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Sammendrag

Opnåelse af bæredygtighed kræver indførelse i global miljøforvaltning!

v. Katherine Richardson, professor på Center for Makroøkologi, Evolution og Klima på Københavns Universitet

Behovet for lokal – og til en vis grad regional – miljøforvaltning har længe været accepteret i vores samfund. Nu er der dog en voksende erkendelse af, at der også er behov for at indføre miljøforvaltning på det globale plan. Det har vi set ifm. Montreal Protokollen, som begrænser den globale anvendelse af de kemikalier, der nedbryder ozonlaget og nu klimaet, hvor der arbejdes på en global aftale, som kan begrænse udslippet af drivhusgasser.

Imidlertid er ozonlaget og klimasystemet ikke de eneste komponenter og processer i jordsystemet, som er under pres fra menneskenes aktiviteter. Forskere indenfor Earth System Science forsøger at udvikle et redskab (”Planetary Boundaries”), som kan bruges til at identificere de af jordens processer, som er hårdt påvirket af menneskenes aktiviteter, samt at udvikle rammer for at vurdere om menneskenes pres på disse processer er på et niveau, som øger risikoen for en forandring af jorden, der vil skubbe den ud af et ”Holocene tilstand”. Status for den forskning vil blive præsenteret

Geolog med faste forbindelser

v. John K. Frederiksen, ingeniør-geolog hos Rambøll

Hovedindholdet i foredraget vil være resultaterne de næsten afsluttede forundersøgelser for den planlagte faste forbindelse til Tyskland, som foredragsholderen har haft lejlighed til at følge på nært hold fra den spæde begyndelse i starten af 1990-erne til i dag. Foruden beskrivelsen af den overordnede geologiske model, som blandt andet omfatter en saltpude midt under bæltet, vil fænomener som ‘glemsomt’ palæogent ler og snavset skrivekridt blive omtalt.

Desuden vil det blive beskrevet, hvordan en opnået dybere forståelse af, hvordan det palæogene ler under den sydlige dele af Femernforbindelsen opfører sig, førte til en  hurtigt igangsat forstærkning af funderingen af et par af strømpillerne på den gamle Lillebæltsbro.

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Stevns Klint UNESCO – Hvordan og hvad nu ? v. Tove Damholt, museumsdirektør ved Østsjællands Museum
En meget varm sommerdag i ørkenstaten Qatar i juni 2014 besluttede UNESCOs komite for verdensarv at optage Stevns Klint på den internationalt mest prestigefulde liste over natursteder. Stevns Klint står nu på listen sammen med under 200 andre steder, heriblandt Galapagos, Grand Canyon og Great Barrier Reef.

Arbejdet med at få klinten på listen er lykkedes i et tæt samarbejde mellem mange mennesker og institutioner og med en usædvanlig stor lokal indsats – så stor, at det er blevet bemærket af UNESCO, at lokalområdet havde et helt ekstraordinært kendskab til verdensarv.

Men hvad var det, som sikrede en geologisk lokalitet optagelse på den eksklusive liste? Hvorfor har lokalområdet taget det så meget til sig? Hvad kommer der til at ske nu? Og må man nu ikke længere indsamle fossiler eller andre prøver til forskning på Stevns Klint? Foredraget vi forsøge at give svar på disse spørgsmål.

Hvem ejer Nordpolen – Status for Kontinentalsokkelprojektet i det Arktiske Ocean

Christian Marcussen, Seniorrådgiver, De Nationale Geologiske Undersøgelser for Danmark og Grønland (GEUS), 2047 5964, cma [at] geus [dot] dk

Den 15. december 2014, dagen før 10 års dagen for ikrafttrædelsens af FN’s Havretskonvention (UNCLOS) for Kongeriget Danmarks vedkommende, afleverede Regeringen sammen med Grønlands Selvstyre den videnskabelig dokumentation for sit krav (“submission”) på kontinentalsokkel nord for Grønland til Kommissionen for Kontinentalsoklens Grænser (CLCS). Det drejer sig om et område på ca. 895.000 km2 uden for 200 sømil fra Grønlands kyst i det Arktiske Ocean. Denne submission er den femte indenfor Rigsfælleskabet og den er nummer 76 i en lang række submissioner fra alle dele af kloden (http://www.un.org/depts/los/clcs_new/commission_submissions.htm ).

Dataindsamlingen i Polhavet, der har dannet grundlag for det videnskabelige datamateriale der er indeholdt i submissionen, er foregået i tidsrummet mellem 2006 og 2012 inden for Rigsfælleskabets Kontinentalsokkelprojekt (www.a76.dk). At indsamle data i dette isdækkede område, som er foregået både fra havisen, fra luften og med isbryder, er en stor udfordring og er kun lykkedes på grund af en fornem holdindsats og et godt samarbejde med andre lande.

Efter afleveringen af submissionen vil der gå en rum tid før denne submission bliver behandlet af CLCS, mens den russiske resubmission, der forventes indsendt i løbet af kort tid, bliver behandlet i de kommende år. Norge har fået CLCS anbefaling mht. et mindre område nord for Svalbard, mens Canada har påbegyndt en fornyet dataindsamling og USA endnu ikke har ratificeret UNCLOS.

Dataindsamling i Polhavet har givet de involverede institutioner et unikt erfaringsgrundlag, der forhåbentligt også kan udnyttes fremover i dette svært tilgængelige område.
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Geology at nanoscale: What do CO2 storage, ground water quality, enhanced oil production and coccolith formation have in common?

v. Susan Stipp, professor ved Kemisk Institut, Københavns Universitet og leder af NanoGeoScience Research SectionThe processes that build mountains and wash them to the sea, that clean up pollution and that create oyster shells are all driven by the same molecular scale reactions. Interactions between fluids, such as water, oil and  CO2, and the minerals in rocks and soils control them all.

We use nanotechniques, to “see” these interactions in real time. We learn the secrets of nature and apply the new knowledge to solve some of society’s challenges, such as cleaner water, safer storage of waste, converting CO2 to minerals that are stable for geologic time, squeezing more oil from depleted reservoirs and designing biomimetic materials.
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Vandrammedirektivet – en udfordring både for geologer og dansk landbrug

v. Flemming Gertz, Landskonsulent, Planter & Miljø i SEGES P/S

Vandrammedirektivet blev i 2000 vedtaget af EU kommissionen med det overordnede formål at fastlægge en ramme for beskyttelse af vandløb og søer, overgangsvande, kystvande og grundvand.

Implementeringen af direktivet er en kæmpe udfordring for alle medlemslande, fordi direktivet opstiller meget ambitiøse mål. Direktivet giver muligheder for at anvende en række forskellige undtagelser, men som udgangspunkt skal de biologiske kvalitetselementer, som anvendes for at bedømme tilstanden i et vandområde, udvise niveauer, der kun er svagt ændret som følge af menneskelig aktivitet, og kun afviger lidt fra, hvad der normalt gælder under uberørte forhold. Det siger næsten sig selv, at for et land som Danmark, giver det nogle særlige udfordringer, da uberørt natur i Danmark dækker en forsvindende lille del af landet.

Vandrammedirektivet bryder med flere danske vandforvaltningstraditioner. Væsentligt er det, at målene defi-neres ved biologiske ”kvalitetselementer” (plankton, fisk, planter mv) og fastsættes for det specifikke vand-område. Det bryder med den danske tradition i Vandmiljøplanerne, hvor målet om 50% N reduktion og 80% P reduktion mere eller mindre blev politisk fastsat med håbet om, at vandmiljøet ville ende i en tilfredsstillen-de tilstand. Direktivet bryder også med en anden stærk dansk tradition. Traditionen med top-down regulering.

Et af direktivets grundpiller er den aktive involvering af borgere. Det beskrives i direktivets artikel 14 stk1: ”Medlemsstaterne tilskynder til, at alle interesserede parter inddrages aktivt i gennemførelsen af dette direktiv, navnlig i udarbejdelse, revision og ajourføring af vandområdeplanerne”. Netop dette punkt om ind-dragelse var fra dansk side næsten komplet fraværende i 1. generation vandplaner, og har været helt afgø-rende for at 1. generation vandplaner blev sendt til kommissionen i efteråret 2014 med næsten 5 års forsinkelse.

Sammen med den manglende inddragelse skyldes problemerne grundlæggende de ambitiøse mål i vandplanerne om god tilstand (dvs kun svag afvigelse fra uberørte forhold) i stort set alle danske vandløb, søer og fjorde. Det er selvsagt meget svært at opnå. Især er landbrugserhvervet blevet udfordret på flere punkter. Hvad angår udledningen af kvælstof var den i 2012, ifølge Naturstyrelsen, på 56.900 ton og udled-ningen til vandmiljøet skal frem til 2021 reduceres til 40.600 ton.

Da naturbidraget af gode grunde ikke kan reduceres betyder det, at landbrugets tab af kvælstof til vandmiljøet skal reduceres med 46 pct frem til 2021. Med den nuværende betydelige lovpligtige undergødskning i dansk landbrug vil dette mål ikke kunne opnås med de virkemidler vi kender i dag uden store negative konsekvenser for landbruget. En opgørelse af landbrugets drænvandsundersøgelse 2011-2014 på i alt 700 lokaliteter og 3500 enkeltmålinger viser et gennemsnit af de sidste tre års målinger på 7,5 mg total-kvælstof pr. liter. (og ca. 5,5 mg nitrat-N).

Drænvandsundersøgelen viser, at der er meget stor variation mellem koncentrationen i de enkelte dræn. Således var koncentrationen i 20 pct. af drænene under 3,9 mg totalkvælstof pr. liter, og koncentrationen var i 20 pct. af drænene over 10,3 mg pr. liter. Det viser, at eventuelle tiltag til reduktion af kvælstofudledningen skal rettes mod dræn med høje koncentrationer og stor afstrømning. Dette kræver ny og detaljeret viden om nitrats transportveje gennem grundvand, dræn, ådale mv.

Ikke kun store krav til N-reduktion udfordrer landbruget. Også landbrugets afvanding af marker via dræn og vandløb er udfordret af målene i danske vandplaner. Helt op mod 90% af de danske vandløb er uddybede og/eller udrettede i større eller minde grad som følge af behovet for effektiv afvanding. Til trods for de åbenlyst fysisk ændrede betingelser er målene fortsat god økologisk tilstand i 19.000 km vandløbsstrækning.

En nødvendig analyse af vandløbenes hydromorfologiske karakteristika er ikke foretaget, og med baggrund i kun biologiske vandløbsbedømmelser er staten fortsat på vildspor, hvad angår at få målsætning og realiteter til at hænge sammen.

I de kystnære områder er ålegræs et af de biologiske kvalitetselementer som har stor betydning for miljøtil-standen. Den traditionelle biologiske tilgang har været, at tillægge lystilgængeligheden afgørende betydning for ålegræsset udbredelse. Dette er for så vidt rigtigt hvad angår dets maximale dybdegrænse. Men hvad angår udbredelse i lavvandede fjorde er de fysiske og morfologiske betingelser af endnu større betydning. Mudrede sedimenter uden forankringsevne, sandflugt og bølgepåvirkning er nogle af de afgørende parametre som forhindrer ålegræsset i at brede sig, og generobre tabte habitater. Endnu er dette ikke anerkendt og medtaget i vandplanerne.

Til trods for, at det i sidste ende er de biologiske kvalitetselementer som afgør om et vandområde er i god tilstand, så er det muligt at fare vild, hvis ikke den grundlæggende områdeforståelse er til stede. Samlet tegner der sig et billede af, at der i den danske forvaltning af Vandrammedirektivet ikke lægges tilstrækkelig vægt på at beskrive og forstå de grundlæggende geologiske, morfologiske og fysiske karakteristika.

Hydraulic Fracturing – Unlocking Danish North Sea Chalks

v. Michael Mulrooney, senior stimulationsingeniør ved Mærsk Olie og Gas

In all but one Danish North Sea field operated by Maersk Oil, carbonate reservoirs consisting of chalks and limestones have been successfully produced since the early 1970’s and drove the global evolution of horizontal wells and well stimulation techniques in the 1980’s, 90’s and into the 2000’s.

This evolution has seen a variety of well architecture and stimulation techniques deployed on various fields, resulting in the economic production of Danish North Sea Chalks that were previously thought to be too challenging and marginal to sustain meaningful oil and gas production.

Some of the first economic production from Danish chalk reservoirs came from drilling long horizontal wells through the producing intervals.  Long wells have not proven to be enough however, and this has posed a challenge to engineers and geologists to understand the producing reservoirs, and how these reservoirs’ production can be stimulated to economic levels.

This talk will give a brief understanding of the reservoir types and inherent production challenges, as well as an overview of the stimulation techniques employed.  Focusing mainly on Hydraulic Fracturing stimulation techniques including Acid Fracturing and Proppant fracturing, we will discuss what fracturing is, where and why it is deployed, and more importantly, what it is not.

Though technically complicated as an entire process, incorporating geology, geomechanics, reservoir engineering, chemistry, hydraulics, surface equipment operations, the general principles can be explained quite easily.  This talk will attempt to come to a balance between technical and general.

As the Danish oil fields age, and new target reservoirs become more and more marginal, new, faster and more economical fracturing methods are needed.  An overview of where we started and where we are moving with respect to technology and methods will be discussed.

Hydraulic fracturing or “Fracking” has had a global history of over 100 years, and was introduced in Denmark both onshore and offshore as early as the 1960’s, but began to become commonplace offshore in the 1990’s.  Recent increases in onshore shale-gas fracturing activity in the USA and in Continental Europe have increased visibility of the environmental impact of not only fracturing, but oil and gas drilling in general.

This talk will touch on the cooperation that operators such as Maersk Oil have had and continue to have with the Danish Energy Agency (DEA) ant the Danish Environmental Protection Agency (DEPA) to regulate the drilling and completion process, chemical usage, and discharge of produced fluids.  A brief introduction to the chemicals used, and the regulatory processes in place will be given.
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Jordskælvet i L’Aquila 2009 – Seks italienske videnskabsfolk og en administrator dømt til 6 års fængsel for drab

v. Trine Dahl-Jensen, seniorforsker på GEUS

Early Monday morning, April 6 2009, central Italy was struck by a 6.3 magnitude earthquake. The 2009 L’Aquila earthquake caused serious damage to several medieval hill towns in the region, killing over 309 residents, injuring over 1,000 and leaving 28,000 homeless.

The earthquake occurred after a period of smaller earthquakes – a swarm – causing concern in the population. A meeting with members of the Italian Major Hazards Commission was convened in L’Aquila to access the situation, and one member, Department of Civil Protection vice-president Bernardo De Bernardinis, who is not a seismologist nor a member of the Major Hazards Commission, said following the meeting:
“The scientific community tells us there is no danger, because there is an ongoing discharge of energy. The situation looks favourable.”

This statement is not scientifically correct. A few days later the main shock occurred. Nearly everyone in L’Aquila, including the prosecutor, lost relatives or friends.

De Bernadinis and six scientists were indicted for manslaughter. They were charged with conducting a risk assessment that was “generic and ineffective”, providing civil authorities and the public with “incomplete, imprecise, and contradictory information about the nature, causes, and future developments of the seismic hazards”, and characterizing the seismic swarm that affected L’Aquila for about three months before the main shock as “a normal geological phenomenon”.

Monday 22 October 2012 the 7 were sentenced to 6 years in prison each. The case was appealed, and in November 2014 the six scientists were acquitted, while De Bernadinis was sentenced to two years in jail.
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Postersammendrag

Auriferous gold deposits explained through principal component analysis in South Greenland

Sven Helbig [svhe [at] geus [dot] dk], Geological Survey of Denmark and Greenland; Øster Voldgade 10, DK-1350 Copenhagen K, Denmark

The Nalunaq gold mine is located on the Nanortalik peninsula, which comprises of rocks formed during the Ketilidian orogen in South Greenland. The Ketilidian orogen took place in the Paleoproterozoic from ca. 1850 Ma to 1725 Ma. In 2004, the Nalunaq gold mine opened and produced over 7 tons of gold until its closure at the end of 2013.

The hydrothermal gold deposit is characterized by a quartz vein with a thickness between 0.5 and 2.0 m with an average dip of 35o towards the south east. The quartz vein contains gold grades of up to 40 g/t. The host rock surrounding the auriferous quartz vein (main vein) is a fine- to coarse- grained homogeneous meta-basalt and consists of hornblende, plagioclase, quartz, minor biotite and clinopyroxene. It was metamorphosed under amphibolite facies conditions predating the hydrothermal alteration surrounding the main vein.

The aim of the project is to determine if principal component analysis (PCA) is a viable method for the analysis of auriferous gold deposits. The answer to this is yes. Two approaches were applied in this thesis, an analysis of the trace elements and major elements. The major elemental analysis revealed that a quartz vein can be identified directly or within a measuring error of about 90 m. The trace elemental analysis revealed to be more accurate in the determination of gold vein deposits. The measuring error with trace elements is at about 4 m.

The difference between the major elements and the trace elements is that the major elements can be used on a larger scale to determine in which general area a gold bearing quartz vein may be located. Trace elements only describe a narrow area (in this case about 50 m) of mineralization. In both cases the stronger the signal of the gold is the more precise PCA is in determining the location of the gold bearing quartz vein.

PCA was used to identify groupings of gold content, which reflect hydrothermal alteration halos surrounding the main vein. These groupings correlate with elements in specific ways that show how the host rock was influenced and changed geochemically during the introduction of the main vein. Through this approach it was possible to determine that the main vein has been thrusted towards the west in a reverse fault setting.
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Stratigraphic architecture of Devonian lacustrine basins of Northern Scotland

Thorben Kristiansen1 [thorbenk87 [at] gmail [dot] com], Julien Moreau1, Steven Andrews2 and Stuart Archer2
1: Department of Geosciences and Natural Resource Management, Copenhagen University
2: University of Aberdeen
In Northeastern Scotland, the Orcadian Basin hosted large lacustrine systems which developed during Devonian times (c. 400 Ma). The pre-Devonian metamorphic basement unconformity is only exposed in a small number of places around the basin margin and therefore the characterization of the nature of this important surface has received relatively little attention. We have utilized vintage onshore seismic to gain a better understanding of the pre-Devonian basement physiography. Onshore exposures of the top Moine, base Devonian unconformity surface is exposed and have been visited to ground truth our subsurface interpretations.

The studied deposits have been deeply buried then exhumed so that they are exposed widely onshore. Post Caledonian tectonism has faulted and folded the Devonian succession making it challenging to reconstruct the stratigraphy and the basin architecture from geological data only. The Devonian sediments were deposited in a continental environment and fluvial and alluvial deposits are interbedded with lacustrine units. These lacustrine facies contain fishbeds which are organic rich mudstones with moderate source potential. Variations in burial history have resulted in variations in the source rock maturity of the fishbeds.

A large dataset of 2D seismic reflection profiles are available from across the study area. The dataset is of mid 80’s vintage and covers the Caithness and the Ross and Cromarty areas (NE Scotland). The survey consists of 33 profiles making up 416,92 km of data on an area of 140 X 40 km. The vintage data have limited horizontal and vertical resolutions. To enhance the images, we have used a dip-steering median filter. To depth convert the horizons, stacking velocity analysis has been performed. In parallel, newly acquired field data are used to correlate with the seismic profiles. Correlations made to deep borehole data (Tain-1 well) have allowed marker beds to be attributed to specific seismic reflections. Finally, gravimetric data are used to calculate the depth to basement.

The main focus of this work is to fully interpret the seismic architecture of the Devonian basins by integrating seismic and potential fields based depth to basement mapping techniques. Within the basin fill specific stratigraphic horizons and structural domains have been mapped. Seismic velocity analysishas contributed to the production of the basin maps. Understanding the stratigraphic architecture of the basin will bridge the gap between onshore field data and offshore North Sea wells and seismic. We expect to provide new insights into the North Sea’s geological history, as well as a better understanding of the offshore Devonian hydrocarbon play.
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Hydrothermal vents and sand injectites of Lower Cretaceous, southern North Sea. Consequence of transform tectonics induced magmatism?

Luka Blažić*1 and Julien Moreau1,
1 Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, 1350 Copenhagen
*luka [dot] blazic [dot] geol [at] gmail [dot] com

Within the Jurassic Broad Forteen Basin (North Sea), 31 vents built of 58 smaller structures have recently been recognized within a seismic cube thanks to seismic attribute analysis. Strong amplitude anomalies present within the salt are good indication of the presence of igneous intrusions. Near the surveyed volume, well cuttings from Zeichstein salt structures contain nephelinic basalts dating of 100 Ma. The vents are imaged as sub-transparent agglomeration of sub-vertical pipe structures emanating above the seismic amplitude anomalies.

The vents were analyzed through distinct categories: size, shape, upper part shape and source bed. Most of the vents originate from the Lower Germanic Triassic Group (Bundsandstein). They are conical in shape and have an eye-shaped upper dome. At the top, numerous domes have been eroded. A few domes have jacked up the overburden, sometimes including lateral intrusion (sandstone sill). Almost all vents terminate at the Upper Jurassic/Lower Cretaceous unconformity. Based on the relationship with the overlaying deposits, we have constrained the time span of venting to be from pre- Mid Hauterivian times (eroded/partly eroded upper parts of the vents, onlaps on the vents) to Albian times for the latest (bended reflections, igneous intrusion dating from well cutting).

Vents formation and subsequent fluidized sandstone injection and expulsion are interesting from petroleum exploration perspective. Most of the vents punctured through basins primary source rock – the Posidonia shales. The breaching most probably created new pathways for fluid migration, connecting the source with the overlaying sandstone units with sand injectites/fracturation around the pipes. Sand injections in the vents could serve as both migration route and reservoir units, under the condition that fluids did not conceal the pore-space. The occurrence of hydrothermal activity could also create sweet spots where good maturity occurs at shallow depth because of the associated localized heat-flow. In this new play, the seal is similar to the traditional one in the basin, the Vieland Claystone Fm, which drape and onlap on hydrothermal vents domes creating a stratigraphic trap. Preservation of these traps is observed today, unlike conventional traps in the basin where majority was destroyed during inversion in Late Cretaceous.

In addition, this discovery illustrates the complexity of transfer of fluids and solids associated with igneous intrusions within sedimentary basins. The zone was not considered particularly volcanic except for the isolated Zuidwal volcano situated onshore (50 km East and older). The formation of these vents coincide with the end of subearial exposure in the basin during the main syn-rift phase. Besides the economic impact of this discovery, one could ask what is the trigger of this activity? Was it so discreet in the seismic images that it is more widespread than thought in the basin? One possible process behind the focusing of igneous intrusions is the extensional movement of the crustal-scale faults  bounding the rift system. Between the Late Jurassic and the Early Cretaceous, faults of the Broad Fourteens Basin, the Sole Pit Basin to the West, the Sudetic Basin to the East, are being reactivated in a dextral transtensive motion. If such focusing mechanism exists, volcanic activity of Early Cretaceous age and associated hydrothermal venting with sandstone intrusions is not restricted to the Broad Fourteen Basin and could be expected along the Late Jurassic/Early Cretaceous transform zone of the North Sea.
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Orbital calibration of the Late Campanian carbon isotope event in the North Sea

Anastasios Perdiou, Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, 1350 Copenhagen

A new record of carbon isotopes, calcareous nannofossil biostratigraphy, gamma-ray and Fe content variations is presented for the Late Campanian of the Adda-3 core, Danish central Graben, North Sea. The studied interval was previously assigned a late Coniacian to early Santonian age. Biostratigraphy actually indicates a late Campanian age for the 60 m long studied interval.

The Late Campanian Event (LCE) is well-recorded by a 2‰ negative excursion in the bulk δ13C. Correlation of the δ13C curve of Adda-3 to similar records from North Germany, UK, and Tercis (France) shows that the amplitude of the LCE is higher in the North Sea than in other areas. This correlation also allows identification of a new 0.4‰ negative excursion (defined as the conica event). Fe and gamma-ray variations are used to calibrate the record with cyclostratigraphy.

Fourteen 405 kyr eccentricity cycles are identified in the late Campanian of Adda-3 and correlated to North Germany. The compilation of previous results from North Germany and correlation to Adda-3 shows that the Boreal Late Campanian comprises a total of seventeen 405 cycles and accounts for a total duration of 6.885 Myr while the duration of the LCE in the North Sea is of 1.6 Myr.

Abundance and size changes in the calcareous nannofossil Schizosphaerella – relation to pCO2 and the carbonate factory of the Early Jurassic

Leonie Schäfer and Nicolas Thibault, Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, 1350 Copenhagen.

Schizosphaerella spp., a probable fossil calcareous dinoflagellate, was the main pelagic carbonate producer of the Early Jurassic. A major drop in abundance and in the mean size of this group during the early Toarcian Oceanic Anoxic Event (T-OAE) has been previously interpreted as a calcification crisis in response to increased pCO2, increased nutrient availability and greenhouse warming (Suan et al., 2008). The behavior of this taxon has however never been documented so far prior to the interval that spans the extreme environmental change of the T-OAE. Such studies are necessary in order to better constrain the palaeoecology of this group and its contribution to pelagic carbonate sedimentation.

This study focuses on changes in abundance and mean size of Schizosphaerella throughout the Sinemurian-Pliensbachian (ca. 199 to 183 Ma) and on its potential contribution to the overall carbonate factory in the Sancerre core (Paris Basin). The abundance of Schizosphaerella shows a marked increase coincident with a rise in sea-level and a major change in facies in the Oxynotum Ammonite Zone.

During the late Sinemurian, the abundance of coccoliths is very low, Schizosphaerella dominates the calcareous nannofossil assemblage and is characterized by a relatively large size. A sharp drop in the mean size of Schizosphaerella occurs in the Early Pliensbachian (Early Carixian) and precedes a decrease in absolute and relative abundance of the group in the late early Pliensbachian (Late Carixian). The absolute abundance of Schizosphaerella increases again and reaches maxima during the Margaritatus Ammonite Zone (Late Pliensbachian), preceding a gradual size increase. Another decrease in Schizosphaerella abundance is recorded during the Spinatum Ammonite Zone, preceding a major drop in size at the Pliensbachian-Toarcian-Boundary.

Our results demonstrate that there is no direct correlation between the abundance and size of Schizosphaerella. Mixture analysis of our biometric data highlight the presence of two distinct populations, suggesting two different species with distinct paleoecological affinities whose changes in relative abundance are responsible for the observed variations in mean size.

During the Sinemurian and Pliensbachian, the carbonate production by Schizosphaerella (CaCO3Schizo) accounts for up to 12% of the total carbonate fraction. The total CaCO3 content and the CaCO3Schizo show similar long-term trends from the Late Sinemurian to the Early Toarcian that may have been controlled by changes in pCO2.

These findings demonstrate that by the Late Sinemurian, calcareous nannofossils influenced the total pelagic CaCO3 production and CaCO3 deposition in the Basin over long time-scales. However, there is no direct correlation between the two signals and over short time-scales, there is a decoupling of these two proxies, suggesting that high-frequency changes in carbonate deposition were rather controlled by the transport of carbonate particles from shelf areas than by in situ production.

Volatile (S and Cl) and major element variations in olivine hosted melt inclusions from the backarc volcanic province, Payéna, of the Andes Southern Volcanic Zone (SVZ)

Brandt, F.E*1, Holm, P.M1, Hansteen, T, 2
1Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, Copenahagen 1350, Denmark (*correspondence : feb [at] ign [dot] ku [dot] dk).
2GEOMAR Helmholtz-Zentrum für Ozeanforschung, 24148 Kiel, Germany

We precent volatile (sulfur and chlorine) and major element contents in olivine hosted melt inclusions from 13 mafic tephras sampled along the Quaternary backarc volcanic province, Payénia, of the Andes Transitional to Northern Southern Volcanic Zone (T–NSVZ; 33˚S–38˚S). Pre-eruptive S and Cl contents extend to higher K2O concentrations in olivine hosted melt inclusions from the backarc, than observed for arc related olivine hosted melt inclusions of the T–NSVZ, reflecting lower degrees of mantle melting in the backarc.

In turn, Cl/K2O and S/K2O ratios increase northwards along the backarc, reflecting an inreased fluid-derived signal by subduction of altered oceanic crust. Post-entrapment olivine crystallisation corrected Cl/K2O and S/K2O ratios define positive correlations with host olivine fosterite content (Fo89–80) that cannot be explained by olivine fractionation, degassing and/or degree of mantle source melting. The correlation is instead evidence of source differences in the content of Cl, K2O, S and their ratios, but also Mg#. The differently enriched mantle sources feeding the backarc volcanism are not only chemically different but also mineralogically. This is evident in correlations between Mn/Fe in the host olivine and Cl/K2O, S/K2O and Mn/Fe ratios in the melt inclusions.

The age of extension-related lamprophyres in the Western Province of New-Zealand and their relevance to Gondwana break-up and pre-Alpine deformation

Quinten H.A. Van der Meera, Michael Storey 2 and Tod E. Waight a1

1 Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, 1350 Copenhagen K, Denmark.
2 QUADLAB, Department of Environmental, Social and Spatial Change, Roskilde University, Universitetsvej 1, DK-4000 Roskilde, Denmark.

Step heating 40Ar/39Ar amphibole and biotite ages ranging between 92 and 70 Ma are presented for eight lamprophyric dikes from the Westland region of the South Island of New Zealand. Based on dike orientations and cross-cutting relationships these dikes have previously been related to extensional tectonics preceding and during opening of the Tasman Sea. Detailed analysis of step-heating profiles reveals common evidence for low-temperature Ar loss and the presence of excess 40Ar, in part explaining variability and inconsistencies in older (bulk mineral and bulk rock) K/Ar studies.

The new ages, in combination with previously published reliable ages from Westland, provide evidence for two pulses of late Cretaceous mafic magmatism. The first episode occurred between 92 and 81 Ma during a period dominated by crustal extension between cessation of subduction-related activity and the first appearance of oceanic crust in the Tasman Sea. This activity appears to young southwards. A second period of mafic volcanism is identified at 72 – 68 Ma and is concentrated to the south of the Hohonu Ranges. It is suggested that this late Cretaceous activity may be potentially related to transtensional shearing, oroclinal bending, crustal heating and deformation of Zealandia at 72-68 Ma.
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Chemographic modelling of secondary zirconosilicates: Implications on late-stage fluid evolution in agpaitic nepheline syenites of the Ilímaussaq Complex, South Greenland

Anouk Borst 1,2*, Henrik Friis 3, Tom Andersen 4, Troels Nielsen 1, Tod Waight 2 (*amb [at] geus [dot] dk)
1) Department of Petrology and Economic Geology, GEUS, Øster Voldgade 10, Copenhagen 1350, Denmark
2) Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, Copenhagen 1350, Denmark
3) Natural History Museum, University of Oslo, Sarsgate 1, N-0562, Norway
4) Department of Geosciences, University of Oslo, P.O. Box 1047 Blindern, N-0316, Norway

The peralkaline Ilímaussaq Complex (~1.16 Ga) is well-known for its great mineralogical diversity and multi-element resource potential. The intrusion is largely composed of agpaitic nepheline syenites, which contain complex Na-Zr-Ti silicates such as eudialyte and rinkite, instead of common HFSE-phases like zircon and ilmenite. Voluminous accumulations of magmatic eudialyte in the layered syenites in the lower part of the magma chamber provide economically exploitable concentrations of Zr, Nb, and REE. The mineralisation, however, is affected by wide-spread autometasomatic alteration of cumulus eudialyte, which led to the formation of complex pseudomorphic aggregates of secondary Na, Fe, Zr, REE and Nb phases.

Detailed petrographic studies reveal three types of eudialyte alteration assemblages, dominated by the zirconosilicates catapleiite (Na2ZrSi3O9•H2O), zircon and gittinsite (CaZrSi2O7). Gittinsite, previously unidentified from Ilímaussaq, is a rare mineral mostly found in Ca-metasomatised peralkaline granites. Its occurrence in highly sodic and Ca-depleted syenites such as Ilímaussaq is unusual.

To evaluate the relative stability of the various zirconosilicates as a function of changes in the chemical components of the melts and fluids (alkalinity, H2O and CaO activity), we constructed a theoretical 3D chemographic grid model using the principles of Schreinemakers analysis. The calculations are based on the observed mineral assemblages and compositions, assuming constant P and T.

The diagrams confirm previous models of catapleiite-formation by a general increase in water activity, which can be related to the exsolution of Na, Cl and F-rich aqueous fluids at the final stages of crystallisation. The spatially restricted formation of gittinsite requires the influx of an externally derived Ca-Sr-rich fluid at the post-magmatic stage. Zircon-bearing alterations are restricted to more heavily altered kakortokites and associated pegmatites, and require a general decrease in alkalinity and water activities.

Mass balance calculations for the observed eudialyte alteration assemblages additionally suggest that the autometasomatic alteration was not associated with significant remobilisation of Zr, Nb and REE. We infer that the immobile behavior of HFSE and REE during the wide-spread fluid-rock reactions can be attributed to the overall high pH of the late-magmatic fluids, which, despite high concentrations of transporting ligands Cl and F, prevents stable complexation of REE and HFSE with fluoride and chloride compounds.
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Chronicles recorded in grains of sand: The genesis of Bunter Sandstone Formation

Mette Olivarius, Geological Survey of Denmark and Greenland (GEUS) & Aarhus University (AU)

Invaluable information of the geological past is stored in sand grains. Their formation age may reveal their provenance. Their shape is a result of composition, weathering and abrasion. Their mineralogical assemblage is related to source rock, depositional environment and climatic conditions. Their diagenetic alteration is associated with detrital composition, burial depth and pore water chemistry.

Sand grains in the Bunter Sandstone Formation have been used to identify source areas and diagenetic history. The formation contains two primary sand intervals named the lower and upper Bunter sand. These red beds were deposited in the North German Basin during the Early Triassic. They were sampled in well cores from southern Denmark where they are present at depths of 1–2 km.

The lower Bunter sand has a mature mineralogical composition indicative of a long source-to-sink distance. Zircon ages show that most of the sand was transported across the North German Basin from the Variscan belt in Czech Republic and southeastern Germany to the Danish area. The basin area was a desert at the time, and the lower Bunter sand was deposited as aeolian sand sheets. The high degree of sorting and the low clay content are related to the depositional environment. Thick red coatings were formed due to the arid climatic conditions. A combination of all these factors made the sand stay loose to weakly cemented during burial.

The upper Bunter sand has a uniform, unique and immature heavy mineral assemblage indicative of a local provenance. Zircon ages show that the Ringkøbing-Fyn High is the primary source area. The sand was deposited by ephemeral fluvial channels due to the semi-arid climatic conditions. The more pronounced mechanical compaction than in the lower Bunter sand is related to ductile grains and infiltration clays. The diagenetic alterations include pervasive cementation in some intervals.

Palæoøkologisk rekonstruktion af Skandinavien gennem Furongien (Øvre Kambrium)

Bo Wilhelm Rasmussen, Statens Naturvidenskabelige Museum, Øster Voldgade 5, 1350 Kbh K.
Alunskifferen i Skandinavien har været et interessant emne for geologer/palæontologer siden 1800 tallet. I dette projekt er alunskifferen aflejret i den sydlige del af Skandinavien i Øvre Kambrium (Furongien) 495–488 Ma og kan genfindes i Sverige, Norge og på Bornholm. Den kambriske mudderhavbund havde en utrolig langsom sedimentationsrate (få mm/1000 år) og ophold i aflejring af skifferen gav anledning til udfældning af kalk (antrakonit). I kalkkonkretioner og kalklag genfindes utallige trilobitter. Ved identificering af arterne og indsigt af deres anatomiske og fysiologiske funktioner opnås en forståelse af et relativt hav- og oxygenniveau. Materiale bliver indsamlet/behandlet fra flere lokaliteter og resulterer i et palæoøkologisk billede af Skandinavien gennem Furongien.