Detection of Organic-Rich Oil Shales of the Green River Formation, Utah, with Ground-Based Imaging Spectroscopy

Oil shales contain abundant immature organic matter and are a potential unconventional petroleum resource. Prior studies have used visible/shortwave infrared imaging spectroscopy to map surface exposures of deposits from satellite and airborne platforms and image cores in the laboratory. Here, we work at an intermediate, outcrop-scale, testing the ability of field-based imaging spectroscopy to identify oil shale strata and characterize the depositional environments that led to enrichment of organic matter in sedimentary rocks within the Green River Formation, Utah, USA. The oil shale layers as well as carbonates, phyllosilicates, gypsum, hydrated silica, and ferric oxides are identified in discrete lithologic units and successfully mapped in the images, showing a transition from siliciclastic to carbonate- and organic-rich rocks consistent with previous stratigraphic studies conducted with geological fieldwork

Detrital zircon age and provenance constraints on late Paleozoic ice-sheet growth and dynamics in Western and Central Australia

U–Pb dating and Hf-isotope provenance analysis of detrital zircons from the glaciogenic lower Permian Grant Group of the Canning Basin indicate sources principally from basement terranes in central Australia, with subordinate components from terranes to the south and north. Integrating these data with field outcrop and subsurface evidence for ice sheets, including glacial valleys and striated pavements along the southern and northern margins of the basin, suggests that continental ice sheets extended over several Precambrian upland areas of western and central Australia during the late Paleozoic ice age (LPIA). The youngest zircons constrain the maximum age for contemporaneous ice sheet development to the late Carboniferous (Kasimovian), whereas palynology provides a minimum age of early Permian (Asselian–Sakmarian). Considering the palynological age of the Grant Group within the context of regional and global climate proxies, the main phase of continental ice sheet growth was possibly in the Ghzelian–Asselian. The presence of ice sheets older than Kasimovian in western and central Australia remains difficult to prove given a regional gap in deposition possibly covering the mid-Bashkirian to early Ghzelian within the main depocentres and even larger along basin margins, and the poor evidence for older Carboniferous glacial facies. There is also no evidence for extensive glacial facies younger than mid-Sakmarian in this region as opposed to eastern Australia where the youngest regional glacial phase was Guadalupian

CO\u3csub\u3e2\u3c/sub\u3e-Forced Climate and Vegetation Instability During Late Paleozoic Deglaciation

The late Paleozoic deglaciation is the vegetated Earth’s only recorded icehouse-to-greenhouse transition, yet the climate dynamics remain enigmatic. By using the stable isotopic compositions of soil-formed minerals, fossil-plant matter, and shallow-water brachiopods, we estimated atmospheric partial pressure of carbon dioxide (pCO2) and tropical marine surface temperatures during this climate transition. Comparison to southern Gondwanan glacial records documents covariance between inferred shifts in pCO2, temperature, and ice volume consistent with greenhouse gas forcing of climate. Major restructuring of paleotropical flora in western Euramerica occurred in step with climate and pCO2 shifts, illustrating the biotic impact associated with past CO2-forced turnover to a permanent icefree world