Problem of positioning Paleogene Eurasia: A review. Efforts to resolve the issue. Implications for the India-Asia collision

Abstract

Limitations with the 'stable Eurasia' paleomagnetic database (temporal and geographic coverage) create problems for tracing the Paleogene and Cretaceous position of Earth's largest continental plate. Consequently, modeling its punctuated growth and assessing the associated tectonic processes, including basin formation along the southeastern and eastern margins, is hampered. A solution is presented in the form of a hybrid early Paleogene paleomagnetic pole (72.0°N, 177.9°E, A95 = 7.9°) derived from three sets of newly generated data; 58-55 Ma and 50 ± 15 Ma basaltic lavas respectively from the Faroe Islands and Kyrgyzstan, and ∼52 Ma sedimentary rocks from southern England. The India-Asia collision model is reviewed in light of the new stable Eurasia pole, seismic tomography data from the mantle below the Indian Ocean-Central Asia region, and recently published, largely field-based, data from the Yarlung-Tsangpo Suture Zone, Tibet. We suggest firstly that between 65-55 Ma India collided with an equatorially located intra-oceanic arc. Secondly, India continued to move north, although at a slower rate, eventually colliding with Eurasia ∼30 Ma. Thirdly, as a result of the collision, maximum shortening in Tibet was probably around 700 km. The principal benefit of a late Paleogene India-Asia collision concerns the reduced time between causal-event and orogenic response in East-SE Asia (the early-contact model, has a delay of >20 m.y., for example initiation of the Red River Fault). The late-collision scenario overcomes this problem, the response time being more similar to the young-active orogens operating today (e.g., Central Japan, Taiwan, New Guinea and Timor).