Late Cenozoic tectonic evolution of the northwestern Tien Shan: New age estimates for the initiation of mountain building

Abstract

The Tien Shan are the quintessential intracontinental range, situated more than 1000 km north of the suture between India and Asia. Their initiation and growth in the Cenozoic, however, remain poorly understood. In this study we present stratigraphic, detrital fission-track, and magnetostratigraphic results that provide a basis for reconstructing the Cenozoic tectonic evolution of the Kyrgyz Range and adjacent Chu basin in the northwestern Tien Shan. Detrital fission-track thermochronology indicates that the northwestern Tien Shan was tectonically quiescent for much of the Cenozoic. Prior to uplift and exhumation in the late Miocene, the Kyrgyz Range was buried by sediments shed from highlands to the south and/or east. Paired bedrock fission-track and [U-Th]/He ages from a sampling transect of 2.4 km relief demonstrate that rapid exhumation commenced at ca. 11 Ma. Initial thrusting in the hinterland was followed by evaporite accumulation (ϳ0.4 km/m.y.), which coincided with erosion of the pre-11 Ma strata that mantled the Kyrgyz Range. Between 10 and 3 Ma, bedrockexhumation rates decreased to Ͻ0.3 km/ m.y., while sedimentation rates decelerated initially to ϳ0.25 km/m.y. before accelerating to ϳ0.4 km/m.y. at 4-5 Ma. Detrital fission-track results indicate that by 4.5 Ma,

Mesozoic–Tertiary exhumation history of the Altai Mountains, northern Xinjiang, China: New constraints from apatite fission track data

“…In the Tian Shan Mountains to the southwest (Fig. 1) tectonism and surface uplift started around 25 -20 Ma and is considered linked to a change from extrusion-dominated to crustal-thickening-dominated strain accommodation in the Himalaya (Bullen et al, 2001;Sobel and Dumitru, 1997). An Oligocene unconformity in basins along the eastern margin of the Altai such as the Dzereg and Dariv basins marks the onset of deformation in the Mongolian Altai (Howard et al, 2003;Cunningham et al, 2001).…”

Paleo-erosion rates in Central Asia since 9Ma: A transient increase at the onset of Quaternary glaciations?

“…The Tianshan is a 2500-km-long tectonically active mountain range that dominates Central Asia with an average altitude of 2500 m and summits reaching up to 7000 m. While its geology consists of mainly island arc rocks linked to a long-lived Paleozoic history of subduction/collision (Burtman, 1975;Charvet et al, 2007;Gao et al, 1998;Lin et al, 2008;Wang et al, 2008;Windley et al, 1990), the present high topography attests to a more recent and intense deformation. This later owes its origin to the Cenozoic reactivation of the range during the Oligocene to early Miocene (>16 Ma) (Avouac et al, 1993;Bullen et al, 2003;Bullen et al, 2001;Charreau et al, 2009a;Charreau et al, 2005;Charreau et al, 2006;Dumitru et al, 2001;Sobel et al, 2006;Sobel and Dumitru, 1997;Windley et al, 1990;Yin et al, 1998), under the influence of the ongoing India-Asia collision. The Tianshan range indeed plays a major role in the IndiaAsia collision since it presently accomodates up to 40% of the total convergence between those two continents (Abdrakhmatov et al, 1996;Reigber et al, 2001).…”

Permian plume beneath Tarim from receiver functions

“…Previous mountain-building episodes in the region of the Tien Shan took place in the Paleozoic (e.g., Windley et al, 1990), but for about 100 Myr prior to the onset of the present-day mountain building the lithosphere of the Tien-Shan was quiet. Tectonic activity resumed at about 25-20 Ma in the southern Tien Shan ( Sobel and Dumitru, 1997) and at 11 Ma 65 in the north (Bullen et al, 2001). The lithosphere of Tarim underthrusts the relatively weak lithosphere of the Tien Shan at a rate of about 20 mm/yr (Reigber et al, 2001).…”