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

G. Lakshminarayana ¹, K. S. Murti ¹

Affiliations
1 Geological Survey of India, Chandra Vihar, Hyderabad 500 001, IN

Abstract

The Chintalapudi sub-basin, in the southeastern part of the Pranhita-Godavari Valley, was hitherto believed to contain mainly the Kamthi Formation of the Lower Gondwana Group. Recent geological mapping has brought to light the existence of the upper Gondwana sequence consisting of Kota and Gangapur Formations and also the occurrence of new areas of Talchir and Barakar Formations. Revised stratigraphic succession shows, in ascending order, Talchir, Barakar, Kamthi (Lower Gondwana). Kota and Gangapur Formations (Upper Gondwana). The Gondwana sediments are disposed in a NW-SE trending' graben affected by longitudinal and transverse faults. The Barakar Formation is identified over an area of 130sq km in Ayyanapalem-Sattupalli-Pakalagudem area, Khammam district, Andhra Pradesh. Stratigraphic drilling near Sattupalli has established the presence of coal seams with in a depth of 325 m in this newly identified Barakar Formation. The preliminary study of coal seams indicates that the coal is of Class III to Class IV type. The present study has established a new coal belt around Sattupalli in Chintalapudi Subbasins and this find is expected to augment the coal resources of the Godavari Valley considerably.

Keywords

Stratigraphy, Gondwana, Godavari Valley, Andhra Pradesh, Coal.

Full Text

     

G. Lakshminarayana ¹, K. S. Murti ¹, M. Rama Rao ¹

Affiliations
1 Geological Survey of India, Bandlaguda, Hyderabad 500660, IN

Abstract

The Raghavapuram Formation, as demarcated now, consists of shale and micaceous sandstone and contains Early Cretaceous (Neocomian-Aptian age) palynofossil assemblage-represented by Microcachryidites antarcticus, Contignisporites sp., Callialasporites sp, Lycopodiumsporites sp, Impardecispora sp, and Concavissimisporiles sp. The Tirupati Formation consists of conglomerate, ferruginous sandstone and sandstone. The hitherto considered 'Gollapalli sandstone' in Adamilli-Gopalapuram area of West Godavari district forms part of the continental Gondwana sequence (Kota Formation). Therefore, the present study has revealed that there is no stratigraphic unit called Gollapalli Formation in the Upper Gondwana of the Krishna-Godavari coastal tract and the revised stratigraphic succession consists of only two units, namely, the Raghavapuram and Tirupati Formations.

Keywords

Stratigraphy, Gondwana, Krishna-Godavari, Andhra Pradesh.

Full Text

     

T. Rajesham ¹, Y. J. Bhaskar Rao ², K. S. Murti ¹

Affiliations
1 Geological Survey of India, S. R., Hyderabad 500 660, IN
2 National Geophysical Research Institute, Hyderabad 500 007, IN

Abstract

A new terrane of granulite facies rocks-the Karimnagar granulite terrane (KGT) is identified. The KGT is ∼ 150 km x 20 km extending along NW-SE in the Karimnagar, Warangal and Khammam districts of Andhra Pradesh along the southern flank of the Godavari graben which separates the Dharwar and Bastar Cratons. The KGT is interesting because of its location far outside the known charnockitic region of south India. The important rock types in the KGT include : hypersthene granite (charnockite), two pyroxene granulite, calc-granulite and sapphirine bearing pelitic rocks. The association of sapphirine with orthopyroxene and cordierite in the pelitic rocks indicates metamorphism at pressures of ∼ 7 Kbar and temperatures of ∼ 750°C.

It is suggested that the KGT is a remnant of an Archaean supracrustal-granite association which underwent granulite grade metamorphism at ∼ 2.5 Ga ago. This ancient orogenic belt appears to have been exhumed during the early Proterozoic.

Keywords

Precambrian Granulites, Sapphirine Granulites, Dbarwar Craton, Godavari Graben, Andhra Pradesh.

Full Text

     

K. N. Srinivasan ¹, V. Ganesan ², D. Roop Kumar ¹, K. S. Murti ¹, N. V. Rao ³

Affiliations
1 Geological Survey of India, Operations: Andhra Pradesh, Hyderabad, IN
2 Geological Survey of India, Operations: Tamil Nadu, Madras, IN
3 Geological Survey of India, Operations: Andhra Pradesh, Hyderabad

Abstract

The anorthosite of Sripuram is a syn - to late - tectonic concordant intrusive into the rocks of Khammam Schist Belt (KSB). Its major element Chemistry is comparable to Archaean anorthosites.

Keywords

Petrology, Anorthosite, Granulite, Khammam Schist Belt, Andhra Pradesh.

Full Text