Depositional Settings of Early Carboniferous Siliciclastic-Carbonate Succession (Syringothyris Limestone) of Kashmir Himalaya

摘要

Early Carboniferous sequence of Kashmir represents a mixed siliciclastic-carbonate strata, where the lower part is dominated by carbonates and the upper part is rich in siliciclastic rocks. Siliciclastic sediments are mainly arenite, siltstone and claystone. Coarse grain size and bimodality of arenites suggest a high energy environment in the onshore region. Lithofacies and microfacies analyses of the carbonates reveal that they are deposited as turbidite either in the deeper part of the shelf or in the distal part of shelf/slope. Some of the carbonate facies, reflecting shallower microfacies, is deposited on the platform in subtidal and intertidal (peritidal) zone. The increase of siliciclastic material in the depositional basin indicates progradational phase of sedimentation which in turn suggests the lowering of sea level. These deposits represent peritidal (intertidal to subtidal) lithofacies. In fact, there has been retrogradational and progradational phases of sedimentation in the Tethyan basin of Kashmir, but the frequency of siliciclastics increases from middle to top of the Syringothyris Limestone. This feature suggests the overall shallowing of the basin, but intermittent deposition of carbonates reveals the periodic transgression or subsidence of the depositional basin.