Facies Architecture and Sequence Stratigraphy of Tredian Formation in Zaluch Gorge, Western Salt Range, Pakistan

Abstract

The Triassic sequence is well exposed in Zaluch Gorge, Western
Salt Range. The present work focused on detailed facies
architecture and depositional setting of Tredian Formation by using
outcrop data of Zaluch Gorge, Western Salt Range. Tredian
Formation is composed of coarse grained sandy facies of the
Middle Triassic age. The thickness of the formation is 36 meters in
the Zaluch Gorge. Four lithofacies have been identified by using
outcrop data which are the cross-bedded sandstone facie (TF1), the
Greywacke facie (TF2), the massive sandstone facie (TF3) and
medium grained sandstone with carbonate cement (TF4) facie. For
the petrographic study, 12 samples of sandstone of the Tredian
Formation were collected. Three microfacies were identified during
the petrography of the Tredian Formation which are sub-arkose,
quartz wacke and quartz arenite. Cementing materials are silica,
hematite and calcite. Hematite cement is rich at bottom of the
formation and the concentration of calcite cement is high at the top.
On outcrop mainly coarsening upward sequence is marked with
minor local finning upward sequence. Maximum flooding surface,
system tracts and facies cycles have been marked on the outcrop
data. Facie analysis shows that the lower part of the Tredian
Formation was deposited in a delta lobe setting marking shallow
upward cycles. In the middle part, thick sandstone was deposited in
a fluvial setting dominated by coarsening upward cycle. In the final
stage minor fluctuation in the sea level associated carbonate
deposition. Thus, the Tredian Formation is of non-marine origin
and depicts some good reservoir characteristics.