Evidence from paleosols for low to moderate elevation of the India-Asia suture zone during mid-Cenozoic time

Abstract

The post-collisional uplift history of the India-Asia suture zone in southern Tibet is important for understanding the geodynamic conditions of the India-Asia collision and how it may have modified regional and global climate. Here we use stable isotope and major element analyses of paleosols preserved in the Liuqu Conglomerate to reconstruct India-Asia suture zone paleoclimate and paleoelevation. Paleosol carbonate δ13C (Vienna Peedee belemnite) average values of −9.4‰ ± 1.1‰ indicate that Liuqu paleosols were well vegetated by C3 plants, unlike thinly vegetated and arid modern Tibet. Major element weathering indices show that these soils experienced significant collapse and loss of cations due to weathering of similar intensity to that in the wet, low elevations of the Neogene Himalayan foreland. Age estimates for the Liuqu vary, but current evidence points to an early Miocene age. Our evidence requires that the India-Asia suture zone experienced wet, well-vegetated conditions during Liuqu Conglomerate deposition. Geodynamically this implies that the suture zone was at relatively low elevation and was topographically open to monsoon moisture as late as 40 m.y. after the start of the India-Asian collision. This challenges the idea that uplift of the India-Asia suture zone was monotonic and tied directly to crustal thickening.