reconstruction of holocene foreland progradation using optically stimulated luminescence osl dating an example from dungeness uk roberts helen plater a j 2007 reconstruction of holocene foreland progradation using optically stimulated luminescence osl dating an example from dungeness uk the holocene 17 4 pp 495 505 rae2008

sedimentary structures tentatively attributed to seismic events abstract fingerprints of earthquakes in the sedimentary record are as yet difficult to identify this is particularly true for failure phenomena dewatering slumping fault graded and turbidite structures that could have been triggered also by other kinds of energy input other promising candidates are strange biostratinomic features convex down stacking of shells current orientation in wave ripple accumulations as well as certain preservational features found in geosynclinal pelagic limestones but in every case verification of the seismic origin is still needed

a raised ois 3 sea level recorded in coastal sediments southern changjiang delta plain china abstract the distribution of marine influenced oxygen isotope stage ois 5 to ois 1 sediments was examined in several late quaternary boreholes from the southern changjiang yangtze delta plain china using different dating methods including osl u series ams 14c and paleomagnetism results demonstrate that coastal and estuarine deposition during ois 5 and ois 3 occurred throughout the study area however holocene transgressive sediments were absent on the taihu block the burial depth of intertidal to subtidal sediment deposited during ois 5e records 30 80 m subsidence caused by sediment compaction and tectonic movement since that time however coastal sediments formed during the late phase of ois 3 were buried to a depth of ca 6 15 m in the taihu lake area while the burial depth increased eastward to ca 45 60 m on the coastal plain this phenomenon combined with the distribution of holocene marine strata indicates at least 25 30 m uplift of the taihu block since the end of ois 3 we suggest that this uplift was mainly caused by the differential subsidence due to substantial amount of post glacial deposition by the changjiang and huanghe rivers on the continental shelf of east china marginal sea

refined chronostratigraphy of a late quaternary sedimentary sequence from the yangtze river delta based on k feldspar luminescence dating abstract dating of sediments in the tidal dominated yangtze river delta remains a challenge because of extremely complicated processes during sediment transport and deposition in such a fluvial marine transition zone to better understand the late quaternary sedimentary history of the yangtze river delta we explore the applicability of k feldspar luminescence dating techniques to deposits through a case study on a 60 m long borehole core yz07 in the delta and then establish a spanning 50 000 year long chronological sequence a series of luminescence pre tests including dose recovery tests and determination of residual dose and fading rates were implemented using the modified single aliquot regenerative dose sar protocol for post infrared ir ir stimulated luminescence irsl measured at 150 c after prior irsl at 50 c pirir150 luminescence characteristics of the prior irsl ir50 and pirir150 were then analyzed to check their validity two fading correction models were utilized to correct apparent ages obtained from ir50 and pirir150 signals the newly obtained k feldspar luminescence ages were compared with quartz osl ages and 14c ages our results indicate that most of ages derived from pirir150 signals were overestimated due to incomplete bleaching in contrast the fading corrected ages from ir50 measured in pirir150 protocol are robust as they are consistent with quartz osl ages and 14c ages as well as the stratigraphy especially ir50 ages are characterized by negligible residual dose and thus reliably used for defining chronology of the chronological sequence over the past 50 ka our positive results of k feldspar dating shed light on further exploration of older unit in the yangtze river delta in combination with sedimentological and paleontological analyses of core yz07 we find fluvial to tide influenced fluvial deposits were emplaced during the period 30 50 ka which were then overlain by post glacial tidal river 13 11 5 ka and holocene estuarine shelf delta system and tidal flat deposits in the yangtze river delta together records of yz07 with other chronostratigraphy from the collected cores we confirm the existence of marine isotope stage mis 3 depositional units along the marginal coast of the yangtze river delta in relation to the interstadial sea level highstand our stratigraphic correlation based on the refined chronology reveals offshore transition of the mis 3 unit into facies deposited in deeper and offshore marine environments

episodic overbank deposition as a dominant mechanism of floodplain and delta plain aggradation the common view that frequent overbank flooding leads to gradual aggradation of alluvial strata on floodplains and delta plains has been challenged by a variety of studies that suggest that overbank aggradation occurs in a strongly episodic fashion however this remains a largely untested hypothesis due to the difficulty in establishing age models with sufficiently high resolution here we use 39 optically stimulated luminescence osl ages from proximal overbank deposits in the mississippi delta to demonstrate for the first time that alluvial aggradation over centennial to millennial time scales is predominantly episodic with aggradation rates of 1 4 cm yr that can persist for centuries osl ages from three separate study areas produce age clusters that are distinctly different yet complement each other these findings suggest that a substantial portion of the continental stratigraphic record consists of patchworks of relatively discrete centennial to millennial scale sediment bodies assembled by autogenic processes

sedimentary facies of the tide dominated paleo changjiang yangtze estuary during the last transgression abstract 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

chronology of a sedimentary sequence from the land ocean interaction zone in the north jiangsu basin abstract the north jiangsu basin njb located in the western part of the north jiangsu south yellow sea basin is a critical region providing invaluable archives about the evolution processes of the land ocean interchange and climatic environments in a coastal zone chronology is of crucial importance to reconstruct the timing of sea level eustacy and shoreline changes as well as the evolution of the regional environment by means of numerical dating to determine the age of sedimentary strata in the sea land interaction zone of the njb however sediment dating in the njb remains controversial due to limitations in the quantity and quality of chronological data therefore the sediments in the jianhu gangxi gx profile of the njb were analyzed in this study by applying both fine grained quartz optically stimulated luminescence osl dating and 14c dating the results were used to discuss the processes of regional environment evolution the osl dating of fine grained quartz components in sediments was found to be a reliable method to determine deposition ages of sediments in the land sea interaction zone in the njb the combination of osl and accelerator mass spectrometry 14c dating techniques allowed a reliable and high resolution chronological framework for the gx profile since the last glaciation the sedimentary environment in the eastern portion of the njb changed significantly in particular 1 between 13 and 7 25 ka b p the area of interest was dominated by lacustrine deposition within a stable sedimentary environment with low deposition rates 2 from 7 25 to 6 45 ka b p marine transgression events occurred and the deposition rate increased rapidly in an area of land sea interaction 3 after 6 45 ka b p a regression event occurred and the study area transformed into a lowland lake environment

evolution of the coastal depositional systems of the changjiang yangtze river in response to late pleistocene holocene sea level changes abstract the paleo changjiang yangtze incised valley fills approximately 80 90 m thick provide an opportunity to document the evolution of coastal depositional systems with large sediment supply in response to late pleistocene holocene sea level fluctuations on time scales of 103 to 104 years the sedimentary facies of the incised valley fills record three main depositional systems fluvial tide dominated estuary and tide dominated delta radiocarbon ages for the incised valley fills suggest that these depositional systems developed before about 11 ka between 11 and 8 ka and after approximately 8 ka respectively by applying sequence stratigraphic concepts the evolution of the depositional systems can be divided into three systems tracts a lowstand systems tract lst a transgressive systems tract tst and a highstand systems tract hst sea level changes on a 104 year time scale controlled the basic architecture of the sequence of the incised valley fill on the other hand sea level changes on a millennial time scale affected the stacking pattern of the systems tracts in particular the continuous sea level rise with episodic rapid rises during the last deglaciation affected the stacking pattern of the tst which is characterized by a combination of aggradation and backstepping the aggradation of fluvial and estuarine systems was dominant and the shoreline migrated only gradually landward under the relatively slow rise in sea level and a very rapid sea level rise around 12 and 10 ka caused the system to migrate abruptly landward unlike the transgressive estuarine phase the stacking pattern of the regressive tide dominated delta hst which developed within the almost filled incised valley and on the surrounding interfluve zones was characterized by seaward progradation with clinoform architecture it was initiated with aggradational and progradational stacking about 8 ka during the last phase of decelerated sea level rise and was followed by a progradational phase after the highest sea level about 6 ka

early to mid holocene rapid sea level rise and coastal response on the southern yangtze delta plain china we used accelerator mass spectrometry ams 14 c dated sediments of the holocene basal supratidal flat to upper tidal flat facies in 11 cores on the southern yangtze delta plain to reconstruct relative sea levels of 8 5 8 0 cal ka bp three cores were further ams 14 c dated and used to examine the evolution of sedimentary geomorphological environments in response to the rapid sea level rise during the early to mid holocene results demonstrate relative sea level rise of around 30mm a 1 from 8 5 to 8 3 cal ka bp and around 10mm a 1 from 8 3 to 8 0 cal ka bp retrogradation from supratidal to lower tidal flat environments occurred in response to the rapid sea level rise at 8 5 8 3 cal ka bp and aggradation from middle to upper tidal flat occurred at 8 3 7 9 cal ka bp further retreat of the tidal flat at 7 9 7 2 cal ka bp implies a mean sea level rise rate exceeding 5mm a 1 at this time we suggest that the rapid relative sea level rise during 8 3 8 5 cal ka bp and subsequent slower rise caused drastic changes in the coastal zone and that these changes are key phenomena for understanding the coastal response to future sea level rise copyright 2013 john wiley sons ltd

stratigraphy and paleoenvironmental changes in the yangtze delta during the late quaternary 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 18o stage 3 ongoing pedogenesis in the sea level lowstand of 18o stage 2 and early diagenesis after paleointerfluve inundation by the sea level rise of 18o 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

facies patterns and subsidence history of the jumilla cieza region southeastern spain abstract a detailed analysis of the facies patterns and subsidence history since the late cretaceous 100 ma of the jumilla cieza region in southeastern spain has implications for the debate on the mechanisms causing third order changes in sea level the local subsidence history shows periods characterized by specific trends in tectonic subsidence each with a typical concomitant facies pattern the successive periods are considered to illustrate the transition of the southern iberian plate boundary from a passive margin 108 40 ma through an extensional phase 40 20 ma to a thrust and fold belt 20 ma to recent timing and changes in relative sea level derived from the sedimentary record closely match with the regional tectonic events the order of magnitude of these sea level changes exceed those predicted by the global curve therefore we suggest that in the studied area third order sea level fluctuations are of relatively minor magnitude and only enhance the effect of tectonic induced vertical movements

a robust geochronology of the yangtze river delta based on magnetostratigraphy and cyclostratigraphy of sediment core zka2 abstract studying the evolution of sea level fluctuations climate oscillations and tectonic movements in the yangtze river delta requires a reliable chronology here we present the results of a comprehensive study of the magnetostratigraphy and cyclostratigraphy of a 295 m long sediment core zka2 recovered from nantong city jiangsu province china anisotropy of magnetic susceptibility ams studies reveal that the petrofabrics are mainly primary based on rock magnetic and thermal demagnetization analyses the major magnetic minerals in the studied sediments are magnetite hematite and greigite but only magnetite and hematite carry the primary remanence the magnetostratigraphy reveals seven reversed polarity intervals nine normal polarity intervals and one interval of mixed polarity variations in natural gamma ray activity reflect variable continental weathering in the sediment source regions and are paced by earth orbital cycles notably a prominent 405 kyr long eccentricity cycle and 100 kyr short eccentricity cycle are evident which allow us to constrain the basal age of core zka2 to 3 1 ma the magnetostratigraphic and cyclostratigraphic results together enable us to define the depths of key chronostratigraphic and magnetostratigraphic boundaries they include the late middle pleistocene boundary at 18 m depth the brunhes matuyama boundary at 88 m depth and the matuyama gauss boundary at 254 m depth according the new chronology we find that although clear long eccentricity 405 kyr and short eccentricity cycles 100 kyr cycles are evident in the magnetic susceptibility record they are not well matched with cycles of natural gamma ray activity this suggests the source and post depositional process of the magnetic particles is complicated and it should be cautious to choose magnetic properties for cyclostratigraphic analysis

combined chronological and mineral magnetic approaches to reveal age variations and stratigraphic heterogeneity in the yangtze river subaqueous delta abstract delta deposits show large spatial heterogeneity in terms of depositional rate and age which is critical to the study of delta erosion in response to the declining fluvial sediment load observed at many river mouths in the world in this study we show that the magnetic susceptibility can be an indicator to reveal age variations and stratigraphic heterogeneity in the yangtze river subaqueous delta ages of three short sediment cores 1700 years the cores at shallow water depths are younger than those from deeper sites modern deposits i e 800 a show lower and uniform values due to the reductive dissolution of ferrimagnetic minerals while younger sediments

optical dating of holocene tidal deposits from the southwestern coast of the south yellow sea using different grain size quartz fractions abstract the tidal flat deposit provides ideal sedimentary records for paleoenvironmental studies reliable chronology is crucial to utilize this archive for deciphering the history of environmental changes in this study we applied optically stimulated luminescence osl dating method to a holocene tidal flat sequence using both coarse grained cg 90 200 m and fine grained fg 4 11 m quartz extracts from a sedimentary core yz07 in western coast of the south yellow sea the luminescence characteristics of the two grain size fractions were investigated and then their resulting osl ages were systematically compared the results suggested that most tidal flat deposits are well bleached and their fg quartz ages are generally consistent with cg quartz ages while some samples have cg ages underestimated compared with fg likely resulted from the k feldspar contamination for cg quartz hence we applied post ir osl dating and pulsed osl dating techniques they could overcome the problems caused by feldspar contamination and yielded identical dates as fg osl ages all osl ages are generally in stratigraphic order in contrast the 14c ages are much more disorder and characterized with severe inversions finally the age framework of the tidal flat sequence under this study was constructed based on the 30 osl ages and one acceptable radiocarbon age according to the age depth model three main periods of sedimentation rate sr variation were identified these sr changes are probably associated with sea level rise fall history and the depocenter landward seaward movement as well as the transition of depositional process within the holocene delta initiation the depositional environment changes were also reflected in sedimentological features of the tidal flat deposits in our study area

medium term frequency distributions of cross shore suspended sediment transport rates in water depths of 3 to 9 m abstract a data set of several thousands of hours of near bed flow obtained at three cross shore positions in 3 to 9 m water depth in the multiple bar system of terschelling netherlands was used to estimate the medium term years frequency distribution of the cross shore suspended sediment transport rates induced by short waves infragravity waves and cross shore mean flows predictions of an energetics based transport model were categorised into groups of the local height over depth ratio with a width of 0 02 and were subsequently coupled to the discrete medium scale probability distribution of this ratio at all depths the estimated medium scale sediment transport rate by the short waves q ms h and mean flows q ms mf were of approximately equal magnitude and were about three times as large as that of the infragravity waves in general the medium term sediment transport rates were dominated neither by the most extreme conditions nor by day to day situations this was related to the infrequent recurrence of the most energetic events and by the predicted negligible transport rates under daily conditions in 9 m depth breaking conditions contributed to about 90 of both q ms h and q ms mf in shallower water 3 5 m non breaking conditions became increasingly important for q ms h whereas q ms mf remained fully dominated by surf zone conditions this observation as well as literature findings for water depths less than about 3 m suggest that the range of small scale conditions that contribute most to q ms h and q ms mf changes in the onshore direction from mainly breaking conditions at depths in excess of 5 7 m towards prolonged non breaking periods for q ms h and short breaking events for q ms mf on the beach

optical dating of dune sands in the northeastern deserts of china abstract optical dating has been used to obtain the ages of fossil stabilized sand dunes from four sections in the northeastern deserts of china our results indicate that the optically stimulated luminescence ages of the four sections correlate well even though the samples were collected from different deserts about 600 km apart our results also indicate that active dune formation in this region lasted from the last glacial maximum to about 10 ka and that the warm climate of the holocene was interrupted by a cold dry dune formation episode about 3 5 1 7 ka the holocene optimum in this region is between 10 and 3 6 ka and a later warm humid dune stabilization phase lasted from at least 1 6 to 1 0 ka the youngest age on the uppermost sand unit yielded an age of only 40 yr supporting the previous argument that the existence of modern active eolian sands in the regions with a mean annual precipitation of up to 450 mm is not mainly due to drought but to extensive land cultivation over historic time from the luminescence properties of the quartz grains it is hypothesized that the sands in most of the sections are probably derived from more than one source with a minor source of quartz having a different thermal history before deposition

optical dating of holocene sediments from the yangtze river changjiang delta china abstract establishing a reliable chronology is essential for understanding delta evolution which is normally performed using radiocarbon 14c dating and the recently emerging technique of optically stimulated luminescence osl the application of the latter one to the holocene yangtze river changjiang delta deposit is still quite limited in this study two 60 9 m long cores were collected from taizhou tz and nantong nt within the paleo incised valley of the yangtze river and a total of seven and nine osl samples were collected from the tz and nt cores respectively in addition ten accelerator mass spectrometry ams 14c ages of the tz core were presented with eight ams 14c ages that were previously obtained from the nt core the single aliquot regenerative dose sar protocol was applied to coarse silt sized 45 63 m and fine sand sized 90 125 m quartz the results showed that the grains in the 45 63 m size fractions appeared to be better bleached than those in the 90 125 m size fractions and the detection of insufficiently bleached sediments is required in order to obtain accurate age estimates the ages adopted for the samples range from 3 ka to 9 ka for the tz core and from 1 ka to 14 ka for the nt core which were in general internally coherent within the limits of experimental errors and with respect to their stratigraphic order the ams 14c age of the tz core were significantly older than their osl ages while those from the nt core generally showed good agreement with their osl ages one should be cautious when using ams 14c to date deltatic deposits based on the osl ages two periods of rapid accumulation rates can be found in both cores which are linked to the rapid sea level rise in early holocene and migration of delta front facies in late holocene these investigations indicate that osl technique is an effective method with which to date holocene deltaic deposits especially in coarse sedimentary layers where organic carbon material is sparse

towards more robust chronologies of coastal progradation optically stimulated luminescence ages for the coastal plain at moruya south eastern australia accurate chronologies are fundamental for detailed analysis of palaeoenvironmental conditions archaeological reconstructions and investigations of holocene coastal morphological changes chronolog

ams 14c dating of holocene estuarine deposits consequences of high energy and reworked foraminifera benthic foraminiferal species were used to ams date holocene sediments adjacent to trangressive overlap boundaries tob in two high energy estuaries in northern spain it had previously been recognized that the foraminifera could be divided into indigenous and exotic components whereas it was known that the exotic forms had been transported into the estuaries from the adjacent inner shelf it was assumed that the indigenous forms were in situ the ams dates based on indigenous forms obtained from pairs of samples adjacent to the tob showed an inverse relationship in three out of four boreholes i e the age of the higher sample was older than that of the lower the most probable explanation of this unexpected result is that there had been significant reworking of indigenous foraminifera especially associated with the transgressive episode it is concluded that in high energy estuaries ams dating on foraminiferal shells is influenced by transport and reworking even of the indigenous component therefore if only foraminifera are available for dating we recommend that closely spaced pairs of samples should be dated in order to assess the reliability of the results

early mid holocene sea level change and coastal environmental response on the southern yangtze delta plain china implications for the rise of neolithic culture abstract we used a series of holocene sediment cores with ams 14c dated basal saltmarsh peat and supratidal sediment to reconstruct early mid holocene sea level change on the southern yangtze delta plain we also synthesized results for ca 150 late quaternary cores as well as archeological data to reveal the unique interplay between coastal evolution and neolithic cultural response relative sea level was ca 16 5 to 14 5 m from 8600 to 8500 cal bp and ca 6 to 4 m from 7400 to 7200 cal bp reflecting the rate of eustatic sea level rise but being ca 10 m higher possibly because of the effect of hydro istostasy three late pleistocene interfluve terraces t3 to t1 were revealed at burial depths of

luminescence dating of interglacial coastal depositional systems recent developments and future avenues of research abstract luminescence dating offers new opportunities to explore the evolution of quaternary marine coastal facies and landforms this review highlights the main advances in luminescence geochronology of interglacial coastal sediments through the analysis of 547 luminescence ages most of which were published during the last decade the majority of these reported luminescence investigations have been carried out along passive margin coasts since the turn of the century the discovery of a normalization procedure known as single aliquot regeneration sar has drastically reduced data scatter and improved precision with the consequence that quartz sar optically stimulated luminescence osl has become the dating protocol of choice for the last interglacial lig period a more complex technique known as thermally transferred osl tt osl is presumably proposed for dating older interglacials of the mid pleistocene and beyond feldspar luminescence is increasingly being applied to dating pleistocene sea level high stands due to a much higher dose saturation level than quartz osl the use of feldspar irsl infrared stimulated luminescence is limited by the occurrence of variable but ubiquitous anomalous fading af following the advent of af correction methods several middle pleistocene sites have been amenable to dating albeit with significant related uncertainties recently new protocols involving the measurement of post ir irsl at elevated temperatures have yielded relatively coherent ages for interglacial sediments up to ca 300 ka quartz osl tt osl af corrected irsl and post ir irsl ages are generally correlated with periods of sea level high stands a few ages are reported from the early and middle part of the middle pleistocene as mis11 9 and more commonly mis7 high stands are documented in strongly uplifting active margin coasts however by far the most obvious age peak corresponds to the end of the lig the mis5e shoreline is probably the most studied and luminescence dated coastal feature of all as the chronology of the sea level markers is crucial to assess global eustatic sea level variations through the course of the last interglacial nevertheless the observed abundance of young 100 120 ka luminescence ages for presumed mis5e sediments may underline methodological issues and or reflect the higher preservation potential of late regressive sequences on the other hand the occurrence of geographically distant reports of mis5a high stand might reflect a true eustatic origin for this event age analysis supports the impression of general reliability of luminescence for the timing of former sea level high stands there is a clear need to address issues in dose rate variability in the phenomenology of fading in feldspar and in the behaviour of luminescence growth with dose both in laboratory and natural conditions these could be addressed and properly evaluated by dating different minerals as multiple or single grains with consequent variable internal dose rates more robust practices in the application of luminescence dating techniques could eventually constrain the age uncertainties to no better than 2 3 therefore the strength of luminescence as a dating tool is more in terms of its extended age range and the ubiquity of datable material

provenance structure and formation of the mud wedge along inner continental shelf of the east china sea a synthesis of the yangtze dispersal system surficial grain size and down core clay mineralogical data show that sediment along the inner most part of the continental shelf in east china sea is mainly derived from the yangtze river changjiang spanning from the yangtze mouth 33 degrees n similar to 1000 km southward to the southwestern corner of the taiwan strait 24 degrees n high resolution chirp seismic profiles reveal an elongated mud wedge extending along the inner shelf with a northern depocenter on the modern yangtze delta and a southern depocenter at 27 5 degrees n four distinct acoustic units are delineated within the mud wedge from bottom up unit i late pleistocene mainly valley fills unit ii formed by transgressions thin strata unit iii 11 2 kyr bp downlapping strata and unit iv 2 0 kyr bp flat and opaque strata incised valleys up to 15 m deep are filled by flat lying or inclined strata in unit i the thin 3 m and acoustically transparent unit ii is only seen between 30 and 26 degrees n in water depths between 40 and 90 m separated by acoustically opaque strata or unconformities units iii and iv are widely distributed during the past 11 kyr yangtze sediment accumulation has been unsteady showing two high and one low accumulation rate periods the high accumulation period at 5 8 kyr bp may be related to maximum east asian summer monsoon precipitation in the yangtze basin the other high accumulation period 0 2 kyr bp probably reflects intensive human activities in the river s watershed the low accumulation rate period at 2 5 kyr bp which is seen in both northern and southern yangtze depocenters is probably related to low river discharge and or intensified taiwan warm current and china coastal current c 2011 elsevier b v all rights reserved

an early holocene sea level jump and delta initiation 1 early holocene sea level change controlled the evolution of clastic coastal depositional systems radiocarbon dated borehole cores obtained from three incised valley fill systems in asia changjiang song hong and kiso river record very similar depositional histories especially between about 9000 and 8500 cal bp sedimentary facies changes from estuarine sand and mud to shelf or prodelta mud suggest that the marine influence in the incised valleys increased during this period in addition large decreases in sediment accumulation rates occurred a sea level jump causes an estuarine system and its depocenter to move rapidly landward it is possible that the final collapse of the laurentide ice sheet accompanied by catastrophic drainage of glacial lakes at approximately 8500 cal bp caused such a jump the jump was followed immediately by a period of decelerated sea level rise that promoted delta initiation

initiation of the changjiang yangtze delta and its response to the mid holocene sea level change abstract the changjiang yangtze delta in eastern china is one of the largest tide dominated deltas in the world to obtain a more detailed information on its initiation we drilled three sediment cores pk01 hg01 and xj03 from the uppermost region of the delta plain on the basis of sedimentary facies and ams 14c dating we identified three depositional systems 1 a fluvial system 2 an estuarine system and 3 a deltaic system including an initial delta estuary delta transition and a typical delta the maximum flooding surface separates the estuarine and deltaic systems and occurred at ca 8 0 cal kyr bp when brackish water intruded landward and reached the nanjing area the changjiang delta was initiated at the area between nanjing and yizheng when the sea level rise decelerated after the rapid rise in sea level during 9 0 8 2 cal kyr bp the subsequent evolution of the changjiang delta has been shown as a seaward development model of river mouth bars with shoreline migration the oldest river mouth bar called hongqiao sand body which is located most landward was dated at 6 0 5 5 cal kyr bp in this study nearly one thousand years younger than the previous estimates a tide dominated funnel shaped estuary was formed at 8 0 cal kyr bp and lasted until the hongqiao sand bar became exposed this stage is regarded as an aggradation dominated initial stage of the changjiang delta followed by a progradation dominated stage that is characterized by the formation of a series of seaward migrating river mouth bars a relative sea level highstand in the mid holocene may be associated with glacio hydro isostatic tilting

refining the late holocene coastline and delta development of the northern yangtze river delta combining historical archives and osl dating historical documents provide a general chronological overview of the environmental evolution of the yangtze river delta yrd during the last ca 2000 years however absolute dating of the region

integrating geochronologic and instrumental approaches across the bengal basin constraining time is of critical importance to evaluating the rates and relative contributions of processes driving landscape change in sedimentary basins the geomorphic character of the field setting guides the application of geochronologic or instrumental tools to this problem because the viability of methods can be highly influenced by geomorphic attributes for example sediment yield and the linked potential for organic preservation may govern the usefulness of radiocarbon dating similarly the rate of sediment transport from source to sink may determine the maturity and or light exposure of mineral grains arriving in the delta and thus the feasibility of luminescence dating here we explore the viability and quirks of dating and instrumental methods that have been applied in the bengal basin and review the records that they have yielded this immense dynamic and spatially variable system hosts the world s most inhabited delta outlining a framework for successful chronologic applications is thus of value to managing water and sediment resources for humans here and in other populated deltas worldwide our review covers radiocarbon dating luminescence dating archaeological records and historical maps short lived radioisotopes horizon markers and rod surface elevation tables geodetic observations and surface instrumentation combined these tools can be used to reconstruct the history of the bengal basin from late pleistocene to present day the growing variety and scope of bengal basin geochronology and instrumentation opens doors for research integrating basin processes across spatial and temporal scales

sediment deformation structures and the palaeotectonic analysis of sedimentary basins with a case study from the carboniferous of northern england

formation of the yangtze shoal in response to the post glacial transgression of the paleo yangtze changjiang estuary china abstract the yangtze shoal lies east of the yangtze changjiang river estuary china at water depths of 25 55 m and is one of the largest subaqueous sheet like sand banks in the world previous studies have not reached a consensus regarding its origin and timing of formation mainly due to the scarcity of coring and high resolution seismic profiling in the shoal we recovered a 70 20 m long sediment core cre 1402 through the sand shoal and acquired 1586 km of high resolution shallow seismic profiles across the estuary and shoal we conducted systematic analyses of the core including its sedimentary characteristics down core changes in benthic foraminiferal assemblages and 14c and optically stimulated luminescence osl dating we also analyzed the seismic stratigraphy and integrated these results with data from other previously well studied cores onshore and offshore of the yangtze river mouth our results indicate that the stratigraphic architecture in the paleo yangtze estuary i e the area from the present day delta plain to the subaqueous delta and yangtze shoal was controlled mainly by changes in sea level during the post glacial transgression the post 14 ka sedimentary successions in the paleo estuary rest unconformably on fluvial or coastal deposits that formed mainly before mis 1 and are separated by three distinctive bounding surfaces corresponding to mwp 1a mwp 1b or the rapid sea level rise at ca 11 5 ka shortly after the younger dryas cold period and the 8 2 ka event respectively and the maximum marine flooding surface mfs the depositional unit of the yangtze shoal ranges in thickness from 6 to 32 m the shoal exhibits large scale sw dipping generally 0 5 2 foresets with local cross cutting of foresets which are composed mainly of very fine to medium grained sands the shoal is underlain by muddy intertidal to subtidal flat deposits that formed during the younger dryas with an erosional surface corresponding to mwp 1b or the rapid sea level rise at ca 11 5 ka between these and the shoal deposits the yangtze shoal came into being mainly between ca 11 5 and 7 0 ka in the form of tidal sand ridges actively moving southwestwards under intense and reciprocal tidal currents on a tidal shelf the tidal sand ridges have evolved into sheet like tidal sand banks with relatively low relief as a result of tidal remobilization under rotary tidal currents since ca 7 0 ka when the mfs formed therefore the yangtze shoal can be considered to comprise quasi active tidal sand banks

eocene seismicity in the pyrenees from megaturbidites of the south pyrenean basin spain abstract the triggering mechanism for emplacement of nine calcareous megaturbidites mt in the clastic turbidite eocene basin of the pyrenees is examined the thickness of each mt is 10 to 200 m and their volume may reach 200 km 3 their mobilization is thought to result from seismic activity related to thrust faults along the northern border of the basin we attempt to define the seismic characteristics for a volume of 100 km 3 the dimensions of the slope failures are estimated to be 100 5 10 0 1 0 2 km and related to a fault rupture length of about 50 100 km and liquefaction of basal clayey layers given these two constraints superficial earthquakes of m 7 would be required to initiate landslides

origin and evolution of interdistributary delta plains insights from mekong river delta the geometry of river deltas is considered to refl ect the interplay of coastal processes river discharge and sediment supply as 25 of the world s population lives on deltaic lowlands prediction of delta growth is critical knowledge of processes responsible for delta geometries is not well established although such knowledge is critical for the risk management of land use and settlements on deltas the mekong river delta of southern vietnam is one of the largest deltas in the world and offers a unique opportunity to understand the sedimentary evolution of mixed tide and wave dominated large river deltas we constrained the three dimensional sedimentary evolution of the delta plains based on optically stimulated luminescence dating of beach ridges coupled with radiocarbon dated sediment cores results show that the beach shoreline in the lower delta plain initiated ca 3 5 ka by aggradation on basement shoals the delta plain propagated laterally during the late holocene evolving from bars that resulted in asymmetric bifurcation of the river mouth asymmetry was caused by the southwestward longshore sediment drift enhanced by the winter monsoon bars were successively formed on the wider side of the bifurcated river mouths and subsequently accreted seaward being stabilized by tide effects to result in shore perpendicular elongate delta plains our work based on the mekong delta demonstrates for the fi rst time that bar emergence is a key process in the long term evolution of mixed tide and wave dominated deltas

the chronology of a sediment core from incised valley of the yangtze river delta comparative osl and ams 14 c dating abstract optically stimulated luminescence osl dating has gained increased use in dating deltatic deposits however its application can be hindered by the problem of incomplete bleaching to address this limitation we test the single grain osl method for the first time in the yangtze river delta a total of eight osl and 14 ams 14c samples were obtained from a 50 8 m long sediment core from the incised valley of the delta quartz extracted from eight osl samples from the core was first measured with small multi grain aliquots using medium 45 63 m and coarse grained 90 125 m or 150 180 m fractions to test the internal consistency of their respective ages the results showed that four of five medium grained quartz samples appeared to be well bleached in contrast the coarse grained quartz samples revealed poor bleaching except for two samples from the delta front facies five coarse grained quartz osl samples were further analyzed using a single grain osl technique only 0 5 0 7 of the grains passed the rejection criteria single grain osl dating is appropriate for age determination of coarse grained sediments which have been affected by incomplete bleaching however it consumes a lot of instrument time central and minimum age models cam and mam were used to calculate the burial age of the samples mam ages fit best in the stratigraphic sequence small aliquots are recommended as effective in identifying incomplete bleaching for medium or coarse grained quartz a comparison of ams 14c dates and osl ages shows that 14c values are 1 3 ka older than osl ages according to the osl ages core sd experienced rapid accumulation 10 8 ka and in the last 2 ka the former is linked to rapid sea level rise in early holocene while the latter is primarily due to the migration of depo center towards the core site rather than entirely increased sediment delivery caused by human activities

depocenter shift and en echelon shoal development in the pre holocene incised valley of the yangtze delta china abstract this study establishes a holocene sedimentation model for the incised valley of the yangtze delta based on key information taken from existing literature and new cores collected for this study distinctive sedimentary processes and mechanisms operating in the incised valley were revealed 1 the significant role of a pre holocene incised valley on which the holocene funnel shaped bay was established in forming the topography of the present river mouth 2 the backstepping migration of the depocenter in association with tidally dominated sandy shoals developed in the early middle holocene followed by fluvially tidally dominated progradation during the mid late holocene 3 the model of depocenter shift characterized by en echelon sandy shoals in the incised valley revealing stepwise migration from transgressive to retrogressive sedimentation in the holocene and 4 the dextral diversion of the river mouth controlled by strong tidal sedimentation in the valley and the coriolis driven tidal sedimentation off the valley throughout the holocene our results further show that the sediment in the holocene valley was characterized by an upward increase in foraminiferal abundance this is a reversal of the usual pattern to the holocene marine transgression indicating a unique depositional setting in the valley presumably due to higher turbidity and poor preservation caused by strong tidal currents

early middle miocene stratigraphic turning points in the alicante region se spain reflections of western mediterranean plate tectonic reorganizations abstract the paper concerns the miocene deposits of the alicante region se spain which forms part of the prebetic and intermediate units representing the former southern passive margin of the iberian continent from the late jurassic up to the miocene the alicante region was the scene of a facies distribution with more continental lagoonal or shallow marine conditions in the north and northwest and more open or deeper marine in the south and southeast the early middle miocene deposits can be divided in three sedimentary cycles each one controlled by a different tectonic regime cycle i aquitanian is deposits after a block faulting phase at about 25 ma related to the formation of the ligurian and balearic troughs cycle ii burdigalian early langhian is separated from first cycle sediments by a complete reorientation of palaeogeography at 19 5 ma due to the collision of iberia with africa the southern part of the region is folded and uplifted and separated from a northern emerged area by a trough cycle iii late langhian serravallian is controlled by strike slip movements caused by the continuing convergence between africa and europe and resulting in the development of a new set of basins at 15 5 ma at the middle late miocene boundary the alicante region emerges thus younger important tectonics could not be dated our results are in conflict with several recent plate tectonic models for the miocene history of the western mediterranean where the internal betic zone is placed juxtaposed to the alicante region prior to the burdigalian

pillow beds a new type of seismites an example from an oligocene turbidite fan complex alicante spain a new type of soft sediment deformed beds termed pillow beds originally a packet of calcarenitic turbidites show sand in sand loading with plane lower and upper surfaces the pillow beds have some resemblance to ball and pillow structures and they are considered to have formed as a result of dewatering the pillow beds are oligocene in age and are part of turbidite lobes in a submarine fan system which was fed through a canyon along the southern border of the ancient iberian continent three hypotheses may explain their occurrence overloading sliding or seismic shock a seismic origin is preferrred on the basis of the flat undeformed lower surface of the pillow beds excluding dewatering of and loading into the previously deposited beds furthermore the pillow bed structures are related to grain size and may show repetitions thus excluding sliding the scale and nature of the pillow beds suggest they could be the result of an earthquake with a magnitude of 6 7 on the richter scale

magnetostratigraphy and luminescence dating on a sedimentary sequence from northern east china sea constraints on evolutionary history of eastern marginal seas of china since the early pleistocene owing to the large and increasing population density in low lying coastal regions even small changes in sea level can have substantial societal and economic impacts alternations of terrestrial and marine sediments deposited in coastal areas or continental shelves are important and effective indicators of sea level changes and thus have been widely studied in the marginal seas of china over the past 30 years however sea level change results from not only eustatic factors but also tectonic activity the zhe min or zhejiang fujian uplift zmu was such an important factor in geomorphology and formed a barrier preventing entry of sea water into the northern marginal seas of china but its quaternary history is poorly known