A B C D E F G H I J K L M N O P Q R S T U V W X Y Z All
Sastry, A. V. R.
- Structure and Petrography of the Quartz-Magnetite and Associated Rocks of Vemparala Area, Nellore District, Andhra Pradesh
Authors
1 Geology Department, Andhra University, Waltair, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 9, No 1 (1968), Pagination: 49-57Abstract
In the Nellore and Guntur districts of Andhra Pradesh a series of detached hills composed of interbanded quartz-magnetite rocks, garnetiferous quartzites, pyroxene granulites, hypersthene-magnetitites and ferruginous schists extend for 33 miles from Konijedu in the south to Vemparala in the north. This paper mainly deals with the structure and petrography of the northernmost group of these rocks at Vemparala.
In this area the rocks have been metamorphosed and folded, whose axial plane trace only (FI) can be recognised. These have been folded again (FU) with eastward dipping axial planes trending NNW-SSE accompanied by gabbroic and granitic intrusions. The third folding (FIll), in the nature of a cross-fold, is along axes plunging NNE. There are many faults trending roughly N-S and E-W.
Mapping of the structure of a part of the eastern margin of the Cuddapah Basin between Cumbum and Markapur by the authors has revealed the presence of an earlier fold axis trending NW-SE and plunging due NW and a later cross-fold trending NNE-SSW and plunging due NNE. A study of the region from here eastwards to the Konijedu-Vemparala area, a distance of about 60 miles, has shown that the earlier fold axes (or axial plane traces) vary in trend, but the cross-fold axes show fairly consistent trend and plunge due NNE. It is therefore suggested that this region as a whole must have been affected by one and the same set of tectonic forces during its last stage of deformation.
- Joint Patterns and their Significance to the Tectonic History
Authors
1 Department of Geology, Andhra University, Waltair, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 11, No 4 (1970), Pagination: 386-391Abstract
On the basis of the relative intensity of the tectonic disturbances in the Medivada-Vaddadi area in Visakhapatnam district of Andhra Pradesh, the area is subdivided into two domains, homogeneous and inhomogeneous, for the purpose of the study of joints, The subdivision of this contiguous area into two distinct domains is corroborated by applying the Snedecors F-test for the equality of variances for the variables - strike and dip of the joints and the test for the equality of covariances for the variates - strike and dip taken together.
Only in the inhomogeneous domain there is superposition of the low-angled joint pattern on the pre-existing joint pattern consisting of three sets of joints - J1, J2, J3.
The first order joints J1, J2 and J3 might have probably formed during the folding of the beds, and the second order joints with low dips were formed during the readjustment of stress after the folding, jointing and faulting.
The application of the results of the study of the joints to the mineralised zones in areas of superimposed tectonic deformation is indicated.
- Structure and Petrography of the Quartz-Magnetite and Associated Rocks of Siddipet Area, Medak District, Andhra Pradesh
Authors
1 Geology Department, Andhra University, Waltair, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 13, No 1 (1972), Pagination: 21-29Abstract
A series of detached hills composed of quartz-magnetite rocks and diabases occur in the districts of Medak, Nizamabad, Adilabad and Karimnagar of Andhra Pradesh. The country rock is granitic gneiss and is cut across by a number of dykes. The structure of these rocks near Siddipet in Medak district has been studied in detail, and a number of traverses also made between Armur and Jagtial to the north in the districts of Nizamabad and Karimnagar to infer the probable overall structure of the region.
The quartz-magnetite rocks contain quartz and magnetite only and are devoid of ferro-magnesian minerals. The diabases in the Siddipet area are divided into two groups, one rich in hornblende and the other in pyroxene on the basis of petrographic study.
From a study of the outcrop pattern of the quartz-magnetite rocks and diabase bands in the Siddipet area, three traces of axial planes of folds (FI, FII, FIII) possibly related to three ages of folding are inferred. These rocks have been faulted along N-S and NE-SW directions. From the overall pattern of outcrop of these rocks in the entire region, it is surmised that the rocks of Siddipet area form a part of a major NW plunging anticline with an overturned western limb and with the nose of the fold being near the Godavari river.
- Polyphase Deformation and Metamorphism in the Magnetite-Quartzites of Prakasam District, Andhra Pradesh
Authors
1 Department of Geology, Andhra University, Waltair, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 16, No 1 (1975), Pagination: 102-104Abstract
No Abstract.Full Text
- Welded Tuffs from Mangampeta, Cuddapah District Andhra Pradesh
Authors
1 Geology Department, Andhra University, Waltair-530003, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 20, No 12 (1979), Pagination: 615-618Abstract
Close association of peralkaline vitric crystal tuffs (welded) with the massive dark grey stratified barytes deposit is reported. Megascopic and microscopic description of the rocks reveal that these rocks are of eruptive origin.
Chemical analyses of three representative rock samples are given. Peculiar chemical characteristics are discussed.
- Occurrence of Sulphur Crystals in Sediments from Northwestern Part of Lower Bengal Fan
Authors
1 Department of Geology, Andhra University, Visakhapatnam-530003, IN