Onset of Permanent Taklimakan Desert Linked to the Mid
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https://doi.org/10.1130/G47406.1 Manuscript received 19 January 2020 Revised manuscript received 5 March 2020 Manuscript accepted 18 March 2020 © 2020 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license. Published online 12 May 2020 Onset of permanent Taklimakan Desert linked to the mid-Pleistocene transition Weiguo Liu1,2, Zhonghui Liu3*, Jimin Sun2,4,5, Chunhui Song6, Hong Chang1, Huanye Wang1, Zheng Wang1 and Zhisheng An1,2* 1 State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Center for Excellence in Quaternary Science and Global Change, Chinese Academy of Sciences, 710061 Xi’an, China 2 University of Chinese Academy of Sciences, Beijing 100049, China 3 Department of Earth Sciences, The University of Hong Kong, Hong Kong, China 4 Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences (CAS), Beijing 100029, China 5 CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing 100101, China 6 Key Laboratory of Western China’s Mineral Resources of Gansu Province & School of Earth Sciences, Lanzhou University, Lanzhou 730000, China ABSTRACT gocene (Zhu et al., 1980; Fang et al., 2002a; The initial occurrence of desert landscape or eolian sand dunes is thought to have occurred Sun et al., 2009; Zheng et al., 2015; Heermance long before the Pleistocene, and desertification was subsequently enhanced under cold, dusty et al., 2018). Proposed possible mechanisms for glacial conditions. However, when and how the desert landscape persisted during both gla- Asian inland aridification, and by inference, cial and interglacial periods, defined as “permanent” desert here, remain elusive. Here, we desertification, include tectonic uplift (Fang present carbonate carbon isotope and grain-size records from the Tarim Basin, western et al., 2002a), land-sea distributions (Bosboom China, revealing a detailed desertification history for the Taklimakan Desert. Our records et al., 2014), and Cenozoic global cooling (Miao demonstrate that after desiccation of episodic lakes at ca. 4.9 Ma, alternations of eolian sand et al., 2012). It is generally believed that the dunes and fluvial and playa-like conditions persisted for a long period until 0.7 Ma in the initial desert landscape occurred well before the Tarim Basin. The onset of permanent desert landscape around 0.7–0.5 Ma occurred concur- Pleistocene, and desertification was enhanced rently with the climatic reorganization across the mid-Pleistocene transition. The occurrence under cold, dusty Pleistocene glacial condi- of mountain glaciers on the Tibetan Plateau and atmospheric circulation changes may have tions. However, little is known about when and controlled the formation and extreme aridification of the permanent desert in inland Asia how the desert ceased being replaced by other since the mid-Pleistocene transition. landscapes during relatively warm, humid inter- glacial periods, such as the present Holocene INTRODUCTION of the basin, with little vegetation (Zhu et al., period, defined as “permanent” desert, which Long, continuous terrestrial records docu- 1980). Summer subtropical anticyclone and is addressed here. menting inland aridity changes are extremely air subsidence there are thought to be remotely limited, preventing our understanding of the forced by the rising activity in monsoon regions METHOD development of aridification and desertifica- (Rodwell and Hoskins, 1996; Sato and Kimura, We used a 1050-m-long, continuous borehole tion in continent inland areas and their asso- 2005). A detailed aridification history over the (Ls2) that we drilled at Lop Nur (39°46′0″N, ciation with Pliocene–Pleistocene global cli- Pliocene–Pleistocene period from this region, 88°23′19″E) in the eastern Tarim Basin (Fig. 1). matic changes. The Taklimakan Desert in the which is perhaps most representative of inland Previous studies have established a robust chro- Tarim Basin, western China (Fig. 1), the sec- aridity changes around the globe, would help nology (Fig. S1A in the Supplemental Material1; ond largest shifting-sand desert in the world, us to understand monsoon-desert dynamics in Chang et al., 2012), and, through study of the is part of the prominent arid zone in Central response to global climatic changes. lower section of the core (651–1050 m), inferred Asia. Today, extremely dry climate prevails in Although it has been extensively studied over the occurrence of late Miocene episodic lakes, the basin (annual precipitation < 50 mm at its the past decades, the timing and mechanisms based on carbonate oxygen and boron isotopes center), and shifting sand dunes occupy most of Taklimakan Desert formation still remain (Liu et al., 2014). We here addressed how the elusive. The proposed timing, mostly based on Taklimakan Desert evolved into its present form the initial occurrence of eolian deposits, ranges after the episodic lakes dried up at ca. 4.9 Ma *E-mails: [email protected]; [email protected]. from the Pleistocene to Miocene and late Oli- (Liu et al., 2014; Sun et al., 2017). Existing 1Supplemental Material. Materials, methods, and interpretations, Figure S1 (stratigraphic columns and age assignments), Figure S2 (δ13C correlated with rainfall and temperature), Figure S3 (detailed view of the onset of desertification), Figure S4 (representative core photos), Figure S5 (Lop Nur and Mazartagδ 13C), Figure S6 (spectral results), Figure S7 (close-up views of records), and Table S1 (δ18O, δ13C, and grain-size data). Please visit https://doi .org/10.1130/GEOL.26213S.12221885 to access the supplemental material, and contact [email protected] with any questions. CITATION: Liu, W., et al., 2020, Onset of permanent Taklimakan Desert linked to the mid-Pleistocene transition: Geology, v. 48, p. 782–786, https://doi .org/10.1130/ G47406.1 782 www.gsapubs.org | Volume 48 | Number 8 | GEOLOGY | Geological Society of America Downloaded from http://pubs.geoscienceworld.org/gsa/geology/article-pdf/48/8/782/5095912/782.pdf by guest on 03 October 2021 50°N Figure 1. Geographic 300 mm locations of the studied Gurbantunggut Desert Lop Nur and Mazartag Height (m) profiles in the Tarim Basin, western China. Base Tianshan Mt. 5000 topographic map was 40°N Tarim Basin Chinese Loess Plateau generated with ArcGIS Pamir Qaidam 4000 software. The Tarim Basin Kunlun Mt. is currently surrounded by Tibetan Plateau 3000 high mountains with aver- age elevations >4000 m. 30°N 2000 Dashed line is 300 mm annual precipitation line, 500 which roughly separates the Asian inland from Lop Nur monsoonal regions. Inset 0 Taklimakan Desert map shows locations of 20°N Tarim Basin Lop Nur borehole (star), -500 Indian Ocean Mazartag upper Mazartag (a) and lower Mazartag (b) sec- a b tions, and river system in km km Tarim Basin. 0 250 500 1000 0 200 400 60°E 70°E 80°E 90°E 100°E 110°E 120°E records from exposed Mazartag sections in RESULTS AND DISCUSSION positive between 3 and 0.7 Ma. Since ca. 0.7 Ma, 13 13 the central basin (Fig. 1; Pei et al., 2011; Sun Our δ Ccarb record over the past 7.1 m.y. δ Ccarb values stayed around 0‰ ±1‰, close to et al., 2017), where previously controversial age shows a long-term trend toward more positive the background signal in detrital carbonates (Liu assignments have been reconciled with a newly values, with large variability between ∼1‰ and et al., 2014). The grain-size record (Fig. 2C) reported mammal fossil (Fig. S1C; Sun et al., −5‰ (Fig. 2B). After the episodic lacustrine also shows large variability in modal size, from 2017), were also integrated to infer basinwide phase, as evidenced by the high variability in 5–10 µm to 100–150 µm before ca. 0.5 Ma. An 18 paleoenvironmental changes. Lop Nur cur- δ Ocarb between 7.1 and 4.9 Ma (Fig. 2D; Liu abrupt increase occurred at ca. 0.5 Ma, and since 13 rently lies at the lowest elevation in the eastern et al., 2014), δ Ccarb values ranged from ∼0‰ then, the modal size has varied between ∼100 and basin, ∼800 m above sea level, and is terminal to −5‰ between 4.9 and 3 Ma, and from ∼1‰ 200 µm (Fig. 2C; Fig. S3). Notably, after the mid- for receiving river water in the basin, and the to −3‰ with a trend becoming progressively Pleistocene transition (MPT) between ca. 1.25 Mazartag sections are at ∼1150 m in the central basin (Fig. 1), so the borehole at Lop Nur would likely record the last stage of aridity changes 01234567 in the basin, while approximately synchronous 28 MPT NHG signals at both locations could indicate major, A 26 basinwide paleoenvironmental changes. Figure 2. Proxy records °C) ODP 846 ( E. Pacific -6 We generated carbonate carbon isotope 24 over past 7.1 m.y. in the 13 SST Tarim Basin, western (δ Ccarb) and grain-size records at very high 22 China. (A) Sea-surface resolution (<2 k.y. on average; Table S1). The -4 13 temperature (SST) record δ Ccarb values from eolian and fluvial deposits 20 from Ocean Drilling Pro- can become progressively negative with the input B gram (ODP) Site 846 in the 13 of soil organic carbon during soil pedogenesis -2 C (‰) eastern equatorial Pacific (see the Supplemental Material, and Fig. S2; Liu (Herbert et al., 2016). (B) 13C , (C) grain size, et al., 2011; Sun et al., 2015; Caves et al., 2016). δ carb 0 and (D) 18O from the 13 δ carb Hence, δ Ccarb can effectively reflect regional Lop Nur borehole (this vegetation cover and biological productivity in Lop Nur Mazartag study; Liu et al., 2014) 0 2 and Mazartag sections arid and semiarid regions. Grain size, due to its C complicated nature, is used here as a support- (Pei et al., 2011; Sun et al., 50 2017).