Advances in Organic Geochemistry 1989 Org. Geochem. Vol. 16, Nos 4--6, pp. 749-761, 1990 Printed in Great Britain. All rights reserved 0146-6380/90$3,00+ 0.00 Copyright © 1990 PergamonPress plc Aromatic hydrocarbon composition of the Permian Kupferschiefer in the Lower Rhine Basin, NW Germany L. SCHWARK and W. PUTTMANN Lehrstuhl fiir Geologic, Geochemie und Lagerst~itten des Erdrls und der Kohle, RWTH Aachen, Lochnerstr. 4-20, 5100 Aachen, F.R.G. (Received 10 October 1989; accepted 18 February 1990) Abstract--The aromatic hydrocarbon composition of 25 samples of Permian Kupfersehiefer from the Lower Rhine Basin of NW Germany has been investigated using GC, GC/MS and direct probe MS analysis. Two narrow-sampled profiles were investigated with respect to compositional changes during Kupferschiefer sedimentation and samples from 13 different wells, covering a depth range from 350 to 1000 m, were included in order to study temperature-sensitive variations. In the Kupferschiefer trimethyl- substituted aryl isoprenoids in the range from Ca to C2~ occur. These compounds presumably are degradation products of isorenieratane, which is also present in the extracts. Within the profile the amount of a preferentially occurring C29-chroman increases from the bottom to the top of the Kupferschiefer by a factor of about 2.5. The chroman distribution observed in the Kupferschiefer points towards euhaline to mesohaline seawater during sedimentation. Moreover, in the investigated profiles a terrestrial source input mainly in the bottom-most part of the shale is reflected by the occurrence of a monoaromatic C24-chrysene derivative, presumably derived from ring-A-degradation of pentacyclic triterpenes. Key words--aromatic hydrocarbons, chromans, aryl isoprenoids, palaeosalinity, Kupferschiefer INTRODUCTION The distribution of aromatic hydrocarbons in crude oils, extracts of sedimentary rocks and coals has been widely investigated for maturation assessment (Radke, 1987). Moreover, the composition of naph- thalenes and phenanthrenes is revealed to be influ- enced by the type of organic matter initially deposited in sediments (Radke et al., 1986; Strachan et al., 1988; Piittmann and Kalkreuth, 1989). The composition of C-ring monoaromatic or triaromatic steriod hydro- carbons, as well as the aromatization stage of steroids used for the investigation of the time/temperature history of sediments (e.g. Mackenzie and McKenzie, 1983) has also been shown to be facies-dependent (Moldowan et al., 1986; Riolo et al., 1986; Curiale and Odermatt, 1989). One of the best investigated groups of specific aromatic biomarkers is the resin- related phenanthrene derivatives (Simoneit et aL, 1986). Moreover, diagenetic products of aromatic carotenoids in crude oils and sediments were shown to indicate the presence of green sulphur bacteria in ancient marine environments (Summons and Powell, 1986, 1987). Oxygen-containing moieties, such as chromans detected in the so-called "aromatic" hydro- carbon fractions of extracts (Brassell and Eglinton, 1986) were suggested to be useful for the assessment of the palaeosalinity of sediments (Sinninghe Damst6 et al., 1987a). Furthermore, the occurrence of aryl isoprenoids in crude oils and sediments from the Michigan and Alberta Basins, Canada, was related to hypersaline environmental conditions (Summons and Powell, 1987). In carbonate-derived crude oils thio- phenic organo-sulphur compounds (primary benzo- and dibenzothiophenes) were detected as typical con- stituents of aromatic hydrocarbon fractions (Hughes, 1984). Alkyl thiophenes as potential precursors of benzothiophenes have been investigated in detail by Sinninghe Damst6 et al. (1987b). Previous investi- gations of the organic matter in the Kupferschiefer were carried out mainly with emphasis on the satu- rated hydrocarbon fraction for maturation assess- ment (Pfittmann et al., 1989; Piittmann and Eckardt, 1989). Concerning the aromatic hydrocarbons pre- sent in the Kupferschiefer, to date investigations have only been carried out with respect to mono- and triaromatic steroids (P/ittmann et al., 1989). The present study is aimed at a detailed analysis of the aromatic hydrocarbon composition for the assess- ment of maturation, salinity and biological input of the Kupferschiefer deposited in the shallow lagoon of the Lower Rhine Basin. EXPERIMENTAL Geological overview and sample description In the Upper Permian four major evaporitic sedimentary sequences (Richter-Bernburg, 1955) developed within the Southern Permian Zechstein Basin which extended from the east coast of Great Britain further to the eastern border of Poland. The southern shoreline ran along the London-Brabant, the Rhenish and the Bohemian Massifs. In the area 749