Landscape configuration of eastern South China during the late Neoproterozoic: New constraints from sedimentary indices and zircon U-Pb-Hf isotopes of the southeastern margin of the Yangtze Block

The study of the paleogeographic landscapes of South China can contribute to understanding its paleo-position within supercontinents. We conducted a combined study of the Nanhuan-Sinian sedimentary records from the southeastern margin of the Yangtze Block (SMYB) in South China. The results reveal the following. (1) 18 datasets from directional sedimentary structures in the strata of the northern and southern SMYB indicate that the siliciclasts were transported towards the SE-SSE and the NWW-NW-NNW-NNE-NE, respectively. (2) 1670 analyses of 18 zircon samples collected from or near the directional structures have concordant U-Pb ages of 3243-563 Ma. 15 detrital zircon samples have a major peak within the range of 850-730 Ma, and 7 detrital zircon samples have epsilon(Hf)(t) values ranging from - 38.7 to + 13.7, and two-stage modal ages of 4.1-0.9 Ga. These new data reveal three important paleogeographic features of eastern South China during the late Tonian to Ediacaran, as follows. (a) The SMYB was a sedimentary basin (called the "Zhe-Gan-Wan Basin") with opposing paleotopographic dips on two sides. Its northern part was mainly inclined to the SW-S-SE and belonged to the foreslope of the eastern Yangtze Platform. Conversely, its southern part was mainly inclined to the NW-N-NE and was the submerged part of the eroded area in the eastern Cathaysia Block (ECB) extending to the north. (b) The eroded area (called "Zhe-Min Land") was probably located within the northeastern ECB and was surrounded by depositional areas on at least three sides. The ECB was likely connected to a Grenville-age orogen in the south direction. (c) The paleogeographic landscape configuration of eastern South China may have comprised five domains, from north to south: the eastern Yangtze Platform, the Zhe-Gan-Wan Basin, the Zhe-Min Land in the northeastern ECB, the Gan-Min-Zhe Basin, and a Grenville-age orogen. According to the landscape configuration, during the supercontinental cycles from Rodinia to Gondwana, the Cathaysia Block was likely located on the margin of the supercontinents, close to North India, West Australia, and East Antarctica.