Paleoproterozoic thick-skinned tectonics in the Central Indian Tectonic Zone: implications on the tectonic reconstructions of cratonic nuclei

ABSTRACT

The Satpura Mountain Belt, or the Central Indian Tectonic Zone (CITZ), is a Paleoproterozoic mountain belt of Central India, with Mesoproterozoic and Neoproterozoic rejuvenation history. Structural studies carried out in the southern margin of this ancient orogenic belt have identified a two-phase evolution. The documentation of mapped fold interference of Type 2 ‘boomerang-shaped’ pattern and the spread of early lineations over the hinge area of second-generation folds provide an estimate of ~40-43° angle between the regional axial directions of the folds of the two orogenic episodes. The map patterns indicate the presence of basement-involved recumbent fold nappes placed above the sedimentary cover sequence. The identified décollement structure on the surface provides information regarding the deformation of the upper crust in ductile manner. The patterns of the deep crustal reflectors mapped through previous deep seismic reflection study interpreted during the present investigation brought out the thick-skinned deformation in the region as well as identification of crustal low-velocity zones of lower strength and a domal geometry of the lower crust. The regional thrusts are found to deform deeper crustal layers, one thrust affecting the crust-mantle boundary. The behaviours of the upper and lower crust in terms of rheological layering have been used to interpret the regional structural style of the lithosphere. The structural features of the region do not support the argument regarding the status of the Central Indian Shear as a suture, but indicate it to be the outermost emergent thrust towards the foreland side. The patterns of dip of the thrusts and thrust transport directions indicate a northward dip of the South Indian Block during the subduction stage and the position of the collisional suture of the Satpura orogen to the north of the Sausar belt. A tectonic model has been proposed here to explain the formation of the Satpura Mountain Belt or CITZ involving subduction-collision at ~2250 Ma, followed by erosion, stretching and basin development between 2100 and 1500 Ma. A collisional event in the eastern and western craton margins of India, at ~1500 Ma, caused the second uplift of the Satpura Mountain Belt and its northern margin, developing a temporal unconformity of ~300 Ma gap between the Semri and Kaimur Groups (Vindhyan Supergroup). A third event in the region at ~950 Ma was similar to the second event. No continental amalgamation took place along the CITZ during the tectonothermal events at ~1500 Ma and ~950 Ma; these involved reactivation of old thrusts and basal accretion which were the effect of far-field stresses emanating from the orogenic events at the eastern margin of the Bastar Craton and western margin of the Aravalli Craton.

KEYWORDS:

• Basement involved deformation
• rheology of lithosphere
• superposed folding
• deep crustal reflectors
• crustal low-velocity zones
• CITZ

Research highlights

• Paleoproterozoic thick-skinned tectonics identified in the Satpura Orogen, India.

• A crescent-shaped fold inference pattern indicates nappe geometry of the basement rocks.

• Presence of a mantle wedge and double Moho helped to location the collisional boundary.

• Low-strength upper mantle and strong crust developed the thick-skinned tectonics.

Acknowledgments

The author acknowledges the help received from the Post-graduate students and research scholars (particularly A. Acharya, A.K. Mohanty, P.K. Nayak, J.K. Samal, S. Nayak, S.R. Mohapatra, M.P. Mohapatra, A.K. Sahu, A. K. Prasad and M. K. Sahu) associated with the mapping of the Sausar belt for data collection and thought provoking discussions. Suggestions from the first reviewer and Professor R. J. Stern resulted in augmenting more data and the tectonic model. The critical comments from the second reviewer provided impetus for sharpening the logic presented here.

Disclosure statement

The author declares to have no known competing financial interests that could have appeared to influence the work reported in this paper.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00206814.2023.2172620