Paleoenvironments and Genesis of Mixed Siliciclastic and Carbonate Sediments of the Upper Permian Chhidru Formation in the Salt Range, Pakistan

Abstract

 The Upper Permian Chhidru Formation In the Salt Range displays a mlxed sequence of siliciclastic and carbonate sediments. The formation Is divisible Into four lithofacies which in ascending order are: CF1 bioturbated shale with sandstone and limestone Intercalations, CF2 sandstone-limestone with shale alternations, CF3 medium to thlck•bedded sandstone and limestone, and CF4 white friable sandstone with subordinate limestone.
Various features of the Chhldru Formation’ are characteristic of shallow marine environments where mixed clastic and carbonate conditions of deposition prevailed. Mixing appears to have taken place both by punctuation as well as In situ mixing mechanisms. In general, these strata were deposited In shallowing upward conditions with a significant variance above facies CF3 where deepening occurred and facies CF2 was repeated before shallowing up again during the deposition of facies CF3 and CF4.
The shelf during deposition of the Chhldru Formation was frequently affected bystorms and there Is evidence to suggest it to be tidally influenced as well.