Geochemistry and depositional history of the Union Springs Member, Marcellus Formation in central Pennsylvania

2015 ◽  
Vol 3 (3) ◽  
pp. SV17-SV33 ◽  
Author(s):  
Anna K. Wendt ◽  
Mike A. Arthur ◽  
Rudy Slingerland ◽  
Daniel Kohl ◽  
Reed Bracht ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Water Column ◽  
Appalachian Basin ◽  
Depositional Environments ◽  
Source Rocks ◽  
Geochemical Data ◽  
Inorganic Elements ◽  
Central Pennsylvania ◽  
Marcellus Formation

Debate continues over paleoenvironmental conditions that prevail during deposition of organic-carbon (C)-rich marine source rocks in foreland basins and epicontinental seas. The focus of disagreement centers largely on paleowater depth and the prevalence of anoxia/euxinia. The issues of paleodepth and water column conditions are important for prediction of lateral variations in source quality within a basin because the viability of a hydrocarbon play depends on a thorough understanding of the distribution of source rock quality and depositional environments. We used inorganic geochemical data from the Middle Devonian Marcellus Shale in the Appalachian Basin to illustrate interpretive strategies that provided constraints on conditions during deposition. Source evaluation typically relies on the analysis and interpretation of organic geochemical indicators, potentially also providing evidence of the degree of thermal maturity and conditions of the preservation of the organic matter. The Marcellus Formation is thermally mature, making the evaluation of the organic-carbon fraction for geologic interpretation inadequate. Because most labile organic matter has largely been destroyed in the Marcellus Formation, analysis of inorganic elements may be used as an alternative interpretative technique. Several inorganic elements have been correlated to varying depositional settings, allowing for their use as proxies for understanding the paleodepositional environments of formations. A high-resolution geochemical data set has been constructed for the Union Springs Member along a transect of cores from proximal to distal in the Appalachian Basin in central Pennsylvania using major, minor, and trace elemental data. Our results suggested that during deposition, the sediment-water interface, and a portion of the water column, was anoxic to euxinic. As deposition continued, euxinia was periodically interrupted by dysoxia and even oxic conditions, and a greater influx of clastic material occurred. Such variations were likely related to fluctuations in water depth and progradation of deltaic complexes from the eastern margin of the Appalachian Basin.

scholarly journals Analyses of depositional environments of the Marcellus formation in New York using biomarker and trace metal proxies

2021 ◽  
Author(s):  
Reilly M. Blocho ◽  
Richard W. Smith ◽  
Mark R. Noll
Keyword(s):  
Fatty Acids ◽  
New York ◽  
Organic Matter ◽  
New York State ◽  
Depositional Environments ◽  
Average Chain Length ◽  
Lipid Biomarker ◽  
Two Samples ◽  
Biomarker Analysis ◽  
Marcellus Formation

AbstractThe purpose of this study was to observe how the composition of organic matter (OM) and the extent of anoxia during deposition within the Marcellus Formation in New York varied by distance from the sediment source in eastern New York. Lipid biomarkers (n-alkanes and fatty acids) in the extractable organic component (bitumen) of the shale samples were analyzed, and proxies such as the average chain length (ACL), aquatic to terrestrial ratio (ATR) and carbon preference index (CPI) of n-alkanes were calculated. Fatty acids were relatively non-abundant due to the age of the shale bed, but n-alkane distributions revealed that the primary component of the OM was terrigenous plants. The presence of shorter n-alkane chain lengths in the samples indicated that there was also a minor component of phytoplankton and algal (marine) sourced OM. Whole rock analyses were also conducted, and cerium anomalies were calculated as a proxy for anoxia. All samples had a negative anomaly value, indicating anoxic conditions during deposition. Two samples, however, contained values close to zero and thus were determined to have suboxic conditions. Anoxia and total organic matter (TOM) did not show any spatial trends across the basin, which may be caused by varying depths within the basin during deposition. A correlation between nickel concentrations and TOM was observed and indicates that algae was the primary source of the marine OM, which supports the lipid biomarker analysis. It was determined that the kerogen type of the Marcellus Formation in New York State is type III, consistent with a methane-forming shale bed.

Liquid hydrocarbon characterization of the lacustrine Yanchang Formation, Ordos Basin, China: Organic-matter source variation and thermal maturity

2017 ◽  
Vol 5 (2) ◽  
pp. SF225-SF242 ◽  
Author(s):  
Xun Sun ◽  
Quansheng Liang ◽  
Chengfu Jiang ◽  
Daniel Enriquez ◽  
Tongwei Zhang ◽  
...  
Keyword(s):  
Organic Matter ◽  
Source Rock ◽  
Ordos Basin ◽  
Depositional Environments ◽  
Source Rocks ◽  
Type I ◽  
Hydrocarbon Generation ◽  
Type Ii ◽  
Thermal Maturity ◽  
Yanchang Formation

Source-rock samples from the Upper Triassic Yanchang Formation in the Ordos Basin of China were geochemically characterized to determine variations in depositional environments, organic-matter (OM) source, and thermal maturity. Total organic carbon (TOC) content varies from 4 wt% to 10 wt% in the Chang 7, Chang 8, and Chang 9 members — the three OM-rich shale intervals. The Chang 7 has the highest TOC and hydrogen index values, and it is considered the best source rock in the formation. Geochemical evidence indicates that the main sources of OM in the Yanchang Formation are freshwater lacustrine phytoplanktons, aquatic macrophytes, aquatic organisms, and land plants deposited under a weakly reducing to suboxic depositional environment. The elevated [Formula: see text] sterane concentration and depleted [Formula: see text] values of OM in the middle of the Chang 7 may indicate the presence of freshwater cyanobacteria blooms that corresponds to a period of maximum lake expansion. The OM deposited in deeper parts of the lake is dominated by oil-prone type I or type II kerogen or a mixture of both. The OM deposited in shallower settings is characterized by increased terrestrial input with a mixture of types II and III kerogen. These source rocks are in the oil window, with maturity increasing with burial depth. The measured solid-bitumen reflectance and calculated vitrinite reflectance from the temperature at maximum release of hydrocarbons occurs during Rock-Eval pyrolysis ([Formula: see text]) and the methylphenanthrene index (MPI-1) chemical maturity parameters range from 0.8 to [Formula: see text]. Because the thermal labilities of OM are associated with the kerogen type, the required thermal stress for oil generation from types I and II mixed kerogen has a higher and narrower range of temperature for hydrocarbon generation than that of OM dominated by type II kerogen or types II and III mixed kerogen deposited in the prodelta and delta front.

OIL GEOCHEMISTRY AND POTENTIAL SOURCE ROCKS OF THE OFFICER BASIN, SOUTH AUSTRALIA

1980 ◽  
Vol 20 (1) ◽  
pp. 68 ◽  
Author(s):  
D.M. McKirdy ◽  
A.J. Kantsler
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Carbonate Rocks ◽  
Depositional Environment ◽  
South Australia ◽  
Source Rocks ◽  
Potential Source ◽  
Playa Lake ◽  
Oil Source ◽  
Extractable Organic Matter

Oil shows observed in Cambrian Observatory Hill Beds, intersected during recent stratigraphic drilling of SADME Byilkaoora-1 in the Officer Basin, indicate that oil has been generated within the basin. Shows vary in character from "light" oils exuding from fractures through to heavy viscous bitumen in vugs in carbonate rocks of a playa-lake sequence.The oils are immature and belong to two primary genetic families with some oils severely biodegraded. The less altered oils are rich in the C13 - C25 and C30 acyclic isoprenoid alkanes. Source beds within the evaporitic sequence contain 0.5 - 1.0% total organic carbon and yield up to 1900 ppm solvent-extractable organic matter. Oil-source rock correlations indicate that the oils originated within those facies drilled; this represents the first reported examples of non-marine Cambrian petroleum. The main precursor organisms were benthonic algae and various bacteria.Studies of organic matter in Cambrian strata from five other stratigraphic wells in the basin reveal regional variations in hydrocarbon source potential that relate to differences in precursor microbiota and/or depositional environment and regional maturation. Micritic carbonates of marine sabkha origin, located along the southeast margin of the basin, are rated as marginally mature to mature and good to prolific sources of oil. Further north and adjacent to the Musgrave Block, Cambrian siltstones and shales have low organic carbon values and hydrocarbon yields, and at best are only marginally mature. Varieties of organic matter recognised during petrographic studies of carbonates in the Officer Basin include lamellar alginite (alginite B) and "balls" of bitumen with reflectance in the range 0.2 to 1.4%.

PETROLEUM POTENTIAL OF THE NEOPROTEROZOIC WESTERN OFFICER BASIN, WESTERN AUSTRALIA, BASED ON A SOURCE ROCK MODEL FROM EMPRESS-IA

1999 ◽  
Vol 39 (1) ◽  
pp. 322 ◽  
Author(s):  
G.M. Carlsen ◽  
S.N. Apak ◽  
K.A.R. Ghori K. Grey ◽  
M.K. Stevens
Keyword(s):  
Organic Matter ◽  
Western Australia ◽  
Depositional Environments ◽  
Source Rocks ◽  
Petroleum Potential ◽  
Organic Facies ◽  
Organic Growth ◽  
Rock Model ◽  
Depositional Controls ◽  
The Impact

The sedimentology, palaeontology and geochemistry of Neoproterozoic, organic-rich, clastic and related carbonate deposits in Western Australia provide new insights into the first-order depositional controls on hydrocarbon source rocks in the Neoproterozoic. Organic facies are correlated with depositional facies, revealing the impact of organic productivity and transport of organic rich sediments on the accumulation of organic matter in different depositional environments. Sedimentation is largely limited to ramp, platform, shoal, lagoon and sabkha environments.Growth of benthic organisms in the photic zone was the primary process controlling the production of organic matter in the ramp-shoreline system of the Kanpa Formation. Storms and floods were the primary mechanism for moving organic rich sediments into dysoxic and anoxic depositional environments. Variations in organic facies are indicated by: 1) changes in the palynomorph assemblages, particularly the increase in acritarchs within shallow-water ramp facies and cyanobacterial filaments in quiet-water sediments; 2) organic-rich laminae, containing abundant cyanobacterial filaments and mat material; and 3) the oxidation state of preserved organic remains.Periods of high organic growth rates or periods of mass mortality may have led to the development of an anoxic zone at the water-sediment interface. In the shoal and lagoonal settings, higher rates of clastic sediment dilution combined with oxygenated conditions resulted in lower TOC and hydrogen depleted organic facies.Condensed sections overlying stromatolitic dolomites represent the most effective organic facies of all of the potential source laminae sampled in Empress–IA. Most of the Officer Basin succession is currently within the oil-generating window and hydrocarbon shows encourage further exploration.

scholarly journals Organic matter mineralization and trace element post-depositional redistribution in Western Siberia thermokarst lake sediments

2011 ◽  
Vol 8 (11) ◽  
pp. 3341-3358 ◽  
Author(s):  
S. Audry ◽  
O. S. Pokrovsky ◽  
L. S. Shirokova ◽  
S. N. Kirpotin ◽  
B. Dupré
Keyword(s):  
Trace Elements ◽  
Organic Matter ◽  
Organic Carbon ◽  
Lake Sediments ◽  
Water Column ◽  
Western Siberia ◽  
Ecosystem Development ◽  
Thermokarst Lake ◽  
Fe And Mn ◽  
The Impact

Abstract. This study reports the very first results on high-resolution sampling of sediments and their porewaters from three thermokarst (thaw) lakes representing different stages of ecosystem development located within the Nadym-Pur interfluve of the Western Siberia plain. Up to present time, the lake sediments of this and other permafrost-affected regions remain unexplored regarding their biogeochemical behavior. The aim of this study was to (i) document the early diagenesic processes in order to assess their impact on the organic carbon stored in the underlying permafrost, and (ii) characterize the post-depositional redistribution of trace elements and their impact on the water column. The estimated organic carbon (OC) stock in thermokarst lake sediments of 14 ± 2 kg m−2 is low compared to that reported for peat soils from the same region and denotes intense organic matter (OM) mineralization. Mineralization of OM in the thermokarst lake sediments proceeds under anoxic conditions in all the three lakes. In the course of the lake development, a shift in mineralization pathways from nitrate and sulfate to Fe- and Mn-oxyhydroxides as the main terminal electron acceptors in the early diagenetic reactions was suggested. This shift was likely promoted by the diagenetic consumption of nitrate and sulfate and their gradual depletion in the water column due to progressively decreasing frozen peat lixiviation occurring at the lake's borders. Trace elements were mobilized from host phases (OM and Fe- and Mn-oxyhydroxides) and partly sequestered in the sediment in the form of authigenic Fe-sulfides. Arsenic and Sb cycling was also closely linked to that of OM and Fe- and Mn-oxyhydroxides. Shallow diagenetic enrichment of particulate Sb was observed in the less mature stages. As a result of authigenic sulfide precipitation, the sediments of the early stage of ecosystem development were a sink for water column Cu, Zn, Cd, Pb and Sb. In contrast, at all stages of ecosystem development, the sediments were a source of dissolved Co, Ni and As to the water column. However, the concentrations of these trace elements remained low in the bottom waters, indicating that sorption processes on Fe-bounding particles and/or large-size organo-mineral colloids could mitigate the impact of post-depositional redistribution of toxic elements on the water column.

scholarly journals Seasonal dynamics of organic carbon and metals in thermokarst lakes from the discontinuous permafrost zone of western Siberia

2015 ◽  
Vol 12 (2) ◽  
pp. 1975-2019
Author(s):  
R. M. Manasypov ◽  
S. N. Vorobyev ◽  
S. V. Loiko ◽  
I. V. Kritzkov ◽  
L. S. Shirokova ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Water Column ◽  
Permafrost Zone ◽  
Ice Formation ◽  
Thermokarst Lakes ◽  
Dissolved Carbon ◽  
Thermokarst Lake ◽  
Discontinuous Permafrost ◽  
Lake Waters

Abstract. Western Siberia's thermokarst (thaw) lakes extend over a territory spanning over a million km2; they are highly dynamic hydrochemical systems that receive chemical elements from the atmosphere and surrounding peat soil and vegetation, and exchange greenhouse gases with the atmosphere, delivering dissolved carbon and metals to adjacent hydrological systems. This work describes the chemical composition of ~ 130 thermokarst lakes of the size range from a few m2 to several km2, located in the discontinuous permafrost zone. Lakes were sampled during spring floods, just after the ice break (early June), the end of summer (August), the beginning of ice formation (October) and during the full freezing season in winter (February). Dissolved organic carbon (DOC) and the major and trace elements do not appreciably change their concentration with the lake size increase above 1000 m2 during all seasons. On the annual scale, the majority of dissolved elements including organic carbon increase their concentration from 30 to 500%, with a statistically significant (p < 0.05) trend from spring to winter. The maximal increase in trace element (TE) concentration occurred between spring and summer and autumn and winter. The ice formation in October included several stages: first, surface layer freezing followed by crack (fissure) formation with unfrozen water from the deeper layers spreading over the ice surface. This water was subsequently frozen and formed layered ice rich in organic matter. As a result, the DOC and metal concentrations were the highest at the beginning of the ice column and decreased from the surface to the depth. A number of elements demonstrated the accumulation, by more than a factor of 2, in the surface (0–20 cm) of the ice column relative to the rest of the ice core: Mn, Fe, Ni, Cu, Zn, As, Ba and Pb. The main consequences of discovered freeze-driven solute concentrations in thermokarst lake waters are enhanced colloidal coagulation and the removal of dissolved organic matter and associated insoluble metals from the water column to the sediments. The measured distribution coefficient of TE between amorphous organo-ferric coagulates and lake water (< 0.45 μm) were similar to those reported earlier for Fe-rich colloids and low molecular weight (< 1 kDa) fractions of thermokarst lake waters, suggesting massive co-precipitation of TE with amorphous Fe oxy(hydr)oxide stabilized by organic matter. Although the concentration of most elements is lowest in spring, this period of maximal water coverage of land creates a significant reservoir of DOC and soluble metals in the water column that can be easily mobilized to the hydrological network. The highest DOC concentration observed in the smallest (< 100 m2) water bodies in spring suggests their strongly heterotrophic status and, therefore, elevated CO2 flux from the lake surface to the atmosphere.

scholarly journals A New Evaluation Method of Total Organic Carbon for Shale Source Rock Based on the Effective Medium Conductivity Theory

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Jian Fu ◽  
Xuesong Li ◽  
Yonghe Sun ◽  
Qiuli Huo ◽  
Ting Gao ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Total Organic Carbon ◽  
Clay Minerals ◽  
Pore Water ◽  
Effective Medium ◽  
Source Rocks ◽  
Model Parameters ◽  
Hydrocarbon Generation ◽  
Tight Sandstone

In the evaluation of source rocks, the total organic carbon (TOC) is an important indicator to evaluate the hydrocarbon generation potential of source rocks. At present, the commonly used methods for assessing TOC include △ log R and neural network method. However, practice shows that these methods have limitations in the application of unconventional intervals of sand-shale interbeds, and they cannot sufficiently reflect the variation of TOC in the vertical direction. Therefore, a total organic carbon (TOC) evaluation model suitable for shale and tight sandstone was established based on the effective medium symmetrical conduction theory. The model consists of four components: nonconductive matrix particles, clay minerals, organic components (solid organic matter and hydrocarbons), and pore water. The conductive phase in the model includes clay minerals and pore water, and other components are treated as nonconductive phases. When describing the conductivity of rock, each component in the model is completely symmetrical, and anisotropic characteristics of each component are considered. The model parameters are determined through the optimization method, and the bisection iteration method is used to solve the model equation. Compared with the classic TOC calculation method, the new model can evaluate the abundance of organic matter in shale and tight sandstone, which provides a new option to assess the TOC of rocks based on logging methods.

scholarly journals Organic-carbon-rich sediments: benthic foraminifera as bio-indicators of depositional environments

2019 ◽  
Vol 16 (21) ◽  
pp. 4183-4199 ◽  
Author(s):  
Elena Lo Giudice Cappelli ◽  
Jessica Louise Clarke ◽  
Craig Smeaton ◽  
Keith Davidson ◽  
William Edward Newns Austin
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Carbon Content ◽  
Benthic Foraminifera ◽  
Organic Content ◽  
Depositional Environments ◽  
Organic Carbon Content ◽  
Carbon Burial ◽  
Actual Change ◽  
Freshwater Inputs

Abstract. Fjords have been described as hotspots for carbon burial, potentially playing a key role within the carbon cycle as climate regulators over multiple timescales. Nevertheless, little is known about the long-term fate of the carbon that may become stored in fjordic sediments. One of the main reasons for this knowledge gap is that carbon arriving on the seafloor is prone to post-depositional degradation, posing a great challenge when trying to discriminate between an actual change in the carbon deposition rate and post-depositional carbon loss. In this study, we evaluate the use of modern benthic foraminifera as bio-indicators of organic carbon content in six voes (fjords) on the west coast of Shetland. Benthic foraminifera are known to be sensitive to changes in organic carbon content in the sediments, and changes in their assemblage composition therefore reflect synchronous variations in the quantity and quality of carbon reaching the seafloor. We identified four environments based on the relationship between benthic foraminiferal assemblages and organic carbon content in the sediments: (1) land-locked regions influenced by riverine and/or freshwater inputs of organic matter, namely the head of fjords with a restricted geomorphology; (2) stressed environments with a heavily stratified water column and sediments rich in organic matter of low nutritional value; (3) depositional environments with moderate organic content and mild or episodic current activity; and (4) marginal to coastal settings with low organic content, such as fjords with an unrestricted geomorphology. We conclude that foraminifera potentially provide a tool to disentangle primary organic carbon signals from post-depositional degradation and loss of organic carbon because of their environmental sensitivity and high preservation potential in the sedimentary record.

Controls on organic accumulation in late Jurassic shales of northwestern Europe as inferred from trace-metal geochemistry

2004 ◽  
Vol 175 (5) ◽  
pp. 491-506 ◽  
Author(s):  
Nicolas Tribovillard ◽  
Alain Trentesaux ◽  
Abdelkader Ramdani ◽  
François Baudinet ◽  
Armelle Riboulleau
Keyword(s):  
Organic Matter ◽  
Dilution Effect ◽  
Major Elements ◽  
Depositional Environments ◽  
Sediment Flux ◽  
Geochemical Data ◽  
Clay Shales ◽  
Reducing Conditions ◽  
Water Stratification ◽  
Clay Formation

Abstract In the Kimmeridge Clay Formation of the Wessex-Weald Basin, five organic-matter-rich intervals (or ORIs), dated from Kimmeridgian-Tithonian times, can be correlated from distal depositional environments in Dorset and Yorkshire (UK) to the proximal environments in Boulonnais, northern France. The ORIs are superimposed on a meter-scale cyclic distribution of organic matter (OM), referred to as primary cyclicity, which is commonly interpreted to result from Milankovitch climate forcing. The present work addresses the distribution of redox-sensitive and/or sulfide-forming trace metals and selected major elements (Si, Al and Fe) in Kimmeridge Clay shales from the Cleveland Basin (Yorkshire) and the Boulonnais cliffs with two objectives: 1) to determine whether the ORIs formed in similar paleoenvironments, and 2) to identify the mechanism(s) of OM accumulation. High-resolution geochemical data from primary cycles in the Yorkshire boreholes (Marton and Ebberstone boreholes), were studied and the results are then applied with lower resolution sampling at the ORI scale in the Flixton borehole and Boulonnais cliff. Good correlations are found between total organic carbon (TOC) vs Cu/Al and Ni/Al, but relationships between TOC and Mo/Al, V/Al and U/Al are more complex. Cu and Ni enrichment is interpreted to have resulted from passive accumulation with OM in an oxygen-deficient basinal setting, which prevented the subsequent loss of Cu and Ni from the sediment. Mo and V were significantly enriched only in sediments where considerable amounts of OM (TOC&gt;7 %) accumulated, the result of strongly reducing conditions and OM burial. At the scale of the Flixton ORIs, the samples with the highest Mo and V concentrations also show relative Fe enrichment, suggesting pyrite formation in the water column (combination of euxinic conditions and presumably low sedimentation rates). Samples from all ORIs were slightly enriched in Si relative to Al, interpreted as reflecting decreased sediment flux during transgressive and early-highstand systems tracts. The data show that in some ORIs, OM accumulation proceeded while productivity was not particularly high and sediments were not experiencing strong anoxia. In other ORIs, OM accumulation was accompanied by widespread anoxia and possibly euxinic conditions in distal settings. Though somewhat different from each other, the ORIs have all developed during episodes of reduced terrigenous supply (transgressive episodes). The common feature linking these contrasted episodes of enhanced OM storage (ORIs) must be the conjunction of productivity coupled with a decrease in the dilution effect by the land-derived supply, in a depositional environment prone to water stratification and, therefore, favorable to OM preservation and accumulation.

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