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This special issue is to memory Professor Liu Tungsheng for his scientific contributions and his centenary birthday. Liu Tungsheng was the former President of the International Association for Quaternary Association (INQUA), and the Honorary President of the Chinese Association for Quaternary Research (CHIQUA). Liu’s best known contribution to Quaternary research is his pioneering and systematic study of the extensive loess deposits of China, which has been regarded as the best terrestrial paleoclimatic archive on the Earth. He won many international awards including the Tyler Prize for Environmental Achievement in 2002 and the Alexander von Humboldt Medal in 2007. He was an inspiring leader, one of China’s, and indeed one of the world’s most outstanding Earth scientists. This introduction aims to explore the personal factors behind his great achievements and reviews the papers included in this special issue from his colleagues, friends, and students.

Gran Canaria Island is frequently impacted by Saharan dust, a health hazard of particular concern to the island population and health agencies. Airborne mineral dust has the severest impact on the higher age groups of the population, and those with respiratory conditions; despite that, on average, the ambient particulate matter (PM) concentrations fall within international PM guidelines. During 2010 and 2011, an epidemiological survey, in parallel with an air quality study, was conducted at the Dr Negrin hospital in Gran Canaria. This included the quarterly monitoring of outpatients and recording of emergency patients with respiratory diseases, together with the measurement of aerosol, meteorological, and PM-related air quality levels. The finer more toxic particles were collected with PM2.5 (particulate matter with aerodynamic diameter less than 2.5 μm) aerosol samplers. The filter samples were gravimetrically and chemically analyzed for their elemental, water-soluble ions, carbon, and mineralogi...

Considering their distribution, thickness, and complexity around the margins of the Quaternary ice-sheets in the Northern Hemisphere, loess sequences can be considered as one of the best records of global environmental changes on the continents. European loess sequences have been intensively studied for many decades, but increasingly higher stratigraphic resolution and the availability of a growing range of climate proxy indicators has resulted in some notable advances in recent years. Climatic variability has been analyzed at high resolution, based on different proxies.

Glacioaeolian processes, sediments, and landforms are a critical component of glacial and periglacial systems. Their forms range from extensive dune systems, cover samples, thick loess successions, to thin veneers of silts and sands that drape glacial and periglacial landforms, and erosion surfaces. Glacioaeolian processes may be found in environments more distal from the glacial settings such as in the loess deposits of the United States, Western Europe, South America, and Central Asia. The glacioaeolian system involves sediment production by chemical and physical weathering of rock and abrasion of rock and sediment by transporting agents, notably glaciers, wind, and water. This is followed by sediment transfer and deposition by aeolian processes. Sediment transfer and deposition are strongly controlled by climatic perturbations; e.g., rates of glacioaeolian sediment deposition, most notably glacial loess, occur during glaciation at its height.

This paper reports on sequential aerosol sample sets collected at the Campus de Tafira, University of Las Palmas de Gran Canaria (ULPGC), in 2010. Gran Canaria is located approximately 250 km off the coast of North Africa and at the northern margin of the dominant Saharan dust plumes being blown westward across the Atlantic Ocean. PM2.5 aerosol samples were collected on 47 mm filter substrates of Teflon®, quartz fiber and Nuclepore®, generally at weekly sampling intervals. Subsets of these were analyzed for their mass, as well as elemental and ionic compositions. The 2010 annual geometric mean PM2.5 concentration at Tafira was 6.2 μg/m3, with only two particularly dusty events. From a simultaneous PM10 study at the same site, a PM2.5/PM10 mass ratio of 0.35 was calculated. Diagnostic chemical ratios for PM2.5, for both moderate and severe Saharan dust events (calimas) in 2010 are: Al : Si : K : Ti : Mn : Fe : Sr 1 : 2.818 : 0.330 : 0.078 : 0.012 : 0.847 : 0.0088 . To better understand the mineralogy of the aerosols and for inter-comparison purposes, normative mineral compositions were calculated from the chemical compositions. Depending on their transport patterns, four source regions, each with a distinct mineralogical signature were distinguished. The Northwest to North sector (Oceanic NW) aerosols contain evaporites, secondary ammonium sulfate, lesser amounts of organic carbon, and minor amounts of quartz and other silicates. The North to Northeast sector (Europe NE) generated aerosols of evaporites, ammonium sulfate and organic carbon. The Northeast (Africa NE) sector, with influx of air from the Iberian Peninsula and North Africa, contained evaporites and secondary ammonium sulfate with some organic carbon, and minor amounts of silicates and quartz. In 2010, the main African transport pathway from the Sahara region and across northern Mali, northern Mauritania, Western Sahara and Morocco was responsible for elevated concentrations of mineral dust during calima events.

La Graciosa volcanic island evolved in the late Pleistocene–Holocene. It is situated along the northeast of the Canarian Archipelago, with a subaerial surface of 27 km2. This island is located close to the Western Sahara, being 80 km from the north-western African continental shelf and 145 km from the coast. The island supports a very small permanent population. The climate is coastal-arid (116 mm precipitation per annum). Regular occurrences of Saharan dust plumes (about 30% of the year), with a dust accumulation rate of 20 g− 2 year− 1, produce sedimentation of dust on the island of ca. 540 t year− 1. Wind-blown sediments cover a large area (more than 52%) of the otherwise volcanic island, forming sandy beaches, sand sheets, nebkhas and other aeolian deposits. Re-distributed dust deposits often occur on the leeward sides of inter-volcano areas, inter-dune areas and in endorheic sediment traps. Many of these deposits are edaphized and carbonatized. Textural analysis of the dust deposit samples shows a variable proportion of silt (80–20%), clay (19–9%), and fine to very fine sand (71–4%). The general mineralogical composition of these sediments as measured by XRD and SEM-EDS is calcite (26%), illite (26%), quartz (11%), augite (10%), aragonite (6%), anorthite (8%), kaolinite (5%) and montmorillonite (3%). The mineralogy in different size fractions is very consistent; for example, quartz content decreases from 15% in the coarse silt fraction to 5% in the fine sand. A mineral and grain-size comparison with airborne dust collected on Gran Canaria Island was undertaken; close similarities were found in the two sample sets. Such closely-matched characteristics point to a similar origin for both airborne dust and dust deposits, in line with the Saharan plume dust that regularly traverses this archipelago. It is unusual to find so much quartz in the fine sand fraction of these aeolian dust deposits. Individual quartz grains with an intermediate axial length of ~ 160 μm were identified by SEM-EDS. Previous investigators have found similar “giant” particles in long-range transported aeolian dust (Middleton et al., 2001), in contrast to the classic model for gravity settling of airborne dust particles. The debate on this subject remains open for discussion. We present evidence of long-range, wind-transported large mineral particles and a 2004 case study of uplift wind velocity vs. plume dust generation, as well as a transport efficiency model that can explain the existence of fine sand in the dust deposits on La Graciosa Island and in the airborne samplers on Gran Canaria Island. Recent Saharan dust shows that about 10% of similar coarse-grained particulate matter is also present.

Global dust events have been part of much of Earth's history. As in the geological past, mineral dust deflated off weathered crustal material in arid regions is continually being lofted kilometres into the atmosphere, where it circles the globe until physical and chemical processes favour precipitation in the ocean or on land. Mineral dust aerosols affect the environment both directly and indirectly by impacting the chemical and physical properties of the atmosphere and by interfering with biogeochemical cycles, all on a global scale. The most important source regions of dust are all in the Northern Hemisphere and include North Africa, the Middle East, the northwestern Indian subcontinent, central Asia, and northwestern China.

Moraines along the southwestern slopes of the Qilian Shan were dated using cosmogenic radionuclide (CRN) surface exposure techniques to help define the timing of glaciation in northernmost Tibet. The CRN data show glaciers extending 5–10 km beyond their present positions during the global Last Glacial Maximum (LGM) and probably maintained at their maximum extent until the Lateglacial. These data help support the view that glaciers throughout Tibet and the Himalaya were maintained at or near their maximum LGM extent until the Lateglacial. An optically stimulated luminescence date of 11.8 ± 1.0 ka on silt that caps a latero-frontal moraine shows that glaciers had retreated significantly by the end of the Pleistocene and that loess was beginning to form in this region in response to the changing climate during and after the Younger Dryas Stade.

The “methane-led hypotheses” assume that gas hydrates and marine seeps are the sole geologic factors controlling Quaternary atmospheric and climate changes. Nevertheless, a wider class of geologic sources of methane exist which could have played a role in past climate changes. Beyond offshore seepage, relevant geologic emissions of methane (GEM) are from onshore seepage, including mud volcanism, microseepage and geothermal flux; altogether GEM are the second most important natural source of atmospheric methane at present. The amount of methane entering the atmosphere from onshore GEM seems to prevail on that from offshore seepage. Onshore sources inject a predominantly isotopically heavy (13C-enriched) methane into the atmosphere. They are controlled mainly by endogenic (geodynamic) processes, which induce large-scale gas flow variations over geologic and millennial time scales, and only partially by exogenic (surface) conditions, so that they are not affected by negative feedbacks. The eventual influence on atmospheric methane concentration does not necessarily require catastrophic or abrupt releases, as proposed for the “clathrate gun hypothesis”. Enhanced degassing from these sources could have contributed to the methane trends observed in the ice core records, and could explain the late Quaternary peaks of increased methane concentrations accompanied by the enrichment of isotopically heavy methane, as recently observed. This hypothesis shall be tested by means of robust multidisciplinary studies, mainly based on a series of atmospheric, biologic and geologic proxies.

This study further investigates the reported “uniqueness” of MIS 3 climatic changes in northwestern China by focusing on the MIS 3 lacustrine-wetland sequences in the western part of the Chinese Loess Plateau. The lacustrine-wetland sequence at the Suancigou section documented four major environmental changes. Stratigraphic unit (i) was formed under lake-dominated environments (48,420–35,730 14 C yr BP), unit (ii) under wetland-dominated environments (35,730–20,480 14 C yr BP), and unit (iii) under eolian-dominated environments (20,480–13,090 14 C yr BP). Unit (iv) is a fluvially-reworked eolian (loess) unit (13,090–11,450 14 C yr BP). Pollen zone A (47,210–33,370 14 C yr BP), representing a coniferous forest, corresponds to stratigraphic unit (i). Zone B (33,370–28,280 14 C yr BP), representing a coniferous woodland landscape, and zone C (28,280–22,480 14 C yr BP), representing a landscape in which coniferous woodlands alternated with steppes; correspond to unit (ii). Zone D (22,480–11,450 14 C yr BP), representing a steppe landscape, corresponds to unit (iii) and unit (iv). We propose that the extremely wet MIS 3 was a combined result of mildly high summer insolation and constantly higher-than-normal winter insolation. That is, mildly high MIS 3 summer insolation was probably able to maintain the warmth of the ocean surface to the extent so that the Tibetan Plateau and northwestern China received an adequate supply of water-vapour. A constantly higher-than-normal MIS 3 winter insolation might have shortened the duration of the winter monsoon, so lengthening the rainy season. In addition, the soil-vegetation-air coupled feedback mechanisms under extensively well-vegetated wet conditions might have further enhanced the MIS 3 wet conditions.

Natural disasters like the 2004 tsunami bear graphic testimony to the Earth's incredible power and to an obvious corollary: that effective use of geoscientific knowledge can save lives and protect property. Such knowledge also enables satisfying, in a sustainable manner, the growing need for Earth's resources by an expanding human population.

A systematic study of the last glacial cycle along three transects across the Chinese Loess Plateau shows that sand-sized particle content within loess decreases rapidly from north to south, and that markedly high sand particle contents in loess horizons occur only in the northern part of the Plateau. This suggests that variation in the sand-sized particle fraction within loess near the desert margin is closely linked to migration of the southern desert border in northern China where sand grains move mainly in saltation or modified saltation mode near the ground surface. As desert margin shift is essentially controlled by the amount of monsoon precipitation, the sand-sized particle content within loess near desert margin is regarded as a new and readily applied proxy for variations in the strength of the East-Asian summer monsoon. A continuous record of sand content in loess along the loess–desert transitional zone shows that the Mu Us Desert migrated southward at 2.6, 1.2, 0.7 and 0.2 Ma, suggesting a stepwise weakening of the East-Asian summer monsoon during the past 3.5 Ma. This evolutionary pattern is significantly different from that previously inferred from loess magnetic susceptibility records, a widely used monsoon proxy. Our results further suggest that changes in global ice volume may have been an essential factor in controlling Plio–Pleistocene monsoon evolution, and that the anticipated future melting of polar ice cover may lead to a northward migration of the monsoon rainfall belt in northern China.

Temporal and spatial changes in glacier cover throughout the Late Quaternary in Tibet and the bordering mountains are poorly defined because of the inaccessibility and vastness of the region, and the lack of numerical dating. To help reconstruct the timing and extent of glaciation throughout Tibet and the bordering mountains, we use geomorphic mapping and 10 Be cosmogenic radionuclide (CRN) surface dating in study areas in southeastern (Gonga Shan), southern (Karola Pass) and central (Western Nyainqentanggulha Shan and Tanggula Shan) Tibet, and we compare these with recently determined numerical chronologies in other parts of the plateau and its borderlands. Each of the study regions receives its precipitation mainly during the south Asian summer monsoon when it falls as snow at high altitudes. Gonga Shan receives the most precipitation (>2000 mm a −1 ) while, near the margins of monsoon influence, the Karola Pass receives moderate amounts of precipitation (500–600 mm a −1 ) and, in the interior of the plateau, little precipitation falls on the western Nyainqentanggulha Shan (∼300 mm a −1 ) and the Tanggula Shan (400–700 mm a −1 ). The higher precipitation values for the Tanggula Shan are due to strong orographic effects. In each region, at least three sets of moraines and associated landforms are preserved, providing evidence for multiple glaciations. The 10 Be CRN surface exposure dating shows that the formation of moraines in Gonga Shan occurred during the early–mid Holocene, Neoglacial and Little Ice Age, on the Karola Pass during the Lateglacial, Early Holocene and Neoglacial, in the Nyainqentanggulha Shan date during the early part of the last glacial cycle, global Last Glacial Maximum and Lateglacial, and on the Tanggula Shan during the penultimate glacial cycle and the early part of the last glacial cycle. The oldest moraine succession in each of these regions varies from the early Holocene (Gonga Shan), Lateglacial (Karola Pass), early Last Glacial (western Nyainqentanggulha Shan), and penultimate glacial cycle (Tanggula Shan). We believe that the regional patterns and timing of glaciation reflect temporal and spatial variability in the south Asian monsoon and, in particular, in regional precipitation gradients. In zones of greater aridity, the extent of glaciation has become increasingly restricted throughout the Late Quaternary leading to the preservation of old (≫100 ka) glacial landforms. In contrast, in regions that are very strongly influenced by the monsoon (≫1600 mm a −1 ), the preservation potential of pre-Lateglacial moraine successions is generally extremely poor. This is possibly because Lateglacial and Holocene glacial advances may have been more extensive than early glaciations and hence may have destroyed any landform or sedimentary evidence of earlier glaciations. Furthermore, the intense denudation, mainly by fluvial and mass movement processes, which characterize these wetter environments, results in rapid erosion and re-sedimentation of glacial and associated landforms, which also contributes to their poor preservation potential.

The field properties, magnetic susceptibility, particle size, calcium carbonate content, soil micromorphology and optical luminescence ages of the upper 6.1 m and lowermost 4.7 m of the 45 m loess-palaeosol sequence at El Lambedero in the Tafí del Valle region of Tucumán Province (Sierras Pampeanas, northwest Argentina) have been used to set up a partial stratigraphy and chronology, as well as a basic pedosedimentary model of loess accumulation, palaeosol development, reworking and erosion for the site. The minimum ages derived from the basal part of the section suggest that loess began to accumulate some time before 165 ka. A thick and well-developed pedocomplex in the upper profile is correlated with at least the latter part of marine isotope stage (MIS) 5, whereas the overlying palaeosol may be attributable to pedogenic activity during MIS 3. The absence of material younger than 33 ka close to the surface of this rounded spur landform is probably the result of either non-deposition or erosional stripping in response to climatic change, or episodic uplift in this seismically active region. © 2004 John Wiley and Sons, Ltd. Fil: Kemp, Rob A.. University of London; Reino Unido Fil: King, Matthew. Royal Holloway University of London; Reino Unido Fil: Toms, Phillip. Royal Holloway University of London; Reino Unido Fil: Derbyshire, Edward. Royal Holloway University of London; Reino Unido Fil: Sayago, Jose Manuel. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Geociencias y Medio Ambiente; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina Fil: Collantes, Mirian Mabel. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Geociencias y Medio Ambiente; Argentina

Mineral dust is an important constituent of the solid load in Earth's atmosphere, the total atmospheric aerosol loading being both a function of, and a factor affecting climatic change. Human actions have progressively enhanced atmospheric dust loading, especially in the past century, so that both natural and human-induced effects of atmospheric dust on climatic change require more detailed research. Records of changing climate are preserved in cores from the ocean floors, glaciers and ice sheets, as well as in terrestrial sedimentary sections. Quantitative data on the present-day distribution of atmospheric dust are sparse, but simulation of dust transport and deposition has been modelled with some success. The dust indicators and records of terrestrial and marine palaeoenvironments (DIRTMAP) database was designed to serve as a global validation data set for use with earth system models of the palaeo-dust cycle. Loess, a wind-borne silt deposited on the continents particularly in the past 2.6 Myr, is an important potential source of information on past atmospheric dust accumulation. A recent initiative sought to improve the terrestrial data coverage within the existing DIRTMAP database by involving representatives from key loess regions in coordinating the data synthesis process, so as to facilitate interaction between the dust modelling and the data collection communities. The results are presented in this issue. In order to compare past minerogenic dust records (loess) with those in ice and ocean cores, mass accumulation rates (MARs) have been calculated as fluxes (in g/m2/yr). The loess regions covered include North and South America, Europe, Siberia, eastern Asia, and Australasia. It is acknowledged that provision of age models for the calculation of realistic MAR values depends upon a number of conditions, most notably sound chronostratigraphy and realistic values of loess dry bulk densities. The MAR data sets presented here show some notable variation, both within and between the studied regions. Regional MAR coverage also varies, reflecting differences in the availability of key data on loess from one world region to another. Loess facies vary according to specific site and source conditions, as well as in response to post-depositional re-working of primary (wind-lain) loess by surface geomorphic processes. Mean particle size consistently declines downwind, and terrace, valley and upland sites generally yield the highest MAR values, characteristics noted in all regions discussed here. The loess accumulations in two major world regions, central and eastern Asia and the Great Plains region of North America, differ in some important respects from loess elsewhere in that they lie peripheral to deserts and are remote from the former sites of major Quaternary ice sheets. It is concluded that the MARs for terrestrial sites obtained from loess are consistently higher than those obtained from ocean and ice cores, so that future climatic models designed to study the role of global atmospheric dust will have to take full account of the present and past dust records over the continents.

The basal part of the 42-m loess–paleosol sequence at La Mesada near Tucuman in NW Argentina reported by Zinck and Sayago (J. S. Am. Earth Sci. 12 (1999) 293; Quat. Int. 78 (2001) 11) is re-examined here using a combination of micromorphology and optically stimulated luminescence (OSL) dating. Depth distributions of microstructure, clay coatings and secondary carbonate features enable the development of this part of the sequence to be reconstructed in terms of a series of pedosedimentary stages. Stage one involved accretionary pedogenesis with loess being modified by bioturbation (and possibly leaching) processes as it accumulated. Stage two was marked by a reduction in loess deposition and establishment of a relatively stable surface at which bioturbation, leaching and clay translocation processes were dominant. Stage three represented a return to accretionary pedogenesis followed by establishment of a new relatively stable surface and vertical leaching and clay translocation processes with some welding of secondary carbonate features on the underlying older soil. The three OSL dates, ranging from ca. 150 to 195 ka BP, suggest that the whole sequence is significantly older than indicated by the radiocarbon chronology ( ka BP) reported in the works of Zink and Sayago cited above. However, assuming that the pedosedimentary changes reflect alternating periods of dry-cool and moist-warm conditions as suggested in the works of Zink and Sayago cited above the succession still potentially provides the highest resolution proxy climatic record so far reported in Argentina.

The nature of fine-grained sediment production and transfer in high-altitude debris-covered glaciers was studied by examining the Rakhiot and Chungphar glaciers in the Nanga Parbat Himalaya, Northern Pakistan. Transport pathways, from the source areas to the glacier snout, were mapped and samples collected for particle size analysis and scanning electron microscopy. Positive down-glacier trends in sediment fining and increased weathering showed that debris transport in the supraglacial zone of these Himalayan glaciers is an important contributor to contemporary glacial sediment production, resulting in intense comminution that yields large volumes of fine sediment. These findings cast doubt on the traditional view that the basal traction zone of glaciers is the only major source of fine sediment production in glaciated environments, although that view may hold true for classic alpine glaciers that are at lower altitudes and, as a consequence, generally have less supraglacial debris cover. To test this hypothesis, the Glacier de Cheilon, in the Swiss Alps was also studied. This glacier did not exhibit such striking down-glacier trends in the particle size characteristics measured. It is thus suggested that a thick debris-cover may be an important source of fine-grained sediments on glaciers that occur in high-altitude environments.

The micromorphological characteristics of a continuous set of block samples from 24–38 m depth in a well section on Jiuzhoutai Mountain, Lanzhou, China, are described. The shape of the magnetic susceptibility curve, together with previously published radiocarbon, luminescence and geomagnetic dates, indicates that this sample set encompasses the whole of the last interglacial (S1) palaeosol complex, and extends into the overlying and underlying loess (L1 and L2) units. Seven pedosedimentary units are recognised on the basis of trends in the bulk properties and the key micromorphological indicators (excrements, textural concentrations, shell fragments, and calcite and gypsum features). High rates of loess deposition, with significant cryogenic activity, gypsum precipitation and only weak bioturbation, characterised Oxygen Isotope Stage (OIS) 6 and OIS 4 at Lanzhou. Depositional rates were moderately high in OIS 5d and 5b, with slightly higher bioturbation and no significant cryogenesis or gypsum precipitation. OIS 5e, 5c and 5a were marked by low rates of accretion, more extensive bioturbation and limited leaching. This reconstruction reflects the pedosedimentary responses to fluctuating dominances of monsoonal controls during this period of global climatic change. Comparison of earlier micromorphological results from sites to west and east of Lanzhou along a dry to humid climatic gradient indicate a clear regional pattern with reduced loess accumulation rates and enhanced bioturbation and leaching in the humid east (Tianshui and Xian). Clay translocation occurred only in OIS 5e at Xian, the warmest and most humid site on the transect.

The considerable morphodynamic energy provided by the continuing tectonic evolution of Asia is expressed in high erosional potentials and very high rates of sediment production that make this continent unequalled as a terrestrial source of primary silt. Many of these environments are hazardous, threatening human occupation, health and livelihood, especially in regions of dense population such as the loess lands of north China. Dry loess can sustain nearly vertical slopes, being perennially under-saturated. However, when locally saturated, it disaggregates instantaneously. Such hydrocompaction is a key process in many slope failures, made worse by an underlying mountainous terrain of low-porosity rocks. Gully erosion of loess may yield very high sediment concentrations (>60% by weight). Characteristic vertical jointing in loess influences the hydrology. Enlarged joints develop into natural sub-surface piping systems, which on collapse, produce a “loess karst” terrain. Collapsible loess up to 20 m thick is common on the western Loess Plateau. Foundation collapse and cracked walls are common, many rapid events following periods of unusually heavy monsoonal rain. Slope failure is a major engineering problem in thick loess terrain, flow-slide and spread types being common. The results are often devastating in both urban and rural areas. An associated hazard is the damming of streams by landslides. The human population increases the landslide risk in China, notably through imprudent land-use practices including careless water management. A number of environmentally related endemic diseases arise from the geochemistry of loess and its groundwaters, including fluorosis, cretinism, Kaschin–Beck Disease, Keshan Disease and goitre. The Chinese desert margins also have a major atmospheric dust problem. The effect of such dust upon human health in these extensive regions, including many large cities, has yet to be evaluated, but pneumoconiosis is thought to affect several million people in north and west China.

During one or more times throughout the Quaternary, an extensive glacier system occupied the valleys of the Nanga Parbat massif. Glacial landforms in the Astor valley provide evidence for two separate glacial advances with ice advancing more than 15 km down-valley from the present ice fronts. Elsewhere in the massif, geomorphic and sedimentological evidence provide evidence for a less extensive glaciation, where glaciers advanced no more than 12 km beyond their present positions. Intense erosion and mass movement has destroyed any depositional evidence for earlier Pleistocene glaciations. However, truncated spurs, hanging valleys, steep valley sides and over-deepened trunk valleys provide evidence of an earlier, more extensive glaciation. Small moraines near the snouts of the present glaciers provide evidence for at least three limited glacial advances that post-date the extensive valley glacier system. On the basis of geomorphology, sedimentology and relative weathering characteristics glacial landforms are correlated across the Nanga Parbat massif. Furthermore, the age of the maximum extent of valley glaciation is tentatively assigned to early in the last glacial cycle with two late Pleistocene readvances or periods of stagnation followed by three periods of limited glacial advance during the Holocene.

A micromorphologically based pedosedimentary reconstruction of a 40-m loess–palaeosol sequence from the western part of the Chinese Loess Plateau provides a sensitive proxy record of changing processes and associated environmental conditions in this region between ca. 150 000 and 10 000 yr BP. Depth functions of more traditional climate proxies, such as magnetic susceptibility, calcium carbonate content and median grain size, support the broad pattern of environmental changes inferred from the micromorphology, although the bulk properties sometimes lag behind or are out of phase with each other and do not match all the fluctuations in the micromorphological record. The reasons for the disparities are probably complex, although they partly reflect differences in response rates and sensitivities of proxies to different climate parameters, as well as genuine out-of-phase changes in strength of monsoonal climate controls. This work illustrates the sensitivity of micromorphology in detecting past environmental changes within rapidly aggrading landscapes, and emphasises the need to understand more fully the local and regional significance of bulk proxies currently used in global correlations with marine- and ice-core records. Copyright © 1999 John Wiley & Sons, Ltd.

Summary The sequence of palaeosols and intervening loess units in North China provides a sensitive, detailed record of global climatic changes over the last 2.5 million years. Although various depth functions of properties, notably magnetic susceptibility, have been successfully correlated with oxygen isotope records from the deep oceans, there is a need to improve our understanding of such proxy measures used to infer past climates. For instance, pedologists are well placed to address some of the uncertainties surrounding the origin of the enhanced magnetic susceptibility (MS) values in palaeosols, and the reconstruction of palaeoprecipitation patterns by application of MS climofunctions. There are few published field descriptions of the soils buried in the loess, and those available often fail to recognize their accretionary and polycyclic nature. Field and micromorphological techniques enable finely detailed reconstructions of the pedogenic and sedimentary signals held in both palaeosol and loess units. Micromorphology, in particular, has provided detailed environmental information on successive pedosedimentary developmental stages at several sites in the Loess Plateau of China. This approach re-focuses attention on the local, climatically sensitive mechanisms that underpin the inferred global patterns of climate.

Results of a comparative analysis of a 4-year set of monthly samples of airfall dust with samples from surface alluvial fan deposits, desert sand dunes and late Pleistocene loess and palaeosols in Gansu Province, northern China, are summarized. They suggest a qualification of the conventional view that the sand deserts were the primary single source of the Quaternary loess. It is argued that silts deflated from the surfaces of the large and numerous piedmont alluvial fans in the Hexi Corridor, Gansu, constituted a major contribution to the loess column in the western region of the Chinese Loess Plateau. The present dust fall regime in the Hexi Corridor suggests that distribution and rate of accumulation of airfall silt in the present interglacial is similar to that in parts of the Pleistocene loess record.

Over much of the western part of the Loess Plateau of north China, aeolian silts averaging 150 m in thickness drape the mountainous pre-Pleistocene bedrock. The semi-arid climate with its violent monsoonal rainstorms, and the recurrent earthquakes associated with the continuing uplift of the adjacent Tibetan Plateau, contribute to frequent and rapid failure of the loess-mantled slopes. Losses of livelihood and life are amongst the most serious in all China. Landslides in eastern Gansu total more than 40000 and affect over 27% of the total area of the Province. Accelerating population growth and associated expansion in both industry and agriculture, especially since the 1950s, has added urgency to the need to improve control and management of the landslide hazard. Several approaches to control and prevention have evolved, tailored to failure type and stage of development. Some of these are discussed, particular attention being paid to certain successful procedures employed in the control of two large landslides in the major city of Tianshui. It is suggested that these slides provide a useful model for future landslide control and prevention strategies in similar urban agglomerations in the Chinese Loess Plateau.

The Loess Plateau of North China is a key region for the study of records of Quaternary climatic change. Various techniques to abstract climatically sensitive data were first applied to the classic loess—palaeosol site at Luochuan, and current views on climatic change in Asia have been strongly moulded by results from this central part of the Loess Plateau. Data including the magnetic susceptibility, granulometry, mineralogy, geochemistry, micromorphology, fossil content, and inorganic and organic carbon content of Asian loess—palaeosol series have been used, singly and in combination, as surrogate measures of palaeoclimates to infer climatic changes with particular reference to changes in the Asian monsoon. Some of this work is reviewed and the status of a number of parameters as climatic proxies is discussed. Some lithostratigraphic sequences from which proxy measures of climate have been derived are incomplete, as shown by erosion surfaces, water-laminated zones and truncated palaeosol profiles, while others provide records of relatively low resolution. Most descriptions of Quaternary climatic changes based on studies of the loess emphasize alternations in the relative dominance of warm and moist v. cool, dry and dust-laden monsoons. Some recent studies of the much higher resolution loess—palaeosol successions on the western margins of the Loess Plateau have suggested that such changes may sometimes be out of phase, with the inference that the current climate model is too simple. Means of testing this hypothesis are proposed.

A high-resolution record of the Blake Event has been obtained from a 40 m well dug in a loess section at Jiuzhoutai in the City of Lanzhou in the western Loess Plateau of China. The paleomagnetic signal is principally carried by magnetite both in loess and paleosols. The Blake Event is located at the boundary between paleosol S1-c of the last interglacial (equivalent to MIS 5e in deep-sea records) and loess L2-2 (MIS 5d), and is characterized by a triple feature consisting of two short reversed intervals separated by a short normal interval. The directional changes are abrupt, as previously revealed in other records, and suggest geocentric dipole field behavior before, after and during the event, but not necessarily during N R or R N transitions. The age and duration of the event are estimated as between 119.97 and 114.47 kyr BP and 5.5 kyr, respectively, from thermoluminescence dating and astronomically tuned climate stratigraphy based on high-resolution magnetic susceptibility.

The quality of the loess magnetic susceptibility (MS) record as a climate proxy has been compared to the ice core and deep-sea records, yet the source and causes of the MS signal remain poorly understood. Four explanations are currently in circulation. The dominant hypothesis, that MS variations largely result from post-depositional weathering and/or formation of magnetic phases by pedogenic processes, has led to the use of MS data as a palaeoprecipitation proxy. We present a different view based on analyses of samples of monthly dust falls over 4 years in North China. These have MS values comparable to those of Pleistocene loess and palaeosols but, unlike the latter, their variations are seasonal and so cannot be explained by weathering differences. Our experiments confirm that MS enhancement in the palaeosols is caused principally by fine-grain magnetic minerals, but, in contrast with previous proposals, the major source of the ultrafine magnetic minerals appears to be decomposed plant litter.

The S1 pedocomplex, correlated to Oxygen Isotope Stage 5 of the ocean cores, has been traced west of the Loess Plateau on to the extreme northeastern margin of the Qinghai-Xizang (Tibetan) Plateau in China. Detailed micromorphological analysis of closely spaced thinsections from the pedocomplex at this site provides the basis for reconstruction of the sequence of pedosedimentary processes and associated palaeoenvironmental changes occurring during this time interval. The six pedosedimentary stages identified are interpreted in terms of temporal variations in depositional rates, size of particles transported and availability of moisture for pedogenic alteration, as determined by changing balances in dominance of winter and summer monsoonal forces. Two main ‘soil-forming intervals’ are identified: the more extensive of the two in terms of resultant pedological features reflects pedogenic alteration at a relatively ‘stable’ land surface under a semi-arid climate during the later part of pedosedimentary stage 2. The other main period corresponds to pedosedimentary stages 4 and 5, when leaching and bioturbation processes were active at aggrading surfaces, leading to development of an accretionary unit without clear differentiation of horizons. Pedosedimentary stages 1, 3 and 6 were characterised mainly by rapid rates of coarse loess accumulation, with synsedimentary modification restricted to surface slaking and crust formation, and minor localised redistribution of calcite.

Opinions on the extent and style of the Quaternary glaciations of the Karakoram and northwest Himalaya have ranged from restricted alpine-style glaciation to extensive inundation by montane ice caps, to overwhelming by sheet ice from the Qinghai-Xizang (Tibet) Plateau. The sedimentological and geomorphological evidence underpinning these contrasting opinions is used to integrate the sedimentary record with what is known about uplift and incision rates and broad-scale changes in the regional climate. By reference to the independent record of monsoon-versuswesterly strength provided by the lacustrine and loess record of central and east Asia, increasing relative relief and topographical discordance are considered as influences upon glaciation style, glacier extents, and sediment budgets since the Middle Pleistocene. Ice extent may have progressively declined with increasing constraints on glaciation limits through time, but total ice volumes during glaciations may have shown less variation as valley systems enlarged in conditions of quasi-balance between uplift and incision.

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.

This paper presents the first glacial chronology for the Lahul Himalaya, Northern India. The oldest glaciation, the Chandra Glacial Stage, is represented by glacially eroded benches at altitudes greater than 4300 m above sea-level. This glaciation was probably of a broad valley type. The second glaciation, the Batal Glacial Stage, is represented by highly weathered and dissected lateral moraines, which are present along the Chandra valley and some of its tributaries. This was an extensive valley glaciation. The third major glaciation, the Kulti Glacial Stage, is represented by well-preserved moraines in the main tributary valleys of the Chandra valley. This represents a less extensive valley glaciation. Two minor glacial advances, the Sonapani I and II, are represented by small sharp-crested moraines, which are within a few hundred metres or few kilometres of the present-day glaciers. The change in style and extent of glaciation is attributed to an increase in aridity throughout the Quaternary, due either to global climatic change or uplift of the Pir Panjal mountains to the south of Lahul, which restricted the northward penetration of the south Asian summer monsoon. © 1996 John Wiley & Sons, Ltd.

In his 1990 paper (Catena, 17: 175–183), Jan de Ploey proposed a system whereby catchments are viewed as functional units in which geomorphic work results from the combined effects of water erosion and mass movements. His measure of erosional susceptibility of catchments, ES, introduced the gravitational potential in addition to the kinetic energy of the eroding agents. This modelling of the erosional susceptibility of catchments in terms of energy was being used to explore time-dependent variations of ES when Jan de Ploey died. Also at this time, he extended an invitation to the present authors to test and extend his model using our data base on the landslide-dominated catchments in the thick loess country of north-central China. This paper presents a series of new equations expressing variations in ES using a data base for over 200 landslides in the loess-covered mountainous terrain (relative relief up to 1500 m) of the Lanzhou region of eastern Gansu Province. These equations express the loss of potential energy of the landslide mass in relation to the relative relief and the pressure energy input in the form of rainfall. These indices of erosional susceptibility can be used to analyse the differences in response, from one catchment to another and through time, between the characteristics of vegetation cover including land use, hydrology, geomechanical behaviour, and mechanisms of movement on slopes. Using certain assumptions on percentage area of catchments affected by mass movement and long-term mean annual precipitation in the Lanzhou region, the Es equation suggests an estimate for non-clayey materials of about 10−4 m−2/s−2, which is a significantly higher susceptibility value than the mean worldwide value for non clayey materials obtained by De Ploey.

New data are presented on micromorphology, magnetic susceptibility and particle size characteristics of three soil/sediment units at four locations along a WNW-ESE transect across the Loess Plateau of North China. Differences and spatial trends are used to assess the sensitivity of such data as proxies of regional palaeoclimatic gradients. The steepest climatic gradient suggested by the magnetic susceptibility for the S1 palaeosol is at the eastern (humid) end of the traverse. Micromorphology and particle size analysis show that the loess units in the east are richer in clay than the best developed palaeosols in the semi-arid west, and that particle size in the west appears to provide a more sensitive record of climatically-driven changes than magnetic susceptibility. The use of surface and near-surface soils as a datum for inferring palaeoprecipitation values is reviewed in the light of recent evidence of substantial degradation of such soils. Micromorphological and particle size analysis of closely spaced samples from loess-palaeosol sequences is a sensitive addition to magnetic susceptibility stratigraphy and correlation.

Fine atmospheric dust (including fine mineral aggregates, fibrous minerals, and fibrous organic materials) reaches concentrations in many parts of the world sufficient to constitute a major influence upon both human and animal health.

The seismic refraction reversed profiling technique has been used to investigate the topography of the last interglacial soil (paleosol S1) within the central Chinese Loess Plateau near Xifeng. The results suggest an essentially flat-lying soil at a depth which varies by only a few meters over an area of more than 10 km2. In addition, the results indicate a high-velocity layer at 50-60 m depth which is thought to coincide with a layer of carbonate concretions at the base of paleosol S5. The results agree well with the local loess-paleosol stratigraphy for this area and indicate that the seismic refraction method is a rapid technique for investigating paleotopography.

The 35.5 m thick loess section at Beiyuan in Gansu Province, China provides the most detailed record on the Loess Plateau of the periodicities in earth orbital changes during and since the last interglacial. It contains ten paleosols, one of which is in the Holocene loess, four in the Malan loess and five in the upper Lishi loess and associated alluvium. Micromorphological study of the S1 paleosol series indicates that all of the component soils were subjected to moderate carbonate leaching and biological activity. Paleosols S1-c, S1-d and S1-e developed in alluvium over a time interval equivalent to stage 5e of the deep-sea core V28–238. Alluvial deposition was episodic as evidenced by the separation of the paleosols. Since the development of S1-c, the terrace has not been affected by floods and has received only wind-blow dust additions. The SBC index, a ratio of the content of channels and excrements to the content of primary calcite grains, appears to be a sensitive indicator of environmental change between the arid and sub-humid environments represented by the loess and paleosols, respectively. The trends, periodicities and amplitudes of environmental change revealed by the SBC ratio are in good agreement with those derived from other indices through the Beiyuan section and with records from other parts of the world.

A loess section near Lanzhou, China, has been investigated using the seismic refraction technique. The results show that the method is able to discriminate four distinct seismic boundaries within the section as well as indicating that the loess-bedrock contact occurs at a depth of more than 200 m. A 30 m deep pit was subsequently dug and revealed that the first two seismic boundaries correspond to soil units Sa (an intermediate soil within loess unit L1) and S1 (the last interglacial soil at the base of L1). These results, though preliminary, indicate the potential of the technique not only for mapping loess-bedrock contacts but also for determining the finer subsurface detail of the loess-palaeosol stratigraphy.

The landslides in the lœss terrain of Gansu Province are a major and recurrent natural hazard in a region with a rapidly rising population which occupies all available space in the landscape. The landslides result from the combination of a climate characterised by irregular monsoonal rains which include high intensity showers, strong seismic activity, steep, montainous topography and the metastability of the lœss. Cultivation on the slopes enhances surface runoff and, in consequence, accelerates infiltration of meteoric waters into a network of pipes making up the "lœss karst". Water becomes concentrated close to the lœss-bedrock contact, inducing saturation and liquefaction which create flow slide type failure at depth as an essential condition for simultaneous failure of the whole slope., Les glissements de terrain qui affectent les lœss de la province de Gansou constituent un risque naturel majeur et récurrent dans une région dont la population croît et utilise tout l'espace disponible. Ils sont dus à la combinaison d'un climat à pluies de mousson irrégulières à averses de forte intensité, d'une sismicité très active, d'un relief accidenté à pentes raides et fortes dénivellations, ainsi qu'aux propriétés spécifiques du lœss qui est un matériau métastable. La mise en culture des pentes accroît le ruissellement de surface et accélère en conséquence l'infiltration des eaux dans un réseau de conduits qui forme le pseudokarst du lœss. Les eaux se concentrent préférentiellement au contact du lœss et du substrat rocheux, provoquant la saturation et la liquéfaction du matériau et déclenchant en profondeur des mouvements de type «flow slides » qui entraînent l'effondrement simultané de la totalité du versant., Billard Armelle, Muxart Tatiana, Derbyshire Edward, Egels Yves, Kasser Michel, Wang Jingtaï. Glissements de terrain induits par les pluies dans les lœss de la Province de Gansou, Chine . In: Annales de Géographie, t. 101, n°567, 1992. pp. 520-540.