Late Miocene episodic lakes in the arid Tarim Basin, western China

• Published in: Proceedings of the National Academy of Sciences - PNAS 2014-11, Vol.111 (46), p.16292-16296
• Main Authors: Liu, Weiguo, Liu, Zhonghui, An, Zhisheng, Sun, Jimin, Chang, Hong, Wang, Ning, Dong, Jibao, Wang, Huanye
• Format: Article
• Language: English
• Subjects: Axial tilt; Carbonates; Cooling; Desertification; Deserts; Dust; Geological time; Geology; Lakes; Moisture; Numerical eccentricity; Paleoclimatology; Physical Sciences; Plateaus; Tectonics
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1410890111

The Tibetan Plateau uplift and Cenozoic global cooling are thought to induce enhanced aridification in the Asian interior. Although the onset of Asian desertification is proposed to have started in the earliest Miocene, prevailing desert environment in the Tarim Basin, currently providing much of the Asian eolian dust sources, is only a geologically recent phenomenon. Here we report episodic occurrences of lacustrine environments during the Late Miocene and investigate how the episodic lakes vanished in the basin. Our oxygen isotopic (δ ¹⁸O) record demonstrates that before the prevailing desert environment, episodic changes frequently alternating between lacustrine and fluvial-eolian environments can be linked to orbital variations. Wetter lacustrine phases generally corresponded to periods of high eccentricity and possibly high obliquity, and vice versa, suggesting a temperature control on the regional moisture level on orbital timescales. Boron isotopic (δ ¹¹B) and δ ¹⁸O records, together with other geochemical indicators, consistently show that the episodic lakes finally dried up at ∼4.9 million years ago (Ma), permanently and irreversibly. Although the episodic occurrences of lakes appear to be linked to orbitally induced global climatic changes, the plateau (Tibetan, Pamir, and Tianshan) uplift was primarily responsible for the final vanishing of the episodic lakes in the Tarim Basin, occurring at a relatively warm, stable climate period. Significance The relative roles of the two plausible causes, Cenozoic global cooling and Tibetan Plateau uplift, for the Asian interior aridification/desertification are often difficult to disentangle. High-quality terrestrial records from the Tarim Basin document how enhanced aridification occurred over the last 7 my, from episodic lacustrine environments to the currently prevailing desert environments. During the Late Miocene–Early Pliocene period, episodic occurrences of great lakes and thus wetter climate closely corresponded to periods of high eccentricity and possibly high obliquity, suggesting that the uplifted plateau by then did not effectively block the moisture availability at optimum climatic conditions. The finally irreversible drying up of great lakes at ∼4.9 Ma could be attributed to the plateau uplift.