Kachchh Mesozoic Domes, Western India: Study of Morphotectono Character and Evolution

Kachchh domes are recognized by the oval to elliptical- shaped outcrop patterns marked by outlines of bedding surfaces which invariably dip in the outward directions. The occurrence of domes in rows without having corresponding basin-like features implies that these are not superposed folds resulting due to constriction- type tectonic forces. Further, in spite of the close time-space relationship, the occurrence of domes is exclusively in the Mesozoic rocks on the uplifted block of the fault. The absence of any such rock formation on the other side of the fault rules out the possibility that these are 'drape folds' developed during the adjustment of the sedimentary blanket over the faulted-up edges of the basement blocks. Hinging on the evidence of intrusive plutonic (mafic) masses in the core of some of the domes, we suggest that the structures evolved through diapiric rise of magma bodies causing dome-shaped up-warping (bending) of the pre-existing (Mesozoic) flat-lying sedimentary formations. Linear disposition of domes is explained as due to channellization of magma along the fractures that developed around large-scale crustal doming during the early phase of the Reunion Plume impingement under the Indian Lithosphere.