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A Marine Focus
The Permian-Triassic Boundary: Paleoclimate

During the lower Triassic, the interior of Pangaea remained predominantly hot and dry with warm, temperate climates extending to the Poles. Worldwide climate was largely homogeneous and no polar ice existed. Sedimentary features such as red-sandstones, salt pseudomorphs in marls, ephemeral river deposits, mud cracks, evaporites, and digenetic carbonate cements from Gondwanan strata suggest a semi-arid climate, probably caused by the reduction in total area covered by continental shelf seas due to the emergence of the super continent Pangaea. This climate was punctuated by short periods of humidity, as evidenced by the prevalence of amphibian and water plant remains as well as braided fluvial sediments, clay-rich deltaic sediments and red-beds of alluvial origin. A peculiar cyclicity is seen in strata from this time due to periodic high humidity levels. This cyclicity has been attributed to climate forcing due to Milankovitch cycles. The effects of Milankovitch cycles are evidenced in Olenekian aged meter-scale peritidal carbonate strata in the Nanpanjiang Basin of South China. The stacking patterns in these strata display three orders of cyclicity, suggesting a hierarchical stratigraphic relationship. That is, the rates of carbonate production showed a sufficient order so as to suggest cyclic climactic influence. Strong obliquity coupled with low-amplitude sea-level changes would have served to create conditions to limit accommodation on shallow marine platforms, thus creating small, low carbonate strata. (Yang, 2000)

Figure: Climate of the Early Triassic (Scotese, 2001)