T287 The Cenozoic Evolution of Tibet—How Do We Unify Seemingly Contradictory Evidence?

Wednesday, 7 November 2018
1:30 PM - 5:30 PM
Room 243

A CASE STUDY AND PALEOMAGNETIC TEST OF THE GREATER INDIA VERSUS GREATER INDIAN BASIN HYPOTHESES: STATISTICALLY RIGOROUS TESTS COMPARING PALEOMAGNETIC STUDY MEANS WITH APPARENT WANDER PATHS

Paper number: T287-10
Program: Technical Sessions
Time: 3:45 PM – 4:00 PM

Authors

Abstract

The Greater Indian Basin (GIB) hypothesis infers the presence of an ocean basin that opened between the Tethyan Himalaya (TH) and cratonic India in late Early Cretaceous to Paleocene time to a width that has been estimated as 2675±700km derived by (van Hinsbergen et al., 2012). The GIB is proposed to have started closing after the collision of the Tethyan Himalaya and Eurasia around the beginning of the Eocene (56 Ma) and finally closed by ~25Ma. This hypothesis is predicated on comparisons of relative few paleomagnetic study means from the TH compared with an estimate of cratonic India's apparent polar wander path (APWP) derived from a global APWP (GAPWP). The paleomagnetic comparison employed in developing this hypothesis involves the angular difference of these individual TH poles with means derived from populations of comparable or more reliable poles, with uncertainty estimated by combining the A95's of the study means and APWP means. If this same metric is applied to the data used to compute the GAPWP one finds that >55% of the study means contributing to the GAPWP would themselves be deemed to be significantly displaced relative to the GAPWP means defined based on those very same poles. This is illogical and demonstrates that this traditional approach to paleomagnetic comparisons is flawed. An alternative metric is proposed that combines the K95,GAPWP and A95,SM to assess significance, where K95≈140/sqrt(K), defines the region within which 95% of poles contributing to a population mean will fall. The average GAPWP K=90, so the mean K95,GAPWP≈12.4°, with average combined uncertainty of ~13.7°, significantly limiting the resolution of paleomagetic estimates of relative displacement. Using this metric of comparison and re-appraising the TH paleomagnetic data demonstrates that these data are no more dispersed than the data that underlie the GAPWP with which they are being compared. Thus these data provide no statistically significant support for the GIB hypothesis.

Geological Society of America Abstracts with Programs. Vol. 50, No. 6

doi: 10.1130/abs/2018AM-325076

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