Tectonostratigraphy of the Late Archean Dharwar Supergroup, Dharwar Craton, India: Defining a tectonic history from spatially linked but temporally distinct intracontinental and arc-related basins

摘要

The Dharwar Supergroup comprises the unconformity bound Bababudan and Chitradurga groups. The Bababudan Group, which is best preserved in the Western Dharwar Craton, records a divergent margin comprising a basalt-dominant intracontinental rift sequence, a shale-BIF drift sequence, and a sandstone-shale thermal-subsidence sequence. The rift stage evolved from similar to 2765 Ma to similar to 2720 Ma, whereas the succession was folded, uplifted and eroded during development of a convergent continental margin from similar to 2680 Ma. Ocean opening was to the east or southeast. The Chitradurga Group records a two-stage back-arc basin behind an eastfacing continental arc. Stage I evolved between similar to 2609 Ma and similar to 2582 Ma, and Stage II between similar to 2582 Ma and similar to 2540 Ma. The two stages are separated by a subaerial unconformity. Stage I comprises siliciclastic fluvial, shallow-marine and deep-marine sedimentary rocks and bimodal volcanic rocks. Stage I is best preserved in the Western Dharwar Craton, but there are equivalents in the Eastern Dharwar Craton. Stage II in the Western Dharwar Craton comprises deep-marine turbidites of siliciclastic and volcaniclastic provenance, and basaltic and felsic volcanic rocks. Volcanic Stage II sequences in the Eastern Dharwar Craton define an arc-adjacent position. Tectonically driven cyclic uplift and erosion were responsible for the mismatch between preserved stratigraphic thickness and time, particularly for Stage II sequences. A remnant of a < 2540 Ma late-stage basin in the northeast of the Eastern Dharwar Craton defines a syncollisional tectonic setting. The Dharwar Supergroup was deformed in a SW-verging hinterland magmatic fold/thrust belt from similar to 2540 Ma.