The stratigraphy and coal resource potential of the Sohnari Member of the Laki Formation in Sindh Province, Pakistan; a progress report

Abstract

This progress report releases new data on the stratigraphy and lithology of the Paleocene Sohnari Member of the Laki Formation. Sixteen new outcrop sections were measured in the area between Thatta and the north end of the Lakhra Anticline, and two new mine sections were measured in the Meting-Jhimpir Coal Field. This report also re-evaluates existing data about the Sohnari member published in SanFilipo and others (1988), SanFilipo and others (1989), Outerbridge and others (in press) and Wnuk, Fariduddin, Fatmi and SanFilipo (in press). The Sohnari Member ranges between 4 and 58 m in thickness and is primarily composed of shale/claystone (65%) and sandstoxfe (21%) with minor percentages of siltstone, mudstone, conglomerate, and coal. Coal has not been found in outcrop but is widespread in the subsurface, occurring in 91% of the core holes. Coal accounts for 0% to 5% of the total thickness of any one section; the thickest bed reported is 1.78 m thick. The Sohnari was deposited in neritic tidal flat, estuarine, and coastal swamp and marsh environments. It grades downward into the mixed marine elastics and foraminiferal carbonates of the Lakhra Formation. Upward the Sohnari becomes less terrestrial/coastal and more marine in aspect, gradincp into Lakhra-like marine elastics. There is a sharp contact between the Sohnari Member and the overlying Meting Limestone and Shale Member of the Laki Formation. On the basis of lithology, a depositional hiatus of unknown duration is inferred at this contact.

Middle and late paleocene angiosperm pollen from Pakistan

“…In outcrop, the Sohnari Formation is mainly ferruginous clay and sandstone, but in the subsurface it is mainly carbonaceous shale, sandstone, and coal, very similar in general lithology and apparent depositional setting to the Bara Formation. In outcrop an unconformity seems to be present between the mainly detrital rocks of the Sohnari Formation and the overlying limestones of the Laki Formation (Wnuk et al, 1991b), but in cores, at least at some localities, the contact is gradational and therefore apparently conformable (Outerbridge et al, 1991).…”

Coal resource potential of Afghanistan

“…In general, the oldest deposits are found in the northwest of Pakistan; coals become progressively younger towards the southeast. Coal deposits are reported from the early Palaeocene Hangu Formation in Khyber Pakhtunkhwa, Pakistan (Warwick et al 1995;Qazy 2005); the stratigraphically higher Palaeocene Patala Formation in the Salt Range, Punjab, Pakistan (Warwick and Shakoor 2007); the Palaeocene Bara Formation (Frederiksen 1992;Wnuk et al 1993) and the latest Palaeocene Sohnari Formation coals, both on the Lakhra Anticline in Sindh, Pakistan (Wnuk et al 1991;Fatmi 1992a, 1992b); the Palaeocene/Eocene Bara(?) Formation in the Thar Desert, Pakistan (Fassett and Durrani 1994) and coals in various formations in the Barmer, Nagaur, and Palana Coalfields Rajasthan, India Rana et al 2005;Tripathi et al 2009 among others); early Eocene coals in the Gujarati coalfields outside of the Cambay Basin (Garg et al 2011;Rao et al 2013;Saraswati et al 2014 among others); and early Eocene Kadi Formation (Chowdhary and Singh 1978) and middle Eocene Kalol Formation (Mathur 1986) coals within the Cambay Basin.…”

Energy Dispersive X-Ray Spectroscopy of the Sohnari Member of Laki Formation from Southern Indus Basin of Pakistan

“…The general stratigraphy of the study area is very much interesting in the research. The oldest stratigraphic unit is Bara Formation (Middle Paleocene age), [9]. The second oldest unit is Lakhra Formation (Late Paleocene).…”