variations in mode of formation and temperature of oceanic deep waters over the past 125 000 years marked changes in the deep water temperature of the different oceanic basins during the past 125 kyr are revealed by a detailed comparison of the oxygen isotopic composition ofbenthicforaminiferafrom sediment cores taken from the norwegian sea and the pacific atlantic and southern oceans the last interglacial deep water temperatures were similar to the modern ones at the 5e 5d transition around 115 kyr bp the deep water temperatures dropped below approximately 0 c in the pacific and southern indian oceans in the atlantic ocean the deep water temperature dropped in 2 successive steps at 115 and 75ky bp the global ocean deep water temperatures were in the 0 to 1 c range for the whole of the last ice age isotope stages 4 2

3d architecture of lowstand and transgressive quaternary sand bodies on the outer shelf of the gulf of lion france abstract a restricted area 700 km 2 of the outer continental shelf in the gulf of lions western mediterranean sea has been surveyed in detail in order to reconstruct the 3d architecture of large quaternary sand bodies that are exceptionally well preserved in the western part of the rho ne delta data sources include digital very high resolution seismic swath bathymetry and some shallow cores in two dimensions the seismic data display a complex superposition of alternating seismic units consisting of high and low angle prograding clinoforms corresponding to high and low energy environments the combination of faunal and grain size analysis from shallow cores geometry of sedimentary bodies showed that these two types of seismic facies can be attributed respectively to upper shoreface and prodelta c settings despite a similar geometry in 2d it appears that the prograding sand units have very different 3d geometries lateral extent direction of progradation with respect to the paleoshorelines implying different sedimentary processes at least two major sand units have shore parallel orientations and can be mapped along the entire study area the mechanism responsible for the formation of these sand bodies seems similar to that described for many sharp based sand bodies from the stratigraphic record especially in the western interior seaway their isolated position on the shelf being related to forced regressions in contrast some other sand units have lobate shapes with divergent directions of progradation and limited lateral extent they are often overlying fluvial incisions and they pinch out landward it is still not clear whether they are related to some allocyclic or autocyclic processes like shifting of delta c lobes as observed on the texas coast the very high resolution and high quality of the seismic data have enabled us to characterise the three dimensional architecture of small scale sedimentary bodies the study has pointed out the variability of depositional processes and has given an insight on reservoir characteristics 1998 elsevier science ltd all rights reserved

impact of relative sea level and rapid climate changes on the architecture and lithofacies of the holocene rhone subaqueous delta western mediterranean sea abstract the modern rhone delta in the gulf of lions nw mediterranean is a typical wave dominated delta that developed after the stabilization of relative sea level following the last deglacial sea level rise similar to most other deltas worldwide it displays several stacked parasequences and lobes that reflect the complex interaction between accommodation sediment supply and autogenic processes on the architecture of a wave dominated delta the interpretation of a large set of newly acquired very high resolution seismic and sedimentological data well constrained by 14c dates provides a refined three dimensional image of the detailed architecture seismic bounding surfaces sedimentary facies of the rhone subaqueous delta and allows us to propose a scenario for delta evolution during the last deglaciation and holocene the subaqueous delta consists of parasequence like depositional wedges a few metres to 20 30 m in thickness these wedges first back stepped inland toward the nw in response to combined global sea level rise and overall westward oceanic circulation at a time when sediment supply could not keep pace with rapid absolute eustatic sea level rise at the younger dryas preboreal transition more rapid sea level rise led to the formation of a major flooding surface equivalent to a wave ravinement surface after stabilization of global sea level in the mid holocene accommodation became the leading factor in controlling delta architecture an eastward shift of depocentres occurred probably favoured by higher subsidence rate within the thick messinian rhone valley fill the transition between transgressive backstepping geometry and regressive prograding geometry para sequences resulted in creation of a maximum flooding surface mfs that differs from a classical mfs described in the literature it consists of a coarse grained interval incorporating reworked shoreface material within a silty clay matrix this distinct lithofacies results from condensation erosion which appears as an important process even within supply dominated deltaic systems due to avulsion of distributaries the age of the mfs varies along strike between ca 7 8 and 5 6 kyr cal bp in relation to the position of depocentres and climatically controlled sediment supply the last rapid climate change of the holocene the little ice age 1250 1850 ad had a distinct stratigraphic influence on the architecture and lithofacies of the rhone subaqueous delta through the progradation of two deltaic lobes in response to changes in sediment supply linked to rapid climate changes and to anthropic factors the rhone delta evolved from wave dominated to fluvial dominated and then wave dominated again

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

architecture of stacked quaternary deltas correlated with global oxygen isotopic curve a distinctive pattern of quaternary stacked prograded deltas and intervening transgressions on a rapidly subsiding continental margin in the eastern mediterranean has been dated from offshore wells simple modeling using the quaternary oxygen isotope record as a proxy sea level curve has demonstrated that this pattern is a consequence of sea level change the progradational pattern is dependent principally on the amount of time that is available between successive highstands to provide accommodation space by subsidence on rapidly subsiding continental margins the standard pattern of stacked deltas can be used as a chronological tool in undated quaternary seismic sequences

live dead comparison of benthic foraminiferal faunas from the rhone prodelta gulf of lions nw mediterranean development of a proxy for palaeoenvironmental reconstructions dead benthic foraminiferal faunas 150 m from the rhone prodelta gulf of lions nw mediterranean were analysed at 41 stations 15 100 m water depth sampled in june 2005 and september 2006 and compared to the living faunas investigated during previous studies at the same stations the comparison between dead and living assemblages enhances the understanding of taphonomic processes that may modify the composition of the dead faunas in this area we observed a loss of individuals from living to dead assemblages of species characterised by a fairly fragile test and therefore more prone to fragmentation or dissolution e g bolivina alata quinqueloculina tenuicollis allochthonous dead and or live specimens may be transported to some parts of the prodelta particularly the shallowest sites where hydrodynamic processes i e river flood storm swells longshore currents are more intense these specimens may originate from relict deltaic structures e g elphidium spp from the lobe of bras de fer or from surrounding areas e g ammonia beccarii forma beccarii from the river opportunistic species e g bulimina marginata cassidulina carinata characterised by high reproductive rates have much higher relative abundances in the dead than in the living fauna cluster analyses based on dead foraminiferal assemblages divide our study area into four main thanatofacies directly related to distinct local environmental conditions prevailing in the prodelta close to the river mouth ammonia beccarii forma beccarii and ammonia tepida are found in sediments subject to a high riverine influence i e bottom currents high organic and inorganic material input of continental origin elphidium species are abundant in the silty sandy relict deltaic lobe west of the river mouth which is characterised by strong longshore currents that disturb the benthic environment nonion fabum rectuvigerina phlegeri and valvulineria bradyana are found along the coast west of the rhone river mouth in the area defined as the river plume thanatofacies in the more stable and deeper prodeltaic area species known to feed on fresh phytodetritus e g bulimina aculeata marginata c carinata hyalinea balthica dominate the faunas since only minor variations in species relative abundances and spatial distributional patterns are observed between the living and the dead faunas we consider that our thanatofacies have not been influenced by substantial transport of dead tests this suggests that fossil benthic foraminifera can provide a reliable tool for investigating the development of the palaeo rhone prodelta

sea level changes an integrated approach sea level changes an integrated approach in october 1985 sepm sponsored a four day conference entitled sea level changes an integrated approach the purpose of the conference was to provide a forum for an interdisciplinary exchange of ideas on sea level changes and to provide an opportunity for integrating various types of evidence in approaching unresolved issues the conference was successful in bringing together scientists from industry academia and government representing all of the major geosciences disciplines presentations of many new papers plus significant releases of data that were previously held proprietary provided fertile ground for discussion this much cited volume represents the best of the material presented at the conference includes the early vail chart

natural environmental radiation mapping in parts of meghalaya india this paper presents new data on natural environmental radiation mapping in meghalaya for the first time in india two alternate methods have been used to map 1 a regional low density environmental radiation mapping by using radiation meters 2 high resolution radiation mapping of shillong basin using the data generated by an integrated litho and pedo geochemical sampling program using gamma ray spectrometric measurements on both rock and soils samples the variation in radio elemental concentrations and radiation levels are related to bedrock geology and structures the high levels of radiation levels are observed in the areas occupied by mylliem granite 3 935 msv a 51 r h 178 066 ngy s followed by south khasi batholith with pink feldspar 2 42 to 3 652 msv a 31 r h 109 502 165 249 ngy s graphitic schists avg 52 10 pgy s 1 06 msv a chlorite schist avg 51 16 pgy s 1 13 msv a phyllites avg 47 98 pgy s 1 06 msv a volcanics avg 46 9 pgy s 1 04 msv a the chlorite schist of tyrsad formation 21 r h 1 643 msv a 74 321 ngy s and barapani arenite 16 r h 1 21 msv a 54 773 ngy s tertiary sandstone 21 r h 1 633 msv a 73 885 ngy s shella subgroup 12 r h 0 914 msv a 41 376 ngy s langpars 13 r h 1 006 msv a 45 502 ngy s upper mahadek 26 r h 2 062 msv a 93 298 ngy s lower mahadek 38 r h 2 935 msv a 132 785 ngy s and the lowest environmental radiation levels are observed over sylhet traps 9 r h 0 725 msv a 32 786 ngy s the soils generally show higher radiation levels as compared to their bed rocks comparisons are made with high radiation areas of the world results showing that they are lower than high background radiation areas these radiation images are the first series of environmental images for meghalaya and will serve as the baseline data for the upcoming uranium mining projects in meghalaya baseline environmental radiation images are necessary information to policy makers and provide a sound basis for addressing the public concerns for radiation levels

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

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

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

non linear response of the golo river system corsica france to late quaternary climatic and sea level variations disentangling the impact of climatic and sea level variations on fluvio deltaic stratigraphy is still an outstanding question in sedimentary geology and geomorphology we used the golo river system corsica france as a natural laboratory to investigate the impact of late quaternary climate and sea level oscillations on sediment flux from a catchment and on fluvio deltaic stratigraphy we applied a numerical model pacmod which calculates catchment sediment production and transport and compared modeling output to the sedimentary record of the golo alluvial coastal plain whose chronology was reinterpreted using new optical stimulated luminescence osl ages on feldspars our modeling osl ages and geomorphological results indicate that the two main phases of braidplain development in the golo alluvial coastal plain occurred during the cold dry phases of mis5 and during the late mis4 early mis3 as a consequence of high catchment erosion rates and low water discharge incision and sediment reworking occurred during sea level low stand periods mis4 and late mis3 mis2 high sediment flux pulses from the catchment outlet were generated during the lateglacial and early holocene as a result of the release of sediments previously stored within the catchment and enhanced snowmelt our results suggest a non linear response of the golo river system to climatic and eustatic changes caused by sediment storage within the catchment and geomorphological thresholds this indicates that a direct comparison between palaeo climate and stratigraphy is not possible without considering catchment sediment storage and sediment transport delays out of the catchment

reconstruction of late quaternary sea and lake level changes in a tectonically active marginal basin using seismic stratigraphy the gulf of cariaco ne venezuela abstract the gulf of cariaco is a marginal basin located between the cariaco basin and the paria gulf offshore ne venezuela along a system of active right lateral strike slip faults it is connected to the caribbean sea via a shallow 58 m deep sill implying that the gulf was disconnected from the global ocean during eustatic lowstands a dense grid of high resolution reflection seismic profiles has been used to determine the overall tectonic structure of the gulf and to establish the seismic stratigraphy of its sedimentary infill six unconformity bounded seismic stratigraphic units were identified in the upper 200 m of the sedimentary infill detailed seismic stratigraphic and seismic facies analysis allowed defining a series of sedimentary features that can be used as indicators of past sea or lake level in the gulf of cariaco i delta offlap breaks ii evaporites and iii erosional unconformities using accurate measurements of these various indicators at several locations in the gulf and a simple total subsidence model a relative sea lake level history encompassing the last 130 kyr could be reconstructed in periods of connection with the open ocean reconstructed relative sea level correlates well with eustatic sea level in times of disconnection distinct lake level fluctuations occurred which sometimes resulted in total dessication of the gulf lake level fluctuations appear to correlate with major heinrich events stadials and interstadials mis 4 the lgm and the younger dryas were thus identified in the gulf of cariaco sedimentary record the last reconnection to the caribbean sea occurred during mwp1b around 11 5 kyr the very good fit of the cariaco sea lake level curve with the eustatic sea level curves both in terms of amplitude and of timing underscores potential for future paleoclimate research of the sedimentary record contained in this marginal basin despite its active tectonic setting

terrestrial 10 be and electron spin resonance dating of fluvial terraces quantifies quaternary tectonic uplift gradients in the eastern pyrenees the 120 km longt et river flows out of the pyrenees to the mediterranean by displaying a mappable sequence of quaternary alluvial units between the pleistocene frontal moraines of the high range and the offshore sedimentary depocentres its 1400 km 2 watershed is well suited to quantifying gradients of topographic uplift five main generations of terrace treads had previously been inferred from constrasts in regolith weathering features but here we present the first radiometric age constraints based on 15 esr sediment burial ages covering the full sequence and 3 vertical tcn age profiles restricted to three mid sequence terraces analytically robust results were obtained for the oldest and uppermost terrace t5 esr age 1099 179 ka for t3b esr age 374 47 ka mis 10 and for t2 esr age 174 44 ka mis 6 these results are consistent with the contrasts in weathering grade of the deposits the tcn profiles only yielded minimum exposure ages but provided precise post depositional denudation rates for the fluvial terrace treads the land to sea geometry of the chronosequence also provided clues about valley incision rates in response to topographic uplift during the last 1 ma based on a critical review of similar data obtained for other mediterranean and atlantic watersheds in the pyrenees the full regional correlation reveals that post orogenic topographic uplift was substantial and relatively uniform throughout the entire mountain range patterns and magnitudes suggest a shared probably subcrustal driving mechanism of neogene and quaternary mountain growth with only subsidiary influence from isostasy and climatic forcing

sedimentary sequences in the gulf of lion a record of 100 000 years climatic cycles abstract the wide continental shelf of the gulf of lion up to 70 km has been the object of numerous investigations since the early days of oceanography yet the question of sequences duration the mechanisms of deposition and factors implied remained unanswered a study of a very dense grid of very high resolution vhr seismic reflection sparker data associated with surficial cores both collected by ifremer between 1992 and 2001 on the outer shelf and upper slope offshore of sete in the languedoc region gives a new insight into these issues analysis of the 3d geometry of the sedimentary record reveals a basic depositional pattern consisting of a pair of horizontally juxtaposed and downlapping prisms prism pi with low angle clinoforms results obtained from integrating lithology palynology micropaleontology seismic stratigraphy stratigraphic simulation support the hypothesis that the basic depositional pattern records a 100 000 years glacioeustatic interglacial glacial cycle as previously suggested by aloisi aloisi j c 1986 sur un modele de sedimentation deltaique contribution a la connaissance des marges passive these de doctorat d etat universite de perpignan 162 pp prisms pi corresponds to deposition at high sea level and prisms pii to deposition during low sea level at glacial maxima five sequences of paired prisms capped by five major erosion surfaces have been identified and modelled showing that the corresponding glacioeustatic cycles the last five cycles at least are recorded on the shelf of the western part of the gulf of lion

high resolution stratigraphic forward modeling of a quaternary carbonate margin controls and dynamic of the progradation abstract the relationships between the margin sedimentary regime and the platform progradation are studied using forward stratigraphic numerical simulations on the leeward western prograding margin of the great bahama bank gbb during the quaternary 1 7 0 ma the corresponding sedimentary regime in the slope and the platform is well known from the odp leg 166 and bahamas drilling project wells located along the western line seismic transect however the sedimentary regime on the margin is not well established the coral reefal margin observed before between 1 7 and 0 8 ma in the well clino is not active anymore at present day and the holocene sedimentary regime is geometrically unable to account alone for the progradation this study is based on three 2d high resolution forward stratigraphic numerical modeling experiments with the software dionisosflow that include the platform margin and slope domains on the western line section in the same sedimentary models the results are compared to the six sedimentary cores and to the present day bathymetry in order to identify the more realistic scenario the three experiments test different models of carbonate sediment production and transport experiment 1 shows that the highstand shedding of the fine grained uncemented platform production is unable to reproduce the progradation and the present day profile experiments 2 and 3 incorporate cemented facies in the margin with the best results obtained with the cemented marginal wedges produced in experiment 2 during platform emersion from these results a high resolution interpretation of the margin seismic section is proposed this study shows that the platform progradation can be decoupled from the highstand shedding of the fine grained platform production it is dependent on the accumulation in front of the steep margin of coarse or cemented material before 0 8 ma this corresponds to the coral reef identified in clino the transition after 0 45 ma to 100 kyr large eustatic cycles with total platform flooding created two distinct marginal regimes 1 during platform flooding aggrading accumulation of non skeletal sands and 2 during platform emersion prograding cemented marginal wedges produced in situ

quaternary stratal architecture of the barcelona prodeltaic continental shelf nw mediterranean abstract the barcelona continental shelf is part of a 6 20 km wide canyon bounded shelf located off the city of barcelona ne spain this study integrates newly acquired high resolution single channel seismic reflection profiles and available lithological information of the barcelona shelf to describe its late quaternary architecture and the role of global glacio eustatic fluctuations and local factors in its development four major sequence boundaries are identified throughout the seismic dataset they are tentatively correlated with the four last 4th order 100 120 ka high amplitude late quaternary glacio eustatic lowstands most of the stratigraphic record is formed by falling stage systems tracts with forced regressive deposits which confers a general progradational vertical stacking pattern transgressive systems tracts are represented by continuous units confined directly off river sources and on previously eroded surfaces stillstand deposits are difficult to recognize in the available dataset the uppermost seismic unit corresponds to the holocene shore parallel besos and llobregat joint prodelta affected by the prevailing south westward circulation the general architecture of the late quaternary barcelona shelf deposits is determined by global glacio eustatic cycles however the lateral variability of the seismic units depends largely on local factors such as i the position of sediment sources essentially the llobregat river ii differential subsidence and especially sediment compaction iii erosive processes such as canyon incision mass wasting or wave base dynamics and iv underlying geomorphic restrictions

the timing of postglacial coastal adaptations in eastern iberia a bayesian chronological model for the el collado shell midden oliva valencia spain abstract el collado is an open air site containing evidence of 14 burials and a shell midden archaeological deposit with different phases of human occupation dated to the early holocene previous studies have produced 14 radiocarbon dates using bone collagen samples from human burials however no attempt has been made to date the stratigraphic sequence to address the formation time of the shell midden and establish a chrono stratigraphic framework for the study of bio archaeological and cultural assemblages we critically evaluate the available radiocarbon record of the site and present 6 new ams radiocarbon dates on ungulate bones with anthropic fractures and bivalves from the three major stratigraphic horizons then we integrate our results with previously published ams radiocarbon determinations on human samples into a chronological bayesian model constraining the radiocarbon distributions with prior information about the samples stratigraphic provenance finally we correlate the results of the chronological model with the regional archaeological sequence and the available data on coastal evolution at regional and local scales the vertical distribution of the radiocarbon dates makes evident some stratigraphic disturbance caused by the repeated presence of pit graves agricultural activities and low stratigraphic control of the excavation process however once the problematic determinations are identified as outliers the remaining radiocarbon dates grouped according the major stratigraphic divisions and the calibrated distributions modelled constrained the resulting bayesian phase model reveal high agreement index ac 103 the shell midden formation took place from the bottom of the sequence spanning 1022 1965 calibrated years ci 95 4 the occupations documented at phase 1 level iv are dated to the early holocene 9828 9551 cal bp the phase 2 level ii encompass radiocarbon evidence of both burial and occupational activities dated to 9437 to 8477 cal bp spanning 779 985 calibrated years ci 95 4 finally the phase 3 level i records late mesolithic occupations deposited between 8509 and 8391 cal bp for the start boundary and 8499 8060 cal bp for the end boundary ci 95 4 there are no individual radiocarbon dates during or postdating the chronological span of the 8 2 ka climatic event 8300 8140 cal bp

the active submarine nw termination of the south aegean active volcanic arc the submarine pausanias volcanic field abstract methana peninsula shows the longest recorded volcanic history at the western end of the south aegean active volcanic arc including volcanic products from the upper pliocene to recent times the volcanic rocks comprise widespread dacite domes and andesite lava flows from several small volcanic centers and are only imprecisely dated in this paper the integrated analysis of swath bathymetry side scan sonar data and high resolution seismic reflection profiles correlated with core samples has allowed detailed mapping characterization and precise chronological identification of the pausanias submarine volcanic field activity offshore northern methana six volcanic cones or domes are recognized typically 1 3 km in diameter some elongated ne sw and some with a small central crater on their flanks the acoustically reflective volcanic rocks pass laterally into incoherent transparent seismic facies interpreted as volcaniclastic deposits possibly including hyaloclastites that interfinger with the regional basin sediments a sea bottom hummocky field is interpreted as volcanic avalanche and appears to be the submarine continuation of the volcaniclastic apron of northern methana peninsula a robust chronostratigraphic framework has been established based on the recognition of shoreline progradational units and their connection with quaternary eustatic sea level cycles relative dating of the different phases of submarine volcanic activity during the upper quaternary has been achieved by correlating the imaged volcaniclastic flows interlayered within the chronostratigraphically dated sediments dating by stratigraphic position relative to 2d imaged eustatic sea level clinoform wedges appears to be more precise than radiometric methods on land three main submarine volcanic events ve are recognized ve3 at 450 ka a less precisely dated interval at 200 130 ka ve2 and ve1 at 14 ka based on chronostratigraphic constraints subsidence rates of 0 16 0 008 m ka in between marine isotopic stages 6 and 12 and 0 19 0 009 m ka in between marine isotopic stages 12 and 16 were estimated for the marine basin north of methana the morphological similarity to the onshore volcanoes of methana peninsula implies that magmatic constructive processes were dominant regardless of whether in air or in water the upper quaternary submarine volcanic rocks of methana differ from those known from stratovolcanoes elsewhere in the mediterranean e g kos nisyros stromboli and in other volcanic arcs e g montserrat st vincent in the submarine development of domes or small cones the paucity of volcano flank failure deposits and the lack of explosive events pausanias volcanic products date the onset of ne sw faulting as well as the following tectonic phase of e w striking faults possibly related to basin inversion caused by a major rifting phase that also affected most of the south aegean arc and the adjacent gulfs of corinth and argolikos

back to basics of sequence stratigraphy early miocene and mid cretaceous examples from the new jersey paleoshelf abstract many sequence stratigraphic approaches have used relative sea level curves that are dependent on models or preconceived notions to recognize depositional sequences key stratal surfaces and systems tracts leading to contradictory interpretations here we urge following basic sequence stratigraphic principles independent of sea level curves using seismic terminations facies successions and stacking patterns from well logs and sections and chronostratigraphic data to recognize sequence boundaries other stratal surfaces parasequences and systems tracts we provide examples from the new jersey siliciclastic paleoshelf from the 1 early miocene using academic based chronostratigraphic seismic core downhole and core log data and 2 mid cretaceous using commercial well log seismic and biostratigraphic data we use classic criteria to identify sequence boundaries on seismic profiles by reflection terminations onlap downlap erosional truncation and toplap in cores by surfaces of erosion associated with hiatuses detected using biostratigraphy and sr isotope stratigraphy and changes in stacking patterns and in logs by changes in stacking patterns maximum flooding surfaces mfss are major seismic downlap surfaces associated with changes from retrogradational to progradational parasequence stacking patterns systems tracts are identified by their bounding surfaces and fining generally deepening and coarsening generally shallowing upward trends in cores and well log stacking patterns our miocene examples of sequences m5 4 17 7 16 1 ma and m5 8 20 1 19 2 ma illustrate how basic sequence stratigraphic techniques reveal higher order sequences within myr scale composite sequences our mid cretaceous examples from the new jersey shelf provide a paleoshelf transect spanning the great stone dome to the outer continental shelf to identify parasequences sequences and systems tracts this sequence stratigraphic framework provides insights into myr scale coeval depositional environments across the paleoshelf and reservoir continuity and highlights the application of basic sequence stratigraphic criteria to reservoir scale evaluation not only for oil and gas resources but also for carbon storage

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

anatomy of an early paleozoic subduction complex in the central appalachian orogen abstract the greenwich slice of the hamburg klippe a taconic allochthon in the eastern pennsylvania appalachian orogen is part of a subduction complex that formed during early paleozoic crustal convergence it consists chiefly of turbidite sandstone and hemipelagic mudstone of middle ordovician age 85 and sequences of red and light green pelagic mudstone deep water limestone and chert of early middle ordovician age 14 additional minor lithologies include pebbly mudstone and boulder conglomerate and basic intrusive and extrusive rocks the dominant lithologies of the greenwich slice are arranged in fault bounded sequences of pelagic deposits overlain by channelized turbidite sandstone and hemipelagic mudstone these sequences are interpreted to record migration of a site on oceanic lithosphere from an abyssal plain setting toward and ultimately into a trench by middle ordovician time the channelized turbidite deposits were transported parallel to the continental margin northeast southwest and there are no proximal to distal sedimentologic variations along the length of the greenwich slice these characteristics suggest that the turbidites accumulated on part of an elongate submarine fan that occupied the floor of the trench or alternatively within laterally migrating channels along the floor of a large trench axis channel petrographic characteristics of the inferred trench fill turbidite deposits suggest that the longitudinal dispersal system may have been supplemented by transversely supplied sediment calculated sedimentation rates of the middle ordovician trench fill deposits and estimated plate convergence rates are consistent with accumulation of the turbidites as part of a trench wedge rather than a fan

natural controls of fluvial denudation rates in major world drainage basins we present a new compilation of estimates of modern rates of mechanical and chemical denudation for externally drained basins exceeding 5 105 km2 in area these estimates are based on sediment and solute load data selected in order to represent natural rates as far as possible chemical denudation rates have been calculated by deducting the nondenudational component of solute load mechanical denudation rates range from 1 mm kyr 1 for the st lawrence and dnepr basins to 670 mm kyr 1 for the brahmaputra basin chemical denudation rates vary from 1 mm kyr 1 kolyma niger nile and rio grande basins to 27 mm kyr 1 chiang jiang basin the kolyma basin has the lowest 4 mm kyr 1 and the brahmaputra basin the highest overall rate of denudation 688 mm kyr 1 relationships between denudation rates and a range of morphometric hydrologic and climatic variables are investigated through correlation and regression analysis morphometric variables such as mean local relief are accurately calculated for large basins for the first time by using the national geophysical data center 10 minute topographic database variables expressing basin relief characteristics and runoff are found to be most strongly associated with both mechanical and chemical denudation rates with more than 60 of the variance in total denudation being accounted for by basin relief ratio and runoff basin area runoff variability and mean temperature however are only weakly associated with rates of denudation although direct comparisons cannot be made it appears that rates of basin denudation derived from present day mass flux estimates are not overall significantly different from estimates of long term rates based on sediment volume and thermochronologic data it therefore appears that the key factors identified as controlling denudation rates here are also applicable to the geological time spans relevant to the interaction between tectonic and denudational processes

the changing architecture of sea level lowstand deposits across the mid pleistocene transition south evoikos gulf greece abstract on subsiding continental shelves the style of stacked coastal and deltaic progradational packages is directly dependent on relative sea level changes in the past 0 6 ma sea level change has been dominated by asymmetric 100 ka eustatic sea level cycles whereas the record of sea level changes in earlier pleistocene progradational sequences is less clear in a steadily subsiding basin in which accommodation balances sediment flux the depth of a eustatic lowstand determines the paleo depth of the deepest clinoform inflection point and the seaward limit of the erosional transgressive surface whereas the duration of a lowstand controls the amount of progradation that takes place we report high resolution seismic profiles of an exceptionally preserved coastal progradational sequence from a coastal embayment in the aegean sea that is subsiding at 100 m ma the seismic profiles show clinoforms of smaller amplitude and volume that were deposited before the 100 ka cyclic progradational units this contrasts with literature reports of complexity in progradational sequences at that time we assume that published stacked benthic foram o isotope records are a good proxy for the duration and a reasonable proxy for the amplitude of pleistocene eustatic sea level cycles the mis 6 5 eustatic sea level rise is recognised based on sedimentation rates from cores the underlying major progradational units are correlated with the long duration extreme lowstand 100 ka cycles of mis 6 12 and 16 changes in the elevation of lowstand inflection points in clinoforms are used to tentatively extend the record back to mis 38 by comparison with the benthic foram proxy the deposits of the higher and longer highstands of mis 25 31 and 37 are also recognised this record provides a testable template for future studies of short early pleistocene sections on land and raises questions of detail about parts of the published 18 o records it independently supports the recent evidence that the mid pleistocene transition was an abrupt event with an extreme lowstand in mis 22

the late oligocene early miocene himalayan belt constraints deduced from isotopic compositions of early miocene turbidites in the bengal fan abstract we present a mineralogical and isotopic study of early miocene turbidites from the bengal fan which are the oldest sediments recovered during odp leg 116 clay fractions are dominated by illite and chlorite and have low 18o 11 16 the clays are dominantly derived from a metamorphic precursor by physical erosion and have undergone only minor low t water rock exchange and chemical weathering sr and nd isotope analysis of silt and clay fractions and coarse muscovite biotite and feldspar fractions are remarkably similar to those of the presently exposed high himalaya crystalline hhc sequence the data show that a close analogue of the hhc was already subaerially exposed to active erosion during early miocene rb sr data on the biotite separates has been used to evaluate the time elapsed between cooling through the closure temperature for sr in biotite in the hhc ca 325 c and final sedimentation in the bengal fan despite the large uncertainties in the initial 87 sr 86 sr values of sedimentary mixtures our estimates of the elapsed time between cooling and deposition are short 4 14 ma assuming a transport time scale 1 ma deduced exhumation rates are in the same range of modern values 1 3 mm yr since ca 30 ma given that a the rocks exposed at the surface b the style of weathering and c rates of exhumation were similar to the present we infer that the factors controlling erosion of the early miocene himalayan belt were also similar to the present the data suggest that the early miocene himalayan belt had significant relief and induced orographic effects on precipitation similar to the modern mountain range it appears that the thrusting along the main central thrust mct or similar structures has uplifted metamorphic basement analogous to the present hhc at sufficiently high rate to maintain steep relief throughout miocene time despite high average erosion rates

geomorphological evidence for fluvial change during the roman period in the lower rhone valley southern france abstract the hydrological and geomorphological dynamics of the lower rhone river southern france are studied during the roman period 2nd 1st centuries bc 2nd 3rd centuries ad the crossing of archaeological and radiocarbon dating methods allow to study events at a pluridecadal to centennial scale from the avignon town to the delta the 15 sites where roman fluvial dynamics were recorded show higher flooding frequencies higher energy levels during floods rises in the marshes or groundwater levels and or active morphological dynamics such as channel migrations from 1st century bc to 1st 2nd centuries ad with respect to the encircling periods although this fluvial change does not reach the amplitude of great climatic events such as the little ice age in the rhone valley we show that it is also perceived in other parts of the catchment and could have a climatic origin however this event is not recorded in the immediate mediterranean environment of the lower rhone so that the rhone appears to efficiently transmit a foreign climatic change

late pleistocene holocene deposits of the rhone inner continental shelf france detailed mapping and correlation with previous continental and marine studies very high resolution seismic data acquired on the rhone continental shelf were used to address the detailed morphology of late pleistocene and post glacial units from 18 000 yr bp to the present two groups of units can be distinguished 1 lower units that are mainly the product of variations in relative sea level they comprise the last pleistocene regressive deposits made of alluvial sheets u0 u1 and above transgressive deposits that can be divided into backstepping transgressive units u3 and u4a deposited during the landward retreat of the river mouth and transgressive units u4b u4c laid down during the inundation of the shelf a prograding littoral lagoon system u5 u6 indicating a fluctuation during the rise in sea level caps the transgressive units this work has emphasized the complexity of these depositional environments mainly related to a river system situated near the current petit rhone 2 upper units that make up the recent rhone delta and correspond to the current highstand systems tract hst developed since the stabilization of relative sea level seven prodeltaic lobes have been identified u7 u13 two of them are bilobate u7 and u8 and date from a period when the delta was split as a result of the fluviatile system being progressively divided into several channels other prodeltaic lobes u9 u10 are stacked in front of the distributary s outlet recording several periods of outflow the results show a strong correlation with studies on land the distribution of recent prodeltaic lobes was constrained by canalization of the rhone river to prevent the effects of climatic crises or other natural disasters

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