Geological Mapping with Emphasis on Sedimentary Structures Around Rukumkot and Naigad Area in Rukum (East), Western Nepal

Abstract

The Lesser Himalaya constitutes a critical tectono-sedimentary domain within the Himalayan orogenic system, preserving a prolonged record of sedimentation, basin evolution, and deformation related to India–Eurasia convergence. Detailed analyses of lithostratigraphy and sedimentary structures within this region are essential for reconstructing depositional environments and understanding the coupling between sedimentation and tectonism through geological time.Despite extensive regional stratigraphic and structural investigations in western Nepal, formation-scale documentation of sedimentary structures and their paleoenvironmental significance remains limited in the Rukumkot–Naigad area.This study aims to address this gap by undertaking detailed geological mapping and systematic sedimentological analysis to characterize lithostratigraphic units, sedimentary structures, and depositional environments within the Lesser Himalayan succession of the Rukumkot–Naigad region, western Nepal.Geological mapping at a scale of 1:25,000 was integrated with comprehensive field based lithological descriptions and analysis of primary sedimentary structures across seven Lesser Himalayan formations and one Higher Himalayan unit. Observed structures including stromatolites, ripple marks, mud cracks, flute casts, intraclast breccia, and cross-bedding indicate depositional environments ranging from deep to shallow marine and marginal fluvial settings, consistent with foreland basin sedimentation subsequently modified by progressive Himalayan thrusting and folding. Overall, this study refines the stratigraphic framework of the Rukumkot–Naigad area and advances understanding of Lesser Himalayan basin evolution.