Magnetostratigraphic and rock magnetic study of the Neogene upper Yaha section, Kuche Depression (Tarim Basin): Implications to formation of the Xiyu conglomerate formation, NW China

Abstract

[1] Magnetostratigraphic study of 251 horizons through the younger Yaha succession in the Kuche Depression of the Tarim Basin, NW China, lying beneath a massive regionally extensive (Xiyu) conglomerate formation identifies nine reversed and eight normal polarity chrons correlating with the Geomagnetic Polarity Time Scale to show that deposition spanned the interval $5.3 to $1.7 Ma. Sedimentation rates fell episodically from $49 to $24 cm/kyr as neotectonic deformation in the southern Tian Shan thrust belt became focused on two major anticlines with the northern (Qiulitage) anticline being initiated at $5.5 Ma and developing a northern hinged limb that embraces the basal part of the studied section. Rock magnetic parameters show multiple signatures of lithologic change, deformation, burial diagenesis, and climate with the latter identifying an early Pliocene warm/humid interval followed by cooling and desertification after $2.6 Ma. Diachronous commencement of Xiyu conglomerate deposition ranged from mid-Miocene in the north of the southern flank of the Tian Shan to Pleistocene in the south advancing as a clastic wedge derived from the uplifted range front to the north. This southward progradation was not climatically controlled although climatic effects may have modulated deposition during the Pleistocene. Uplift in the Tian Shan at $16-15 Ma correlates with rapid increase in sedimentation rate and episodic increases occurred subsequently until the initiation of the Qiulitage anticline. Reduced rates since $5.0 Ma contrast with increases more commonly recorded in foreland basins and have been controlled by accelerated growth of this regional structure counterbalancing uplift of the mountain front to the north.

Neogene Paleomagnetic Study of the Western Baicheng Depression: Implications for the Intensified Deformation of Tian Shan Since the Latest Miocene

“…Based on the magnetostratigraphy of syntectonic deposits on the northern limb of the northern Kalayuergun anticline, we suggest that the anticline growth initiated at ~5.3 Ma. The interpreted latest Miocene intracontinental deformation in the western Baicheng Depression is roughly synchronous with tectonic events observed around the Tian Shan Range and the Tarim Basin, such as the tectonic uplift of the Kunlun Mountains (Sun et al, ; Zheng et al, ), the northward propagation of the northeast Pamir thrust system (Thompson et al, ), the eventual collision between the Pamir Plateau and the SW Tian Shan (Fu et al, ; Sun et al, , ), and the deformation in other parts of Tian Shan forelands (Huang et al, , ; Hubert‐Ferrari et al, ; Lu et al, , ; Saint‐Carlier et al, ; Sun et al, ; Sun & Zhang, ; Wang et al, ; Zhang et al, ). The above mentioned geological facts suggest that the deformation initiating in the latest Miocene was a regionally distributed tectonic event.…”

A New Sediment Accumulation Model of Cenozoic Depositional Ages From the Qaidam Basin, Tibetan Plateau

“…Sun et al, ). However, by carrying out magnetostratigraphic studies along multiple outcrops in Tarim basin and Junggar basin, recent studies reveal that the basal age of the Xiyu conglomerate could range from ~15 to 0.7 Ma (Charreau, Chen, et al, ; Charreau et al, ; Charreau, Gumiaux, et al, ; Heermance et al, ; Huang et al, ), which indicates the diachronous nature of the Xiyu conglomerate deposition at both a local and regional scale. Therefore, our interpretation that the Qaidam basin filled diachronously during the Cenozoic appears to be reasonable.…”

Magnetostratigraphy of the Kelasu section in the Baicheng depression, Southern Tian Shan, northwestern China

“…Although several magnetostratigraphic results have been published in recent years in the nearby region (e.g., Teng et al, 1997;Charreau et al, , 2009Huang et al, 2006Huang et al, , 2010Zheng and Meng, 2006;Jing et al, 2011;Zhang et al, 2014), no agreement has been acquired. Teng et al (1997) carried out a magnetostratigraphic study in the Kuqa section, which is about 80 km to the east of our studied section.…”

“…Magnetostratigraphy of the Cenozoic sediments in the foreland basins of Tian Shan has been widely studied during the last two decades (e.g., Teng et al, 1997;Sun et al, 2004Sun et al, , 2007Charreau et al, 2005Charreau et al, , 2009Huang et al, 2006Huang et al, , 2010Zheng and Meng, 2006;Ji et al, 2008;Jing et al, 2011;Li et al, 2011;Zhang et al, 2014). However, due to the scarcity of paleontological fossils and volcanic rocks appropriate for accurately dating, there have been many debates about the magnetostratigraphic time scales in the foreland basins of the Tian Shan Range.…”

“…Additionally, the previous magnetostratigraphic investigations in the foreland basins of the Tian Shan mainly focused on the Neogene deposits (e.g., Charreau et al, 2005Charreau et al, , 2009Huang et al, 2006Huang et al, , 2010Jing et al, 2011;Zhang et al, 2014) (see the detailed locations in Fig. 2a).…”