Qiang Xiaoke

Multiple expansions of C4 plant biomass in East Asia since 7 Ma coupled with strengthened monsoon circulation

The expansion of plants using the C4 photosynthetic pathway is one of the most prominent changes in the global ecosystem during the Cenozoic Era. A significant late Miocene expansion is well documented. However, the existence and cause of subsequent expansions are still not clear, owing in part to the lack of long, continuous climate-vegetation records. Here we present two high-resolution carbon isotope time series, covering the past 7 m.y., derived from eolian deposits on the Chinese Loess Plateau. The data indicate three intervals of significant C4 plant expansions within the semiarid monsoonal region of East Asia (ca. 2.9–2.7 Ma, 1.3–0.9 Ma, and 0.6 Ma–present). These expansions covary with strengthened East Asian summer monsoon circulation. We conclude that in East Asia, large-scale late Miocene C4/C3 vegetation changes in semiarid areas have been primarily driven by warm seasonal precipitation and temperature variations associated with changes in monsoon circulation.

The Causes of Fluvial Terraces Inland and Its Implication

Terraces in tectonically active mountains and uplands record both tectonic uplift and climatic changes. The author discusses the methods of how to distinguish the role of both tectonic and climatic factors. Fluvial system in inland is a process of reaction between aggradation and incision controlled by tectonic movement or climate changes. Through studying the cause of formation of terrace, point out that climate-controlled terrace mainly deposits in the glacial period, and incises during glacial-interglacial transition. Incision of tectonic-controlled terrace takes place in active phase. At the same time, the palaeo- channel begins abandoning. People can determinate the cause of terraces through geology features analysis and contrast them with others that were put forward before. Every one of climate- caused terraces reveals that there is/are one/several glacial to interglacial cycle(s), the gravel interbedded with slope deposition, the declining terraces bottom; while every one of tectonic-caused terraces implies that there is a tectonic event during its formation. Some terraces result from both tectonic movements and climate changes.

Magnetostratigraphy study on the Miocene sediments of Suerkal Basin, Altyn Tagh and its significance

The Altyn Tagh fault is the northernmost controlling boundary of the Tibetan Plateau, which plays an important role in growth of the Tibetan Plateau. We carried out integrated research on Cenozoic stratigraphic sections in the intermontane basin of the Alty Tagh. Existing biostratigraphic data, and magnetostratigraphic analysis were used to establish chronostratigraphy, whereas composition of sandstone and coarse clastic sedimentary rocks was used to determine the unlift history of the source region. Much of the detrital grains in our measured sections can be correlated with uplifted of the surrounding mountains, implying a temporal link between sedimentation and deformation. The results of our studies, together with existing uplift period of the Kunlun Mountains, suggest that uplifting events started about 18Ma in northern Tibet. KeywordsThe Altyn Tagh fault; Magnetostratigraphy; Suerkal Basin; Lithology; stratigraphy

Two quantitative methods of studying Orogenic belt uplift and denudation through basin-range sedimentary coupling

Intensive uplifting of mountains has great impact on the changes of climate and environment, the uplift and denudation process of orogenic belts have been a major problem in geosciences studies. The sediment basin adjacent to mountains had truthfully recorded plentiful information about the uplift and denudation process of orogenic belts. Therefore, the history of uplift and denudation process of orogenic belts could be reconstructed by using basin-range sedimentary coupling theory. In this context, two quantitative methods were introduced to reconstruct the uplift and denudation process of orogenic belts. The uplift and denudation process of orogenic belts has been a major problem in geosciences studies. Uplift of Orogenic belt is not only the exterior presentation of locomotion from interior lithosphere of the earth, but also one of the important driving forces for great changes of geographic and ecological environment. The tremendous geomorphic diversity and ecological environmental effect caused by uplift of Orogenic belt have been widely concerned. The Late Cenozoic intensive uplift of Qinghai-Tibet Plateau has greatly influenced the physiographic pattern, atmospheric circulation and anthropic living environment (1-4). Here, many methods, such as paleomorphology, paleontology, palaeoclimate, thermochronology and cosmogenic radionuclide, have played an important role and obtained many great achievements (5-10). These methods generally study the uplift process of orogenic belts directly bymountains and orogenic belts themselves or deduce the uplift rate and range of mountains indirectly by paleontology and palaeoclimatic controlled eolian loess-paleosol sequences. During the last twenty years, Scholars both home and abroad have carried out plentiful investigations on the uplift of the Tibetan Plateau (11-12). Based on the high-resolution geomagnetic polarity time scale, many paleoclimatic proxies, such as the spatio-temporal variation of grain size, mineral components and sedimentary rate, obtained from the detrital sediment sequences in basins. All these proxies were used to reconstruct the uplift process, and affirmably indicated the regional structure, especially the orogenic belt uplift and its influence on the environmental evolution. These achievements produced a marked effect on sedimentary basin-orogenic belt systems researches, and promoted the research of uplift of mountains. However, the quantification researches of uplift rate, range and dimensions of orogenic belt should go further. In the studies, we have noticed that the study of thermal history on basement rock or sediment stratum in the