Fracture Fills or ‘Sedimentary Dykes’ in the Lake Sediments of Jalala, NWFP, A Preliminary Report
Abstract
Quaternary lake sediments of Jalala in Mardan District are intersected by discordant structures which have been described as clastic dykes by Allen (1964). These sediments consist of horizontal, alternate beds of clay, silt and sand with local pockets of erratics. Poor sorting, angular to subangular shapes of the grains, and varied mineralogy indicate short distance of transport. Metasediments, amphibolite and granitoids are among the possible source rocks. Field evidences indicate that episodic tectonic activity produced fractures in the sediments which were filled by the plastic flow of clayey material from the overlying beds.
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