Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

V. Natarajan ¹, S. Rajagopalan Nair ¹

Affiliations
1 Geological Survey of India, Andhra Pradesh Circle (N), Hyderabad 500029, IN

Abstract

In the northeast part of the Palnad Basin, Krishna district, Andhra Pradesh, interesting structural features are noticed in Precambrian sedimentary rocks. A prominent thrust which has brought the Cumbums over the younger Kurnools, and other primary and secondary structures in the rocks are significant and help in deciphering structural events. The thickness of the Narji limestones based on the structural studies is estimated to be 300 m and not 6400 m as suggested by Heron.

Full Text

     

K. Srinivasa Rao ¹, T. Sreenivasa Rao ², S. Rajagopalan Nair ³

Affiliations
1 6-3-628/8/1, Ravindra Nagar, Khairatabad, Hyderabad 500004, IN
2 Barkatpura, Hyderabad, IN
3 Ananda Nagar, Khairatabad, Hyderabad 500004, IN

Abstract

The lithostratigraphic succession worked out for the Upper Precambrian of Venkatapuram-Cherla area includes Cherla Formation, Somandevara Quartzite, Tippapuram Shale Utlapalli Conglomerate, Albaka Sandstone, Nambi Breccia and Doli and Usur Sandstones. Three disconformities, one each at the base of the Somandevara Quartzite, Utlapalli Conglomerate and the Nambi Breccia, have been inferred. Of these, the one at the base of the Nambi is believed to be the most significant one. Based on gross lithological similarity and relative stratigraphic position, the different Upper Precambrian units of this area are correlated with those of the already established Pakhal and Sullavai Groups of the main Upper Precambrian belt, west of the Godavari River. The correlation implies that the nature of the contact between the Pakhal and Sullavai Groups of the, main Upper Precambrian belt on the western side of the Godavari, a much debated question, is a profound unconformity.

Full Text

     

V. Natarajan ¹, S. Rajagopalan Nair ², J. K. Nanda ³, H. Sarvothaman ⁴

Affiliations
1 3-4-756 A/I, Barkatpura, Hyderabad, IN
2 10-2-317/22, Vijayanagar Colony, Hyderabad, IN
3 12-2-111/A, Muradnagar, Mehdipatnam, Hyderabad, IN
4 3-4-448,2/1, Narayanguda, Hyderabad, IN

Abstract

A number of laterite cappings have been demarcated over the Deccan Trap basaltic rocks in parts of Medak and Nizamabad districts of Andhra Pradesh. Favourable lithology of traps and a geomorphic surface with almost gentle unidirectional slope from south to north appear to have strongly influenced the lateritisation process in the area that resulted in thick lateritic cappings.

Full Text