Environmental drivers of cyclicity recorded in lower Permian eolian strata, Manitou Springs, Colorado, western United States

Three levels of cyclicity are observed in the Ingleside Formation that are inferred to reflect changes in local and global paleoenvironmental conditions. The first is the long-term gradation from the predominantly fluvial upper part of the Fountain Formation to the predominantly eolian Ingleside Formation. This trend is inferred to be the result of long-term aridification of the Pangaean interior. The second scale of cyclicity is denoted by punctuation of the two eolian ridges by alluvial facies comprising the intervening valley. We propose that this dry-wet-dry environmental change is driven by relative global ice volume during the early Permian. Higher volumes of global ice, occurring as Gondwanan ice sheets, appear to correlate to the eolian intervals, whereas, the alluvial interval may be coeval with feckless or complete loss of Gondwanan ice sheets. The third scale of cyclicity is indicated by the SBZ-coset couplets and is inferred to be the result of glacioeustatic variations in sea level resulting from the waxing and waning of relatively large Gondwanan ice sheets.