Geomorphic investigation of fold characteristics and linkage across the Indoburman Range

Abstract:

The Indoburman Range (IBR) fold-and-thrust belt formed due to the highly oblique subduction of the Indian Plate under the Burma microplate. The subduction has produced components of E-W shortening and N-S strike-slip deformation. The N-S oriented anticlinal structures have accommodated E-W shortening. These surface structures do not appear to be impacted by the obliquity of the plate convergence, and the fold characteristics, lateral propagation and linkage reflect the landscape evolution under the subduction regime. In this study, we aim to investigate morphological characteristics of the folds, i.e. symmetry and aspect ratio, to define the fold type and examine the variation in fold characteristics across the IBR. We also identify locations of fold linkage and investigate the factors underlying the fold propagation and linkage. We employ ArcGIS, MATLAB, and TopoToolbox to extract elevation data from the USGS 30 x 30 m SRTM digital elevation model, and identify streams, drainage divides and basins. We examine the locations of water and wind gaps, stream patterns, topographic profiles of the fold crests and streams, and variation in fold asymmetry directions to study the development of fold linkages. We observe that the IBR folds are fault-related folds, slightly sinuous and elongate (40 – 400 km crest length). The > 100-km folds do not evolve from a single fold, but they developed through the linkage of multiple folds. The N-S linkage between folds can occur linearly and/or obliquely, and this linkage leads to the greater fold elongation (and sinuosity if the folds obliquely connect). We also observe E-W drainage divides between the N-S folds that in part relate to the NS flexure due to the Shillong Plateau load. Moreover, erosion and sediment deposition likely control the critical distance over which the folds can start to connect forming extended elevated zones above the surroundings. Combining existing field-based structural modeling with new studies from satellite data helps us to better understand the distribution of active tectonics controlling the active fold-and-thrust structures and associated drainage development.