Bighorn Basin Coring Project (BBCP): a continental perspective on early Paleogene hyperthermals

[摘要] During the summer of 2011, the Bighorn Basin Coring Project (BBCP) recoveredover 900 m of overlapping core from 3 different sites in late Paleoceneto early Eocene fluvial deposits of northwestern Wyoming. BBCP cores arebeing used to develop high-resolution proxy records of the Paleocene–EoceneThermal Maximum (PETM) and Eocene Thermal Maximum 2 (ETM2) hyperthermalevents. These events are short-term, large magnitude global warming eventsassociated with extreme perturbations to the earth's carbon cycle. Althoughthe PETM and ETM2 occurred ~55–52 million years ago, they areanalogous in many ways to modern anthropogenic changes to the carbon cycle.By applying various sedimentological, geochemical, and palynological methodsto the cores, we hope to better understand what caused these events, studythe biogeochemical and ecological feedbacks that operated during them, andreveal precisely how they impacted continental environments.

Core recovery was >98% in all holes and most drilling wascarried out without fluid additives, showing that continuous coring ofcontinental smectitic deposits like these can be achieved with minimal riskof contamination to molecular biomarkers. Cores were processed in the BremenCore Repository where the science team convened for 17 days to carry outdata collection and sampling protocols similar to IODP projects. Initialresults show that the weathered horizon extends to as much as~30 m below the surface and variations in magneticsusceptibility within the cores record an interplay between grain size andpedogenesis. Previous investigations of outcrops near the BBCP drill sitesallow detailed evaluation of the effects of weathering on common proxymethods. Studies of lithofacies, organic geochemistry, stable isotopegeochemistry, calibrated XRF core scanning, paleomagnetics, and palynologyare underway and will represent the highest resolution and most integratedproxy records of the PETM from a continental setting yet known. An extensiveoutreach program is in place to capitalize on the educational valueassociated with the Bighorn Basin's unusually complete record of Phanerozoicearth history.

[学科分类] 地质学