Phenylnaphthalenes and polyphenyls in Palaeozoic source rocks of the Holy Cross Mountains, Poland

Source rocks from a marine depositional setting from Palaeozoic formations in the Holy Cross Mountains region (Midlands, Poland) were analysed for aro matics using capillary gas chromatography-mass spectrometry (GC-MS). The oc currence of two novel series of aromatic hydrocarbons in these sediments, n amely phenyl derivatives of fused ring polycyclic aromatic hydrocarbons (Ph PAH) and polyphenyls (PPh), was established. Furthermore, the methyl deriva tives of these compounds were also present. The chromatographic behaviour o f the triaromatic members of the series, i.e. two isomers of phenylnaphthal ene (1-PhN and 2-PhN) and three isomers of terphenyl (o-TrP, m-TrP and p-Tr P) was evaluated using authentic standards. The isomeric composition of the phenylnaphthalenes (PhNs) and terphenyls (TrPs) was found to depend on the rmal maturity. In the lower maturity samples abundances of 1-PhN and o-TrP are higher. Increase in sample maturity is indicated by an increase in the relative abundance of 2-PhN as well as m-TrP and p-TrP. Three thermal matur ity parameters of the organic matter based on the relative abundances of th e PhN and TrP isomers are proposed: PhNR = 2-PhN/1PhN, TrP1 = p-TrP/o-TrP, and TrP2 = (m-TrP + p-TrP)/o-TrP. In general their values positively correl ate with the vitrinite reflectance (R-o) and MDR, while correlation of the other biomarker maturity parameters such as the Ts/Tm ratio are less appare nt. The compounds above are believed to be geochemical products from unknow n precursors. A potential geochemical process of formation for the o-TrP is proposed, and involves initial preservation of carbohydrates in sediments through sulfur incorporation, further dehydration, cyclisation and aromatis ation to respective furan and/or thiophene derivatives, and finally reducti ve elimination of oxygen and sulfur in the furan and thiophene products, re spectively. (C) 2001 Elsevier Science Ltd. All rights reserved.