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Enigmatic tubular trace fossils up to eight meters long occur in the Lower Pennsylvanian Middlesboro Member of the Lee Formation. Two morphotypes occur: type 1 trace fossils are plain, smooth, vertical, nonbranching, parallel-walled, tubular structures; type 2 trace fossils branch, have walls with faint vertical striations, regularly or irregularly spaced nodes, and funnel-shaped terminations. Sandstone casts filling type 2 structures have helical spiral morphology, and, in rare individuals, faint meniscate fills have been observed. Both trace-fossil morphotypes have poorly cemented wall linings containing framboidal pyrite, amorphous carbon, quartz sand, and poorly preserved fecal material.The trace fossils occur in a massive, structureless, channel-form sandstone, originating at the contact between a channel lag and the overlying massive fill. The stratigraphic sequence is interpreted to represent a barrier island transgressing an estuarine facies. A tidal inlet within the barrier facies scoured into the underlying estuarine sediments. Subsequent rapid filling of the inlet led to the deposition of the massive sandstone.Origin of these structures is uncertain. The preponderance of evidence favors the hypothesis that the structures are escape burrows of animals that had colonized, or were concentrated in, the lag and were suddenly buried by the deposition of the massive sand. However, no likely burrower has been identified, and several characteristics of the structures and the enclosing sediments indicate that they may be completely inorganic in origin.

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.

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