The Stages of Debris Flow Activity During the Quaternary in the Xiaojiang River Basin, China

This study aimed to predict the laws and trends of modern debris flow by examining the activity cycle of debris flow during the Quaternary and its relationship with environmental change. The timing of the debris flow activity period was determined using sediment dating data based on typical debris flow deposition profiles selected from various terraces in the Xiaojiang River Basin, China. The relationships between debris flow and environmental change were compared and analyzed using neotectonic history, the deep-sea oxygen isotope δ18O curve, and the loess paleosol series. The results showed that the debris flow activities in the Xiaojiang River Basin could divided into eight activity cycles, namely 11.42 Ma, 0.985 Ma, 0.562–0.52 Ma, 0.218 Ma, 0.137 Ma, 14 Ka, 0.73 Ka, and since 3 Ka. The activity cycle of debris flow deposition coincided with the neotectonically active period. Neotectonic movement has controlled the cycle of large debris flow deposition in the Xiaojiang River Basin since the Quaternary. The sedimentary activity of debris flow was not completely consistent with a warm and humid climate, and the sedimentation activity of debris flow was the result of the combined effects of tectonic movement and climate change.

Two new species and the molecular phylogeography of the freshwater crab genus Bottapotamon (Crustacea: Decapoda: Brachyura: Potamidae)

Bottapotamon chenzhouense sp. n. and B. luxiense sp. n. are described from Hunan Province and Jiangxi Province, respectively. These species both have diagnostic features of the genus Bottapotamon and discernible characteristics as new species. B. chenzhouense sp. n. can be distinguished from co-geners by features such as the G1, which has a fold covering the surface of the entire subterminal article with a distal region. B. luxiense sp. n. has an elliptical carapace, and a sturdy and blunt terminal article of G1. The molecular phylogeny and biogeography of the genus Bottapotamon (Decapoda: Brachyura: Potamidae) were studied, using mitochondrial cytochrome oxidase I (mtDNA COI), 16S rRNA and nuclear histone H3 gene fragments. The results support the assignment of the two new species to the genus Bottapotamon. In addition, the divergence time of the genus Bottapotamon was estimated to be 3.49–1.08 Ma, which coincided with various vicariant and dispersal events that occurred in the geological area where the genus Bottapotamon is commonly distributed. Mountains appear to have played an important role in the distribution of this genus. The Wuyi Mountains gradually formed offshore and inland of southeastern China by the compression of the Pacific plate and the Indian plate in the Neogene-Quaternary, and the Luoxiao Mountains formed continuously in the continued forming in the north-south direction because of neotectonic movement, have resulted in the geographical distribution pattern of the genus Bottapotamon, which was also established gradually.

Cause Analysis of Zhaohe Debris Flow in Erlong Town in Zhenping County in Henan Province

Debris flow is one of the major geological disasters in mountain areas. This paper systematically analyzes the influence of steep terrain conditions, the development of regional structure, neotectonic movement and earthquake, wide distribution of debris, human engineering activity and rainfall concentrated climate conditions in debris flow area. The dominant factors inducing Zhaohe debris flow were revealed, providing guidance for the debris flow disaster prevention, as well as reference for the same area debris flow cause analysis.