Eocene Coals Research Articles

Microfacies and Paleomire Reconstruction of Coal in the Tanjung Formation, Barito Basin, Kandangan Area, South Kalimantan

Abstract The occurrence of the Tanjung Formation as a coal-bearing formation that has thick coals and is laterally distributed along in Barito Basin causes it to be well-known as one of the biggest coal-producing basins in Indonesia. The genesis of Eocene coal formed in terrestrial depositional environment influenced by freshwater and marine transgression is the uniqueness of this coal and interesting to examine maceral’s characteristic and its microfacies, and the evolution of paleomire seam AGM-B3, AGM-B4, AGM-B5, and AGM-B6 in Kandangan area by organic petrography’s analysis and coal’s chemical analysis. The result of subbituminous coal’s petrography show vitrinite is the most abundant maceral ranging from 56,.6% - 80.36% vol, liptinite (15.27% - 39.45% vol), inertinite (0.55% - 15.18% vol), and mineral matter (0.18% - 4.36% vol) which is dominated by pyrite. Based on maceral’s assemblages, coal’s microfacies divided into four groups are (1) telovitrinite-rich group, (2) detrovitrinite-rich group, (3) telovitrinite-liptinite-rich group, (4) inertinite-rich group. The basal section of seam AGM-B6 is characterized by detrovitrinite-rich group while seam AGM-B3, AGM-B4, and AGM-B5 are characterized by telovitrinite-liptinite-rich group. The middle section only represented the inertinite-rich group in seam AGM-B3, and the top section of the coal seams, except AGM-B6, is typically represented by the telovitrinite-rich group. The vertical profile of paleomire evolution shows a repetition of topogenous mire changing into ombrogenous mire and then back to topogenous mire. The paleomire type developed includes wet forest swamp, forested peatlands, and intermittently dry forested swamp and the environmental conditions are telmatic. The correlation between paleomire’s type and coal maceral’s abundance in the Kandangan area reflects that the type of vegetation from woody plants that underwent high degradation, moderate gelification, and intensive oxidation processes triggered by a short dry season.

Biomarker Reconstruction of a High‐Latitude Late Paleocene to Early Eocene Coal Swamp Environment Across the PETM and ETM‐2 (Ellesmere Island, Arctic Canada)

AbstractThe Paleocene‐Eocene Thermal Maximum (PETM) and early Eocene hyperthermal events were characterized by a Hothouse climate state. Our understanding of the climatic impact of these hyperthermals is currently biased toward marine settings and the mid‐latitudes. Here we present organic geochemical data from Stenkul Fiord, Ellesmere Island, Arctic Canada. This organic rich formation was deposited in a high northern latitude wetland setting during the late Paleocene to early Eocene, spanning the PETM and subsequent ETM‐2 hyperthermals. Biomarker data (e.g., diterpenoids), combined with published palynological data from the site, indicate Cupressaceae‐dominated vegetation. Biomarkers suggest that land plant composition remained fairly unchanged across the two hyperthermal events. Increases in abundance and 13C‐depletion of hopanoid biomarkers (minima <−50‰ (VPDB)) highlight periods of enhanced bacterial methane consumption, particularly during the PETM. However, periods of low hopanoid δ13C values were also found outside the hyperthermal intervals. Relatively low δ2H values of higher plant n‐alkanes (average δ2H values of n‐C25, n‐C27, n‐C29 ∼ −230 to −270‰ (SMOW)) indicate that deposition formed during times with enhanced precipitation. The wettest intervals, as identified by the lowest δ2H n‐alkane values, contain high abundances of hopenes, indicating enhanced bacterial turnover. At Stenkul Fiord, high temperatures and CO2 concentrations likely fostered the growth of widespread wetland forests that became a CO2 sink and may have played an important role in carbon drawdown during the Early Paleogene.

Geochemical variations of major, trace, rare earth elements in some Gondwana and Eocene coals of India with a comparison of their germanium, lithium, and mercury content

The geochemistry of major, trace, rare earth elements (REEs), with special reference to Ge, Li, and Hg in selected Gondwana and Eocene coals, has been studied. Major oxide and trace element ratios have been utilised to compare the tectonic setting, provenance of source rocks, and paleoweathering conditions that prevailed the during formation of these coals. The Gondwana coals have a higher mean mercury and ash content (244.5 μg/kg and 17.2 %, respectively) than the Eocene coals (142.1 μg/kg, 8.9 % respectively). The major oxides, SiO2, Fe2O3, and Al2O3, in Gondwana and Eocene coals, are enriched relative to the upper continental crust (UCC), Chinese and American coals. The UCC normalized trace element concentration coefficients of the Gondwana and Eocene coals show enrichment in Ge, Se, Th, Co, Mo, Sn, W, and Li. The mean Ge and Li concentrations (mg/kg) in Gondwana (106.7, 154.7) and Eocene (120.0, 252.6) exceed the corresponding values in world coal (2.2, and 12). The Rajmahal coals have the highest mean Ge concentration (168.8 mg/kg) among the Gondwana coals while Eocene coals from East Jaintia Hills have the highest mean value (343.7 mg/kg). The Gondwana coals have a higher mean As concentration (3.5 mg/kg) in comparison to the Eocene coals (1.9 mg/kg). The mean of the rare earth elements in Gondwana (24.1 mg/kg) is higher than that in Eocene coals (11.3 mg/kg) and these values are less than the World coals (68.5 mg/kg). Both the Gondwana and Eocene coals are enriched in light rare earth elements (LREEs). However, among the Eocene coals, the Meghalayan coals show REE enrichment in comparison to Assam coals. Both the Gondwana and Eocene coals were formed in warm and humid climates under oxic conditions with moderate weathering of the source rocks.

Coal deposition in the Barito Basin (Southeast Borneo): The Eocene Tanjung Formation compared to the Miocene Warukin Formation

Coal seams of Late Eocene (Tanjung Formation) and middle Miocene age (Warukin Formation) are present in the Barito Basin of Borneo. The seams are laterally continuous and can be traced over at least 20 km. The thickness of three Eocene seams in the TAJ Pit–1D mine ranges from 1.4 to 3.4 m. These seams (from base to top: D, C, B) were studied to reconstruct their peat–forming environment and to compare the characteristics of Eocene and Miocene coals. The comparison reveals differences in peat types, flora and climate. The study is based on 38 Eocene coal and six non–coal samples, each representing a stratigraphic interval of 0.2 m. The samples were analyzed for ash yield, carbon and sulphur contents, and maceral composition. Organic geochemical parameters (incl. biomarkers) were obtained on every second coal sample to obtain information on the peat-forming vegetation and its diagenetic alteration.The Eocene seams were deposited in rheotrophic mires with palm/fern–dominated vegetation. Transitions to local ombrotrophic mires cannot be excluded. Very low to low sulphur contents (max. 0.9 wt%) speak against a marine influence, despite a general coastal plain setting. Upward increasing sulphur contents in the lower seam D and the upper seam B are interpreted to reflect transgression, which ended peat accumulation. The seam C formed in a rheotrohpic seam with a relatively high water level. This favored the accumulation of aquatic plants.Miocene coals from the Warukin Formation in the Barito Basin were studied recently in a companion paper. The comparison of Eocene and Miocene coals shows major differences, which include: Miocene coals are significantly thicker (up to 50 m) and display a cyclic structure. Miocene coals accumulated in ombrotrophic mires dominated by more decay resistant angiosperm trees (and subordinate gymnosperms). Therefore, preserved plant tissues are more abundant in Miocene coals. In addition, Miocene coals contain a significantly higher amount of root–derived macerals (suberinite). Leaf–derived macerals (cutinite, fluorinite) and resinite are ubiquitous in Miocene coals, but even slightly more abundant in Eocene coals. At least part of the resinite in Miocene coals, but not in Eocene coals, is derived from dammar resin produced by Dipterocarpaceae. Fungal activity, recorded by high funginite percentages, was high in low-ash ombrotrophic and high-ash rheotrophic mires both in Eocene and Miocene times.

Eocene Paleoclimate Evolution under the Background of Warmhouse-Hothouse Conditions in the Continental Fushun Basin: Implications from Magnetic Susceptibility and Color Reflectance.

Paleocene–Eocene hyperthermal events are a current research focus in the fields of sedimentology and paleoclimatology. The Fushun Basin in northeast China contains continuous continental Eocene fine-grained rocks, and a series of Eocene hyperthermal events in the Fushun Basin have been identified. Because of the high cost of high-precision isotope data testing, it is necessary to find new and alternative paleoclimate parameters. In this study, Eocene coal and oil shale-bearing layers in the Fushun Basin are used as research objects. The high-precision data of magnetic susceptibility, color reflectance, rock composition, and cluster analyses are used to conduct a vertical comparison in the same category and compare that analysis with the identified Eocene hyperthermal events in the Fushun Basin. The preliminary results show that high-frequency-dependent susceptibility, high color reflectance a* (redness)/L* (lightness) values, and high kaolinite content in the study area have good correspondence with global hyperthermal events and can be used as effective parameters for the identification of continental basin hyperthermal events. The detailed magnetic susceptibility and color reflectance data also reveal that the Eocene strata in the Fushun Basin recorded the Late Lutetian Thermal Maximum (LLTM) and 13 short-term hyperthermal events during the Early Eocene Climatic Optimum (EECO). These results indicate that the parameters of rock physical properties can be used to study the evolution of the paleoclimate in geological history, and it has universal practicability in continental and marine fine-grained sedimentary rocks.

Abundance of Sulphur in Paleogene coals of North-East India and Its Paleo-environmental Implications

The present paper entails the occurrence and distribution of different forms of sulphur in Paleogene coals of north-eastern India. All the coal seams present in the north-eastern region of India are characterized by the presence of high sulphur with total sulphur content ranging from 3 to 7%. Among all the forms of sulphur recognised, organic sulphur is dominant. The total sulphur content originated in the Platform area for Eocene coal under stable shelf condition vary from 4.20 % to 6.01 % for Jaintia Hills, from 2.78 % to 4.01 % for Khasi Hills and from 1.90 % to 3.00 % for Garo Hills, whereas Oligocene coal evolved under the foredeep basin have total sulphur ranging in from 2.90 % and 6.60 %. In the Eocene coals, there is a distinct lateral and vertical variation of sulphur i.e., sulphur content increases from the bottom to the top seam and also from western side of Meghalaya to the eastern side. This lateral variation of sulphur was because of the more marine nature of the Eastern Meghalaya than the Western Meghalaya. Both Eocene and Oligocene coals have been derived from seawater as evidenced by the presence of pyritic form of sulphur. Study of forms of sulphur also suggests that the deposition of the coals in a different part of the region was influenced by roof strata, peat-forming plant communities, tectonic uplifting, and marine or freshwater incursion.

Petrographic Characterization and evolution of Eocene Coal from Bapung coalfield, East Jaintia Hills, Meghalaya, North-East India

The Bapung coalfield in the East Jaintia Hills of Meghalaya belongs to the Shella Formation of Jaintia Group and is of Eocene age. Thinly bedded seams of about 1 m thick are vastly exposed in the Bapung area. The present study includes petrographic and geochemical characterization of these coals. This study reveals that the Bapung coals are sub-bituminous ‘A’ to high volatice bituminous ‘C’ in rank. These coals are perhydrous in nature with moderately high volatile matter content. The sulphur content is high in these coals having pyrite as the most abundant mineral. Vitrinite is the dominant maceral group constituting nearly 76.5-82.6% of the entire group macerals, while inertinite occurs in subordinate amount and liptinite concentration is insignificant. Facies-critical models used to decipher the paleodepositional environment suggest that anoxic moor condition dominantly prevailed in the paleomire and there was association of peat with brackish water condition which allowed the sulphate reducing bacteria to thrive.

Geological setting and facies distribution of mengen eocene coal deposits, Bolu, NW-Turkey

Geological setting and facies distribution of mengen eocene coal deposits, Bolu, NW-Turkey

A study of geochemical and petrographic characteristics of Eocene coal from Bapung coalfield, East Jaintia Hills, Meghalaya, North East India

A study of geochemical and petrographic characteristics of Eocene coal from Bapung coalfield, East Jaintia Hills, Meghalaya, North East India

Depositional environment of Upper Paleocene – Middle Eocene series of the Lesser Himalaya, Central Nepal

Paleocene–Eocene epoch was the turning point when the Indian subcontinent experienced maximum isolation before it collided with Eurasia. Intense sedimentation occurred in late Paleocene in the foreland basins of young Himalaya, marking the beginning of a major transgression on the Indian subcontinent. In central Himalaya (Nepal), the synorogenic stratigraphy recorded the depositional environment changes from salt-water to brackish-water and even to fresh-water condition, indicating slight and gradual regressive phase. We report petrography, U–Pb detrital zircons ages, whole-rock geochemistry data from sandstone in Cretaceous–Paleocene, Eocene, and lower Miocene of the Lesser Himalaya, central Nepal. The Eocene and Miocene sequences have small Neoproterozoic to Cambrian age zircon populations indicating multiple source terrains. The whole-rock geochemistry supports the unroofing history documented by U–Pb zircon ages, the succession belongs to foreland basin, an area between the active and passive continental margins tectonic setting. Petrography data indicates a recycled orogenic provenance.For the first time, we identify the Eocene coal was deposited in tropical and humid conditions based on fauna and flora, geochemistry, fission-track, and Zircon-Helium (ZHe) age. The organic geochemical and organic petrological data suggests the depositional environment of Jhadewa coal of central Nepal in anoxic terrestrial condition signifying a peat-swamp flood basin environment. Therefore, we suggest that the studied coal is formed from ancient submerged peat forests in swampy environments subjected to the geological forces of heat and pressure over millions of years and the tectonic collision might have played an essential role for burial and formation of lignite to bituminous coal.

Changes in chemistry of vitrinite in coal through time: Insights from organic functional group characteristics

Is the signature of the original plant communities preserved in coal, or is that signature overprinted by depositional and diagenetic processes? To address this question, Pennsylvanian coals from the Illinois and Appalachian basins were compared to Cretaceous, Paleocene, and Eocene coals of comparable coalification levels as shown by vitrinite reflectance. Three reflectance intervals—0.52–0.55, 0.58–0.62, and 0.68–0.71%—were considered, and in total 51 samples were analyzed. Although data on proximate and ultimate analyses and petrographic composition were compared on whole coal samples, the maceral vitrinite was the main target of this comparison because’ aside from being the dominant component of all the samples, it offers the best chance to preserve the signature of the original woody material. An in-situ micro-FTIR technique was used to collect data on the functional group distribution of vitrinite, and FTIR-derived parameters were compared between different age groups with a special emphasis on the differences between Pennsylvanian and the Cretaceous vitrinite. The main difference between Cretaceous and Pennsylvanian coals is reflected in their oxygen content, which is higher for the Cretaceous coals. On the functional group level, the only significant difference was detected in the CH2/CH3 ratio, which had higher values for vitrinite in the Cretaceous samples. Other parameters both within the coal and the vitrinite showed comparable scatter within age groups as those between the age groups. It is suggested that oxygen content in coal and CH2/CH3 ratio in vitrinite reflect differences in the original biomass, and the variations in other parameters such as C, H, N, volatile matter, calorific value, or the majority of FTIR-derived parameters are a function of both depositional and post-depositional factors.

Marine influence during deposition of the Kiliranjao Brown Shale, Central Sumatra, from palynology point of view

The Eocene to Oligocene succession of the Kiliranjao Brown Shale was deposited in a lacustrine environment. This study combines palynological analysis and XRD analysis technique to investigate the possibility of marine influence during deposition of Kiliranjao lacustrine shale. Two biostratigraphic zonations of Karbindo section are Middle to Late Eocene Proxapertites operculatus Zone and Oligocene Meyeripollis naharkotensis Zone. The marine flooding surface, as shown by the peak of the abundance of mangrove pollen, is used to delineate the section into five parasequences. The tripartite stratigraphic architecture of Karbindo section is consists of early rift deposit (TS1), syn-rift deposit (TS2), and syn-rift deposit (TS3). Middle to Late Eocene coal and limestone facies (parasequence I) represents the TS1. Late Eocene to Oligocene parasequence II to IV (below MFS) shows the TS2 (deepening-upward lacustrine succession), and the shallowing-upward lacustrine succession of Oligocene parasequence V (above MFS) indicate the TS3. The abundance of mangrove and back mangrove palynomorph assemblages and the high amount of carbonate mineral from XRD analysis are the evidence of marine influence to the deposition of Karbindo section Brown Shale. The marine incursion to the lacustrine environment occurred from the adjacent nearby open sea, that separated by shoal area, which can submerge below sea level during a marine transgressive event. Marine incursion events did contribute to the deposition of Kiliranjao Brown Shale though further work is still needed.

Organic Geochemistry, Petrography, Depositional Environment and Hydrocarbon Potential of the Eocene Coal Deposits of west Daranggiri Coalfield, Meghalaya

Abstract The Eocene coal deposits of west Daranggiri coalfield of Meghalaya is hosted in the Tura Formation. The coals are perhydrous in composition, rich in organic matters and poor in mineral content. The organic matters are dominantly represented by Type III kerogens contributed by terrestrial plants. Petrographic analysis confirms dominance of vitrinite with subordinate amounts of liptinite and inertinite. Maturity parameters like vitrinite reflectance, Rock-Eval Tmax, volatile matter content etc. indicate low thermal maturity of the coal within lignite to subbituminous rank. The coals are immature to act as petroleum source rock despite having high-quality organic matters. However, perhydrous nature of the organic matters and significant amount of liptinite macerals suggest that despite low thermal maturity, the coals might have some capacity to generate liquid hydrocarbon. High liptinite and perhydrous vitrinite contents of the coal may result in suppression of vitrinite reflectance, thus, underestimation of maturity. Presence of exsudatinite in the coal also points to generation of some liquid hydrocarbon. The coal deposits possess excellent potential for hydrogenation industry. The coals are characterized by very high rate of conversion from coal to oil and high oil yield. Indices of facies critical maceral association indicate the origin of the coal in wet swamps under mildly oxic to the anoxic environment with moist hydrodynamic condition. The high sulphur content of the coal, association of marine palynological assemblage and presence of limestone beds at the top of the Tura Formation point to nearshore environment of deposition.

Plant and insect herbivore community variation across the Paleocene-Eocene boundary in the Hanna Basin, southeastern Wyoming.

Ecosystem function and stability are highly affected by internal and external stressors. Utilizing paleobotanical data gives insight into the evolutionary processes an ecosystem undergoes across long periods of time, allowing for a more complete understanding of how plant and insect herbivore communities are affected by ecosystem imbalance. To study how plant and insect herbivore communities change during times of disturbance, we quantified community turnover across the Paleocene­–Eocene boundary in the Hanna Basin, southeastern Wyoming. This particular location is unlike other nearby Laramide basins because it has an abundance of late Paleocene and Eocene coal and carbonaceous shales and paucity of well-developed paleosols, suggesting perpetually high water availability. We sampled approximately 800 semi-intact dicot leaves from five stratigraphic levels, one of which occurs late in the Paleocene–Eocene thermal maximum (PETM). Field collections were supplemented with specimens at the Denver Museum of Nature & Science. Fossil leaves were classified into morphospecies and herbivore damage was documented for each leaf. We tested for changes in plant and insect herbivore damage diversity using rarefaction and community composition using non-metric multidimensional scaling ordinations. We also documented changes in depositional environment at each stratigraphic level to better contextualize the environment of the basin. Plant diversity was highest during the mid-late Paleocene and decreased into the Eocene, whereas damage diversity was highest at the sites with low plant diversity. Plant communities significantly changed during the late PETM and do not return to pre-PETM composition. Insect herbivore communities also changed during the PETM, but, unlike plant communities, rebound to their pre-PETM structure. These results suggest that insect herbivore communities responded more strongly to plant community composition than to the diversity of species present.

A predictive algorithm for wetlands in deep time paleoclimate models

Abstract. Methane is a powerful greenhouse gas produced in wetland environments via microbial action in anaerobic conditions. If the location and extent of wetlands are unknown, such as for the Earth many millions of years in the past, a model of wetland fraction is required in order to calculate methane emissions and thus help reduce uncertainty in the understanding of past warm greenhouse climates. Here we present an algorithm for predicting inundated wetland fraction for use in calculating wetland methane emission fluxes in deep-time paleoclimate simulations. For each grid cell in a given paleoclimate simulation, the algorithm determines the wetland fraction predicted by a nearest-neighbour search of modern-day data in a space described by a set of environmental, climate and vegetation variables. To explore this approach, we first test it for a modern-day climate with variables obtained from observations and then for an Eocene climate with variables derived from a fully coupled global climate model (HadCM3BL-M2.2; Valdes et al., 2017). Two independent dynamic vegetation models were used to provide two sets of equivalent vegetation variables which yielded two different wetland predictions. As a first test, the method, using both vegetation models, satisfactorily reproduces modern day wetland fraction at a course grid resolution, similar to those used in paleoclimate simulations. We then applied the method to an early Eocene climate, testing its outputs against the locations of Eocene coal deposits. We predict global mean monthly wetland fraction area for the early Eocene of 8×106 to 10×106 km2 with a corresponding total annual methane flux of 656 to 909 Tg CH4 yr−1, depending on which of the two different dynamic global vegetation models are used to model wetland fraction and methane emission rates. Both values are significantly higher than estimates for the modern day of 4×106 km2 and around 190 Tg CH4 yr−1 (Poulter et al., 2017; Melton et al., 2013).

Study of microstructure, maceral and mineral matter in two different coals of the Nepal Himalaya

The Eocene coals from the western (Tosh coalfield) and central regions (Jhadewa coalfield) of the Nepal Himalaya have been studied under the petrological and the Scanning Electron Microscopes to explain the mode of occurrence of mineral matter and their microstructural relations with organic constituents. As shown by the results of the coal samples, three kinds of coals in diminishing abundance are moderately dull coal, moderately bright coal and bright coal. Distribution of mineral matter in the Eocene coals shows that the bright coal is rare in western Nepal and the moderately bright coal is abundant in central Nepal. Mineral matter in moderately dull coals contains superficial impregnating and cavity filling. Mineral matter in bright coals contains superficial mounting and pore fillings, but in moderately bright coals contains superficial impregnating, cavity filling, and intimate intergrowth. Mineral matters in
 moderately dull coals, moderately bright coals and bright coals respectively range from 38.27 to 47.12 vol%, 12.31 and 15.73 vol%, and 12.31 and 15.73 vol%. The Jhadewa coalfield (central Nepal) contains more macerels than the Tosh coalfield (western Nepal), whereas the Tosh coalfield contains more mineral matter than the Jhadewa coalfield. The results indicate two different origins for coal deposits from two different regions.

Classification and Potential Utilization of Eocene Coals of Meghalaya, North East India

ABSTRACT In the present study, petrographic and geochemical investigation of Meghalayan coal deposits have been carried out to classify these coals in terms of rank, type and grade, using Indian and International classification schemes. Based on petrographic and geochemical characteristics, an attempt has also been made to identify the potential utilization of Meghalayan coals for various industrial applications. According to the study, these coals have been classified as sub-bituminous C to high volatile bituminous in rank, vitric in type and clean to ashy in grade. Considering their hydrocarbon potential, these coals are suitable for liquefaction and gasification.

Structural investigations of Eocene coals from foreland basin of central Nepal Himalaya

Structural investigations of Eocene coal from foreland basin of central Nepal Himalaya were subjected to attenuated total reflection Fourier transform infrared spectroscopy, X-ray diffraction, high-resolution transmission electron microscopy and scanning electron microscopy to study their chemical and structural characteristics. The attenuated total reflection Fourier transform infrared spectroscopy data show that the less matured coal sample (sub-bituminous) has more aliphatic moieties, whereas the relatively more matured (bituminous) coal samples contain higher fractions of poly-aromatic moieties and saturated long-chain hydrocarbons. Fourier transform infrared spectroscopy spectra reveals the presence of stretching vibrations of aliphatic –CH, –CH2 and –CH3 absorptions, –OH bonds, C=C and –CH of aromatic structures and C=O stretching vibrations of carbonyl groups. X-ray diffraction indicates the presence of crystalline carbon having turbostratic structure along with some highly disordered amorphous car...

An overview on source rocks and the petroleum system of the central Upper Rhine Graben

The petroleum system of the Upper Rhine Graben (URG) comprises multiple reservoir rocks and four major oil families, which are represented by four distinct source rock intervals. Based on geochemical analyses of new oil samples and as a review of chemical parameter of former oil fields, numerous new oil–source rock correlations were obtained. The asymmetric graben resulted in complex migration pathways with several mixed oils as well as migration from source rocks into significantly older stratigraphic units. Oldest oils originated from Liassic black shales with the Posidonia Shale as main source rock (oil family C). Bituminous shales of the Arietenkalk-Fm. (Lias α) show also significant source rock potential representing the second major source rock interval of the Liassic sequence. Within the Tertiary sequence several source rock intervals occur. Early Tertiary coaly shales generated high wax oils that accumulated in several Tertiary as well as Mesozoic reservoirs (oil family B). The Rupelian Fish Shale acted as important source rock, especially in the northern URG (oil family D). Furthermore, early mature oils from the evaporitic-salinar Corbicula- and Lower Hydrobienschichten occur especially in the area of the Heidelberg-Mannheim-Graben (oil family A). An overview on potential source rocks in the URG is presented including the first detailed geochemical source rock characterization of Middle Eocene sediments (equivalents to the Bouxwiller-Fm.). At the base of this formation a partly very prominent sapropelic coal layer or coaly shale occurs. TOC values of 20–32 % (cuttings) and Hydrogen Index (HI) values up to 640–760 mg HC/g TOC indicate an extraordinary high source rock potential, but a highly variable lateral distribution in terms of thickness and source rock facies is also supposed. First bulk kinetic data of the sapropelic Middle Eocene coal and a coaly layer of the ‘Lymnaenmergel’ are presented and indicate oil-prone organic matter characterized by low activation energies. These sediments are considered as most important source rocks of numerous high wax oils (oil family B) in addition to the coaly source rocks from the (Lower) Pechelbronn-Schichten (Late Eocene). Migration pathways are significantly influenced by the early graben evolution. A major erosion period occurred during the latest Cretaceous. The uplift center was located in the northern URG area, resulting in SSE dipping Mesozoic strata in the central URG. During Middle Eocene times a second uplift center in the Eifel area resulted in SW-NE-directed shore lines in the central URG and contemporaneous south-southeastern depocenters during marine transgression from the south. This structural setting resulted in a major NNW-NW-directed and topography-driven migration pattern for expelled Liassic oil in the fractured Mesozoic subcrop below sealing Dogger α clays and basal Tertiary marls.

Organic geochemistry and element distribution in coals formed in Eocene lagoon facies from the Eastern Black Sea Region, NE Turkey

The amount and type, the inorganic element content, and the maturity of organic materials of Eocene coals, shaly coals, and coaly shales exposed in the Gümüşhane and Bayburt districts of the Eastern Black Sea Region of Turkey were investigated. The depositional environments and hydrocarbon potentials were also interpreted. The total organic carbon concentrations in the studied samples ranged from 0.50% to 63.08%. The samples from Özyurt, Kayadibi, and Tarhanas contained types II and III kerogen, and those from Sökmen and Manas contained type III kerogen. The samples contained Co, Cs, Ga, Hf, Th, U, Y, Mo, Be, Cd, Sb, and La, with average values similar to those of standard brown coals. The samples showed average contents of Co, Ga, Nb, Rb, V, Y, Cu, Pb, Zn, As, Be, and Se, similar to those of other Turkish coals. The sediment source of Eocene samples in the five areas was characterized by rocks with intermediate or mafic geochemical characteristics. The terrigenous/aquatic ratio of coal and shaly coal samples of the areas in question is >1. The sterane distribution was C29 > C28 > C27 and C29 > C27 > C28 for the Özyurt and Tarhanas areas, respectively. The average Tmax values for samples are between 424 °C and 460 °C. For samples Oz-1 and Ta-2, 22S/(22S + 22R) homohopane (C32) ratios are 0.48 and 0.61, respectively; 20S/(20S + 20R) sterane (C29) ratios are 0.18 and 0.53, respectively; and Ts/(Ts + Tm) ratios are 0.015 and 0.64, respectively. The Pr/Ph ratios of the samples are >3. The studied samples have low sterane/hopane and high (C19+C20)/C23) ratios without anoxic biomarkers (17α(H)-28,30-bisnorhopane). Based on these data, the coals, shaly coals, and coaly shales were probably deposited under an oxic-suboxic mixture of marine and terrestrial environment conditions; these materials contain terrestrial organic matter and cannot generate hydrocarbon.