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

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Barr Conglomerate: Its Recognition and Significance in the Stratigraphy of the Delhi Supergroup in Central Rajasthan


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1 Department of Geology, Presidency College, Calcutta 700 073, India
     

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The lithostratigraphic units of the Delhi Supergroup are well exposed around Barr (26° 05': 74° 06'). Field, petrographic and geochemical observations from these units suggest that the lithofacies changes from lower arenaceous Alwar Group with basal polymictic conglomerate to the upper impure calcareous-cum-argillaceous Ajabgarh Group. The Barr conglomerate is truly a genuine sedimentary rock with assortment of pebbles and cobbles of quartzite, granite-gneiss, chert and mica schist. However, the conglomerate has been deformed along with other lithostratigraphic units of the Delhi Supergroup. Tectonically formed boudins can be distinguished from clastic pebbles and cobbles. The recognition of the sedimentary origin of the Barr conglomerate is useful in discussing the nature of Delhi-PreDelhi contact on the western flank of the 'Delhi synclinorium'.
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  • Barr Conglomerate: Its Recognition and Significance in the Stratigraphy of the Delhi Supergroup in Central Rajasthan

Abstract Views: 268  |  PDF Views: 2

Authors

P. K. Gangopadhyay
Department of Geology, Presidency College, Calcutta 700 073, India
Amitava Lahiri
Department of Geology, Presidency College, Calcutta 700 073, India

Abstract


The lithostratigraphic units of the Delhi Supergroup are well exposed around Barr (26° 05': 74° 06'). Field, petrographic and geochemical observations from these units suggest that the lithofacies changes from lower arenaceous Alwar Group with basal polymictic conglomerate to the upper impure calcareous-cum-argillaceous Ajabgarh Group. The Barr conglomerate is truly a genuine sedimentary rock with assortment of pebbles and cobbles of quartzite, granite-gneiss, chert and mica schist. However, the conglomerate has been deformed along with other lithostratigraphic units of the Delhi Supergroup. Tectonically formed boudins can be distinguished from clastic pebbles and cobbles. The recognition of the sedimentary origin of the Barr conglomerate is useful in discussing the nature of Delhi-PreDelhi contact on the western flank of the 'Delhi synclinorium'.