Kinematic model for the Main Central thrust in Nepal

Abstract

We present a kinematic model for the Himalayan thrust belt that satisfies structural and metamorphic data and explains recently reported late Miocene-Pliocene geochronologic and thermochronologic ages from rocks in the Main Central thrust zone in central Nepal. At its current exposure level, the Main Central thrust juxtaposes a hanging-wall flat in Greater Himalayan rocks with a footwall flat in Lesser Himalayan rocks of the Ramgarh thrust sheet, which is the roof thrust of a large Lesser Himalayan duplex. Sequential emplacement of the Main Central (early Miocene) and Ramgarh (middle Miocene) thrust sheets was followed by insertion of thrust sheets within the Lesser Himalayan duplex and folding of the Main Central and Ramgarh thrusts during late Miocene-Pliocene time. Thorium-lead (Th-Pb) ages of monazite inclusions in garnets from central Nepal record the timing of coeval, progressive metamorphism of Lesser Himalayan rocks in the footwall of the Main Central thrust. Although this model does not rule out minor, late-stage reactivation of the Main Central thrust, major late Miocene reactivation is not required.

Mountain Building: From Earthquakes to Geologic Deformation

“…Figure 20 presents the kinematic model proposed for far western Nepal . This model also applies, with some minor variations, to central Nepal (Bollinger et al, 2004a;Robinson et al, 2003).…”

“…The basal 'Mahabharat' thrust can be interpreted as the southern extension of the MCT, although the possibility that it is a distinct thrust fault rooting below the MCT cannot be excluded (e.g., Upreti, 1999). North of the klippe, the foliation in the Lesser Himalayan schist describes a large antiformal structure, called the PokharaGorkha anticlinorium (Pêcher, 1989 shown in Figure 8, has been interpreted as a hinterland dipping duplex structure (Brunel, 1986), and it has been recognized on most sections across the Nepal Himalayas Robinson et al, 2003;Schelling and Arita, 1991;Schelling, 1992) and in Kumaon, India (Celerier et al, 2009;Srivastava and Mitra, 1994). The High Himalayan units consist of amphibolite-grade schist intruded by large leucogranitic plutons.…”

Tectonic studies and crustal shortening across Easternmost Arunachal Himalaya

“…They are exposed as thrusted units in southern part of the area above the eroded Siwaliks. In the northern part, they are exposed as tectonic window as a result of duplexing (Robinson et al, 2003) near Hunli village. Roof of this duplex has been eroded and the underlying greenschist metamorphics of Sewak Group are exposed in the area as a window at Hunli village underneath medium-grade epidote-amphibolite metamorphics of Lalpani Group where they are exposed around Ameli village, both beneath the kyanite-sillimanite metamorphics of Mayodia Group.…”

Cenozoic sedimentary records and geochronological constraints of differential uplift of the Qinghai-Tibet Plateau

“…During the uplifts, the exhumation occurred. A number of data on Ar/Ar age and the monazite Th-U age suggested that in the period 11-9 Ma [65][66][67][68][69][70] the Central Himalayan Fault, the major boundary fault, and high Himalayan metamorphite system were under exhumation. Since 5Ma, the rapid uplift and exhumation events mainly occurred in the Himalayan orogenic belts.…”