Biomarkers geochemistry of the Alpagut oil shale sequence: an evaluation of dispositional environments and source rock potential from Dodurga-Çorum basin (N-Turkey)

The Cenozoic Çankırı-Çorum basin, with sedimentary facies of varying thickness and distribution, contains raw matters such as coal deposits, oil shales and evaporate. Source rock and sedimentary environment characteristics of the oil shale sequence have been evaluated. The studied oil shales have high organic matter content (from 2.97 to 15.14%) and show excellent source rock characteristics. Oil shales are represented by very high hydrogen index (532–892 mg HC/g TOC) and low oxygen index (8–44 mgCO2/g TOC) values. Pyrolysis data indicate that oil shales contain predominantly Type I and little Type II kerogen. The biomarker data reveal the presence of algal, bacterial organic matter and terrestrial organic matter with high lipid content. These findings show that organic matters in the oil shales can generate hydrocarbon, especially oil. High C26/C25, C24/C23 and low C22/C21 tricyclic terpane, C31R/C30 hopane and DBT/P ratios indicate that the studied oil shales were deposited in a lacustrine environment, and very low Pr/Ph ratio is indicative of anoxic character for the depositional environment. Tmax values from the pyrolysis analysis are in the range of 418–443 °C, and production index ranges from 0.01 to 0.08. On the gas chromatography, high Pr/nC17 and Ph/nC18 ratios and CPI values significantly exceeding 1 were determined. Very low 22S/(22S + 22R) homohopane, 20S/(20S + 20R) sterane, diasterane/sterane and Ts/(Ts + Tm) ratios were calculated from the biomarker data. Results of all these analyses indicate that Alpagut oil shales have not yet matured and have not entered the oil generation window.

The Biodegradation of Soil Organic Matter in Soil-Dwelling Humivorous Fauna

Soil organic matter contains more carbon than global vegetation and the atmosphere combined. Gaining access to this source of organic carbon is challenging and requires at least partial removal of polyphenolic and/or soil mineral protections, followed by subsequent enzymatic or chemical cleavage of diverse plant polysaccharides. Soil-feeding animals make significant contributions to the recycling of terrestrial organic matter. Some humivorous earthworms, beetles, and termites, among others, have evolved the ability to mineralize recalcitrant soil organic matter, thereby leading to their tremendous ecological success in the (sub)tropical areas. This ability largely relies on their symbiotic associations with a diverse community of gut microbes. Recent integrative omics studies, including genomics, metagenomics, and proteomics, provide deeper insights into the functions of gut symbionts. In reviewing this literature, we emphasized that understanding how these soil-feeding fauna catabolize soil organic substrates not only reveals the key microbes in the intestinal processes but also uncovers the potential novel enzymes with considerable biotechnological interests.

Microporphyritic and microspherulitic melt grains, Hiawatha crater, Northwest Greenland: Implications for post-impact cooling rates, hydration, and the cratering environment

Sand-sized impactite melt grains hand-picked from a glaciofluvial sample proximal to the Hiawatha impact crater in Northwest Greenland contain new information about the crystallization and cooling history of this impact structure, which is concealed by the Greenland Ice Sheet. Of course, the original locations of the individual sand grains are unknown, but this is offset by the substantial number and wide variety of impactite grains available for study. A detailed investigation of 16 melt grains shows that post-cratering crystallization took place under very variable conditions of strong undercooling with temperatures that dropped rapidly from high above their solidus to far below. A distinct event of near-isochemical hydration at above or ∼250 °C is recorded by intense perlitic fracturing and the growth of closely packed mordenite spherulites only 1−3 μm across in felsic melt grains, which was followed by lower temperature hydrothermal alteration along the pre-existing perlitic fractures. The formation of abundant mordenite microspherulites appears to be very rare or not previously recorded in impactite melts and suggests the rapid infilling of the Hiawatha crater by a hydrous source. The infilling did not occur immediately after the impact as in submarine impacts, but soon thereafter, and before the establishment of a low-temperature hydrothermal alteration system common to the waning stage of cooling in many impact structures. These observations and previous documentation of terrestrial organic matter in the impactites are consistent with an impact into a water-rich terrestrial environment, such as through the Greenland Ice Sheet or into a forested, lacustrine−fluvial region.

Changing depositional environments in the semi-restricted Late Jurassic Lemeš Basin (Outer Dinarides; Croatia)

The up to 450 m-thick Upper Jurassic Lemeš Formation includes organic-rich deep-water (max. ~ 300 m) sedimentary rocks deposited in the Lemeš Basin within the Adriatic Carbonate Platform (AdCP). The Lemeš Formation was investigated regarding (1) bio- and chemostratigraphy, (2) depositional environment, and (3) source rock potential. A multi-proxy approach—microfacies, Rock–Eval pyrolysis, maceral analysis, biomarkers, and stable isotope ratios—was used. Based on the results, the Lemeš Formation is subdivided from base to top into Lemeš Units 1–3. Deposition of deep-water sediments was related to a late Oxfordian deepening event causing open-marine conditions and accumulation of radiolarian-rich wackestones (Unit 1). Unit 2, which is about 50 m thick and Lower early Kimmeridgian (E. bimammatum to S. platynota, ammonite zones) in age, was deposited in a restricted, strongly oxygen-depleted basin. It consists of radiolarian pack- and grainstones with high amounts of kerogen type II-S organic matter (avg. TOC 3.57 wt.%). Although the biomass is predominantly marine algal and bacterial in origin, minor terrestrial organic matter that was transported from nearby land areas is also present. The overlying Unit 3 records a shallowing of the basin and a return to oxygenated conditions. The evolution of the Lemeš Basin is explained by buckling of the AdCP due to ophiolite obduction and compressional tectonics in the Inner Dinarides. Lemeš Unit 2 contains prolific oil-prone source rocks. Though thermally immature at the study location, these rocks could generate about 1.3 t of hydrocarbon per m2 surface area when mature.

Trace Metal Variations through the Tartan and Waipawa Formations: Implications for the Environment of Deposition

<p>An inorganic geochemical study of the Late Paleocene organic matter-rich Waipawa and Tartan formations was undertaken in order to investigate the depositional environment. The formation varies in thickness between 2 and 50 metres and is distributed across many of New Zealand’s Cenozoic basins, where it forms an important potential hydrocarbon source rock. This study measured major and trace elements which can be loosely grouped into redox sensitive, biologically influenced, terrestrially sourced, and rare earth elements (REE). The study focused on three sections through the Waipawa and Tartan formations: Angora Quarry in the East Coast Basin, and the Great South Basin hydrocarbon exploration wells Kawau-1A and Pakaha-1. At Angora Quarry, x-ray fluorescence (XRF) was used to measure the major constituents Na₂O, MgO, Al₂O₃, SiO₂, P₂O₅, SO₃, K₂O, CaO, TiO₂, MnO and Fe₂O₃. inductively-coupled plasma mass spectrometry (ICP-MS) was used to measure Li, Ca, Ti, V, Cr, Co, Ni, Cu, Zn, Ga, Ge, As, Rb, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Ba, REE, Hf, Tl, Pb, Th and U. For Pakaha-1 and Kawau-1A side wall core samples, ICP-MS was used to measure Ti, V, Cr, Mn, Co, Ni, Cu, As, Se, Rb, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Hf, Ta, W, Tl, Pb, Bi, Th and U. Insufficient sample was available for XRF on these samples. No major changes in oxygen concentration during deposition were recorded by redox-sensitive elements from Angora Quarry and Pakaha-1 sediments; however samples from Kawau-1A and from a section 1 km upstream from Angora Quarry were deposited under somewhat oxygen-depleted conditions. As the anoxic and suboxic indicators show significantly lower variations than under present day anoxic environments, and in Angora Quarry CaO and SO₃ are significantly depleted with higher aluminosilicates a rapid deposition is required to explain the preservation of the organic matter. In the Great South Basin wells, the clay content correlates directly with increased gamma ray levels measured by well logs. Increased influx of terrestrial clays has been linked to marine transgressions in many New Zealand sediments and is been taken to mean the same for the Waipawa and Tartan formations. The oxygen depletion indicates that water depths during deposition exceeded 50 metres. The depositional model proposed here, therefore, is that of a major marine transgression that flooded and eroded near-shore swamps, re-depositing the terrestrial organic matter offshore. The increased nutrients released by this would have stimulated bioproductivity and locally, where conditions were suitable, depleted the oxygen content of the water column. This study also suggests ternary diagrams are valuable for calculating the enrichment of elements affected by two processes, such as Sr, which is related to both detrital Al and related to biological Ca. Ga, Ba and Al content are also related on a ternary diagram indicating the similar terrestrial and biological relationships for Ba and Ga. W was found to behave in a similar way to Bi. Enrichment factors proved less useful than absolute enrichment for Kawau-1A, where detrital input varied greatly and was found to be significantly different in composition to average shale as defined by Wedephol (1971).</p>

Trace Metal Variations through the Tartan and Waipawa Formations: Implications for the Environment of Deposition

<p>An inorganic geochemical study of the Late Paleocene organic matter-rich Waipawa and Tartan formations was undertaken in order to investigate the depositional environment. The formation varies in thickness between 2 and 50 metres and is distributed across many of New Zealand’s Cenozoic basins, where it forms an important potential hydrocarbon source rock. This study measured major and trace elements which can be loosely grouped into redox sensitive, biologically influenced, terrestrially sourced, and rare earth elements (REE). The study focused on three sections through the Waipawa and Tartan formations: Angora Quarry in the East Coast Basin, and the Great South Basin hydrocarbon exploration wells Kawau-1A and Pakaha-1. At Angora Quarry, x-ray fluorescence (XRF) was used to measure the major constituents Na₂O, MgO, Al₂O₃, SiO₂, P₂O₅, SO₃, K₂O, CaO, TiO₂, MnO and Fe₂O₃. inductively-coupled plasma mass spectrometry (ICP-MS) was used to measure Li, Ca, Ti, V, Cr, Co, Ni, Cu, Zn, Ga, Ge, As, Rb, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Ba, REE, Hf, Tl, Pb, Th and U. For Pakaha-1 and Kawau-1A side wall core samples, ICP-MS was used to measure Ti, V, Cr, Mn, Co, Ni, Cu, As, Se, Rb, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Hf, Ta, W, Tl, Pb, Bi, Th and U. Insufficient sample was available for XRF on these samples. No major changes in oxygen concentration during deposition were recorded by redox-sensitive elements from Angora Quarry and Pakaha-1 sediments; however samples from Kawau-1A and from a section 1 km upstream from Angora Quarry were deposited under somewhat oxygen-depleted conditions. As the anoxic and suboxic indicators show significantly lower variations than under present day anoxic environments, and in Angora Quarry CaO and SO₃ are significantly depleted with higher aluminosilicates a rapid deposition is required to explain the preservation of the organic matter. In the Great South Basin wells, the clay content correlates directly with increased gamma ray levels measured by well logs. Increased influx of terrestrial clays has been linked to marine transgressions in many New Zealand sediments and is been taken to mean the same for the Waipawa and Tartan formations. The oxygen depletion indicates that water depths during deposition exceeded 50 metres. The depositional model proposed here, therefore, is that of a major marine transgression that flooded and eroded near-shore swamps, re-depositing the terrestrial organic matter offshore. The increased nutrients released by this would have stimulated bioproductivity and locally, where conditions were suitable, depleted the oxygen content of the water column. This study also suggests ternary diagrams are valuable for calculating the enrichment of elements affected by two processes, such as Sr, which is related to both detrital Al and related to biological Ca. Ga, Ba and Al content are also related on a ternary diagram indicating the similar terrestrial and biological relationships for Ba and Ga. W was found to behave in a similar way to Bi. Enrichment factors proved less useful than absolute enrichment for Kawau-1A, where detrital input varied greatly and was found to be significantly different in composition to average shale as defined by Wedephol (1971).</p>

Biomarker Characterization of Oil Seepages in Tomori Basin, Central Sulawesi, Indonesia

Tomori Basin is located close to the Banggai Basin which has several productive oil fields. Further investigation of the hydrocarbon potential in Tomori Basin is an important issue as potential hydrocarbon resources are indicated by the discovery of several oil seepages in the area. This study identified Tomori Basin oil seepage characteristics using a biomarker analysis approach. The Wosu and Kolo Areas were the main objectives of this study. Oil seepage characteristics were determined using Gas Chromatography (GC) and Gas Chromatography-Mass Spectrometry (GC-MS) methods to generate biomarker data which could be analysed to identify organic matter origin, oxic and anoxic conditions, source facies, or depositional environment. Based on the GC analysis of is oprenoids, the Pristane C19/Phytane C20 ratio (Pr/Ph) of Wosu Oil was 0.75, indicating anoxic conditions typical of a hypersaline environment. Kolo Oil had a Pr/Ph ratio of 3.37 indicative of terrestrial organic input under oxic conditions. A cross plot between Pristane/nC17 and Pr/Ph ratios indicates that Wosu Oil derives from a highly anoxic environment with algae/bacterial organic matter input whereas Kolo Oil derives from a suboxic-oxic environment dominated by terrestrial organic matter input. Trycyclic terpene analysis from C19 to C25 shows Wosu Oil seepages tend to originate from an environment of mixed terrestrial and marine organic matter (transitional environment). Overall, biomarker characteristics indicate that Wosu Oil originated from organic matter in a hypersaline and anoxic environment, whereas Kolo Oil originated from terrestrial matter in a suboxic – oxic environment.

Phytoplankton Fuel Fish Food Webs in a Low-Turbidity Temperate Coastal Embayment: A Stable Isotope Approach

Trophic contributions of diverse OM sources to estuarine and coastal food webs differ substantially across systems around the world, particularly for nekton (fish, cephalopods, and crustaceans), which utilize basal resources from multiple sources over space and time because of their mobility and feeding behaviors at multiple trophic levels. We investigated the contributions of putative OM sources to fish food webs and assessed the spatiotemporal patterns, structures, and trophic connectivity in fish food webs across four seasons from three closely spaced (10–15 km) sites: an estuarine channel (EC), a deep bay (DB), and an offshore (OS) region in Gwangyang Bay, a high-productivity, low-turbidity estuarine embayment off the Republic of Korea. While nearly all previous studies have focused on few representative species, we examined δ13C and δ15N values of whole nekton communities along with dominant benthic macro-invertebrates, zooplankton, and their putative primary food sources. The δ13C and δ15N values coupled with MixSIAR, a Bayesian mixing model, revealed that these communities utilized multiple primary producers, but phytoplankton comprised the primary trophic contributor (46.6–69.1%). Microphytobenthos (15.8–20.4%) and the seagrass Zostera marina (8.6–19.8%) made substantial contributions, but the role of river-borne terrestrial organic matter was negligible. Spatially different species composition and stable isotope values, but higher utilization of coastal phytoplankton by estuarine fish, indicated disparate food webs structures between the EC and DB/OS coastal areas, with considerable trophic connectivity. Greater overlaps in fish and cephalopod isotopic niches than among other consumers and a higher estimated carbon trophic enrichment factor for EC nekton confirmed feeding migration-mediated biological transport of coastal OM sources to the estuary. Further, the seasonally consistent structures and resource utilization patterns indicate that fish food webs are resilient to changes at lower trophic levels. Our results contrast with those for other highly turbid coastal systems depending highly on diversified basal sources, including exported terrestrial and wetland detritus alongside autochthonous phytoplankton. Finally, this study provides a novel perspective on the role of OM sources in such low turbidity and highly productive coastal embayments and enhances our understanding of marine ecosystems.