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A total of 71 floodplain sediments were collected from the mainstream and major tributaries of the Changjiang for heavy mineral examinations. The upper Changjiang samples contain more heavy minerals in the very fine sand fraction than the middle-lower samples which are relatively enriched in polygenetic heavy minerals. The heavy mineral assemblages are characterized by Fe–Ti oxide minerals, calcic amphibole, epidote, garnet, biotite, and zircon, which exhibit large variations in percent between different tributaries and the mainstream. The widely distributed granitoids and Permian Emeishan Basalt in the drainage basins account for the high contents of zircon and hypersthene in the Xiangjiang and Daduhe samples, respectively. Most of the detrital magnetite grains are homogeneous in typomorphic feature and almost stoichiometric in chemical composition. The discrimination plot of TiO2 + V2O3 versus MgO/(MgO + Al2O3) suggests that most of the detrital magnetite grains are sourced from felsic plutonic/volcanic and metamorphic parent rocks, and those from different tributaries have distinct chemical compositions. Our study suggests that the combination of transparent heavy mineral assemblages and varietal study of individual heavy minerals sheds new light on the provenance discrimination of the Changjiang sediments and contributes to the mineralogical determination of ancient source rocks within a large drainage basin, despite the sediment recycling and complex source rock types.

The stiff clays beneath Holocene strata in the Yangtze Delta are interpreted as palaeosols, based on pedogenic features including illuvial argillans, voids, cracks, iron–manganese concretions and nodules, and carbonate materials. Variations in clay content with depth, the occurrence of foraminifera, and the environmental magnetism characteristics of the palaeosols suggest that their parent materials are floodplain deposits. Anisotropy of magnetic susceptibility (AMS) parameters of the sediments correlate well both with sedimentary dynamics and depositional processes in different sedimentary environments, and AMS analysis may be a useful tool for inferring sedimentary environments. Based on their considerable thickness (> 3.0 m), vertical changes of palaeosol maturity, and occurrence of ageing argillans throughout the palaeosols, the palaeosols are inferred to be compound ones (pedocomplexes) resulting from alternating deposition and pedogenesis on the palaeointerfluve of the Yangtze River. Phytoliths in the palaeosols indicate that climates turned generally from warm and wet to cold and dry with marked fluctuations during development of the palaeosols. This suggests that the palaeosols developed mainly during the marine regression prior to the last glacial maximum. The vertical distribution of manganese materials (e.g., concretions, nodules, speckles and mottles) in the palaeosols suggests that the groundwater tables were about 2.0–3.0 m beneath the upper boundary of the palaeosols during their development. Yellow–brown streaks and speckles are abundant from the middle to lower parts of the palaeosols, and layers with high CaCO 3 content occur in the strata just beneath the palaeosols, but which lack caliche, suggesting that the groundwater table fluctuated markedly during their development. Voids and cracks filled with clays, and carbonate nodules (less than 0.1 mm in diameter) with thin iron–manganese rims are abundant in the palaeosols, indicating that wet and dry seasons were marked during the palaeosol development. It is suggested that the monsoonal influence was marked in the Yangtze Delta, with both winter and summer monsoons strongly developed during the development of the late Quaternary palaeosols.

The question of the Yangtze’s origins has been extensively researched by geologists and geomorphologists for more than a century, and a widely-accepted answer is still pending. Evidence of river piracy, diversion and incision in the upper river segment from Shigu town in Yunnan Province to Yichang City has been used to reconstruct the history of the Yangtze drainage system, and constrain the timing of the upper Yangtze diversion from south flowing to east, debouching into the East China Sea. There is much diversity in fluvial deposits and landforms even over small spatio-temporal scales in tectonic highly active regions. They are also liable to latter reworking by external forces, making their paleo-geographical interpretation a more complex and controversial matter. Based on evidence from fluvial strata and landforms, various hypotheses have been proposed with considerable discrepancies for the timing of the Jinsha River diversion from the south flowing into the east, and the timing of the upper Yangtze channeling through the Three Gorges area. The Yangtze was controversially assumed to be: (1) a very old river in existence since the Cretaceous and earlier, (2) a very young river that came into being only during the past several hundred thousand years, or (3) any age in between these two extremes.

Core from a continuous borehole in the Changjiang Delta to a depth of 318.7 m dated back to the Pliocene (>3.58 Ma) and was selected for geochemical measurements and determinations of Th–U–Pb ages of monazite, in order to investigate the changing sediment provenance and development history of the Changjiang River. Geochemical proxies including fractionation parameters of rare earth elements (cerium and europium anomalies) and elemental ratios Cr/Th, Nb/Co and Th/Co suggest that the Pliocene and Quaternary sediments have remarkably different provenances. Six peak ages of monazite grains dated at

Three deep drill holes with depth exceeding 300 m were collected from eastern China for geochemical study in order to reconstruct Late Cenozoic palaeoenvironmental changes. The Late Cenozoic strata in eastern China are predominantly composed of lacustrine, fluvial and littoral sediments. Degrees of chemical weathering during the Late Cenozoic were estimated by using geochemical proxies including CaCO3 contents, chemical index of alteration and Al2O3–CaO–(Na2O+K2O) diagrams. The results show that chemical weathering was intense in eastern China in the Late Neogene, and progressively weakened during the Quaternary, albeit with amplified fluctuations. Although the palaeoclimatic conditions reconstructed from the drill holes in eastern China are generally comparable with those records from the loess–palaeosol sequences, red clay, and deep-sea sediments in East Asia, they changed asynchronously in north-central and southeast China during the Neogene. The Late Neogene palaeoclimate was overall warmer in southeast China than on the North China Plain except for some extreme cooling periods in the Late Pleistocene. In contrast, the North China Plain experienced moderate to weak chemical weathering with the intensification of East Asian winter monsoon activities during the Late Quaternary. Regional differentiation of palaeoclimatic variability since the Pliocene in eastern China is comparable with today’s climate regimes in the Changjiang and Huanghe drainage basins but with different intensities, suggesting different impacts of the East Asian palaeomonsoon during the Late Cenozoic. D 2005 Elsevier B.V. All rights reserved.

Tonglu rhythmites (Upper Ordovician) in Zhejiang Province, east-central China, display three orders of cyclicity in sandstone and mudstone layer thickness. Millimeter-thick alternations of sandstone and mudstone laminae are ascribed to single tidal cycles. Centimeter-thick alternations of sand-dominated layers (SDLs) and mud-dominated layers (MDLs) are interpreted to be related to alternation of storm and calm weather conditions with a periodicity longer than that forced by neap-spring tidal cyclicity. The SDLs are interpreted as storm deposits on the basis of presence of scour structures, abundant intraformational mud pebbles, oscillation ripples, and thinning-upward trends in the sandstone laminae. A third, meter-thick cycle of variations in sandstone-lamina thickness is interpreted as a reflection of cross-shore changes in coastal dynamics and water depth in the subtidal-intertidal environment. Storm waves, usually considered to be random destructive factors to normal cyclic deposits, are here highlighted as effective agents of sediment transport and deposition of the sand-dominated layers. This study aims at improving our facies-level understanding of the genesis and preservation of storm-related tidal-flat rhythmites on open coasts, and highlights the fact that storm related facies can mimic the cyclicity that is commonly ascribed to neap-spring tidal variation.

The Volga Delta developed in the closed Caspian basin can be classified as a river-dominated type. The subaqueous part of the delta (avandelta) is characterized by an extremely gentle slope and may be subdivided into shallow and deep parts. The very low-angle slope of the shallow avandelta is a major factor to mitigate impacts of Caspian sealevel (CSL) changes on the Volga Delta during the last 100 years. The CSL has fluctuated 3.46 m in the last 100 years, with a high of −25.55 m relative to the Baku Datum (BD) in 1903 and a low of −29.01 m BD in 1977. Sea-level changes can be grouped into three stages: (1) slowly falling at an average rate of 1.1 cm yr−1 in 1900–1929; (2) rapidly falling at an average rate of 6.3 cm yr−1 in 1930–1977; (3) rapidly rising at an average rate of 8.8 cm yr−1 in 1978–1999. During the rapid fall stage of sea level, the Volga delta-plain expanded at a rate of 2.3 km2 yr−1 to 180 km2 yr−1 because of alluvial accumulation and exposure of the shallow avandelta. Flourishin...

The present research reconstructs the histories of chemical weathering in the drainage basins of the Changjiang and Huanghe based on the chemical compositions of the river sediments. The silicate weathering of the Changjiang Basin is strong and Naand Ca-silicate minerals are considerably dissolved, while other silicate minerals are less attacked. In comparison, the Huanghe Basin is characterized by very weak silicate weathering, and the weathering degree corresponds well with that of the loess which is the predominant source of the Huanghe sediment. Overall, the Changjiang and Huanghe basins constitute a consistent weathering spectrum from the early to intermediate stage. The similarity of chemical compositions between upper continental crust and the Huanghe sediments as well as the low degree of chemical weathering in the Huanghe Basin imply that the river sediments can be considered to be the representative of UCC and are suitable for studying the evolution of continental crust. Our observations indicate that climate is the predominant factor controlling silicate weathering in both river basins, while controls by source rocks and relief are subordinate. Highly erosive river basins such as the Huanghe produce poorly weathered materials, which casts doubt on the idea that strong physical weathering naturally contributes much to chemical weathering. Differences in silicate weathering processes between the Changjiang and Huanghe basins may provide more constraints in estimating atmospheric CO2 budget in China. D 2003 Elsevier B.V. All rights reserved.

Loess deposits (Xiashu Loess) are widely distributed in the lower Changjiang Valley, East China, and are considered to be of eolian origin with a similar provenance to the well-documented loess of north-central China. The Xiashu Loess is characterized by strong dissolution of carbonate, and considerable weathering of some silicate minerals, especially plagioclase. Chemical mobility of Ca>Sr>Na>Mg was observed in the Xiashu Loess sediments, whilst most transition metals are relatively enriched. Chemical index of variation (CIA) and element ratios of K/Na and K/Ca record several paleoclimate events in the lower Changjiang Valley during the mid-late Quaternary, corresponding with isotopic records in deep-sea sediments. East China might be governed by stronger summer monsoons than north-central China during interglacial periods of the mid-late Quaternary, which may somewhat obscure the record of winter monsoons during glacial periods.

The Yellow Sea has been extensively studied for the understanding of dispersal patterns and limits of sediments from neighboring countries including China and Korea. Although sedimentological, mineralogical, and geochemical approaches have been tried to solve the problems, especially including the identification of sediment sources in and around the Yellow Sea, the published results are not enough for understanding them. Suggestions on sediment origins, budgets, sediment accumulation rates, mineralogical, and geochemical compositions are not coincident to each other and sometimes even controversial; for example, conflicts on the distribution patterns of smectite and calcium carbonate, the provenance of the southeastern Yellow Sea mud and sedimentation rates in there, the ratios of V/Al and Mn/Al in Korea and China river sediments, the origin of Ba and Pb in sandy sediments of the northeastern Yellow Sea, and so on. Various geochemical indicators from the literature for the provenance discrimination in the Yellow Sea are reviewed here in depth, and corresponding discussions are described separately. Research topics for the future study, also, are suggested for the proper access to the understanding of the origin and dispersal patterns of the Yellow Sea sediments, especially focusing on the geochemical approaches. D 2003 Elsevier Science B.V. All rights reserved.

The sequence boundary and maximum flooding surface of the postglacial transgressive cycle in the Changjiang Delta have been identified by 265 cores. Based on these data, the sediment amounts and the thickness-isopach maps of postglacial sedimentary cycle, transgressive and regressive successions in the Changjiang Delta have been worked out. The results show that the sediment amounts of the postglacial cycle, transgressive succession and regressive succession are 17742.2 × 108 tons, 9791.9 × 108 tons and 7950.3 × 108 tons, respectively. The postglacial sediments deposited in the incised valley are more than those in the two flanks, and the sediments contained in the transgressive succession are more than those in the regressive succession. The postglacial sediments deposited in the southern flank are more than those in the northern flank, and the sediments in the area seaward from the postglacial transgression maximum (PTM) of each flank are more than those in the area landward from the PTM. Considering both the possible changes of the ratio between the sediment amount remained in the modern Changjiang Delta and the sediment discharge of the Changjiang River in the postglacial period, and the changes of the sediment discharge, the authors believe that in the postglacial period, the sediment discharge of the Changjiang River is (2.36–4.86) × 108 tons/a on average, totaling to (35400–70800) × 108 tons, and the sediments delivered to sea and adjacent coasts are (1.18–3.54) × 108 tons/a on average, totaling to (17700–53100) × 108 tons.

Rare earth element (REE) compositions of the suspended sediments from the rivers around the Yellow Sea were different in that Korean river sediments (Han, Keum and Yeongsan Rivers) yield stronger fractionations than Chinese river sediments (Changjiang, Huanghe and Yalujiang), shown by obvious enrichments of LREE (light rare earth element) relative to UCC (upper continental crust). Variations of source rock compositions in the drainage basins are responsible for the differences of REE compositions between the river sediments. REE fractionation parameters including (La/Yb)UCC and (Gd/Yb)UCC as well as the ratios of La/Sc and Th/Sc can be treated as proper proxies for identifying the Chinese river sediments from those Korean river matters, and furthermore, for studying the provenances and paleoenvironmental changes of the marginal seas of China.

The relatively abundant palynomorphs were recovered from the samples of the first paleosol layer of core CY in Shanghai for the first time. A total of 55 genera and families of spore, pollen and phytoplankton were identified. According to the characteristics of the palynological assemblages, the depositional conditions in the development period of the paleosols were discussed and the microfossil evidence to study the origin of the paleosols in the Yangtze Delta area was provided as well. The research results show that paleosols should be freshwater deposits. The palynological assemblage sequence in the first paleosol layer reveals fluctuations of freshwater palynomorphs, mainly Concentricystis, and terricolous herbs pollen, reflecting the alternations of deposition and exposure in the development period of the paleosols. Concentricystis developed prosperously in the period of flood, while terricolous herbs grew on the emerged land in the period of exposure. The variations in the palynological assemblages suggest that the depositional conditions were various during the formation of the paleosols, and resulted in obvious stage characteristics of the paleosol’s development. The dinoflagellate cysts occur in low abundance in the palynological assemblages of the first paleosol layer of core CY, indicating that the area where core CY lies was influenced by seawater in the depositional period of the parent materials of the paleosols.

Based on field observations of the preservation potential and genesis of couplets and small sequences, diastems occur within tidal flat deposits at scales of semi-tidal, daily, monthly, and yearly intervals. Thus, tidal flat deposition is riddled with more diastems of different scales than previous assumptions. Units that are apparently complete when examined at longer time scales actually contain many diastems when examined at a shorter time scale. Diastems within tidal flat deposits are generated not only by high-magnitude storm waves, which occur during typhoon seasons, but also by daily erosion produced by tides and weak waves during calm-weather seasons. The missing intervals in diastems generated by storm waves can be several days to several years. Preservation potential of storm-generated small sequences is of the order of one-third. Diastems generated by erosion, by tides, and weak waves can have spans from a semidiurnal cycle to several days. They are easily overlooked because of the low-magnitude destruction and lack of distinctive sedimentary features. Net erosion by tides and weak waves is unexpectedly increased by day-to-day processes. Alternations of sandy and muddy laminae are related to tidal rhythm, but individual laminae can be separated by a significant diastem. Documentation of erosion by tides and weak waves under normal (non-typhoon) conditions is the principal focus of this report.

A Late Quaternary stratigraphic framework of the Yangtze delta, China, has been established based on the analysis and correlation of over 600 cores. Thirty cores were drilled and analyzed during this study, and the rest were collected from numerous publications. The Late Quaternary stratigraphic framework of the Yangtze delta consists of incised-valley fill and two interfluvial sequences. The incised valley roughly coincides with the modern Yangtze delta. From bottom to top, the incisedvalley fill sequence is typically composed of channel, floodplain–estuary, estuary–shallow marine, and modern deltaic facies. The interfluvial sequences occur along the two flanks of the incised-valley fill. On the southern flank, seaward of the maximumtransgression line, the interfluvial sequence is typically composed of marsh–nearshore, shallow marine, and tidal flat facies with predominantly muddy deposits. On the northern flank, the interfluvial sequence is typically composed of barrier–lagoon, tidal sand ridge, and littoral–tidal flat facies with predominantly sandy deposits. The interfluvial sequence landward of the maximum-transgression line on both flanks is composed mainly of lacustrine muddy deposits. The post-glacial fining-upward incised-valley fill sequence was formed by retrogressive aggradation in the lower reach of the Yangtze River, induced by sealevel rise. The upstream extent of the retrogressive aggradation exceeds the reach of flood tidal currents, which explains the lack of marine fossil and tidal sedimentary structures in the channel sand deposits. A huge estuary was formed in the present Yangtze delta area when the post-glacial transgression reached maximum at about 7500 years BP. The shallow marine mud was deposited broadly in the estuary and the maximum flooding surface, which separates the underlying transgressive sequence from overlying regressive sequence, located within the muddy stratum. An erosional surface between the channel sand unit and deltaic sand unit exists at the apical area of the Yangtze delta. The modern Yangtze delta developed after the post-glacial transgression maximum was reached. The delta development was dominated by the abundant fluvial sediment supply. Six subdeltas with a southward migrating trend have developed. D 2002 Elsevier Science B.V. All rights reserved.

The mesotidal Changjiang Estuary is characterized by high suspended sediment concentration, broad mudflats, no barrier islands, and a semidiurnal tidal regime controlled by the tropical period. Study mudflats are located at the south flank of the Changjiang Delta, facing the East China Sea. Thickness and number of tidal couplets deposited on the mudflats were measured daily and fortnightly over three neap-spring cycles. Changes in mudflat elevation were monitored from May (pre-typhoon season) to August (mid-typhoon season). Daily observation of sedimentary features shows that short-term deposition on the mudflats during calm weather is controlled mainly by tides. Neap-spring cyclicity can be extracted from the variation of sand-mud couplet thickness. High suspended sediment concentration allows deposition of two couplets per semidiurnal tide. However, number of couplets preserved per tidal cycle is reduced because of reworking and erosion by tidal currents and waves. Over a fortnightly period, tidal cyclicities are obscured, with ca. 80% of the couplets reworked. On a seasonal scale, sand-dominated layers reflect deposition during storms and mud-dominated layers reflect deposition from tides during calm weather. Two orders of sand-mud lamina alternations were examined in the tidal-flat succession. The first-order alternations are in the range of centimeters to decimeters (consisting of 16-26 couplets) and related to storm-calm weather variation; the second-order, millimeter-thick alternations are related to tidal rhythm. Deposition rates decrease exponentially as time scales increase. The open-coast tidal-flat succession is truncated with numerous depositional hiatuses.

Concentrations of 25 elements in the fine-grained fraction (6 63 Wm) of bottom sediments of the Changjiang and the Huanghe were determined to characterize the geochemical compositions of each riverine origin. Most of the elements, except for alkali and alkaline earth elements (Na, Ca, Sr and Ba), are highly enriched in the Changjiang sediments compared to those in the Huanghe sediments. Differences in source rocks and weathering mechanisms between the two drainage basins are the major factors controlling those compositional characteristics. The provenance index of core sediments from the northern Jiangsu coastal plain, calculated with nine elements with distinct compositional differences between both river sediments, indicates that the Changjiang had prevailed in the coastal plain sedimentation during the early stage of Holocene, while the Huanghe dominated over the area during the late Holocene. However, neither of the signatures of the modern Changjiang- and Huanghe-derived sediments is remarkable in the present-day coastal plain. 5 2002 Elsevier Science B.V. All rights reserved.

Thirty-four samples from the Changjiang and Huanghe were analyzed to characterize their rare earth element (REE) compositions. Although REE concentrations in the Changjiang sediments are higher than those of the Huanghe sediments, the former are less variable. Bulk samples and acid-leachable fractions have convex REE patterns and middle REE enrichments relative to upper continental crust, whereas flat patterns are present in the residual fractions. Source rock composition is the primary control on REE composition, and weathering processes play a minor role. Grain size exerts some influence on REE composition, as demonstrated by the higher REE contents of clay minerals in sediments from both rivers. Heavy minerals contribute about 10^20% of the total REE in the sediments. Apatite is rare in the river sediments, and contributes less than 2% of the REE content, but other heavy minerals such as sphene, allanite and zircon are important reservoirs of residual REE fractions. The Fe^Mn oxides phase accounts for about 14% of bulk REE content in the Changjiang sediments, which could be one of the more important factors controlling REE fractionation in the leachable fraction. 6 2002 Elsevier Science B.V. All rights reserved.

The Changjiang (Yangtze) River, one of the largest rivers in the world, has formed a broad tide-dominated delta at its mouth during the Holocene sea-level highstand. Three boreholes (CM97, JS98, and HQ98) were obtained from the Changjiang delta plain in 1997–1998 to clarify the characteristics of tide-dominated delta sediments and architecture. Based on sediment composition and texture, and faunal content, core sediments were divided into six depositional units. In ascending order, they were interpreted as tidal sand ridge, prodelta, delta-front, subtidal to lower intertidal flat, upper intertidal flat, and surface soil deposits. The deltaic sequence from the prodelta deposits to the delta front deposits showed an upward-coarsening succession, overlain by an upward-fining succession from the uppermost part of the delta front deposits to the surface soil. Thinly interlaminated to thinly interbedded sand and mud (sand–mud couplets), and bidirectional cross laminations in these deposits show that tide is the key factor affecting the formation of Changjiang deltaic facies. Sediment facies and their succession combined with AMS 14C dating revealed that isochron lines cross unit boundaries clearly, and delta progradation has occurred since about 6000 to 7000 years BP, when the rising sea level neared or reached its present position. The average progradation rate of the delta front was approximately 50 km/kyear over the last 5000 years. The progradation rate, however, increased abruptly ca. 2000 years BP, going from 38 to 80 km/kyear. The possible causes for this active progradation could have been an increase in sediment production in the drainage basin due to widespread human interference and/or decrease in deposition in the middle reaches related to the channel stability caused by human activity and climatic cooling after the mid-Holocene.

Study of Asian major rivers discharge to the ocean reveals variations of their water discharges and sediment loads, and local characteristic of river sediment concentrations. On the basis of this, the Asian rivers can be divided into three regions: Eurasia Arctic, East Asia, Southeast and South Asia Region. The Eurasia Arctic Region is characteristic of the lowest sediment concentration and load, while the East Asia Region is of the highest sediment concentration and higher sediment load, and the Southeast and South Asia Region yields higher sediment concentration and highest sediment load. The sediment loads of these regions are mainly controlled by climate, geomorphology and tectonic activity. The Eurasia Arctic rivers have large basin areas and water discharge, drain low relief which consist of tundra sediment, thus causing the lowest sediment load. The East Asia rivers have small basin areas and lowest water discharges, drain extensive loess plateau, and transport most erodible loess material, which results in highest sediment concentration. The Southeast and South Asia rivers originating from the Tibetan Plateau have large basin areas and the largest water discharges because of the summer monsoon and high rainfall influence, causing the highest sediment load. In Asia, the tectonic motion of the Tibetan Plateau plays an important role. Those large rivers originating from the Tibetan Plateau transport about 50% of the world river sediment load to the ocean annually, forming large estuaries and deltas, consequently exerting a great influence on sedimentation in coastal zones and shelves.

Non-barrier mudflats in the Changjiang Estuary is examined to obtain preservation potentials and deposition rates over different time scales. The preservation potential of couplet is ca. 46.6% within daily scale and decreases as the time-interval extending, with 9.2% on a semi-lunar scale and 3.7% on a seasonal scale. In the long term, only 1.6% of daily deposition can potentially be preserved in the tidal flat sequence and other 98.4% have been eroded and leave sedimentary discordances, discernable or un-discernable, in the mudflat deposits. A negative log-linear relationship is examined between sedimentation rates and the time spans. The length of sedimentary hiatuses on the mudflat deposition were estimated with considerable uncertainty, but it can provide from an actualistic base some further insights into the nature and origin of ancient mudflat deposits with emphasis on the sedimentary discordances.

Analyses of 41 elements reveal that Holocene sediments in the Changjiang Estuary bear regular elemental compositions in different sedimentary environments, and Holocene sediments came mainly from the Changjiang River based on compositions of REEs and most trace elements. Some heavy metals are more enriched in the surface sediment than in the deltaic sediments, reflecting human impact. Elemental compositions of the river channel sediment are related to the influence of proximal sediments. Sedimentary environments exert some influences on elemental compositions. Some chemical indices can be used to record chemical weathering undergone by the Changjiang sediment and environmental change.

A large estuary was formed by marine inundation of the paleo-Changjiang (Yangtze) incised valley during the transgression after the Last Glacial Maximum. This paper presents the sedimentary facies and architecture of the estuary fill, based on the analysis of three sediment cores (CM97, JS98, and HQ98) obtained from the present Changjiang delta plain. Estuary fill deposits showing an upward-fining succession were grouped into five depositional facies: tidal river, distributary channel, muddy intertidal to subtidal flats, transgressive lag, and estuary front, based on sedimentary textures, lithology, and physical sedimentary structures. Sand–mud couplets are common in these deposits, indicating that tides played a significant role in producing these sedimentary structures and that the estuary type was tide-dominated. Some of the successive sand–mud couplets probably recorded neap-spring cycles as well as semidiurnal tidal cycles. The nature of the estuary was very different from other representative tide-dominated estuaries in sediment facies, its distribution, and sediment source for estuarine fill. Unlike the other estuaries that receive sediments mainly from the sea, the paleo-Changjiang estuarine fill deposits were supplied largely from the river. This difference would also have a great influence on the sedimentological and morphological component in the estuary. The sediment distribution of the estuary showed fining-seaward and estuary-mouth sand bodies fed by marine-source sand were absent. The architecture model of tide-dominated estuaries should be divided into two types by the degree of fluvial sediment supply. The paleo-Changjiang estuary shows a good example for an estuary of large rivers.

A radial tidal sand ridge system (RTSRS) spans more than 20 000 km 2 in the southwest Yellow Sea, is fan-shaped and stretches from Qianggang toward the sea. The marine RTSRS is located in a convergent–divergent tidal current field (CDTCF). Numerous drilling holes reveal an area of 3000 km 2 containing tidal sand strata in the Jiangsu coastal plain on land, adjacent to the marine RTSRS, which stretches eastward from Chengdong and is also a fan-shaped with a central angle of 130°. The tidal sand unit lies on a transgressive coastal barrier-lagoon unit with an erosional surface between them, and the latter unit is in turn lying on late Pleistocene stiff mud. The tidal sand unit is overlain by the littoral–tidal-flat unit and together they constitute the Holocene regressive succession. Paleo-current study reveals that a paleo-current pattern similar to the modern marine CDTCF was present in the Holocene sub-aerial tidal sand strata. Therefore, the sub-aerial tidal sand bodies are deduced to be an ancient RTSRS that was formed during the Holocene regression, and gradually exposed and changed into land as the Changjiang and Huanghe deltas prograded. Both sub-aerial and marine RTSRS should be formed in the same tidal depositional environment but in different development stages. Thus, the radial tidal sand ridges in southwestern Yellow Sea should have formed not during the Holocene transgression, as most previous studies have inferred, but in the process of Holocene regression. Mineralogical analyses demonstrate that the sediment source of the sub-aerial RTSRS initially came from the Changjiang and later predominantly from the Huanghe. Sea-floor erosion by tidal currents may also provide sandy material to form the RTSRS. Drilling cores and ground-penetrating profiles show that the paleo-valleys in the study area are much smaller than the present distributaries of the Changjiang River. Thus, the presumption of direct sand supply by a large river to form the RTSRS through its apical area is cannot be supported. After the sea level reached the present high stand, the Jiangsu coastline has been prograding seaward as the Changjiang Delta expanded and this progradation was accelerated when the Huanghe debouched in the study area. The nearshore part of RTSRS has been gradually changing into land while the entire RTSRS extends seawards. In the process of the development, the RTSRS apex changed from Chengdong to Qianggang. At present, the coastline is still moving seaward while the outer part of the RTSRS suffers from some erosion owing to reduction of sediment supply from both the Changjiang Delta and the abandoned Huanghe Delta.

The Yangtze Delta area may be subdivided into paleo-valley and paleointerfluves of the last glaciation. The postglacial transgressive sedimentary cycle (PTSC) on the front zones of the paleointerfluves is composed of marsh-nearshore and barrier-lagoon, shallow marine and nearshore-tidal flat units, with a basement in stiff clay. The PTSC in back zones of the paleointerfluves consists of lacustrine-marsh deposits. The PTSC in the incised valley contains river channel, floodplain-estuary, estuarine-shallow marine and deltaic units, with an erosional surface at its bottom. The stiff clay and the erosional surface constitute the PTSC lower boundary. The stiff clay, consisting of a paleosol, experienced deposition alternating with pedogenesis during the falling of sea-level during δ18O stage 3; ongoing pedogenesis in the sea-level lowstand of δ18O stage 2; and early diagenesis after paleointerfluve inundation by the sea-level rise of δ18O stage 1. The climate during the paleosol formation was temperate with more than 500-mm a−1 rainfall and frequently fluctuating groundwater. The Yangtze River incised its course during falling sea level of stage 3, and a huge incised valley was formed during the sea-level lowstand (stage 2). The filling of the incised valley took place during the postglacial sea-level rise, and delta formation occurred at a late stage of PTSC development.

The subaerial tidal sand area in the northern Jiangsu Province (Subei), stretching from Dongtai towards east with a fan shape, is an early developing stage of radial sand ridges distributed in the South Yellow Sea. Since 5 000-6 000 a BP, after the Holocene transgression maximum in the northern Jiangsu Province, subaqueous tidal sand bodies were exposed and changed into land gradually. The environmental magnetism analysis shows that subaerial tidal sand strata are formed by the convergent-divergent paleo-tidal current field. The sediment source of tidal sand strata came early from the Changjiang River and late from the Yellow River. Sea floor erosion by tidal currents also served as an important sand source. Drilling cores and ground-penetrating profile show that there exists no probability of sand supplying directly by a large river through the apical area of tidal sand ridges either on land or in the sea. Fluvial deposits supplied the tidal sand bodies by alongshore transportation, which corresponds to the conclusions obtained by the analyses of provenance and paleocurrent field.

The late Quaternary paleosols in the Yangtze Delta area developed in the period of 25 000–12 000 aBP. Phytolith ratios (value A) of contents of fan, square and rectangle types indicating the warm and humid climate to those of bar, hat and point types indicating cold and dry climates decrease upwards overall on profiles of the paleosols, suggesting that the climates turned from warm and humid to cold and dry. So, the paleosols developed mainly during the regression before the last glacial maximum. Changes of value A indicate no trend of warming, suggesting that the transgression was rapid after the last glacial maximum. The development of the paleosols exhibited obvious stages, which were controlled remarkably by transgression and regression: I. Period of alternation of deposition and pedogenesis, which was from the occurrence of regresson before the last glacial maximum to the time when sea levels fell close to the lowest; II. Exposure period with continual pedogenesis, which was terminated when the paleosols were drown in the post-glacial transgression; III. Period of being drown and buried, the paleosols were buried by marine sediments, and reworked by early diagenesis.

Comparison of magnetic fabric parameters of deposits in different modern sedimentary environments indicates that values ofP, F andL of eolian deposits are lower obviously than those of hydrogenic ones respectively. On relationship diagrams of magnetic fabric parameters, data points of eolian samples concentrated in limited area near origin of coordinates indicate that dynamic intensity is lower with less variation; while those of hydrogenic ones depart from origin of coordinates suggest higher intensity of sedimentary dynamics. Analyses of dynamic characteristics of different sedimentary environments indicate that values of magnetic fabric parameters of deposits are determined by dynamic types and characteristics of depositional processes. Magnetic fabric analyses of deposits are effective in determination of sedimentary environments.

The result of measurements and analyses on magnetic fabrics data for the late Quaternary core at Caoyangxincun in Shanghai shows that abrupt changes of magnetic fabric curves coincide with the boundaries between the marine strata and underlying stiff clay. Littoral, neritic, subtidal and tidal flat facies in the marine strata have distinct magnetic fabric characteristics. The curves of the parameters,K, P, L, q, display clear boundaries between various facies, which could serve as a new method for the stratigraphic subdivision and correlation.

The volumes of each sedimentary facies in the Qiantongjiang estuary area have been calculated based on layer thickness data of about 100 bores. The sediment sources of each facies have been discussed on the basis of the previous work and the above calculations.

IN the southern Yellow Sea there exists a large radial sand ridge system,which covers about 20 000 km2. Sand ridges and troughs occur alternately within the system, and single sandridges are tens of kilometers, even more than one hundred kilometers long and ten to fifteenkilometers wide. Due to the distribution pattern of the radial sand ridge system being like finer...