--> Abstract: Evidences of Igneous Diapirism in Northern Part of Narmada Block, Cambay Basin, India, by Rangarajan Sreenivasan; #90072 (2007)

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Evidences of Igneous Diapirism in Northern Part of Narmada Block, Cambay Basin, India

Rangarajan Sreenivasan
Oil & Natutral Gas Corporation Limited, Jorhat, Assam, India

The arcuate Cambay Rift Basin situated near the northwestern margin of Indian Peninsula hosts Tertiary and Quaternary sediments. It is almost entirely covered with Quaternary alluvium, save for the exposure of Tertiaries along a few ENE-WSW trending elongate domes in the southern part. Reflection seismic data over one of the domes indicates an episode of uplift at the end of Paleocene that gave rise to sharp angular unconformity. It is proposed that this was a result of a series of thermo-mechanical events associated with rifting in the basin. Seismic data also indicate a recently formed large-scale anticline in the subsurface. This feature has earlier been variously interpreted to have arisen due to compressive stresses from Himalayan orogeny or due to wrench movements along Narmada Geofracture Zone bordering the dome in the north or as uplift. It is argued in this paper that the feature is an uplift and that the earlier explanations are untenable. The recent uplift is inferred to be due to ascent of magma beneath the feature. The sharp downwarping of sediment beds bordering the uplift in the north is interpreted as a collapse feature arising out of withdrawal of magma. This, together with the coeval ascent beneath the anticline, indicates diapiric movement of magma. This is perhaps the first instance of demonstration of diapiric movement of magma on reflection seismic data.

 

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece