Geologisk Tidsskrift 1999

Indhold af hæfte 1

Tidlig ordovicisk palæogeografi bestemt udfra palæooceanografiske modelleringer kombineret med palæobiogeografiske data

Christiansen, Jørgen Løye: Tidlig ordovicisk palæogeografi bestemt udfra palæooceanografiske modelleringer kombineret med palæobiogeografiske data. Geologisk Tidsskrift, hæfte 1, pp. 1–7, København, 1999–04–29.

Abstract: Palaeogeographic reconstructions are normally based on palaeomagnetic, palaeobiogeographic and palaeolithological data. Palaeooceanographic models however can, when combined with palaeobiogeographic data, be used as an essential constraining element in the palaeogeographic reconstructions. In this paper this approach has been taken with the Arenigian (Early Ordovician) as an
example and a new palaeogeographic reconstruction for the Arenigian has been composed.
Adresse: Jørgen Løye Christiansen, Institut for Geografi og Internationale Udviklingsstudier, Hus. 19.2., Roskilde Universitetscenter, Postboks 260, 4000 Roskilde.

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Sr/Ca variationer i Orthoceratitkalken (Nedre Ordovicium): Evidens for havniveauændringer

Feilberg, F.: Sr/Ca variationer i Orthoceratitkalken (Nedre Ordovicium): Evidens for havniveau ændringer. Geologisk Tidsskrift. hæfte 1, pp. 8–12, København 1999–04–29.

Abstract: Sea-level variations in the Lower Ordovician ‘Orthoceras Limestone’ on the Baltic platform have previously been estimated on the basis of sedimentological and palaeontological data. This paper provides evidence for a correlation between the carbonate chemistry (Sr/Ca ratio) and these sea-level variations. During a transgression, the inner platform settings provide a significant carbonate production which serves as a sink for Ca relative to Sr. The Sr/Ca ratio in the ocean will therefore increase during the transgression. During regressive
conditions, the opposite situation occurs, and the Sr/Ca ratio will be lowered in the ocean. The abiotic marine cement is in equilibrium with the ambient sea water and fluctuations in the Sr/Ca (sea water) will be traced in the carbonate geochemistry. The assumption is based on a Lower Palaeozoic ‘calcite sea’ and not on the modern ‘aragonite sea’.
This model has been tested at Horns Udde, northern Öland, Sweden.The samples were collected bed by bed from the Microzarkodina sp. A to the Baltoniodus norrlandicus Zone (Latorp–Volkhov Stage), and the Sr/Ca data were obtained by atomic absorption spectrophotometry. The sea-level curve based on the Sr/Ca data and a sea-level curve constructed from conodont biofacies analysis are synchronous. The strong relationship between these models provides additional support for the Sr/Ca model. Furthermore the d18O ratio was used to predict original/diagenetic remobilised signals.

Adresse: Flemming Feilberg, Geologisk Institut, Afdeling for Historisk Geologi og Palæontologi, Øster Voldgade 10, 1350 København K. Nuværende adresse: Poppelhegnet 20, 2800 Lyngby.

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En palynologisk undersøgelse af kretassiske og paleocæne
sedimenter fra det sydøstlige Nuussuaq, Vestgrønland

Jakob Lanstorp: En palynologisk undersøgelse af kretassiske og paleocæne sedimenter fra det sydøstlige Nuussuaq, Vestgrønland. Geologisk Tidsskrift, hæfte 1, pp. 13–20. København, 1999–04–29.

Abstract: The Cretaceous and Paleocene sediments from the West Greenland Basin onshore the southeast Nuussuaq peninsula, represent fluviodeltaic and prodeltaicmarine deposits. From the strata of Ataa, Paatuut, Atanikerluk and Tartunaq, southeast Nuussuaq, eight sections were investigated for their microfloral content and 61 genera and 107 species of microspores and pollen were recovered. No
dinoflagellate cysts or other marine microfossils have been recovered. Palynological analyses of 39 samples permit the recognition of 3 diagnostic biostratigraphic assemblage-zones and 2 subzones, the age of which have been estimated by comparison with palynofloras from North America and Europe. The Alnipollenites versus Assemblage-Zone (A), from the very top of the Paatuut, and a Tartunaq section, is of Early Paleocene age. The Pilosisporites sp. A –Hazaria sheopiarii Assemblage-Zone (PH), from Ataa and Paatuut is of Late Santonian – Early Campanian age, possibly the transition Santonian/Campanian. Rugubivesiculites rugosus – Retitricolpites georgensis Assemblage-Zone (RR) is divided into a Tricolporopollenites Subzone (RRT) from Atanikerluk of Early Cenomanian age and a Cycadopites Subzone (RRC) from Tartunaq of Middle-Late Albian age.

Adresse: Jakob Lanstorp, Geologisk Institut, Afdelingen for Palæontologi og Stratigrafi, C.F.Møllers Allé 120, 8000 Aarhus C. Nuværende adresse: Ravnsborggade 13,, 2200 København N. E-mail: lanstorp [at] hotmail [dot] com

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Ella Hoch: Anmeldelse af: Nils Møller Andersen: Water striders from the Paleogene of Denmark with a review of the fossil record and evolution of semiaquatic bugs (Hemiptera, Gerromorpha). Det Kongelige Danske Videnskabernes Selskab. Biologiske Skrifter 50. 1998. 140 sider, 8 tavler. Kommissionær: C.A. Reitzels Boghandel (fra 1. januar 1999), København. Pris 250 kr. – Geologisk Tidsskrift, hæfte 1, pp. 21–24. København, 1999–04–29.

Adresse: Ella Hoch, Geologisk Museum, Københavns Universitet, Øster Voldgade 5–7, 1350 København K

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Foreningens meddelser

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Indhold af hæfte 2


Geotekniske problemer

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Stratigrafisk korrelation af øvre karbone (Moscov) miosporer fra Kap Jungersen, Amdrup Land, det østlige Nordgrønland

Thomsen, C.: Stratigrafisk korrelation af øvre karbone (Moscov) miosporer fra Kap Jungersen, Amdrup Land, det østlige Nordgrønland. Geologisk Tidsskrift, hæfte 2, pp. 7- 1 8 . København, 1999-09-27.

Abstract: The 350 meter thick sedimentary succesion at Kap Jungersen, southem Amdrup Land, eastem NOlth Greenland, is dominated by marine shallow water carbonates with minor evaporites and siliciclastics. The age of the succesion is dated to Kashirskian and Podolskian in the Moscovian epoch by correlation of fusulinids to the Russian fusulinid stratigraphy.

33 productive palyno samples were collected and 48 miospore species have been identified and described (Thomsen et al. manus.). 21 of these species are new and described for the first time. Few scolecodonts and no acritarchs have been observed. The miospore assemblage is dominated by saccate striate and non striate pollen. Vitta tina is common.

The composition of the miospore assemblage indicates affinity to the nothem subtropicaI and arid Tianural floral province by similarity to other miospore assemblages in nothem Canada, the Urals and China. Age determination by comparison of the miospore assemblage to the West European miospore zonation indicates an age coresponding to Gzelian – Asselian, which is approximately 1 7 m.y. younger than the age determinated by the cooccouring fusulinids. This age discrepancy is best explained by floral provincialism resulting from differences in aridity between the humid tropicai Euramerica and the arid subtropicai Tianural futher north.

Adresse: Christian Thomsen, Enator A/S, Vesterbrogade 149, DK-1620 København V [cth [at] enator [dot] dk]

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Hadrosauride dinosuarers forben: funktionel morfologi og systematik

Rasmussen, M.E.: Hadrosauride dinosaurers forben; funktionel morfologi og systematik.Geologisk Tidsskrift, hæfte 2, pp. 1 9-23. København, 1999-09-27.

Abstract: Hadrosaurs (Ornithischia, Ornithopoda, Hadrosauridae), Late Cretaceous “duckbilled” dinosaurs, are often reconstructed with incorreetly articulated forelimbs. The palm of the manus is generally reconstructed facing backwards, but the morphology dictates a more medial orientation. This is supported by the orientation of manus prints from quadrupedal trackways of hadrosaurs. The position of manus prints of quadrupedal trackways furthermore suggests that lateral oscillations of the body occurred, when the animal was walking.

A cladistic analysis, based on 92 morphological characters from the forelimbs of 18 hadrosaur species (representing 1 3 genera), eight other ornithopods and the Early Jurrasic ornithischian Heterodontosaurus, resulted in one single, most parsimonious tree. This tree is similar to other published phylogenies, and the family Hadrosauridae, as well as the two subfamilies Hadrosaurinae and Lambeosaurinae, are well defined, as is the group including hadrosaurs and the Early Cretaceous Iguanodon and Ouranosaurus (family Iguanodontidae).

The evolutionary trend of the ornithopod forelimb is traced. The early ornithopods, such as Heterodontosaurus were bipedal, while the forelimb of the intermediate-sized ornithopods was adapted for mass support. In the larger ornithopods, like hadrosaurs and iguanodonts, the forelimbs served several functions, and there are a clear functional division ofthe digits. Mass-support was the main function of the tree middle digits, the fifth digit could be used for manipulation, and perhaps the first digit of the iguanodonts served for defence or display.

Adresse: Mette Elstrup Rasmussen, Geologisk Museum, Københavns Universitet, Øster Voldgade 5- 7, 1350 København K.

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Udforskning af Thylacocephala – en mærkelig gruppe af leddyr

Steeman, F.A .: Udforskningen af Thylacocephala – en mærkelig g ruppe af leddyr. Geologisk Tidsskrift, hæfte 2, pp. 24-28. København, 1999-09-27.

Sammendrag: Thylacocephala er en klasse af leddyr (Arthropoda), der formodentlig har tilknytning til krebsdyrene (Crustacea). Thylacocephala blev først opdaget i starten af 1980′ erne af tre uafhængige forskergrupper. Klassen Thylacocephala blev etableret i 1985 . De andre navne som var foreslået for denne gruppe, Concavicarida og Conchyliocarida, blev henført til ordner indenfor klassen.

Senere er en lang række af nye arter blevet beskrevet. I mange tilfælde har fejlidentificerede fossiler vist sig at tilhøre denne gruppe, hvilket formodentlig også gælder et antal uidentificerede fossile leddyr. Thylacocephalerne optræder fra Silur til Sen Kridt. De har et skjold, der dækker hele kroppen, og som har en indskæring fortil. Ventralt findes tre par store gribelemmer og postero-ventralt er der et antal små, trådformede lemmer. I den forreste indskæring findes en stor, afrundet struktur, som de fleste har tolket som et sammensat øje. Der er dog nogle der betragter denne struktur som en hovedsæk dækket af mikroskæl. Ifølge den førstnævnte tolkning, som nu støttes af de fleste data, var thylacocephaler aktive rovdyr. Nøglekarakterer for identifikation af thylacocephaler gives .

Adresse: Fedor A . Steeman, Grønnegården 332, 2670 Greve [fsteeman [at] dds [dot] nl]

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