Of these, ooids were widespread in shallow marine carbonate settings during the PermianâTriassic (PâTr) transition, and giant ooids occurred more frequently at this critical period than any time during the Phanerozoic. The PermianâTriassic mass extinction (PTME) is not only a dramatic loss in biodiversity and major change in ecosystem structures, but also coincided with the formation of abundant unusual sedimentary structures. The anomalous primary mineralogy of Lower Triassic ooids implies that previously assumed stable seawater composition during the Early Triassic needs to be revaluated. Widespread aragonitic ooids in the end of the Permian reinforce the scenario that an âaragonite seaâ period may have resulted in the dramatic losses of skeletal organisms that precipitated low-Mg calcite and hampered their recovery in the aftermath. isarcica Zone of the earliest Triassic and afterwards. The latest Permian ooids were usually small (0.3 to 0.7mm in diameter), aragonitic, poorly preserved and recrystallized, while moderately to well-preserved morphology, bimineralic, and oversized forms usually occurred in the I. Proliferation of ooids over the PâTr transition indicates an extensive range of warm waters with high level of carbonate saturation state that prevailed in the oceans during that time. In addition, oolites are often found in association with microbialites in low-latitude shallow-marine settings. They persisted into the earliest Triassic until the conodont Isarcicella isarcica Zone. Ooids became widespread over extensive regions just after the LPE during the interval corresponding to the conodont Hindeodus changxingensis Zone. Global review of 43 oolite-bearing PermianâTriassic boundary (PTB) sections with reliable biostratigraphic controls indicates that ooids occurred mostly in coincidence with the latest Permian extinction (LPE) and its immediate aftermath.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |