8. Quaternary geology

8.1. Ice and climate history in the Arctic and subarctic

8.2. Glacial processes, deposits and landforms

8.3. Open session Quarternary geology

8.1. Ice and climate history in the Arctic and subarctic

                       ORAL PRESENTATIONS                    

A 200 ka glaciation history from NW Svalbard

Helena Alexanderson¹, Mona Henriksen², Heidi T. Ryen³, Jon Y. Landvik² and Gustaf Peterson^4
1Lund University, ²Norwegian University of Life Sciences, ³Norwegian Water Resources and Energy Directorate, ⁴Geological Survey of Sweden
Late Quaternary sedimentary units at Kongsfjordhallet, NW Svalbard, represent five cycles of glaciations and subsequent deglaciations during high relative sea levels. The high sea-level events are interpreted as glacioisostatically induced and imply preceding regional glaciations, which we constrain in time by luminescence and radiocarbon ages to just prior to ~195 ka, ~130 ka, ~85 ka, ~60 ka and ~14 ka. Combined with the stratigraphical record from nearby Leinstranda (Alexanderson et al. 2011) we identify six, possibly seven, major glacial advances during the last 200 ka in the Kongsfjorden region. Two of these occurred during the Saalian and at least four during the Weichselian.

The results are based on detailed sedimentological, stratigraphical and chronological investigations of the uppermost 15 m of the 40-m-high Kongsfjordhallet coastal sections. The succession is dominated by sediments of marine and littoral origin, representing partial shallowing-upward sequences due to isostatic rebound. Only one subglacial till was recognized. Interestingly, alluvial and periglacial deposits, not commonly recognized in this type of setting, occur in the sequence. These include weathered coarse alluvium, sandy channel fills as well as cryoturbated sediments and solifluction deposits. The sedimentary succession has been summarised in a facies model for an emergence cycle following deglaciation.

Our study encompasses only the upper 15 m of the coastal cliff sections at Kongsfjordhallet (succession A of Houmark-Nielsen and Funder 1999), and there is an additional ~20 m of sediments below our Unit 1, which is promising for future studies aiming to go further back in time.

References

Alexanderson, H., Landvik, J. Y. and Ryen, H. T. 2011. Chronology and styles of glaciation in an inter-fjord setting, northwestern Svalbard. Boreas 40, 175-197.

Houmark-Nielsen, M. and Funder, S. 1999. Pleistocene stratigraphy of Kongsfjordhallet, Spitsbergen, Svalbard. Polar Research 18, 39-49.

Reindeer kill dates record late Holocene glacier lake outburst floods in East Greenland

Anders Bjørk¹, Morten Meldgaard¹, Jeppe Møhl¹, Kristian Gregersen¹, Shfaqat Khan², Romain Millan³, Kristian Kjeldsen², Svend Funder¹, Mike Willis⁴, Laurence Dyke⁵, Nicolaj Larsen⁶ and Kurt Kjær^1
1Natural History Museum of Denmark, ²DTU Space, ³University of California, Irvine, ⁴University of Colorado, Boulder, ⁵GEUS, ⁶Aarhus Universitet
In the summers of 2004 and 2005 a surprising find of the remains of several dead reindeers was done in East Greenland. The carcasses were melting out of a snowbank in a small valley next to the village Ittoqqortoormiit at the mouth of Scoresbysund fjord-system. The radio-carbon ages of the 30 animals showed a surprising spread with several episodes of reindeer-deposition within the last four thousand years. We argue that the only phenomena capable of killing and positioning the animals at the exact same location over multiple millennia are glacier lake outburst floods (GLOFs). In the catchment, glaciers and topography capable of creating GLOFs are indeed present. Thus, our pile of dead reindeer became an unlikely proxy of glacial presence, and moved the onset of neo-glacial build-up in the region by a thousand years.

Preliminary results based on 24 new ³⁶Cl exposure datings reveals asynchronous deglacial history of Tröllaskagi peninsula, central north Iceland

Skafti Brynjólfsson¹, Nuria Andrés², David Palacios² and Þorsteinn Sæmundsson^3
1Icelandic Institute of Natural History, Akureyri, Iceland, ²Universidad Complutense, Physical Geography, Madrid, Spain, ³Institute of Life and Environmental Science, Reykjavík, Iceland
At present the Tröllaskagi peninsula, located in central north Iceland hosts 150 cirque and valley glaciers. The landscape is characterised by steep narrow glacially carved valleys separated with up to 1500 m high peaks and ridges. The glacial history of Tröllaskagi suffer from lack of direct dating. Previous studies indicate Tröllaskagi peninsula was mostly ice covered during the last glacial maximum. Several lowland end moraines and raised beaches indicate recurrent glacial re-advances during the deglaciation , which was completed  about 10 Ka ago. Most of the present glaciers are considered to have reached maximum Holocene conditions during the late Little Ice Age.

We sampled 24 rock samples from erratics and moraine boulders for ³⁶Cl exposure dating in order to improve the glacial history of the area. Preliminary results indicate asynchronous deglaciation pattern over the peninsula. Some mountain ridges and summits were deglaciated at least about 16 Ka ago. Furthermore, some highland valleys were deglaciated about 13-14 Ka ago while others probably remained glaciated at least until early Holocene. Finally we obtained average ages 2.66 Ka and 0.7 Ka from two moraines proximal to present glaciers which were suspected to relate to LIA fluctuations.

Our preliminary results support recent researches that suggest ³⁶Cl exposure dating method as plausible to improve significantly the deglacial history of Iceland, especially where presence of tephra and organic material for dating is limited.

Advances in Deglaciation on Svalbard

Wesley R. Farnsworth¹, Ólafur Ingólfsson², Michael Retelle³, Lis Allaart⁴, Lena Håkansson⁵, Anders Schomacker⁶, Riko Noormets⁷, Snorre Olaussen⁸, Alexander Prokop⁸ and Aleksandra Smyrak-Sikora^8
1University Centre in Svalbard (UNIS) & UiT, The Arctic University of Norway, ²University of Iceland & University Centre in Svalbard (UNIS), ³Bates College, ME, USA & University Centre in Svalbard (UNIS), ⁴UiT, The Arctic University of Norway, ⁵University Centre in Svalbard (UNIS), ⁶UiT, The Arctic University of Norway & Natural History Museum of Denmark, ⁷University Centre in Svalbard (UNIS), Dept. of Arctic Geology, N-9171 Longyearbyen, ⁸University Centre in Svalbard (UNIS), Dept. of Arctic Geology, N-9171 Longyearbyen, Norway
Despite warm regional fjords, a variety of data suggest extensive glacier advances on Svalbard during the Pleistocene-Holocene transition. We present the first well-constrained (in age) end moraine formed during the Lateglacial-early Holocene (LGEH) in Svalbard, De Geerbukta, NE Spitsbergen. The landform was deposited by an outlet glacier re-advancing into a fjord extending 4.4 km further than the late Holocene maximum. We compare the synchronicity of this glacier advance to paleoclimate records and 15 other proposed glacier advances from Svalbard. Furthermore, we introduce 35 additional LGEH glacier deposits identified through remote sensing were glaciers also advanced into a high relative sea level. Glacial deposits were wave-washed or cut by early Holocene raised marine shorelines, suggesting the landforms were deposited before or during high relative sea level stands, thus exhibiting a similar LGEH age. Contrary to current understanding, our new evidence suggests that the LGEH glaciers were more dynamic, exhibited re-advances and extended well beyond the extensively studied late Holocene glacial expansion. Given the widespread occurrence of the LGEH deposits on Svalbard, we suggest that the culmination of the Neoglacial advances during the Little Ice Age does not mark the maximum extent of most Svalbard glaciers since deglaciation; it is just the most studied and most visible in the geological record.

¹⁰Be and ²⁶Al exposure and burial histories for ancient granite tors in arctic Finland.

Adrian Hall¹, Marc Caffee², Karin Ebert¹, Jakob Heyman³ and Johan Kleman^1
1Department of Physical Geography, Stockholm University SE 106 91 Stockholm Sweden, ²Purdue Rare Isotope Measurement Laboratory, Purdue University, 525 Northwestern Avenue, West Lafayet, ³Department of Earth Sciences, University of Gothenburg, PO Box 460, SE 405 30 Göteborg Sweden
The ice-divide zone of northern Finland experienced low erosion beneath successive cold-based Fennoscandian ice sheets (Hall et al., 2015). One indicator of this are the many tors that occur on hill tops and flanks. Published ¹⁰Be and ²⁶Al inventories for two tor summit surfaces near Vuotso indicate ~0.8 Myr of exposure and burial (Darmody et al., 2008). These samples came from tabular tors that may have lost granite sheets to glacial erosion. Schmidt Hammer values are high, indicating limited weathering of these rock surfaces despite apparently long exposure. Hence published data may relate to one or more phases of glacial erosion rather than to tor surface erosion. In contrast, nearby tors retain delicate superstructures and give low rock hardness values, features consistent with little or no glacial modification, more advanced weathering and longer exposure of the tor summit surfaces. We will present new ¹⁰Be and ²⁶Al isotope results for these surfaces and use Monte Carlo simulations to derive Pleistocene exposure and burial histories. We expect bedrock erosion rates to be amongst the lowest reported for the northern Fennoscandian shield.

References
Darmody, R.G., Thorn, C.E., Seppala, M., Campbell, S.W., Li, Y.K., Harbor, J., 2008. Age and weathering status of granite tors in Arctic Finland (~ 68˚ N). Geomorphology, 94, 10-23.

Hall, A.M., Sarala, P., Ebert, K., 2015. Late Cenozoic deep weathering patterns on the Fennoscandian shield in northern Finland: a window on ice sheet bed conditions at the onset of Northern Hemisphere glaciation. Geomorphology, 246, 472–488.

Constraining the evolution of the last Eurasian ice sheets: progress towards DATED-2

Anna Hughes¹, Richard Gyllencreutz², Jan Mangerud¹ and John Inge Svendsen^1
1University of Bergen & Bjerknes Centre for Climate Research, ²Stockholm University
In 2016 we published an empirical reconstruction of the evolution of the extent of the last Eurasian ice sheets, that is fully documented, specified in time, and includes uncertainty estimates (DATED-1; Hughes et al. 2016). This was the culmination of a 10-year effort to compile and archive all published dates relating to the build-up and retreat of the British-Irish, Scandinavian and Svalbard-Barents-Kara Seas ice sheets. Over 5000 dates were assessed for reliability and used, together with published geomorphology-based ice-sheet margin positions, to reconstruct time-slice maps of ice extent for every 1000-years 25-10 ka and four periods between 40-27 ka. All uncertainties (both quantitative and qualitative e.g. precision and accuracy of numerical dates, correlation of moraines, stratigraphic interpretations) were combined based on our best glaciological-geological assessment and expressed in terms of distance as a ‘fuzzy’ margin. Since the DATED-1 census (1 January 2013), the volume of new information (from both dates and mapped glacial geomorphology) has grown significantly (e.g. 32% increase in the number of dates), although the spatial distribution of information remains similar. Here, we present work towards an updated version of results, DATED-2 (census: 1 January 2017), that attempts to further reduce and explicitly report all uncertainties inherent in the ice sheet reconstructions, and discuss the implications of the revised margins.

References
Hughes, A. L. C., Gyllencreutz, R., Lohne, Ø. S., Mangerud, J., Svendsen, J. I. 2016: The last Eurasian ice sheets – a chronological database and time-slice reconstruction, DATED-1. Boreas, 45, 1–45. 10.1111/bor.12142

Local ice caps response to Holocene climate variability in Kobbefjord, West Greenland

Nicolaj K. Larsen¹, Astrid Strunk¹, Laura B. Levy², Jesper Olsen³, Anders Bjørk⁴, Torben L Lauridsen⁵, Erik Jeppesen⁵ and Thomas A. Davidson^5
1Department of Geoscience, Aarhus University, ²Department of Geology, Humboldt State University, ³Department of Physics and Astronomy, Aarhus University, ⁴Natural History Museum of Denmark, University of Copenhagen, ⁵Department of Bioscience, Aarhus University
The sensitivity of glaciers and ice caps (GICs) in Greenland to prolonged warm periods is poorly constrained and geological records documenting the long-term glacial history are needed to put recent observations into a broader perspective. Here we report the results from three proglacial lakes where fluctuations in local glaciers located at different altitudes in Kobbefjord, southwest Greenland have been recorded. Our results show that the lakes received meltwater from the initial deglaciation of the area ~9.2 cal. ka BP until ~8.7-7.9 cal. ka BP when the meltwater input ceased as the glaciers most likely disappeared. Regrowth of glaciers began again at ~5.5 cal. ka BP at ~1,370 m a.s.l., ~3.6 cal. ka at ~1,170 m a.s.l., and ~1.6 cal. ka BP at ~1,000 m a.s.l., clearly reflecting strong altitudinal control of the GIC response to Neoglacial cooling. Our results highlight that GICs in Kobbefjord, southwest Greenland are primarily influenced by changes in summer air temperatures and winter precipitation and that they are facing a rapid decay that most likely will result in their disappearance within the next centuries as a consequence of global warming.

Deglaciation patterns of the Lake District Ice Lobe of the Scandinavian Ice Sheet in SE Finland during the Younger Dryas

Juha Lunkka¹, Niko Putkinen² and Anu Seppänen^2
1Geoscience Research Unit, Oulu Mining School. P.O. Box 3000, FI 90014 University of Oulu, Finland, ²Geological Survey of Finland, P.O. Box 97, FI-67101, Kokkola, Finland
The deglaciation pattern of the Lake District Ice Lobe (LDIL) of the former Scandinavian Ice Sheet (SIS) in the Salpausselkä zone, southern Finland were studied. Glaciofluvial landforms (i.e. eskers, glaciofluvial deltas and subaquatic fans and sandurs) were mapped using Digital Elevation Model (DEM) data with 10 metre-resolution and Light Dedection And Ranging (LiDAR) data with 2 metre-resolution. Hillshading was used to make a DEM-generated 3D-landscape in order to help the recognition of landforms and their surface deformation. Based on these observations ice lobe re-advance and retreat phases, and their extent across the Salpausselkä zone were defined.

The results indicate that the LDIL of the SIS retreated as far as 40 kilometres north of the proximal side of the present Second Salpausselkä ridge most likely prior to the Younger Dryas. This retreat phase was followed by a re-advance and the deposition of the First Salpausselkä in front of the LDIL ice margin. Subsequently, ice retreated further north and the Second Salapusselkä in front of the LDIL margin was formed. Optically stimulated luminescence dates indicate that the Second Salpausselkä was deposited during the Younger Dryas.

Molluscs show an early and exceptional warm Holocene Thermal Maximum around Svalbard, which is not found in climate models

Jan Mangerud¹ and John Inge Svendsen^1
1Dept. of Earth Science, Univ. of Bergen, Norway and Bjerknes Center for Climate Research
Several species of shallow-water marine molluscs that cannot presently live around Svalbard due to the cold-climate occur frequently in raised Early Holocene deposits. The most warmth demanding of these species, Zirfaea crispata, currently has a northern limit 1000 km farther south. Based on radiocarbon ages of this species we conclude that the August temperatures on Svalbard were as much as 6 °C warmer than today during the period 10,200 to 9,200 calendar years ago (Mangerud & Svendsen 2017). The blue mussel, Mytilus edulis, re-appeared on Svalbard in 2004, in response to the recent warming of the Arctic. This happened almost 4000 years after Mytilus disappeared from the shores of Svalbard, excluding a short re-appearance during the Medieval Warm Period 900 years ago. After the last Ice age, Mytilus arrived for the first time in Svalbard as early as 11,000 years ago, indicating that the climate was then as least as warm as today.

If we, as an example, postulate that the winter precipitation pattern during the period 10,200 – 9,2000 years ago was similar to the present pattern, then a summer warming of 6 °C would have raised the equilibrium line altitude (ELA) on glaciers by about 900 meters, and all glaciers on Svalbard would have melted away.

We also note that climate models simulate a much later and not-so-warm Thermal Maximum compared with our reconstruction when ice sheets, or ice sheets and meltwater, are included in the models (Zhang et al. 2016).

References
Mangerud, J. & Svendsen, J. I. 2017: The Holocene Thermal Maximum around Svalbard, Arctic North Atlantic; molluscs show early and exceptional warmth. The Holocene. http://journals.sagepub.com/doi/abs/10.1177/0959683617715701

Zhang, Y., Renssen, H. & Seppä, H. 2016: Effects of melting ice sheets and orbital forcing on the early Holocene warming in the extratropical Northern Hemisphere. Climate of the Past 12, 1119-1135.

Local or distant centre of uplift, a case study from Northwest Iceland

Hreggviður Norðdahl^1
1Institute of Earth Sciences, University of Iceland
Contemporary studies of glacio-isostatic uplift at the Vatnajökull glacier in Iceland have revealed a more or less instantaneous accelerating rates of uplift as high as 35 mm·a^-1 due to negative glacier mass-balance. During the late Weichselian deglaciation of Iceland, uplift rates exceeded 160 mm·a^-1 when relative sea-level regressed from the marine limit in West Iceland some 14.7 cal ka BP.

Glacial striae in Northwest Iceland are arranged in an apparent radial pattern with the striae orientated towards the outer coasts of NW-Iceland implying that the striae were formed by actively eroding glaciers retreating towards the centre of the peninsula. Numerical modelling of the Weichselian retreat of the Icelandic Ice Sheet (IIS) has returned local ice-caps in NW Iceland when the IIS reached a temporary minimum in Bølling-Allerød times. Thus, the existence of independent late Weichselian ice-caps in NW Iceland seems plausible and also that they influenced glacio-isostatic uplift in the area, especially when considering temporal and spatial isostatic equilibrium during deglaciation.

Raised shoreline features are found throughout lowland areas of NW Iceland from present sea-level and up to or slightly above 80 m a.s.l. The aim of this paper is to examine if altitudes of raised shorelines can be used to decide if glacio-isostatic uplift of the NW Iceland was controlled by reduced crustal load (uplift) of a local ice cap or if, and then to what extent, the uplift was influenced by the wastage of the IIS in central Iceland.

Younger Dryas ice margin retreat triggered by warming of the ocean surface in central-eastern Baffin Bay

Mimmi Oksman¹, Kaarina Weckström², Arto Miettinen³, Stephen Juggins⁴, Dmitry Divine³, Rebecca Jackson⁵, Richard Telford⁶, Niels J. Korsgaard⁷ and Michal Kucera^5
1Department of Geosciences and Geography, University of Helsinki, Finland, ²Department of Environmental Sciences (ECRU), University of Helsinki, Finland, ³Norwegian Polar Institute, Norway, ⁴School of Geography, Politics and Sociology, Newcastle University, UK, ⁵MARUM – Center for Marine Environmental Sciences, University of Bremen, Germany, ⁶Department of Biology, University of Bergen, Norway, ⁷Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, Iceland
The Greenland Ice Sheet stability is linked to fast-flowing ice streams that are strongly influenced by sea surface temperatures (SSTs) at their front (Holland et al. 2008; Nick et al. 2013). As the ice mass loss from the Greenland Ice Sheet is accelerating (Shepherd et al. 2012), there is a need for high-resolution marine proxy data to understand interactions between the ocean and the ice sheet. Here we present the first diatom-based high-resolution quantitative reconstruction of sea surface conditions from central-eastern Baffin Bay covering the period from 14.0 to 10.2 kyr BP. Our reconstruction reveals warmer sea surface conditions from 13.4 kyr BP to the end of the Younger Dryas (YD) period (11.7 kyr BP) and strong interaction between the ocean and the West Greenland ice margin. These warmer ocean conditions were caused by an enhancement of Atlantic-sourced water inflow together with increased insolation and amplified seasonality. Our sediment record shows that warmer ocean conditions played key part in the retreat of Jakobshavn Isbræ, one of the largest ice streams in West Greenland, which has been shown to have collapsed at 12.2 kyr BP (Rinterknecht et al. 2014). Our results show that ice retreat occurred mainly by calving during the YD period while surface/subsurface melt dominated during a warmer climate before and after the YD. Our results emphasize the ocean`s significant role for ice sheet stability under the current climate change.

References
Holland, D. M., Thomas, R. H., De Young, B., Ribergaard, M.H. & Lyberth, B. 2008: Acceleration of Jakobshavn Isbræ triggered by warm subsurface ocean waters. Nature Geoscience 1, 659−664.

Nick, F.M., Vieli, A., Andersen, M. L., Joughin, I., Payne, A., Edwards, T. L., Pattyn, F. & van de Wal, R. S. W. 2013: Future sea-level rise from Greenland´s main outlet glaciers in a warming climate. Nature 497, 235−238.

Rinterknecht, V., Jomelli, V., Brunstein, D., Favier, V., Masson-Delmotte, V., Bourlès, D., Leanni, L. & Schläppy, R. 2014: Unstable ice stream in Greenland during the Younger Dryas cold event. Geology 42, 759−762.

Shepherd, A. et al. 2012: A reconciled Estimate of Ice-Sheet Mass Balance. Science 338, 1183−1189.

Marine environmental changes in front of the Scandinavian Ice Sheet during the last deglaciation

Nadine Quintana Krupinski¹, Andreas Mackensen², Yasmin Bokhari Friberg¹, Karen-Luise Knudsen³, Anne-Sophie Fanget³, Jeroen Groeneveld⁴, Ellen Martin⁵, Marit-Solveig Seidenkrantz³ and Helena Filipsson^1
1Lund University, ²Alfred Wegener Institute, ³Aarhus University, ⁴MARUM, University of Bremen, ⁵University of Florida
The Kattegat-Baltic Sea region shows evidence of strong coupling with North Atlantic climate over recent glacial-interglacial cycles, but insufficient long, high-resolution Baltic area climate records have limited evaluating such links. New ultra-high-resolution sediment cores collected during IODP Expedition 347 can provide such records, including foraminiferal and mollusc geochemistry records reflecting seawater environmental changes directly adjacent to the Scandinavian Ice Sheet (SIS) during the most recent deglaciation.

We present benthic foraminiferal stable isotope (δ¹⁸O and d¹³C) and trace element (Ba/Ca, Mn/Ca and Mg/Ca) records as well as mollusc Sr isotope data from IODP Site M0060 (located between Sweden and Denmark in the southern Kattegat) to constrain bottom water salinity, temperature and oxygenation changes from ~18-13ka. Because of the large salinity changes (fresh to marine) during the past 20ka in this region, we interpret δ¹⁸O as reflecting salinity changes more than temperature here, while d¹³C reflects ventilation, productivity, and salinity. Ba/Ca, Mn/Ca, and Mg/Ca may indicate salinity, oxygenation, and temperature variations, although these proxies are less straightforward to interpret in this setting.

Stable isotope results suggest fjord-like, poorly ventilated conditions during early deglaciation, with three clear phases: 1) an initial rapid, large freshening event; 2) subsequent slower, step-wise freshening (likely linked to the decay of the SIS); 3) more marine, ventilated, saline conditions after ~15.6ka. These events may be linked to regional and global climate changes during this period of global climate changes, and may help us evaluate the interplay between the SIS and climate in the North Atlantic and beyond.

New insights into the glacial and climate history of the Polar Urals, Arctic Russia

Carl Regnéll¹, John-Inge Svendsen¹, Haflidi Haflidason¹ and Jan Mangerud^1
1Department of Earth Science and Bjerknes Centre for Climate Research, University of Bergen, Norway
Here we present new results and discoveries from several field campaigns in the Polar Urals of Arctic Russia. This talk focus on the late Weichselian and Holocene glacial and climate history as inferred from a 24 m long, partly varved, high resolution and exceptionally well dated sediment core from a deep lake (Bolshoye Schuchye) located in the interior of the mountain chain. The core, that is spanning the last 24,000 years, provide a unique high resolution record of the climate and environmental changes since the Last Glacial Maximum (LGM). Our results infer glacial influence on lake sedimentation including annual rhythmites, i.e. varves, through the LGM until about 19 ka when the continuous sequence of varves successively disappear and the sedimentation rate decrease. We conclude that all local glaciers within the catchment had melted away by 15 ka and there are no indications that a regrowth of glaciers took place during the Younger Dryas. A significant warmer climate prevailed during the Holocene period. The combination of AMS ¹⁴C- and varve chronology in this study has provided a valuable contribution to constrain the age model for ongoing palynological-, paleomagnetic, DNA- and compound specific isotope (δ²H, δ¹⁸O) analyses also conducted within the framework of the CHASE- (Climate History of the Arctic Seaboard of Eurasia) project. Put together, this continuous and unprecedented high resolution record effectively supplement previous attempts to reconstruct pre-Holocene environmental changes based on fragmentary data from moraines and exposed strata along river banks and coastal cliffs around the Russian Arctic.

Relative sea-level data as a constraint of Holocene ice sheet history in Finderup Land, NE Greenland

Astrid Strunk¹, Andreas Nilsson², Marit-Solveig Seidenkrantz¹, Benoir Lecavalier³, Glenn Milne⁴ and Nicolaj K. Larsen^1
1Department of Geoscience, Aarhus University, Denmark, ²Department of Geology, Lund University, Sweden, ³Department of Physics and Physical Oceanography, Memorial University, St. John’s, Canada, ⁴Department of Earth and Environmental Sciences, University of Ottawa, Canada
Here, we present a new relative sea level (RSL) reconstruction for Finderup Land, NE Greenland, based on isolation basins to obtain more knowledge about the Lateglacial and Holocene glaciation history. Existing RSL data is in general sparse in NE Greenland and the RSL curves produced at nearby locations are based on very limited data^1,2. It is imperative to understand how the large ice sheets responded to a warming climate in the past, in order to make accurate predictions of future sea level change. Reconstructions of past relative sea level changes is a key parameter in modeling global sea level fluctuations under past climate changes^1,3,4,5.

We present a new dataset of isolation lakes covering elevations from 8-62 m a.s.l. in which we identify the marine to lacustrine environmental transition. We date this transition using radiocarbon ages from foraminifera combined with paleomagnetic age correlation. Our new dataset will allow us to construct a RSL curve for Finderup Land, which in turn reflects the Lateglacial and Holocene ice marginal fluctuations in NE Greenland. Furthermore, we compare our results with existing predictions of past RSL in the area produced by the Huy2 (ref. 6) and Huy3 (ref. 1) ice sheet models and discuss possible improvements of the ice sheet models by incorporating our new data set.

References

1. Lecavalier, B. S. et al. A model of Greenland ice sheet deglaciation constrained by observations of relative sea level and ice extent. Sci. Rev. 102, 54–84 (2014).
2. Funder, S. et al. A 10,000-Year Record of Arctic Ocean Sea-Ice Variability—View from the Beach. Science (80-. ). 333, 747–751 (2011).
3. Khan, S. A. et al. Geodetic measurements reveal similarities between post-Last Glacial Maximum and present-day mass loss from the Greenland ice sheet. Adv. 2, e1600931, 11pp (2016).
4. Church, J. A. et al. in Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (eds. Stocker, T. F. et al.) 1137–1216 (Cambridge University Press, UK, 2013).
5. Long, A. J., Woodroffe, S. A., Roberts, D. H. & Dawson, S. Isolation basins, sea-level changes and the Holocene history of the Greenland Ice Sheet. Sci. Rev. 30, 3748–3768 (2011).
6. Simpson, M. J. R., Milne, G. A., Huybrechts, P. & Long, A. J. Calibrating a glaciological model of the Greenland ice sheet from the Last Glacial Maximum to present-day using field observations of relative sea level and ice extent. Sci. Rev. 28, 1631–1657 (2009).

Deglaciation history of western Norway inferred from ¹⁰Be- dating of erratics and ¹⁴C-dates from sediment cores

John Inge Svendsen¹, Jan Mangerud¹ and Jason P. Briner^2
1Dept. of Earth Science, University of Bergen and Bjerknes Centre for Climate Research, ²Dept.of Geology, University at Buffalo, USA
We report new results from an ongoing field campaign in southern Norway aiming at reconstructing the glacial and climate history since the Last Glacial Maximum (LGM). The inferred ice sheet history is based on a large number of cosmogenic nuclide exposure ages (¹⁰Be) from glacially transported boulders as well as sediment records from lake basins. We find that all coastal mountains in the studied area were ice covered during the LGM, at which time the Scandinavian Ice Sheet was flowing westward, independent of the underlying topography. Later, the fast flow of the Norwegian Channel Ice Stream led to a lowering of the ice surface. The highest mountain peaks along the Hardangerfjorden became ice free as early as ~20 ka. Following the collapse of the Norwegian Channel Ice Stream, the ice margin stabilized just outside the outermost coast. A major withdrawal took place ~15 ka, possibly in response to the Bølling warming (Gump et al. 2017, Mangerud et al. 2017). The retreat was later interrupted by two re-advances that culminated ~14 ka (Older Dryas) and during the end of Younger Dryas. We find ¹⁰Be- dating a very useful tool for making three-dimensional ice sheet reconstructions. The front of the ice sheet seems to have been surprisingly steep. In the Bergen area the ice surface appears to have reached an elevation of more than 700 m only some 15 km inside the front. However, in low-lying areas radiocarbon dating of basal lacustrine sediments provides more precise and accurate dates of the deglaciation.

References

Gump, D.J., Briner, J.P., Mangerud, J., Svendsen, J.I. 2017: The deglaciation of Boknafjorden, Southwestern Norway. Journal of Quaternary Science  32, 80-90.

Mangerud, J., Briner, J-P. Goslar, T., Svendsen, J.I. 2017: The Bølling-age Blomvåg Beds, western Norway; implications for the Older Dryas glacial readvance and the age of deglaciation. Boreas 46, 162-184.

The Mineral Assemblage of Gas-charged sediments from Vestnesa Ridge, NW Svalbard  – a tale of crystallization and dissolution

Christoph Vogt¹, Simone Sauer², Aivo Lepland³ and Jochen Knies^4
1Crystallography, Geosciences, University of Bremen, Germany, ²CAGE – Centre for Arctic Gas Hydrate/UiT Tromsø & The Geological Survey of Norway, Trondheim, Norway, ³CAGE/ UiT Tromsø & The Geological Survey of Norway, Trondheim, Norway & Uni Tallinn, Lettland, ⁴CAGE/ UiT-Tromsø & The Geological Survey of Norway, Trondheim, Norway
We present a full-pattern quantitative phase analysis of x-ray diffraction data (QXRD, Vogt et al., 2002) from sediments taken within the active methane seep sites of Vestnesa Ridge, NW Svalbard.  . The 4 coring positions were controlled by remotely operating vehicle (ÆGIR 6000) with three sites within the active seep sites and one reference site outside the main activity. Hence, a clear differentiation between active and inactive with respect to methane gas flux  can be shown. While the reference core can be related to well know sedimentary events in the vicinity of the W Spitsbergen shelf and Yermak Plateau – which are related to warm Atlantic water influx and/or deglaciation of the Svalbard ice sheets – gas-hydrate influenced cores contain particular carbonate mineral phases. Mg-rich calcites and aragonites have been freshly precipitated in the vicinity of a sulfide methane transition zone (SMTZ) triggered by anaerobic methane oxidation (AOM) and sulfate reduction due to high methane flux through the sediments .

The QXRD allows also for the investigation of Fe-, Mn-oxides and –sulfides probably precipitated in the transition zones under changing redox-conditions. Combined with sediment and pore water geochemistry, the authigenic mineral assemblage indicative for a gas-hydrate influenced sediment can be described in much detail. While geochemical processes can be quantitatively viewed, the high resolution determination of authigenic minerals also helps to understand the past history of methane emissions in this Arctic gas hydrate system. .

References
Vogt, C., Lauterjung, J. & Fischer, R.X., 2002. Investigation of the clay fraction (<2 µm) of the clay mineral society reference clays. Clays and Clay Minerals, 50(3): 388-400.

                       POSTER PRESENTATIONS                    

From fjord to land – Holocene climate of the Femmilsjøen area, NE Spitsbergen

Lis Allaart¹, Anders Schomacker², Matthias Forwick³, Michael Retelle⁴ and Lena Håkansson^5
1UiT The Arctic University of Norway & University Centre in Svalbard, ²UiT The Arctic University of Norway & Natural History Museum of Denmark, ³UiT The Arctic University of Norway, ⁴Bates College, ME, USA & University Centre in Svalbard, ⁵University Centre in Svalbard
The overall aim of the project is to reconstruct the Holocene climate and glacial history of northeast Spitsbergen, based on a holistic approach including collection and integration of marine, terrestrial and lacustrine data. The area of main interest is the 8 km long lake Femmilsjøen in NE Spitsbergen, as well as its surroundings and the adjacent part of northern Wijdefjorden. Marine sediment cores and swath bathymetry data were collected just off Femmilsjøen in the summer of 2017. Lacustrine cores are to be collected in 2018.  We expect that data series from different archives with restricted spatial distribution will reflect the various feedback mechanisms (e.g. the interaction between ocean-atmosphere, atmosphere-sea-ice, precipitation-ice-masses, increased runoff from glaciers and solar forcing) of the different elements in the climate system in that particular area. This will help to solve questions as whether the Late Pleistocene-Early Holocene fjord temperatures increased first and subsequently the glaciers on land retreated – or vice versa. Furthermore, we aim to identify if the same climatic signals occur in both archives synchronously. Preliminary results from the project will be presented.

Sea-ice in the Iceland-Norwegian Sea during the last 50-60000 years: first results from the IS-4C marine core

Erna Ósk Arnardóttir¹, Esther Ruth Guðmundsdóttir¹, Jón Eiríksson¹, Ívar Örn Benediktsson¹ and Yanguang Liu^2
1Institute of Earth Sciences, University of Iceland, Askja, Sturlugata 7, IS-101 Reykjavík, Iceland, ²First Institute of Oceanography (FIO), State Oceanic Administration, Qingdao, China
Sea ice coverage in the North Atlantic plays an important role in the Arctic climate system.

The aim of the study presented here is to reconstruct and time sea ice coverage in the Iceland-Norwegian sea during the Weichselian with the purpose of increasing our understanding of climate and oceanographic changes. The area is highly affected by the cold southward flowing East Greenland current and a branch of the warmer north-westward flowing Norwegian current, creating a complex zone of temperate and cold waters.

A 430 cm long marine sediment core, IS-4C, retrieved from 1598 m water depth in the Iceland-Norwegian sea, northeast of Iceland has been investigated with regard to quantity and source of ice rafted debris (IRD) as well as the abundance of planktonic foraminifera. These proxies have been counted at every 2-3 cm throughout the core. Radiocarbon dating indicate that the upper 251 cm of the core represent the last 42000 years and the Vedde Ash is present in the uppermost 30 cm. More precise chronology with radiocarbon dating, tephrochronology and correlation of oxygen isotopic records from Greenland ice cores and the North Atlantic deep sea is in progress.

IRD has been identified to three main components; crystals, rock fragments and ash/tephra. Planktonic foraminifera have been counted and identified to species. These proxies display high amplitude variations throughout the core indicating variable sea ice flux. A low sea ice flux is recorded between 184 cm (39500 yr. BP) and 294 cm indicating an interglacial period.  The investigation is ongoing.

A new relative sea level curve from Mestersvig, NE Greenland based on isolation basins

Frank Bauer¹, Astrid Strunk¹, Sarah Woodroffe², Anne Sophie Søndergaard¹ and Nicolaj K. Larsen^1
1Department of Geoscience, Aarhus University, Høegh Guldbergs Gade 2, 8000 Aarhus C, Denmark, ²Environmental Research Centre, Department of Geography, University of Durham, South Road, Durham, UK
Our ability to model the past response of the Greenland ice sheet to climate change is fundamentally dependent on the quality and distribution of geological observations of ice margin history and relative sea level (RSL) observations. In Greenland, the extensive ice-free corridor provides an excellent opportunity to develop a network of well constrained RSL observations that can provide powerful glacio-isostatic adjustment (GIA) constraints over the post-glacial period. In southern Greenland, the RSL observations are in many places well constrained in contrast to northern Greenland where the data quality and spatial resolution is poorer. In this study, we present a new RSL curve from Mestersvig, Northeast Greenland. We used sediment cores from seven isolation basins collected at different elevations to identify the change from marine to lacustrine sediments using a multiproxy approach including XRF core scanning, magnetic susceptibility and diatom analysis. The marine-lacustrine isolations were dated using terrestrial macro fossils. Our new results will be compared to existing RSL curves from the area and with the latest RSL-based ice sheet model of Greenland.

Putorana ice sheet advance over southern Taimyr, NW Siberia, during the Late Saalian (MIS 6)

Ivar Benediktsson¹ and Per Möller^2
1Institute of Earth Sciences, University of Iceland, ²Department of Geology, Lund University
Previous studies in NW Arctic Siberia suggest that local ice caps around the Kara Sea shelf merged there repeatedly to form a Kara Sea Ice Sheet (KSIS). When assembled to a large ice sheet, initial northward flow from the Byrranga Mountains on the Taimyr Peninsula reversed as the ice sheet further expanded southwards. The most extensive glaciation over Taimyr occurred during the Taz/Late Saalian (MIS 6), during which the KSIS advanced from NW onto the Putorana Plateau south of Taimyr. However, stratigraphic sites along the Bol’shaya Balaknya River (situated on southern Taimyr) suggest that the Taz/Late Saalian expansion of the KSIS from NW was preceded by ice coming from the Putorana Plateau to the south, a conclusion based on our site BBR 16. This site reveals a fining upwards sequence from fluvial sands to shallow glaciomarine mud with shell fragments, dated with ESR to 171 ka BP. This sequence is glaciotectonically deformed and unconformably overlain by subglacial traction till. The glaciotectonic deformation as well as clast fabrics in the overlying till, indicate stress application from southerly directions. Our preliminary model suggests a marine transgression due to a growing Putorana ice sheet, before it overrode southern Taimyr during the Late Saalian (MIS 6). This occurred at the same time as a KSIS advanced from the north beyond the Byrranga Mountains. The KSIS subsequently merged with the Putorana ice sheet and eventually pushed the maximum extent of Late Saalian ice well south of the Putorana Plateau.

Facies model for a rebound cycle based on mid-late Quaternary sediments in the Kongsfjorden area, NW Svalbard

Mona Henriksen¹, Helena Alexanderson², Heidi T. Ryen³, Jon Y. Landvik¹ and Gustaf Peterson^4
1Norwegian University of Life Sciences, ²Lund University, ³Norwegian Water Resources and Energy Directorate, ⁴Geological Survey of Sweden
Raised marine deposits found in coastal areas of the Arctic have been instrumental in reconstructing past sea-level change and glaciations during the Quaternary. This is because the high relative sea level indicated by the marine sediments is largely due to isostatic loading and thus implies a preceding regional (ice-sheet scale) glaciation. Kongsfjordhallet is one of several sites in the Kongsfjorden area in NW Svalbard with such deposits, and where successions of Quaternary sediments are exposed in up to 40 m high coastal cliffs (Houmark-Nielsen & Funder 1999). Here, we present results from a more detailed sedimentological and stratigraphical investigation of the uppermost 15 m of Kongsfjordhallet. While subglacial tills are scarce, marine and littoral sediments are volumetrically dominating, representing partial shallowing-upward sequences. Interestingly, we also find alluvial and periglacial deposits, which are not commonly recognized in this type of settings.

Based on this record we have further developed the facies model for rebound cycle by Alexanderson et al. (2011). An idealized record, representing glacial advance and overriding (facies A), deglaciation with isostatic rebound and successively shallower water (facies B-E) and eventually fluvial and periglacial processes (facies F) on ice-free land. Even if only a few of the facies are actually found per sequence, it still implies a regional glaciation. At Kongsfjordhallet, five cycles of glaciation and subsequent deglaciation during high but falling relative sea levels are recognized. These are dated by luminescence to range in age from ~190 ka to the last deglaciation (Alexanderson et al., this volume).

References
Alexanderson, H., Landvik, J.Y. & Ryen, H.T. 2011. Chronology and styles of glaciation in an inter-fjord setting, northwestern Svalbard. Boreas 40, 175-197.

Alexanderson, H., Henriksen, M., Ryen, H.T., Landvik, J.Y. & Peterson, G. this volume: A 200 ka glaciation history from NW Svalbard.

Houmark-Nielsen, M. & Funder, S. 1999: Pleistocene stratigraphy of Kongsfjordhallet, Spitsbergen, Svalbard. Polar Research 18, 39-49.

The Weichselian chronostratigraphical framework of the Kongsfjorden Trough Mouth Fan, W-Spitsbergen

Daniel Hesjedal Wiberg¹, Haflidi Haflidason² and Jan Sverre Laberg^1
1Department of Geosciences, UiT – The Arctic University of Norway in Tromsø, N-9037 Tromsø, Norway., ²Department of Earth Science, University of Bergen, Bergen, Norway
The high-latitude Kongsfjorden Trough-Mouth Fan (TMF), situated on the continental margin west of Svalbard was fed by the Kongsfjorden paleo-ice stream system. A placement, which is ideally suited for recording glacial advances to the shelf break and thereby the development of the Svalbard Ice Sheet through time. During a survey in 2010, a regional seismic grid was established, consisting of 17 high-resolution seismic 2D lines (TOPAS). There were also retrieved a 12.65 meter long sediment core from the southern part of the Kongsfjorden TMF at 846 m water depth. Our preliminary conclusion fits well with the earlier proposed development models, which indicates that during the Weichselian glacial (117 – 11.6 ka), paleo-ice streams from the west coast of Spitsbergen advanced to the continental shelf-break three times. The new data acquired allow us to study the last two advances in greater detail than previously available. The upper half of the core displays a very varied character, with layers comprising ice rafted debris (IRD) inter-bedded with hemipelagic sediments, where the interval between 2 – 5 m have been dated with AMS ¹⁴C. An anomalous layer (at 270-335 cm) have been estimated to have an age between 23,3 – 25 ka, and is interpreted to comprise sediments from the last glacial maximum (LGM). The lower half of the core appears visually fairly homogenous, but have been interpreted to consist of alternating layers of GDFs and IRD related to the second advance during the mid-Weichselian, estimated to have occurred from about 70 ka.

Evolution of Greenland’s glaciers and ice caps in the 20th century

Niels J. Korsgaard¹ and Miska Luoto^1
1University of Helsinki, Department of Geosciences and Geography
About 20,000 glaciers and ice caps (GICs) surround the Greenland Ice Sheet. These GICs cover 7% of the glaciated area in Greenland but store less than 1% of the total ice volume. It is estimated that 14-20% of the total ice loss from Greenland between 2003-2008 could be attributed to the GICs, therefore they contribute far more to global mean sea level rise than their size relative to the Greenland Ice Sheet would suggest. They could make a significant contribution in the 21st century, as they are more sensitive climate indicators and adjust their size in response to climate change more rapidly than ice sheets. Estimates for the 20^th century that predates the modern age of remote sensing, use records from half a score of GICs to obtain estimates of the mass loss for Greenland as a whole. This has implications for our understanding of past glacier evolution and its coupling to climate, and hence also limits our ability to predict the future. This project aims to produce an improved observational data set for physical and statistical modelling of ice loss with regional granularity. The record will extend back to the Little Ice age, when the GICs began to retreat from their maximum positions. Data and models will be developed to facilitate an analysis of factors driving GIC evolution in the 20^th. Finally, the data will be used as input for inversion modelling of glacier evolution of a subset of ice caps enabling a forward simulation of future behavior.

Paleoceanographic ocean surface conditions in Kongsfjorden, Svalbard over the last 400 years

Tiia Luostarinen¹, Arto Miettinen², Katrine Husum², Dmitry Divine², Seija Kultti¹, Outi Hyttinen³ and Rahul Mohan^4
1Department of Geosciences and Geography, University of Helsinki, ²Norwegian Polar Institute, Tromsø, Norway, ³Department of Geosciences and Geography, University of Helsinki; Geological Survey of Finland, Espoo, ⁴National Centre for Antarctic and Ocean Research, Ministry of Earth Sciences, Goa, India
Marine subfossil diatom assemblages from Kongsfjorden are used to investigate sea surface temperatures (SST) and sea ice variability in high temporal resolution. The oceanographic conditions in Kongsfjorden are strongly related to the characteristics of the West Spitsbergen Current (WSC), transporting Atlantic Water (AW) and therefore heat and salt into the Arctic Ocean (Svendsen et al., 2002). Changes in the AW inflow can have a major impact on the environment of the Svalbard area (Ślubowska-Woldingen et al. 2007).

A 49 cm long marine sediment core was analyzed for diatoms and grainsize at 1.0 cm intervals. Diatoms were abundant in the top 16 cm. The AMS 14C dates suggest the basal age of ca. 400 cal yr. BP. The diatom-based SST reconstruction based on the North Atlantic surface sediment sample calibration data set (Miettinen et al. 2015) and WAPLS transfer function method (Ter Braak and Juggins 1993) indicates temperature variation between 4.1 to 6.0 ˚C with a mean temperature of 4.8 ˚C. The qualitative sea ice reconstruction is based on the Marginal Ice Zone (MIZ) diatom assemblage. Factor analysis with the North Atlantic diatom factors based on Andersen et al. 2004 was used to estimate the variability of water masses. The preliminary results show a cooling trend in both SST and sea ice since the Little Ice Age, and a very recent warming during the past decades. Grain size is dominated by fine fraction, but in the upper 15 cm coarse fraction increases up to 40 %, indicating change in depositional conditions.

References
Andersen, C., Koç, N., Jennings, A. and Andrews, J.T. 2004: Nonuniform response of the major surface currents in the Nordic Seas to insolation forcing: Implications of the Holocene climate variability. Paleoceanography 19, PA2003.

Miettinen, A., Divine, D., Husum, K., Koç, N. and Jennings, A., 2015: Exceptional ocean surface conditions on the SE Greenland shelf during the Medieval Climate Anomaly. Paleoceanography 30, 1675–1674.

Ślubowska-Woldingen M., Rasmussen, T.L., Koç, N., Klitgaard-Kristensen D., Nilsen, F. and Solheim, A. 2007: Advection of Atlantic Water to the western and northern Svalbard shelf since 17,500 cal yr BP. Quarternary Science Reviews 26, 463–478.

Svendsen, H., Beszczynska-Møller, A., Hagen, J.O., Lefauconnier, B., Tverberg, V., Gerland, S., Ørbæk, J.B., Bischof, K., Papucci, C., Zajaczkowski, M., Azzolini, R., Bruland, O., Wiencke, C., Winther, J-G. and Dallmann, W. 2002: The physical environment of Kongsfjorden-Krossfjorden, an Arctic fjord system in Svalbard. Polar Research 21(1), 133­–166.

Ter-Braak, C. J. F., and Juggins, S. 1993: Weighted averaging partial least squares regression (WA-PLS): An improved method for reconstructing environmental variables from species assemblages, Hydrobiologia, 269(1), 485–502.

Characteristics of wave-built sedimentary archives in Buor Khaya Bay (71°N/130°E), Siberian Arctic, Russia.

Lasse Sander¹, Rune Michaelis¹, Svenja Papenmeier¹, Sergey Pravkin² and Karen H. Wiltshire^1
1Alfred-Wegener-Institute, List/Sylt, Germany, ²Arctic and Antarctic Research Institute (AARI), St. Petersburg, Russia
Prograded sequences of beach deposits preserve valuable paleoenvironmental information on the long-term variability of the (wave-) climate forcing driving centennial to millennial coastal evolution. Buor Khaya Bay, NE Siberian Arctic, is located at the transition between the Verkhoyansk mountain range and the Arctic Ocean and is one of the few places along the Russian arctic coast, where wide beach-ridge systems exist. Two field sites in Buor Khaya Bay were visited during an expedition in August 2017 in order to obtain baseline information to assess the potential of the systems for the reconstruction of Holocene sea level and past sea-ice extent. The inner parts of the bay are ice-free for three to four months during the short boreal summer. The wave forcing of the system is hence a function of the duration of ice-free conditions and fetch across the open sea surface. Both systems are composed of several sets of beach ridges composed of sand- to cobble-sized shales of local origin. The morphological arrangement of landforms and the characteristics of the beach deposits evidence (1) extensive periods of continuous progradation, and (2) unconformities with changes in ridge orientation suggesting fluctuations in the directional components of energy supply and sediment delivery.

The project is at an early stage of investigation and we present first insights into a new and promising area of investigation. Work will be continued in summer 2018.

Ice marginal fluctuations of local ice caps in McCormick Fjord, NW Greenland

Anne Sofie Søndergaard¹, Nicolaj Krog Larsen¹, Astrid Strunk¹ and Jesper Olsen^2
1Dept. for Geoscience, Aarhus University, Denmark, ²Dept. for Physics and Astronomy, Aarhus University, Denmark
Knowledge about the glacial history of the Greenland Ice Sheet and its dynamic response to past climate variability is important to put the current changes into context. In southern and eastern Greenland, a number of recent studies have documented the ice marginal response to Holocene climate variability (Lowell et al. 2013, Larsen et al. 2016), but from northern Greenland there are very few observations.

In this study, we use a multiproxy approach to try and constrain the Holocene glacial history in McCormick Fjord in northwest Greenland. Due to the occurrence of moraines and the absence of marine content in several retrieved lake cores, we speculate that the area might has been subjected to an early Holocene ice advance that dammed the area from the inflow of marine waters from the fjord.

During the field season 2016 and 2017 we retrieved sediment cores from 5 lakes in different elevations, samples for cosmogenic exposure dating from two moraines, shell fragments and mosses from the margin of a nearby local ice cap. Here we present C¹⁴ ages and XRF data of 6 sediment cores and C¹⁴ dates of moss samples – the rest of the samples are scheduled to be processed in early spring 2018.

With the collected data, we expect to obtain an overview of the deglaciation history in McCormick Fjord. We will discuss the ages and data in relation to existing climate records from the area and put the new results into context.

References
Lowell, Thomas V; Hall, Brenda L; Kelly, Meredith A; Bennike, Ole; Lusas, Amanda R; Honsaker, William; Smith, Colby A; Levy, Laura B; Travis, Scott; Denton, George H, (2013), Late Holocene expansion of Istorvet ice cap, Liverpool Land, east Greenland, Quaternary Science Reviews, Volume 63, Page 128 – 140

Larsen, Nicolaj K; Find, Jesper; Kristensen, Anders; Bjørk, Anders A; Kjeldsen, Kristian K; Odgaard, Bent V; Olsen, Jesper; Kjær, Kurt H, (2016), Holocene ice marginal fluctuations of the Qassimiut lobe in South Greenland, Scientific reports, Volume 6, Article 22362

8.2. Glacial processes, deposits and landforms

                       ORAL PRESENTATIONS                    

Palaeo-ice streams in NE-Iceland: a new project and the first findings

Ívar Benediktsson¹ and Ólafur Ingólfsson^1
1Institute of Earth Sciences, University of Iceland
Current understanding of the configuration, geomorphological imprint, dynamics and recessional history of palaeo-ice streams in Iceland is limited. A new project aims to advance our knowledge of palaeo-ice streams in NE Iceland by investigating the glacial landform associations and sedimentary records in the Vopnafjörður, Bakkaflói, Þistilfjörður and Jökuldalsheiði areas, using multiple glacial geological, geomorphological, remote sensing, geophysical/geotechnical and chronological methods. The project is designed to elucidate the relative timing and spatial distribution of fast ice flow, the absolute timing of ice-stream/ice-sheet recession and thinning, and the mechanisms contributing to fast flow and the genesis of streamlined subglacial bedforms. The project can thereby provide insight into marine-ice sheet instability and the vulnerability of marine-terminating ice streams to sea-level rise, and further our understanding of ice sheet deglaciation dynamics. An important benefit of this project will be the value of its results for constraining numerical models aimed at illuminating subglacial landform development and the evolution of the Iceland ice sheet during the last deglaciation.

Preliminary mapping suggests that the flow sets of several apparently cross-cutting former ice streams are preserved in the glacial landform record. This includes onset zones with reticulated ridges and hummocky topography, and trunk-flow zones with elongate subglacial bedforms, rhombohedral ridge-networks and regularly-spaced transverse ridges. Reconnaissance fieldwork in 2017 indicates that elongate sedimentary bedforms consist of deformation till and sorted sediments, and that rhombohedral and transverse ridges are mainly composed of till. Future excavations and GPR surveys aim at revealing the internal structure of these landforms.

Interpretation of glaciotectonic complexes from analysis of thin-skinned thrust-fault structures in seismic sections, an example from the Jammerbugt in eastern North Sea.

Lars Ole Boldreel¹ and Stig A.S. Pedersen^2
1IGN, KU, ²GEUS
During the last decade, a number of glaciotectonic complexes have been recognized in the North Sea (Andersen 2005, Bendixen 2016, Larsen & Andersen 2005, Novak & Leth 2015, Pedersen & Boldreel 2017). The mapping of these complexes are merely depending on interpretation of qualified seismic data, which enables structural interpretation. This presentation demonstrates the complexity of seismic interpretation of glaciotectonic structures by the investigation of the Jammerbugt Glaciotectonic Complex.

The Jammerbugt Glaciotectonic Complex, eastern part of the North Sea, occupies an area of more than 300 km² located about 10 km offshore the west coast of northern Denmark. The bedrock included in the complex comprise the main part of the Cretaceous Chalk Group in the North Sea. The detachment surface in the proximal part of the complex occurs in Lower Cretaceous greensand about 400 m b.s.l. In the central part of the complex the thrusting ramps the strong reflectors at the base of the Chalk Group and the detachment surface continues in the lower part of the Upper Cretaceous chalk throughout the distal part.

The Eemian–Early Weichselian Skærumhede Group onlap the deformed beds at the boundary to the tectonic depression north of the complex indicating a Saalian age of the glaciotectonic deformation. The calculation of the displacement during balanced cross section construction demonstrates that the thrust sheets in the tailing end of the complex had their source in the Skagerrak Sea. Thus, we suggest that the hole caused by displacement of thrust sheets contributed to formation of the Skagerrak depression.

References
Andersen, L. T. 2004. The Fanø Bugt Glaciotectonic Trust Fault Complex, Southeastern Danish North Sea. Ph. D. Thesis 2004. Danmarks og Grønlands Geologiske Undersøgelse Rapport 2004/30: 1–143.

Bendixen, C. 2016: Aspects of the Quaternary evolution of the southern Kattegat and the central North Sea based on interpretation of 2D and 3D marine reflection seismic profiles. Ph.D. thesis University of Copenhagen, 35 pp.

Larsen, B., Andersen, L. T. 2005. Late Quaternary stratigraphy and morphogenesis in the Danish eastern North Sea and its relation to onshore geology. Netherlands Journal of Geosciences 84-2: 113–128.

Novak, B, Leth, J.O. 2015. Glaciotectonic thrust complex offshore Holmsland, the Danish North Sea. Abstract in The Quaternary Geology of the North Sea, Annual discussion Meeting of the Quaternary Research association UK, Edinburgh, January 2015: p. 71.

Pedersen, S.A.S. & Boldreel, L.O. 2017: Glaciotectonic deformations in the Jammerbugt and glaciodynamic development in the eastern North Sea. Journal of Quaternary Science, 32 (2), 183–195.

Computer supported 3D modelling of the Hanklit glaciotectonic complex, Mors, Denmark

Embla Galdal^1
1University of Copenhagen
The Hanklit coastal cliff is a glaciotectonic locality where an excellent cross-section through a thrust fault complex is exposed. The structural architecture and structural features of the glaciotectonic complex is modelled in the 3D modelling software, Leapfrog Geo.

The structural elements in the Hanklit Complex consist of thrust sheets interpreted to be the result of the Norwegian ice advance in a pro-glacial glaciotectonic deformation about 30-28,000 years ago. It consists of a 60m thick succession of Eocene diatomite overlain by 15m of glacial deposits. The Hanklit Thrust Sheet extends for more than 1km along the W-E strike and is displaced for more than 300m to the south (Klint & Pedersen, 1995). The Hanklit Thrust Sheet is thrusted across the foreland feature named Gullerup Thrust Sheet, whereas the Salgerhøj Thrust Sheet describes the northernmost thrust element ramping up and displaced upon the back of the Hanklit Thrust Sheet. In the frontal part of the Salgerhøj Thrust Sheet a hanging-wall anticline is developed with overturned limbs. This hanging-wall anticline can be followed for nearly 10km along the crest of the highest hills on Mors. A balanced cross section is provided. The depth to the décollement zone is determined and the displaced along the shallow dipping ramp and flat is calculated.

The Hanklit Thrust Fault Complex is a well-documented thrust fault structure, and the model is a good illustration of the thin skinned thrust fault, and can also be compared to structures that occurs in mountain ranges like the Jura mountains.

References
Klint, K. E. S. & Pedersen, S. A. S., 1995. The Hanklit Glaciotectonic Thrust Fault Complex, Mors, Denmark. DGU Serie A 35, 30 pp + insert.

Diagnosing ice sheet grounding line stability from landform morphology

Sarah Greenwood¹, Lauren Simkins² and John Anderson^2
1Department of Geological Sciences, Stockholm University, ²Department of Earth Science, Rice University
Marine-based ice sheet stability is largely dictated by processes at or near the grounding line, where marine and glacial processes and the topographic setting govern the duration of grounding line occupation and sensitivity to retreat. Landforms that are built at the grounding line, such as grounding zone wedges and recessional moraines, are inscribed extensively on formerly glaciated continental margins. These landforms directly mark former grounding line positions over a prolonged period of retreat (thousands of years), represent the history of sedimentation during the occupation of each position, and offer high potential for extracting information about grounding line dynamics.

We characterise the morphological traits and spatial distribution of thousands of grounding line landforms from the Ross Sea continental shelf, which mark Antarctic Ice Sheet retreat since the Last Glacial Maximum. Recessional moraines indicate a consistency of grounding line processes/setting and regularly forced retreat, while grounding zone wedges are highly variable in size and shape, developing both asymmetry and sinuosity during landform growth. We attribute growth of sinuosity to lateral variability in sediment delivery along the grounding line, linked to basal meltwater drainage. This development of sinuosity over time is commonly associated with larger-magnitude retreat events. A ‘stable’ grounding line position of relatively long duration may thus be linked with an ‘unstable’ retreat event. Landform construction is surprisingly insensitive to the local topographic setting. We explore the processes controlling the production of contrasting grounding line landform morphologies and, consequently, what these morphologies reveal regarding the (in)stability of a retreating ice sheet.

Details in glacial terrains detected from Digital Terrain Models brings new light upon the Danish glacial landscape

Michael Houmark-Nielsen^1
1Centre for GeoGenetics, Natural History Museum, University of Copenhagen, Denmark
Previously unnoticed landforms of former glaciated terrains in Denmark can now be revealed from studies using Digital Terrain Models (DTMs) provided by the Danish Geo-data Agency. The removal of buildings, vegetation etc. from DEMs with 25m, 10m and 1.6 m grids allow exposure of details in landforms not earlier subjected to investigation. GIS-based studies of hill shaded DTMs – on land as well as on the sea floor –combined with Quaternary geological mapping and data from open exposures as well as the use of the rich literature on the Danish glacial landscape and its origin, gives new insight into glacial landforms, that was formed along the lowland fringes of the Scandinavian Ice Sheet during the last two glaciations.

In this lecture focus will be on subglacial landforms and their distribution around the country. Here single or multiple generations of streamlined terrain with increasing size ranging from tens of meters to tens of kilometres are presented. Other subglacial features include eskers and tunnel-valleys. Examples are given on the combination of easily accessible on-land features and obscured terrains partly buried on the sea floor into a more whole appearance of glacial landforms. In order to establish a meaningful and modern model of the ice age landscapes in Denmark, subglacial terrains are but one of many pieces of the puzzle and they must be seen in relation to other glacial landforms such as terminal moraines, dead-ice land forms and features related to proglacial erosion and long time periglacial reshaping.

Mapping of glaciotectonic structures and associated sedimentary deposition with ground penetrating radar

Peter Roll Jakobsen¹, Hans Lerche and Cecilie Skovsø Andersen
¹GEUS
The analysis of glaciotectonic structures and geological setting is best done in outcrops, but as they are limited both in occurrence and in lateral extent, geophysical methods are often used to interpret the geology. Ground penetrating radar has proven to be an excellent method to determine sedimentary structures as well as deformation structures.

Examples of structural analysis are given from small composite ridges in the northwestern part of Jylland created during the general retreat of the Main Glacial Advance in the late Weichselian. Other examples are given from Northwest Sjælland where two georadar investigations were carried out in the rim of the large end-moraines from a re-advance of the Young Baltic Advance, about 17.000 years ago.

The radar profiles are differentiated into radar facies with distinct reflection characteristics. Glaciotectonic deformations such as thrusts and folds are interpreted from the GPR data. Furthermore syn-tectonic and post-tectonic sedimentation is interpreted from the radar profiles.

The examples show that the morphology of the ridges investigated is controlled by the deformation structures, and that penecontemporaneous sedimentary processes have smoothened the morphology created by the deformations.

Geomorphology and distribution of subglacial triangular hummocks (murtoos) in Sweden and Finland

Mark D. Johnson¹, Joni Mäkinen², Gustaf Peterson³, Antti Ojala⁴, Jukka-Pekka Palmu⁴, Kari Kajuutti², Christian Öhrling³ and Elina Ahokangas^2
1University of Gothenburg, ²University of Turku, ³Geological Survey of Sweden, ⁴Geological Survey of Finland
Triangular or V-shaped hummocks of subglacial origin have been identified in Sweden and Finland due to the increased resolution provided by LiDAR imagery. Their triangular shape is distinctive and recognizable as a clearly identifiable landform. These forms have been previously mapped in some cases as dead-ice hummocks, but geomorphic relationships with eskers, flutes and De Geer moraines show these to be subglacial. Good examples of these forms occur near Murtoojärvi, Finland, and we propose calling these new landforms ‘murtoos.’ Individual murtoos are diamond and triangular shaped with the axis of the triangle parallel to regional ice flow. Murtoos have a longitudinal spacing on 50 to 200 m, and their widths are on the order of 50 to 100 m. They are asymmetric with a gentle up-ice side and a steeper down-ice side. Often, they have a shingled appearance. In many cases, they occur in patches in an ice-flow parallel path with eskers defining corridors we believe to be of subglacial meltwater origin.

Murtoos are composed primarily of heterogeneous diamicton with minor amounts of bedded sand.

Murtoos are common in Finland and Sweden and we present a map of their distribution. They seem to be most common where ice-retreat rates were high during deglaciation, and they are absent where extensive frozen-bed conditions were present.

The framework of glaciotectonic complexes and their position in the glaciodynamic sequence stratigraphy

Stig Schack Pedersen^1
1GEUS
The analysis of glaciotectonic complexes uses the classification of architectural surfaces. These comprise four orders of surfaces (Pedersen 2014). The first order includes the décollement zone and the topographic surface, which define the bottom and the top of complexes. The second-order surfaces are the thrust-faults, which bound the thrust sheets and duplexes that constitute the internal framework of tectonic complexes. The third order comprises folded beds appearing in the internal structure of thrust sheets. The fourth order includes all small-scale structures like joints and faults with minor displacement, which are important for the prediction of dynamic development (Pedersen 2000).

For the interpretation of the dynamic development, three macroscopic regimes are defined: the distal, the central and the proximal part of glaciotectonic complexes (Pedersen 2005). In the distal regime close to the foreland, flat-lying thrust-faults displace thin thrust sheets. In the central regime, steep dips of thrust faults occur together with hanging-wall anticlines. Towards the proximal part of complexes superimposed deformation of duplexes occur, which result in vertical orientation of surfaces. Glaciotectonic complexes may include superimposed deformation related to development in one event or superimposing of several events. Glaciodynamic events are differentiated by application of glaciodynamic sequence stratigraphy, which combines depositional and structural features (Pedersen 2012).

References

Pedersen, S.A.S. 2000: Superimposed deformation in glaciotectonics. Bull. Geol. Soc. Denmark 46, 125-144.

Pedersen, S.A.S. 2005: Structural analysis of the Rubjerg Knude Glaciotectonic Complex, Vendsyssel, northern Denmark. Geol. Surv. Denmark & Greenland Bull. 8, 192 pp.

Pedersen, S.A.S. 2012: Glaciodynamic sequence stratigraphy. In: Huuse, M., Redfern, J., Le Heron, D.P., Dixon, R.J., Moscariello, A. & Craig, J. (eds.): Glaciogenic Reservoirs and Hydrocarbon Systems. Geol. Soc., London, Spec. Publ. 368, 29–51.

Pedersen, S.A.S. 2014: Architecture of glaciotectonic complexes. Geosciences 2014, 4, 269-296.

Subglacial till deformation: lessons from laboratory experiments

Jan A. Piotrowski¹, Mia Bering Holdensen¹, Włodzimierz Narloch², Simon Carr³, Anders Damsgaard⁴ and Nicolaj Krog Larsen^1
1Department of Geoscience, Aarhus University, DK-8000 Aarhus C, Denmark, ²Department of Geology and Hydrogeology, Nicolaus Copernicus University, PL-87-100 Toruń, Poland, ³School of Geography, Queen Mary University of London, London E1 4NS, UK, ⁴Geophysical Fluid Dynamics Laboratory, Princeton University, Princeton, NJ 08540, USA
In a detailed study of mega-scale glacial lineations (MSGLs) left by a Weichselian palaeo-ice stream in Poland, Spagnolo et al. (2016) analysed multiple parameters of the land-forming till and concluded that it originated by a combination of lodgement and thin-skinned deformation whose cumulative effect was the formation of the MSGL field.

To advance our understanding of till formation and deformation postulated by Spagnolo et al. (2016) we conducted a series of experiments on this till in a large ring-shear apparatus intended to mimic subglacial shearing (Bering Holdensen 2017). Undisturbed, oriented samples for micromorphological analyses were taken at displacement increments of 0, 9, 18, 36, 72, 144, 288, 576 and 1152 cm.

Till microstructures mapped on thin sections across the zone of shearing gave intriguing and hitherto unmatched insights into the development and evolution of till properties during the shearing under controlled boundary conditions. The deformation signatures often varied non-systematically between the sampled increments. Three-dimensional microtomographic scanning showed intervals of relatively stable till fabrics intervening with phases of fabric re-orientation towards new equilibria. Shear stresses during the deformation showed a distinct cyclicity possibly indicating formation and collapse of grain bridges.

Collectively, we interpret the ring-shear data as a signature of permanent and sometimes unsystematic evolution of till structure with a general trend towards more ductile and less brittle deformation with increasing strain. These results bear on the reconstruction of past subglacial processes and we advocate extreme caution with interpreting the history of natural tills based on the micromorphological signatures alone.

References

Spagnolo, M., Phillips, M., Piotrowski, J.A., Rea, B.R., Clark, C.D., Stokes, C.R., Carr, S.J., Ely, J.C., Ribolini, A., Wysota, W. & Szuman, I., 2016. Ice stream motion facilitated by a shallow-deforming and accreting bed. Nature Communications 7:10723, doi: 10.1038/ncomms10723.

Bering Holdensen, M., 2017. Ring-shear experiments on subglacial till deformation. M.Sc. thesis, Department of Geoscience, Aarhus University, Denmark, 148 pp.

Glacial landform evolution in transitional cold – warm bed subglacial conditions in the central part of Scandinavian Ice Sheet, in northern Finland

Pertti Sarala^1
1Geological Survey of Finland, P.O. Box 77, 96101 Rovaniemi, Finland/Oulu Mining School, Univ. Oulu
On-going glaciomorphological mapping in Finland based on airborne LiDAR (Light Detection And Ranging) interpretation has revealed new data that is useful for the glaciodynamic examination in the glaciated terrain. One of the key study areas in Finland has been the Kuusamo Ice Lobe area close to the Late Weichselian ice-divide zone in Finnish Lapland. The glacial morphology of the ice lobe is composed mainly of moraine morphologies such as the glacial streamlined lineations of the Kuusamo drumlin field in the eastern part and different hummocky and ribbed moraines in the western part, i.e. at the core of the ice lobe. The drumlin field was formed under surging type glacial movement during Younger Dryas while the core part of the glacier remained cold-based. Glaciofluvial deposits (eskers and delta formations) occur in places representing last deglaciation phase. Particularly, ribbed moraines represent the depositional formations formed under subglacial conditions at the transitional zone between the warm and cold based glacier. However, an erosional, subglacial meltwater channel network cutting the ribbed moraine formations before the deposition of glaciofluvial deposits and smoothly lineated surface of morainic terrains by glacier reworking gives new knowledge of the formation phases of subglacial moraine formations in the core part of continental glacier. As the subglacial meltwater activity that formed the erosional channel system and later channel fills such as eskers was worked after ribbed moraine formation, the origin of the ribbed moraines must be earlier process, happened close to cold-based core part.

Active retreat of a Late Weichselian marine-terminating glacier revealed by large-scale glaciotectonics in Melasveit, western Iceland

Thorbjörg Sigfúsdóttir¹, Ívar Örn Benediktsson² and Emrys Philliips^3
1Department of Geology, Lund University, Sweden & Institute of Earth Sciences, University of Iceland, ²Institute of Earth Sciences, University of Iceland, ³Birtish Geological Survey, Edinburgh, UK
Large and complete glaciotectonic sequences formed by marine-terminating glaciers are rarely observed on land, hampering our understanding of the behaviour of such glaciers and the processes operating at their margins. During the Late Weichselian in West Iceland, marine-terminating glaciers deformed glaciomarine sediments. These formations are now exposed in >5km long coastal cliffs in the Melasveit district, recording past glacier dynamics and the interrelationship between glaciotectonic and sedimentary processes under/in front of a marine terminating glacier. The sedimentology and glaciotectonic architecture of the coastal cliffs reveals a series of subaquatic moraines formed by a glacier emanating from Borgarfjörður to the north. The style of deformation demonstrates that these moraines were primarily built up by ice-marginal/proglacial thrusting and folding of marine sediments as well as deposition and subsequent deformation of ice-marginal subaquatic fans. The southernmost and largest of the moraines is over 1.5 km wide and more than 30 m high and is interpreted to indicate the maximum extent of the Borgarfjörður glacier. Generally, the other moraines become progressively younger towards the north, designating an advances or still-stands of the glacier as it oscillated during an overall retreat. Glaciomarine sediments rapidly accumulated in front of the glacier and filled in the depressions between the moraines when the glacier finally receded from the area. Previously obtained radiocarbon dates from the deformed sequence suggest that these moraines were formed in the Younger Dryas. This study highlights the dynamics of marine-terminating glaciers and may have implications for the interpretation of their sedimentological and geomorphological records.

Glaciotectonic analysis of the geology in the NE part of Sjælland, Denmark, based on interpretation of vibro seismic data along the west bank of Esrum Sø

Line Winsløw¹, Stig A. S. Pedersen² and Lars O. Boldreel^1
1Copenhagen University, ²GEUS
In the northeastern part of Sjælland, two outstanding morphological elements are present: the composite hill ridges characterizing the terrain in Gribskov and the elongated depression lodging Esrum Sø. A simple glaciodynamic interpretation of their formation is that they represent a hill-and-hole pair with Esrum Sø representing the hole from where the material for the composite hills in Gribskov derived. This interpretation satisfies the general N–S trend of the morphological elements.

However, the northern part of Esrum Sø trends SE–NW parallel to the buried Esrum-Alnarp valley suggesting a tectonic origin of the lake morphology. For the investigation of this hypothesis, a 6.3 km vibro seismic profile was collected along the western bank of the lake. During the analysis of the seismic profile, a large glaciotectonic complex was recognized. The complex comprises five sections, which characterize the distal to the proximal structural development. The translation of the complex was from a northerly to a southerly direction over a décollement surface, which stepwise rises from 95 m b.s.l. in the northern proximal region shallowing toward the southern distal region. The glaciotectonic complex comprises ramps and flats with related hanging wall and footwall structures.

The glaciotectonic complex developed during the advance of the Scandinavian Ice sheet in the Late Weichselian (30,000-20,000 B.P.). During the initial phase, glaciofluvial sediments accumulated proglacially. These were later thrusted into piggyback duplexes. Following the recession of the ice, a glaciolacustrine environment appeared. In a final phase, a superimposed glaciotectonic deformation occurred concluding the development the glaciotectonic complex.

References
Houmark-Nielsen, M. 1990: Late glacial stratigraphy and deglaciation pattern in eastern Denmark. Lundqua 32, 31-34.

Konradi, P. B. 1992.De marine kvartære aflejringer i Esrumdalen. Dansk geol. Foren., Arsskrift for 1990-91. side 111-115, Kobenhavn.

Pedersen, S. 2000. Superimposed deformation in glaciotectonics. Bulletin of the Geological Society of Denmark. Vol. 46, pp. 125–144, Copenhagen.

Pedersen, S. A. S., 2012. Glaciodynamic sequence stratigraphy. Geological Society, London, Special Publications V. 368, 29–51.

                       POSTER PRESENTATIONS                    

Subglacial or Pro-glacial Deformed Middle-Late Weichselian Ridges in Jyderup Skov, Odsherred, Denmark

Cecilie Skovsø Andersen^1
1Former student at University of Copenhagen
The aim of this study is to investigate the glaciotectonic deformation of the ice-push ridges on the outer edge of the Vig-Hønsinge Arc in Jyderup Skov, Odsherred, Denmark. By measurements of Ground Penetrating Radar (GPR) reflections profiles across the structures, the project will aim to produce a geological model with emphasis on a structural analysis of deformed meltwater sediments. The ridges are parallel to the terminal moraine of the Vig-Hønsinge Arc formed by the Bælthav Readvance and are located on the proglacial meltwater plain ahead of the terminal moraine. The ridges were investigated by six 250 MHz GPR lines perpendicular to the ridges and one GPR line striking parallel to the ridges. The GPR lines were successfully recorded and needed only very little processing and patience with estimating the migration velocity, as diffractions were many. 8 Facies have been determined from the radar stratigraphic analysis. Two facies of glacio-fluvial sand and gravel, which are folded and thrusted respectively indicating both ductile and brittle style deformation, with complex imbricate fans. Additionally, deformed seasonal outwash, channels, till, kames, landslides and cover sands are interpreted as well. The GPR lines are deformational shortened by 7 % on average. Two different scenarios are suggested to explain this deformation; A: A surge and sustained advance and B: Recession on an annual scale. Based on the distribution of the radar stratigraphic facies is scenario B interpreted to be the most likely one to have happened.

New subglacial landforms detected from LiDAR data

Kari Kajuutti¹, Joni Mäkinen¹, Elina Ahokangas¹, Antti Ojala² and Jukka-Pekka Palmu^2
1University of Turku, ²Geological Survey of Finland
High-resolution DEMs produced from LiDAR provide a revolutionary tool for the mapping and documentation of glacial landforms over wide areas (e.g. Johnson et al. 2015). The main resource for this study was the Maankamara map service (http://gtkdata.gtk.fi/maankamara/) of the Geological Survey of Finland (GTK) where LiDAR data is supplemented with base maps and maps of the Quaternary deposits as well as bedrock, striation and the highest shoreline data. Indeed, while studying the deglaciation of the past Scandinavian ice sheet after the Salpausselkä III stage in SW Finland (Kajuutti et al. 2016), our attention was drawn to formations being surprisingly regular triangles in shape.

Even though the triangular landforms are clearly identifiable from LiDAR-based DEMs, they are almost impossible to detect from map contour-lines, other remote sensing images or even in the field within forest covered areas. The triangles consist of till and are typically 100 – 200 m long and 2 – 5 m high. Our hypothesis is that the triangular landforms and related other features belong to routed, large-scale subglacial drainage systems forming a continuum between channelized (eskers) and more widely spread small-scale distributed subglacial drainage (Mäkinen et al. 2017).

We have started co-operation with Swedish researchers (cf. Peterson et al.) aiming to a joint publication that will show the distribution of the triangles in both countries and moreover expand our knowledge of their sedimentology and origin. The name for the new landforms will be published both in our forthcoming paper as well as in the NGWM meeting.

References

Johnson, M.D., Fredin, O., Ojala, A.E.K., Peterson, G., 2015. Unraveling Scandinavian geomorphology: the LiDAR revolution. GFF 137, 245e251.

Kajuutti, K., Mäkinen, J., Palmu, J.-P. 2016: LiDAR-based interpretation of deglacial dynamics in SW Finland. In: Staubolis, S., Karvonen, T., Kujanpää, A. (Eds.), Abstracts of the 32nd Nordic Geological Winter Meeting 13the15th January 2016. Bull. Geol. Soc. Finl, Helsinki, Finland, p. 314, 2016.

Mäkinen J., K. Kajuutti, J.-P. Palmu, A. Ojala & E. Ahokangas 2017: Triangular-shaped Landforms Reveal Subglacial Drainage Routes in SW Finland. Quaternary Science Reviews 164, 37-53.

Peterson, G., Johnson, M.D. & Smith, C.A. 2017: Glacial geomorphology of the south Swedish uplands – focus on the spatial distribution of hummock tracts. Journal of Maps 13:2, 534-544.

Using large-scale patterns and morphology of subglacial meltwater corridors to gain insight into the spatial organisation, formation and evolution of meltwater drainage beneath ice sheets

Emma Lewington¹, Stephen Livingstone¹, Andrew Sole¹, Chris Clark¹ and Sarah Greenwood^2
1The University of Sheffield, ²Stockholm University
While spatio-temporal variations in the efficiency of the subglacial drainage system have been identified as a key control on ice sheet dynamics, the inaccessibility of the bed means its precise character and evolution remains poorly understood. Palaeo-bedforms provide one solution to this, enabling the reconstruction of relict networks over large areas. Such investigations have been facilitated by the release of freely available, high-resolution digital elevation models (e.g. ArcticDEM).

This study focuses on subglacial meltwater corridors (SMCs), characterised as elongated tracts of hummocky sediments often associated with eskers, glaciofluvial sediments and eroded bedrock. Similar features have been recognised before (e.g. Rampton et al., 2000; Utting et al., 2009; Peterson et al., 2017) but their distribution over ice-sheet scales has yet to be considered. This is an important consideration for determining the formation of these features and confirming their link to subglacial meltwater i.e. identifying the source, magnitude and duration of flow required.

We use a large-scale mapping approach to understand the spatial pattern of palaeo-subglacial flow beneath large parts of the former Laurentide and Fennoscandian ice sheets. An automated method for identifying and mapping these features is developed based on the high degree of roughness within these channels which distinguishes them from the surrounding bed. The outputs of this approach are compared to traditional manual techniques and detailed morphological investigations to provide insights into the nature of the drainage system and to contextualise limited observations of contemporary subglacial meltwater drainage.

References
Peterson, G. Johnson, M.D. Smith, C.A. 2017: Glacial geomorphology of the south Swedish uplands – focus on the spatial distribution of hummock tracts. Journal of Maps. 13:2. 534-44.

Rampton, V.N. 2000: Large-scale effects of subglacial meltwater flow in the southern Slave Province, Northwest Territories, Canada. Canadian Journal of Earth Sciences. 37(1). 91-93.

Utting, D.J. Ward, B.C. Little, E.C. 2009: Genesis of hummocks in glaciofluvial corridors near the Keewatin Ice Divide, Canada. Boreas. 38(3). 471-81.

Sedimentology of the new subglacial landforms detected from LiDAR data in SW Finland

Joni Mäkinen¹, Kari Kajuutti¹, Antti Ojala², Jukka-Pekka Palmu² and Elina Ahokangas^1
1Department of Geography and geology, University of Turku, ²Geological Survey of Finland
New triangular-shaped glacial landforms have been identified and described from LiDAR-based DEMs in SW Finland (Kajuutti et al. 2016; Mäkinen et al. 2017). Our hypothesis is that they and related other features belong to routed, large-scale subglacial drainage systems forming a continuum between channelized (eskers) and more widely spread small-scale distributed subglacial drainage.

We present the first sedimentological description of the new triangular landform from SW Finland and tentatively discuss the depositional environment and related processes. The general sediment characteristics include stratified gravel-sand core covered by loose sandy/gravelly, massive/matrix-supported diamictons interbedded with disturbed, laminated sand beds. The paleoflow pattern is lobe-shaped with boulder-rich margin. Maximum size of the boulders in the sediment is ca. 1 m and the clasts are angular to edge-rounded. The sediment characteristics do not fit into current conception of subglacial glaciofluvial deposits or tills, but rather support the continuum between these as also indicated by the morphological characteristics.

Ongoing co-operation with Swedish researchers (cf. Peterson et al. 2017) will expand our knowledge on the sedimentology and genesis of these new landforms. Their name will be published both in our forthcoming paper as well as in the NGWM meeting.

References
Kajuutti, K., Mäkinen, J., Palmu, J.-P. 2016: LiDAR-based interpretation of deglacial dynamics in SW Finland. In: Staubolis, S., Karvonen, T., Kujanpää, A. (Eds.), Abstracts of the 32nd Nordic Geological Winter Meeting 13the15th January 2016. Bull. Geol. Soc. Finl, Helsinki, Finland, p. 314, 2016.

Mäkinen J., K. Kajuutti, J.-P. Palmu, A. Ojala & E. Ahokangas 2017: Triangular-shaped Landforms Reveal Subglacial Drainage Routes in SW Finland. Quaternary Science Reviews 164, 37-53.

Peterson, G., Johnson, M.D. & Smith, C.A. 2017: Glacial geomorphology of the south Swedish uplands – focus on the spatial distribution of hummock tracts. Journal of Maps 13:2, 534-544.

Sedimentological and morphological implications for the understanding of murtoo formation in Sweden

Gustaf Peterson¹, Mark D. Johnson² and Christian Öhrling^3
1Department of Earth Sciences, Gothenburg University, Göteborg; Geological Survey of Sweden, Uppsala, ²Department of Earth Sciences, Gothenburg University, Göteborg, ³Geological Survey of Sweden, Göteborg
During glacial landform mapping in southern Sweden, a new distinct landform was detected, which we refer to as murtoos. The landform appearance is a V-shaped hummock, generally pointing down ice with an asymmetric vertical profile along its axis. The LiDAR DEM of Sweden has been surveyed for murtoos, and they commonly throughout the country, most frequently north of the Younger Dryas ice margin and in areas deglaciated during Bølling-Allerød in the south. We have excavated murtoos at four localities and have studied the internal structure through detailed sediment description. The distribution, geomorphology and sedimentological properties of murtoos collected here provide an opportunity to understand their genesis.

Murtoo sizes are roughly 10-100 meters wide, 5 to 50 m long, and 2-10 meters high. The individual murtoos have an overlapping appearance and occur as fields. In places, elongated fields trend parallel to the overall ice flow direction. Commonly, Murtoos occur in close relation to ribbed moraine and, in places, they are draped by eskers and overprinted by flutes, indicating murtoos form subglacially. Murtoos predominantly consist of a heterogeneous sandy gravelly diamicton, with angular to sub-angular clasts. Lenses of sorted sediments are intermixed in the diamicton and boulders are common on the surface. Further, their distribution in Sweden suggests a formation during periods of rapid ice retreat. We list multiple hypotheses, their pros and cons, and discuss them to shed light on the formative process.

A new glacial deposits and features database of Finland

Niko Putkinen¹, Pertti Sarala¹, Satu Putkinen¹, Jukka-Pekka Palmu¹ and Antti E. K. Ojala^1
1Geological Survey of Finland
Renewing of the glacial deposits and features database is going-on in the Geological Survey of Finland (GTK). It includes both a new definition of the landform categories and mapping work based on the 2-metre resolution LiDAR (Light Detection And Ranging) data interpretation with ArcGIS software. Preliminary sources for map polygons and lines are: 1. LiDAR-DEM data provided by National Land Survey of Finland, 2. GTK’s Quaternary geological 1:20 000 and 1: 200000 data, 3. aggregate, engineering geological and groundwater aquifer investigations. The multi-year project aims to produce ‘the best mapping data for each location in Finland’ with a cost-effective, minimal fieldwork approach. The mapping process combines both the main geological unit (deposit) and a new, landsystems-based glacial geomorphological feature information. Recent studies have shown that previously detected large mega-scale glacial features, such as mega flutings, drumlins, end moraine complexes and glacial melt water systems show up in LiDAR-based digital elevation models (DEM) in greater detail than ever before (Putkinen et al., 2017). The new map database will significantly improve mineral exploration, groundwater studies, land use planning and management. In the future, the database will be linked to the nationwide stratigraphical units and be extended to the national subsurface 3D database. The glaciodynamic themes included in the database are: Glacifluvial deposits, glacially lineated terrains and various types of other moraine types referred to much slower ice flow velocities or different glacier margin landforms (ribbed moraines, hummocky moraines, De Geer moraines and end moraines).

References
Putkinen, N., Eyles, N., Putkinen, S., Ojala, A.E.K., Palmu, J.-P., Sarala, P., Väänänen, T., Räisänen, J., Saarelainen, J., Ahtonen, N., Rönty, H., Kiiskinen^, A., Rauhaniemi^, T. & Tervo, T. 2017. High-resolution LiDAR mapping of glacial landforms and ice stream lobes in Finland, Bulletin of the Geological Society of Finland (Published online 28 September 2017)

8.3. Open session Quarternary geology

                       ORAL PRESENTATIONS                    

Repeated fluvial sedimentation during the late Pleistocene in Kitinen valley, Sodankylä

Annika Katarina Åberg¹, Anu Kaakinen¹ and Veli-Pekka Salonen^1
1Department of Geosciences and Geography, University of Helsinki, P.O. Box 64, 00014 Helsinki
New studies confirm (Sarala et al. 2015, 2016, Lunkka et al. 2015) that Weichselian glaciation in Central Lapland has been more complex than previously assumed. Three to four interstadials have been suggested based on the existence of intertill sorted deposits and pollen assemblages of organic layers. In addition, subtill fluvial deposits have now been discovered in test sections of Kärväsniemi, in Sodankylä, indicating that the area was ice-free during Early and Middle Weichselian. The Kärväsniemi site consists of three till beds and four sorted sediment units. The OSL ages of the lower fluvial deposit vary between 67-79 ka, suggesting deposition during Odderade (MIS 5a). The upper sorted deposit, interpreted as fluvial bar and channel lag deposit, may have deposited during Middle Weichselian interstadials (MIS 3). These two subtill sorted deposits, separated by a thin till unit, could be also correlated to Tärendö I and Tärendo II (Hättestrand & Robertsson 2010) of the Riipiharju stratigraphy in northern Sweden. The sorted deposits in Kärväsniemi can be correlated with the lacustrine deposits of Sokli (Helmens et al. 2007).

A 3D model of surficial deposits was generated along with a GIS database and GPR interpretations to study sedimentation in the Kärväsniemi area (Åberg et al. 2017). The sedimentation history in Kärväsniemi has at least three phases of fluvial deposition, disturbed by deposition of three till units. The non-destructive contacts of the overlaying tills suggests that they were deposited from a stagnant frozen-bed ice sheet indicating an overall weak glacial erosion in Kärväsniemi.

References
Helmens K.F., Johansson P.W., Rasanen M., Alexanderson H. & Eskola K.O. 2007. Ice-free intervals continuing into Marine Isotope Stage 3 at Sokli in the central area of the Fennoscandian glaciations. Bulletin-Geological Society of Finland 79: 17.

Hättestrand M. & Robertsson A.-M. 2010. Weichselian interstadials at Riipiharju, northern Sweden – interpretation of vegetation and climate from fossil and modern pollen records. Boreas 39: 296-311.

Lunkka J.P., Sarala P. & Gibbard P.L. 2015. The Rautuvaara section, western Finnish Lapland, revisited: new age constraints indicate a complex Scandinavian Ice Sheet history in northern Fennoscandia during the Weichselian Stage. Boreas (Oslo) 44: 68-80.

Sarala P., Räisänen J., Johansson P. & Eskola K.O. 2015. Aerial LiDAR analysis in geomorphological mapping and geochronological determination of surficial deposits in the Sodankylä region, northern Finland. GFF 137: 293-303.

Sarala P., Väliranta M., Eskola T. & Vaikutiené G. 2016. First physical evidence for forested environment in the Arctic during MIS 3. Scientific Reports Vol. 6: 1-9.

Åberg A.K., Salonen V.-P., Korkka-Niemi K., Rautio A., Koivisto E. & Åberg S.C. 2017. GIS-based 3D sedimentary model for visualizing complex glacial deposition in Kersilo, Finnish Lapland. Boreal environment research 22: 277-298.

An interglacial deposit from Copenhagen, Denmark: marine isotope stage 7

Ole Bennike¹, Jens Galsgaard², Joakim Stiel Korshøj², Geoffrey Lemdahl³, Kirsty Penkman⁴ and Richard Preece^5
1GEUS, ²GEO, ³Kalmar University, ⁴York University, ⁵Cambridge University
During the construction of a new Metro station in Copenhagen, fossiliferous organic sediments were encountered. An investigation was undertaken on the organic sediments, which occurred beneath a succession of a lower till bed, glaciofluvial sand and gravel, an upper till bed and glaciofluvial sand. The organic sediments were rich in plant fossils and the flora show that the region was forested but included some light-demanding species. The flora includes Najas minor, which today has a northern geographical range limit in Germany. Shells of freshwater molluscs were frequent, but the diversity was rather low. Bithynia opercula were abundant, allowing the sediments to be put into an aminostratigraphical framework. The amino acid racemisation ratios indicate that the organic sediments formed during early MIS 5e or more likely during MIS 7. The older attribution is consistent with OSL ages of 206 and 248 ka. The assemblages from Trianglen are similar to those reported from deposits recovered during the construction of the free port (1.4 km away) in Copenhagen in 1892, except that Corbicula was not found at Trianglen. The presence of Corbicula indicates a pre-Eemian age. AAR data from Bithynia opercula from the free port were almost identical to those from Trianglen, indicating that the two sites are contemporary. We suggest the Trianglen interglacial be used as a local name for the MIS 7 interglacial deposits.

A bag of sand from the ice-concealed, 31 km large Hiawatha crater in North-West Greenland: samples of the impact plume, ejecta blanket and crater floor from a recent meteorite impact through the Greenland ice sheet

Adam A. Garde¹, Tod E. Waight², Christian Weikusat³, Carsten Guvad¹, Svend V. Funder⁴, Kurt H. Kjær⁴, Iain McDonald⁵, Jette D. Møller⁶ and Gernot Nehrke^3
1Geological Survey of Denmark and Greenland, Denmark, ²Department of Geosciences and Natural Resource Management, University of Copenhagen, Denmark, ³Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany, ⁴Centre for GeoGenetics, Natural History Museum, University of Copenhagen, Denmark, ⁵School of Earth and Ocean Sciences, Cardiff University, U.K., ⁶Natural History Museum, University of Copenhagen, Denmark
Hand-picked, sand-sized grains from a recent glaciofluvial sediment from the Hiawatha Glacier draining the Hiawatha impact crater, Inglefield Land in North-West Greenland, provide rare new insight into melting and crystallisation processes and unusual incorporation of organic carbon in the uppermost parts of a large, young impact structure.

The bulk sand composition mimicks the regional Palaeoproterozoic, granulite-facies paragneiss bedrock. Predominating {10-13}, {10-12} orientations of shock lamellae in quartz indicate a threshold shock pressure of >16 GPa. Yellow, green, brown and black, variably carbon-bearing glass fragments have feldspar-, biotite- or garnet-like compositions and high volatile contents suggesting direct melting of these minerals and admixture of H₂O and organic carbon. Microporphyritic to microcrystlline particles have similar and occasionally crustal-melt-like compositions. Microliths of euhedral, zoned and/or skeletal feldspar, orthopyroxene, clinopyroxene, ilmenite and cordierite suggest rapid crystallisation and partial quenching. An ellipsoidal grain with radial crystallites may represent a melt droplet from the impact plume. Ejecta blanket? microbreccias with glassy or microcrystalline matrix contain abundant bedrock mineral splinters.

Sand-sized carbonaceous grains and centimetre-sized charcoal fragments picked from glacier ice preserve conifer cell structures; their highly variable reflectance corresponds to 150-1200°C heating. Raman graphite-o-peak spectra of carbon in microbreccia matrix, glass and microlith coatings likewise show a wide range of ordering without evidence of metamorphic overprinting, unlike carbon in the Norwegian Gardnos crater (Parnell & Lindgren 2006). The Hiawatha carbon was probably derived from Pleistocene tree trunks buried under the ice; the ice sheet likely protected them from being blown away during the initial impact phase.

References
Parnell, J. & Lindgren, P. 2006: Survival of reactive carbon through meteorite impact melting. Geology 34, 1029–1032.

The Last Glacial and Holocene Seismostratigraphy and sedimentation history of the Lake Bolshoye Schuchye, Polar Ural, Arctic Russia

Haflidi Haflidason¹, Julie Lundekvam Zweidorff², Richard Gyllencreuz³, John-Inge Svendsen² and Slava Gladysh^4
1Dept. of Earth Science and BCCR, University of Bergen, Allégt. 41, POBox 7803, N-5020 Bergen, Norge, ²Dept. of Earth Science and BCCR, University of Bergen, Allégt 41, POBox 7803, N-5020 Bergen, Norway, ³Department of Geological Sciences, Stockholm University, 10691 Stockholm, Sweden, ⁴I.S. Gramberg VNIIOkeangeologia, Sonic Group, 190121, St.Petersburg, RUSSIA
The seismostratigraphic studies of the 11 km² and the 136 m deep Lake Bolshoya Schuchye, Polar Ural, Arctic Russia, have unrevealed that the lake is apparently preserving up to a 130-150 m thick pile of seismostratigraphic laminated sediments. With aid of a Sparker array seismic and sub bottom profiling (SBP) surveys a dense grid of profiles have been collected allowing the sediment distribution and the geometry of the sediment units to be mapped out in some details. Three regional seismic horizons have been identified and correlated with the well dated 24 m long core retrieved from the lake. The detailed time constrain available on the upper stratigraphic units in the lake offer also excellent possibility to calculate the development in sediment fluxes in this Polar area from the Last Glacial Maximum (25 ka BP) to the present day. The detailed grid of seismic survey has also allowed the total sediment volume in the lake basin to be calculated and integrated with the well dated core the age of the initial sedimentation in the lake basin has been calculated to have started c. 55 ka BP, with a few thousand years uncertainty. Identification of submerged delta inside the lake basin suggest that the lake level must have dried in and be lowered with at least 26 m below the present level during the LGM period. This finding offer a new insight into the climate condition in the Polar Ural area, Arctic Russia, during the LGM and the early deglaciation period.

Sandy deposits from a Preboreal glacier lake outburst flood (Nedre Glomsjø), southeastern Norway

Louise Hansen¹, Fredrik Høgås¹, Lars Olsen¹ and Georgios Tassis^1
1Geological Survey of Norway
The major outburst flood from glacier lake Nedre Glomsjø in southeastern Norway, has been known for decades. Previously described deposits include pronounced boulder accumulations upstream and vast fine-grained flood deposits far downstream. In addition, new LiDAR data from the middle reaches of the Glomma valley has revealed spectacular mega bars and erosional features related to the dramatic flood event (Høgaas & Longva 2016). The LiDAR data provide a basis for further investigation of the event and its impact on the landscape and the valley fill. Sedimentological investigation of a sandy dune field provides new insight into the variety of deposits from the outburst flood. The dunes were previously described as of aeolian origin. However, facies analysis shows that the deposits were deposited in association to the outburst flood. Beside the association with water-lain facies, such as e.g. diffuse, climbing ripple lamination, a diagnostic feature seems to be water-escape structures defined by numerous (sub)vertical tracks cutting through the bedding including the foresets of mega-scale bedforms. The tracks are interpreted as a result of a significant drop in hydrostatic pressure as the flood levels were lowered and triggered a release of excess pore pressure in the sediments. The study extends the understanding of the outburst flood as an extreme, landscape-defining event. In addition, the study has important impact on the understanding of the regions postglacial landscape as other, previously defined aeolian fields may show to originate from the flood, and comparable sedimentary features have been observed at Starmoen nature reserve.

References
Høgaas, F. & Longva, O. (2016) Mega deposits and erosive features relate to the glacial lake Nedre Glomsjø outburst flood, southeastern Norway. Quaternary Science Reviews 151, 273-291.

The Quaternary of the island of Falster, SW Denmark

Peter Roll Jakobsen¹ and Knud Erik Klint^2
1GEUS, ²GEO
The island of Falster is covered by the geological map sheets Geological map of Denmark 1:50.000 Stubbekøbing and Nykøbing Falster. During the geological mapping new data was collected regarding Quaternary stratigraphy, morphology and the evolution of the landscape.

The pre-Quaternary deposits on Falster are Maastrichtien chalk and Paleogene Clay. The pre-Quaternary surface is influenced by NW–SE-striking faults that act as weakness zones, and buried valleys are incised into the chalk surface. At Stubbekøbing, the course of the Fribrødreå valley is controlled by a fault.

The oldest till unit on Falster is seen in boreholes and is interpreted as the Ristinge Klint Till Formation (c. 50 000 years ago).

At Pomlenakke and on Farø sections show a till deposited by a glacier coming from NE, which is interpreted as the Midtdanske Till Formation (Late Weichselian 24 000–20 000 years ago). It is covered by two Baltic tills – Øst Jylland Till Formation and Bælthav Till Formation (19 000–16 000 years ago). A characteristic boulder pavement is seen at the base of the lower unit. The boulders are often more than 1 m in diameter.

The most pronounced geomorphological element is the push moraine Væggerløse Arc, formed by an advance from east. An esker stretches from the north-easternmost part of Falster and almost down to Nykøbing Falster. A small meltwater plain is associated with the esker. In the Northern part smooth ridges with a NW-SE trend are interpreted as older marginal moraines, subsequently overridden by glaciers.

A large young impact crater beneath the Ice in Northwest Greenland

Kurt H. Kjær¹, Nicolaj K. Larsen², Svend Funder¹, Michael Houmark-Nielsen¹, Adam Garde³, Mark Fahnestock⁴, Ian McDonald⁵, Olaf Eisen⁶, Joseph MacGregor⁷, Anders Bjørk¹, Veit Helm⁶, Eske Willerslev¹, Matheu Morlighem⁸, Jeremie Mouginot⁸, Henning Haack⁹, Kristian K. Kjeldsen¹⁰, Horst Machguth¹¹, Tobias Binder⁶, John Paden¹² and Shfaqat Abbas Khan^10
1Centre for Geogenetics, University of Copenhagen, ²Dept. of Geoscience, Aarhus University, ³Geological Survey of Denmark and Greenland, ⁴University of Alaska Fairbanks, ⁵Cardiff University, ⁶Alfred Wegener Institute, ⁷NASA, ⁸University of California, ⁹Geobiology and Minerals Section, University of Copenhagen, ¹⁰DTU Space, ¹¹University of Zurich, ¹²University of Kansas
During Earth’s history, cataclysmic impact events have been linked to major climate change and mass extinctions. Here, we report on the discovery of a large impact structure hidden beneath Hiawatha Glacier in northwest Greenland. Beneath nearly a kilometre of ice lies a 31-kilometre-wide, circular bedrock depression with an elevated rim and a subdued central peak. Outwash sediments from the largest river draining from the glacier catchment contains shocked quartz and other unweathered impact grains. Geochemical analysis shows that the impactor was a Pt-rich iron asteroid that would have had a diameter of c. 1.5 km in order to produce a crater of the observed size. Radiostratigraphic, morphological and geochemical evidence suggest that the Hiawatha impact took place between 38 and 11.7 kyr ago, which would make it the largest known impact experienced by modern humans. Our discovery has potentially wide-ranging implications for our understanding of the recent history of Earth.

Provenance and ¹⁰Be surface exposure age of Late Weichselian glacial erratic boulders in southern Norway

Henriette Linge¹, Lukas Becker¹, Jenny Eidsvåg¹ and Derek Fabel^2
1Department of Earth Science, University of Bergen, ²Scottish Universities Environmental Research Centre
Boulders and cobbles of non-local lithologies (i.e. erratics) are found on all types of substrates in east-central southern Norway. The only exception is surfaces formed after the last deglaciation. Hence, erratics are found in superimposed on surfaces of bare bedrock, blockfield, till, glaciofluvial and glaciolacustrine material. The erratics must have been glacially transported at some point, either as isolated clasts or as till. Boulders resting on fragile substrates, such as sediments or weathered bedrock, are characteristic for areas with past cold-based, low-erosive ice sheets.

We present a preliminary synthesis of five studies that used provenance analysis of erratic boulders to reconstruct regional ice-flow direction east of the present day main water divide. The investigated mountains all have erratic material from source areas to the N and NNW. The westernmost mountains Kolla, Knutshøa and Blåhøe (Becker 2013), as well as Heidalsmuen (Tvedt 2013), also have material originating from source areas in the SW. The mountains Storsølnkletten (Eidsvåg 2013) and Tron (Hult 2011) located in the central part of the study area, and Søre Sølen (Kvamme 2012) in the eastern part, have additional boulders transported from source areas in the S-SE.

In addition, we report ¹⁰Be surface exposure ages from 36 glacially transported boulders in the study area. ¹⁰Be ages range from 7.7 ± 0.5 to 66.1 ± 1.9 ka, but cluster around 11 ka. The ages must be considered minimum ages as they are not corrected for snow cover, weathering or isostatic rebound.

References
Becker, L. 2013: Reconstruction of regional ice-flow directions in central southern Norway based on the analysis of provenance of erratic boulders. MSc thesis, Department of Earth Science, University of Bergen, 114 pp.

Eidsvåg, J.S. 2013: Glasiasjonshistorie og provenancestudier av flyttblokker frå Storsølnkletten, Alvdal, Hedmark. MSc thesis, Department of Earth Science, University of Bergen, 125 pp.

Hult, L. 2011: Rekonstruksjon av paleoisbevegelse over Tron (1666 m o.h.), Nord-Østerdalen, Hedmark, ved provenancestudie av flyttblokker. MSc thesis, Department of Earth Science, University of Bergen, 92 pp.

Kvamme, Å.D. 2012: Paleoisrørsleretningar og glasiasjonshistorie, Rendalssølen, Søraust-Noreg. MSc thesis, Department of Earth Science, University of Bergen, 228 pp.

Tvedt, M.M. 2013: Rekonstruksjon av isbevegelsesretninger basert på flyttblokker, Heidalsmuen (1745 m o.h.), Sel i Oppland. MSc thesis, Department of Earth Science, University of Bergen, 88 pp.

                       POSTER PRESENTATIONS                    

Mineralogical analysis of till by the Greenland Ice Sheet, Kangerlussuaq, West Greenland

Karin Grodzinsky¹, Eva-Lena Tullborg², Johan Hogmalm¹ and Ignasi Puigdomenech^3
1Department of Earth Sciences, University of Gothenburg, Gothenburg, Sweden, ²Terralogica AB, Gråbo, Sweden, ³Swedish Nuclear Fuel and Waste Management Company, Stockholm, Sweden
Keywords: Greenland, Kangerlussuaq, moraine, till, glacial meltwater chemistry, weathering

Till sampled from terminal moraines close to Kangerlussuaq at west Greenland are analyzed through mineralogical observations along with chemical composition data including Sr-isotopes. This study focus on the weathering processes and interaction between glacial meltwater and till. Scanning Electron Microscope, XRD and leaching experiments are, among other methods, used to study chemical weathering and reactions. For example, minerals such as pyrite and biotite show weathered edges with loss of sulfur and potassium, respectively. Some feldspars may present caved surfaces which could indicate weathering processes. Leaching experiments indicate relatively fast interaction time between water and till, and the data are compared to chemical compositions of moraine ponds and pore water samples and even deep groundwater from the same study area. These comparisons increase our understanding of the course of events and reactions for the glacial meltwater on its way from the glacier and further down the bedrock and in the watershed.

The study has been carried out as a complement to the Greenland Natural Analogue Project conducted by the Canadian Nuclear Management Organisation, the Finnish Posiva Oy and the Swedish Nuclear Fuel and Waste Management Co. (Claesson Liljedahl, L. et al. 2016). The aim of the project was to investigate how glacial conditions would affect a deep repository for spent nuclear fuel during future glacial periods.

References
Claesson Liljedahl, L. et al. 2016: The Greenland Analogue Project: Final report. SKB TR-14-13. Stockholm: Svensk Kärnbränslehantering AB.

Sedimentary characteristics of a possible tsunami deposit in the Leirfjorden area, North Norway

Louise Hansen¹, Reidulv Bøe¹, Harald Sveian¹ and Katrine Husum^2
1Geological Survey of Norway, ²Norwegian Polar Institute
A material-extraction site near Leirfjorden in North Norway reveals a composite stratigraphy of interbedded glacial and marine deposits. A coarse-grained, crudely stratified event bed is interpreted as a possible tsunami deposit. It is underlain by marine deposits reflecting reworking of glacial deposits by waves and gravitational processes after glacier retreat. The event bed is divided into four main intervals reflecting different stages of the sedimentation process. From the base upwards, these are irregular, poorly sorted sand and gravel interbedded with massive fine sand overlain by thin-bedded silt and sand with clasts. The succession of facies reflects flow processes of varied concentration alternating with suspension sedimentation of sand. Silty intraclasts and poor sorting testifies to short and episodic transportation and fast sedimentation. The bed is overlain by subtidal sediments. The sedimentological characteristics of the bed show some similarities to previously described tsunami deposits from Norway but there are also differences such as absence of biogenic material except for a few reworked foraminifers. The high elevation of the inferred tsunami deposit at c. 75 m a.s.l. precludes a relation to the Storegga tsunami and it must be older. As there is no record of an older, regional tsunami, a local event is suggested. A marine sparker survey in Leirfjorden reveals a major mass-wasting deposit that accumulated in the fjord shortly after the last deglaciation. This mass-wasting could be a likely source for a local tsunami. Failure is explained by high sedimentation rates and emergence following glacier retreat, maybe combined with seismicity.

Late Glacial and Holocene development within the source depression of the Vejrhøj end-moraine, NW Sjælland, Denmark

Peter Roll Jakobsen¹, Ole Bennike¹ and Jakob Walløe Hansen^2
1GEUS, ²UNESCO Global Geopark Odsherred
The prominent arcuate end-moraines in NW Sjælland are the backbone of the geology of Geopark Odsherred. The largest and southernmost of the end-moraines, the Vejrhøj arc, is a glaciotectonic hill-hole pair landform. The source depression makes up the innermost part of one of Europes largest reclaimed areas, the Lammefjord. It constitutes a basin that has been filled with Late Glacial and Holocene deposits. As part of a large outreach programme the basin was investigated in a drilling campaign and ground penetrating radar investigations was used in the sandy areas.

In the deepest recognized part of this basin, 25 m of sediment has been deposited. Macro fossils show that the basin initially was a Late Glacial lake, where sand and clay is deposited. The freshwater lake environment continued into the Holocene, and peat was deposited at the shores of the lake.

During the Atlantic transgression the area was flooded, and the present surface is now 3.8 m below sea level. In the initial phase of the change of environment from freshwater to marine, brackish sediments are deposited in form of laminated gyttja deposits. In this phase some of the lake deposits where redeposited. Subsequently a full marine sequence deposited in the basin as marine gyttja with numerous shells.

At the edge of the basin marine sand is deposited, and oyster banks developed at relative shallow water depth.

Lake sediment analysis of the Nedre Glomsjø outburst flood event, Southeastern Norway

Helle Daling Nannestad¹, Ivar Berthling¹ and Fredrik Høgaas^2
11Department of Geography, Norwegian University of Science and Technology, NO-7491 Trondheim, NORWAY, ²Geological Survey of Norway, Postal Box 6315 Sluppen NO-7491Trondheim, NORWAY
Sediment cores from lake and mires can provide geological archives of palaeofloods. By analysing the sediment we can better our understanding of the nature and impact of large flood events. This study aims to constrain the run-up height and timing of the outburst flood from glacial lake Nedre Glomsjø at the end of the last Ice Age. Cores from four lake basins will be examined for grain size distribution, total organic carbon (TOC) and macrofossil content. In addition to this, we aim to provide a geochemical profile (using XRF) of the floodlayer and properly constrain the event in time by radiocarbon dating macrofossils found above and below the flood sediment. Geochemical data will serve as a geomarker in order to identify the flood layer elsewhere. The probable flood layer stands out as a light, fine-grained layer in all of the retrieved cores. The upper boundary towards the organic gyttja as sharp, which signals that sedimentation stopped abruptly. Preliminary results indicate that the flood inundated basins more than 50 m above the valley floor in our study area.

Lateglacial – early Holocene geomorphology between Lake Vänern and Lake Vättern, southern Sweden

Christian Öhrling¹, Gustaf Peterson² and Mark D. Johnson^1
1Department of Earth Sciences, University of Gothenburg, Gothenburg, Sweden, ²Geological Survey of Sweden, Uppsala, Sweden
The arrival of Light Detection and Ranging derived elevation models enables efficient and accurate mapping of landforms. The region in central Sweden between Vänern and Vättern contains landforms created during two of the most important events during the late Quaternary of Sweden; the Younger Dryas cold interval and drainage of the Baltic Ice Lake.

Here, we present a 1:220 000 scale geomorphic map of this region covering approximately 18 000 km². Fifteen landform units have been mapped; end moraines, De Geer moraines, drumlinoids, crag-and-tails, hummock tracts, irregular ridges, eskers, deltas/sandurs, outwash complexes, meltwater channels, boulder bars/sheets, the Timmersdala ridge, raised shorelines, sand dunes and prominent landslide scars.

The mapped glacial geomorphology deepens the understanding of the deglacial history by the revelation of previously undetected geomorphic features and their relations, for example the abundant traces of meltwater erosion manifested as channels and hummock corridors, and previously unreported ice-marginal lines. Perhaps most striking is that all of these ice-margin positions are marked by distinct lobate moraines where they were formed above the highest shoreline.

This map provides a ‘set table’ for future research – e.g. glacier modeling, georesources, geologic history and geoheritage.

Weichselian Stratigraphy and Deglacial Deposits from Kuusivaara, Sodankylä, Central Finnish Lapland

Markus T.O. Valkama¹, Seija Kultti¹, Annika K. Åberg¹, Emilia Koivisto¹ and Veli-Pekka Salonen^1
1University of Helsinki
Central Finnish Lapland exhibits limited glacial erosion during the Weichselian. Therefore, the till units of Early and Middle Weichselian stadials are preserved in many places (eg. Helmens et al. 2007, Lunkka et al. 2015). This study describes lithostratigraphy from Kuusivaara, which is situated 140 kilometres north of Rovaniemi, east of river Kitinen. During deglaciation, the study area was first occupied by the Moskujärvi Ice Lake (207 m.a.s.l.) and later by the Ancylus Lake (186 m.a.s.l.) Stratigraphy and glacial deposits from the area were studied from six test pits and conducting fifteen kilometers of ground penetrating radar acquisition. Sediment logs were made from test sections and fourteen sediment samples were analysed for their granulometric properties. Preliminary observations suggest that weathered bedrock is covered by a probably Early Weichselian till with sandy sediments and a distinct soil horizon on their top, which may represent an interstadial deposit. The upper till is a stratified, loose sandy melt-out deposits overlain by aeolian sands, gravity flow or shoreline deposits. Stratigraphical evidence can be applied as a key to interpret landscape evolution based on LiDAR images.

References
Helmens K.F., Johansson P.W., Räsänen M., Alexanderson H. & Eskola K.O. 2007: Ice-free intervals continuing into Marine Isotope Stage 3 at Sokli in the central area of the Fennoscandian glaciations. Bulletin of the Geological Society of Finland 79, 17–39.

Lunkka J.P., Sarala P. & Gibbard P.L. 2015: The Rautuvaara section, western Finnish Lapland, revisited: new age constraints indicate a complex Scandinavian Ice Sheet history in northern Fennoscandia during the Weichselian Stage. Boreas 44, 68–80.