Active out-of-sequence thrust faulting in the central Nepalese Himalaya

Abstract

Recent convergence between India and Eurasia is commonly assumed to be accommodated mainly along a single fault--the Main Himalayan Thrust (MHT)--which reaches the surface in the Siwalik Hills of southern Nepal. Although this model is consistent with geodetic, geomorphic and microseismic data, an alternative model incorporating slip on more northerly surface faults has been proposed to be consistent with these data as well. Here we present in situ cosmogenic 10Be data indicating a fourfold increase in millennial timescale erosion rates occurring over a distance of less than 2 km in central Nepal, delineating for the first time an active thrust fault nearly 100 km north of the surface expression of the MHT. These data challenge the view that rock uplift gradients in central Nepal reflect only passive transport over a ramp in the MHT. Instead, when combined with previously reported 40Ar-39Ar data, our results indicate persistent exhumation above deep-seated, surface-breaking structures at the foot of the high Himalaya. These results suggest that strong dynamic interactions between climate, erosion and tectonics have maintained a locus of active deformation well to the north of the Himalayan deformation front.

Correlations Between Erosions and Relative Uplifts From the Central Inversion Zone of the Xihu Depression, East China Sea Basin

“…Erosion and uplift are two basic geological processes associated with mountain building, and there has been an upsurge of interests in better understanding the complex and dynamic feedbacks between tectonics, climate, and denudation (i.e., Wobus et al 2005). However the exact relationships and interactions between erosion and uplift are often difficult to quantify due to the lack of observable or measurable data.…”

“…Riebe et al (2000) studied the erosion rates in the Sierra Nevada of California using cosmogenic 26 Al and 10 Be, while in the same region, Cecil et al (2006) studied the Cenozoic exhumation from (U -Th) / He thermochronology. Wobus et al (2005) suggested from 10 Be data that a locus of active deformation well to the north of the Himalayan deformation front has been maintained by dynamic interactions between climate, erosion and tectonics.…”

“…However the exact relationships and interactions between erosion and uplift are often difficult to quantify due to the lack of observable or measurable data. Most studies on uplift and erosion are focused on present-day landscapes, such as the Sierra Nevada (Riebe et al 2000;Cecil et al 2006), the Colorado Plateau (Pederson et al 2002) and the Tibetan Plateau (Wobus et al 2005), which can offer easy access and direct measurements. Cosmogenic isotopes such as 26 Al and 10 Be, and low-temperature thermochronology based on apatite and zircon (U -Th) / He ages are two commonly used techniques in estimating erosion and exhumation (Spotila 2005).…”

Feasibility of the Sar Technique on Quartz Sand of Terraces of NW Himalaya: A Case Study from Devprayag

“…Recently, a lot of work has been done regarding the evolution of river terraces and their neo-tectonic and climatic implications (Burbank, 2005;Wobus et al, 2005). Due to lack of suitable organic material and limited upper bound (<50 ka) for 14 C dating technique, OSL dating technique was explored due to ubiquitous dating material (Quartz and Feldspar) and expanded upper age limit up to 200-300 ka.…”

“…The Himalaya is an active south propagating foldthrust-belt as a result of collision between Indian and Asian plates and preserves signatures of past tectonic and climatic events in the form of various geomorphic archives (Bilham et al, 1997;Senthil et al, 2001;Hodges et al, 2004;Pratt et al, 2004;Burbank, 2005;Wobus et al, 2005). Most of the projects in the Indian Himalayas focused on Lake Sequences for palaeo-climate and neotectonic studies (Singhvi et al, 1994;Banerjee et al 1999;Chamyal and Juyal, 2005), which can be dated by 14 C and less attention was paid to fluvial sediments in the Himalayan river Valleys.…”