tectonic and structural evolution of gough volcano a volcanological model abstract morphostructural stratigraphic and tectonic data indicate that the evolution of gough volcano is similar to other oceanic intraplate volcanoes is older than 1 ma and is related to a transform fault at least six evolutionary stages can be distinguished within two major magmatostructural periods dominated by basaltic and trachytic magmas respectively the basaltic shield volcano is characterized by a curved elongated shape in plan and a rift zone with a high density of dykes combined with a radial intrusive system the latter is interpreted as being fed by a magma chamber some 4 km below the surface the activity of the volcano became more centralized at the end of the basaltic period and its slopes became steeper this corresponds to the development of a shallower and narrower central conduit in the edifice the basaltic period was terminated by formation of a shield caldera related to the 4 km deep magma chamber the term shield caldera is used for a collapse structure that is postmagmatic large in comparison with the diameter of the volcano and delimited by normal faults that do not show a closed circular pattern but rather a series of arcs in contrast summit calderas are defined as smaller circular shaped centrally situated synmagmatic features related to a central shallow column during the basaltic period landslides were generated on the flanks of the edifice as a result of slope stability factors which are not easy to determine at present and dynamic factors among which the intrusion of magma along a curved zone certainly played a major role the trachytic period is characterized by comparatively rare pyroclastic deposits and a large volume of thick flows extruded from domes these extrusions as well as plugs formed from vertical cylindrical columns of magma rising from shallow individual magma pockets fed by the main reservoir

tracing tsunami signatures of the ad 551 and ad 1303 tsunamis at the gulf of kyparissia peloponnese greece using direct push in situ sensing techniques combined with geophysical studies

clinoforms and clinoform systems review and dynamic classification scheme for shorelines subaqueous deltas shelf edges and continental margins abstract clinoforms are inclined and normally basinward dipping horizons developed over a range of spatial and temporal scales in both siliciclastic and carbonatic systems the study of clinoform successions underpins sequence stratigraphy and all efforts to reconstruct the relative partitioning of reservoir seal and source rocks along shoreline to basin floor profiles here we review clinoform research and propose a more systematic description and classification of clinoforms this is a crucial step to improve predictions of facies and lithology distribution within shoreline to continental shelf and abyssal plain successions together with the genesis drivers and dynamics of their constituent sedimentary units four basic clinoform types are here distinguished in delta shorelines lacustrine and marine environments on the basis of their overall spatial and temporal scale morphology outbuilding dynamic and geodynamic and depositional setting 1 2 delta scale clinoforms which in turns are sub divided into shoreline and delta scale subaqueous clinoforms 3 shelf edge clinoforms and 4 continental margin clinoforms delta scale clinoform sets are tens of metres high and typically represent 1 103 kyr with progradation rates ranging from 1 000 100 000 m kyr for shorelines and subaerial deltas to 100 20 000 m kyr for subaqueous deltas shelf edge clinoform sets are hundreds of metres high and are nucleated and accreted in 0 1 20 myr usual progradation rates of 1 100 m kyr by successive cross shelf transits of delta scale clinoforms continental margin clinoform sets are thousands of metres high hallmark key geodynamic crustal boundaries e g continent ocean transition and slowly prograde basinwards in ca 5 100 myr with typical rates of 0 1 10 m kyr as a consequence of the very different progradation rates and of the difficulty of large scale clinothems to backstep during transgressions shorelines are the most dynamic clinoforms with regards to position continental margins the least and shelf edges are intermediate shortly after a transgression therefore the four clinoform types may prograde synchronously along shoreline to abyssal plain transects forming compound clinoform systems during the subsequent regressive cycle however due to the dissimilarity in progradation rates different clinoform types will normally merge progressively with each other giving rise to hybrid clinoforms e g shelf edge deltas and fewer depositional breaks in slope are distinguished along a single shoreline to abyssal plain transect overall all clinoform systems are the result of the dynamic evolution of compound and hybrid clinoforms along a temporal and spatial continuum regulated by the cyclical backstepping of the smaller scale system within natural progradational retrogradational cycles of larger scale clinothem outbuilding all clinothem types may show either an accretionary active or draping passive style depending on the proximity to the sediment source draping clinothems are nearly always composed of condensed fine grained sediments while actively accreting clinothems can be composed of predominantly coarse grained i e reservoir forming or predominantly fine grained i e non reservoir lithotypes a novel hierarchical classification scheme for both recent and ancient clinoforms is here proposed consisting of 12 classes the four basic clinoform types delta scale shoreline delta scale subaqueous shelf edge and continental margin are sub divided into eight accretionary active and draping passive sub types 8 division each accretionary sub type is then sub divided into a sandstone prone and mudstone prone variant 12 division which can be at least tentatively predicted on the basis of the clinoform morphology even in the absence of direct stratigraphic logs

late pleistocene and holocene sedimentary facies on the ebro continental shelf abstract late pleistocene holocene history of the ebro continental shelf of northeastern spain is recorded in two main sedimentary units 1 a lower transgressive unit that covers the shelf and is exposed on the outer shelf south of 40 40 n and 2 an upper progradational prodeltaic unit that borders the ebro delta and extends southward along the inner shelf the lower transgressive unit includes a large linear shoal found at a water depth of 90 m and hardground mounds at water depths of 70 80 m some patches of earlier pleistocene prodelta mud remain also exposed or covered by a thin veneer of transgressive sand on the northern outer shelf this relict sand sheet is 2 3 m thick and contains 9000 12 500 yr old oyster and other shells at water depths of 78 88 m the upper prodelta unit covers most of the inner shelf from water depths of 20 80 m and extends from the present ebro river delta to an area to the southwest where the unit progressively thins and narrows interpretation of high resolution seismic reflection data shows the following facies occurring progressively offshore 1 a thick stratified facies with thin progradational foresets beds 2 a faintly laminated facies with sparse reflectors of low continuity and 3 a thin transparent bottomset facies underlain by a prominent flat lying reflector deposition in the northern half of the prodelta began as soon as the shoreline transgressed over the mid shelf but progradation of the southern half did not begin until about 1000 3000 yrs after the transgression a classic deltaic progradational sequence is shown in the ebro prodelta mud by 1 gradation of seismic facies away from the delta 2 coarsening upward sequences near the delta and fining upward sequences in the distal mud belt deposits and 3 thin storm sand layers and shell lags in the nearshore stratified facies the boundaries of the prodeltaic unit are controlled by increased current speeds on the outer shelf where the shelf narrows and by development of the shoreface sand body resulting from shoaling waves on the inner shelf

ignimbrites of basaltic andesite and andesite compositions from tanna new hebrides arc tanna island is part of a large volcanic complex mainly subsided below sea level on land two series of hydroclastic deposits and ignimbrites overlie the subaerial remains of a basal mainly effusive volcano the older tanna ignimbrite series oti late pliocene or pleistocene in age consists of ash flows and ash and scoria flow deposits associated with fallout tephra layers overlain by indurated pumice flow deposits phreatomagmatic features are a constant characteristic of these tuffs the younger late pleistocene pyroclastics the siwi sequence show basal phreatomagmatic deposits overlain by two successive flow units each comprising a densely welded layer and a nonwelded ash flow deposit whole rock analyses of 17 juvenile clasts from the two sequences vitric blocks from the phreatomagmatic deposits welded blocks scoriaceous bombs and pumices from the ignimbrites show basaltic andesite and andesite compositions sio2 53 60 in addition 296 microprobe analyses of glasses in these clasts show a wide compositional range from 51 to 69 sio2 dominant compositions at 54 56 58 5 and 61 62 sio2 characterize the glass from the oti glass compositions in the lower phreatomagmatic deposits from the siwi sequence also show multimodal distribution with peaks at sio2 55 57 5 61 62 and 64 whereas the upper ignimbrite has a predominant composition at 61 62 sio2 in both cases mineralogical data and crystal fractionation models suggest that these compositions represent the magmatic signature of a voluminous layered chamber the compositional gradient of which is the result of fractional crystallization during two major eruptive stages probably related to two caldera collapses the oti and siwi ignimbrites represent large outpourings from these magmatic reservoirs the successive eruptive dynamics from phreatomagmatic to plinian emphasize the role of water in initiating the eruptions without which the mafic and intermediate magmas probably would not have erupted

worldwide initiation of holocene marine deltas by deceleration of sea level rise radiocarbon dated deltaic sequences of holocene age from different parts of the world began to accumulate within a restricted time range from about 8500 to 6500 years ago evaluation of major delta processes indicates that deceleration in sea level rise was the key factor in holocene delta formation within many deltas there is as much as a 2000 year age range between basal deposits in seaward and landward cores this age difference records the progressive landward migration of near mean sea level depositional environments during the lower to mid holocene establishment of a chronostratigraphic framework for holocene delta development provides a fundamental global baseline for distinguishing sea level change from vertical land motion by tectonism and isostasy and for evaluating rates of future marine incursion into low lying deltas

the depositional architecture and facies variability of shelf deltas in the eocene battfjellet formation nathorst land spitsbergen deltas are commonly classified according to their plan view morphology as either river dominated tide dominated or wave dominated however most deltas form under the mixed influence of these processes commonly with laterally varying process regimes it has also become clear that there is a mismatch between the plan view morphology and internal facies composition in some deltas combined outcrop and subsurface data from the eocene battfjellet formation spitsbergen provide an example of ancient shelf deltas that formed under mixed influence internally these shelf deltas are characterized by wave dominated facies that are normally associated with strike extensive nearly linear shoreline sandstones however the formation comprises partially overlapping sandstone bodies of limited lateral extent 20 km in any direction this stacking pattern is attributed to frequent autogenic lobe switching that caused localized and rapid transgressions such processes typify fluvial dominated deltas and occur less commonly in wave dominated ones thus there is an apparent mismatch between inferred plan view morphology and internal facies composition it is argued that the battfjellet deltas were flood dominated and prograded mainly during periods of high fluvial discharge however reworking of the fluvial flood facies by fair weather and storm waves as well as longshore currents resulted in a wave dominated facies character delta lobes undergoing auto retreat were particularly prone to reworking by basinal processes including tidal currents it is suggested that repeated delta progradation from inner shelf settings towards the outer shelf and shelf edge was aided by high sediment supply rather than relative falls in sea level as previously suggested this interpretation is supported by i the lack of major facies dislocations and extensive sub aerial unconformities and ii an overall relative rise in sea level as evidenced by an overall low angle 0 8 to 1 2 ascending shoreline trajectory the latter results from the combined effect of basin subsidence eustatic highstand and sediment compaction

the ebro continental shelf quaternary seismic stratigraphy and growth patterns abstract single channel seismic reflection profiles on the ebro shelf and upper slope between cap salou and the columbretes islands have been interpreted to outline the quarternary shelf evolution in this deltaic area three types of unconformity surfaces can be differentiated in the seismic records type 1 and 2 unconformities and toplap surfaces these surfaces are the stratigraphic expression of the difference between rate of eustatic sea level fall and subsidence on the outer shelf a type 1 unconformity forms if the rate of eustatic sea level fall is the more rapid a type 2 unconformity forms if subsidence is faster and toplap forms if subsidence and eustatic sea level fall are equal thirteen stratigraphic units can be differentiated on the basis of unconformities based on their relative location on the shelf these units are subdivided into inner and outer units the inner units occur on the inner and middle shelf and are characterized by an underlying transgressive surface while the outer units extend onto the middle to outer shelf and upper slope and show unconformities at their bases the inner units are interpreted to be stacked transgressive and highstand systems tracts bounded by a maximum flooding surface the outer units correspond to shelf deltas and shelf margin deltas that prograded southward and seaward over an unconformity in relatively stable water depths when sea level fall was compensated for by subsidence the progradation of these units ends with an episode of generalized erosion of the shelf and canyon cutting across the new shelf edge the growth pattern of the northern ebro shelf is characterized by important hiatuses condensed stratigraphic sections and units which are older than those on the southern shelf the depositional processes were mainly controlled by eustatic sea level oscillations subsidence and changes in sediment supply the subsidence during the late pleistocene was sufficient to compensate for the sea level falls and allow the development of shelf deltas and shelf margin deltas on the middle and outer shelf during low sea level stands

post calabrian sequence stratigraphy of the northwestern alboran sea southwestern mediterranean abstract the post calabrian sedimentary column of the northwestern alboran sea comprises three depositional sequences the two older depositional sequences are defined by lowstand systems tracts shelf margin deltas slope base of slope and basin deposits and the guadiaro channel levee complex in contrast the most recent depositional sequence also includes transgressive relict shelf facies and high stand the guadalmedina guadalhorce prodelta and hemipelagic facies systems tracts the stratigraphic architecture of these depositional sequences is controlled by the synchronism between high frequency sea level changes variations in sediment supply and sedimentary processes the configuration of the depositional sequences is variable and their distribution is complex as a result of the relative importance played by sea level changes and tectonism through the area the sequence boundaries are represented by polygenetic surfaces in the proximal margin and by monogenetic surfaces in the distal margin and basin each polygenetic surface results from the interaction between the sequence boundary with the lowstand erosional truncation surface and the transgressive surface both developed during the previous sea level cycle the monogenetic surfaces correspond to unconformities and their correlative conformities formed during sea level lowstands this pattern of depositional sequences developed in the margin and basin of the northwestern alboran sea shows differences with the exxon sequence stratigraphy model as traditionally applied sea level change control is essentially recognized through lowstand systems tracts and sequence boundary coincides with lowstand erosional truncation surface and transgressive surface both developed during the previous sea level cycle

evidence for holocene sea level and climate change from almenara marsh western mediterranean in the almenara marsh western mediterranean four cores were analyzed to establish the relationship between the marsh record of the almenara marshlands and the environmental factors responsible for its evolution during the holocene one hundred and eighty six samples were collected for sedimentologic and paleontological study 63 for biomarker analysis 5 for amino acid racemization aar dating and 5 for 14 c dating litho and biofacies analyses identified distinct paleoenvironments with the presence of a marsh environment alternating with inputs of alluvial material and marine sediments biomarkers indicated the constant presence of terrestrial herbaceous plants together with a variable development of aquatic macrophytes during the holocene transgression the almenara marsh was occupied by oligohaline marsh facies with an oscillating water level and peat formation which was established at the bottom of the record at 7570 cal yr bp and persisted until 3100 780 yr aar maximum surface flooding occurred at 5480 cal yr bp registered 450m from the current coastline at least three peat beds dated with 14 c dating and aar correlated with bond episode 5900 cal yr bp and wanner episodes 4800 4500 and 3300 3500 cal yr bp cycles and thus correspond to a regional model that affected the northern hemisphere

gplates building a virtual earth through deep time gplates is an open source cross platform plate tectonic geographic information system enabling the interactive manipulation of plate tectonic reconstructions and the visualization of geodata through geological time gplates allows the building of topological plate models representing the mosaic of evolving plate boundary networks through time useful for computing plate velocity fields as surface boundary conditions for mantle convection models and for investigating physical and chemical exchanges of material between the surface and the deep earth along tectonic plate boundaries the ability of gplates to visualize subsurface 3 d scalar fields together with traditional geological surface data enables researchers to analyze their relationships through geological time in a common plate tectonic reference frame to achieve this a hierarchical cube map framework is used for rendering reconstructed surface raster data to support the rendering of subsurface 3 d scalar fields using graphics hardware accelerated ray tracing techniques gplates enables the construction of plate deformation zones regions combining extension compression and shearing that accommodate the relative motion between rigid blocks users can explore how strain rates stretching shortening factors and crustal thickness evolve through space and time and interactively update the kinematics associated with deformation where data sets described by geometries points lines or polygons fall within deformation regions the deformation can be applied to these geometries together these tools allow users to build virtual earth models that quantitatively describe continental assembly fragmentation and dispersal and are interoperable with many other mapping and modeling tools enabling applications in tectonics geodynamics basin evolution orogenesis deep earth resource exploration paleobiology paleoceanography and paleoclimate

oxygen isotopes and sea level from the time that detailed oxygen isotope records derived from foraminifera living in the constant temperature environment of the abyssal ocean became available there has been a discrepancy between the ice volume record that these records imply and that derived from the altitude of dated coral terraces around the world here we re examine the data and conclude that the temperature of the abyssal ocean has been an actively varying component of the climate system

revised geology age and vertebrate diversity of the dinosaur bearing griman creek formation cenomanian lightning ridge new south wales australia abstract the mid cretaceous griman creek formation gcf which crops out near the town of lightning ridge in the surat basin of north central new south wales australia is noteworthy for its opalised vertebrate fauna the fossil assemblage comprises remains of aspidorhynchid teleosts lamniform chondrichthyans dipnoans chelid and possible meiolaniform turtles leptocleidid like and possible elasmosaurid plesiosaurians anhanguerian pterosaurs titanosauriform sauropods megaraptoran theropods ankylosaurians several forms of non iguanodontian and iguanodontian ornithopods crocodylomorphs enantiornithine birds and stem and true monotremes making it one of the most diverse mid cretaceous terrestrial vertebrate faunas in australia a detailed stratigraphic survey of twenty subterranean opal mines provides new information on the geology age and palaeoenvironment of the main fossil bearing beds vertebrate remains derive from the finch clay facies laterally extensive but discontinuous lenses of claystone that likely accumulated relatively rapidly in near coastal but freshwater embayments i e lagoonal conditions and probably represent a single roughly contemporaneous fauna u pb age dating of detrital zircons extracted from a distinct layer of volcanogenic claystone immediately overlying one of the opalised fossil bearing layers yields a maximum depositional age of 100 2 96 6 ma these new dates confirm an early to mid cenomanian age for the fauna rather than albian as has been reported previously the gcf at lightning ridge is therefore equivalent to the middle part of the winton formation queensland and several million years older than the sauropod dominated fauna at winton

man s influence on the erosion and transport of sediment by asian rivers the yellow river huanghe example during the holocene sediment input from the yellow river to the yellow sea and adjacent areas has amounted to about 3000 km 3 detailed records from river gauging stations over the past 70 yrs together with estimates based on earlier historic records suggest that the river has contributed 2300 km 3 of sediment during the last 2300 yrs an average discharge of 1 km 3 yr 1 x 10 9 t yr prior to extensive agricultural use of the loess plateau in northern china beginning about 200 bc therefore the river s load must have been about 0 1 km 3 yr an order of magnitude lower than that at present a broad delta 20 m below sea level suggests that early holocene rates were higher than the pre agricultural average and therefore that middle holocene loads were low

barremian cenomanian palaeotemperatures for australian seas based on new oxygen isotope data from belemnite rostra oxygen isotope ratio 18o data are presented for 55 belemnite rostra specimens of late aptian albian age from the great artesian basin of eastern australia and of late barremian early cenomanian age from the carnarvon basin of western australia the belemnites were carefully screened for diagenesis by means of catholuminescence and trace element geochemistry the 18o record for the carnarvon basin palaeolatitude 40 s is interpreted to show a long term warming trend from 10 c in the aptian to a maximum of 15 c in the cenomanian shorter term fluctuations in the mid albian are also apparent data from the great artesian basin palaeolatitude 40 55 s show a wider 18o range which is attributed to the epeiric sea context of this sample set the larger range in 18o is interpreted to reflect differing water mass characteristics due possibly to a combination of variable freshwater dilution seasonal temperature fluctuations and isotopic exchange between seawater and pyroclastic sediment within the epeiric sea nevertheless the aptian albian 18o trends are still comparable to those obtained for the carnarvon basin the inferred palaeotemperature trends for the australian sedimentary basins are consistent with records from other regions and demonstrate that broadly synchronous palaeotemperature variations can be recognised on a global scale during the cretaceous although our data do indeed show cool temperatures within the aptian and the albian reaching a low of 10 c these estimates are somewhat warmer than those based on glendonite genesis however the exact position of the glendonite bearing and dropstone rich parts of the bulldog shale is poorly constrained with respect to our isotope data and the warmest temperatures were of late albian and early cenomanian age however to conform to greenhouse warmth and equability and to achieve parity with other palaeotemperature records the 18oseawater estimate of 1 0 that is generally used for cretaceous oceans in an ice free world needs to be adjusted to a slightly higher value

new evidence on the evolution of the po delta coastal plain during the holocene abstract the po coastal plain dominated by the po and adige rivers deltaic systems is characterized by beach ridges which mark successive positions of the coastline during the holocene the most evident of these ridges are the most recent ones their dating is mainly based on archaeological and historical data the complex formed by some of the most prominent beach ridges was previously considered by experts to be the first post glacial shoreline this shoreline enclosed a single lagoonal system comprising the lagoon of venice and the delta of the main rivers more recent studies have instead allowed us to recognize other beach ridges older than this one these beach ridges are partially or totally buried by alluvial sediments belonging we believe to active subboreal shorelines additionally other studies we are now carrying out such as the geomorphologic map of the po plain and the venetian lagoonal system project have allowed the identification of older buried intertidal facies this work proposes a progradational model mainly developed by the building of the marine deltas including episodic or discontinuous lagoonal environments in opposition to the continuous lagoonal system model described up to now

tectonics of marion and prince edward volcanoes indian ocean result of regional control and edifice dynamics abstract a structural analysis of marion and prince edward islands shows two kinds of tectonic control 1 1 regional tectonics the parallelism between a common structural trend on these two islands characterized by a n20 e and e w association the morphology of the underlying submarine plateau the structure of the sea floor and the fact that both islands display the same rhythm of activity all suggest that these volcanoes all resulted from the reactivation of oceanic lithosphere paleostructures 2 2 edifice tectonics the marion cone is better suited for a study of edifice dynamics than prince edward volcano of which about 80 has subsided below sea level marion is composed of a main volcanic center and a rift zone on which a second volcanic center developed it is proposed that the weight of the edifice and the geometry of the feeding and intrusive system emanating from small relatively deep magma chambers are responsible for the peculiar dynamic properties of the marion edifice the latter are the absence of a caldera a low rate of activity and numerous flank landslides a three fold classification of the stability of volcanoes based on structural patterns is proposed

paleobiological and sedimentological evidence of pleistocene holocene hiatuses and ironstone formation at the pontian islands shelfbreak italy abstract iron rich hardgrounds were grabbed near the shelfbreak ne ventotene and sw ponza at water depths of 119 and 141 m respectively these 1 to 3 cm thick ironstone layers formed at about the pleistocene holocene boundary during rapid sea level rise which began about 16 000 years ago and within about 8000 years brought the bottom of the shelf from a water depth of less than 30 100 m or more a rapid vertical transition from circalittoral deposits characterized by a coastal detritic community with calcareous algae to ironstones rich in iron managanese pisoids or glaucony and containing planktonic foraminifera siliceous sponge spicules and echinoderm remains indicates sediment starvation during rapid drowning of the shelf the crisis of the sedimentary system and the local ironstone formation at sites of favourable morphology were triggered by major paleogeographic changes during final deglaciation at the close of the pleistocene leading to modified circulation patterns and chemistry of sea water reduced carbonate productivity below the photic zone and strong activity of northward directed tyrrhenian currents intruding onto the outer shelf abundance of organic matter transported from the drowned volcanic islands and diminished oxygenation due to both increasing water depth and sluggish vertical circulation were responsible for local reducing micro environments as testified by the formation of pyrite leaching of carbonate bioclasts and growth of microbial mats offshore sedimentation did not resume until the last 2000 4000 years when the deeper water and finer grained ponza glauconitic ironstone was covered by a thin veneer of silty clay deposited on the uppermost slope beneath the mudline the shallower and coarser grained ventotene winnowed pisoidal hardground instead is probably still forming today under the action of strong northward directed marine currents sweeping the shelfbreak free of sediment

a simple approach to define holocene sequence stratigraphy using borehole and cone penetration test data cone penetration testing has been widely used since the 1950s for determining the subsurface geotechnical conditions of unconsolidated sediments this paper highlights the potential value of cone penetration testing as an aid to define the stratigraphic structure of holocene sedimentary deposits by calibrating cone penetration test logs with adjacent borehole logs and by utilizing all the available information produced during geotechnical surveying stratigraphic models that accurately describe the vertical and lateral boundaries as well as the stacking pattern of late quaternary systems can be constructed the widespread application and technical simplicity of cone penetration testing combined with simple data interpretation via correlation with adjacent borehole logs yield a useful and inexpensive tool for sedimentological investigations this methodology is illustrated using data from 36 cone penetration tests and 11 boreholes on the holocene deltaic plain of the aliakmon river greece sedimentological and stratigraphic information from core log correlations the spatial distribution of cone penetration test parameters sediment grain size and per cent concentration of organic matter are utilized the results suggest that in sequence stratigraphic terms the delta is divided into a lowstand systems tract composed by fluvial gravels and sands u0 of late pleistocene age as well as from red oxidized clays and a transgressive systems tract represented by fluvial channel sands u1 overlain by a thin transgressive sand sheet of coastal origin u2 characterized by fining upward trends the highstand systems tract is constituted by a variety of stratigraphic units u3 to u7 and depositional environments characterized by coarsening upward sequences representing both aggradational and progradational facies and dominated by the presence of three prograding wedges detailed definition of the thickness vertical boundaries and stacking pattern of the resolved stratigraphic units presented as a two dimensional stratigraphic model demonstrates the applicability of the proposed method

high resolution seismic reflection profiles for the reconstruction of postglacial transgressive shorelines an example from greece abstract in 1982 we carried out a shallow penetration high resolution seismic profiling study on the shelf of the southern argolid peloponnesos greece to identify and map the shores of the late pleistocene and holocene and to establish their coastal environments portable equipment and a local boat were used the lowest glacial shore occurs at 115 to 118 m within the range of global values the subsequent rise across the distinct old land surface left behind many shore features scaps beaches and beach ridges channels and lagoons now buried under a few meters of post transgressive deposits these features cluster at a small number of depths below present sea level suggesting that the rise of the sea usually too fast to leave an imprint was episodically interrupted by brief stillstands or even temporary reversals of climatic or tectonic origin the clusters can be roughly dated with reference to a global sea level rise curve after 6000 yr b p sparse archaeological data establish a local curve the seismic profiling technique convenient and not costly holds promise for the identification of postglacial shores elsewhere prior to sampling for dating it has wide application for environmental reconstructions of vanished coastal zones as a basis for prehistoric resource assessments these applications are illustrated with examples from this study

the timing and evolution of the post glacial transgression across the sea of marmara shelf south of istanbul high resolution reflection seismic profiles with core analyses of sedimentary sequence near the sea of marmara som entrance to the strait of istanbul soi bosphorus provide detailed record of sealevel changes since the late glacial maximum lgm the sequence is deposited over the lgm erosional surface at a maximum depth of 105 m it includes seven seismic units that can be confidently correlated with 14c dated sedimentary units in the cores unit 6 represents levee deposits of the paleo soi channel that was deposited by a black sea outflow during 11 2 10 6 kyr bp the reflection surfaces at base of unit 5 and 4 correspond to wave cut terraces at 71and 63 m respectively and are estimated to be 10 6 and 9 8 kyr bp the seismic unit 2 overlaying a mud drape unit 3 comprises deltaic sediments that was deposited during 6 400 3200 yr 14c bp isopach map and

a new interpolation method to measure delta evolution and sediment flux application to the late holocene coastal plain of the argens river in the western mediterranean abstract rapid environmental changes along the mediterranean coasts influenced the sedimentary dynamics shoreline position and human settlements in deltaic areas over the last millennia an innovative and multiproxy approach using geostatistical modelling was developed to estimate geomorphic evolution and sediment fluxes in deltaic areas while palaeoecological conditions and environmental changes were assessed from geochemistry and cluster analyses of molluscan fauna this method was applied to the coastal plain of the argens river in southern france depositional environments of prodelta delta front river channel floodplain marsh and abandoned channel were identified from the study of facies associations the late holocene sediment flux in the argens river bayhead delta ranged from 15 800 2300 to 52 000 8500 m3 yr 1 the highest rate of sediment deposition between 2500 and 2000 cal yr bp was associated with increased river flooding in southeastern france a general decrease in subaqueous sediment flux over the past 2500 years was primarily controlled by a decrease in accommodation space and delta slope from 500 to 0 cal yr bp a sharp increase in subaerial sediment flux probably due to hydroclimatic change was contemporaneous with a period of high flood frequency during the little ice age a southward shift of the north atlantic westerlies combined with either a negative phase of the east atlantic west russian pattern or a negative phase of the east atlantic pattern coupled to a northward migration of the intertropical convergence zone could have led to increased fluvial activity in the lower argens valley during the late holocene

reconstruction of sediment supply from mass accumulation rates in the northern adriatic basin italy over the past 19 000 years reconstruction of sediment supply is hampered by the incompleteness of the stratigraphic record this problem may be partly circumvented by studying mass accumulation rates in closed systems i e basins in which no sediment has bypassed the site of deposition over the time interval of interest we present time averaged basin wide mass accumulation rates and their associated uncertainties from a well documented closed basin the northern adriatic basin italy spanning the time interval from 19 ka b p to the present the sediment masses of five basin wide lithosomes and their associated uncertainties are derived by means of stochastic simulation using highresolution seismic data porosity profiles and radiocarbon datings this study demonstrates that inferring rates of sediment supply from conformity bounded stratigraphic units is feasible as indicated by the excellent agreement of our results of mass accumulation over the past 400 years with two independently derived estimates formation of the stratigraphic record is not an instantaneous process by comparing spatial patterns of mass accumulation rates on three different timescales decadal centennial and millennial we demonstrate a low preservation potential of sediments presently accumulating near the coast and a continuous cross shore and alongshore sediment transport regime the change from transient to persistent accumulation patterns in the highstand systems tract of the northern adriatic basin occurs at the centennial to millennial timescale intrabasinal erosion and recycling of sediments obscure the relation between rates of sediment supply and net basin wide mass accumulation which limits the amount of information that can be extracted from the stratigraphic record hence a mismatch between rates of sediment supply and accumulation rates is expected for unconformity bounded sequence stratigraphic units given the uncertainties associated with our estimates we are unable to reject the hypothesis that net basin wide mass accumulation rates have been constant over the time interval of 19 000 years at a 10 significance level

shelf sequence and characteristic bounding surfaces in a wave dominated setting latest pleistocene holocene examples from northeast japan abstract this paper presents modern models for coastal to shelf sequences in a microtidal and wave dominated setting based on detailed analyses of latest pleistocene holocene sequences on the pacific side of northeast japan the latest pleistocene holocene sequences on the pacific side of northeast japan created in response to sea level changes for the last 30 kyr can be assigned to lowstand transgressive and highstand systems tracts related to sea level changes and show characteristic bounding surfaces and depositional systems these basically support the sequence architecture model of vail however transgression and regression occurred almost simultaneously with rise and fall of sea level in the study areas and so inflection points of sea level curves where the absolute slope or the rate of change is greatest are less significant for these high frequency sequences the characteristic bounding surfaces are a sequence boundary a transgressive surface which is the boundary between the lowstand and the transgressive systems tracts a ravinement surface which is found mainly in deposits of the transgressive systems tract and a maximum flooding surface which is the boundary between the transgressive and the highstand systems tracts the sequence boundary was created in response to falling sea level fluvial entrenchment shifted seaward with falling sea level therefore the boundary is a time transgressive unconformity and is not an isochronous boundary the transgressive surface is a nearby isochronous boundary that occurred when the shoreline had started to move landward from its maximum seaward excursion the ravinement surface is a diachronous surface created by shoreface erosion during transgression the shoreface erosion shifted landward with rising sea level and so the erosion surface created is time transgressive this surface is the most distinct bounding surface in the shelf sequence these characteristics of the bounding surfaces support and clarify the model of thorne and swift 1991 the transgressive systems tract on the shelf can be divided into two backstepping wedges separated by the ravinement surface the lower wedge consists of coastal plain and fluvial systems and the upper wedge is composed of transgressive sand and or sand ridges both the wedges show a backstepping depositional pattern which can be recognized in seismic records and cores these wedges correspond to the backstep backbarrier wedge and backstep shelf wedge of thorne and swift 1991 respectively

relative sea levels and coastal sedimentation in southeast australia in the holocene abstract in recent years australian studies of relative sea level change have shown reasonable consistency on the termination date of the postglacial marine transgression at c 6 500 14c years bp the following stillstand period has been characterized in some regions by a slight falling trend from a high stand or in other areas by a level not easily distinguished from the present the latter situation occurs on the embayed coast of new south wales here studies of depositional environments and sequences within bed rock embayments have linked the holocene sea level history to patterns of sedimentation on the inner shelf in bay barriers and in estuaries deposition of quartz rich sand in shoreface flood tidal delta and backbarrier environments occurred during the marine transgre sion and the subsequent stillstand shell fragments from these deposits have been radiocarbon dated shoreline displacement continues to the present day partly in response to changes in availability of sand in the shoreface zone and partly in response to variations in regional storminess patterns a nd the great shroud of the sea rolled on as it rolled five thousand years ago herman melville moby dick

a jurassic ornithischian dinosaur from siberia with both feathers and scales middle jurassic to early cretaceous deposits from northeastern china have yielded varied theropod dinosaurs bearing feathers filamentous integumentary structures have also been described in ornithischian dinosaurs but whether these filaments can be regarded as part of the evolutionary lineage toward feathers remains controversial here we describe a new basal neornithischian dinosaur from the jurassic of siberia with small scales around the distal hindlimb larger imbricated scales around the tail monofilaments around the head and the thorax and more complex featherlike structures around the humerus the femur and the tibia the discovery of these branched integumentary structures outside theropods suggests that featherlike structures coexisted with scales and were potentially widespread among the entire dinosaur clade feathers may thus have been present in the earliest dinosaurs

late quaternary deltaic lowstand wedges on the rhone continental shelf france abstract shallow seismic profiles on the rhone continental shelf have shown the existence of stacked progradational lowstand wedges on the outer shelf accumulated during late quaternary glacioeustatic lowstands the wedges are bounded by sharp to erosional sequence boundaries and onlap onto the middle shelf the thickness of individual wedges attains 50 meters at the shelf edge where they are sheared by slumping the wedges exhibit well developed progradational clinoforms episodically interrupted by internal unconformities on which there is a downward shift of the succeeding clinoforms these represent small scale in the order of a few meters falls in sea level during the quaternary eustatic cycles the durations of the stable highstand conditions appear to have been too brief to permit the regressive highstand tract to prograde to the outer shelf therefore the shelf edge builds up entirely with lowstand wedges

global sea level control on local parasequence architecture from the holocene record of the po plain italy abstract holocene deposits exhibit distinct predictable and chronologically constrained facies patterns that are quite useful as appropriate modern analogs for interpreting the ancient record in this study we examined the sedimentary response of the po plain coastal system to short term millennial scale relative fluctuations of sea level through high resolution sequence stratigraphic analysis of the holocene succession meters thick parasequences form the building blocks of stratigraphic architecture above the younger dryas paleosol a prominent stratigraphic marker that demarcates the transgressive surface early holocene parasequences s 1 3 record alternating periods of rapid flooding and gradual shoaling and are stacked in a retrogradational pattern that mostly reflects stepped post glacial eustatic rise conversely middle to late holocene parasequences s 4 8 record a complex pattern of coastal progradation and delta upbuilding that took place following sea level stabilization at highstand starting at about 7 cal ky bp the prominent transgressive surface at the base of parasequence 1 correlates with the period of rapid global sea level rise at the onset of the holocene mwp 1b whereas flooding surfaces associated with parasequences 2 and 3 apparently reflect minor early holocene eustatic jumps reported in the literature changes in shoreline trajectory parasequence architecture and lithofacies distribution during the following eustatic highstand had instead an overwhelming autogenic component mostly driven by river avulsions delta lobe switching local subsidence and sediment compaction we document a 1000 year delayed response of the coastal depositional system to marine incursion farther inland from the maximum landward position of the shoreline a dramatic reduction in sediment flux due to fluvial avulsion resulted in marine inundation in back barrier position whereas coastal progradation was simultaneously taking place basinwards we demonstrate that the landward equivalents of marine flooding surfaces parasequence boundaries may be defined by brackish and freshwater fossil assemblages and traced for tens of kilometers into the non marine realm this makes millennial scale parasequences whether auto or allogenic in origin much more powerful than systems tracts for mapping detailed extents and volumes of sediment bodies the holocene parasequences of the po coastal plain with strong age control and a detailed understanding of sea level variation may provide insight into the driving mechanisms and predictability of successions characterized by similar depositional styles but with poor age constraint resulting in more robust interpretations of the ancient record

sedimentary response to late quaternary sea level changes in the romagna coastal plain northern italy data from 17 continuously cored boreholes 40 170 m deep reveal the subsurface stratigraphy of the romagna coastal plain sedimentological and microfaunal data allow the distinction of eight facies associations of late pleistocene holocene age including 18 lithofacies and 16 faunal associations ten 14c dates provide the basis to establish a sequence stratigraphic framework for the succession corresponding to the upper part 35 ky bp of the last glacio eustatic cycle the eight facies associations can be grouped into lowstand transgressive and highstand systems tracts the upper part of the lowstand systems tract consists of alluvial plain deposits these accumulated during the late pleistocene when the shoreline was 250 km south of its present day position a pronounced stratigraphic hiatus between 25 and 8 8 ky bp is invariably recorded at the upper boundary transgressive surface of these pleistocene indurated and locally pedogenized alluvial deposits the succeeding postglacial history is represented by a well developed transgressive regressive cycle transgressive deposits interpreted to reflect the rapid landward migration of a barrier lagoon system include two wedge shaped paralic and marine units these thicken in opposite directions and are separated by a ravinement surface above the transgressive deposits the maximum flooding surface mfs marks the change from a transgressive barrier lagoon complex to a prograding wave dominated delta system early po delta the mfs can be traced landwards where it constitutes the base of lagoonal deposits an aggradational to progradational stacking pattern of upper delta plain marsh lower delta plain lagoon bay and delta front beach ridge deposits reflects the progressive increase in the sediment supply accommodation ratio during the following highstand the alluvial deposits capping the sequence accumulated by the 13th century ad in response to an avulsion event that caused abandonment of the former po delta lobe and the northward migration of the po river towards its present position

control of alongshore oriented sand spits on the dynamics of a wave dominated coastal system holocene deposits northern gulf of lions france article the maguelone shore extends along the northern coast of the gulf of lions west of the rhone delta and east of high gradient coastal streams that have provided most of the clastic sediments to the gulf of lions margin since the early miocene this 10 km wide area is constituted by a small coastal watershed 15 km long in low lying carbonate hills a kilometre wide marsh a sandy beach barrier and a shoreface experiencing local low sedimentation rates this onshore offshore transition zone is a key area to understand the relationships between erosion by pass deposition and preservation processes unlike the neighbouring rhone deposits that display numerous thick deltaic sequences related to a continuous sediment flux the maguelone shore exhibits peculiar sedimentary bodies the analysis of about 250 km of new vhr seismic profiles acquired over the study area 9 short cores and outcrops data allowed us to determine the three dimensional high resolution geometry of the coastal system tracts from quaternary to present day this revealed dominant denudation processes in the upstream catchments associated with the formation of incised valleys during quaternary lowstands in addition this study investigates the erosion and deposition mechanisms controlled by littoral hydrodynamics that have been taken place on this shore since the last transgression in particular metre high and hundreds of metre long sandy bodies constructed by alongshore hydrodynamics were identified and their effect on the morphodynamics of the whole littoral system is discussed the maguelone shore can be used as an experimental study for onshore offshore dynamics under the influence of microtidal wave current hydrodynamics and very low river derived sediment flux during a eustatic cycle geometry of system tracts across flood plain to shoreface is usually considered to be controlled by relative sea level changes and is successfully analysed with 2d sequence stratigraphy cross shore models it is observed that in areas like the maguelone shore traditional sequence stratigraphy methods might not be fully relevant and need to integrate alongshore hydrodynamical processes

petrology of tholeiitic lavas from tanna island new hebrides importance of cumulative processes in island arc magmatism tanna one of the southernmost islands of the new hebrides volcanic arc is made of late pliocene to recent island arc tholeiitic basalts and andesites with sio2 contents ranging from 45 to 57 these lavas are highly porphyritic 30 50 in volume phenocrysts of plagioclase are the most abundant together with olivine and clinopyroxene the groundmass contain plagioclase augite olivine magnetite and glass pigeonite tridymite sanidine and rarely biotite may also occur the olivines and clinopyroxenes show an iron enrichment from the cores of phenocrysts to their rims and the groundmass crystals but their compositional variations are not correlated with the mg fe ratio of bulk host rocks the most fe rich compositions being found in mg rich lavas plagioclase compositions range from an95 to an60 in the basalts and an60 to an50 in the andesites but within each group they are not correlated with sio2 or na2o contents of host lavas consequently the bulk major element compositions of tanna volcanic rocks cannot be considered as primarily controlled by crystal separation from successive liquids the oxyde sio2 variations diagrams and the modal compositions and mineral chemistry show that crystal accumulation is the predominant mechanism accounting for bulk rock compositions however this does not exclude fractional crystallization the variation of the calculated groundmass mineralogy strongly suggest the occurrence of crystal removal mainly clinopyroxene and magnetite

stratal architecture of western mediterranean margins as the result of the stacking of quaternary lowstand deposits below glacio eustatic fluctuation base level abstract through a comparison of high resolution seismic stratigraphy of seven western mediterranean margins similarities and differences in stratigraphic architecture were highlighted and a hierarchy of controlling factors was established the areas are northwestern alboran ebro and northern catalonia in the spanish margin rho ne in the french margin and tuscany latium and calabria in the italian tyrrhenian margin despite their different tectonic physiographic and depositional setting the seismic facies and growth pattern of the middle late pleistocene deposits are comparable the margins are in fact the result of the stacking of lowstand systems tracts of 4th order depositional sequences bounded by polygenetic unconforniities on the shelf and condensed sections on the upper slope this lowstand nature results from the high frequency 100 ka high amplitude 100 m asymmetry falling 65 of the time and stationariness between 10 and 120 m with respect to the present of the glacio eustatic sea level curve if eustasy directly controls the types of deposits making up the margins tectonism conditions their growth pattern as it is the only factor accounting for similarities and differences in the external geometry stratal pattern and distribution of the middle late pleistocene depositional sequences an evolutionary model for the quaternary growth of young passive continental margins is proposed in this model tectonics determines the degree of preservation of lowstand deposits because it conditions the accommodation space left below the erosional profile produced by each glacio eustatic cycle thus some of the sequence stratigraphy principles widely used to set up the model have been modified and adjusted to take into consideration the peculiar nature of quaternary glacio eustasy

late quaternary stratigraphy and paleogeography of the eastern nile delta egypt abstract a petrological study of numerous sediment borings identifies the late pleistocene and holocene lithofacies in the northeastern nile delta of egypt a coarsening upward sequence characterizes the major holocene depocenters located along the northern margin of the present delta stratigraphic correlation of radiocarbon dated sections and mapping of key facies such as delta front mud reveal the locations of four major holocene delta lobes related to former distributary branches of the nile river mendesian pelusiac tanitic and pre modern damietta these lobes formed primarily of marine prodelta and delta front deposits interfinger geographically but radiocarbon dating indicates that their bases are not synchronous lobes developed for the most part since 8000 years b p i e as the rate of eustatic sea level rise began to decrease climatic and sediment discharge fluctuations lateral migrations of distributaries and isostatic subsidence of land are additional factors that affected the temporal and spatial distributions of the lobes paleogeographic maps reveal the changes with time in the distributions of different lobes and deltaic plain environments marsh lagoons and concomitant displacement of the coastline holocene sediment accumulation rates to 500 cm per 1000 years are calculated this is 10 times greater than that on the nile cone and 50 times greater than on the egyptian continental shelf the delta coastal margin in the study area migrated northward by as much as 50 km during the past 5000 years an average progradational rate of up to 10 m per year the general configuration of the present delta developed during the past millennium the major changes recently induced by man in this region coupled with a series of continuing natural phenomena slow rise in sea level coastal erosion subsidence have markedly affected the evolution of the delta petrological study of the nile delta sediments provides baseline reference information to help recognize changes in the recent geological past to help identify those taking place at present and possibly to help predict those likely to occur in this region in the future

environmental evolution and mid late holocene climate events in the valencia lagoon mediterranean coast of spain integration of geomorphological stratigraphic malacological sedimentological and micropalaeontological techniques and 14c dating allows us to characterise the processes and evolution of the coastal barrier lagoon system of valencia spain from the middle holocene to the historical epoch as well as the responses to global climate events four stages are recognised phase 1 around 8240 80 cal yr bp a brackish lagoon of moderate energy and in restricted environment was formed with an energy peak that could correspond to the maximum holocene marine transgression dating 8240 80 cal yr bp carried out in peat corresponds to a cold cycle and low water levels in inland lakes of the western mediterranean phase 2 from 6450 cal yr bp to 3710 130 cal yr bp a lagoon remained in restricted environment and connected with the sea but with a notable energy decrease and recurrent saturation processes similar to those described in other mediterranean continental lakes this phase is contemporaneous

submergent shorelines in the sw pacific evidence for an episodic post glacial transgression high resolution seismic profiles supported where possible by radiocarbon dates and regional stratigraphic data indicate that the last post glacial transgression in the sw pacific was episodic comprising major stillstands punctuated by rapid rises in sea level on the terrigenous continental shelf east of south island new zealand a succession of shorelines s8 s1 are recognized as follows s8 c 113 m 18 000 yr bp s7 c 88 m 17 000 yr bp s6 c 75 m 15 000 yr bp s5 c 56 m 12 000 yr bp s4 c 46 m 11 000 yr bp s3 c 28 m 9 500 yr bp s3a c 24 m 9 000yr bp s2 c 9 m 7 500yr s1 0 m 6 500yr bp with the exception of s8 and possibly s2 the shorelines are associated with wedges of sediment the size and presence of which imply that 1 sea level stabilized at some shorelines for a considerable period of time up to i 2 000 yr and 2 the intervening rises of sea level estimated to have been at least 10 12 m lo3 yr were too rapid to allow the reworking of the wedges into a transgressive sediment sheet as favoured in some current models on the great barrier reef shelf off queensland australia shorelines s8 sl have also been recognized with a further shoreline feature s4a occurring at c 39 m shorelines sla 0 m o yr bp slb 2 3 m 6 000 yr bp and slc 0 m 6 500 yr bp are recognized as discrete aspects of the post 6 500 yr bp sea level behaviour in north eastern australia the rapid rise in sea level at least between shorelines s5 12 000 yr bp and 53 9 500 yr bp is known to have outpaced reef growth causing in situ drowning of reefs located along the deeper shorelines all modern reefs so far drilled and dated began their development at or above s3 28 m 9 500 yr bp some of the shorelines particularly s5 appear to correlate between the northern and southern hemispheres on the basis of age succession and general depth of occurrence suggesting 1 that they may be global features controlled by the post glacial pattern of ice sheet decay and 2 that hydro isostatic adjustment may exert only a minor control on the depth of particular shorelines at least during the earlieg parts of the post glacial transgression

onshore offshore correlation of the llobregat deltaic system spain development of deltaic geometries under different relative sea level and growth fault influences abstract groundwater resources in deltaic aquifers are essential in the mediterranean region to sustain the socio economic development of coastal communities and shallow water ecosystems understanding the geological connection between coastal aquifers and the offshore sedimentary record is important to better predict consequences in terms of water management in spite of this most approaches to postglacial and pleistocene deltaic sedimentation focus either on the offshore or the delta plain few studies correlate and integrate the entire system in the llobregat delta south of barcelona spain onshore offshore correlation is achieved by integrating data from sediment cores acquired on the deltaic plain with seismic profiles from offshore data integration enables the reconstruction of the entire deltaic system providing a more well defined picture and a better understanding of the onshore offshore stratigraphic framework in a late quaternary tectonically active narrow shelf in the western mediterranean basin the late quaternary record in the llobregat delta shows an unusual well preserved transgressive regressive cyclic stacking pattern which displays peculiarities compared with most mediterranean quaternary deltaic shelves given that the transgressive and highstand intervals appear to be significantly preserved both onshore and offshore the preservation of these deposits is attributed to the high subsidence rate on the continental margin controlled by quaternary faults and the structure of the basement and by sediment supply fluctuations depositional sequences also reveal contrasting patterns between the northeastern and southwestern llobregat shelves and show significant variability in the dip direction the results are compared with diverse stratigraphic architectures reported elsewhere and provide information to the ancient delta deposits about the distinct types of deltaic geometries generated under different sea level trends helping to improve sequence stratigraphic models where deltaic geometries generated during specific intervals of the sea level curve are poorly constrained and or documented

late quaternary sedimentation on the north aegean continental margin greece the late quaternary seismic stratigraphy of the north aegean continental shelf and adjacent basins has been interpreted from boomer and 3 5 khz seismic profiles ages derived from shallow cores and offshore wells and relative offsets on small synsedimentary faults provide chronological control sea level history inferred from seismic stratigraphy correlates with the global eustatic sea level record based on oxygen isotopic curves outer shelf progradation correlates with lowstands of sea level in isotopic stages 2 3 and 6 whereas shelf wide transgression surfaces correspond to the stage 6 5 and 2 1 transitions when rapid deglaciation occurred the present depth of the delta plain formed on the outer shelf during the late stage 6 lowstand provides a dated and originally horizontal marker for estimating rates of tectonic subsidence gross distribution of sediment facies is similar in both tectonically stable and active areas the shelf break formed by delta progradation but is marked by faults in most places because of the accommodation provided by graben subsidence rates of 0 3 1 5 mm yr standard sequence stratigraphic analysis can be applied to these sediments deposited during high amplitude quaternary sea level oscillations high rates of subsidence result in the preservation of an unusually complete record of sea level change major lowstand progradation is dependent on the duration rather than the magnitude of sea level lowstand the long glaciations in isotopic stages 6 12 16 and 22 resulted in the most prominent seaward progradation on the margin sandy lowstand turbidite deposits formed only when there was rapid fall in sea level otherwise sand was trapped on delta tops and silty muds were deposited in deep water

sand composition and sedimentary evolution of a late quaternary depositional sequence northwestern adriatic coast italy abstract in order to detect temporal and spatial variations in detrital supply in the upper part of the last depositional sequence of late pleistocene holocene age we conducted a combined petrographic and stratigraphic study in the romagna coastal plain south of the po delta northern italy we analyzed heavy minerals and the bulk composition of sands from cores and surface samples by using petrographic and stratigraphic data on composition of modern beach and major river deposits new aspects of detrital dispersal mechanisms and the depositional history of the study area are documented the heavy mineral distribution coupled with the dolostone and volcanic rock fragment contents of bulk sands allow identification of three different petrofacies petrofacies a petrofacies b and petrofacies c which have been interpreted as of apenninic mixed eastern alps po river basin and po river catchment basin provenance respectively distribution of the three petrofacies changed through time in response to landward and seaward shifting of the coastline during the late pleistocene lowstand a pure apenninic provenance characterized the romagna coastal plain petrofacies a during the holocene transgression when the shoreline migrated tens of kilometers west of its present position eastern alpine sediment sources fed littoral facies petrofacies b probably as a result of southward transport by littoral drift this sediment supply continued during the early regressive phases and was cut off by a change in coastal morphology related to the development of the early po delta this led to the establishment of a sediment supply entirely related to the po river catchment basin petrofacies c changes in the compositional signature of sand in the youngest beach ridges mark the abandonment of the early po delta due to an avulsion event and testify to the establishment of a coastal system fed by rivers draining the apennines petrofacies a we emphasize sand petrography as an important tool in studying the internal architecture of sandy clastic depositional units on detailed spatial scales and its use in deciphering the depositional history of complex sedimentary successions fig 1 location of the study area end page 829

geotechnical characterization of the upper pleistocene holocene alluvial deposits of roma italy by means of multivariate geostatistics cross validation results abstract we are presenting an attempt to evaluate the spatial variability of geotechnical parameters in the upper pleistocene holocene alluvial deposits of roma italy by means of multivariate geostatistics the upper pleistocene holocene alluvial deposits of roma are sensitive to high levels of geohazard they occupy a sizable and significant part of the city being the foundation for many monuments historical neighborhoods and archaeological areas and the main host of the present and future subway lines we have stored information from more than 2000 geotechnical boreholes crossing the alluvial deposits into a relational database for the present study only the boreholes with lithologic textural interpretation and geotechnical information were selected the set includes 283 boreholes and 719 samples which have a set of geotechnical information comprising physical properties and mechanical parameters techniques of multivariate statistics and geostatistics were combined and compared to evaluate the estimation methods of the mechanical parameters with special reference to the drained friction angle from direct shear test principal component analysis was applied to the dataset to highlight the relationships between the geotechnical parameters through cross validation analysis multiple linear regression kriging and cokriging were tested as estimators of cross validation demonstrates that the cokriging with granulometries as auxiliary variables is the most suitable method to estimate in addition to proving that cokriging is a good estimator of cross validation demonstrates that input data are coherent and this allows us to use them for estimation of geotechnical parameters although they come from different laboratories and different vintages nevertheless to get the same good results of cross validation in estimation it is necessary for granulometries to be available at grid points since this information being not available at all grid points it is expected that in the future textural information can be derived in an indirect way i e from lithologic textural spatial reconstructions

forced regressions in a sequence stratigraphic framework concepts examples and exploration significance sequence stratigraphic concepts suggest that stratal geometries develop and are largely controlled by changes in relative sea level on the shelf lowstand deposits which form during falls and subsequent stillstands of relative sea level can be recognized by the presence of an unconformity at the base the isolated and basinward position relative to the previous shoreline and the abrupt seaward translation of shallow water and shoreline facies into the basin across an unconformity surface this seaward translation of facies and shoreline regression in response to relative sea level lowering is termed a forced regression a forced regression is independent of variations of sediment flux and is in contrast with normal regressions that occur in response to excess sediment flux relative to space available on the shelf i e accommodation forced regressions commonly are associated with a zone of sedimentary bypass subaerial exposure and possible fluvial erosion between the newly formed and preceding shorelines certain shelf sands previously interpreted as offshore or mid shelf sand bodies thus can be reinterpreted as stranded lowstand shorelines associated with forced regressions this alternative interpretation has economic significance insofar as it suggests different subsurface correlations and reservoir geometries with the potential for development of new play types and enhanced recovery in o der fields examples of forced regression can be observed at a variety of scales and ages several such examples include the modern east coulee fan delta and the lower cretaceous viking formation in alberta canada the quaternary rhone delta and the quaternary hudson valley system

geochemistry vs seismo tectonics along the volcanic new hebrides central chain southwest pacific abstract compositional variations major and trace element of pleistocene to present rocks along the volcanic new hebrides central chain southwest pacific are presented and discussed using a new set of analyses we focus in particular on the anomalous mg k lile and lree rich and al and si poor character of the basalts from aoba and santa maria volcanoes and to a lesser extent from ambrym volcano all located in the area where the d entrecasteaux zone collides with the arc in addition we note a compositional transition from normal arc basalts to boninite related high mg andesites at the southern termination of the nhcc the peculiar composition of the rocks of the volcanoes facing the d entrecasteaux zone has traditionally been related more or less directly to the collision subduction occurring in this area we present an alternative hypothesis of a strong geochemical anomaly under santa maria and aoba volcanoes unrelated to this collision in this model a westward and upward invasion of dupal type enriched mantle corroborated by the pattern of intermediate seismicity occurs under this part of the arc in strong contrast to the usual pacific type morb mantle source present under all other volcanoes of the nhcc such a dupal type source may explain the anomalous geochemistry of the resulting volcanic products

effect of sea level variation on upper slope depositional processes offshore of tiber delta tyrrhenian sea italy abstract the upper slope and outer shelf in front of the tiber river mouth east central tyrrhenian sea exhibits a series of about 15 gullies that are not clearly related to present day erosional or depositional processes an extensive high resolution seismic reflection profiling survey of a 450 km 2 area in front of the tiber delta shows several generations of similar features within the older depositional sequences underlying the outer continental shelf the gully relief appears dominantly depositional probably developed during lowstand periods when the tiber river mouth was relatively near the shelf break the position of the gullied intervals including those on the modern slope relict from the last lowstand shows a successive northward shift with time this northward shift indicates continued tilting of this part of the eastern tyrrhenian continental margin probably resulting from a continued subsidence to the north

temporal significance of sequence boundaries abstract this paper analyses the temporal significance of stratigraphic surfaces bounding the marine portions of the depositional sequence genetic stratigraphic sequence and transgressive regressive sequence these bounding surfaces known as the correlative conformity c c maximum flooding surface mfs and conformable transgressive surface cts respectively may either be defined on the basis of stratal stacking patterns which we call type a surfaces or on the basis of water depth changes and relative sea level changes which we call type b surfaces the type a mfs and cts are time lines in a depositional dip section corresponding to the turnaround points from shoreline transgression to regression and vice versa they separate prograding coarsening upward from retrograding fining upward geometries with a timing determined by the interplay between the rates of sedimentation and relative sea level rise in the shoreline area the timing of type a mfs and cts is not affected by the offshore variations in sedimentation and subsidence rates but it is only controlled by the shoreline movements and the associated facies shifts the type a c c separates rapidly prograding and offlapping forced regressive strata from the overlying lower rate prograding and aggrading normal regressive strata this surface is diachronous younger basinward with the rate of offshore sediment transport the timing of the type a c c in the shoreline area corresponds to the end of relative sea level fall but it develops under relative sea level rise conditions offshore the timing of the type b mfs and cts depends on the offshore variations in the sedimentation and subsidence rates these surfaces defined on the basis of bathymetric changes become younger and older seaward respectively tending to merge together offshore the type b c c marks the end of relative sea level fall in any point along a depositional dip section it is diachronous older basinward as its timing depends on the offshore variations in subsidence rates the diachroneity of type b surfaces reaches a quarter of the period of the highest frequency variable whichever that is among the eustasy tectonics or sedimentation controls types a and b surfaces merge together in the shoreline area but they become temporally divergent offshore deepening upward and shallowing upward facies should not be confused with transgressive and regressive systems tracts the latter are strictly controlled by the shoreline movements which determine the direction of facies shifts and the stratal stacking patterns

sequence stratigraphy of a coastal plain incised valley estuary lake calcasieu louisiana abstract the stratigraphic profile along a 100 km section of the lake calcasieu incised valley fill was reconstructed from 87 bridge borehole records at four sites along the tidal reaches of the calcasieu river an additional 18 boreholes aligned along the chenier plain near the estuary mouth and shallow seismic data collected along 160 km of track line within the lake calcasieu central basin valley incision occurred during the d18o stage 2 sea level lowstand when the paleo calcasieu river flowed across the inner continental shelf and incised into older fluvial terraces of the prairie formation the valley floor is 57 m deep beneath the modern chenier plain and rises to 30 m along the upper reaches of the modern estuary sea level rise commenced about 20 ka and has continued episodically throughout the holocene shoreline transgression has proceeded at varying rates in response to sea level rise and the incised valley is now occupied by a wave dominated estuary fringed by the chenier plain of western louisiana lowstand deposits are poorly preserved within the calcasieu incised valley deposits constituting the transgressive systems tract tst lie directly above the lower sequence boundary at the top of the prairie formation the tst shows greatest facies diversity and clearest separation of bounding surfaces toward the present seaward end of lake calcasieu here the tst comprises three parasequences that include fluvial bayhead delta and central basin estuarine deposits multiple flooding surfaces within the tst relate to the episodic style of sea level rise highstand infilling of the valley has been characterized by nearshore marine deposition and chenier plain progradation along the lower reaches of the modern calcasieu river the valley fill comprises transgressive central basin nd landward stepping bayhead delta facies overlain by the highstand bayhead delta complex this study documents the most recent phase of deposition within the compound fill of a coastal plain incised valley and demonstrates the potential importance of fluvial controls on facies within incised valley systems

quaternary sequence stratigraphy of the brisbane river delta moreton bay australia abstract the quaternary geological history of the brisbane river delta front and prodelta was interpreted using seismic stratigraphic and sequence stratigraphic principles during the last major glacial sea level episode the floor of the bay was exposed and eroded by stream channels in the subsequent postglacial marine transgression the palaeochannels of the brisbane and pine rivers were backfilled with mud sea level continued rising until about 6500 years ago and a highstand has persisted since then during the quarternary sediment deposition in moreton bay was controlled by sea level fluctuations channel migration and palaeotopography there were at least four depositional episodes prior to the last glacial period plus the presenet postglacial episode periods of low sea level occurred between highstands and the sea bed exposed and eroded eight major seismic reflectors were recognised and six seismic sequences defined the seismic sequences represent five highstand systems tracts and one transgressive systems tract the relationships between eustacy and system tract type were applied to glacio eustatic sea level curves to determine relative ages of sequences in moreton bay the application of sequence stratigraphy to high frequency sea level fluctuations was demonstrated the stratigraphic system established within the context of sequence stratigraphy will provide a reference for future work within the region

anatomy of sinosauropteryx prima from liaoning northeastern china a spectacular pair of sinosauropteryx skeletons from jurassic cretaceous strata of liaoning in northeastern china attracted worldwide notoriety in 1996 as the first dinosaurs covered with feather l

transgressive and regressive stratigraphies of coastal sand barriers in southeast australia abstract in recent years attempts have been made in southeast australia to document the stratigraphic characteristics of coastal sand barriers two basic arrangements of facies are distinguished those associated with transgressive depositional sequences and those associated with regressive sequences transgressive sequences either are formed during the postglacial marine transgression or are related to receding or transgressive barriers at present sea level in the former case complex interfingering of nearshore washover and lagoonal facies are evident in many areas these facies underlie those associated with regressive sequences which have formed since sea level has reached its present position ca 6000 6500 yrs ago examples of regressive sequences associated with both prograded and stationary barrier types occur in southeast australia here the thickness of nearshore facies in particular is commonly greater than equivalent units beneath barriers on coasts of lower energy and for less steep inner shelf gradients in the northern hemisphere the interplay of various factors within embayments has led to the development of several barrier types such as prograded stationary receded and episodic dune with some sedimentary characteristics in common with similar types recognized in other parts of the world e g texas delaware the netherlands barriers formed as a result of migrating spits and tidal inlets are not common in southeast australia

the holocene record of environmental changes in the stagno di maccarese marsh tiber river delta central italy the stratigraphic study of the stagno di maccarese carried out on the sediments exposed in about 7 km of trenches excavated in an area of approximately 1 5 km2 has shown that in the course of the holocene many environmental variations have taken place the complex evolution of the marsh is demonstrated by the variations in water salinity and the presence of erosion surfaces and soils between the sediments in the early holocene the area studied was an isolated marsh with water having variable salinity and it was only about 6000 cal yr bp that it was encompassed in the system of inner delta marshes in the delta environment the water of the marsh was oligohaline until about 9th 8th centuries bc brackish from 9th 8th centuries bc to about 600 yr bp and later oligohaline until the 19th century drainage a number of environmental variations are connected with local phenomena such as erosion of the beach ridges and tiber floods but the others can be correlated chronologically with climatic events rec

architectural stacking patterns of the ebro delta controlled by holocene high frequency eustatic fluctuations delta lobe switching and subsidence processes abstract during the late pleistocene and holocene 125 ka b p to present a type 1 4th order depositional sequence comprising regressive lowstand transgressive and highstand system tracts formed worldwide the holocene 10 ka b p to present part of this contains the latest and present highstand systems tract hst within this and the underlying transgressive systems tract tst of the ebro delta in northeastern spain higher frequency 5th to 6th order sea level fluctuations are recognised these form retrogradational and progradational high frequency depositional sequence sets within the tst and hst respectively each high frequency sequence comprises 1 a basal highly reflective shell lag associated with an erosional transgressive surface 2 aggradational deposits which seawards consist of a wedge of marine clays with transparent seismic facies but inland are represented by thick peats 3 progradational deposits composed of sandy delta front facies displaying slope clinoforms these pass seawards into prodeltaic grey silts and landwards into red silts and pebbly sands of delta plain facies the progradational deposits downlap towards their bases the aggradational deposits formed in response to a period of rising sea level and a rapid increase in accommodation space progradation began when sediment supply to the delta exceeded accommodation space as a result of relative sea level fall the relative sea level curve for the delta has a stepped character caused by the punctuation of the 4th order sea level trend by higher frequency eustatic fluctuations as well as by high subsidence rates of about 1 75 mm per year the tst comprises retrogradational parasequences that onlap the underlying pleistocene gravels the maximum flooding surface separating the tst from the hst was formed about 6900 yrs b p on the basis of14c dating of peats the hst comprises progradational deltaic and aggradational units stacked as progradational high frequency parasequence sets the hst of the ebro delta is compared with other deltaic sequences around the world in particular with that of the mississippi delta a tentative chronology of the high frequency climatic and eustatic oscillations influencing deltaic sedimentation globally over the last 7000 years is presented

transgressive and highstand systems tracts and post glacial transgression the east china sea abstract the late pleistocene holocene depositional sequence on the shelf in the east china sea ecs is interpreted on the basis of the analyses of four sediment cores and high resolution seismic reflection sub bottom profiler records along a ne sw across shelf transect sedimentary strata deposited above a lowermost planar erosional surface that was formed during sea level fall of the last glacial are divided into two units along a ne sw across shelf transect changjiang okinawa the lower unit is characterized by seaward dipping tangential clinoforms with a thickness of 30 40 m at mid shelf depths and less than 30 m beneath the outer shelf prograding clinoforms are more obvious in mid shelf environments the upper unit is characterized by an upper transparent layer that is formed into ridge and swale topography the boundary between the upper and lower units is sharp and erosional surficial sediments taken by cores from the central ecs shelf are also divided into two facies a sandy facies consisting of sand or sandy gravel with moderately abundant molluscan shell fragments and a muddy facies comprising mud intercalated with thin sand layers the sandy facies is widely distributed on the middle to outer shelf seafloor and has a measured thickness of 30 cm up to several metres radiocarbon ages of molluscan shells in this sediment are less than approximately 10 ka bp except for ages from basal shell lag deposits which are 10 40 ka bp the muddy facies underlies the sandy facies and has radiocarbon ages of 2 7 2 9 ka bp previous work and 20 38 ka bp this study and tl ages of 27 50 ka bp previous work the boundary between these lithologic units is an erosional sharp contact the sandy and muddy facies are correlated with the upper and lower seismic units respectively the lower unit is characterized by prograding clinoforms and is interpreted to represent deltaic or nearshore tidal ridge sediments of the paleo changjiang river that were deposited during the last glacial lowstand of sea level as a lowstand systems tract the underlying erosional surface is interpreted to be a sequence boundary formed as a regressive marine erosional surface during the fall of sea level the erosional boundary between the lower and upper units is interpreted as a transgressive surface of erosion formed during the subsequent rise of sea level the upper unit has a modern sand ridge topography and is interpreted to represent offshore shelf sand ridges of the transgressive to highstand systems tract

petrology of matthew and hunter volcanoes south new hebrides island arc southwest pacific abstract matthew and hunter the two southernmost active volcanoes of the new hebrides island arc southwest pacific differ markedly from the other mainly tholeiitic quaternary volcanoes of this arc geodynamically related to the new hebrides subduction zone they also lie close to the southern limb of the active expanding ridge of the north fiji basin both volcanoes are made up of acid medium k calcalkaline orogenic andesites containing a variety of inclusions pyroxene and gabbroic cumulates as well as doleritic cognate inclusions this paper presents the first systematic petrographic and chemical study of these volcanics and their inclusions trace element geochemistry and rare earth element modelling suggest that the two volcanoes developed from successive batches of similar parental magmas originating from limited partial fusion of garnet peridotite in the mantle wedge various degrees of fractional crystallization of these batches led to the formation of three volcanic suites hunter little fractionated west matthew moderately fractionated and east matthew highly fractionated moreover on matthew island no correlation exists between the degree of fractionation and the eruptive chronology the youngest edifice west matthew being less evolved than the older one east matthew

late quaternary evolution of the gulf of patras greece tectonism deltaic sedimentation and sea level change abstract the gulf of patras is an actively subsiding late cenozoic graben in western greece that receives deltaic sediment from the large acheloos and evinos rivers the late quaternary sedimentation history of the gulf is interpreted from 3 5 khz profiles numerous short cores and airgun seismic profiles a widespread unconformity represents the isotopic stage 2 marine lowstand when the gulf was subaerially exposed subsequent deltaic progradation and associated coastal transgression was greatest during the 13 10 5 ka slowdown in sea level rise and the period of stable sea level since the mid holocene switching of delta distributaries can be related to the known evolution of the subaerial parts of the deltas the stage 2 unconformity provides a datum for quantitative determination of rates of subsidence the central graben is subsiding at rates of 3 5 mm yr rates in the northern part of the gulf average 1 2 mm yr this is consistent with a listric faulting model for the origin of the modern patras graben

continental depositional systems of the quaternary of the po plain northern italy abstract the po plain is a molasse foredeep bounded by two mountain chains apennines and alps apenninic thrusting is still active whereas the alpine one ended by early pliocene times the continental deposits form a veneer at the surface and form the topset of a prograding complex the po river divides the plain into two sectors with different sedimentary facies and body geometries to the south the alluvial fan and plain deposits are small embedded in clays and show elongate shapes to the north sedimentary bodies are laterally extensive tabular and with minor amounts of fine grained sediments this difference could be due to a different climatic conditions during quaternary ice ages on the two sides of the basin b different structural settings in the two sectors of the basin that produce a higher subsidence rate to the south c different lithologies in the source areas i e alps and apennines

high resolution seismic study as a tool for sequence stratigraphic evidence of high frequency sea level changes latest pleistocene holocene example from the korea strait abstract sequence stratigraphic analysis of high resolution seismic reflection profiles and sediment data reveals that the latest pleistocene holocene deposits in the korea strait shelf off the southeastern korean peninsula form a high frequency sequence consisting of a set of lowstand transgressive and highstand systems tracts that corresponds to a fifth order 20 kyr sea level cycle eight depositional systems each with different seismic facies constitute the systems tracts the lowstand systems tract consisting of sandy mud forms a deltaic wedge that pinches out updip near or at the relict shelf edge the transgressive systems tract consisting mainly of sands includes six depositional systems 1 inner shelf transgressive layer 2 transgressive estuarine deltaic complex 3 transgressive sand ridge 4 mid shelf transgressive layer 5 incised channel fill and 6 beach shoreface complex although the transgressive systems tract is widely distributed it is much thinner than the lowstand and highstand systems tracts the highstand systems tract is composed of a prodelta shelf complex consisting almost exclusively of holocene muds the distribution and geometry of the systems tracts in the latest pleistocene holocene sequence in the korea strait shelf is different from that of vail s model in that 1 the lowstand systems tract consists only of the lowstand deltaic wedge which forms an elongated sediment body along the paleoshelf edge and 2 the highstand systems tract is completely confined to the inner shelf and forms a nearshore belt parallel to the coastline high frequency 20 kyr high amplitude magnitude of about 130 m sea level change together with strong currents flowing northeastward along the southeastern coast of the korean peninsula and varying sediment supply have resulted in this rather unusual stratigraphic architecture

sequence stratigraphy and depositional setting of the tiber delta integration of high resolution seismics well logs and archeological data abstract using archeological evidence radiocarbon data well logs and high resolution seismic profiles we applied sequence stratigraphic analysis to sediments deposited during the last glacio eustatic cycle on the tyrrhenian continental margin embracing the tiber river months these sediments form a high frequency sequence of fifth order that has developed over the last 20 000 yr since the last lowstand hereafter referred to as the tiber depositional sequence tds the tds is still evolving and lies on a type 1 sequence boundary that has been identified both on the shelf and below the present delta plain this sequence consists of lowstand transgressive and highstand systems tracts the lowstand deposits are not present on the shelf but are found on the continental slope where they constitute the last progradation set of the continental margin a network of gullies active when the river mouth was at the shelf break is present within the lowstand deposits the transgressive systems tract tst deposits lie directly on the basal unconformity landwards the tst is represented by a retrogradational parasequence set of fluvial coastal barrier lagoon and lagoonal delta facies seaward on the shelf these parasequences merge into a seismically transparent deposit that forms a condensed section the flooding surfaces that bound the parasequences are marked by peat layers that were dated by 14c the radiometric ages were used to draw a carve of sea level rise for the last 11 000 yr the top of the transgressive systems tract maximum flooding surface is represented by the last peat layer which was formed about 4700 5000 yr bp and buried 4 5 m below the present upper delta plain the highstand systems tract is made up of deposits of the present tiber wave dominated delta i e upper and lower delta plain delta front and prodelta slope the aligned beach ridges mark the position of the prograding coastline which for the last 2500 yr can be dated by archeological and historical data the recent very fast progradation of the tiber delta during the last 500 years is consistent with historical data on floods of the city of rome and the suspended load of the tiber river

a polar dinosaur feather assemblage from australia abstract exceptionally preserved mesozoic feathered dinosaur fossils including birds are famous but recognized from only very few localities worldwide and are especially rare in the southern hemisphere here we report an assemblage of non avian and avian dinosaur feathers from an early cretaceous polar around 70 s environment in what is now southeastern australia the recovered remains incorporate small 10 30 mm long basal paravian like tufted body feathers open vaned contour feathers and asymmetrical bird like wing feathers that possess high angled barbs with possible remnants of barbicels amongst the geologically oldest observed to date such morphological diversity augments scant skeletal evidence for a range of insulated non avian theropods and birds inhabiting extreme southern high latitude settings during the mesozoic although some of these fossil feathers exhibit what may be residual patterning most are uniformly toned and preserve rod shaped microbodies as well as densely packed microbody imprints on the barbules that are structurally consistent with eumelanosomes geochemical analysis detected no identifiable residual biomolecules which we suspect were lost via hydrolysis and oxidization during diagenesis and weathering nevertheless an originally dark pigmentation can be reasonably inferred from these melanic traces which like the coloured feathers of modern birds might have facilitated crypsis visual communication and or thermoregulation in a cold polar habitat

coalescent valley fills from the late quaternary record of tuscany italy abstract three prominent incised valley fills of post last glacial maximum age are described from the northern tuscan coast of italy stratigraphic correlation of core data along a cross section transversal to the present fluvial channel axes enables identification of a suite of genetically related valley bodies that fill the incisions made up by arno serchio and camaiore stiava rivers during the last glacial interglacial cycle the valley fills display different shapes and size but remarkably similar facies architecture valley bodies range between 5 and 10 km in width and between 30 and 45 m in thickness with width thickness ratios of about 100 300 above a lowstand and early transgressive gravel fluvial deposit the three incised valley fills display a distinctive succession of coastal plain to estuarine facies dated to about 13 8 cal ka bp radiocarbon dates document that the three valleys were active simultaneously accommodation space was rapidly created during transgression and then filled under conditions of very high sediment accumulation about 1 cm y in contrast to the more common deepening upward trend recorded by the latest pleistocene early holocene valley fill successions worldwide sedimentation in the tuscan valleys equalled or even exceeded the rate at which accommodation was created thus leading to an aggradational rather than backstepping stacking pattern of high frequency millennial scale parasequences above the valley fills and on the interfluves a thin deepening upward succession of nearshore deposits marks the rapid change from aggradational to retrogradational depositional style this is invariably overlain by a characteristic shallowing upward motif of prograding deltaic and coastal facies the maximum flooding surface which can be tracked across the whole study area on the basis of subtle palaeontologic indicators is shown to represent an almost isochronous surface dated to about 7 8 cal ka bp through examination of large scale geometry and facies attributes of the valley fills including the relationships between valley bodies and interfluves this study represents an example of how adjacent river systems with significantly different characteristics may respond simultaneously in a consistent manner to rapid changes in sea level and climate conditions

petrology geochemistry and tectonic implications of volcanics dredged from the intersection of the yap and mariana trenches abstract rocks dredged from the forearc very close to the intersection of the yap and mariana trenches include a suite of highly depleted arc tholeiites and several samples of transitional to slightly alkaline basalt the tholeiites range from magnesian quartz tholeiites with 0 46 0 6 tio2 to andesites with up to 62 sio2 and 8 2 feo all show pronounced lree depletion and have very low contents of ba and sr they are postulated to have been produced by partial melting of upper mantle peridotite residual after morb extraction following influx of hydrous fluids from the subducted slab while these fluids were responsible for small enrichments in ba k rb and sr in melts generated lree were not involved in the metasomatism and the strong lree depletion probably reflects the unmodified depleted source peridotite the second lava suite includes slightly ne normative ti augite bearing basalts with convex upward ree patterns showing slight lree depletion la sm n 0 76 the chemical features of these basalts support affinities with basalts erupted during the earliest stages of backarc basin opening a k ar age on one sample 7 8 1 3m y is in good agreement with the initial opening of the mariana trough the tectonic significance of the dredged arc tholeiite suite is less obvious a k ar age of10 8 0 4 my on one andesite and the occurrence of similar lavas in dredges from at least 300 km along the length of the yap arc suggest that subduction was occurring beneath the yap arc in the late miocene after overthrusting of the yap greenschist allochthon and while calc alkaline arc magmatism was occurring further north on the west mariana ridge we suggest that the depleted arc tholeiites in dredge 1438 were generated by abnormally shallow melting of upper mantle beneath the yap forearc following subduction beneath this area of young hot sorol trough crust these arc tholeiites represent a magma type transitional between more typical arc tholeiites e g tongan and high mg andesites and boninites

physical stratigraphy and sedimentology of the late pleistocene holocene tiber delta depositional sequence the tiber delta lies on the passive continental margin of central western italy the tiber delta is a late pleistocene holocene sedimentary succession and constitutes an incomplete high frequency depositional sequence 4th or 5th order which developed from the last post glacial rise in sea level to the present stillstand it is bound by a type 1 basal unconformity which cuts pleistocene deposits five depositional systems have been identified 1 coastal barrier lagoon 2 shelf transition 3 fluvial braided 4 tiber lagoonal deltas t1 t2 t3 and 5 tiber wave dominated delta the first four systems constitute the transgressive system tract tst which is characterized by a retrogradational parasequences set while the fifth system represents the highstand system tract hst characterized by only one parasequence progradational the evolution of these depositional systems has been mostly controlled by sea level rise which was not continuous but punctuated by eight minor stillstands and rapid rises this mechanism of sea level change led to the formation of parasequences that developed within the depositional systems from a palaeogeographical point of view the present tiber delta area was mainly characterized by a coastal barrier lagoon and tiber lagoonal deltas t1 t2 t3 which migrated landwards during the sea level rise throughout the time of the present stillstand the t3 lagoonal delta prograded rapidly into the lagoon reaching the coastal barrier and the lagoon was replaced first by marshes and then by the alluvial plain finally the tiber river overcame the littoral barrier supplying the coast giving rise to the present wave dominated delta

the effects of late quaternary sea level changes on the rhone slope sedimentation northwestern mediterranean as indicated by seismic stratigraphy abstract high resolution single channel seismic profiles have been collected on the shelf and slope off the present rhone delta western mediterranean using a 750 j sparker these profiles have been correlated with earlier high resolution seismic work on the shelf that identified several superimposed wedge shaped seismic units interpreted to be late quaternary shelf perched lowstand wedges these wedge shaped seismic units are traced onto the slope in an intercanyon area between the grand rhone and petit rhone submarine canyons detailed analysis of the seismic facies shows that upper quaternary slope deposits also define sedimentary cycles each basic cycle is composed of a couplet of two different subunits the lowest one is mostly transparent has a gentle seaward convergent geometry and correlates with one complete perched lowstand wedge on the shelf the upper subunit is well stratified has a gentle seaward divergent geometry and correlates with an erosional unconformity on the shelf 14c dating of the youngest slope cycle indicates that most of the deposition on the slope occurred during low sea level periods and that the couplet of transparent and layered subunits are the result of the interaction between eustatic sea level sediment flux and the geometry of the continental shelf and slope stratified elongated wedges on the slope are interpreted as deposition when the depocenter moves out from the shelf to the upper slope and deep basin this model is compared to the late quaternary eustatic sea level curve some cycles in this curve seem to be absent on the slope or completely eroded on the shelf indicating that caution is necessary in deducing relative sea level cycles from continental margin stratigraphy

biomarkers in coastal marshlands environmental characteristics of the mazarron basin during the middle pleistocene mis 7 and holocene mis 1 abstract we reconstructed the paleoenvironmental conditions of the mazarron basin during mis 7 and mis 1 based on their alkane and fatty acid contents their mineralogy and the fossil content of an amino acid dated sediment sequence the n alkane and fatty acid indices proved to be excellent paleoenvironmental proxies for studying the paleo hydrogeological and paleoclimatological evolution of this marshland three geochemical units gus were identified from the abundance of the c25 n alkane and the acl tarhc and paq values confirming the importance of phases with terrestrial plant input or aquatic macrophyte predominance these gus were used to define three paleoenvironmental episodes pes during mis 7 in pe7 1 the contribution of algal and aquatic macrophytes predominated in a temporarily flooded saline muddy plain in pe7 2 the major contribution was from aquatic macrophytes flooded marsh although it was marked by episodes of emersion with greater terrestrial contribution at the top of the mis 7 record pe7 3 there was a significant reduction in the water depth with the main input deriving from terrestrial plants in a muddy alluvial plain six pes were established during mis 1 holocene of which three predominately received organic matter derived from aquatic macrophytes while the major contribution in the other three came from terrestrial plants the two sets of pes were linked to episodes of increased and decreased water level respectively this interpretation is consistent with the characteristics of the sediment facies with pe1 1 1 3 and 1 5 corresponding to a marsh with deeper water and a greater input of detrital materials and pe1 2 1 4 and 1 6 to a shallow environment with carbonates and gypsum deposits direct marine influence was limited so the oscillations in the water level in the marsh were likely to be more related to climatic changes drier wetter phases and recent tectonics than to large changes in sea level emersion led to degradation of the organic matter and enrichment in short chain and branched saturated fatty acids

sequence stratigraphy seismic profiles and cores of pleistocene deposits on the rhone continental shelf abstract high resolution seismic profiles on the rhone deltaic shelf has shown the existence of a complex of pleistocene superimposed prograding wedges interrupted by a major incised valley system cutting across the shelf the individual wedges are interpreted from internal geometry and coring data as prograding shoreface deposits accumulated during periods of relative sea level lowering punctuated by small scale relative sea level falls or forced regressions they are related to 5th order glacio eustatic cycles and are stacked to form a composite 4th order sequence radiocarbon dating tandetron ams of the upper wedge to 40 ka bp indicates a stratigraphic hiatus across the shelf corresponding to the glacial maximum lowstand at the end of the wurmian cycle isotopic stage 2 during which sea level had dropped to 120 m below present sea level seaward tilting of the wedge boundaries indicate that the shelf has been subjected to differential subsidence that provides the necessary accommodation space for deposits to accumulate on the mid outer shelf the seaward tilting results from a cumulative effect of sediment and hydrostatic loading tectonism is also expressed by a westward shore parallel tilting in the area east of the incised valleys the amount of tilting the stacking pattern of the wedges and the location of incised valleys are structurally controlled by the alpine orogen which dips westward under the rhone margin the tectonic component interacts with glacio eustatic sea level fluctuations and accounts for the partition of the shelf into two areas with specific features separated by the rhone incised valleys

southern polar forests the early cretaceous floras of victoria and their palaeoclimatic significance abstract a diverse fossil flora including cryptogams pteridosperms cycadales bennettitales ginkgoales coniferales and angiosperms occurs in early cretaceous fluvial and lacustrine strata in the otway and gippsland basins in southern victoria both evergreens e g araucarians cycads ferns and deciduous or semi deciduous forms e g certain pteridosperms and ginkgoales seem to have been represented certain ferns ginkgos and conifers grew to a large size overall the assemblages are typical of early cretaceous floras the associated fauna includes dinosaurs hypsilophodontids allosaurs lepidosaurs chelonians birds fish including the lungfish ceratodus and insects the evidence of the biota as a whole suggests a warm to cool temperate relatively equable climate of moderate seasonality with no widespread winter freezing the complex mesozoic apparent polar wander path apw indicated for australia places victoria in high to polar palaeolatitudes ca 70 85 s during the early cretaceous this apw path is supported by paths for other gondwana continents the existence of the victorian early cretaceous forest and biotic communities through polar nights of about two to five months duration is difficult to accept evergreen species would have required relative equability of light whatever the temperature the dinosaurs foliage throughout the year and the lungfish warm to temperate conditions without freezing in view of the consistency of mesozoic palaeomagnetic results for gondwanaland and the enigmatic presence of mesozoic and early cenozoic fossil floras and faunas in very high northern palaeolatitudes the possibility of a reduced obliquity of the ecliptic in mesozoic early cenozoic time should be considered

high mg diorites derived from sanukitic hma magmas kyushu island southwest japan arc evidence from clinopyroxene and whole rock compositions abstract high mg diorites that have similar whole rock composition to high mg andesites hmas should not be simply interpreted as rocks solidified from the hma magmas because the high mg diorites may be mafic cumulates derived from a different magma from the hmas the hmas contain unique clinopyroxenes with higher mg and si than those of other sub alkaline series igneous rocks the mg and si are controlled by the source magma composition rather than its crystallized conditions such as pressure and temperature the chemical composition of clinopyroxenes would present important information for the investigation of the source of high mg diorites we considered the source of early cretaceous high mg diorites on kyushu island southwest japan arc based on their clinopyroxene and whole rock compositions the clinopyroxenes have similar chemical characteristics to those in hmas rather than those in other sub alkaline rocks moreover the whole rock compositions are equivalent to the sanukitic hma and do not show features of mafic cumulates this indicates that the high mg diorites solidified from sanukitic hma magmas it is generally believed that the sanukitic hma magmas involve the subduction of a young and or hot oceanic slab was situated in their genesis therefore the occurrence of the high mg diorites suggests that kyushu was situated in the tectonic setting of young and or hot slab subduction in the early cretaceous

a multi proxy approach to reconstructing sedimentary environments from the sperchios delta greece this paper presents an integrated approach to assess holocene environmental changes in the sperchios delta sperchios rift central greece a multidisciplinary study was carried out applying established analytical methods as well as exploring new techniques to detect past environmental conditions in a fluvio deltaic depositional system a series of six deep boreholes up to 50 m long and four shallow cores up to 6 m long from across the delta plain were studied in detail sedimentary facies were defined by changes in grain size and macro and microfaunal composition variability in mineral magnetic composition documented by changes in bulk magnetic susceptibility and 77k 293k and remanence parameters s 300 and arm sirm ratios as well as down core elemental variations obtained by scanning micro x ray fluorescence xrf provide constraints on the depositional changes related to the evolution of the sperchios delta correlations between elemental data derived by xrf analyses and grain siz

late quaternary depositional architecture of po and tevere river deltas italy and worldwide comparison with coeval deltaic successions abstract po and tevere rivers form two of the most important deltas of the whole mediterranean area detailed investigations have been carried out in the last decade beneath the present delta plains of these two river systems using borehole data correlation with the aid of radiocarbon dates and other dating methods pollens archaeology a detailed sequence stratigraphic framework has been constructed in both areas especially for the last glacial interglacial cycle regional subsidence combined with short term sea level fluctuations of relatively high amplitude played a fundamental role in creating subtracting accommodation during the long phase of falling sea level which followed the tyrrhenian substage 5e transgressive event a discontinuous record of this phase is present in the subsurface of the po plain whereas poor or no preservation has been detected in the tevere area progradational lowstand wedges accumulated during the last glacial maximum mostly in the central part of the basins far from the present deltas and are lacking in the study areas where a hiatal surface is invariably recorded below the transgressive deposits glacioeustasy exerted a major control on sedimentation in both areas during the latest pleistocene holocene sea level rise infilling of fluvial valleys and rapid landward migration of barrier lagoon systems in the context of wave dominated estuaries characterized the transgressive phase in both po and tevere systems in place drowning and transgressive submergence mechanisms of barrier migration were effective predominantly between 13 5 and 9 ka bp in contrast shoreface retreat was dominant in the late transgressive phase the maximum flooding surface mfs can be traced physically from continental to marine deposits and has similar characteristics in the po and tevere river systems being marked by peat layers or lagoonal deposits at landward locations and by distinctive lithological characteristics and micro and macrofossils assemblages basinwards above the mfs the early highstand systems tract records initially the filling of the lagoons followed by the rapid progradation of wave dominate delta systems and flanking strandplains autocyclic processes such as distributary channel avulsion delta lobe abandonment and local subsidence due to sediment compaction were the fundamental controlling factors on sedimentation during deposition of the hst the stratigraphic architecture of the post glacial po and tevere delta complexes closely resembles the basic facies successions documented from coeval deposits of wave dominated and wave influenced clastic coasts both locally within the mediterranean area and in other parts of the world our study emphasizes however some additional features and major differences with previously published depositional models including i the development of backstepping wave dominated estuaries during transgression ii consistent changes through time in the mechanism of barrier migration iii a later construction of the delta systems with respect to what traditionally considered

glacio eustatic control of continental shallow marine cyclicity from late quaternary deposits of the southeastern po plain northern italy abstract integrated sedimentological and micropaleontological foraminifera ostracods pollens investigations of a 173 m long continuous core in the subsurface of the se po plain reveal a cyclic facies distribution of continental to shallow marine deposits radiometric and pollen data enable an age attribution of the study units to the late middle pleistocene holocene glacioeustasy appears to have exerted a major control on facies development as documented by the close relationships between cyclic lithofacies patterns and the curves of eustatic fluctuation particularly relative sea level falls and lowstand phases were characterized by the development of alluvial sedimentation whereas major transgressive pulses and subsequent highstands are reflected by abrupt shifts to paralic and shallow marine deposits this facies architecture is paralleled by a distinctive pollen distribution reflecting the alternation of a glacial type of vegetation dominated by pinus and nonarboreal pollen types with interglacial mixed deciduous broad leaved forests

asymmetry in holocene river deltas patterns controls and stratigraphic effects abstract understanding controls on sediment distribution in river deltas is paramount to predicting facies relationships and stratal architecture most classifications of deltas have focused on subaerial plan morphology as a simplistic function of river tide and wave energy new work however is revealing the importance of subaqueous deposits and in particular shore parallel sediment redistribution in the shaping of delta planform delta asymmetry has emerged as an important characteristic reflective of patterns of alongshore sediment dispersal asymmetry has been described from onshore and offshore environments from several different types of modern deltas but aspects of asymmetry have not been fully documented and the degree to which these patterns are recorded in deltaic strata is not yet known this study is a comprehensive literature review of sediment distributions in modern deltas focusing on studies with high resolution geomorphic geophysical and geochronological datasets we reviewed 27 deltas using over 100 papers primarily from the past 15 20 years morphological facies and stratigraphic aspects were analyzed across the entire spectrum of deposits from the delta apex to the most distal muds of the prodelta we define quantifiable indices of asymmetry describing upcurrent vs downcurrent distribution of sediment volume sediment area sediment caliber and distributary channels most deltas are asymmetrical to some degree with respect to one or more of these parameters many deltas are increasingly skewed toward the downcurrent side from proximal to distal sub environments i e delta plain delta front prodelta some deltas are skewed toward the upcurrent side in one sub environment and toward the downcurrent side in another sub environment sand is preferentially deposited on the downcurrent side of most deltas but distributary channels tend to develop toward the upcurrent side the highest sand mud ratios are often on the upcurrent side in the lower delta plain but in the delta front these ratios are highest on the downcurrent side these complex patterns of asymmetry reflect different combinations of controls including discharge partitioning lobe abandonment and localized transgression plume deflection by coastal currents dominance of longshore current direction variable subsidence and other factors these processes may result in upcurrent downcurrent variations in clinoform geometry rates of progradation and stratal lapping relationships asymmetry has multiple aspects manifestations and controls even within a single delta but the long term preservation potential of these patterns likely varies depending on depositional setting and shoreline trajectory studies of ancient deltas will be better informed by recognizing the wide variety of controls on sediment distribution and avoiding the tendency toward a single model of delta asymmetry

late pleistocene holocene sediments on the spanish continental shelves model for very high resolution sequence stratigraphy abstract sequence stratigraphy analysis of high resolution seismic profiles geopulse uniboom and 3 5 khz of late pleistocene holocene sediments has been carried out on five sectors of the spanish continental margin four types of depositional settings are distinguished in these sectors 1 low subsident ramps alboran margin cadiz gulf 2 high subsident 2m kyr ramps alicante valencia 3 ria type morphology on the atlantic passive margin ria de muros and 4 fault scarp morphology systems with subsidence balearic margin a type 1 sequence is interpreted in all these sectors being composed of lowstand systems tract transgressive systems tract and highstand systems tract this conforms to the basic concepts of sequence stratigraphy and each systems tract correlates with a particular part of the last eustatic hemicycle characteristic shelf features such as terraces terraces with beach deposits and progradational sediment wedges evidence a complex stacking of lesser sub sequences in all the systems tracts which must be related to very short period sea level stillstands and fall we propose a very high resolution sequence stratigraphy model in which the last sea level hemicycle is punctuated by p cycles 4500 years which give rise to the neo glacial events h cycles 2200 950 years and c cycles 500 50 years these cycles interact with each other thus establishing the placing of the high and low sea levels this attention to detail 1 explains sedimentary evolution on both the shelf and upper slope during late pleistocene holocene time 2 illustrates some departures from the classical sequence stratigraphy model and 3 also demonstrates that the late pleistocene holocene eustatic curve is not one simple transgression but is modulated by three differing period cycle groups below the milankovitch band our model is delimited by fluctuating sea level during pleistocene holocene times such features should be identifiable on any continental margin however localized features occur due to subsidence and continental shelf morphology which determ ine the location and depth of sedimentary bodies generated in each eustatic cycle

recognition of interfluve sequence boundaries integrating paleopedology and sequence stratigraphy in shallow marine and coastal plain strata sequence boundaries are easily recognized at the base of incised valley fills between valleys however it is more difficult to recognize sequence boundaries where they are expressed as interfluve paleosols we suggest that interfluve paleosols can be most reliably identified using a combination of 1 stratigraphic position 2 field observations such as thickness structure color and degree of rooting and 3 micromorphological features such as bioturbation fabric clay coatings ferruginous features and siderite and barite only micromorphology permits recognition of temporal changes in drainage surface stability and protracted pauses in sedimentation that typify these surfaces this three part approach has been successfully employed to identify interfluve sequence bounding paleosols in the cenomanian dunvegan formation in alberta and british columbia canada

families of similar events and modes of oscillation of the conduit at yasur volcano vanuatu abstract we examined one year of seismic recordings collected in 2008 during a temporary experiment at yasur volcano vanuatu the volcano has a permanent strombolian activity that was at a relatively high level during most of our experiment with commonly at least one explosion per minute associated with this activity the network recorded intense seismicicity with hundreds of transients per day video recordings indicate that most of the high frequency transients are directly related to the strombolian explosions they also outline the presence of fewer signals which are not accompanied by any surface activity the classification of transient events recorded at a station close to the summit indicates that a significant part of the events exhibit waveform similarity this technique allows the identification of characteristic repeating events among the hundreds of thousands of transients recorded during the experiment most of the families of similar events are groups of explosion quakes eqs but a few are groups of long period events related to deeper processes by scanning the 9 months of continuous data available at the summit station with master events extracted from these families we reconstruct their temporal evolution our results show that several families dominate the activity with a few of them lasting for several months we show that their temporal evolutions can be used to probe changes in the structure or activity of the volcano we observe that a major change was induced by a m 7 3 subduction earthquake which occurred on april 9 2008 about 80 km from the volcano while this event did not change significantly the surface morphology of the volcano nor the intensity of the eruptive activity it interrupted the families as none of them is present both before and after the event this change in the waveforms can be explained by a drop in the seismic velocity of the volcano caused by the distal event numerous other transitions between families are observed sudden or progressive these can be interpreted as representative of changes in the eruptive dynamics the presence of similar eqs especially for impulsive explosions indicates that the source mechanism is reproducible and has a stable location for some periods this favors a source process based on the oscillation of the conduit or oscillation of the edifice in response to the explosive decompression of gas slugs at the free surface of the conduit our results suggest that the seismic activity of yasur is characterized by the presence of dominant modes of resonance of the conduit which may be influenced both by external and internal factors

transgressive depositional systems of the mississippi delta plain a model for barrier shoreline and shelf sand development abstract depositional sequences generated in the mississippi river delta plain consist of a regressive and a transgressive component the transgressive component has been considerably less studied but accounts for the majority of the surface area on the lower mississippi river delta plain and up to 50 percent of the total sequence thickness in shallow water deltas the development and preservation of transgressive depositional systems in abandoned delta complexes follows the process of transgressive submergence in which the horizontal component of reworking occurs during shoreface retreat combined with a vertical component of submergence acting to preserve the sequence the evolution of transgressive depositional systems in each of the abandoned holocene mississippi river delta complex s can be summarized in a three stage model beginning with stage 1 an erosional headland and flanking barriers in this stage regressive sand deposits contained within abandoned deltaic headlands are reworked by the eroding shoreface and dispersed longshore into contiguous flanking barriers enclosing restricted interdistributary bays submergence of the delta plain during relative sea level rise generates an intradeltaic lagoon separating the former stage 1 sand body from the shoreline forming stage 2 a transgressive barrier island arc the landward migrating barrier island arc is unable to keep pace with relative sea level rise and the retreating mainland shoreline resulting in submergence and the formation of stage 3 an inner shelf shoal following submergence the former barrier island arc sand body continues to be reworked into a marine sand body on the inner continental shelf during stage 3 this sequence of coastal evolution provides direct evidence of barrier island formation with each stage producing a distinctive stratigraphic signature the current sea level rise models of shoreface retreat and in place drowning developed for the u s atlantic continental shelf do not adequately explain either the morphology or the stratigraphy of transgressive mississippi river delta sand bodies current models of mississippi deltaic stratigraphy emphasize the deep water artificially maintained balize delta which differs considerably from the shallow water shelf phase delta complexes that are the primary depositional constituents of he holocene mississippi river delta plain

holocene evolution of the song hong red river delta system northern vietnam abstract the song hong red river delta located on the western coast of the gulf of bac bo tonkin in the south china sea formed as a result of the song hong sediment discharge throughout the holocene the river s sedimentary basin upstream from the delta plain is not large the delta plain comprises emerged tidal mangrove flats formed during the sea level highstand at 2 3 m 6 4 cal kyr bp and a beach ridge strandplain with straight to lobate beach ridges on the landward and seaward sides of the delta plain respectively the delta affords us the opportunity to examine river mouth morphodynamics comprehensively in relation to sediment discharge and sea level changes in this paper we describe the holocene evolution of the song hong delta system and the river mouth morphodynamics on the basis of seven sediment cores each 30 70 m long taken from the delta plain during 1999 2001 and 101 radiocarbon dates obtained from the core sediments sediments from the seven cores consisting of incised valley fills since the last glacial maximum can be divided in ascending order into fluvial sediments composed of gravelly sand and mottled clay tide influenced estuarine sediments containing shell and wood fragments and deltaic sediments composed of tide influenced sand and mud deposits in which the contents of sand and wood fragments increase upward by applying sequence stratigraphic concepts a transgressive surface can be identified at the gravelly sand mottled clay boundary and the maximum flooding surface can be identified at the estuarine deltaic sediments boundary the lowstand systems tract transgressive systems tract and highstand systems tract record 15 15 9 and 9 0 cal kyr bp respectively during the past 9 kyr the majority of the sediment discharged by the song hong accumulated in the incised valley and enhanced progradation at the river mouth the river mouth prograded from the bay head toward the gulf and its morphology changed from funnel shaped 9 6 cal kyr bp to straight 6 2 cal kyr bp and finally to lobate 2 0 cal kyr bp the morphological change from a funnel shaped to straight coast is interpreted to have been closely related to a hydrologic regime shift from a tide dominated bay head setting to a wave influenced open coast setting the cessation of the sea level rise at 6 cal kyr bp may have played only a small role in the change of river mouth morphology because the progradation rate decelerated from 22 to 4 m yr instead of accelerating at that time the river mouth morphodynamic change from straight to lobate was largely caused by an increase in the song hong sediment discharge from 17 27 9 2 cal kyr bp to 49 million t yr 2 0 cal kyr bp as a result of anthropogenic deforestation along the upper reaches of the song hong

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr