TY - JOUR
T1 - Petrographic and organic geochemical study of the Eocene Kosd Formation (northern Pannonian Basin): Implications for paleoenvironment and hydrocarbon source potential
AU - Körmös, Sandor
AU - Bechtel, Achim
AU - Sachsenhofer, Reinhard
AU - Radovics, Balazs G
AU - Milota, Katalin
AU - Schubert, Felix
PY - 2020/8/1
Y1 - 2020/8/1
N2 - The Eocene Kosd Formation forms part of the Hungarian Palaeogene Basin. The coal measure of this formation was investigated using an 18 m drill core from borehole W–1. Petrographic and organic geochemical investigations (Rock-Eval pyrolysis, biomarker analysis) were performed in order to characterize the depositional environment, to determine the source of the organic matter within, and to assess the hydrocarbon generative potential. The presence of marine fossils, high TOC/S ratios and ash yields show that the deposition of the coal measure occurred in a marine delta with individual coal layers accumulating in low-lying, rheotrophic mires. The distribution of land plant-derived biomarkers demonstrates that the peat-forming vegetation was dominated by angiosperms, but the relative contribution of gymnosperms varied through time. In addition to land plants, algae and aquatic macrophytes contributed to the biomass. This dense vegetation established a CO
2-limited environment forcing aquatic plants to utilise HCO
3
− during photosynthesis. The marine environment, as well as the predominance of carbonate rocks in the hinterland, caused slightly alkaline conditions, which, together with reduced oxygen availability, stimulated sulphate-reducing bacterial activity and the microbial degradation of plant remains. Consequently, Kosd Formation coal is very rich in sulphur (up to 8.8%). Moreover, the coal contains vitrinite with a strong orange-brown fluorescence colour and swells strongly during pyrolysis. These features are typical for coals with marine influences. Vitrinite reflectance, Tmax, and biomarker proxies indicate that the organic matter is thermally mature and that the Kosd coal reached the high volatile bituminous rank in the deep borehole (~2.6 km depth). Rock-Eval parameters imply that the coal is gas- and oil-prone and reached the maturity threshold critical for first gas generation and the onset of oil expulsion.
AB - The Eocene Kosd Formation forms part of the Hungarian Palaeogene Basin. The coal measure of this formation was investigated using an 18 m drill core from borehole W–1. Petrographic and organic geochemical investigations (Rock-Eval pyrolysis, biomarker analysis) were performed in order to characterize the depositional environment, to determine the source of the organic matter within, and to assess the hydrocarbon generative potential. The presence of marine fossils, high TOC/S ratios and ash yields show that the deposition of the coal measure occurred in a marine delta with individual coal layers accumulating in low-lying, rheotrophic mires. The distribution of land plant-derived biomarkers demonstrates that the peat-forming vegetation was dominated by angiosperms, but the relative contribution of gymnosperms varied through time. In addition to land plants, algae and aquatic macrophytes contributed to the biomass. This dense vegetation established a CO
2-limited environment forcing aquatic plants to utilise HCO
3
− during photosynthesis. The marine environment, as well as the predominance of carbonate rocks in the hinterland, caused slightly alkaline conditions, which, together with reduced oxygen availability, stimulated sulphate-reducing bacterial activity and the microbial degradation of plant remains. Consequently, Kosd Formation coal is very rich in sulphur (up to 8.8%). Moreover, the coal contains vitrinite with a strong orange-brown fluorescence colour and swells strongly during pyrolysis. These features are typical for coals with marine influences. Vitrinite reflectance, Tmax, and biomarker proxies indicate that the organic matter is thermally mature and that the Kosd coal reached the high volatile bituminous rank in the deep borehole (~2.6 km depth). Rock-Eval parameters imply that the coal is gas- and oil-prone and reached the maturity threshold critical for first gas generation and the onset of oil expulsion.
KW - Eocene Kosd Formation
KW - High volatile bituminous coal
KW - Hungarian Palaeogene Basin
KW - Organic geochemistry
KW - Organic petrology
UR - https:// doi.org/10.1016/j.coal.2020.103555
UR - http://www.scopus.com/inward/record.url?scp=85088294278&partnerID=8YFLogxK
U2 - 10.1016/j.coal.2020.103555
DO - 10.1016/j.coal.2020.103555
M3 - Article
SN - 0166-5162
VL - 228
JO - International journal of coal geology
JF - International journal of coal geology
M1 - 103555
ER -