Leszek Marynowski

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 aromatics using capillary gas chromatography–mass spectrometry (GC–MS). The occurrence of two novel series of aromatic hydrocarbons in these sediments, namely phenyl derivatives of fused ring polycyclic aromatic hydrocarbons (PhPAH) and polyphenyls (PPh), was established. Furthermore, the methyl derivatives of these compounds were also present. The chromatographic behaviour of the triaromatic members of the series, i.e. two isomers of phenylnaphthalene (1-PhN and 2-PhN) and three isomers of terphenyl (o-TrP, m-TrP and p-TrP) was evaluated using authentic standards. The isomeric composition of the phenylnaphthalenes (PhNs) and terphenyls (TrPs) was found to depend on thermal 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 maturity parameters of the organic matter based on the relative abundances of the 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 correlate with the vitrinite reflectance (Ro) and MDR, while correlation of the other biomarker maturity parameters such as the Ts/Tm ratio are less apparent. The compounds above are believed to be geochemical products from unknown 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 aromatisation to respective furan and/or thiophene derivatives, and finally reductive elimination of oxygen and sulfur in the furan and thiophene products, respectively.

Phenyldibenzofurans and phenyldibenzothiophenes in marine sedimentary rocks and hydrothermal petroleum

Abstract The phenyl derivatives of dibenzo[ b , d ]furan and dibenzo[ b , d ]thiophene, so far not reported in geological samples, have now been identified in some sedimentary rocks, bitumen and hydrothermal petroleum through a comparison of their retention times and mass spectra with those of authentic standards. All four possible positional isomers were detected for each phenyldibenzo[ b , d ]furan (PhDBF) and phenydibenzo[ b , d ]thiophene (PhDBT). Their elution sequence is 1-, 4-, 2- and 3-phenyldibenzo[ b , d ]furan and 1-, 4-, 2- and 3-phenyldibenzo[ b , d ]thiophene on apolar stationary phases. In contrast to phenyldibenzofurans, the distributions of the thiophene series is controlled mainly by the organic matter maturity. In the most mature samples 4-, 2- and 3-PhDBTs prevail over 1-PhDBT, while less mature samples contain mainly 4-PhDBT or 1-PhDBT and 2-, 3-PhDBTs occur at comparable concentrations. However, in samples of low maturity, in addition to the phenyldibenzo[ b , d ]thiophene C 18 H 12 S series, other structural isomers of C 18 H 12 S possessing very similar mass spectra were detected. These are likely to be either naphthylbenzo[ b ]thiophenes and/or phenylnaphtho[ b ]thiophenes. PhDBFs and PhDBTs are likely to be intermediate products in the formation of more condensed heterocyclic polycyclic aromatic compounds like triphenyleno[1,12 −bcd ]thiophene and triphenyleno[1,12 -bcd ]furan, and benzobisbenzofurans and benzobisbenzothiophenes, which are commonly detected in geological samples.

New constraints on the Middle Palaeozoic to Cenozoic burial and thermal history of the Holy Cross Mts. (Central Poland): results from numerical modelling

A 1-D burial-thermal modelling was performed using data from two borehole sections representative of the central part of the Holy Cross Mts. area. This area is located in the axial part of the Permian-Mesozoic Mid-Polish Trough that was inverted during the latest Cretaceous-Paleocene. The modelling involved different variants of restored stratigraphy of eroded Carboniferous to Cretaceous strata, whereas calibration was based on samples from cored Middle-Upper Devonian sediments. The modelling results are consistent with the assumption of a Variscan (Carboniferous-Early Permian) heat flow elevated up to 80 mWm -2 , which is further confirmed by independent regional evidence. The zone of increased thermal maturity in the Devonian may be partly accounted for by a thicker Carboniferous section (by ca. 500 m) compared to previous estimates. Two variants of the post-Carboniferous geohistory were analysed. The variant of a thinner Permian-Mesozoic section, implying lower magnitude of the Late Cretaceous-Paleogene inversion, allows more realistic assumptions regarding heat flow distribution through time, including the possibility to incorporate an elevated Variscan heat flow. The alternative scenario, assuming deeper burial, generally lower heat flow and smaller Carboniferous thickness, is regarded as less probable. The accepted variant of the Permian-Mesozoic burial history implies that the total post-Carboniferous burial in the study area was on the order of 2000-2500 metres rather than 3000-3500 metres. The respective Upper Cretaceous thickness could have been 400 to 500 m instead of ca. 1000 m, whereas the Late Cretaceous-Paleogene inversion more likely started in the Santonian than in the late Maastrichtian. Consequently, the preferred magnitude of total inversion was on the order of 2500 m. Basin modelling. subsidence. Heat flow. tectonic inversion. Holy Cross Mountains.

Organic geochemical characteristics of the Mississippian black shales from Wardie, Scotland

Coal and hydrocarbons have been exploited from the Carboniferous rocks of the Midland Valley for over 200 years. This work characterises organic matter from the Mississippian black shales of the Midland Valley from Wardie, Scotland. Biomarker analysis allowed the estimation of the degree of microbial transformation of organic matter, type of kerogen and thermal maturity during hydrocarbon generation. Parameters based on the biomarker indicators confirm a generally mixed type II/III kerogen. However, some samples contain mostly terrestrial organic matter, whilst others contain predominantly marine organic matter, which shows that the sedimentary environment varied greatly throughout the basin. The presence of gammacerane suggests water column stratification and anoxic conditions. Organic matter was much better protected from post-depositional alteration within the concretions, where higher TOC (total organic carbon) and TS (total sulphur) contents occur, than in the surrounding sediments. This can be induced by very early diagenetic formation of these concretions which protected organic matter from late diagenetic degradation. Estimated values of vitrinite reflectance (Rc, Rcs) show that the sedimentary rocks reached the catagenesis stage. Most samples exhibit maximum organic matter maturation temperatures of around c 60–90°C. However, stable isomers of phenyldibenzo[ b,d ]thiophene detected in some samples indicate that in some cases post-depositional hydrothermal activity affected maturation of organic matter increasing temperatures to as high as c 174°C.