Some Examples of Climate Controls on Sedimentation
Part 3 of this volume contains five papers that illustrate some of the various effects of climate on sedimentation, including studies of climatic controls on sediment supply in marine environments and in desert environments, numerical modeling of ancient climates, and climate influences on the occurrence of petroleum. The paper by Edgar and Cecil relates spatial changes in sedimentation in the Peru–Chile trench (off the west coast of South America) to spatial changes in climate along the Andes Mountain chain. They show that the deepest part of the trench is sediment starved adjacent to the zone where the Andes Mountains are highest and the climate is hyperarid. Fluvial sediment supply is climate dependent, regardless of the heights of mountains in provenance regions. As the climate becomes progressively wetter north and south of the sediment-starved region, the trench is progressively filled, even though the height of the Andes decreases. As an example of climate effects on basin fill, the spatial distribution of sediment in the Peru–Chile trench and the climate of western South America are used as an analogue for the late Paleozoic sediment fill of the Ouachita trough of North America. Edgar and Cecil suggest that the onset of filling of the Ouachita trough is related to the northward drift of the North American craton (from the dry tropics into the wet tropics) rather than the onset of tectonism. The article by Edgar et al. presents shallow seismic interpretations derived from the modern Gulf of Carpentaria, in northern Australia. The seismic data suggest that numerous Pliocene to Recent transgressive–
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Climate Controls on Stratigraphy
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.