Vitrinite equivalent reflectance of Silurian black shales from the Holy Cross Mountains, Poland

Abstract

A number of independent methods have been used to measure the thermal maturity of Silurian rocks from the Holy Cross Mountains in Poland. Black shales are characterized by diverse TOC values varying from 0.24-7.85%. Having calculated vitrinite equivalent reflectance using three different formulas, we propose that the most applicable values for the Silurian rocks are those based on Schmidt et al. (2015) equation. Based on this formula, the values range from % 0.71 VReqvVLR (the vitrinite equivalent reflectance of the vitrinite-like macerals) to % 1.96 VReqvVLR. Alternative, complementary methods including Rock Eval pyrolysis and parameters based on organic compounds (CPI, Pr/n-C17, Ph/n-C18, MPI1, and MDR) from extracts did not prove adequate as universal thermal maturity indicators. We have confirmed previous suggestions that Llandovery shales are the most likely Silurian source rocks for the generation of hydrocarbons in the HCM.

Mercury Spikes Indicate a Volcanic Trigger for the Late Ordovician Mass Extinction Event: An Example from a Deep Shelf of the Peri-Baltic Region

“…Trela et al . 32 postulate that pyroclastic material was transported to the HCM by westerlies from the Avalonian volcanoes. Alternatively, Shen et al .…”

“…1), representing different types of Upper Ordovician and lower Llandovery claystone, mudstone, and black shale. The investigated samples are characterised by a relatively low level of thermal maturity ( ca 0.72% of the vitrinite equivalent reflectance measured on graptolites) 32 . Upper Ordovician strata of the Zbrza PIG-1 borehole consist of the Sandbian to Hirnantian mudrock facies that form up to 90 m of the succession (Fig.…”

Tectonothermal history of the Holy Cross Mountains (Poland) in the light of low‐temperature thermochronology

“…There is no consensus on the tectonothermal evolution of the HCM and several contradicting models have been proposed. Most authors (Bełka, ; Marynowski, , ; Marynowski, Salamon, & Narkiewicz, ; Naglik, Toboła, Natkaniec‐Nowak, Luptáková, & Milovská, ; Narkiewicz, ; Narkiewicz, Resak, Littke, & Marynowski, ; Smolarek, Marynowski, Spunda, & Trela, ) argue for an elevated Variscan (late Carboniferous to early Permian) heat flow, which significantly exceeded the current low values (Szewczyk & Gientka, ). However, Poprawa, Żywiecki, and Grotek () proposed that thermal maturity of organic matter in the Devonian to Jurassic sedimentary successions was achieved during Late Jurassic or Late Cretaceous burial that was characterized by constant heat flow equal to the recent one (Szewczyk & Gientka, ).…”

Lower Wenlock black shales in the northern Holy Cross Mountains, Poland: sedimentary and geochemical controls on the Ireviken Event in a deep marine setting

“…1), which comprises claystones and black shales (see Deczkowski & Tomczyk, 1969). Owing to the relatively high thermal maturation of the sediments (within the 'gas window'; conodont alteration index: CAI > 2, Narkiewicz, 2002; vitrinite-like maceral values calculated to vitrinite reflectance VR equ = ß1.7 %, Smolarek et al 2014), our research has focused on redox proxies that are not susceptible to alteration by heat, such as pyrite framboid petrography and trace metal concentrations. Sedimentological observations of colour, lithology, sedimentary structures and ichnofabric are supported by thin-section petrography of microfacies.…”