HR: 1340h
AN: PP23B-1339    [Abstracts]
TI: Changing Low-Latitude Paleoenvironments During the Onset of the Late Paleozoic Ice Age.
AU: * Davies, S
EM: sjd27@le.ac.uk
AF: University of Leicester UK, Department of Geology University Road, Leicester, LE1 7RH, United Kingdom
AB: The Carboniferous is one of the critical stepwise transitions in the evolution of the Earth System when rapid changes in climate and atmospheric composition (rise in oxygen/carbon dioxide) coincided with key events in biological evolution (the proliferation of land plants) and increased rates of tectonic plate reorganisation. The paleoequatorial Carboniferous sedimentary successions of Britain and Ireland were deposited in a shallow epicontinental seaway and record high magnitude and high frequency eustatic changes as ice sheets waxed and waned on Gondwana during the onset of the Late Paleozoic ice age. In the Asbian and Brigantian (ca.334-326 Ma) widespread shallow and marginal marine conditions are recorded by mixed carbonate and siliciclastic deposition and carbonate successions on platforms and shelves. In the mid-Brigantian, a marine transgression reduced deposition on the carbonate platforms and connected previously separate sub-basins in central Scotland. Data used to interpret global climate for this time slice are contradictory. A warmer global climate is suggested by the widespread extent of a Gondwanan macrofloral realm that requires frost-free conditions whereas isotope data suggest a cold Asbian followed by a warm, ice-free Brigantian. In the Pendleian to Yeadonian (ca.326-317 Ma), increasingly light oxygen isotope data indicate a return to cold conditions. Well- constrained periods of Gondwanan glacial sedimentation (e.g. in SE Australia), of 1 and 3 Myr duration, coincide with major paleoevironmental changes across Britain and Ireland, including the end of significant carbonate production and the earliest examples of large-scale river paleovalleys (with 20-80 m of erosional relief). Depositional environments (fluvial, deltaic) and basin bathymetry (distinct shelf edges) provided optimal conditions for the effects of sea-level change to be recorded in sedimentary successions of this time slice. These late Mississippian and early Pennsylvanian siliciclastic and carbonate successions generally reflect shifts in global climate, including glacial periods, but temporal changes in paleoenvironments and local climate overprint the record. These data provide useful constraints for modelling climate change in deep time.
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1630 Impacts of global change (1225)
DE: 1637 Regional climate change
DE: 1641 Sea level change (1222, 1225, 4556)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting