Anomalous cold in the Pangaean tropics

• DOI: 10.1130/g24822a.1
• Publication Date: 2008-07-22T15:08:31Z
• Authors: Gerilyn S. Soreghan; Michael J. Soreghan; Christopher J. Po...; Roger A. Young; Cortland F. Eble; Dustin E. Sweet; Oswaldo C. Davogu...
• Keywords: 13. Climate action; 15. Life on land; 01 natural sciences; 0105 earth and related environmental sciences

The late Paleozoic archives the greatest glaciation of the Phanerozoic. Whereas high-latitude Gondwanan strata preserve widespread evidence for continental ice, the Permo-Carboniferous tropics have long been considered analogous to today9s: warm and shielded from the high-latitude cold. Here, we report on glacial and periglacial indicators that record episodes of freezing continental temperatures in western equatorial Pangaea. An exhumed glacial valley and associated deposits record direct evidence for glaciation that extended to low paleoelevations in the ancestral Rocky Mountains. Furthermore, the Permo-Carboniferous archives the only known occurrence of widespread tropical loess in Earth9s history; the volume, chemistry, and provenance of this loess(ite) is most consistent with glacial derivation. Together with emerging indicators for cold elsewhere in low-latitude Pangaea, these results suggest that tropical climate was not buffered from the high latitudes and may record glacial-interglacial climate shifts of very large magnitude. Coupled climate–ice sheet model simulations demonstrate that low atmospheric CO 2 and solar luminosity alone cannot account for such cold, and that other factors must be considered in attempting to explain this “best-known” analogue to our present Earth.