Stratigraphic Studies of the Nowshera Reef Complex, Nowshera Tehsil, West Pakistan
Abstract
A belt of Siluro-Devonian limestone and quartzite, pink or yellowish-pink in colour, is exposed on either side of the Nowshera-Risalpur road. This belt was identified as a 'Reef Complex' in 1965, and is the first of its kind to be discovered in the lndo-Pak sub-continent. Prior to this discovery, the limestone belt had been erroneously assigned a Precambrian age and regarded as part of the Attock Slates.
The entire belt unconformably overlies the Kandar Phyllite and is divisible into four definite units: 1. Carbonate Rocks, 2. Reef Core, 3. Reef Breccia, and 4. the Misri Banda Quartzite. The first three collectively are known as the Nowshera Formation. With the exception of the last, these units represent the characteristic structural layers of a reef.
The age of the reef complex on the basis of its fossil assemblage ranges between Upper Silurian and Devonian. However, there is no fossil present which may pinpoint an exact age. The uncertainity about the precise age of the reef is largely due to the destruction of many organisms by the process of dolomitization.
In the opinion of the writers, the Nowshera Formation and the Misri Banda Quartzite were deposited in the southernmost extremities of the basin in which the Muth Quartzite, of Siluro-Devonian age, was formed. In their opinion, the Nowshera Formation and the MisriBanda Quartzite can be correlated with the middle and upper parts of the Muth Quartzite.
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