In which regions of India oldest gneissic rocks are found?
The Archean gneisses and schists, which are the oldest rocks of the Indian Shield, constitute a considerable area of Peninsular India. The Dharwar (Super Group) and the Peninsular Gneissic Complex are the classified groups of the Precambrian rocks of India.
In which city will you find oldest exposed rock mass also known as Peninsular Gneiss?
the city of Bangalore
One of the amazing things about the city of Bangalore is that it sits on a natural wonder… the rock that the city sits on is one of the oldest exposed rocks in the world. This wonder of Nature, called Peninsular Gneiss, is so easy to see.
What is gneissic banding?
The minerals in gneiss are arranged into layers that appear as bands in cross section. This is called gneissic banding. The darker bands have relatively more mafic minerals (those containing more magnesium and iron).
What are the characteristics of gneiss?
Gneiss is a medium- to coarse-grained, semischistose metamorphic rock. It is characterized by alternating light and dark bands differing in mineral composition (coarser grained than schist). The lighter bands contain mostly quartz and feldspar, the darker often contain biotite, hornblende, garnet or graphite.
What is found mostly in Gondwana rocks?
Gondwana rocks contain nearly 98 per cent of India’s coal reserves. Gondwana coal is much younger than the Carboniferous coal and hence it’s carbon content is low. They have rich deposits of iron ore, copper, uranium and antimony also. Sandstones, slates and conglomerates are used as building materials.
Where is Dharwar System of rocks?
Dharwar system Dharwar Rock System is special because it is the first metamorphic sedimentary rocks in India. They are named Dharwar system because they were first studied in Dharwar region of Karnataka. But they are also found in Aravallis, Tamil Nadu, Chotanagpur plateau, Meghalaya, Delhi, and the Himalayas region.
What is peninsular region?
The Peninsular India comprises the diverse topological and climatic patterns of South India. The narrow strip of verdant land between the Western Ghats and the Arabian Sea is the Konkan region; the term encompasses the area south of the Narmada as far as Goa.
What is the composition of peninsular?
the peninsular plateau is composed of old crystalline, igneous and metamorphic rocks. it was formed due to the breaking and drifting of gondwanaland and the making the part of oldest landmass.
What causes gneissic banding?
The banding is usually due to the presence of differing proportions of minerals in the various bands; dark and light bands may alternate because of the separation of mafic (dark) and felsic (light) minerals. Banding can also be caused by differing grain sizes of the same minerals.
How does sandstone become gneiss?
Gneiss can be formed from a sedimentary rock such as sandstone or shale, or it can be formed from the metamorphism of the igneouse rock grantite. Gneiss can be used by man as paving and building stone. Non-Foliates are metamorphic rocks that have no cleavage at all.
What is Gondwana Flora of world?
Introduction to Gondwana Flora of India: Later the term ‘Gondwana System’ was published by Ottokar Feistmantel (1876), comprising of continental rock formation with coal seams and fossil plants and animals of the Upper Palaeozoic as well as Mesozoic Eras.
What is meant by peninsular gneiss?
Peninsular Gneiss. Peninsular Gneiss is a term coined to highlight the older gneissic complex of the metamorphics found all over the Indian Peninsula. This term was first fashioned by W.F.Smeeth of the Mysore Geological Department in 1916 based on the first scientific study of this rock exposure.
What is the Archaean peninsular gneiss of southern India?
The Archaean Peninsular Gneiss of southern India is considered by a number of workers to be the basement upon which the Dharwar supracrnstai rocks were deposited. However, the Peninsular Gneiss in its present state is a composite gneiss formed by syn-
Were the supracrustal rocks deposited on a gneissic basement?
Tonalitic pebbles in conglomerates of the Dharwar Supergroup confirm the inferenoe that the supracrustal rocks were deposited on a gneissic basement. Whole rock Rb-Sr ages of gneisses showing only the DhF1 structures fall in the range of 310(O3200 Ma.
What is gneiss rock?
It is also called the Lalbagh rock. As general information, gneiss is a coarse-grained high grade metamorphic rock formed at high pressures and temperatures in which light and dark mineral constituents are segregated into visible bands.