Pyroclastic volcanism in Papaghni sub-basin, Andhra Pradesh: Significant Paleoproterozoic tectonomagmatic event in SW part of the Cuddapah basin, Eastern Dharwar craton

Abstract

Detailed field and petrological studies in Vanambayi-Lingala-Lopatnutala section and old Kadiri Ghat-Pulivendela section in SW part of the Proterozoic Cuddapah basin of Eastern Dharwar craton brought to light the occurrence of hitherto unreported two significant phases of pyroclastic volcanic activity associated with the Vempalle Formation in Papaghni sub-basin. Occurrence of a significant pyroclastic agglomerate at the contact zone of Vempalle dolomite of Papaghni Group and Pulivendela quartzite of Chitravathi Group represents a significant event of the mafic phase of pyroclastic volcanic activity, while the finely laminated felsic tuff within the intercalated reddish siltstone, chert and dolomite sequence in the lower part of Vempalle Formation represents the felsic phase of pyroclastic activity. Studies indicate that the pyroclastic agglomerate zone in Vanambayi-Lingala-Lopatnutala section is a classical example of pyroclastic volcanism wherein the highly vesicular rock with rounded basalt clasts often exhibit embayed contact of welded nature with the matrix. The pyroclastic zone reported in the present paper particularly at the interface of Vempalle Formation and Pulivendela quartzite in Vanambayi-Lingala-Lopatnutala section represents a significant tectono-magmatic event of explosive volcanic activity that is contemporaneous with the culmination of the carbonate precipitation of Vempalle dolomite and marks the termination of sedimentation in Papaghni Group in southwestern part of Cuddapah basin during Paleoproterozoic times.