Prolonged Slip on the South Tibetan Detachment Constrains Tectonic Models for Synorogenic Extension in the Central Himalaya

Abstract

Stretching over 2,000 km along the crest of the Himalaya, the South Tibetan detachment system (STDS) features a series of low-angle, north dipping, extensional faults and shear zones that played a major role in the Cenozoic tectonic evolution of the Himalayan-Tibetan orogenic system (Burchfiel et al., 1992;Hodges, 2000;Kellett et al., 2018). At some fundamental levels, the STDS marks a late Oligocene-middle Miocene decoupling horizon between the high-temperature metamorphic infrastructure of the orogen below and a more weakly metamorphosed to an unmetamorphosed sedimentary superstructure above (Hodges, 2016). Its trace also corresponds to an important strain transition in the orogen. To the south, Oligocene-Recent thrust and fold structures accommodate ∼N-S shortening. To the north, structures of the same age are predominately normal faults that accommodate E-W extension. In order to know whether this spatial correlation is just a coincidence or has a deeper tectonic significance, we must understand better the age of STDS deformation relative to the age of contractional and extensional deformation to the south and north, respectively. New geochronologic and thermochronologic data reported here provide important constraints on the age of the principal, basal structures of the STDS in an area of the Himalaya where the south-to-north strain transition is especially abrupt and well exposed: the Kali Gandaki valley of central Nepal (Figure 1). Regional GeologyThe bedrock geology of the region of Nepal that includes the 8,000-m peaks Manaslu, Annapurna, and Dhaulagiri has been studied at various levels of detail by many researchers since the foundational work of French geologists in the 1970s (Bordet et al., 1971;Le Fort, 1975). One of the most dramatic geologic transects through the Himalaya is provided by the trans-Himalayan Kali Gandaki river, which carves one of the deepest valleys on Earth between the Annapurna and Dhaulagiri massifs. North of these massifs, the river gradient is low as it flows along the ∼NNE-SSW axis of the Cenozoic Thakkhola graben (

A review of the Caledonian Wilson cycle from a North Atlantic perspective

“…Synorogenic (syn-convergent) extensional structures seem to be a common feature in major continental collision zoneswith the Himalayan South Tibetan Detachment System (STDS) as the most prominent example formed within an ongoing collision zone (e.g. Kellett et al 2019;Pye et al 2022). Synorogenic extension similar to the STDS has been suggested to have occurred within the Caledonian retro-wedge preserved within the East Greenland Caledonides (White et al 2002;White and Hodges 2003;Hodges 2016), whereas the majority of ductile extensional structures preserved within the Scandinavian Caledonides is interpreted to be post-orogenic, representing a distinct tectonic phase after cessation of plate tectonic convergence (e.g.…”

A timeline of the Cenozoic tectonic–magmatic–metamorphic evolution and development of ore resources in the Himalayas

“…Geologists have developed some of the more popular models, but the timing of geological activity is not consistent. As mentioned above, the activity time of many geological processes, such as the extrusion metamorphism time of the GHC and LHS (Goscombe et al, 2018; Kohn, 2014), the active time of the STDS (Kellett et al, 2019; Leloup et al, 2010; Pye et al, 2022), the initial time of the NSTR (Bian et al, 2022; Wolff et al, 2023) and the formation time of the NHGD (Chen et al, 2022; Jessup et al, 2019), remains very controversial. In addition, the Himalayas stretch for approximately 2200–2500 km from east to west and increasing evidence indicates that the timing of the geological activity may not be uniform within the various regions along the strike (Webb et al, 2017).…”

Late extension of a passive margin coeval with subduction of the adjacent slab: The Western Alps and Maghrebides files

“…Extensional tectonics was intensely studied during the last decades in the Alpine belts from the Himalaya to the Alps, Pyrenees and Western Mediterranean belts. Extension occurred during various stages of the evolution of these subduction-collision belts, from the rifting (Manatschal and Müntener, 2009;Chenin et al, 2017;Lagabrielle et al, 2019;Motus et al, 2022) to the impending collisional stages (Royden, 1993;Jolivet et al, 2008;Molli, 2008;Van Hinsbergen et al, 2014), and finally the post-collisional stages (Froitzheim et al, 1997;Selverstone, 2005;Sue et al, 2007;Jolivet et al, 2020;Pye et al, 2022). It is well known that during subduction at the active margin, extension may affect the back-arc domain (Fig.…”