Mesozoic‐Cenozoic evolution of the Xining‐Minhe and Dangchang basins, northeastern Tibetan Plateau: Magnetostratigraphic and biostratigraphic results

Abstract

[1] Accurate stratigraphic ages are crucial to understanding the deformation history of the Tibetan Plateau prior to and during the Indo-Asian collision. Efforts to quantify MesozoicCenozoic ages are hindered by limited fossils and a paucity of volcanic horizons and regionally correlative strata. Magnetostratigraphic and biostratigraphic results from the Xining-Minhe-Longzhong basin complex and Dangchang basin provide an improved chronology of nonmarine basin development over a large region of the northeastern Tibetan Plateau (34-37°N, 101-105°E). Analyses of 171 magnetostratigraphic levels and 24 palynological assemblages (>120 species) indicate Late Jurassic-Early Cretaceous to mid-Tertiary deposition. Although magnetic polarity zonation is incomplete, independent palynological age control partially restricts possible correlations to the Geomagnetic Polarity Timescale. The sediment accumulation record, basin provenance, structural geology, and published thermochronological data support a history of Jurassic exhumation, Late Jurassic-Early Cretaceous fault-related basin initiation, and Cretaceous-Paleogene reduced accumulation. These patterns, which are compatible with Late Jurassic-Early Cretaceous extension and Cretaceous-Paleogene postrift thermal subsidence, were disrupted at about 40-30 Ma, when shortening related to the Indo-Asian collision induced localized range uplift, vertical axis rotation, and amplified subsidence.INDEX TERMS: 1520

A late Eocene palynological record of climate change and Tibetan Plateau uplift (Xining Basin, China)

“…38 Ma (Dupont-Nivet et al, 2008; now dated at 36.1 Ma (C16n.2n), see Abels et al, 2011). Additionally, there is evidence for tectonism and exhumation starting at 45-50 Ma in the West Qinling range at the southern edge of the Xining basin Horton et al, 2004;Clark et al, 2010).…”

“…Typical taxa of the deciduous forests are Quercoidites, Caryapollenites, Celtipollenites, Ulmipollenites, Cupuliferoipollenites, Juglanspollenites, Tiliaepollenites, Betulaceoipollenites, Salixipollenites and pollen types with affinity Fagaceae. These taxa mostly occur in the lower part of the section (zones A and B) and are indicative of temperate and warm, humid climates, which at present form the lower vegetation belts in temperate to subtropical mountainous regions (Wang et al, 1990;Horton et al, 2004;Sun and Wang, 2005;Fauquette et al, 2006;Miao et al, 2008). Subtropical pollen taxa are rare in the succession except for e.g.…”

“…Past occurrences of Ephedripites and Nitrariadites/Nitraripollis in the Tibetan region date as far back as early Paleogene, coinciding with the time when an arid belt extended over most of China (Wang et al, 1990;Horton et al, 2004;Sun and Wang, 2005). The abundance of xerophytes such as Ephedripites and Nitrariadites/ Nitraripollis in the Xining Basin (Figs.…”

Climatic and tectonic controls on sedimentation and erosion during the Pliocene-Quaternary in the Qaidam Basin (China)

“…Both tectonic uplift and climate change can infl uence sedimentation patterns, and thus any causal interpretation of stratigraphy must account for both tectonic and climatic infl uences. Strata preserved within the Qaidam and other nearby basins in the northeastern Tibetan Plateau record tectonic and climatic changes since at least Paleocene time (Pares et al, 2003;Fang et al, 2003Fang et al, , 2007Horton et al, 2004;Zhou et al, 2006;Yin et al, 2008;Craddock et al, 2011;Zhuang et al, 2011b;H.-P. Zhang et al, 2012). Differentiating the tectonic versus climatic controls on sedimentation at any of these localities, however, is complicated by the competing infl uences of both tectonics and climate on sedimentation.…”

A Review of Recent Advances in Red-Clay Environmental Magnetism and Paleoclimate History on the Chinese Loess Plateau

“…Apatite fission track data from hanging wall of the Liupan Shan thrust fault reveal almost invariant ages of 8 Ma below a fossil partial annealing zone, suggesting that initiation of rapid uplift and exhumation of the Liupan Shan at the same time (Zheng et al, 2006). The western CLP belongs to the Longzhong Basin, which is a Cenozoic foreland basin as a result of India-Asia collision (Horton et al, 2004). The eastern CLP belongs to the Ordos block, which is bounded by the Luliang Shan to the east, the Qinling Shan to the south, the Helan Shan to the west, and the Yin Shan to the north (Song et al, 2001).…”