Precipitation Models for Sediment Supply in Warm Climates
Sediment discharge in fluvial systems is primarily a function of climate. In tropical and subtropical climates, discharge of solid sediment is nearly zero under perhumid climatic conditions whereas maximum discharge occurs under dry subhumid condition when there is a pronounced dry season and seasonality in rainfall is at a maximum. Discharge of solid sediment also approaches zero under arid conditions when there is little if any rainfall throughout the year. Solute discharge is also largely a function of climate. Solute discharge appears to be greatest under semiarid to subhumid climatic conditions and is nearly zero under hyperarid and perhumid conditions. The effects of tectonics and eustasy on sediment discharge are negligible, particularly at intermediate and short-term time scales.
The potential for the production and accumulation of terrestrial organic matter as peat in a given basin is also a function of climate. The effects of tectonics and eustasy as controls on peat formation are minimal, but they are very important in burial and preservation of peat as coal. In addition, it is well known that the potential for eolian transport is also a function of climate, with maximum transport occurring under arid conditions. With increasing wetness, including seasonal rainfall, dune fields begin to stabilize and eolian transport diminishes and finally becomes zero.
Climate is also one of the primary controls on weathering, pedogenesis, and soil formation. However, there is not always a strong relation between the genesis of soils and annual rainfall. Therefore, we relate the genesis of soil orders that form under relatively warm conditions to specific degrees of seasonality of rainfall when other factors such as parent material and relief are relatively constant.
Figures & Tables
The role of climate as a primary control on stratigraphy is the cornerstone of this volume. The emphasis on climate is in distinct contrast to most previous studies, in which stratigraphic variability has been related to changes in sea level and in tectonic activity. Furthermore, the findings, derived from several years of detailed study of modern and ancient key geologic sections around the world, indicate that traditional depositional models generally do not fully explain the origin of fossil fuels. Although the results of the studies presented in this volume are intended to contribute to the disciplines of sedimentary geology and stratigraphy, the contributors recognize that their results may also contribute to a better understanding of global climate change. The theoretical background of climate control on sediment supply and stratigraphy is presented in the volume. With this background in place, detailed documentation and analysis of climate control on the lithologic variation of a single Middle Pennsylvanian.