The Pangaean Megamonsoon- Evidence from the Upper Triassic Chinle Formation,

摘要: The Upper Triassic Chinle Formation was deposited at an exceptional time in Earth's paleogeographic and paleoclimatic history. During the Triassic, supercontinent Pangaea its greatest size, terms of both aggregated continental crust exposed land area. Moreover, divided symmetrically about paleoequator between northern southern hemispheres. These conditions were ideal for maximizing monsoonal circulation, as predicted from paleoclimate models. 5?to 15?N paleolatitude western equatorial region Pangaea, a key area documenting effects climate. This study summarizes sedimentologic paleontologic data on Colorado Plateau integrates that with evidence abundant moisture seasonality attest to reversal flow support hypothesis Pangaean climate dominated by circulation. contains lithofacies fluvial channels, crevasse splays, lakes, bogs, marshes, lacustrine deltas reflect precipitation shallow water tables. Paleosols ichnofossils indicate tables lake levels fluctuated episodically. Interbedded carbonates marginal-lacustrine siltstones mudstones longer-term but regular, episodic fluctuations level. Fine-scale laminations suggest seasonal influx clastic sediment, thus precipitation, basin. Uppermost strata consist interbedded minor eolian sand sheets dunes; thus, later reflects continued marked more pronounced extended dry seasons.