No abstract

In the Cenozoic, fault-related basins, including the Wei River, Lingbao and Linfen basins, developed on the southeast margin of the Ordos Block. Based on the latest drilling data and previous research results, this article analysed the evolutionary processes, temporal and spatial relationships and tectonic background of these basins, and obtained the following results: (a) The Wei River Basin and the Lingbao Basin belong to a unified basin, which formed in the Palaeocene and developed gradually from east to west. (b) The Linfen Basin formed in the late Miocene and developed gradually from southwest to northeast. (c) The evolution of the basin systems was dominated by the westward subduction of the Pacific Plate in the Palaeogene and then by a combination effects of the subduction of the Pacific Plate and the uplift of the Tibetan Plateau. (d) The so-called Fen-Wei Graben is not supported by the different geological evolutionary histories of the Wei River Basin and the Linfen Basin.

In the study of global change, the relationship between the Holocene climatic disaster events and the rise and fall of ancient civilization is of considerable significance to a profound understanding of civilization evolution and human-land harmony. During the geological survey in the western Wei River Basin, a debris-flow event that would have destroyed an archaeological site was uncovered in the Holocene loesson the south bank of the Qian River. They were studied by field observations and laboratory analysis, including magnetic susceptibility, particle size distribution, carbonate content determination, and AMS 14 C dating. The debris-flow event was dated at about 3702 BP to 4084 cal BP by using the AMS 14 C in combination with archaeological artefacts age determination. Mingling with cultural layer, whole pig bones, and covering ash pit and cellars, the debris flow incident was linked to the site destruction. Combined with the global climate background at about 4000 a BP, the palaeo-floods records in the Wei River Basin, and the regional palaeo-earthquakes, we infer that the debris-flow was triggered by large earthquake and heavy rainfall and was a regional hydrological response to the 4.0 ka global climate event. Moreover, the debris-flow incident and its resulting archaeological site ruin have essential scientific significance for exploring the climate environment evolution, the ancient civilization evolvement, and the human-land relationship development in the Wei River Basin and surrounding area.

The Earth's climate had undergone a global transition around 4-3 Ma, from warm to cool. The western Wei River Basin, its late Cenozoic tectonic evolution was mainly controlled by the expansion of the Tibetan Plateau, is affected by both Monsoon climate and Westerlies circulation. A set of lacustrine sediments between 4.2 and 3.6 Ma with clearly sedimentary rhythm are good materials for studying the palaeoclimate/palaeoenvironment changes and exploring the contained tectonic implications. We present a high-resolution grain-sized, magnetic susceptible, and carbonate content records from the palaeolake sediments at the global climate transition interval (4.2-3.6 Ma) in the western Wei River Basin. The abrupt changes of climate indicators at about 4.14-4.16 Ma, which is a regional response to global cooling, indicate that both westerly and monsoonal circulations were enhanced and should be attributed to global cooling rather than the uplift of TibetanPlateau. From 4.14 to 3.6 Ma, the climate represented stepwise strengthening or weakening with frequent fluctuations on the millennium scale and extreme dry events at 3.77-3.80 Ma. Combined with regional geological environment and palaeoclimate evolution data, the palaeolake that rapidly receded at 3.6 Ma provides evidence for the understanding the major climatic and environmental changes produced by the uplift of the Tibetan Plateau in western Wei River Basin and surrounding areas.