4D paleoenvironmental evolution of the Early Triassic Sonoma Foreland Basin (western USA)

摘要: In the wake of the Mesozoic, the Early Triassic (~251.95 Ma) corresponds to the aftermath of the most severe mass extinction of the Phanerozoic: the end-Permian crisis, when life was nearly obliterated (e.g., 90% of marine species disappeared). Consequences of this mass extinction are thought to have prevailed for several millions of years, implying a delayed recovery lasting the whole Early Triassic, if not more.Several paradigms have been established and associated to a delayed biotic recovery scenario expected to have resulted from harsh and deleterious paleoenvironments. These paradigms include a global anoxia in the marine realm, a “Lilliput” effect, and the presence of “disaster” taxa and “anachronistic” facies. However, recent works have shown a more complex global scheme for the Early Triassic recovery, and that a reevaluation of these paradigms was needed. Especially, new data from the western USA basin were critical in re-addressing these paradigms.The western USA basin is the result of a long tectono-sedimentary history that started 2 Gyr ago by the amalgamation of different lithospheric terranes forming its basement. A succession of orogenies and quiescence phases led to the formation of several successive basins in the studied area, and traces of this important geodynamical activity are still present today. The Sonoma orogeny occurred about 252 Ma in response to the eastward migration of drifting arcs toward the Laurentian craton. As a result, compressive constrains lead to the obduction of the Golconda Allochthon above the west-Pangea margin in present-day Nevada. Emplacement of this topographic load provoked …