Original paper

Chemical facies and proximity indicators of continental-marine sediments (Triassic to Liassic, SE Germany)

Dill, Harald G.; Dultz, Stefan

Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen Band 221 Heft 3 (2001), p. 289 - 324

70 references

published: Aug 31, 2001

BibTeX file

ArtNo. ESP155022103001, Price: 29.00 €

Download preview PDF Buy as PDF

Abstract

A facies analysis involving investigations of trace and major elements as well as studies of heavy and clay minerals was focused on Late Triassic to Early Jurassic series which were formed in a transitional environment of deposition between land and sea (North Bavarian Tableland). During Rhaetian and early Jurassic times a striking change in the paleogeography took place (playa, terrigenous linear shoreline, deltaic, nearshore brackish and fully marine epicontinental depositional systems). Elements such as U, Th, Pb, Cu and REE form a reliable tool for facies discrimination. Zinc increases basinward and may be used as a proximity indicator as it is the case with the Fe/Sc and Mn/Fe ratios, which are a direct response to the redox conditions in the basin. From sea towards land the Fe/Sc ratio increases and its graph becomes more oscillating. The Mn/Fe ratios display a reverse trend, with fluctuating curves in the basin centre and an almost straight line in the downhole plots near the basin edge, reflecting a conspicuous decrease in calcareous interbeds. The Jurassic transgression provoked a decreasing-upward trend in the graph of the Cr/Ni ratio, which mirrors variation in provenance and continental run-off. Ratios involving Si, Zr and Hf and REE tot are reliable tools as proximity indicators as they are correlative to bed load deposition of rock forming minerals such as quartz and phyllosilicates as well as heavy minerals. Of these elements Zr offers a valuable tool to constrain reworking and beach placer deposits within the sedimentary record.

Kurzfassung

Basierend auf der mineralogischen und chemischen Zusammensetzung klastischer und karbonatischer Sedimente wurde eine Faziesanalyse der obertriassischen und liassischen kontinental-marinen Serien des nordbayerischen Schichtstufenlandes durchgeführt. In dieser durch verschiedene Ablagerungsmilieus gekennzeichneten Region haben sich die Elemente U, Th, Pb, Cu und die REE als Faziesindikatoren bewährt. Verhältnisse, die die Elemente Fe, Mn, Sc, Cr, Ni, Si, Hf, Zr und die REE beinhalten, wie auch der Zinkgehalt eignen sich sehr gut zur Kennzeichnung des Abstands zwischen Paläoküstenlinie und dem untersuchten Ablagerungsraum.

Keywords

facies analysisRhaetianJurassicfluctuatingpaleogeographytransgressionNorth Bavarian Tableland