A Relook into the Status of Granitoids and Conglomerate in Salumber- Jaisamand Area, Southern Rajasthan: Implications for the Stratigraphy of the Palaeoproterozoic Aravalli Fold Belt

Detailed geological mapping (1 :25,000) of the Jaisamand-Salumber area in south Rajasthan has brought out modifications and additions to the existing published maps. Significant modifications in the outcrop pattern relate to the disposition of (a) polymictic conglomerate, feIdspathic quartzite and calcareous quartzite-dolomite unit in the Ora- Jaisamand area, (b) granitoid bodies, and (c) polymictic conglomerate occurring southwest of Salumber. A better understanding of the inter-relationship of significant litho-units has necessitated a relook into the Aravalli stratigraphy of the area, particularIy with respect to the granitoids and conglomerate. Geological mapping has also helped in identifying some stratigraphically important litho-units, such as polymictic conglomerate from northwest of Paluna, calcareous grit1 calcareous quartzite-dolomite from west of Piladhar, and calcareous quartzite-dolomite along the northeastern limb of Ora - Jaisamand anticline. The Aravalli sequence exposed in the area can be divided into Salumber Group (lower Aravalli) and Jaisamand Group (upper Aravalli), separated by an unconformity. The two groups also differ in lithologic assemblages. The granitoids are intrusive into the volcano-sedimentary sequence of the Salumber Group and form the basement for the Jaisamand Group. On the basis of overlapping relationship with Salumber Group litho-units and clast composition, the stratigraphically controversial Ora-Jaisamand-Salumber conglomerate and correlatable units have been interpreted as the basal unit of the Jaisamand Group (upper Aravalli).