Regardless of being deemed a “excellent” arc, the form of the Himalaya highlands is interrupted by an embayment that stretches throughout almost 2° of longitude in western Nepal. This deviation from an ideal form, plus just a few diverging landforms and fault anomalies, casts a shadow on the geologic processes at play within the area. This anomaly additionally gives a possibility to research how the Himalayan megathrust fault impacts the lively progress of the mountain vary. Moreover, understanding the character of the megathrust within the western Himalayas is essential to evaluating seismic hazards within the area.
In a brand new examine, Fan et al. used thermokinematic modeling to outline the geometry and motion of the megathrust in western Nepal. Specifically, the researchers in contrast the thermochronological ages of crystals equivalent to zircon, apatite, and muscovite with age estimations from thermokinematic fashions that invoke large-scale crustal actions alongside the megathrust.
Analysis revealed the 3D geometry and motion of the megathrust. The crew discovered that the cooling ages in western Nepal are finest reproduced by a megathrust mannequin with two related ramps and crustal accretion occurring at mid-lower crustal depths alongside the northern ramp. In addition they discovered that crustal accretion alongside the mid-lower ramp might need been controlling the frontal fringe of the Tibetan plateau out and in of the embayment. As well as, variation within the propagation of the mid-lower ramp could have occurred no less than 10 million years in the past and will have precipitated the formation of the embayment in western Nepal.
The crew stated their work highlights the significance of crustal accretion at completely different depths when growing a mountain system and helps to find out the placement of a plateau edge. In addition they word that the megathrust evolution and related deep structural processes could have managed the evolution of the regional drainage system. (Tectonics, https://doi.org/10.1029/2021TC007071, 2022)
—Sarah Derouin, Science Author