Development of Mesoproterozoic Fold-and-Thrust Belt Structures in Central India: New Evidence from Detachment-Controlled Deformation in the Lower Vindhyan Basin

The Central Indian Tectonic Zone (CITZ) records the Proterozoic collision between the Bundelkhand and Bastar cratons, with the adjacent Vindhyan Basin preserving evidence of deformation during the N-S convergence across CITZ. Previous interpretations associated the structural features in the Lower Vindhyan Group (LVG) to synsedimentary or seismic processes. To investigate the structural evolution of LVG and its relationship with CITZ, we conducted detailed litho-structural analysis of both the LVG and the Mahakoshal Supracrustal Belt (MSB) within the CITZ, specifically focusing on their mechanical coupling during Mesoproterozoic collisional deformation.

Our field investigations revealed polyphase deformation within the MSB, characterized by three distinct phases: (D1) E-W trending regional foliation (S1) and diversely oriented folds, (D2) E-W oriented steep folds associated with a crustal-scale shear zone along the Son-Narmada South Fault, and (D3) local cross-folds. In the LVG, we report, for the first time, characteristic fold-and-thrust belt features including buckle folds, kink bands, reverse faults, fault-related folds, and notably, 5-20 meters long outcrops of pop-up structures. The deformation style in the LVG was dominantly controlled by a mechanically weak detachment layer comprising the Kajrahat Limestone and Arangi Shale units, which enabled thin-skinned deformation within the overlying competent units of Porcellanite, Kheinjua Shale, and Chorhat Sandstone.

Based on geometric and kinematic analysis, we demonstrate that deformation in the LVG occurred between the D3 event in the MSB and the deposition of the Upper Vindhyan Group (1.5–1.2 Ga). Cross-sectional analysis reveals that the LVG deformation patterns closely mimic sandbox experiments of fold-and-thrust belt evolution, particularly in the sequential development of pop-up structures above a weak detachment horizon. We propose a tectonic model wherein the Vindhyan Basin initially developed as a peripheral foreland basin, followed by northward propagation of deformation through detachment folding mechanisms. The model involves initial northward subduction followed by polarity reversal to southward subduction, explaining both the basin formation and subsequent deformation patterns. Our findings also highlight the significance of thin-skinned tectonics in shaping structural architecture of Central India during the Mesoproterozoic period and reveal the far-field effects of cratonic collisions on basin evolution.