Guoli Wu

Detrital zircon evidence for the linkage of the South China block with Gondwanaland in early Palaeozoic time

LA-ICP-MS U–Pb dating of Lower Devonian detrital zircon samples from three representative sections in the South China block yields dominant Grenvillian and Pan-African populations, similar to the age distribution of early Palaeozoic samples from Gondwana, the Tethyan Himalaya and West Australia, in particular. Hf isotopic compositions indicate the contributions of juvenile crust at 1.6 Ga and 2.5 Ga, and bear a resemblance to their counterparts from SE Australia and West Antarctica, revealing the mixed origin of the Pan-African and Grenvillian grains from juvenile magmas and melting of pre-existing crustal rocks. These results suggest that the South China block should be considered an integral part of East Gondwana in early Palaeozoic time, rather than a discrete continental block in the Palaeo-Pacific or a fragment of Laurentia.

Multisource data registration based on NURBS description of contours

This paper presents a novel contour‐based approach for multisource image registration. The contours are parameterized with Non‐Uniform Rational B‐Splines (NURBS). The control points of parametric contours are used as contour descriptor for image registration due to their invariance under affine and perspective transformations. The distance of control points, and the curvature and orientation similarity of the corresponding segments induced by the control points are considered as the matching criteria, and mismatching of control points can be avoided effectively because of the local controllability of NURBS. Therefore, the method is able to deal with the case in which the corresponding contours are locally distorted. Additionally, the NURBS description of contours has the strong global property; the method is therefore robust to image noise. In order to improve robustness, we perform the extraction and labelling of contours interactively. The experiments on both single‐sensor and multisource data registration demonstrate the effectiveness and robustness of the presented method.

Multiple controls on rift basin sedimentation in volcanic settings: Insights from the anatomy of a small Early Cretaceous basin in the Yanshan belt, northern North China

This paper deals with a small continental rift basin in a volcanic setting and tries to decipher potential controls on its synrift sedimentation. The Luanping basin, which is a well-exposed Early Cretaceous rift basin in the Yanshan belt on the northern periphery of the North China block, was chosen as a case study. We show that extensive and vigorous volcanism took place just prior to the onset of basin formation and continued into a synrift period. Basin fills consist predominantly of lacustrine, fan-delta, braid-delta, and volcaniclastic deposits. Lacustrine facies are composed mostly of deep-lake deposits that appear to have been established soon after basin initiation. Fan-delta systems developed along two high-angle border faults, the master northern Hongqi fault and the secondary western Xiaobaiqi fault. Fan-delta fronts were built up primarily by gravelly and sandy debrites and turbidites. Braid-delta deposits are restricted to the eastern corner of the basin and are characterized by an aggregation of braid-plain conglomeratic deposits. Underwater extrusions of magma and pyroclastic flows are inferred from the presence of volcanic breccias, ignimbrites, andesitic pillows, and peperites, which are enclosed by host lacustrine deposits. Deep-lake and fan-delta systems persisted throughout the synrift period, indicating a rapid subsidence rate, with both adequate sediment and water supply. The high-angle border faults are thought to have played a critical role in creating large accommodation space, and simultaneous displacements of the Hongqi and Xiaobaiqi faults led to the localization of a major depocenter in the western part of the basin. One-dimensional backstripping analysis of three stratigraphic sections shows that the Luanping basin experienced marked synrift tectonic subsidence up to 2 km at a subsidence rate close to 0.2 mm yr −1 . We propose that the high rate of basin subsidence might have been caused mainly by left-lateral transtensional faulting and was enhanced by the superposition of basement downsag induced by underlying magma withdrawal. A predominance of volcanic particles in both debrites and sandstones suggests that source areas were erodible volcanic edifices. A humid paleoclimate is inferred, which not only provided enough water supply, but also promoted weathering of volcanic rocks in source areas, thus maintaining both the deep-lake environment and sediment influx. We conclude that relatively small and isolated rift basins in volcanic settings can experience both rapid subsidence and receive thick lacustrine deposits if they are under the combined control of favorable structure, climate, and magmatism. The model proposed here is believed to be applicable to other rift basins in similar volcano-tectonic settings.

Revisiting Triassic stratigraphy of the Yanshan belt

Age determinations of the Triassic lithostratigraphic units of the Yanshan belt were previously based on plant fossils and regional correlations of lithologies. The Liujiagou and Heshanggou Formations were assigned as the Lower Triassic, and the Ermaying Formation was regarded as the Middle Triassic. We carried out a geochronologic study of detrital zircon grains from the Triassic sandstone in the Xiabancheng and Yingzi basins in northern Hebei where the Triassic strata are exceptionally well preserved. The results show that the Liujiagou, Heshanggou, and Ermaying Formations are all Late Triassic in age. The ages of detrital zircons also revealed that the upper part of the Shihezi Formation and the overlying Sunjiagou Formation, both of which were thought to be the Middle-Late Permian units, are actually late Early to Middle Triassic deposits. This study combines the upper Shihezi and Sunjiagou Formations into a single unit termed as the Yingzi Formation. We also substitute the widely-used Liujiagou, Heshanggou, and Ermaying Formations with the Dingjiagou, Xiabancheng, and Huzhangzi Formations, respectively. Field observations and facies analysis show that the top of the Shihezi Formation is an erosive surface, marking a parallel unconformity between the Middle Permian and Lower Triassic. The Yingzi Formation is composed mainly of meandering river deposits, indicative of tectonic quiescence and low-relief landform in the Early to Middle Triassic. In contrast, the Dingjiagou, Xiabancheng, and Huzhangzi Formations are interpreted as the deposits of sandy/gravelly braided rivers, alluvial fans, fan deltas, and deep lakes in association with volcanism, thus indicating an intense rifting setting. A new Triassic lithostratigraphic division is proposed according to age constraints and facies analysis, and the results are of significance for understanding the early Mesozoic tectonic evolution of the Yanshan belt.