Dharwar Succession Karnataka: Basis for Division

The Dharwar Supergroup in Karnataka represents a significant Precambrian sedimentary and volcanic sequence. Its division into Lower and Upper Dharwar is based on major geological events and dating methods, distinguishing distinct phases of deposition and tectonic activity.

Basis for Stratigraphic Division

The classification of the Dharwar succession relies on key geological indicators:

• Unconformity: Major unconformities represent significant gaps in the geological record, often indicating periods of erosion or non-deposition. These breaks are crucial markers for dividing rock sequences into distinct stratigraphic units. A significant unconformity exists within the Dharwar sequence, serving as a primary basis for separating the Lower and Upper Dharwar groups.
• Geochronological Data: Radiometric dating techniques provide absolute age estimates for rock formations. Geochronological data helps establish the timing of deposition and events, allowing geologists to define boundaries based on age differences. This data confirms distinct age ranges for the Lower and Upper Dharwar units.
• Fossil Evidence: While fossils are vital for dating younger rock sequences (Phanerozoic), Precambrian rocks like the Dharwar succession contain very limited and simple fossil evidence (stromatolites, microfossils). Therefore, fossil evidence is not the primary basis for dividing the Dharwar succession into Lower and Upper parts.
• Economic Minerals: The Dharwar rocks are known for valuable mineral deposits (e.g., iron ore, gold). However, the presence or type of economic minerals is a consequence of geological processes within the formations, not a fundamental criterion for defining the stratigraphic boundaries themselves.

Therefore, the Dharwar succession of Karnataka is divided into Lower and Upper Dharwar primarily based on the presence of a major unconformity and supported by geochronological data.