Magnetostratigraphy and rock magnetism of the Neogene Kuitun He section (northwest China): implications for Late Cenozoic uplift of the Tianshan mountains

Abstract

In order to better constrain the tectonic evolution of central Asia under the influence of the India-Asia collision, we carried out a magnetostratigraphic study at the Kuitun He section, on the northern flank of the Tianshan range (northwest China). A total of 801 samples were collected from a 1559-m-thick section, which is composed mainly of fluvio-lacustrine sandstone and conglomerate. Stepwise thermal and alternating field demagnetization isolated a linear magnetization component that decays univectorally toward the origin and likely represents a primary magnetization principally carried by magnetite. From this component, 29 magnetic polarity intervals were identified. They correlate between 3.1 and 10.5 Ma with the reference magnetic polarity time scale, indicating a relatively constant sedimentation rate with an average of 0.21±0.01 mm/year. We also performed a suite of rock magnetic experiments designed to track time-transgressive changes in the sedimentary record. From the rock magnetic parameters, together with the constant sedimentation rate, we conclude that the Tianshan mountains were actively uplifting by 10.5 Ma.

A case study of the internal structures of gossans and weathering processes in the Iberian Pyrite Belt using magnetic fabrics and paleomagnetic dating

“…Figs. 8a-8b) that reveals the internal stratification. Such classical "sedimentary fabric" is extensively described in the AMS literature (Tarling and Hrouda 1993;Charreau et al 2005). …”

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).…”

“…To calculate the 10 Be production during the burial accumulation, the crucial parameter A r was determined by using the high-resolution paleomagnetic record of Charreau et al (2005). This magnetostratigraphic study constraints the accumulation rate at the time of deposition between 0.115±0.006 and 0.418±0.021 cm.yr -1 .…”

Late Paleozoic paleogeographic reconstruction of Western Central Asia based upon paleomagnetic data and its geodynamic implications

“…Baiyanggou, SE of Urumqi) occurred during the events. The structures related to the Paleozoic were reactivated by multiple intracontinental tectonic events which resulted in repeated uplift, erosion, folding and thrusting of the Tian Shan Belt over the Junggar basin (Avouac et al, 1993;Charreau et al, 2005).…”

“…In north Tian Shan, the age of folding is mainly Tertiary (Avouac et al, 1993;Charreau et al, 2005), although several Mesozoic tectonic events are recognized (Hendrix et al, 1992).…”