Print this pagePaleoclimatic Indicators in Paleosols Underlying Pennsylvanian Coal Beds: USA
DULONG, FRANK T., and C. BLAINE CECIL
Regionally extensive paleosols formed during low stands of sea level underline most minable Pennsylvanian coal beds. Several characteristics of the paleosols indicate long-term soil formation prior to the onset of peat formation. Regional description of soil types under any given coal bed allows reconstruction of the paleowater table, the paleoclimate, the lateral variation in soil types (catena), and surficial relief.
Lower and lower Middle Pennsylvanian paleosols under coal beds in the Appalachian basin have features such as gleization, well-crystallized clay minerals, and the absence of subaerial exposure features, all of which indicate peat formation was initiated on poorly drained aquic Inceptisols. The climate was probably perhumid which is consistent with the inferred domed-peat origin of Lower and lower Middle Pennsylvanian coal beds. Upper Middle and Upper Pennsylvanian paleosols underlying coal beds have features such as stressed cutans and mukkara structures which indicate the soil was well drained with the water table commonly at or below the C-horizon. The climate was relatively less wet and rainfall was more seasonal.
A Middle Pennsylvanian, Desmoinesian, sedimentary cycle/ biostratigraphic interval has been identified and correlated across the United States to evaluate allogenic and autogenic controls on lithostratigraphy. Within the cycle, are differences in the structure and mineralogy of the paleosol underlying the coal bed. The paleosol is a paleo-Ultisol in the Appalachian basin and grades to a paleo calcic-Vertisol in the Western Interior basin, which indicates increasing seasonality of rainfall from east to west.