Role of initial basin width in partitioning total shortening in the Lesser Himalayan fold-thrust belt: Insights from regional balanced cross-sections

• Lesser Himalayan sequence (LHS) records highest lateral variation in shortening in the Himalayan FTB.
• A direct correlation exists between initial width of LHS and total shortening in the FTB.
• Initial width of LHS controlled lateral variation in shortening in the FTB.
• Initial width of LHS controlled lateral variation in structural geometry of the FTB.

Published, regional, balanced cross-sections constructed across various transects along the Himalayan fold-thrust belt (FTB) suggest significant lateral variations in the magnitude and partitioning of total minimum shortening among various lithotectonic units. The variation in shortening is greatest in the Lesser Himalayan sequence (LHS). Western Nepal Himalaya records the highest shortening. Shortening variation shows non-uniform spatial distribution along the length of the FTB, with regions of lower shortening estimates lying in between regions of higher shortening estimates.We measured the initial and final lengths of the Lesser Himalayan sequence (LHS) from existing published balanced cross-sections. There is a direct correlation between the initial width of the LHS and the total minimum shortening distribution accommodated in all the lithotectonic units of the FTB. This indicates that the initial width of the LHS controlled the lateral variation in the total minimum shortening, and provides a new interpretation for minimum shortening variation in the FTB. The initial width of the LHS also controlled the lateral variation in structural architecture of the LHS by affecting the geometry and total number of LHS imbricates and horses along the FTB. The variation in structural geometry of the LHS along the Himalayan FTB resulted in non-uniform distribution of lateral variation in initial and current LHS outcrop widths.