CARBONIFEROUS SPATIAL AND TEMPORAL CLIMATE CHANGE IN SOUTHERN EURAMERICA

A long-term cool mode that began in the Late Devonian resulted in late Famennian glacial deposits in the Appalachian basin. In addition, coal deposits, chemically reduced fluvial sediments, highly leached paleosols, and a relative increase in terrestrial organic matter in both marine and nonmarine strata, are indicative of a humid climate that persisted for 15 m.y. into the early Visean (mid Osagean) in eastern North America. The subsequent early Visean to late Serpukhovian 20 m.y. warm mode was accompanied by sea level rise and a switch to aridity as indicated by dry-climate paleosols and evaporites throughout much of eastern North America. The ensuing 15 m.y. mid Carboniferous cool mode began in the late Serpukhovian (late Chesterian) and was accompanied by sea level fall and perhumid conditions. These late Serpukhovian to early Moskovian (late Atokan) humid conditions resulted in intense chemical weathering, extensive karsting of carbonate strata from the Appalachian basin into western North America, and coal deposits preserved in tectonically subsiding cratonic basins. The succeeding 5 m.y. early Moscovian to late Kasimovian warm mode (Desmoinesian to Missourian) caused sea level rise with coeval continental-scale climate drying. The Late Carboniferous warm mode culminated in the Kasimovian (Missourian) when dry subhumid to arid conditions spanned North America. Consequently, coal formation was curtailed, and copious amounts of carbonate minerals in paleosols as well as evaporites indicate a dry paleoclimate. The onset of a cool mode in the Gzhelian (Virgilian) that culminated in the Permian was accompanied by a moderate increase in humid conditions as indicated by the return of coal-forming conditions in eastern North America. Similarly, shorter term glacial and interglacial intervals exhibit a comparable wet-dry pattern; glacial intervals were humid and interglacials were relatively dry. Thus, Late Paleozoic strata across North America indicate that cool periods were relatively wet when compared to preceding and subsequent warm periods. Ice volume was the predominant control on global atmospheric pressure belts, variations in monsoonal winds, and rainfall patterns in the low latitudes of the Late Paleozoic paleogeographies.