Paleomagnetism indicates no Neogene vertical axis rotations of the northeastern Tibetan Plateau

Abstract

[1] Paleomagnetic data were obtained from 108 paleomagnetic sites collected in Cretaceous to Tertiary red beds from seven localities distributed in three general regions adjacent to the Altyn Tagh fault at the northern edge of the Tibetan Plateau. In the Hexi corridor, 12 sites in Oligocene strata at Yaoquanzi (39.97°N; 97.68°E) yield a mean paleomagnetic direction (I = 33.0°; D = 8.6°, a 95 = 6.0°) with concordant declination, and 36 sites in Early Cretaceous mudstones of the Longshou Shan (39.09°N; 100.50°E) provide a concordant paleomagnetic direction (I = 53.4°; D = 6.8°, a 95 = 3.8°). Across the Nan Shan fold-thrust belt, Miocene paleomagnetic directions from 39 sites distributed among four localities have a concordant mean declination (I = 40.6°; D = 7.2°, a 95 = 5.8°). In the Altyn Tagh range, 21 sites in Oligocene strata at Xorkoli (38.93°N; 91.43°E) yield a paleomagnetic direction with concordant declination (I = 49.7°; D = 5.0°, a 95 = 5.4°). These results combined with existing regional paleomagnetic data indicate that (1) the Hexi corridor along with the North China block has not undergone tectonic vertical axis rotation since at least Early Cretaceous time and is separated from the XiningLanzhou basin and eastern Tibet by an important post-Early Cretaceous tectonic boundary; (2) the Nan Shan fold-thrust belt and the Qaidam Basin have not experienced wholesale vertical axis rotation during Neogene time; and (3) absence of vertical axis rotations in areas adjacent to the Altyn Tagh fault indicates that sinistral shear strain between the Tarim Basin and the northern Tibetan Plateau is concentrated on the fault. These results are consistent with Asian tectonic models that combine distributed lithospheric deformation and thickening with narrow and weak shear zones.

Magnetostratigraphy of the Suerkuli Basin indicates Pliocene (3.2Ma) activity of the middle Altyn Tagh Fault, northern Tibetan Plateau

“…4), which is consistent with a significant hematite contribution. These results are in agreement with rock magnetic characteristics from previously reported Neogene red beds from the Suerkoli (Xorkoli) basin (Dupont-Nivet and Butler, 2003).…”

“…A set of Cenozoic basins formed adjacent to the ATF recording the precise history of the fault activity (e.g. Dupont-Nivet and Butler, 2003;Sun et al, 2005a,b;Yue et al, 2003). However, the depositional age in most of these basins is still poorly constrained although they are potentially suitable for magnetostratigraphic dating.…”

The Cenozoic growth of the Qilian Shan in the northeastern Tibetan Plateau: A sedimentary archive from the Jiuxi Basin

“…This counterclockwise rotation is also documented by paleomagnetic data from other sections in the Jiuxi Basin [ Yan et al ., ]. Two potential mechanisms have been proposed to explain the appearance of the basin's counterclockwise rotation: (1) the eastward extrusion of materials along the Qilian Shan, which may cause counterclockwise rotation in the foreland [ Yan et al ., ], and (2) oroclinal bending of the Altyn Tagh Fault by shear stress [ Dupont‐Nivet et al ., ]. In the first model, the large‐magnitude left‐lateral strike‐slip faulting on the Altyn Tagh Fault plays a central role in the eastward extrusion of the northeastern Tibetan Plateau [ Meyer et al ., ; Tapponnier et al ., ; Yan et al ., ].…”

“…In the first model, the large‐magnitude left‐lateral strike‐slip faulting on the Altyn Tagh Fault plays a central role in the eastward extrusion of the northeastern Tibetan Plateau [ Meyer et al ., ; Tapponnier et al ., ; Yan et al ., ]. In the second model, the left‐lateral movement of the Altyn Tagh Fault bent the strata in the eastern part of the Altyn Tagh Fault toward the south [ Dupont‐Nivet et al ., ]. Regardless of which process resulted in the rotation direction changes in the Jiuxi Basin, the counterclockwise rotation in the basin was potentially caused by left‐lateral strike slip along the eastern Altyn Tagh Fault after ~13.5 Ma.…”

Initial rupture and displacement on the Altyn Tagh fault, northern Tibetan Plateau: Constraints based on residual Mesozoic to Cenozoic strata in the western Qaidam Basin

“…Understanding the Cenozoic kinematic patterns of the Altyn Tagh fault holds important implications for unraveling the evolution of northern Tibet, deciphering the growth history of the entire Tibetan Plateau, and contributing to oil and gas exploration in the surrounding region (Yue and Liou, 1999;Yin and Harri-son, 2000;Tapponnier et al, 2001;Yin et al, 2002;Wang et al, 2014). Recent studies have revealed much about the basic geology of the Altyn Tagh Range and the surrounding region (Wang, 1997;Cowgill et al, 2000Cowgill et al, , 2003Yue et al, 2001Yue et al, , 2004aYin et al, 2002;Chen et al, 2003;Dupont-Nivet et al, 2003Ritts et al, 2004;Wu et al, 2012aWu et al, , 2012bCheng et al, 2014;Lu et al, 2014;Zhang et al, 2014); however, the immense size and extent of the Altyn Tagh Range make it difficult to locate ideal piercing points with which to estimate the initial timing of left-slip movement and total displacement along the Altyn Tagh fault. As a result, both the timing and amount of slip along the fault are vigorously debated (e.g., Yin et al, 2002;Cowgill et al, 2003;Gehrels et al, 2003aGehrels et al, , 2003bRitts et al, 2004;Wu et al, 2012aWu et al, , 2012b.…”