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High resolution of environments in estuarine to fluvial sediments of the Middle Eocene at Helmstedt, nothern Germany

Riegel, W. and Lenz, O. K. and Wilde, V. (2010):
High resolution of environments in estuarine to fluvial sediments of the Middle Eocene at Helmstedt, nothern Germany.
Stuttgart, Schweizerbart, In: GeoDarmstadt 2010, Darmstadt, 10.10.2010 -13.10.2010, In: Due to a steep gradient in physical and chemical condi-tions environments and ecology are subject to rapid changes across the shoreline in land to sea transects which are therefore highly differentiated in space and time. Their reconstruction in ancient s, ISSN ISSN: 1860-1782 , [Online-Edition: https://www.schweizerbart.de/series/sdgg],
[Conference or Workshop Item]

Abstract

Due to a steep gradient in physical and chemical condi-tions environments and ecology are subject to rapid changes across the shoreline in land to sea transects which are therefore highly differentiated in space and time. Their reconstruction in ancient sediments is facili-tated in considerable detail by using sedimentological and biotic proxies as well as modern analogues for comparison. Early and Middle Eocene coal bearing sequences exposed in open cast mines near Schöningen and Helmstedt include numerous land/sea transitions, since for most of the Palaeogene the Helmstedt area was located at the mouth of a broad estuary at the southern shore of the North Sea basin. There it was exposed to the interaction between sea level fluctua-tions, basin subsidence, and sediment transfer from land to sea. To demonstrate the potential of high resolution recon-struction of estuarine to fluvial environment transitions some examples are selected from exceptionally well exposed Middle Eocene sections in the former open cast mine Helmstedt. Here, Ophiomorpha bearing estu-arine sediments, occasionally interrupted by transient terrestrialization, are dissected by extensive point bar successions of active fluvial channels which often end in abandoned channels filled either with clay or coal. In the absence of carbonate and shelly fossils environ-ment reconstructions have to rely entirely on the analy-sis of sedimentary and organic facies. Nevertheless, salinity gradients and progressive terrestrialization can be traced in detail across the shoreline by means of dinocyst populations and mangrove to mire forest pol-len assemblages. Point bar sediments provide clues to the dynamics of the active fluvial channel, while aban-doned channel fills are excellent archives of hydrologic conditions in oxbow lakes and their surrounding vegeta-tion.

Item Type: Conference or Workshop Item
Erschienen: 2010
Creators: Riegel, W. and Lenz, O. K. and Wilde, V.
Title: High resolution of environments in estuarine to fluvial sediments of the Middle Eocene at Helmstedt, nothern Germany
Language: English
Abstract:

Due to a steep gradient in physical and chemical condi-tions environments and ecology are subject to rapid changes across the shoreline in land to sea transects which are therefore highly differentiated in space and time. Their reconstruction in ancient sediments is facili-tated in considerable detail by using sedimentological and biotic proxies as well as modern analogues for comparison. Early and Middle Eocene coal bearing sequences exposed in open cast mines near Schöningen and Helmstedt include numerous land/sea transitions, since for most of the Palaeogene the Helmstedt area was located at the mouth of a broad estuary at the southern shore of the North Sea basin. There it was exposed to the interaction between sea level fluctua-tions, basin subsidence, and sediment transfer from land to sea. To demonstrate the potential of high resolution recon-struction of estuarine to fluvial environment transitions some examples are selected from exceptionally well exposed Middle Eocene sections in the former open cast mine Helmstedt. Here, Ophiomorpha bearing estu-arine sediments, occasionally interrupted by transient terrestrialization, are dissected by extensive point bar successions of active fluvial channels which often end in abandoned channels filled either with clay or coal. In the absence of carbonate and shelly fossils environ-ment reconstructions have to rely entirely on the analy-sis of sedimentary and organic facies. Nevertheless, salinity gradients and progressive terrestrialization can be traced in detail across the shoreline by means of dinocyst populations and mangrove to mire forest pol-len assemblages. Point bar sediments provide clues to the dynamics of the active fluvial channel, while aban-doned channel fills are excellent archives of hydrologic conditions in oxbow lakes and their surrounding vegeta-tion.

Journal or Publication Title: Schriftenreihe der Deutschen Gesellschaft für Geowissenschaften
Series Name: Due to a steep gradient in physical and chemical condi-tions environments and ecology are subject to rapid changes across the shoreline in land to sea transects which are therefore highly differentiated in space and time. Their reconstruction in ancient s
Volume: 68
Place of Publication: Stuttgart
Publisher: Schweizerbart
Divisions: 11 Department of Materials and Earth Sciences > Earth Science > Applied Sedimentary Geology
11 Department of Materials and Earth Sciences > Earth Science
11 Department of Materials and Earth Sciences
Event Title: GeoDarmstadt 2010
Event Location: Darmstadt
Event Dates: 10.10.2010 -13.10.2010
Date Deposited: 18 Feb 2015 13:10
Official URL: https://www.schweizerbart.de/series/sdgg
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