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Principal reference section for part of the Eocene Ghazij Formation, Moghal Mine area, Mach coal field, Balochistan, Pakistan

Miscellaneous Field Studies Map 2263-D

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Abstract

The information presented on this sheet was collected as part of a joint U.S. Geological Survey-Geological Survey of Pakistan program sponsored by the U.S. Agency for International Development. As a project within this program, the coal-bearing Ghazij Formation (Eocene) was investigated in the northeastern part of Balochistan cast and south of the provincial capital of Quetta. Strata exposed in this area range in age from Permian to Holocene and crop out as a belt of folded and thrusted rocks that form a southeast-facing orocline. In this region of Pakistan, the Ghazij can usually be divided into three parts. The lower part is the thickest (probably more than 1,000 m) and consists of gray-weathering calcareous mudrock (shale, mudstone, and impure claystone) and a few tabular bodies of fine-to medium-grained calcareous sandstone. The middle part (27-300 m) consists of gray-weathering calcareous mudrock and tabular to lenticular bodies of fine-to medium-grained calcareous sandstone; beds of carbonaceous shale and coal are common. The upper part (as thick as 533 m) contains reddish-weathering calcareous mudrock that contains scattered lenticular bodies of fine- to medium-grained calcareous sandstone. Fossil plant debris is common in mudrock of the lower and middle parts of the Ghazij, and bivalves and gastropods are common in the middle part; the upper part of the Ghazij is usually unfossiliferous. This three-fold division of the Ghazij is less distinct in the Johan area. Here, the upper part of the formation is clearly identifiable, but rocks below it are poorly exposed and assigning a stratigraphic level that separates the middle and lower parts of the formation is problematic. Below the upper part of the formation is a thick sequence of greenish-gray calcareous mudrock that contains locally abundant plant debris and isolated bodies of brown-weathering sandstone. Rare carbonaceous shale and even rarer coal are present in the upper part of this sequence, and this interval of the formation might correspond to the middle part of the Ghazji exposed in areas to the north. We propose that, in the Johan area, those rocks below the upper part of the formation be referred to as the main body of the Ghazij (for example, main-body Ghazij). Underlying the Ghazij are the carbonate rocks of the Paleocene Dungan Formation (or its equivalent), and overlying the Ghazij are the mostly carbonate rocks of the Eocene Kirthar Formation (or its equivalent). Both contacts can be conformable or unconformable. All of the pre-Neogene rocks in Balochistan are greatly deformed by the collision of India and Asia. The Ghazij is especially susceptible to regional compressional tectonics because it contains a large amount of shale and is sandwiched between two thick carbonate units. As a result, bedding-plane faults and isoclinal folds are common.

As part of our study of the Ghazij Formation, five stratigraphic sections were measured: one near Pir Ismail Ziarat, one in the Sor Range, two in the vicinity of Mach, and one near Johan. Each area's section is published separately.

Additional publication details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Principal reference section for part of the Eocene Ghazij Formation, Moghal Mine area, Mach coal field, Balochistan, Pakistan
Series title:
Miscellaneous Field Studies Map
Series number:
2263
Chapter:
D
Year Published:
1994
Language:
English
Publisher:
U.S. Geological Survey
Description:
Report Cover: 1 p.; Map: 53.88 x 29.49 inches
Country:
Pakistan
State:
Balochistan
Scale:
0