Dust, Ice, and Biotic Consequences in Late Paleozoic Pangaea
|対象||教職員向け 大学院生向け 学部生向け|
|イベント概要||講師：Gerilyn (Lynn) S. Soreghan (オクラホマ大学地質学地球物理学教室)
Dust, including loess, is well recognized as a climate archive for Earth's Quaternary record. Quaternary loess is extra-tropical, generated by 1) physical (glacial) weathering in high-mid latitudes, or 2) deflation of ephemeral lacustrine/fluvial systems, or eolian abrasion in low-mid latitude deserts. Loess deposits of pre-Cenozoic age are less well known, but growing research suggests widespread loess in western tropical Pangaea dating from the Late Carboniferous-Permian (~300 Ma). In this talk, I will report on these dust deposits, the timing and sources of the loess, and implications for tropical paleoclimate.
The paleotropical setting is remarkably unusual relative to the Cenozoic, and requires semi-arid to arid conditions at the source, and a glacial-interglacial modulation of sourcing. Climate modeling (Community Climate System Model v.3) suggests that cold tropical climate with upland glaciation represents one scenario capable of replicating the conditions necessary for dust generation and mobilization from the Central Pangaean Mountains.
The Late Paleozoic has long been cast as climatically analogous to the Late Cenozoic, with glaciation limited to high southern latitudes. If more widespread (upland) glaciation occurred, then these vast deposits archive unusual climatic conditions, but moreover may have induced climate change. Regardless, loess of the late Paleozoic reveals fascinating insight into the Earth System of our most recent pre-Cenozoic icehouse.