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A new species of Papaveraceae, Corydalis sunhangii, in the section Trachycarpae, is described and illustrated from Nyingchi City, Xizang, China. The new species has some resemblance to Corydalis kingdonis, but differs by radical leaves prominent, usually several, blade tripinnate (vs. insignificant, few, blade bi‐ to triternate); cauline leaf usually one, much smaller than radical leaves, usually situated in lower half of stem (vs. usually two, larger than radical leaves, concentrated in upper third of stem); racemes densely 13–35‐flowered (vs. rather lax, 4–11‐flowered); claw of lower petal shallowly saccate (vs. very prominently and deeply saccate); capsule oblong, with raised lines of dense papillae (vs. broadly obovoid, smooth). Phylogenetic analysis, based on 68 protein‐coding plastid genes of 49 samples, shows that C. sunhangii is not closely related to any hitherto described species, which is consistent with our morphological analysis. [ABSTRACT FROM AUTHOR]

Trench basin, as an important sedimentary repository in oceanic subduction zones, documents faithfully the evolution of paleodrainage and paleogeographic information. Because of the frequent intense deformation during and after deposition, the recognition of trench-basin strata in orogenic belts is quite challenging. Several trench-fill deposits have been identified from the Yarlung Zangbo suture in southern Tibet, which can be classified into two types based on major differences in formation timing and tectonic setting. The first type developed during subduction of the Neotethyan oceanic slab in the Cretaceous (e.g., the Jiachala, Rongmawa, and Luogangcuo formations), and the second type developed during the initial stage of the India-Asia collision in the Palaeogene (e.g., the Sangdanlin-Zheya formations). The former was originally deposited on the subducting oceanic crust and then accreted as tectonic slices into the subduction complex; the latter was deposited unconformably on the continental margin of the subducting Indian plate and then involved in the subduction complex during the continental collision. Typical lithologies of trench-basin fills include abyssal chert, siliceous shale, silty to sandy turbidites, debris flows deposits, and slump deposits without carbonate. Detritus feeding these basins were chiefly from the uplifted terrane in the upper plate. This paper summarizes the geological features of trench basins developed in southern Tibet and proposes criteria for recognizing trench-basins in collisional orogens. [ABSTRACT FROM AUTHOR]