Integration of Grain-Size Statistics, Sedimentary Structures and Basin Dynamics of the Nagaur Sandstone in the Shri Balaji Area, Nagaur District, Northwestern India

Author(s): Mahendra Dan, Deva Ram Meghwal and Vijay Kumar Matoria

Abstract:

The Neoproterozoic to Early Cambrian Marwar Supergroup of western Rajasthan preserves an exceptional sedimentary archive for deciphering the paleogeographic and geodynamic evolution of the northwestern Indian shield. This study integrates high-resolution grain-size statistics, primary sedimentary structures, and directional paleocurrent data from the Nagaur Sandstone exposed in the Shri Balaji area of Nagaur District, Rajasthan, to reconstruct depositional processes, hydrodynamic conditions, and localized basin dynamics. Utilizing digital image-based petrographic measurements across ten representative sandstone samples (SBL-1 to SBL-10), the grain-size frequency distributions reveal a predominantly fine- to very-fine-grained sandy population with a prominent unimodal modal peak centered around 2.5 Φ. Field observations delineate a diverse structural inventory, including planar and parallel stratification, small-scale cross-bedding, asymmetrical current ripples, flaser-lenticular bedding, and localized desiccation structures. These features indicate persistent tractional transport under predominantly unidirectional currents, interspersed with periodic fluctuations in flow energy and episodic subaerial emergence. Azimuthal measurements from fifteen ripple-bearing horizons (n=141) define a coherent sediment-dispersal vector with a mean resultant paleocurrent direction of 〖295.5〗^∘ (WNW). The synthesized sedimentological, textural, and directional evidence demonstrates that the Nagaur Sandstone in the Shri Balaji sector accumulated within a dynamic, current-influenced shallow-water to intertidal-marginal-marine depositional system governed by steady sediment reworking, fluctuating hydraulic energy, and stable regional paleoslopes.

keywords:
Nagaur Sandstone; Grain-size statistics; Sedimentary structures; Paleocurrent analysis; Depositional environment; Basin dynamics; Marwar Supergroup.

Pages: 51-59     |    9 View     |    2 Download