Paleomagnetic data support Early Permian age for the Abor Volcanics in the lower Siang Valley, NE India: Significance for Gondwana-related break-up models

Abstract

a b s t r a c tConfusion exists as to the age of the Abor Volcanics of NE India. Some consider the unit to have been emplaced in the Early Permian, others the Early Eocene, a difference of $230 million years. The divergence in opinion is significant because fundamentally different models explaining the geotectonic evolution of India depend on the age designation of the unit. Paleomagnetic data reported here from several exposures in the type locality of the formation in the lower Siang Valley indicate that steep dipping primary magnetizations (mean = 72.7 ± 6.2°, equating to a paleo-latitude of 58.1°) are recorded in the formation. These are only consistent with the unit being of Permian age, possibly Artinskian based on a magnetostratigraphic argument. Plate tectonic models for this time consistently show the NE corner of the sub-continent >50°S; in the Early Eocene it was just north of the equator, which would have resulted in the unit recording shallow directions. The mean declination is counter-clockwise rotated by $94°, around half of which can be related to the motion of the Indian block; the remainder is likely due local Himalayan-age thrusting in the Eastern Syntaxis. Several workers have correlated the Abor Volcanics with broadly coeval mafic volcanic suites in Oman, NE Pakistan-NW India and southern Tibet-Nepal, which developed in response to the Cimmerian block peeling-off eastern Gondwana in the Early-Middle Permian, but we believe there are problems with this model. Instead, we suggest that the Abor basalts relate to India-Antarctica/India-Australia extension that was happening at about the same time. Such an explanation best accommodates the relevant stratigraphical and structural data (present-day position within the Himalayan thrust stack), as well as the plate tectonic model for Permian eastern Gondwana.

Petrographic features as an effective indicator for the variation in strength of granites

“…The Permian aged rift related magmatism in the Himalayan domains of Pakistan, India and China is widely considered as large igneous province (Chaudry and Ashraf, 1980;Bhat et al, 1981;Vannay and Spring, 1993;Spencer et al, 1995;Garzanti et al, 1999;Ernst and Buchan, 2001;Zhu et al, 2010;Shellnutt et al, 2011Shellnutt et al, , 2012Shellnutt et al, , 2014Ali et al, 2012;Zhai et al, 2013;Wang et al, 2014). The Panjal Traps (e.g.…”

“…The Panjal Traps (e.g. Papritz and Rey, 1989;Chauvet et al, 2008;Shellnutt et al, 2014), Abor volcanics (Bhat, 1984;Ali et al, 2012) and Qiangtang dykes (Zhu et al, 2013;Xu et al, 2015) are the few examples of early to middle Permian basaltic rocks in the Himalayas which are the result of plate separation and initiation of new oceanic basin i.e. Neotethys (Sengor, 1987;Bhat et al, 1981;Shellnutt et al, 2014).…”

Late Paleozoic Woniusi basaltic province from Sibumasu terrane: Implications for the breakup of eastern Gondwana’s northern margin

“…1), including the Sibumasu and southern Qiangtang terranes, had drifted from the northern Gondwana margin during the Early Permian period (e.g., Zhong, 1998;Metcalfe and Aung, 2014). Contemporaneous basaltic magmatism has been widely reported in the northern Indian Gondwana margin and its surrounding areas, as represented by the Panjal Traps, Abor, Bhote Kosi, Selong, and southern Qiangtang (Bhat, 1984;Garzanti et al, 1999;Chauvet et al, 2008;Shellnutt et al, 2011Shellnutt et al, , 2014Ali et al, 2012;Zhai et al, 2013;Wang et al, 2014). They are all displayed in large distributions and were emplaced in a relatively short time interval between the latest Carboniferous and Early Permian (ca.…”

Faunal similarity in Madagascan and South Indian Late Cretaceous vertebrate faunas

“…Roever, 1942, andDavydov et al, 2013, in Timor; Reeckmann and Mebberson, 1984, in Canning Basin;Ali et al, 2012 in Himalayan India).…”