Mirosław Słowakiewicz

Upper Permian (Zechstein) microbialites: Supratidal through deep subtidal deposition, source rock, and reservoir potential

Zechstein 2 (Z2) carbonate microbialites flourished under arid paleoclimatic conditions in the Late Permian. Microbial carbonates from the Roker Formation outcrop in northeast England, with its subsurface equivalent being the Main Dolomite from northwest–central Poland. The Z2 carbonate deposits developed in supratidal through deep subtidal zones and consist of various stromatolites and thrombolites. Planar stromatolites and thrombolites characterize intertidal and supratidal facies, and biohermal stromatolites with oolitic grainstone and crinkled stromatolites typify shallow subtidal facies. The Z2 subtidal and/or intertidal microbialites with oolites form complexes more than 10 m (33 ft) thick and are important reservoir facies for hydrocarbons. Subtidal (slope) and intertidal (lagoonal) microbial mudstone and wackestone have poor reservoir properties but contain total organic carbon as much as 2 wt. % and are considered as potential source rocks. The thermal maturity assessed from C27 17-trisnorhopane (Tm) and C27 18-trisnorhopane (Ts) as the Ts/(Ts + Tm) ratio, C30 moretane/hopane ratio, sterane ratio expressed as 20S/(20S + 20R), and /( + ) ratio shows to indicates a mature character of organic matter with respect to oil generation.

Palaeozoic Climate Cycles: Their Evolutionary and Sedimentological Impact

This volume presents results of a variety of case studies documenting the Late Palaeozoic climate changes and cyclicity of deposition. The collected papers cover many aspects related to palaeoenvironmental analysis with sedimentological, stratigraphic, palaeobiological, geochemical, and palaeomagnetic studies of the fossil record around the Late Palaeozoic Ice Age and soon after. They span a stratigraphic interval from Carboniferous to Permian–Triassic transition around the world. This book comprising results for a range of disciplines, is a valuable source for not only researchers who are actively working on specific aspects of the Late Palaeozoic and looking for an up-to-date reference on this inhospitable time in the Earth’s history. It is also of interest to climate modellers and the wider scientific community with an interest in the latest research on the decline of the Palaeozoic World.

Holocene Intertidal Microbial Mats Of Qatar And Their Implications For Petroleum Source Rock Formation In Carbonate-Siliciclastic-Evaporite Systems

Organic-rich mesohaline microbial mats occur in the intertidal zone of a lagoonal area developed to the lee of a coastal spit in Mesaieed, Eastern Qatar. The mats grow on a substrate of seagrass-rich carbonate mud with cerithid and monachid gastropods and other small bioclasts, reaching a thickness >3.5 cm. The mats are well laminated with different microbial communities, from cyanobacteria to sulphur bacteria, reflected in the distinct colour changes from green to pink to brown. The mat layers contain spheroids of dolomite, the precipitation of which was plausibly mediated by bacteria. The lipids reflect the biomass of the principal mat-building phototrophic and heterotrophic microorganisms. A variety of hydrocarbons, including n-alkanes, diploptene, and isoprenoids such as phytane, phytene, phytadiene and squalene were detected, in varying concentrations amongst the particular mat layers. In particular, n-heptadecane, likely derived from cyanobacteria, dominated the n-alkane distribution at a depth of 0-0.1 mm. The concentration and abundance of n-alkanes increase with depth through the mat, likely representing the early diagenetic initiation of hydrocarbon generation. Therefore, understanding early diagenetic organic matter alteration and preservation in marine mixed carbonate-evaporite-siliciclastic systems, as well as the processes operating in the early stages of diagenesis, could improve understanding of the hydrocarbon potential of such systems. This will help considerably in the prediction of hydrocarbon occurrence in frontier, as well as mature, petroleum carbonate-evaporite basins.

Palaeoclimatic imprint, distribution and genesis of Zechstein Main Dolomite (Upper Permian) petroleum source rocks in Poland: Sedimentological and geochemical rationales

Abstract Arid palaeoclimatic conditions and marine current circulation influenced organic matter productivity and its distribution and preservation in the Upper Permian (Zechstein) Main Dolomite (Ca2) source rocks in Poland. The gaseous and liquid hydrocarbons occurring within the Main Dolomite show distinctive geochemical characteristics which distinguish them from those derived from Carboniferous or other Permian strata and indicate that the main type of organic matter from which they were derived was of microbial origin. It is suggested here that the majority of the Ca2 hydrocarbons come from in situ organic matter (intraformational deposits). The lagoonal and slope zones are enriched in total organic carbon (TOC) compared to both the oolite shoal and basinal facies. These sedimentary settings were dominated by various biolaminated microbialite facies. The basinal areas, previously believed to be the location of the main source rocks for hydrocarbons found in the Main Dolomite, appear to have little source rock potential. Geochemical and geological features such as high organic productivity in lagoonal and slope zones of the Main Dolomite indicate that at least some of the hydrocarbons may have been generated from in situ deposited and degraded organic matter. This conclusion may improve prediction of the occurrence of hydrocarbon deposits in the Ca2.

Late Palaeozoic environmental changes: an introduction

The idea of this volume arose from our proposal to the palaeoclimatic session held at the European Geosciences Union General Assembly 2011 Conference in Vienna (Austria). Although the original scope was broader, the included contributions focus on palaeoenvironmental changes during the late Palaeozoic. Late Palaeozoic history is especially important in that it records an increase of tectonics/diastrophism, frequent sea-level fluctuations and climatic changes, all finally leading to the most geocratic time of Earth’s history with the formation of the supercontinent Pangaea. This volume includes a number of articles that discuss the fossil record around the Late Palaeozoic Ice Age, and its decline during the Carboniferous with its unusual plant proliferation soon after, when the hottest and driest period in Earth’s history (in the Permian) caused the development of huge ‘sand seas’ on the land. Finally, a biotic event, the largest mass extinction in Earth History at the Permian–Triassic transition, ends the Palaeozoic world. This volume addresses two key issues – the palaeoclimate and depositional cycles – both of which have a strong impact on the record of palaeoenvironmental changes and the understanding of environmental perturbations. The vigorous current debate on the future climate of the globe inevitably increases our interest in past climates. From a geological perspective, climatic perturbations occurred many times before humans were on the planet. Climate varies on several timescales, depends on many high-order factors including tectonic uplift and the orbital wandering of the Earth, and as a result it changes through time. Consequently, palaeoclimatic reconstructions are growing in their importance as they enable us to use the past as a key to the future. The Earth’s system experiences various cycles of very different origin, scale, frequency, amplitude, phase and basic level. From a geological perspective, the cyclicity appears unidirectional, like Brownian motion. However, in the past, the complex interaction of these cycles has led to catastrophic changes in Earth’s systems, such as those during the late Palaeozoic, when palaeoclimatic and geotectonic cycles coincided. These cycles are also influencing our lives, and will do so in our future, so their impact needs to be understood. The geological archives record both the climatic and cyclic phenomena on local to regional scales, including in the late Palaeozoic, as documented in this volume. Understanding these records will improve our predictions about climate phenomena in the future. They also show that the present climatic perturbations are insignificant from a geological point of view. Changes in the late Palaeozoic Earth system are illustrated in this volume by case studies of fossil records from North and South America, East and South Asia, South Africa and Australia, and as regional reviews (section one). The methods include palaeoenvironmental analysis, including palaeobiological, sedimentological, stratigraphic (sequence stratigraphy), palaeomagnetic and geochemical methods. They describe various environmental settings from palaeodeserts, through marine-associated giant salt pans, to shallow to deep marine records. The articles report new data from less known study areas, provide up-to-date data ordering, and expand our knowledge of the evolution of marine and terrestrial environments, climatic changes and biotic events in late Palaeozoic time. This special publication is divided into five chapters, the first comprising articles focused on the broad descriptive character of Late Carboniferous to Early Triassic palaeoclimatic changes and stratigraphy (with the latest part of this period in Europe, i.e. Zechstein). Subsequent articles include more detailed studies of the geological periods grouped into the latest Devonian to Early Carboniferous (section two), Late Carboniferous to Early Permian (section three), Middle to Late Permian (section four), and finally the Permian–Triassic transition (section five). A brief synopsis of individual papers is given below. Wopfner (2012) reviews Westphalian–Early Triassic palaeoclimatic conditions between Samfrau (comprising the southern margins of South America and South Africa, extending via Antarctica