Palaeomagnetic indication for India–Asia collision at 12°N and maximum 810 km Greater India extent in the western suture zone

Abstract

Summary Knowing the pre-collisional extent of the northern Indian Plate margin (‘Greater India’) is vital to understanding the tectonic evolution of the India-Asia collision and the formation of the Himalayan-Tibetan orogen. However, suitable geological units for paleomagnetic investigations along the Himalayan belt are limited, which makes it difficult to reconstruct Greater India during the pre-collisional period in Late Cretaceous to Paleogene. Often the paleomagnetic results from the Zongpu Formation at Gamba in southern Tibet (∼88.5° E) were used for estimates of Greater India, but their validity was recently questioned. As a contribution to closing the data gap, we performed a paleomagnetic study of the Paleocene/Lower Eocene Dibling limestone (DL) in the western Tethyan Himalaya of Zanskar (34.0° N/76.6° E). The results from 27 sites revealed a well grouping (k = 71.7) syntectonic magnetization with best grouping at 52 per cent unfolding. The remagnetization of the DL was acquired shortly after ∼54 Ma, at the latest at ∼49 Ma, and is probably carried by fine-grained magnetite formed during the early orogenic phase. Assuming proportional tilting of the fold limbs, the corresponding paleolatitude of 11.8 ± 2.4 ° N suggests a maximum Greater India extent of 810 ± 420 km and a first continental contact with the southern Eurasian margin at ∼12° N in the western part of the suture zone. The tectonostratigraphic equivalence of the DL with the Zongpu Formation at Gamba and a great similarity in their magnetic properties supports a secondary origin of the Gamba results. Through understanding the mechanism of remagnetization in the DL, an early orogenic remanence acquisition is also indicated for the Zongpu Formation, and thus the Gamba results deserve further credit for Greater India reconstructions. However, we notice a large inconsistency of the available Late Cretaceous and Paleogene paleolatitude data from the Tethyan Himalaya by up to ∼20°, corresponding to differences of up to ∼2000 km in the size of Greater India. These discrepancies require further paleomagnetic work in the Tethyan Himalaya, and in particular we recommend comparative studies at same locations and of same units.

A Smaller Greater India and a Middle‐Early Eocene Collision With Asia

“…In the western TH, a paleomagnetic study of the Paleocene/lower Eocene Dibling limestone in the Zanskar revealed a syntectonic remagnetization (best grouping at 52% unfolding) and suggested the maximum extent of Greater India was 810 ± 333 km (7.3 ± 3.0°) at 76.6°E (Figure 3 and Figure S8d of Supporting Information ) (Dannemann et al., 2022). Greater India with a 2,700 km extension was proposed based on a "Late Cretaceous" age paleomagnetic study of a section at Zhada (Meng et al., 2020); however, Xu et al.…”

“…In the central–eastern TH the paleomagnetic data for the Zongshan Formation and Zongpu Formation from the Gamba area were interpreted to suggest that Greater India was 1,500–1,900 km (Patzelt et al., 1996; Yi et al., 2011). However, recent studies have questioned whether the remanence is of primary or secondary origin (e.g., Dannemann et al., 2022; Huang et al., 2017; Zhao et al., 2021), and/or a composite higher coercivity remanence was considered as a single remanence direction (e.g., Figure S7 of Supporting Information ). Therefore, these results are not considered sufficiently reliable at present.…”

“…Dotted line indicates the present oriented outline of India and black circles indicate the relative positions of Tingri, Gamba, Gyangze, and Zanskar in the present-day orientation of India. (Dannemann et al, 2022). Greater India with a 2,700 km extension was proposed based on a "Late Cretaceous" age paleomagnetic study of a section at Zhada (Meng et al, 2020); however, Xu et al (2022) argued that this result was unreliable because the section studied by Meng et al (2020) was not the same as that for which previous workers had established reliable biostratigraphic age control.…”

Paleomagnetic Constraint on the Age of the Shyok Suture Zone

“…Owing to the dearth of volcanic rocks that are considered the optimum target for paleomagnetism, and the widespread thermal and chemical overprint in the Tethys Himalaya sedimentary rocks (Appel et al., 2012; Crouzet et al., 2003; Dannemann et al., 2022; Huang et al., 2017; Schill et al., 2002; Xu et al., 2022), the location of the northern edge of Greater India is more challenging to constrain than the Eurasian margin. Results from Paleocene limestones of the Tingri and Zongpu Formations were originally interpreted to suggest the Tethys Himalaya was situated 2,000–3,000 km north of cratonic India at the onset of collision (Besse et al., 1984; Patzelt et al., 1996; Tong et al., 2008; Yi et al., 2011), but these successions have since been shown to be remagnetized (Huang et al., 2017; Liebke et al., 2013).…”

Clay minerals and continental-scale remagnetisation: a case study of South American Neoproterozoic carbonates

“…Late diagenetic processes, such as clay-mineral transformations, release ions in the medium (including ferrous ions) that under the appropriate kinetic/thermodynamic conditions might lead to the growth of authigenic ferromagnetic phases (Hirt et al, 1993;Woods et al, 2002;Tohver et al, 2008). Fluid transport through the natural porosity of sedimentary rocks can induce mineral transformation, while hot basinal brines and hydrothermal associated with nearby magmatic activity/orogenies may trigger the dissolution of detrital phases and growth of others (McCabe et al, 1983;Miller & Kent, 1988;McCabe & Elmore, 1989;Jackson, 1990;Stamatakos et al, 1996;D'Agrella-Filho et al, 2000;Davidson et al, 2000;Trindade et al, 2004;Huang et al, 2017;Jiao et al, 2019;Dannemann et al, 2022;Xu et al, 2022). Finally, the maturation of organic matter and biodegradation of hydrocarbon in sedimentary basins might produce acidic solutions and disturb the local thermochemical equilibrium also contributing to the formation of new magnetic phases (Font et al, 2006;Aldana et al, 2011;Emmerton et al, 2013).…”