Peninsular Gneiss
Peninsular Gneiss or Peninsular Gniessic Complex are the
Geology
The
In most stratigraphic schemes, the peninsular gneisses are shown as the younger Archaean strata situated above the
The rocks of the Dharwar Group, which are mainly sedimentary in origin, occur in narrow elongated synclines resting on the gneisses found in
.The
Geology of the Lalbagh hill monument
The Lalbagh hill, which has been declared as a Geological Monument (plaque pictured) to represent the Peninsular Gneiss, has dark
A common enclave is a dark grey to black rock called
lenticularshapes.
.
The earliest rock was a dark coloured amphibolite which was converted into grey biotite gneiss during migmatization. The grey biotite gneiss during migmatization was first intruded by grey porphyritic granite and later by pink granites. Pegamatities of several generations have traversed all these rocks.
Geological age
Initial studies on the Gneiss samples of the Lalbagh hill and other locations in Bengaluru, carried out in the early 1970s, have attributed two major events of 2.9 –3.0
Geological/Radiometric ages | Study Region/Belt |
---|---|
3.4 Ga. | The oldest Peninsular Gneiss found in areas in the Holenarsipur – Hunsur belt
|
3.3–3.2 Ga. | The second generation Peninsular Gneiss found in the Bengaluru– Chickmagalur –Holenarsipur region
|
3.0–2.9 Ga | a) 207Pb/206 Pb data.
b) In the Dharwar Craton studies done on the trondhjemites of Holenarsipur, major crust forming event are attributed through the Rb–Sr whole rock isochron ages.
c) In Zircons from amphibolite facies gneisses from Kobaladurga and Kober single zircon evaporation ages of grey gneisses have been considered
|
Thus, three major episodes, namely, 3.4 Ga., 3.3–3.2 Ga., and 3.0–2.9
The
Lalbagh
Access
The monument, located in the southern part of Bengaluru, 4 kilometres (2 mi) from the Legislature office complex of the Karnataka Government (Vidhana Soudha) within the Lalbagh gardens is easily approachable by road (Metro Map of the city in the Info box gives exact location). Bengaluru is well connected by road, rail and air with the rest of the country and is also well known internationally.[8]
Gallery
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Plaque declaring the Peninsular Gneiss as a Geological Monument
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A plaque displayed at Lalbagh gives history of the tower and the garden
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Tourist at the Lalbagh Tower on the Peninsular Gneissic Rock hill
References
- ISSN 1432-1149.
- ^ a b c "Peninsular Gneiss". Geological Survey of India. Archived from the original on 21 July 2011. Retrieved 27 February 2009.
- ^ ISSN 0254-0436.
- ^ a b "Lalbagh - Abounting with natural landmarks". Tourism Karnataka. Archived from the original on 5 January 2009. Retrieved 28 February 2009.
- ISBN 9780444415103.
- .
- ^ "stratigraphy of Asia ( in Asia: The Precambrian )". Retrieved 28 February 2009.
- ^ a b "lalbagh Botanical garden Bangalore". Mysore Horticulturtal Society, Bangalore. Archived from the original on 17 February 2012. Retrieved 28 February 2009.
- ^ "Kempe Gowdas of Bengalooru (Bangalore)". Vokkaligara Parishat of America (VPA). Retrieved 28 February 2009.
External links
- Locations Map of the 26 Nartional Geological Monuments of India
- Trans. Min. Geology Institute India, 1, 47 (1906).
- Rec. Geology Survey India, 69, 109 and 458 (1935).
- Mem. Geology Survey India, 70 (1936 and 1940).
- Explanatory brochure on Geological and Mineral Map of Karnataka and Goa Aug 1981