Chemical logging of continental-marine depositional systems. A tool to unravel the palaeogeography and diagenetic alteration of fine-grained clastic rocks in a transitional environment of deposition (Triassic-Liassic, Southeastern Germany)

authored by

H. G. Dill, H. Wehner, R. Botz, S. Dultz

Abstract

From the Late Triassic through the Early Liassic, at the northern edge of the North Bavarian Tableland, Southeastern Germany, fine-grained clastic rocks were deposited in a spectrum of depositional environments. The oldest sediments formed in a playa, the youngest sediments in a nearshore marine depositional system of an epeiric sea. Following a large-scale sampling of drill holes, chemical analyses including major elements (Si, Al, Fe, Mg, Mn, Ca, K, Ti, P, TOC, TSC), trace elements (Ba, Cr, Ga, V, Cu, Pb, Mo, Zn, Ni, Th, U, Zr), organic compounds (e.g. n-alkanes), carbon and oxygen isotopes the interpretation of the palaeogeographic evolution has been performed. During Rhaetian times the sea encroached upon the upper Triassic playa depositional system giving rise to a terrigenous linear shoreline environment which by the beginning of the Liassic was incised by valleys. A short term fluvially-sourced deltaic environment during the Early Liassic was substituted for by another terrigenous linear shoreline environment with palimpsest beach deposits. Subsequently, nearshore brackish marine environments gradually gave way to a fully marine epicontinental depositional system with some shoals scattered across this basin. The chemical composition of phyllosilicates, C isotopes (palaeosalinity indicator), trace elements such as Ba, U, Cu, Pb, Zn, P (palaeoenvironment indicator) and element ratios such as Fe/Mn (redox indicators) prove to be valuable tools to constrain the environment of deposition. Investigations of the organic matter provide a tool to interpret the environment of deposition and determine late stage diagenetic alteration, which took place under the influence of brackish pore waters at temperatures of as much as 70 °C.

Organisation(s)

Institute of Soil Science
Section Soil Chemistry

External Organisation(s)

Federal Institute for Geosciences and Natural Resources (BGR)
Kiel University

Type

Article

Journal

Chemie der Erde

Volume

60

Pages

129-171

No. of pages

43

ISSN

0009-2819

Publication date

05.2000

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Geophysics, Geochemistry and Petrology

Sustainable Development Goals

SDG 14 - Life Below Water