Slides, soft-sediment deformations, and mass flows from Proterozoic Lakheri Limestone Formation, Vindhyan Supergroup, central India, and their implications towards basin tectonics

摘要

The Neoproterozoic Lakheri Limestone (LL) Member of Vindhyan Supergroup, central India, interpreted as a low-gradient homoclinal ramp, contains a wide range of signatures indicating syn-sedimentary basinal extension and compression. Whereas features like intraformational truncation (slide) surfaces of varying geometry, creep and bedding translation manifest the phases of extension, the compressional events are registered in bed-confined thrusts and outcrop-scale folds. A wide range of outcrop and microscopic deformational features are associated with the sliding events, the expressions of which vary based on their relative position with respect to the slide surface (over- or underlying) and the degree of built-up pore water pressure. The detached sediment mass often evolved in the form of mass flows with rheology varying between cohesive debris flow and low-density turbidity current. In particular, operation of reflected turbiditic flows is suggestive of irregular depositional substrate, induced by curvilinear syn-sedimentary slides in otherwise low-gradient distal shelf platformal setting. The present study intends to relate the observed extensional and compressional features of LL succession with the flexural response of early rifted Vindhyan basement under reversing in-plane stress in its post-rift depositional history. Bipolar NE–SW orientation of the slide planes is well consistent with the proposed rifted configuration of Vindhyan basement. Centimeter- to decimeter-deep slide detachments and equally thick mass-flow beds are indicative of relatively deeper level of necking during the early syn-rift phase of Vindhyan history.