Permo-Triassic cyclicity on the western shoulder of Muzaffarabad-Hazara paleo-high, during the oceanisation of Neo-Tethys

Abstract

The sedimentary record of Permo-Triassic (299 Ma to 201 Ma) is only found on the periphery of the Hazara-Kashmir Syntaxis (HKS), i.e., on the western (central Potwar Sub-basin and its west) and eastern (Zanskar-Spiti Basin) shoulders. During this period, HKS acted as an indentation named as Muzaffarabad-Hazara Paleo-high (MPH), where no sedimentation occurred. Previously, the existence of MHP remained questionable as it has yet to be defined with the help of an integrated sequence stratigraphic model built by using outcrop, petrography, drilled well, regional correlations, seismic and gravity data sets on its western shoulder.Permo-Triassic strata outcrop in the western Salt Range, where stratigraphic surfaces, stratal terminations, and their bounding sequences are designed. Permo-Triassic is a mega sequence comprising of two sequences (Permian and Triassic) bounded by SUs. Non-marine (fluvial) Warchha Sandstone split the Permian sequence into two sub-sequences (siliciclastic/clastic and carbonate sequences). The Triassic sequence has the same depositional architectural features have two sub-sequences. Flooding events (i.e., four MRS/MFSs) influenced every sub-sequence, which developed retrogradational and progradational cyclicity during this period. The defined cyclicity, stratigraphic surfaces, and stratal terminations are validated with the well-log motif cycles and seismic data.Composite unconformities developed towards the MHP; therefore, only flooding events are correlatable on both shoulders. During the Sakmarian (290 Ma) age, a flooding event with maximum accommodation space (15–20 m) deposited the middle shelf facies (Amb Formation), which is correlatable with carbonates of Panjal volcanics and transgressive Gechang Formation of Zanskar-Spiti Basin. The third flooding event of the Ceratite Bed of Lower Triassic is also correlatable. Flooding continued in Zanskar-Spiti Basin in Middle Triassic, but diastem was observed in the western Salt Range. Carbonates younger than Ladinian (242-237 Ma) age are only found in Zanskar-Spiti Basin, but during this phase, SU truncated the Triassic strata in the Salt Range.