Paleosol archives of environmental and climatic history in paleotropical western Pangea during the latest Pennsylvanian through Early Permian
Paleosol archives of environmental and climatic history in paleotropical western Pangea during the latest Pennsylvanian through Early Permian (in Resolving the late Paleozoic ice age in time and space, Christopher R. Fielding (editor), Tracy D. Frank (editor) and John L. Isbell (editor))
Special Paper - Geological Society of America (2008) 441: 291-303
- ancient ice ages
- arid environment
- glacial environment
- glacial geology
- humid environment
- interglacial environment
- New Mexico
- terrestrial environment
- tropical environment
- United States
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N31°30'00" - N37°00'00", W109°04'60" - W103°00'00"
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N25°45'00" - N36°30'00", W106°30'00" - W93°30'00"
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The stratigraphic and regional distributions of paleosol morphology in latest Pennsylvanian through Early Permian strata in Colorado, Utah, Arizona, New Mexico, Texas, and Oklahoma are presented in this paper. This regional extent corresponds to a paleolatitudinal gradient spanning approximately 5 degrees S to 10 degrees N. Morphological trends from this region delineate significant and systematic temporal and spatial changes in Permian-Carboniferous paleoenvironment and paleoclimate. The inferred latest Pennsylvanian (Virgilian) through early Early Permian environmental pattern is complex, but it indicates persistently dry, semiarid to arid conditions in Colorado, Utah, and Arizona, at paleolatitudes north of approximately 2 degrees N, whereas lower paleolatitude ( approximately 2 degrees S to 2 degrees N) tropical regions in New Mexico exhibit a stepwise shift from subhumid to semiarid and variably seasonal conditions throughout late Pennsylvanian and the first half of Early Permian (Virgilian through Wolfcampian) time, followed by a subsequent shift to more arid conditions during the latter part of the Early Permian (Leonardian). Notably, strata from the southernmost paleosites, in Texas and Oklahoma, exhibit the most significant and abrupt climate changes through this period; they show a rapid transition from nearly ever-wet latest Pennsylvanian climate (at approximately 5 degrees S) to drier and seasonal climate across the Permian-Carboniferous system boundary, and finally to arid and seasonal climate by Leonardian time (at approximately 2-4 degrees N). The inferred climate patterns show no robust long-term correlation with the high-latitude Gondwanan records of glaciation. Rather, the long-term record of Permian-Pennsylvanian climate indicators from the southwestern United States is most simply explained by an approximately 8 degrees northward tectonic drift through (essentially) static climate zones over western tropical Pangea during the interval of study. However, the relatively rapid perturbations to climate recorded by these pedogenic archives appear to be too rapid for tectonic forces and might correspond to changes in climate drivers, such as atmospheric pCO (sub 2) , atmospheric circulation, and glacial-interglacial cycles.