Khewra Sandstone Fm
Type Locality and Naming
Holotype section: Khewra Gorge, Eastern Salt Range (northern Indus Basin). Hypo: Saiyiduwali section, Khisor Range. Author: A.N. Fatmi, 1973
Synonym: Khewra Sandstone, Khewra Fm
Lithology and Thickness
Sandstone. In the type section, it consists mainly of reddish-brown to purple, thick-bedded to massive cross-bedded sandstone with few brown shale intercalations; bedding surfaces show abundant ripple marks and mud cracks, and in places exhibit convolute bedding. Towards western Potwar, the sandstone retains its purple color but becomes thin bedded with increased shale content.
Reference section: Being suggested by Nusrat K. Siddiqui. Here the lithology is mainly sandstone, with light brown-purplish color but it exhibits massive bedding, the upper part of the formation grades upward into glauconitic sandstone, which is taken to mark the base of the overlying Kussak Formation. A typical conglomerate thin bed with well-rounded pebbles, poorly cemented, is generally present on top of the formation.
Thickness: 150-300 m In the type section the formation is 150 m thick; at the suggested reference section the base is not exposed and only 80 m could be measured; further south, Marvi-1 drilled 300 m of this formation.
Relationships and Distribution
Lower contact
Conformably underlain by Salt Range Fm across a distinct contact.
Upper contact
Disconformably overlain by Kussak Fm.
Regional extent
The formation is widely exposed south of Potwar in the foothills of the Salt Range escarpment from Jogi Tilla in the east to Kalabagh in the west. Across River Indus an isolated outcrop is present at the Saiyiduwali section. Several exploratory wells in eastern Potwar penetrated the sandstone, while towards west the Permian unconformity has resulted in the complete erosion of the Cambrian succession in the subsurface. South of the Salt Range a few wells drilled through the formation, as well as in Punjab Platfrom, east of the Sulaiman Foredeep; farther south, a well Marvi-1 drilled 300 m of this formation.
GeoJSON
Fossils
The formation is essentially devoid of any fossils except rare trace fossils interpreted as trilobite trails by Schindewolf and Seilacher (1955).
Age
Depositional setting
Essentially deposited in shallow water, except the lower part that represents transgressive facies.
Additional Information
EMW: Oil and Gas.