Speaker: Richard Lease, USGS Abstract: The Hue Shale comprises condensed, organic-rich black shale and volcanic ash that blanketed the eastern Colville foreland basin in the Aptian–Maastrichtian (~115–70 Ma), reflecting deepwater conditions in the western Arctic Ocean. The Arctic occupied a unique position during the Cretaceous–Paleogene greenhouse phase as a newly-formed, partially-enclosed polar ocean basin with periods of high carbon burial but variable oxygenation, stratification, and productivity. Multidisciplinary Hue Shale research by a team of 15 USGS geologists over the past five years on the eastern North Slope provides a framework for Arctic source rock and paleoclimate studies. This talk presents new insights on the timing of Hue Shale organic carbon burial during global Oceanic Anoxic Events (OAEs) via correlation of carbon isotope chemostratigraphy and ash zircon U-Pb dates. Hue total organic carbon (TOC) increased by >30-100% during multiple Albian-Campanian OAEs (i.e., OAE1d, OAE2, Hitch Wood, OAE3a, b, c), and was accompanied by increases in marine carbon and productivity proxies. However, geochemical proxies suggest a long-term shift from marine salinity, oxygen minimum zone-like conditions to an increasingly brackish, restricted euxinic basin. I integrate these productivity, redox, and salinity records with the timing of sea level and shelf margin dynamics to examine changing environmental controls on polar greenhouse marine carbon burial.
Speaker Bio: Richard Lease has been a Research Geologist with the U.S. Geological Survey in Anchorage, Alaska since 2012. His research addresses topics in sedimentary basin analysis, mountain building, landscape evolution, and paleoclimate with support from the USGS Energy and Minerals mission area. His favorite AK field locales include the Brooks Range, Alaska Range, Fairweather Range, and Yukon-Tanana Upland. He received an AB in Geosciences from Princeton University, a PhD from the University of California, Santa Barbara, and completed a postdoc at the University of Tuebingen in Germany. His prior research focused on tectonic-climatic-geodynamic interactions during Cenozoic growth of the Tibetan Plateau and Central Andes.
In-Person or Virtual Meeting Online
TIME: Virtual doors open at 11:30 am (Alaska Time), Announcements start at 11:45, Talk is 12 - 1 pm
LOCATION for In-Person: Spruce/Willow Room, Energy Center, 1014 Energy Court, Anchorage
LOCATION for Online: Your home or office.
COST: Free. Bring your lunch to the lecture or your computer.