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The Three Gorges and Yichang areas of the Yangtze River are close to the eastern edge of the Qinghai-Tibet Plateau. Sediment proxies of paleoclimate trends in these areas are of great significance for the interpretation of the regional climatic impact of the episodic uplift of the Qinghai-Tibet Plateau. We examined the macro-sedimentary characteristics, clay mineralogy and geochemistry of sediments from the fan delta and lake deposits and the two river terraces of early and middle Quaternary age in the Yichang area and from the planation surfaces and the five main river terraces of early to late Quaternary age in the Three Gorges areas. The early and middle Quaternary had a generally warm-wet paleoclimate from 1260 to 300 ka. The regional climate changed to generally dry-cold conditions during late Quaternary (110–10 ka), that can be correlated to glacial cycles in the Tibetan Plateau. During the late Quaternary, especially after its Gonghe Movement (150 ka) uplift, the Qinghai-Tibet Plateau had a significant impact on regional climate. Comparing the formation age and source direction of the Wushan loess in the Three Gorge with loess in the western Sichuan (the Ganzi loess), in the Loess Plateau and distributing in the middle and lower reaches of the Yangtze River (the Xiashu loess), it can be found that coupling of the Kun-Huang Movement of the Qinghai-Tibet Plateau occurred at 1100–600 ka and Mid-Pleistocene Transition and global cooling resulted in the sharp increase of East Asian winter monsoon and plateau monsoon, forming the western Sichuan loess and Xiashu loess. The Gonghe movement (150 ka) of the Plateau once again enhanced the plateau monsoon and blocked the Indian summer monsoon moving north-eastward. As a result, the cold-dry climate appeared in the Sichuan Basin and the Three Gorges area, resulting in the deposition of loess from the Zoige Basin to Wushan area. • Paleoclimate changed from warm-wet to dry-cold in Quaternary in Three Gorges. • Paleoclimate in Three Gorges can only correspond with glacier-cycle after 150 Ka. • Tibetan Plateau's Gonghe Movement had a significant impact on paleoclimate. • Gonghe movement enhanced the Plateau monsoon and blocked the Indian summer monsoon. • Cold-dry climate and loess appeared in Sichuan basin after Gonghe movement. [ABSTRACT FROM AUTHOR]

Yibin area is located in the southwestern margin of Sichuan Basin of upper Yangtze River basin, close to the southeastern boundary of the Qinghai-Tibetan Plateau. The paleoclimatic characteristics recorded by Quaternary river sediments in this area can display the impact of uplift of the Qinghai-Tibetan Plateau on paleoclimate change of Sichuan Basin. In this paper, the macro-characteristics, clay minerals and the diagnosis geochemical elements characteristics of the sediments of terraces and floodplain were used as climatic proxies to explore the evolutionary process of the Quaternary paleoclimatic change in the study area. Key findings can be shown as follows: 1) warm and humid paleoclimate occurred during the Middle Pleistocene and the early Late Pleistocene (730–90 ka), shown by the high values of Al 2 O 3 , Fe 2 O 3 , Rb/Sr, chemical index of alteration (CIA, 82–97), illite chemical index (ICI, >0.5), kaolinite and the low values of Na 2 O, K 2 O, MgO, K 2 O/Al 2 O 3 , (CaO + Na 2 O)/Al 2 O 3 , illite, smectite, chlorite from the brown or brownish-red sediments of the terraces T5 to T3. 2) The reversal values of these geochemical and clay mineral proxies (e.g., values of CIA between 50 and 64) derived from grey and greyish-yellow sediments in terrace T2 and floodplain denote the dry and cold paleoclimate, emerging in the middle-late Late Pleistocene (50 ka), corresponding to the Baiyu glacial period of the Qinghai-Tibetan Plateau. Comparing the paleoclimatic evolutionary characteristics in Yibin area with those of the Three Gorges area of northeastern margin of Sichuan Basin from previous researches, this paper considers that during the Gonghe tectonic movement (0.15 Ma), the uplift of the Qinghai-Tibetan Plateau and its southeastern boundary intensified the Plateau winter monsoon and caused the southwesterly withdrawal of the Indian monsoon from Sichuan Basin. Consequently, the warm and humid paleoclimate at the northeastern and southwestern margins of the Basin had successively become dry and cold in the early and middle-late periods of the Late Pleistocene. • Paleoclimate information can be well preserved in terrace sediments in Yibin area. • The paleoclimate in Yibin area had changed from warm and wet to cold and dry since 50 ka. • Quaternary paleoclimate changed to dry and cold from northeast to southwest in the Sichuan Basin. • Tibetan Plateau's Gonghe tectonic movement enhanced the Plateau monsoon and blocked the Indian summer monsoon. • Influence of Indian summer monsoon weakened in the Sichuan Basin along the SW direction after 110 ka. [ABSTRACT FROM AUTHOR]

Based on thin section identification, scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis of samples from cuttings and cores in drillings, tuffaceous deposits were identified to intercalate in marine carbonate rocks and mudstones in the upper part of Maokou Formation and the middle to lower part of the Wujiaping Formation in Guangyuan area, northern Sichuan basin, China. These tuffaceous deposits are of significance to understand the influence range of magmatic activity of the Emeishan Large Igneous Provinces (ELIP), and explore and exploit oil and gas reservoirs in Permian strata in the Sichuan basin. The research results indicated that tuffs formed 0.1–10 mm-thick laminae, and they formed lamellar interbedding with organic mudstones and carbonaceous mudstones, which were sandwiched among bioclast limestones and marls. Tuffaceous deposits in the study area include tuff, sedimentary tuff and tuffaceous sedimentary rock. Under the influence of sulfate reduction, acidic hydrotherm and alkaline fluid, tuffaceous deposits were altered by diagenesis such as dolomitization, argillization, pyritization and dissolution, and formed a variety of secondary rocks and pores which characterized by the micron-scale solution pores in tuff components and the nanometer-scale intercrystal pores among authigenic clay minerals. In addition, the primary directional sedimentary structure of tuffs and sedimentary tuffs and developed laminae in the rocks are conducive to the formation of fissures parallel to laminae, and effectively improve the reservoir property of rocks. The tuffaceous deposits in the study area are mainly the products of subaqueous pyroclastic flow that were dominated by acidic magmatism and indicated that they may not be directly related to the ELIP, which is located in the southwest Sichuan-Yunnan provinces and dominated by continental eruption of basalt. • Tuff was identified in drill cores in Permian marine sediments in Sichuan basin. • Clayization, pyritization, dolomitization and dissolution are the main diagenesis. • Solution pore, intercrystal pore and bedding-plane fissure are main reservoir space. • Sulfate reduction, acidic hydrotherm and alkaline fluid controlled diagenesis. • Tuff may be formed by subaqueous pyroclastic flow and air-fall ash. [ABSTRACT FROM AUTHOR]