RESEARCH Towards a clarification of the provenance of Cenozoic sediments in the northern Qaidam Basin Haijian Lu1,*, Jiacan Ye1,2, Licheng Guo3,4, Jiawei Pan1, Shangfa Xiong3,4, and Haibing Li1 1KEY LABORATORY OF DEEP-EARTH DYNAMICS OF MINISTRY OF NATURAL RESOURCES, INSTITUTE OF GEOLOGY, CHINESE ACADEMY OF GEOLOGICAL SCIENCES, BEIJING 100037, CHINA 2SCHOOL OF EARTH SCIENCE AND RESOURCES, CHINA UNIVERSITY OF GEOSCIENCES, BEIJING 100083, CHINA 3KEY LABORATORY OF CENOZOIC GEOLOGY AND ENVIRONMENT, INSTITUTE OF GEOLOGY AND GEOPHYSICS, CHINESE ACADEMY OF SCIENCES, BEIJING 100029, CHINA 4UNIVERSITY OF CHINESE ACADEMY OF SCIENCES, BEIJING 10049, CHINA ABSTRACT Determining the provenance of sedimentary basin fill in the northern Qaidam Basin is a key step toward understanding the sedimen- tary system dynamics and mountain-building processes of the surrounding orogenic belts in Tibet. The exceptionally thick (average of 6–8 km) Cenozoic fluvio-lacustrine deposits in the northern Qaidam Basin were once thought to have been eroded from the nearby north- ern Qaidam Basin margin and the southern Qilian Shan and to reflect the prolonged thrust-related exhumation of these orogenic belts. However, several recent studies, based mainly on paleocurrent and detrital zircon U-Pb age data, suggested that they were derived from the distant East Kunlun Shan to the south, or the Qimen Tagh to the southwest (at least 200 and 350 km from the northern Qaidam Basin, respectively). That model assumed that the East Kunlun Shan and Qimen Tagh formed significant topographic barriers during the earli- est sedimentation of Cenozoic strata (e.g., the Lulehe Formation) in the northern Qaidam Basin. Therefore, the tectonic significance of the provenance of the Lulehe Formation remains a fundamental problem in understanding the postcollisional uplift history of the northern Tibetan Plateau. To address this issue, we conducted sedimentological and paleocurrent analyses of the Lulehe Formation and detrital zircon U-Pb dating of Mesozoic strata in the northern Qaidam Basin. The results, in combination with existing paleocurrent and seismic reflection data, collectively indicate that although the source area cannot be specified by matching zircon U-Pb ages in sedimentary rocks with crystalline basement source rocks, other evidence points consistently to a unified proximal northerly source area (the northern Qaidam Basin margin and the southern Qilian Shan). Our results emphasize that noncrystalline basement rocks (e.g., Mesozoic sedimentary rocks) in fold-and-thrust belts should be taken into consideration when seeking potential source areas by correlating zircon U-Pb ages of silici- clastic detritus with related basement rocks. In addition, this study strongly supports the claim that variations in the proportions of age populations should be used with caution when determining source terrane by comparisons of age distributions. LITHOSPHERE; v. 11; no. 2; p. 252–272; GSA Data Repository Item 2019032 | Published online 20 December 2018 https://doi.org/10.1130/L1037.1 INTRODUCTION thick (average of 6–8 km) sequences of Cenozoic siliciclastic sediments (Rieser et al., 2006a), which have been extensively used to reconstruct In Tibet, several ranges with upthrusted basement (Gangdese, Tanggula, depositional systems (Bush et al., 2016; Jian et al., 2013; Meng and Fang, Kunlun, Altyn Tagh, and Qilian Shan) are separated by numerous large and 2008; Rieser et al., 2005; Wang et al., 2006; Zhu et al., 2006; Zhuang et small Tertiary basins trending approximately E-W to NW-SE (Liu, 1988; al., 2011), erosional unroofing patterns (X. Cheng et al., 2016; Rieser et Pan et al., 2004; Tapponnier et al., 2001; Wang et al., 2013; Yin and Har- al., 2006a, 2006b; Wang et al., 2017; Y. Wang et al., 2015), and kinematic rison, 2000; Yin, 2010). The sedimentary archives of these intermontane histories of fold-and-thrust belts and strike-slip faults along the northern, basins can be used to constrain the processes and mechanisms of the evo- western, and southern margins of the intermontane basin (F. Cheng et al., lution of Tibet (Metivier et al., 1998; Yin et al., 2002). Various indicators 2016b; Fu et al., 2015; Mao et al., 2016; Meng et al., 2001; Ritts et al., in sedimentary basins in southern Tibet, such as the termination of marine 2004, 2008; Wu et al., 2012; Yin et al., 2007a, 2008a, 2008b; Yue and Liou, facies sediments, the initial deposition of material derived from the Asian 1999; Yue et al., 2001; Zhang et al., 2016, 2018). plate on the Indian margin, and the earliest strata to include mixed India- Recent integrated analyses of seismic reflection profiles and thickness and Asia-sourced detritus, have been used to provide minimum constraints distributions of Cenozoic strata across the Qaidam Basin indicated that on the timing of the initial India-Asia collision (Garzanti et al., 1987, 1996; the basin structure is predominantly a broad Cenozoic synclinorium, and Najman, 2006). Sedimentologic, geochronologic, and structural analyses of hence the main depocenter lies persistently along the northwest-trending Cretaceous–Tertiary basins in central Tibet have indicated multiple-phase central axis of the basin (Yin et al., 2008a; Zhu et al., 2006). The spatial contractional deformation since the India-Asia collision (Horton et al., distribution of Cenozoic strata in the Qaidam Basin indicates that the 2002; Kapp et al., 2007; Li et al., 2017; Spurlin et al., 2005; Staisch et al., sediments are supplied by an endorheic drainage system with sources in 2014). Further northwards, in the Qaidam Basin, there are exceptionally several ranges: in the northern basin, mainly the southern Qilian Shan (Fig. 1A); in the western basin, mainly the Altyn Tagh Range; in the *[email protected] southwestern basin, mainly the Altyn Tagh Range and Qimen Tagh; and in Geological© 2018 The SocietyAuthors. of Gold America Open |Access: LITHOSPHERE This paper | Volume is published 11 | underNumber the 2 terms| www.gsapubs.org of the CC-BY-NC license. 252 Downloaded from http://pubs.geoscienceworld.org/gsa/lithosphere/article-pdf/11/2/252/4659951/252.pdf by guest on 29 September 2021 HAIJIAN LU ET AL. | Provenance of Cenozoic sediments in the northern Qaidam Basin RESEARCH 92oE 94oE 96oE 98oE A N Altyn Tagh Range N Nan Shan Commonly accepted paleocurrent o 39 t Tagh faul (Jian et al., 2013;Song et al., 2013; Altyn Saishenteng Shan Yin et al., 2008a; Zhuang et al., 2011） N Fig. 1C Qilian Shan o (Bush et al., 2016)- 38 Fig. 1D ~350 km Olongbluk Shan Qimen Tagh Qaidam basin Fig. 1B North Qaidam basin N o 37 Dahonggou Fig. 1E 80oE 110oE ~200 km section Aimunik Shan (Wang et al., 2017) Tarim N Basin o N Tibetan 40 o Plateau 36 East kunlun Shan Fig. 1A India N o Kunlun fault 20 01km 00 95°06′ E 95°12′ E 95°18′ E995°24′ E 5°30′ E 94°40′ E 94°45′ E94°50′ E C1 N Z Z B γδ ε PC-1 4 Z N 37°42′ PC-2 Lvliang Shan 50 °10′ SD-1 N 55 2y Z 38 N1 Z 46 N2y N C 1 Lulehe 75 K N2s E3g 84 E1-2l J3h N 60 1 37°36′ 39 K 70 K E3g E1-2l N1 E3g 24 45 53 (Bush et al., 2016) 72 N N2y N Xiao E3g N2s 37°30′ Qaidam lake (Wang et al., 65 2017; this study) Dahonggou 38°05′ (This study, Fig. 8H) Xitie Shan N 70 N PC-5 25 N 1 PC-3 2y E1-2l 65 PC-4 PC-7 N O3 Z PC-6 2s 70 37°24′ N (Ji et al., 2017) 20 1 E N 1-2l J1-2 70 N Yuqia C 2s 50 38°00′ 95°40′ E 95°45′ E 95°50′ E 95°55′ E 96°00′ E 97°37′ E 97°40′ E 97°43′ E N N Z Q C3 70 °59′ E J 70 3h E3g 36 37°38′ K 75 J3h 35 40 70 80 C2 C3 N J E 18 1-2 3g N J2 C2 50 N K N 2y 50 J 1 °56′ 17 56 37°35′ E SD-2 3h 1-2l D3 30 44 64 36 C 15 60 SD-5 1 45 N2s 70 40 N J 3h N2y 75 C1 J1-2 K N 37°32′ 42 Q Yinmaxia SD-3 44 PC-8 PC-9 SD-4 Z °53′ O Beidatan D 3 36 N N E E Q 2s 2y N1 3g 1-2l K Qigequan Fm. Shizigou Fm. Upper Youshashan Fm. Upper Ganchaigou Fm.Lower Ganchaigou Lulehe Fm. Cretaceous Quanyagou Lower Youshashan Fm. Fm. Fm. J 3h J1-2 T2 C3 C2 C1 D3 Upper Jurassic Lower Jurassic Triassic strata Upper Carboniferous Middle Carboniferous Lower Carboniferous Upper Devonian strata strata strata strata strata strata e Z O3 γδ4 PC-1 SD-3 Sinian strata Upper Ordovician strata Permian granitoids Thrust fault Strike-slip fault Paleocurrent data Sandstone samples Figure 1. Location maps of the study area and sampling sites. (A) Digital elevation model (DEM) of the Qaidam Basin and adjacent orogenic belts, with schematic sediment dispersal pathways feeding the northern Qaidam Basin from three distinct perspectives. See inset map for location. The black broken line represents the approximate outline of the northern Qaidam Basin. (B–E) Geological maps of the localities of Dahonggou (B), Yuqia (C), Yinmaxia (D), and Beidatan (E), with the distributions of sampling sites. Geological Society of America | LITHOSPHERE | Volume 11 | Number 2 | www.gsapubs.org 253 Downloaded from http://pubs.geoscienceworld.org/gsa/lithosphere/article-pdf/11/2/252/4659951/252.pdf by guest on 29 September 2021 HAIJIAN LU ET AL. | Provenance of Cenozoic sediments in the northern Qaidam Basin RESEARCH the southern basin, mainly the East Kunlun Shan. This sediment dispersal Basin exhibit a heavy mineral assemblage associated with magmatic and model has been widely substantiated by paleocurrent analyses within the metamorphic basements (e.g., pyroxene, hornblende, epidote, and gar- basin (Heermance et al., 2013; Ji et al., 2017; Jian et al., 2018; Meng and net), potentially derived from both the Kunlun Shan and Qimen Tagh Fang, 2008; Song et al., 2013; Wu et al., 2012; Zhuang et al., 2011).