Palaeoenvironments of the Permian-Triassic transition sections in Kashmir, India

摘要

Detailed measurements of two Permian-Triassic boundary sections at Guryul Ravine and Pahlgam in Kashmir indicate continuous sedimentation across the boundary, though with a marked change from shallow storm-influenced shelf to deeper shelf below wave base. Successive shell beds through the 2.5-m-thick transitional latest Permian section at Guryul formed as in situ accumulations with little sign of either erosional break or condensation. Faunal change takes place gradually in the late Permian transition beds, as elsewhere in the Tethyan sections. There is no major event layer at the Permian-Triassic boundary, and little evidence for dysaerobic conditions. Both the Kashmir and East Greenland Permian-Triassic sections have sedimentation rates that are orders of magnitude greater than at the condensed Meishan reference section. They show that the end-Permian extinction was associated with transgression but not with immediate onset of anoxic conditions. Macrofaunal extinction seems associated with reduction in primary production, which would also explain the dwarfism of fossils found in all Permian-Triassic sections studied so far.