Organofacies reconstruction and lipid geochemistry of sediments from the Galicia margin

Samples of Lower to middle Cretaceous rocks from ODP Sites 638, 640, and 641, drilled on the Galicia continental margin in the northeast Atlantic, have been investigated by organic geochemical methods (i.e., organic carbon determination, Rock-Eval pyrolysis, kerogen microscopy, gas chromatography, a...

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Bibliographic Details
Main Authors: Stein, Ruediger, Rullkötter, Jürgen, Littke, Ralf, Schaefer, Rainer G, Welte, Dietrich Hugo
Format: Dataset
Language:English
Published: PANGAEA 1988
Subjects:
103-638B
103-640A
103-641A
103-641C
DRILL
Drilling/drill rig
Joides Resolution
Leg103
North Atlantic Ocean
Ocean Drilling Program
ODP
North Atlantic
Northeast Atlantic
Online Access:https://doi.pangaea.de/10.1594/PANGAEA.743885
https://doi.org/10.1594/PANGAEA.743885
Description
Summary:Samples of Lower to middle Cretaceous rocks from ODP Sites 638, 640, and 641, drilled on the Galicia continental margin in the northeast Atlantic, have been investigated by organic geochemical methods (i.e., organic carbon determination, Rock-Eval pyrolysis, kerogen microscopy, gas chromatography, and gas chromatography/mass spectrometry) to define the Organofacies types and the depositional environments of these sediments. The results of this study fit well into the general picture drawn for the depositional history of the organic matter in Cretaceous organic-carbon-rich sediments in the North Atlantic from previous DSDP investigations. During the Valanginian to Albian, terrigenous organic carbon dominated the organic matter deposited on the Galicia continental margin. Cyclic changes in total organic carbon content were probably controlled by climatic-triggered changes in the supply of terrigenous organic matter from the nearby continent. A drastic change in depositional environment must have occurred near the Cenomanian/Turonian boundary. The preservation of large amounts of marine organic carbon in these sediments was probably caused by anoxic deep-water conditions during that time, rather than high productivity. All of the primary organic matter of the sediment samples investigated is thermally immature, as indicated by very low vitrinite reflectance values.

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