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A large variety of geological evidence are presented and summarized here to address the links between the geological environments in China and global environmental changes in the Cenozoic era. Environmental indicators (coal beds, salt and gypsum deposits, palaeo-vegetation remains etc.) from the presently monsoonal regions provide the first terrestrial evidences of the inceptions of the Southeast Asian summer monsoon, the Southwest Asian summer monsoon and the Northwest Asian winter monsoon. The Palaeocenc and the Eocene environmental pattern in China was dominated by roughly zonal climates resulted from the planetary wind system. The decrease in the aridity for the southeastern country in the Oligocene indicates the inception of the southeast summer monsoon. Conspicuous changes have occurred for the Miocene when the originally arid south-western part of the country became much more humid, indicating the initiation of the south-west summer monsoon. The south-east summer monsoon was also significantly strengthened at the same time. The geographic location of the arid region in northern China was further close to the present-day one, suggesting that the Himalayans and the Tibetan Plateau may have began to uplift. These were also more or less synchronous with the rapid growth of the Antarctic ice-sheet. Another drastic change occurred around the latest Miocene when extensive aeolian dust began to deposit in the northern China, indicating the emergence of the north-east winter monsoon andan increase in the continental aridity in central Asia. Since then, a stepwise increase of continental aridity in northern China was observed for the last 2.5 Ma as shown by the loess-palaeosol sequences.

In 1935, a terrible disease was spreading wantonly in some rural areas of Heilongjiang province in northeastern China. Women of childbearing age and children were its primary victims. Particularly cruel, the disease frequently occurred without warning and led to the death of a large number of people. At the time, nobody understood the cause of this disease, so it was called “Keshan disease” because it was first reported in Keshan County of Heilongjiang province. Today, Keshan disease is known to be an endemic myocardial disease [affecting heart muscle]. It still occurs in some rural areas. The idea that environmental selenium deficiency could be the cause of Keshan disease came about as the result of the discovery of a special ecological phenomenon in the Keshan disease region. In the summer of 1967, my colleagues and I went to Heilongjiang province to investigate the geological and geochemical environment of the disease districts.

Profound archaeological transformations that mark the collapse of Neolithic Cultures around Central China during the late third millennium BC have been identified widely. However, the causes for their collapse have been disputed. In this paper, paleoclimatic data are synthesized to show that an interval of severe climatic anomalies occurred across much of China, which were synchronous with a climatic event identified at least in the Northern Hemisphere. Our syntheses also indicate that this climatic interval was not only one of several climatic events during the Holocene, but marked the middle Holocene climatic transition (the ending of Holocene optimum). Based on geological evidences and analysis of relationships between variations in the intensity of the East Asian monsoon and changes in distributional pattern of monsoon-related rain belts in eastern China, we suggest that this climatic anomaly was superimposed on the middle Holocene transition and significantly altered the hydrological regime. This generated an environmental framework of drought in the north and flooding in the south of China, which was mainly responsible for the collapse of Neolithic Cultures around the Central Plain.

Eighty-one samples were selected from the Late Pleistocene Xifeng loess profile and analyzed for their element abundances using instrumental neutron activation analysis, and for10Be using the AMS method. The results show that the variations of element abundance and10Be with depth are similar to those of δ18O in DSDP, and may be considered as an indicator of climatic and environmental changes.

and Xian) was covered by an open meadow steppe with the presence of some coniferous species, while the middle part of the plateau (Luochuan) was covered by steppe. Our results do not support the notion that dense forest cover had developed on the Loess Plateau during the Holocene. Copyright 0 1996 Elsevier Science Ltd

The thick deposits of Quaternary gravels found along the margins of the Qinghai-Xizang (Tibet) Plateau have been studied for decades. Here, we concentrate on two sediment series widely developed along the Kunlun, Tian Shan and Qilian mountains: the Xiyu Formation, a molassic series of Lower Pleistocene age, and the Middle and Upper Pleistocene Gobi Gravels. These two series, with their contained fossil assemblages, throw light on the question of the mean altitudes and uplift rates of the Tibetan Plateau during the Quaternary and on the related problem of the vigour and penetration of advected summer monsoonal moisture into central Asia. The sedimentary series on the northern piedmonts of the Tibetan Plateau considered here challege the view that Plateau uplift accelerated in the Upper Pleistocene. They indicate that the Plateau had reached mean altitudes in the range 4000–5000 m perhaps by the end of the Lower Pleistocene, and certainly by the Middle Pleistocene. This diminished the incursion of southerly monsoonal moisture, and so imposed arid and semi-arid conditions across much of a vast region north of the Plateau which, among other effects, precluded widespread mountain glaciation in the Lower Pleistocene and general (ice sheet) glaciation of the Tibetan Plateau as a whole.

In the Loess Plateau and adjacent areas, the present summer climate is controlled largely by the warm-moist southeast monsoon with its source in the low-latitude oceans, whereas the cold-dry northwest monsoon from Siberia is predominant in winter. In this study, we use the magnetic susceptibility record of the Xifeng loess section and the grain size profile of the Baoji section as indicators of summer and winter monsoon variations, respectively. The two loess sections have a palaeomagnetic basal age of about 2.5 Ma with a total thickness of 155–170 m. Magnetic susceptibility and grain size were measured at 10–20 cm intervals. Comparison of these monsoon proxies with the oxygen isotope record of DSDP Site 607 shows that summer and winter monsoon variations closely match the global ice volume changes over the past 2.5 Ma. During glacial periods, the winter monsoon was enhanced with a significant southward retreat of the summer monsoon, as indicated by an increase in loess grain size and a decrease in magnetic susceptibility. This sequence was reversed during interglacial periods, suggesting that the ice sheet cycle in high-latitudes was an important factor controlling monsoon variations. Detailed comparison also shows that coupling of long-term monsoon change with the global ice volume sequence shows a stepwise pattern over the past 2.5 Ma. Two critical time periods, one at about 2.5 Ma and the other around 0.9–0.55 Ma, have been noted. At about 2.5 Ma B.P., loess deposition began on an extensive scale across northern China. This marked the initiation or intensification of the winter monsoon circulation which coincided approximately with the onset of continental glaciation in the northern Hemisphere. From 2.5 to about 0.9–0.55 Ma B.P., visual examination indicates the importance of a direct component of orbital forcing, besides an obvious ice forcing component. Since 0.9–0.55 Ma B.P., the ice forcing component has become the most important one. This implies that the coupling relationship is more apparent after 0.9–0.55 Ma B.P. than earlier. We speculate that the stepwise coupling mechanism between the monsoon circulations and global ice volume may be associated with the stepwise uplift of the Tibetan Plateau.

Summary The pedostratigraphy and magnetostratigraphy of several sections in the Loess Plateau of north-central China have been investigated and correlated. The most complete and distinct loess-paleosol sequence occurs in the Baoji section of the southern part of the Plateau. Thirty seven pedostratigraphic units are identifiable in the Baoji section and correlated with those in other parts of the Plateau. The sequence represents thirty seven major cold to warm climatic cycles in the last 2.5 Myr. At about the time of the Matuyama-Gauss magnetic reversal an abrupt climatic event occurred in north China, represented by the shift of the well weathered Red Clay formation below the M/G boundary to the alternating loess and paleosol units above, marking the beginning of a new epoch in the course of climatic evolution. In addition there are two other major shifts of dominant periods of climatic cycles recorded in the loess-paleosol sequences, one occurring at about 1.5 Myr and another at about 0.8 Myr. The pedostratigraphy of loess deposits in north-central China provides an independent measure of the world-wide climatic fluctuations and is now the most complete and reliable record of the major climatic cycles in the last 2.5 Myr.

Magnetic Susceptibility measurements were conducted at 10 cm intervals in the Baoji section, a 160 m thick loess deposit in the southern Loess Plateau. An independent time scale was developed under control of paleomagnetic data by assuming that the eolian dust deposition rate during glacial periods is 1.5 times higher than that during interglacial periods. The 1600 susceptibility results were then plotted to the time scale which has a basal age of 2.5 Ma based on paleomagnetic measurements. Fourier analysis of the susceptibility time series shows strong spectral peaks centered at about 400,000, 100,000, 40,000 and 20,000 years, coinciding with the Milankovitch periods of paleoclimate. The dominant climatic periodicity recorded in the loess section appears as a function of the time interval considered: the 0–0.8 Ma interval is dominated by the period of about 100,000 years, the 0.8–1.6 Ma interval by 40,000 year cycles and the 1.6–2.5 Ma interval also by 100,000 year rhythms.

The somewhat abrupt commencement of loess deposition on a large scale in north-central China is palaeomagnetically measured at about 2.5 Ma. The formation of the dynamical conditions responsible for windblown loess processes implies a reorganization of the atmospheric circulation over eastern Asia. It is speculated that at that time, the accelerated uplift of the Tibetan Plateau had reached a threshold height, giving rise to the intensification and northward shift of the Siberian high and deepening of the cyclone in the lee of the Tibetan Plateau. The uplift of Tibet and the resulting reorganization of atmospheric circulation at about 2.5 Ma would initiate a coupled environmental system: Tibetan Plateau-inland desert-Loess Plateau in eastern Asia that could be a key system in understanding the onset of glaciation in Northern Hemisphere and climatic change in the Quaternary. The climatic shift from near-continuous warm condition before 2.5 Ma to frequent and chaotic fluctuations after is speculated to be triggered to a significant extent by the uplift of the Tibetan Plateau. An orography-cold surge-albedo-temperature feedback mechanism is developed in explaining the harsher climate over East Asia during glacial time and is thought to be one of the major contributors in promoting glacial development on the globe.

We report a first series of10Be measurements on Chinese loess covering the last 750,000 years. The10Be concentration shows a tendency to decrease with increasing grain size. Leaching experiments with acid solutions show that10Be is strongly bound to particles and therefore mobility due to dissolution can be excluded. The10Be record in loess shows features similar to those observed inδ180 records from deep-sea sediments which strongly reflect climatic variations. This allows one to correlate the10Be loess records withδ180 deep-sea records and to establish a time scale. Based on this time scale, accumulation rates of loess and10Be fluxes can be calculated. These reveal generally higher values for cold, arid and windy periods than for warm, humid and calmer intervals.

The Baoji section is judged to be the most complete pedostratigraphic section on the Loess Plateau of north-central China. It is located about 5 km north of the city of Baoji and consists of 37 paleosols formed during more than the last 2.5 Ma. It is designated here as the type pedostratigraphic section with formally named geosols following the rules of the North American Commission on Stratigraphic Nomenclature. Geochronological control is based largely on magnetostratigraphy with the Brunhes, Matuyama and Gauss epochs, and Jaramillo and Olduvai events clearly recognized. The Baoji geosols can be correlated with equivalent pedostratigraphic units throughout the Loess Plateau by a combination of magnetostratigraphy and character, position and the association of the pedostratigraphic units within the Quaternary succession. The variation of the geosols suggests climatic cycles of varying intensity and duration; but generally warmer and moister conditions when compared with the loess units that suggest colder and drier periods.

Chronological and climatic signification of laminated speleothems in North China. Speleothems from North China show that many of them have very fine micro-layer growth. Most of these layers have bi-optical characters that can be observed under fluorescent and transmitted light. Hydrological analysis and radio-isotopic dating demonstrate that those layers are annually laminated. A Holocene stalagmite from Shihua Cave in Southwest Beijing presents thousands of micro-layers which are very similar to tree rings. Based on the measurements of the thickness of annual layers, short-term climatic changes over the last 1,130 years in the Beijing area are discussed., De nombreux spéléothèmes de Chine septentrionale présentent des micro-lamines d'accroissement. La plupart de ces lamines possèdent des caractéristiques bi-optiques, observables en lumière fluorescente ou transmise. Les analyses hydrologiques et les datations radio-isotopiques démontrent que ces lamines sont annuelles. Une stalagmite holocène de la grotte Shihua, localisée au sud-ouest de Beijing, présente des milliers de lamines qui sont très similaires aux cernes de croissance des arbres. Les mesures d'épaisseur des lamines annuelles permettent de connaître les changements climatiques à court terme dans la région de Beijing pour les 1 130 dernières années., Ming Tan, Tungsheng Liu, Xiaoguang Qin, Xianfeng Wang. Signification chrono-climatique de spéléothèmes laminés de Chine du Nord . In: Karstologia : revue de karstologie et de spéléologie physique, n°32, 2e semestre 1998. Grottes ornées de Bornéo (E Kalimantan) et Grotte de Blue Lagoon (Afrique du Sud) pp. 1-6.