In the geologic timescale , the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided in chronostratigraphy . The Middle Triassic spans the time between 247.2 Ma and 237 Ma (million years ago). It is preceded by the Early Triassic Epoch and followed by the Late Triassic Epoch. The Middle Triassic is divided into the Anisian and Ladinian ages or stages .
4-446: The Guanling Formation is a Middle Triassic ( Anisian or Pelsonian in the regional chronostratigraphy) geologic formation in southwestern China . The formation encompasses two members. The first member is primarily calcareous mudstone and dolomite , indicative of a coastal environment. The second member is a thicker marine sequence of dark micritic limestone with some dolomite. Two distinct fossil assemblages are found in
8-542: A whole was deposited over a period of 340 ± 71 kyr. This estimate is justified by cyclostratigraphic evidence, as indicated by fluctuations of terrestrial proxy metals. Among others, the following fossils were reported from the formation: Middle Triassic Formerly the middle series in the Triassic was also known as Muschelkalk . This name is now only used for a specific unit of rock strata with approximately Middle Triassic age, found in western Europe. Following
12-514: The Permian–;Triassic extinction event , the most devastating of all mass-extinctions, life recovered slowly. In the Middle Triassic, many groups of organisms reached higher diversity again, such as the marine reptiles (e.g. ichthyosaurs , sauropterygians , thallatosaurs ), ray-finned fish and many invertebrate groups like molluscs ( ammonoids , bivalves , gastropods ). During
16-468: The second member. The older Luoping biota preserves abundant arthropods along with fossils from other invertebrates and vertebrates , which are rare but well-preserved. The slightly younger Panxian fauna has a more diverse and common assortment of marine reptiles such as sauropterygians . A tuff bed in the Luoping biota has been dated to 244.5 ± 2.2 Ma via U-Pb SHRIMP dating. The Luoping biota as
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