Origin of the Red Earth sequence on the northeastern Tibetan Plateau and its implications for regional aridity since the middle Miocene

Hippotherium Datum implies Miocene palaeoecological pattern

Here, we report well-preserved skulls and postcranial specimens of genus Hippotherium from the Linxia Basin, Gansu, China. Based on morphological comparison, the species of Hippotherium in China, Hippotherium weihoense and Hippotherium chiai, should be ascribed to the same species, H. weihoense. We also reviewe other Old World hipparion species in the very early Late Miocene and figure out two evolutionary routes: the Hippotherium and Cormohipparion lineages. Analysis of locomotive ability indicates that H. weihoense likely lived in an open habitat, whereas other species of Hippotherium likely lived in closed habitats. This result shows a palaeoecological pattern in the early Late Miocene in Eurasia influenced by a series of geological events as aridification of mid-latitude Asia progressed, whereas Europe and North Africa remained relatively humid. As the genus originated from East Asia, hipparion horses divided rapidly into different groups with differing functional morphology to occupy diverse niches.

Study on the mechanism of tunable ferromagnetic composites with different rare earth ions

Size-controlled Fe₃O₄ nanoparticles doped with rare earth (RE) ions (La³⁺, Ce³⁺, and Dy³⁺) varying from 15 nm to 30 nm were successful synthesized by a hydrothermal method for potential applications in the fields of biomedicine, environmental protection and magnetic memory devices. They possessed good dispersibility, adjustable particle size and nearly spherical shape. The particle grain size was uniformly distributed and showed a low degree of agglomeration in comparison with undoped Fe₃O₄ nanoparticles. The FTIR results showed that the RE elements partially replaced Fe²⁺, occupied the octahedral position, and enhanced the vibration of the Fe–O bond. The XPS study further revealed that the valence states of La, Ce, and Dy are both positive trivalent. The XPS Fe 2p valence band spectra observed a shift in the peak position toward higher binding energy after RE doping, confirming the existence of RE ions in the octahedral position. This paper explains the mechanism of rare earth doping with Fe₃O₄, and clarifies the influence of the doping of different RE ions on its magnetic properties. The detailed analysis of RE-doped ferrite materials can open a new perspective in designing biomedical and spintronics materials with tailored properties by choosing suitable cation substitution.

After doping RE elements, the corresponding M_s decreases, and the magnetization decreases with the increase of doping concentration. The RE ions were more inclined to replace some Fe²⁺ ions in the octahedral position from the VSM results.

Aeolian sediment evidence that global cooling has driven late Cenozoic stepwise aridification in central Asia

It has been a long held view that uplift of the Tibetan Plateau dominated stepwise climatic drying in central Asia during the late Cenozoic. On the other hand, global cooling may also have forced Asian drying and the subsequent formation of aeolian deposits in north China. Until now, whether the Tibetan uplift or the global cooling has been the first-order driver controlling stepwise Asian drying has remained a contentious issue. In this study, we examine the thick aeolian silt deposit, which is regarded as a good archive of palaeoclimatic changes in central Asia and north China, in order to qualitatively reconstruct the drying process in Asia during the late Cenozoic. On the basis of our long-term field surveys, laboratory analyses and previous investigations, we have obtained time sequences of Asian drying from the early Miocene to late Pleistocene; we compare this newly reconstructed time series of Asian aridification with the time series of global cooling and Tibetan uplift to identify the first-order driver of stepwise Asian aridification. A good match between the drying and global cooling might indicate that global cooling was the most likely driver of stepwise drying in interior Asia. On the other hand, controversy regarding timing and amplitude of Tibetan uplift during the late Cenozoic suggests that the prevailing conclusion that Tibetan uplift forces Asian drying should be regarded as immature. A mechanism that global cooling drove the Asian drying is tentatively suggested.

Phylogeography of Phrynocephalus erythrurus from the Qiangtang Plateau of the Tibetan Plateau

Phrynocephalus erythrurus of the Qiangtang Plateau occupies the highest regions of any reptile on earth. Here, we report mitochondrial DNA haplotypes sampled throughout the distribution of P. erythrurus and analyze patterns of genetic divergence among populations. The species diverged into two major lineages/subspecies at 3.67mya corresponding to the Northern and Southern Qiangtang Plateau. The Northern Qiangtang lineage diverged into two subpopulations at 2.76mya separated by the Beilu River Region and Wulanwula Mountains. Haplotypes from the southern Qiangtang lineage diverged 0.98mya as a star-shaped pattern. Analyses of molecular variance indicated that most of the observed genetic variation occurred among populations/regions implying long-term interruptions to gene flow. There was no evidence of sudden recent range expansions within any of the clades/lineages. NCPA infers allopatric fragmentation and restricted gene flow as the most likely mechanisms of population differentiation. Our results also indicate the presence of at least three refugia since the Hongya glaciation. Mountain movement and glaciations since mid-Pliocene are considered to have shaped phylogenetic patterns of P. erythrurus. P. erythrurus parva is suggested as a valid subspecies of P. erythrurus. Using four calibration points, we estimate an evolutionary rate of 0.762% divergence per lineage per million years for a mitochondrial genomic segment comprising the genes encoding ND2, tRNA(Trp) and tRNA(Ala).