Late Cretaceous−early Paleogene rise of the Gangdese magmatic arc (south Tibet) from sea level to high mountains

Abstract

Recognition of the existence of an Andean-type continental margin in southern Tibet prior to its collision with India has provided crucial constraints on the formation of the Tibetan Plateau and South Asian climate evolution. Here, we focused on well-dated Late Cretaceous successions in the Linzhou Basin and determined the elevation changes from sea level to high mountains in the Gangdese magmatic arc in southern Tibet. Our results show that the Linzhou Basin was still submerged in the Tethyan Sea at around 92 Ma when it accumulated Cenomanian (ca. 105−92 Ma) shallow-marine orbitolinid-bearing limestones (Takena Formation); these limestones are unconformably overlain by Campanian (83−78 Ma) fluvial-lacustrine deposits (Shexing Formation) after an ∼9 m.y. depositional hiatus. A prominent unconformity between the tightly folded Shexing Formation and gently tilted overlying Paleocene−Eocene Linzizong successions represents the formation of the regional Lhasaplano ca. 70 Ma, which may have been linked to the rise of an Andean-type Gangdese mountain range along the southern margin of the Lhasa terrane. Using carbonate oxygen isotope and clumped isotope thermometry data from the Shexing Formation paleosols, we quantitatively documented the rise of the Andean-type Gangdese Mountains with a peneplain surface at an elevation of 2.7 +0.5/−0.9 km above sea level prior to onset of the India-Asia collision ca. 65−63 Ma. This scenario of surface gain may have been an isostatic compensation response to the crust thickening to over 50 km during the Late Cretaceous. Subsequently, the surface isostatically rose to its near-present elevation of ∼4.6 km due to the removal of overthickened mantle lithosphere and revival of intense Gangdese magmatism by 56 Ma.

Sedimentary Record of the middle Cretaceous uplift across the Gangdese magmatic arc system in Southern Tibet

“…The Gangdese magmatic arc is believed to have achieved an elevation of approximately three kilometres by the late Upper Cretaceous (Ding et al., 2014, 2022; Murphy et al., 1997; Xu et al., 2022). Topography of the arc massif played a considerable role in Cenozoic climate change of the interior Tibetan Plateau by enhancing the monsoonal climate system and acting as an orographic barrier to Neo‐Tethys Ocean moisture sources to the south (DeCelles et al., 2007; Ding et al., 2014; Spicer, 2017; Spicer et al., 2021; Xu et al., 2022). In ancient active‐margin settings, the sedimentary records within forearc and retroarc strata are excellent proxies for arc magmatism, paleotopography of the arc, and regional drainage patterns between the arc and associated basins (Barth et al., 2013; Capaldi et al., 2021; de Silva et al., 2015; DeGraaff‐Surpless & Graham, 2002; Malkowski, Schwartz, et al., 2017; Schwartz et al., 2021; Sharman et al., 2015).…”

“…The Gangdese magmatic arc is believed to have achieved an elevation of approximately three kilometres by the late Upper Cretaceous (Ding et al., 2014, 2022; Murphy et al., 1997; Xu et al., 2022). Topography of the arc massif played a considerable role in Cenozoic climate change of the interior Tibetan Plateau by enhancing the monsoonal climate system and acting as an orographic barrier to Neo‐Tethys Ocean moisture sources to the south (DeCelles et al., 2007; Ding et al., 2014; Spicer, 2017; Spicer et al., 2021; Xu et al., 2022).…”

“…North of the Gangdese arc, the Linzhou retroarc foreland basin straddles the boundary between Southern and Central Lhasa (Figure 2). The basin is confined by the Gangdese arc in the south and by a series of north‐dipping thrust faults in the north (Meng et al., 2019; Wang et al., 2020; Xu et al., 2022) (Figure 2a). The stratigraphy of the Linzhou basin includes two parts, a lower shallow‐marine Orbitolinid‐bearing limestone of the Takena Formation (approximately equivalent to the Penbo member of Leier, DeCelles, et al., 2007) and the upper fluvial red beds of the Shexing Formation (approximately equivalent to the Lhunzhub member of Leier, DeCelles, et al., 2007) (Figure 2a).…”