Geoffrey S Ellis (Former Employee)

The main controlling factors of organic matter accumulation in the Upper Ordovician Wufeng–Lower Silurian Longmaxi Formations are complex and remain highly controversial. This study investigates the vertical variation of total organic carbon (TOC) content as well as major and trace element concentrations of four Ordovician–Silurian transition sections from the Upper Yangtze Platform of...

Compound-specific sulfur isotope analysis was applied to a suite of 18 crude oils generated from the Permian Phosphoria Formation in the Bighorn Basin, western USA. These oils were generated at various levels of thermal maturity and some experienced thermochemical sulfate reduction (TSR). This is the first study to examine the effects of thermal maturation on stable sulfur isotopic...

The sulfur isotopic fractionation associated with the formation of organic sulfur compounds (OSCs) during thermochemical sulfate reduction (TSR) was studied using gold-tube pyrolysis experiments to simulate TSR. The reactants used included n-hexadecane (n-C16) as a model organic compound with sulfate, sulfite, or elemental sulfur as the sulfur source. At the end of each experiment, the S...

Thiadiamondoids (TDs) are diamond-like compounds with a sulfide bond located within the cage structure. These compounds were suggested as a molecular proxy for the occurrence and extent of thermochemical sulfate reduction (TSR). Compound-specific sulfur-isotope analysis of TDs may create a multi-parameter system, based on molecular and δ34S values that may be sensitive over a wider range...

Laguna Mar Chiquita (central Argentina; ~latitude 31°S, longitude 63°W) provides an outstanding opportunity to examine organic facies development and petroleum source-rock potential in a modern thick-skinned foreland basin lake. In this case study, we define profundal, paleodelta, and lake-margin depositional environments based on trends in bathymetry and lake-floor sediment particle...

In the last 10 years, the success of shale gas and shale oil productions as a result of technological advances in horizontal drilling, hydraulic fracturing and nanoscale reservoir characterization have revolutionized the energy landscape in the United States. Resource assessment by the China Ministry of Land and Resources in 2010 and 2012 and by the U.S. Energy Information Administration...

This study examines the relationship between depositional environment and sedimentary organic geochemistry in Lake Malawi, East Africa, and evaluates the relative significance of the various processes that control sedimentary organic matter (OM) in lacustrine systems. Total organic carbon (TOC) concentrations in recent sediments from Lake Malawi range from 0.01 to 8.80 wt% and average 2...

Dibenzofuran (DBF), its alkylated homologues, and benzo[b]naphthofurans (BNFs) are common oxygen-heterocyclic aromatic compounds in crude oils and source rock extracts. A series of positional isomers of alkyldibenzofuran and benzo[b]naphthofuran were identified in mass chromatograms by comparison with internal standards and standard retention indices. The response factors of dibenzofuran...

Lake deposystems are commonly associated with retroarc mountain belts in the geological record. These deposystems are poorly characterized in modern retroarcs, placing limits on our ability to interpret environmental signals from ancient deposits. To address this problem, we have synthesized our existing knowledge about the distribution, morphometrics, and sedimentary geochemical...

Tropical climate is rapidly changing, but the effects of these changes on the geosphere are unknown, despite a likelihood of climatically-induced changes on weathering and erosion. The lack of long, continuous paleo-records prevents an examination of terrestrial responses to climate change with sufficient detail to answer questions about how systems behaved in the past and may alter in...

This study quantifies the effects of organic-matter (OM) thermal maturity on methane (CH4) sorption, on the basis of five samples that were artificially matured through hydrous pyrolysis achieved by heating samples of immature Woodford Shale under five different time–temperature conditions. CH4-sorption isotherms at 35 °C, 50 °C, and 65 °C, and pressures up to 14 MPa on dry, solvent...

Methane is an important greenhouse gas and energy resource generated dominantly by methanogens at low temperatures and through the breakdown of organic molecules at high temperatures. However, methane-formation temperatures in nature are often poorly constrained. We measured formation temperatures of thermogenic and biogenic methane using a “clumped isotope” technique. Thermogenic gases...