GREENHOUSE VERSUS ICE HOUSE HIGH-FREQUENCY TRANSGRESSIVE/REGRESSIVE CYCLES IN FORELAND BASIN FILL

The Chesterian Hinton Formation of WV consists of coastal plain to marginal marine facies deposited in a foreland basin. Continental ice sheets were present during this interval and successions deposited in the late Mississippian resemble the Pennslvanian Ice House cyclothems. Eight, late Mississippian, transgressive-regressive (T-R) cycles were deposited within a roughly 2.5 million year period in the Appalachian Basin. Consequently the eight T-R events are 4^th order cycles superimposed on the lowstand and transgressive phases of a 3^rd order cycle, all of which were generated by glacioeustatic fluctuation. Glacioestatic events remove and add fluids to the ocean, producing globally synchronous cycles, contrasting markedly with the stratigraphy produced during Greenhouse periods.

Marginal marine to shelf facies of the Jurassic Sundance Formation were deposited in the Mesozoic Greenhouse interval within the Foreland Basin of the western Cordillera. These strata also contain high frequency, T-R cycles, but there was no ice sheet activity in this interval. However, Milankovich cyclicity was documented in coeval strata. Consequently the T-R cycles of this interval are inferred to be caused by cyclic variation in sediment supply, triggered by orbitally-driven climate change, superimposed on sustained subsidence. The Sundance paleolatitude was located near the southern edge of the Ferrell Cell, and as it shifted toward and away from the pole, due to changes in insolation, the deposition site was subjected to variable rates of moisture, causing varied rates of deposition. Since the sedimentary response was caused by regional changes in moisture, areas of regression and transgression were only regionally extensive. So in the Greenhouse interval, globally synchronous change in insolation yields only regionally extensive T-R sedimentation, wherein the poleward side of a climate belt experiences decreased moisture/deposition and a transgression, the equatorward side of the same climate belt experiences increased moisture/deposition and a regression. This contrasts with the Ice House intervals in which change in global insolation, causes climate belt migration and large changes in ocean volume, leading to global sea level change and therefore shoreline advance and retreat that is generally global in extent.