Redefining the tectonostratigraphic and structural architecture of the Almora klippe and the Ramgarh–Munsiari thrust sheet in NW India

Abstract

We integrate U–Pb zircon geochronology and εNd(0) values with field mapping to determine which tectonostratigraphic units are represented to the north, south and within the Almora klippe in Kumaun, NW India. Rock in the Almora klippe and north of the Main Central thrust (MCT) have Neoproterozoic (c. 900 Ma) detrital zircon ages, coupled with similar εNd(0) (−7.6 to −11.8) values, suggesting that these two units are the same tectonostratigraphic unit, and that the Almora klippe is the southern continuation of the MCT or another thrust in the Greater Himalayan thrust system. However, north of the Almora klippe, detrital zircon age populations establish the presence of Palaeoproterozoic rock instead of the previous interpretation of Neoproterozoic rocks. These Palaeoproterozoic Lesser Himalayan (LH) rocks are carried by the Ramgarh–Munsiari thrust (RMT) dipping south and folded underneath the klippe. South of the klippe, the RMT carries both the less metamorphosed Palaeoproterozoic and Neoproterozoic LH rocks, in disagreement with the idea that only Neoproterozoic–Cambrian LH rocks are present south of Almora klippe. These results suggest that previous cross-sections in Kumaun are incorrect and must be re-evaluated.Supplementary material:U–Pb zircon geochronological data table is available at http://www.geolsoc.org.uk/SUP18777.

Neogene marine isotopic evolution and the erosion of Lesser Himalayan strata: Implications for Cenozoic tectonic history

“…In this region of India, the iLH contains strata of both the lower Lesser Himalaya succession and the lowermost part of the upper Lesser Himalayan succession (McKenzie et al, 2011). Klippen of GH rock occurs structurally above both iLH and oLH rocks (Célérier et al 2009a(Célérier et al , 2009bWebb et al, 2011b;Mandal et al, 2014).…”

Zircon U‐Pb ages and Hf isotopes of the Askot klippe, Kumaun, northwest India: Implications for Paleoproterozoic tectonics, basin evolution and associated metallogeny of the northern Indian cratonic margin

“…Age constraints regionally and from laterally correlated rocks include an interbedded basalt (1800 ± 13 Ma), numerous orthogneisses (1.80–1.85 Ga), and detrital zircon (1.88–1.96 Ga) [ Miller et al ., ; Célérier et al ., ; Kohn et al ., ; Long et al ., ; Webb et al ., ]. The greenschist‐facies Damtha Group unconformably overlies the Berinag Formation [ Célérier et al ., ] and consists of siliciclastic units of the Chakrata (≤1.8 Ga) and Rautgara (≤1.6 Ga) Formations [ McKenzie et al ., ; Mandal et al ., ]. The greenschist‐facies Tejam Group conformably overlies the Damtha Group and spans the lower to upper LH chronologic boundary.…”

“…The largest klippe in the region—the Almora klippe—is commonly interpreted as the southern extension of Paleoproterozoic Munsiari Formation equivalent rocks [ Valdiya , ; Srivastava and Mitra , ; Célérier et al ., ; Rawat and Sharma , ; Patel et al ., ]. However, the klippe instead contains widespread Neoproterozoic (circa 900 Ma) metasedimentary and Ordovician intrusive rocks and must instead be composed of Greater Himalayan rocks, carried southward by the Main Central thrust (regionally called the Vaikrita thrust) [ Mandal et al ., ]. This previous work on the Almora klippe raises the question of whether any of the other klippen share affinities with Munsiari Formation rocks or are instead all Greater Himalayan rocks.…”

Structural model of the Balkassar area, Potwar Plateau, Pakistan

“…1 and 2) since about 55 Ma (Gansser 1979(Gansser , 1980Molnar and Tapponnier 1981;Valdiya 1984Valdiya , 1997Baker et al 1988;Burbank and Raynolds 1988;Molnar 1990;Davis and Lillie 1994;Kazmi and Jan 1997;Mohadjer et al 2010;Hasany and Saleem 2012;Jain 2014). Extensive work is conducted on this orogeny in India, Nepal and nearby areas (e.g., Le Fort 1975;Hodges et al 1992;Carosi et al 1998;Upreti 1999;Hodges 2000;DeCelles et al 2002;Lee et al 2004;Yin 2006;Carosi et al 2007;Wang et al 2012 Robinson andPearson 2013;Khanal and Robinson 2013;Mandal et al 2014;Khanal et al 2014). Further in Pakistan, the orogeny has remained the subject of many studies (e.g., Davis and Engelder 1985;Baig and Lawrence 1987;Butler et al 1987;Baker et al 1988;Jaumé and Lillie 1988;Greland et al 2002).…”