--> ABSTRACT: Facies Architecture and Sedimentology of Fluvial Deposits: A Paleogene Example from the Weisselster Basin, Germany, by Jochen Halfar; #91020 (1995).

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Facies Architecture and Sedimentology of Fluvial Deposits: A Paleogene Example from the Weisselster Basin, Germany

Jochen Halfar

The Schleenhain open pit coal mine, located 30km south of Leipzig, Germany, in the center of the Weisselster Basin, reveals outcrops of upper Eocene and Oligocene strata. As a result of active mining and successive cuts into the high wall a 3-dimensional fence diagram was constructed. This provided the basis for recognition of key architectural elements in the weakly consolidated meandering stream deposits. In addition to the eight basic architectural elements of Miall (1985) the element SL (shallow lake deposits) was newly defined and the element CH was subdivided into CHg (paleo river system) and CHk (small channel). The profiles contain parts of two fining-upward cycles, which are separated by an unconformity that, based on paleobotanical data, spans the lower Oligocen . Deposits of the first cycle begin with transverse sand bars (downstream accretion deposits-DA) and point bars (lateral accretion deposits-LA). The upper part of the cycle is represented by overbank fines (OF) and the element SL, which consists of laterally discontinuous lenses of dark, plant-bearing, kaolinite-rich clays, that were deposited in shallow lakes adjacent to the active channel. Coal seams interlayered with paleosols are the main constituents of element OF. Sheetlike bodies of medium to fine gravels (gravel bars and bedforms-GB) on an erosive coal surface mark the beginning of the second cycle.

Dissolution of underlying Permian salts and sulfates prior to, during, and after the deposition of the Paleogene strata caused the development of two synclines within the outcrop. Coal seams and clay horizons, that both thicken and dip towards the center of the synclines, provide evidence for their chronological development.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995