high resolution sequence stratigraphic analysis of late quaternary deposits of the changhua coastal plain in the frontal arc continent collision belt of central taiwan abstract detailed analysis of the sequence stratigraphy in 30 cores from the late quaternary deposits of the changhua coastal plain provides a 25 ka record of the depositional history of a region situated in the frontal arc continent collision belt of taiwan twenty five lithofacies and nine facies associations are recognized an alluvial plain was the dominant feature during a pronounced sea level fall at 25 20 ka ago between 20 and 10 ka alluvial fans were deposited along the western front of the pakua tableland during movement along the changhua fault and a local sag basin was produced no other deposits in the seaward area are recognized between 20 and 16 ka or in the landward area between 20 and 10 ka between 16 and 6 ka the changhua coastal plain experienced rising sea level and retrogradational deposition from 16 to 10 ka estuarine deposits lower transgressive systems tract were deposited and the base of these deposits defines the last glacial maximum lgm unconformity sequence boundary now preserved in four regions to the east of the plain from 10 to 6 ka shelf shoreface and lagoonal deposits upper transgressive systems tract were laid either on top of the estuarine deposits or directly on the lgm unconformity surface by about 7 6 ka sea level had reached its peak maximum flooding surface and shelf and marginal marine sediments covered most of the study area after 6 ka the highstand was dominated by progradation of offshore transition shoreface lagoonal tidal channel tidal flat and alluvial plain deposits one thousand year old fluvial deposits in incised channels are preserved in the central part of the changhua coastal plain since then fluvial channels shifted southward to the present day chuoshuei river the depositional patterns in this tectonically active area during the last interglacial period reflect the complex interplay between high frequency sea level fluctuations tectonics subsidence and uplift and autocyclic processes in the seaward area however fluctuations in sea level were clearly the dominant factor in controlling the nature of depositional facies

the stratigraphic evolution of a large back barrier lagoon system with a non migrating barrier abstract lake st lucia the largest estuarine system in africa is enclosed by a 120 m high compound quaternary barrier dune system in northern kwazulu natal south africa it comprises several discrete sedimentary basins within a single shallow back barrier water body this paper reports the first very high resolution seismic study of the system seven seismic units a g are identified and interpreted based on their geometry acoustic properties and a sediment coring programme the units are bounded by regionally developed sequence boundaries and lower order unconformity surfaces corresponding to bay and tidal ravinement and hiatus surfaces the lowermost subaerial unconformity formed during regression related to late pliocene hinterland uplift initial infilling of this surface in the proximal areas reflects estuarine sedimentation in a mixed wave and tide dominated system during the subsequent lowstand and early transgressive systems tracts overlain by prograding highstand deltaic deposits that developed as sea levels began to stabilise distally this cycle of sedimentation is initially reflected by the infilling of a similar estuarine system that gradually transitioned to a back barrier lagoon superimposed stillstands drove imbalances in the rate of sediment supply and accommodation space and this coupled with the development of an early barrier complex caused lagoon aggradation and shallowing a second similar trend is repeated for the recent postglacial sea level cycle there appears to be no preservation of the intervening pleistocene cycles of erosion and deposition the system is capped by estuarine lacustrine deposits the onset of lower energy estuarine lake conditions began 6235 cal bp in north lake and started earlier in the proximal false bay owing to sheltering by the antecedent barrier of a rocky peninsula this study reveals a markedly different evolutionary history in adjacent basins of the same back barrier system during two full sea level cycles these are attributed to a long established non migrating barrier and to the influence of antecedent conditions on the system response to transgression unlike the us atlantic margin where migrating barriers truncate the infilling sequences the main stratigraphic unconformities within each fill sequence correspond to tidal and bay ravinement surfaces

sedimentary facies and evolution in the qiantang river incised valley eastern china abstract this paper deals with the sedimentary facies and evolution of the qiantang river qr estuary and the characteristics and formation of the incised valley sequences and the related shallow biogenic gas reservoir on the basis of analysis of over 500 cores the result shows that since the last glaciation the late quaternary formation of the qr estuary area underwent three stages 1 deep cutting stage 2 rapid filling stage and 3 burial stage the fall of global sea level during the last glacial maximum enhanced the fluvial gradient and river cutting resulting in the formation of the large scale qr and taihu incised valleys with the interfluve being exposed to air on both flanks of the incised valley fluvial terraces at the elevations are present near the present qr estuarine mouth corresponding to 60 70 90 100 and 115 125 m burial depths the valleys were filled rapidly with fluvial sediments during the post glacial period with the rise of sea level the river mouth migrated to landward and backwater and retrogressive aggradation was enhanced the qr and taihu incised valleys are associated with an early filling and transgressive channel infilling sequence formation and a late filling and transgressive floodplain estuary formation subsequently the qr valley was buried under estuarine marine and estuarine sand bar sediments from bottom to top the incised valley successions can be grouped into four sedimentary facies river channel floodplain estuary estuary shallow marine and estuary sand bar the thickness of the river channel infilling deposits is controlled mainly by base level rising backwater retrogressive aggradation and neotectonism further localized thickening took place where deeper scour pools were present in the incised valley or fluvial terraces were formed during the fall of elative sea level during the deposition of the floodplain estuary facies the conditions of sea level rise tidal regime sediment supply and accommodation space were suitable for the development of a tidal ridge system the sand lenses associated with this facies may represent a tidal ridge system in the incised valley at the later stage when the estuarine sand bars were formed the sedimentary conditions were no longer favourable resulting in absence of sand ridge deposits biogenic gas is stored in the floodplain estuary sand lenses of the incised valleys the changjiang river provides the major sediment supply for the qr estuary sand bar and the qr carried sediments constitute only a small portion of the deposits

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

structure age and origin of the bay mouth shoal deposits chesapeake bay virginia abstract the mouth of chesapeake bay contains a distinctive shoal complex and related deposits that result from the complex interaction of three different processes 1 progradation of a barrier spit at the southern end of the delmarva peninsula 2 strong reversing tidal currents that transport and rework sediment brought to the bay mouth from the north and 3 landward bayward net non tidal circulation and sediment transport together these processes play a major role in changing the configuration of the estuary and filling it with sediment the deposits at the mouth of the bay hold keys both to the evolution of the bay during the holocene transgression and to the history of previous generations of the bay the deposit associated with the shoals at the mouth of the bay the bay mouth sand is a distinct stratigraphic unit composed mostly of uniform gray fine sand the position and internal structure of the unit shows that it is related to near present sea level and thus is less than a few thousand years old the processes affecting the upper surface of the deposit and the patterns of erosion and deposition at this surface are complex but the geometry and structure of the deposit indicate that it is a coherent unit that is prograding bayward and tending to fill the estuary the source of the bay mouth sand is primarily outside the bay in the nearshore zone of the delmarva peninsula and on the inner continental shelf the internal structure of the deposit its surface morphology its heavy mineral composition bottom current studies comparative bathymetry and sediment budgets all suggest that sand is brought to the bay mouth by southerly longshore drift along the delmarva peninsula and then swept into the bay in addition to building the southward and bayward prograding bay mouth sand these processes result in sand deposition tens of kilometers into the bay

late neogene and quaternary evolution of the northern albemarle embayment mid atlantic continental margin usa seismic surveys in the eastern albemarle sound adjacent tributaries and the inner continental shelf define the regional geologic framework and provide insight into the sedimentary evolution of the northern north carolina coastal system lithoand chronostratigraphic data are derived from eight drill sites on the outer banks barrier islands and the mobil 1 well in eastern albemarle sound within the study area parallel bedded gently dipping miocene beds occur at 95 to n160 m below sea level m bsl and are overlain by a southward thickening pliocene unit characterized by steeply inclined southward prograding beds the lower pliocene unit consists of three seismic sequences the 55 60 m thick quaternary section unconformably overlies the pliocene unit and consists of 18 seismic sequences exhibiting numerous incised channel fill facies shallow stratigraphy b40 m bsl is dominated by complex fill patterns within the incised paleo roanoke river valley radiocarbon and amino acid racemization aar ages indicate that the valley fill is latest pleistocene to holocene in age at least six distinct valley fill units are identified in the seismic data cores in the valley fill contain a 3 6 m thick basal fluvial channel deposit that is overlain by a 15 m thick unit of interlaminated muds and sands of brackish water origin that exhibit increasing marine influence upwards organic materials within the interlaminated deposits have ages of 13 11 cal ka the interlaminated deposits within the valley are overlain by several units that comprise shallow marine sediments bay mouth and shoreface environments that consist of silty fine to medium grained sands containing open neritic foraminifera suggesting that this area lacked a fronting barrier island system and was an open embayment from 10 ka to 4 5 ka seismic data show that initial infilling of the paleo roanoke river valley occurred from the north and west during the late pleistocene and early holocene later infilling

palaeo drainage incised valley fills and transgressive systems tract sedimentation of the northern kwazulu natal continental shelf south africa sw indian ocean abstract two sequence boundaries are recognised in seismic data collected from the narrow northern kwazulu natal continental shelf these correspond to late cretaceous and latest pleistocene last glacial maximum lgm periods of sea level fall where fluvial incision into the shelf resulted in several incised valleys having formed in both examples the ensuing transgressive valley fills document an evolution from fluvially dominant sedimentation to classic backbarrier estuarine conditions central estuary basin sedimentation is most prominent within each fill and is separated from the underlying fluvial sediments by bayline ravinement processes tidal ravinement surfaces separate the upper estuarine sequences from barrier and shoreface deposition most easily observed in the latest pleistocene holocene valley fills where a holocene unconsolidated sediment wedge overlies the estuarine fill the wedge itself is characterised by two packages of sediment separated by a regionally occurring wave shoreface transgressive ravinement surface which crops out as a semi indurated shell hash in the mid to outer shelf late cretaceous examples are capped by deposits exhibiting oblique parallel to wavy reflectors interpreted as increasingly energetic deposits analogous to flood tide deltaic sedimentation valley incision and fill are linked to two onshore coastal lake systems lake sibaya and lake st lucia and appear to be the product of barrier breaching and fluvial re adjustment to baseline shifting of these systems during forced regression lake st lucia exhibits a composite palaeo drainage channel where both sequence boundaries merge within the lake margins lake sibaya has two distinct palaeo channels for each sequence boundary episode a late cretaceous channel which fed a small incised valley within which a modern day submarine canyon is located the other an lgm channel directed in towards the head of wright canyon the subsequent input of sediment causing this canyon to breach furthest into the shelf than any other canyon in the area offshore of lake st lucia the most proximal portions of the associated leven canyon occupy the mid shelf and are underlain by lake st lucia palaeo drainage channels of lgm age where erosion along the initial lgm palaeo channel has occurred freshwater exchange between the shelf and the fringing lake system has resulted in the development of sinuous features of leven canyon which have eroded in a downslope fluvial like manner thus occupying palaeo drainage lows as erosive flows were entrained models proposed here indicate that 1 the limited accommodation space offered by a narrow continental shelf may allow for a greater preservation potential of wave dominated estuarine facies 2 the seismic expression of these fills may vary yet still satisfy similar sedimentological conditions and 3 antecedent valley topography increases the preservation potential of these valley fills by providing a preferred space in which to re incise and then fill during sea level rise

stratigraphy petrography and correlation of late cenozoic middle atlantic coastal plain deposits implications for late stage passive margin geologic evolution regional chronostratigraphic correlation of middle atlantic upper coastal plain and fall zone fluvial deposits long thought to represent the updip proximal facies of a well dated post oligocene marine sequence in the salisbury embayment remains incomplete in part because of the paucity of biostratigraphic data petrography based lithostratigraphic correlations provide an opportunity to extend age control present in downdip marine deposits updip to fluvial deposits thus establishing the means for a regional chronostratigraphic correlation previous stratigraphic studies in new jersey delmarva southern maryland virginia and the central appalachian piedmont are linked by a crucial sequence of fluvial deposits at the head of chesapeake bay here petrography based lithostratigraphic correlations demonstrate 1 late oligocene late miocene susquehanna river dominated polygenetic quartzose fluvial aggradation bryn mawr formation 2 pliocene heterolithic but quartz dominated fluvial terrace and alluvial fan deposition perryville formation 3 pliocene early pleistocene paleo delaware hudson river dominated lithic and feldspathic rich fluvial aggradation pensauken formation and 4 the initiation of estuarine conditions turkey point beds by early pleistocene time these results are synthesized to propose a new late cenozoic regional chronostratigraphic correlation and depositional history for the salisbury embayment the correlation elucidates a complex interaction between passive margin isostasy tectonics eustasy and sediment source

non energy minerals and surficial geology of the continental margin of maryland abstract the surficial sediments have been mapped and the shallow geologic framework outlined of the maryland inner continental shelf the initial study encompassed a small area offshore of assateague island but was extended northward to include the ocean city area and eastward across several linear shoals the surficial sediments are predominantly sand with mean grain sizes ranging from 0 40 to 2 89 mud and gravel are the mappable components of the surficial sediments muds are distributed along a n s trending band seaward of the shoreface gravels are mapped farther offshore in 18 22 m of water four distinct seismic units are identified from seismic reflection profiles the lowermost unit t1 exhibits high angle clinoforms truncated at the top by a locally prominent near horizontal reflector above this reflector are concordant strata with parallel to subparallel bedding designated as q2 incised into q2 is an extensive channel q3 that trends both coast parallel and coast normal the upper unit q4 overlaps portions of units q2 and q3 along the eastward edges of the study area and is represented in the nearshore by holocene inlet channeling adjacent to the shoreface note that this excludes the modern shelf and sheet

small rivers contribution to the quaternary evolution of a mediterranean littoral system the western gulf of lion france abstract along the mediterranean coasts and the atlantic french coast former and actual research programs focused on major river systems estuaries and deltas characterized by a last glacial relative sea level lowstand and incision and a well developed sedimentary incised valley infilling deposited during the following sea level rise and highstand this paper presents the preliminary results of a program focused on a particular area of the gulf of lion coast with a thin sedimentary cover over the substratum and only minor rivers with non apparent and important sedimentary contribution during the late quaternary the results show that in this area the best pliocene to actual sedimentary record is preserved the paper rests on the analysis of an extensive database of recent high resolution and very high resolution seismic reflection lines and previously published core data seismic data show that a major complex of paleovalleys connected with the orb aude and agly rivers is preserved on the inner shelf and adjacent coastal plain on the inner shelf the separated incised valleys merged in a unique broad and shoreparallel incision dipping southward at the southward extremity the incision turns eastward and seaward the basal surface of this incision extends seawards under six to seven late quaternary depositional sequences preserved on the mid and outer shelf the infilling of the complex of paleovalleys is characterized by aggrading deposits attributed to periods of relative sea level rise transgressive systems tracts organized into several subunits bounded by internal discontinuities locally deeply incising the discontinuities are amalgamated surfaces including successive sequence boundaries indicative of phases of relative sea level falls merged with transgressive surfaces indistinct tidal and wave ravinement surfaces the subunits are the part of late quaternary depositional sequences preserved in estuarine environments they are the lateral equivalents of landward fluvial terraces and seaward coastal and prodeltaic deposits on the shelf using borehole dataset the underlying and eroded deposits below the basal unconformity are correlated with pliocene deposits outcropping landward in the hinterland the top of the incised valleys complex is capped by the last glacial lowstand surface of erosion 18 ky b p reworked by the postglacial transgressive surface ts dissociated near the shoreline into a tidal and a wave ravinement surfaces above the ts the very high resolution vhr seismic data in the lagoons the tidal channels and cores reveal in details the stratigraphic architecture of the deposits at the base a small wedge constitutes the postglacial transgressive systems tract tst locally thinning in the areas distant of the sediment point sources the tst is capped by a flat surface of wave reworking maximum flooding surface or mfs prolongating under the leucate lagoon and merging offshore at the seafloor boreholes and vhr seismic lines trough the coastal barrier and in the lagoon show that the shoreline probably migrated far landward at the end of the transgression when the rate of sea level rise decreased strongly the shoreline migrated seaward and prograding and aggrading sandy material with landward muddy lateral equivalent facies deposited early highstand systems tract hst above the mfs offshore fine material deposited as a sigmoidal blanket of mud originating in part from the north east and rhone river under oceanic circulation equivalent to a subaqueous prodelta subsequently the modern beach barrier built up by wave reworking of the early hst this new study of the western part of the gulf of lion inner shelf and littoral illustrates an incised valley complex and thus presents the best preserved example of the sedimentary record of the effects of the relative sea level changes during the pliocene to actual period for the first time the land to sea transition is preserved and the late quaternary depositional sequences are in a great part observed the last post glacial deposits present a simplified but very different organisation compared to a record front of the adjacent rhone river consequently a synthesis is now possible

migration of the pee dee river system inferred from ancestral paleochannels underlying the south carolina grand strand and long bay inner shelf several generations of the ancestral pee dee river system have been mapped beneath the south carolina grand strand coastline and adjacent long bay inner shelf deep boreholes onshore and high resolution seismic reflection data offshore allow for reconstruction of these paleochannels which formed during glacial lowstands when the pee dee river system incised subaerially exposed coastal plain and continental shelf strata paleochannel groups representing different generations of the system decrease in age to the southwest where the modern pee dee river merges with several coastal plain tributaries at winyah bay the southern terminus of long bay positions of the successive generational groups record a regional southwestward migration of the river system that may have initiated during the late pliocene the migration was primarily driven by barrier island deposition resulting from the interaction of fluvial and shoreline processes during eustatic highstands structurally driven subsurface paleotopography associated with the mid carolina platform high has also indirectly assisted in forcing this migration these results provide a better understanding of the evolution of the region and help explain the lack of mobile sediment on the long bay inner shelf migration of the river system caused a profound change in sediment supply during the late pleistocene the abundant fluvial source that once fed sand rich barrier islands was cut off and replaced with a limited source supplied by erosion and reworking of former coastal deposits exposed at the shore and on the inner shelf

seismic stratigraphy and coastal drainage patterns in the quaternary section of the southern delmarva peninsula virginia usa abstract seismic stratigraphic analysis of the coastal zone and inner shelf of virginia s southern delmarva peninsula has revealed three geochronologically significant surfaces of post tertiary age that impose a relative chronostratigraphic framework on quaternary marine transgressive and regressive events characteristics of these surfaces indicate that two are sequence boundaries and one is a ravinement surface lying at depths of 18 70 m msl datum the lpb surface a late pleistocene basal unconformity represents the sequence boundary separating the tertiary chesapeake group from the overlying late pleistocene nassawadox formation high relief approximately 50 m on the lpb surface is associated with large fluvial channels higher in the stratigraphic section the lpr surface is found at depths of 6 28 m and corresponds to a late pleistocene transgressive or ravinement surface the surface dips southeastward with a regional dip of 0 04 and has local relief of less than 2 m the lpr surface may represent a ravinement which extended to the west side of the chesapeake bay prior to the development of the nassawadox barrier spit however the lpr surface may steepen between the axis of the southern delmarva peninsula and the holocene lagoon to form a shoreface attached to one of several known late pleistocene shorelines lying at depths of 0 20 m the hb surface is a basal unconformity that marks the holocene sequence boundary it deepens seaward with maximum local relief of about 15 m and has a topographic expression very similar to the present day lagoonal drainage pattern maximum thicknesses of holocene and pleistocene sediments 12 and 70 m respectively are found above channels on the hb and lpb surfaces the pleistocene channels are large and limited in number and represent high order channels of a drainage system that drained the piedmont and coastal plain the greater density of low order stream channels on the hb surface suggests a relationship to much smaller drainage basins that were confined to the seaward part of the coastal plain east of the delmarva peninsula these late wisconsinan smaller hb channels do not re occupy the former drain paths of the much larger high order lpb channels

pleistocene macrotidal tide dominated estuary delta succession along the dong nai river southern vietnam abstract this paper focuses on the facies and sequence stratigraphic interpretation of a tide dominated incised valley system that is rare among geological records of the world for its completeness the subject is the middle upper pleistocene ba mieu and thu duc formations exposed along the dong nai river southern vietnam both the ba mieu and the thu duc formations are interpreted as a transgressive tide dominated estuary succession overlain by a highstand tide dominated delta succession the tide dominated estuary succession is generalized as follows in ascending order fluvial facies in landward portions tidal flat upward coarsening and thickening succession of marine sands with a tidal ravinement surface trs created by tidal scouring during transgression at the base and subtidal lag in seaward portions this tide dominated estuary is distinguished from wave dominated and wave and tide dominated estuaries by 1 the lack of a central basin lagoon tidal delta or bayhead delta facies 2 the widespread presence of marine sands 3 the presence of a subtidal lag and 4 the presence of an upper flow regime sand flat facies the tide dominated delta succession is generalized as follows in ascending order upward convex unit of marine sand and onlapping tidal flat deposits a thick upward fining succession of tidal flat salt marsh deposits and coarse fluvial deposits this delta is distinguished from an estuary as follows 1 it shows thick regional upward fining successions indicating shallowing whereas upward coarsening successions indicating deepening are recognized in an estuary a maximum flooding surface mxfs is recognized in the coarsest part of the succession in marine sand and tidal flat deposits 2 fluvial processes dominate the sediment supply in contrast to an estuary in which a thick marine sand body fed from marine sources is dominant 3 ebb tidal currents are dominant whereas flood tidal currents are dominant in an estuary key features of the incised valley system are 1 amplification of the incised valley geometry by tidal ravinement erosion 2 development of tidal channels filled with mud clasts in the estuary 3 a thick marine sand body in the estuary and 4 upward convex unit of marine sand and a thick tidal flat fluvial succession in the delta the ba mieu formation is recognized as depositional sequence sq 1 between sequence boundary sb 1 below and sb2 above sq1 consists of transgressive systems tract tst 1 and highstand systems tract hst 1 sq1 was formed by a transgression regression cycle during marine isotope stage mis 7 sb2 was formed by fluvial incision during the mis 6 lowstand and is amalgamated with the trs of mis 5 the thu duc formation is recognized as sq2 between sb2 below and sb3 above and it consists of tst2 and hst2 sq2 was formed by a major transgression regression cycle on which a lower rank cyclicity was superposed during mis 5 tst2 thins seaward as a result of tidal ravinement erosion the landward extent of marine environment in mis 5 is inferred to have been of greater scale than that in mis 7 from the distribution of the facies and the trs

hyaloclastites and the slope stability of hawaiian volcanoes insights from the hawaiian scientific drilling project s 3 km drill core abstract core samples recovered during the hawaiian scientific drilling project hsdp drilling project reveal that the upper 1 km of the submarine flank of mauna kea is comprised mainly of hyaloclastites progressive very low temperature alteration of these hyaloclastites has been accompanied by systematic transformations in physical properties of these deposits hyaloclastite deposits which directly underlie ca 1 km of subaerially emplaced lavas are very poorly consolidated but over a depth interval of ca 500 m compaction and especially precipitation of zeolitic pore filling cements associated with palagonitization of sideromelane have eliminated porosity as well as promoted the consolidation of these hyaloclastites the latter is reflected in unconfined compressive strengths which increase from mean values respectively of 2 5 and 4 6 mpa in weakly consolidated smectite rich hyaloclastites from the incipient 1080 to 1335 mbsl and smectitic 1405 1573 mbsl alteration zones to a mean value of 10 0 mpa in the more highly consolidated hyaloclastites of the palagonitic zone of alteration from 1573 mbsl to the bottom of the drill hole conversely overlying intercalated and underlying lava flows are generally much less altered and have mean compressive strengths which are 1 to 2 orders of magnitude greater then hyaloclastites at equivalent depths the shear strengths of the hyaloclastites also increase with depth and grade of alteration but are uniformly and substantially lower in the lavas those hyaloclastites exhibiting the highest grade of alteration i e palagonitic also exhibit the highest measured strengths and thus the alteration of hyaloclastites appears to strengthen as opposed to weaken the flanks of the edifice however the contrast in strength between hyaloclastites and lavas may be a primary factor in localizing destabilization and the zones of weak and poorly consolidated hyaloclastites may facilitate slumping by servings as hosts for shallow detachment surfaces on the unsupported flanks of these volcanoes

quaternary facies assemblages and their bounding surfaces chesapeake bay mouth an approach to mesoscale stratigraphic analysis abstract shallow marine facies assemblages in the late quaternary section of virginia s eastern shore peninsula shed new light on the relationship between mesoscale stratigraphic units facies assemblages or depositional systems and the bounding surfaces from which they have been formed these units were deposited by the coast parallel progradation of the pleistocene barrier spit eastern shore peninsula during successive highstands as a consequence each segment of the spit complex has been produced by the coast parallel translation of a relatively small growth area at the spit tip the distal end of the present holocene barrier system appears to closely resemble the pleistocene highstand growth area and this environment consequently serves as a partial analog for interpreting the depositional environment of the fossil highstand deposits the many facies patterns present in the spit complex can be reduced to four kinds of facies assemblages depositional systems adopting a process based model facies template in this scheme definitions of both facies and facies assemblage are more limited than is the case in most textbook definitions in that the facies of a given assemblage are systematically related to each other by grain size and stratal pattern and also related to a bounding surface source diastem which is the immediate source of sediment for the facies assemblage vertical transitions between individual facies are easily identified in outcrop but the horizontal gradients of facies change are too gentle to be observed over the short dimensions of the borrow pits and do not have sufficient acoustic contrast to appear on ground penetrating radar records however the facies assemblages both in the borrow pits and on radar records stand out by virtue of their sharply defined bounding surfaces source diastems the facies assemblage either buries its source diastem or is capped by it the assemblages in the spit complex are in ascending stratigraphic order 1 several tidal shoal assemblages each underlain by a channel base diastem 2 two shoreface assemblages separated by an intervening marginal shoal assemblage and its underlying channel base diastem and 3 a beach strandplain assemblage underlain by a surf diastem all of these systems prograded southward as the nose of the spit prograded and while they did so zones of erosion cut the bounding surfaces that separate them two important bounding surfaces are conjugate surfaces that nourished both the facies assemblage above and the assemblage beneath as each surface advanced erosion at their leading edge spilled sediment forward down the nose of the spit while sediment was also swept backward aiding in the burial of the surface a conjugate surface creates a sandwich structure in which two facies assemblages are separated by the generating surface proximal facies are back to back across these sediment spreading boundaries episodic progradation of the spit tip by development of successive recurved beach ridges has overprinted the horizontal first order reflectors separating facies assemblages with gently dipping second order reflectors that separate successive growth increments of the spit although less clearly defined these growth increments are essentially high frequency autocyclic sequences and constitute the next higher scale of spatial organization above the depositional systems scale the manner in which facies have been organized into depositional systems in the late pleistocene highstand deposits of the eastern shore is specific to this estuary mouth setting these assemblages are however local expressions of a facies template that can be generalized to many other settings

transgressive systems tract development and incised valley fills within a quaternary estuary shelf system virginia inner shelf usa abstract high frequency quaternary glacioeustasy resulted in the incision of six moderate to high relief fluvial erosion surfaces beneath the virginia inner shelf and coastal zone along the updip edges of the atlantic continental margin fluvial valleys up to 5 km wide with up to 37 m of relief and thalweg depths of up to 72 m below modern mean sea level cut through underlying pleistocene and mio pliocene strata in response to drops in baselevel on the order of 100 m fluvially incised valleys were significantly modified during subsequent marine transgressions as fluvial drainage basins evolved into estuarine embayments ancestral generations of the chesapeake bay complex incised valley fill successions are bounded by or contain up to four stacked erosional surfaces basal fluvial erosion surface bay ravinement tidal ravinement and ebb flood channel base diastem in vertical succession these surfaces combined with the transgressive oceanic ravinement that generally caps incised valley fills control the lateral and vertical development of intervening seismic facies depositional systems transgressive stratigraphy characterizes the quaternary section beneath the virginia inner shelf where six depositional sequences sequences i vi are identified depositional sequences consist primarily of estuarine depositional systems subjacent to the transgressive oceanic ravinement and shoreface shelf depositional systems highstand systems tract coastal systems are thinly developed the quaternary section can be broadly subdivided into two parts the upper part contains sequences consisting predominantly of inner shelf facies whereas sequences in the lower part of the section consist predominantly of estuarine facies three styles of sequence preservation are identified style 1 represented by sequences vi and v is characterized by large estuarine systems ancestral generations of the chesapeake bay that are up to 40 m thick have hemicylindrical wedge geometries and occur within large coast oblique trending depressions paleo estuaries style 1 is dominated by fluvial through estuary mouth depositional systems seismic facies 1 4 style 2 sequence preservation represented by sequences iii and ii is dominantly an inner shelf and shoreface succession with a seaward thickening tabular wedge geometry that does not exceed 15 m in thickness these shoreface and inner shelf depositional systems of the upper transgressive systems tract seismic facies 9 and highstand systems tract seismic facies 7 and 11 are not associated with paleo estuaries style 3 sequence preservation is represented by sequence i the holocene sequence it consists of lower transgressive systems tract fluvial estuarine lagoonal and tidal inlet fill deposits seismic facies 1 6 and 8 overlain by upper transgressive systems tract shelf and shoreface sands seismic facies 9 style 3 has a crenulated wedge geometry and is thickest beneath and seaward of the modern chesapeake bay mouth it thins northward and landward onto late pleistocene interfluvial highs on the basinward side of the southern delmarva peninsula

late quaternary sedimentation off new jersey new results using 3 d seismic profiles and cores abstract regional seismic reflection surveys have delineated a wedge of late quaternary sediment extending 150 km south from the hudson apron along the edge of the continental shelf off new jersey the bottom of the sediment wedge is defined by a prominent reflector r assumed to represent an erosional surface carved during a low stand of sea level probably corresponding to the wisconsinan maximum glaciation a 3 d reflection survey of a 5 0 5 km area of the southern part of the wedge was carried out in october 1989 line spacing was 10 m and shot spacing 2 5 m navigation achieved position accuracies to the survey shows that the outer shelf sediment wedge has a complex internal structure unrelated to the present seafloor morphology the sedimentary sequence appears to have been formed by a series of depositional events related to glacial melting and interrupted by at least one erosional episode marked by a seismic surface that defines a system of meandering channels faunal studies of samples from cores indicate that the sediments were deposited at shallower depths than at present but there is no evidence for deposition in shallower water or closer proximity to land than the modern mid shelf it appears that the history of periglacial marine sedimentation which accompanied the post wisconsinan deglaciation is no less complex than its continental counterpart

ancient channels of the susquehanna river beneath chesapeake bay and the delmarva peninsula three generations of the ancestral susquehanna river system have been mapped beneath chesapeake bay and the southern delmarva peninsula closely spaced seismic reflection profiles in the bay and boreholes in the bay and on the southern delmarva peninsula allow detailed reconstruction of each paleochannel system the channel systems were formed during glacial low sea level stands and each contains a channel fill sequence that records the subsequent transgression the trunk channels of each system are 2 to 4 km wide and are incised 30 to 50 m into underlying strata they have irregular longitudinal profiles and very low gradients within the chesapeake bay area the three main stem channels diverge from the head of the bay toward the southeast the channels are rarely coincident although they commonly intersect all three main channels pass beneath the southern delmarva peninsula forming an age progression from north oldest to south youngest beneath the peninsula and from east oldest to west youngest beneath chesapeake bay southward progradation of the tip of the delmarva peninsula during interglacial high sea level stands caused southward migration of the mouth of the bay so that the next generation of channels were incised progressively further towards the southwest the youngest paleochannel is clearly of late wisconsinan age about 18 ka and the intermediate one appears to be late illinoian in age or about 150 ka the age of the oldest paleochannel is not well constrained but it is in the range of about 200 to 400 ka the three paleochannel systems imply a dynamic coastal plain environment and at least two previous generations of the chesapeake bay both the chesapeake bay and the southern delmarva peninsula have changed considerably in the past half million years

quaternary stratigraphic evolution of the southern delmarva peninsula coastal zone cape charles virginia the quaternary evolution of the coastal zone along the southern delmarva peninsula of virginia was investigated by means of a high resolution seismic survey and supplemental shallow core borings the seismic stratigraphic framework of the area is composed of three depositional sequences separated by two prominent unconformities in ascending order the three seismic sequences represent a late tertiary substrate pleistocene deposits of post illinoian age and holocene deposits stratigraphic analysis indicates that the evolutionary development of the area was controlled mainly by glacio eustatism and paleotopographic features the late tertiary substrate was dissected by southeasterly flowing streams of the ancestral susquehanna fluvial system resulting in a highly furrowed surface consisting of valleys and interfluves that exhibit as much as 46 m of local relief the erosional surface probably represents a mature multicyclic landscape of pre sangamonian age the unconformably overlying pleistocene deposits attain a maximum thickness of 41 m pleistocene sedimentation was closely controlled by the paleotopography with relatively thicker deposits accumulating within ancestral valleys in contrast thinner deposits accumulated over the ancestral interfluves which did not become active sites of sedimentation until after the topographic relief had been substantially subdued by valley infilling pleistocene deposits are characterized by complex fades relationships multiple generations of fluvial channeling and the presence of a variety of coastal geomorphic features fluvial channel zones largely overlie the thalwegs of major southeasterly trending ancestral valleys indicating a paleotopographic control of pleistocene drainage routes the youngest pleistocene geomorphic feature which constitutes a distinctive sand lithosome is a coastal barrier ridge that appears to have developed during a sangamonian interglacial or mid wisconsinan interstadial high stand of sea level during the late wisconsin regression pleistocene deposits were eroded resulting in the development of a relatively low gradient subdued landscape compared to the highly furrowed pre sangamonian landscape holocene deposits unconformably overlie the pleistocene sequence and attain a maximum thickness of 19 m sedimentation during the holocene transgression was primarily influenced by late wisconsinan paleotopography with relatively thicker deposits accumulating within paleochannels and along the modern shoreface holocene deposits also exhibit complex facies relationships extensive channeling and coastal geomorphic features the holocene sediments consist of two distinct lithosomes that are representative of modern barrier island and lagoon marginal lagoon subenvironments microfossil assemblages indicate paleosalinities ranging from upper estuarine to marginal marine inlet conditions vertical environmental transitions during the late holocene transgression reflect a progressive restriction of the southern delmarva coastal area by barrier island development with subsequent lagoonal infilling the modern barrier islands are retrograding and lagoonal infilling has progressed to varying degrees having been influenced by both back barrier sedimentation rates and pre holocene topography

calculating shoreline erosion potential using nearshore stratigraphy and sediment volume outer banks north carolina 1 despite the acknowledged influence of coastal geological framework on the behavior of beaches and barrier islands and a wealth of geological and bathymetric observations from the inner shelf quantitatively connecting those observations to shoreline behavior has been difficult nearshore geologic and morphologic variability described by recent research is not well represented by conventional geologic parameters such as mean grain size and shoreface slope used in most shoreline change models we propose that total nearshore sediment volume as calculated to a continuous seismic reflection surface provides a flexible and robust metric for use in the prediction of shoreline change this method of determining the volume of sediment in the nearshore accounts for three dimensional sandbar morphologies and heterogeneous seafloor sediments the decadal scale shoreline change rate for northeastern north carolina is significantly correlated to the volume of sediment in the nearshore when a geologically defined base is used in volume determinations suggesting that the shallow stratigraphic framework of transgressive coasts is an important influence on decadal shoreline behavior nearshore sediment volume was overestimated when an arbitrary depth constant baseline was used and was not correlated to decadal shoreline change this implies that a volume metric which accounts for both framework geology and variable seafloor morphology better represents the geologic character of the shoreface and may help to improve existing models of shoreline change an empirical model of regional shoreline erosion potential demonstrates the importance of incorporating nearshore sediment volume shallow framework geology and surface morphology when predicting seasonal to decadal shoreline evolution

clastic sequences developed during late quaternary glacio eustatic sea level fluctuations on a passive margin example from the inner continental shelf near barnegat inlet new jersey analysis of 100 km of seismic reflection geopulse profiles from a 47 km 2 grid on the new jersey low mesotidal inner continental shelf near barnegat inlet reveals that the upper 30 m is composed of 3 unconformity bounded units vibracores 1 6 m long recovered from 12 sites contain several lithofacies reflecting a variety of depositional environments that existed during late quaternary glacioeustatic sea level fluctuations on this slowly subsiding passive margin with low sediment supply environments include rivers during glacial and stadial lowstands of the sea and a barrier island lagoon complex as well as pro barrier ebb tidal delta shore attached and detached ridges and below storm wave base shelf during interglacial or inter stadial highstands following the last major interglacial 125 ka sea level fell and rivers eroded a planar seaward dipping surface r1 by early wisconsinan time 70 ka as sea level rose during the mid wisconsinan 55 ka a barrier island system migrated to within 0 2 1 7 km of the modern barrier shoreline leaving a 4 to 6 m thick record depositional sequence i maximum highstand of the mid wisconsinan sea level was 20 m below present sea level fell again during the late wisconsinan 20 ka and rivers again flowed across the exposed shelf creating an unconformity r2 a barrier lagoonal system developed under rising sea level by at least early middle holocene time based on peats 8810 170 yr b p cored from 12 m the mid wisconsinan 55 ka barrier system was preserved under these early holocene transgressive sediments lower unit of depositional sequence ii lower transgressive tract the modern barrier and inner continental shelf deposits upper unit of depositional sequence ii upper transgressive tract are relatively thin average 3 4 m pebbly sands overlying a prominent unconformity a transgressive surface r3 formed by marine erosion during the holocene sea level rise both the ebb tidal delta and shore attached linear sand ridges act as partial shields to wave and tidal current erosion of the muddy sub strate below r3 in the nearshore area this shielding is creating a transgressive surface marine unconformity of relatively high relief 3 7 m

detailed architecture of a compound incised valley system and correlation with forced regressive wedges example of late quaternary tet and agly rivers western gulf of lions mediterranean sea france abstract quaternary incised valley systems are usually characterized by the preservation of a single valley fill attributed to the last post glacial period moreover there are very few cases of correlation between incised valley system developed on inner shelf and sedimentary units observed on the mid to outer shelf mainly forced regressive wedges the roussillon shelf in the western part of the gulf of lion is a particular example of preserved quaternary compound incised valley system also characterized by a direct correlation with the forced regressive lowstand wedges on the mid outer shelf high resolution seismic data and a borehole 60 m deep located on the beach barrier permit an accurate study of the geometry and lithology of the system six imbricated and more or less preserved incised valleys and valley fills are observed up to the inner to mid shelf the key surfaces associated to the incised valleys are correlated to the boundaries of the forced regressive wedges they are assumed to be reworked surfaces at the borehole location only few thin layers less than 1 m thick of coarse grain and or floating pebbles are observed and should correspond to preserved fluvial lowstand deposits reworked under marine influence the valley fills are mainly composed of estuarine muddy silts from ams 14c age dating it is inferred that the uppermost incised valley system is younger than 45 ky cal bp based on those observations the six preserved incised valley systems are assumed to be controlled by the last six 4th order sea level cycles 100 ky of the middle to late quaternary the paleo topography of the underlying plio quaternary deposits controls the compound incised valley system location the deep topography of the messinian erosionnal surface is a controlling factor at a lower degree the partial preservation of the successive valley fill is attributed not only to the differential subsidence but also to the lateral migration of each incision and to the hydrodynamic regime

submerged barrier shoreline sequences on a high energy steep and narrow shelf abstract late pleistocene holocene shoreline sequences and associated shelf stratigraphy are described from a high gradient high wave energy shelf although shoreline preservation by overstepping is considered unlikely in such an environment as a result of intense ravinement during shoreline translation the development and preservation of two distinct shorelines at 100 m and 60 m are evident and attributed to century to millennial scale periods of stillstand during these periods shoreline equilibrium forms developed characterised by early diagenesis of beachrock and aeolianite between these features the shelf is dominated by erosional surfaces reflecting ravinement during periods of slowly rising sea level where shorelines are not preserved areas of scarping in the ravinement surface at similar depths to the adjoining shorelines represent rocky headlands separating the sandy coastal compartments where the depositional shorelines formed shoreline preservation by overstepping was facilitated by rapid relative sea level rise associated with meltwater pulses 1a and 1b although the features preserved are likely to represent only the cemented cores of the coastal dunes and linear beachrock outcrops formed the steep antecedent shelf gradient fostered the erosion of significant portions of the shorelines by ravinement with loose sediment re organised into a thick post ravinement drape the removal of shorelines during ravinement was countered by the rapid rate of sea level rise and early sub tropical diagenesis it is clear that due to the combined effects of subtropical diagenesis long periods of stillstand and drowning by meltwater pulses the governing controls on shoreline preservation can be over ridden by combinations of local climatic and global eustatic factors

mapping the threat of seawater intrusion in a regional coastal aquifer aquitard system in the southeastern united states the upper floridan aquifer ufa beneath the southeastern us atlantic coastal plain and inner continental shelf is a major source of groundwater for coastal georgia ga and south carolina sc where it supplies over 50 of water requirements since pumping from the ufa first began at savannah ga in the late 1800s a large 50 km radius cone of depression has developed on the aquifer s potentiometric surface where a regional miocene age aquitard overlying the ufa is thin or absent within this cone the opportunity exists for seawater to leak downward through the seabed and into the aquifer recently completed marine reflection seismic surveys on the georgia south carolina coast identified 11 areas of concern aocs where the ufa is susceptible to seawater intrusion results from this project and from an aoc test drilling program recently completed are contributing to a large database of information and models being developed for the ufa by several agencies and academic institutions the results will provide input necessary for managing groundwater resources and mitigating potential seawater intrusion on the georgia south carolina coast

uranium series dating of fossil corals from marine sediments of southeastern united states atlantic coastal plain extensive low lying marine deposits border the southeastern united states atlantic coastal plain some units are fossiliferous and contain corals as isolated fragments in sediments of a detrital character these corals are subject to alteration processes such that suites of related samples must be examined to determine the suitability of these coral samples for reliable uranium series dating with the exception of those from one location most samples appear to have remained closed systems with respect to the isotopes of uranium and thorium throughout their geologic history extraneous 230th has been detected in some of the corals due to incorporation of some detrital materials into their skeletons for these samples different methods are applied to correct for the initial 230th contamination continued sampling and analyses have resulted in 55 individual uranium thorium determinations the average 230th ages of samples from the norfolk formation and from later and earlier deposited sediments of the wando formation are 71 000 87 000 and 129 000 yr and they appear to correlate with oxygen isotope substages 5a 5c and 5e respectively the average 230th age of samples from beds of the rappahannock river ponzer and ten mile hill localities is 212 000 yr and they correlate with oxygen isotope stage 7 the sediment of the canepatch formation is 460 000 yr old and it is tentatively correlated with oxygen isotope stage 11 there is general agreement between uranium series and uranium trend dates and between the quantitative trends of the amino acid data and uranium series dates the amino acid values however ure unacceptably high in at least two groups of samples those from localities near charleston south carolina and from central virginia

delta development and channel incision during marine isotope stages 3 and 2 in the western south yellow sea abstract approximately 4100 km of high resolution seismic profiles recently obtained from the western south yellow sea were subdivided into seven seismic units by six major seismic surfaces three sediment cores between 60 and 71 m in length obtained from localities on the seismic profile lines were analyzed for sedimentary characteristics clay mineral components and benthic foraminiferal and ostracod assemblages and were also dated by ams 14 c and optically stimulated luminescence to document the environmental history of the region stratigraphic units in the cores were confidently correlated with seismic units in the profiles stratigraphic correlation among these three cores and the previous well studied core qc 2 was facilitated by the cold water deposits in marine isotope stage mis 5 the three cores document the sedimentary sequence during the period from mis 6 up to mis 1 strata formation and sedimentary environment changes since mis 5 are strongly controlled by sea level fluctuations most of the successions were formed in mis 5 mis 3 and mis 1 with major erosions in mis 4 and mis 2 particularly our data revealed the presence of a large delta active during mis 3 likely from the early stage of mis 3 to about 40 cal kyr bp that was subsequently affected by channel incision the delta succession and incised channel fills have a high concentration of smectite in their clay mineral components suggesting that the paleo yellow river was the main contributor to the delta development and channel incision the delta sequence has a coarsening upward trend and consists of two seismic facies the upper facies shows lateral alternations of chaotic and oblique or very low angle reflectors which correspond to sandy proximal delta front and delta plain facies and the lower facies is characterized by seaward dipping clinoforms which correspond to muddy distal delta front and prodelta facies the top surface of the delta inclines very gently seaward consistent with a deltaic development associated with the sea level fall in mis 3 the incised channel system consists of two main channels with multiple tributaries in a dendritic pattern the incised channel fills begin with fluvial and then estuarine sediments which are truncated by a transgressive ravinement surface and capped by transgressive deposits the main incision channels have a terraced cross sectional morphology which is interpreted to reflect multiple episodes of sea level fall during incision presumably from the late mis 3 to the last glacial maximum

controls on the stratigraphic framework and paleoenvironmental change within a holocene estuarine system pamlico sound north carolina usa abstract this study examines the holocene stratigraphic record and paleoenvironmental evolution of a large estuarine system at high temporal and spatial resolution in the context of changing climate sea level and hydrodynamics new data are used to examine two time periods of increased marine influence within pamlico sound in northeastern north carolina interpreted to be the result of extensive barrier island segmentation synchronous with periods of rapid climate change during the late holocene the study reveals the controls on the stratigraphic development and the highly dynamic character of the coastal system in response to climate and sea level change as it interacts with paleotopography these findings can be used to inform projections of future environmental changes estuarine waters occupied paleovalleys in the pamlico sound region as early as ca 7500 cal bp and pleistocene interfluves separated the paleovalleys from the atlantic ocean until ca 5500 cal bp when they were flooded by rising sealevel forming the broad shallow pamlico sound initial barrier islands and shoals likely formed sometime between 5500 and 5000 cal bp providing the geomorphic setting for continued estuarine conditions behind the barriers at ca 4000 cal bp an increase in marine influence and sand content is detected in multiple cores and is correlated to seismic data within the pamlico sound basin this change is interpreted to be the result of increased segmentation of barrier islands thus a greater number of inlets or wider inlets which is consistent with a rapid transgression seen in other areas of the u s east coast the segmentation may have been partially facilitated by a rapid increase in lagoonal area and tidal prism by overtopping of interfluves greater barrier island continuity is evident from 3500 to 1200 cal bp as indicated by muddy deposits with low brackish estuarine foraminiferal assemblages at ca 1200 cal bp seismic sedimentological and micropaleontological data suggest an increase in wave and current energy and marine influence throughout southeastern pamlico sound these changes are interpreted to represent extensive segmentation of the barrier islands during the medieval climate anomaly mca since ca 500 cal bp the pamlico sound system has returned to a more restricted state as inlets have closed currently only three major inlets segment the outer banks the barrier island system fronting pamlico sound but warming climate and increasing rates of sea level rise suggest that another episode of barrier island segmentation began about a half century ago and appears that it may extend into the near future

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

incised channel morphology and depositional fill of the paleo seomjin river in the continental shelf of the south sea korea this study is the first attempt at describing and interpreting incised channels on the continental shelf of the south sea korea the distribution pattern shape and infilling of submerged channels incised across the continental shelf of the south sea have been investigated based on approximately 1940 line km of chirp and sparker data the incised channel system of the paleo seomjin river on the continental shelf is approximately 109 km long 800 5000 m wide and is more than 890 km2 in area meandering and straight types of channel are dominant on the inner shelf with a change to straight and braided planforms on the mid to outer shelf sparker seismic data suggest the paleo channels formed under fluvial systems when the shelf was exposed during the last glacial maximum lgm channel fills are divided into five types based on erosional surfaces and internal seismic reflectors i transparent to semi transparent incised channel fill ii parallel to sub parallel incised channel fill iii complex incised channel fill iv divergent incised channel fill and v chaotic incised channel fill the acoustically transparent facies of the channel fill type type i suggest the presence of basin muddy deposits in a low energy environment which were dominant in the inner shelf these muddy sediments were likely during a period of higher sea level during the holocene transgression types ii iii and iv are characterized by onlap downlap and wave or tidal ravinement surfaces respectively indicating that they were deposited during a transgressive stage which type v represent basal incision surface the evolution of paleo seomjin river has been strongly controlled by sea level change and sediment transport processes since the lgm

late quaternary activity of the scorciabuoi fault southern italy as inferred from morphotectonic investigations and numerical modeling 1 following a detailed morphotectonic analysis of the fluvial terraces of the sauro river basilicata southern italy the present research documents for the first time the late quaternary tectonic activity of the scorciabuoi fault and discusses its inferred seismogenic potential on the basis of both remote sensing techniques and detailed field investigations four fill terraces have been recognized and mapped along the sauro valley showing differential cumulative displacements across the fault these terraces are genetically correlated with four highstand sea level periods following stratigraphic and geological age constraints and on the basis of the correlation with a sequence of marine and fluvial terraces characterizing the lower agri valley the sauro terraces likely formed between 80 or 100 ka and present the inferred long term slip rate of the scorciabuoi fault ranges between 0 5 and 1 0 mm a numerical simulations based on a crustal elastic deformation model also contribute to separate and tentatively quantify the regional uplift rate 1 0 1 4 mm a and to improve the overall reconstruction of the late quaternary evolution of the area the synergic but distinct roles played by eustatism regional uplift and faulting are eventually appreciated

coastal lithosome preservation evidence from the shoreface and inner continental shelf off bogue banks north carolina abstract seismic and vibracore data from the continental shelf as well as borehole data from an adjacent barrier island indicate that the migrating shoreface responding to rising sea level has nearly completely removed the entire coastal sedimentary record in northern onslow bay north carolina this process was active throughout the quaternary and even the late tertiary as middle tertiary sediments and rocks directly crop out on the sea floor in vast areas of this shelf sector seaward of bogue banks a holocene barrier island located along northern onslow bay seismic sequences have been truncated by the modern shoreface which extends to about 12 m depth correlations with borehole data on the island indicate that these sequences are pleistocene and holocene in age the holocene sequences contain numerous channels which are interpreted to be relict tidal inlets however none extends vertically lower than the shoreface indicating that landward translation of the shoreface would remove most of even the deepest holocene coastal lithosomes parts of the pleistocene and even a portion of the tertiary the middle and inner portions of the continental shelf have been incised by numerous channels channel facies are an important component of shelf sedimentary and stratigraphic sequences and comprise about one third of northern onslow bay similar seismic infilling facies and vibracore data as well as the poor preservation potential of the tidal inlet throats indicate that the channels were lower coastal plain streams the infilling sediments are mostly muds with some sands and shells dates from shells via the amino acid racemization technique are pleistocene in age these channels with some having multiple infilling events assume greater importance when one recognizes that essentially they alone hold the vast majority of the quaternary record of numerous sea level fluctuations

late quaternary stratigraphy and sea level history of the northern delaware bay margin southern new jersey usa a ground penetrating radar analysis of composite quaternary coastal terraces abstract ground penetrating radar gpr and lithologic data reveal six pleistocene sea level highstand sequences forming two composite terraces along the northern margin of delaware bay in southern new jersey usa the upper terrace 18 to 9 m msl is underlain by four estuarine marine sequences of middle pleistocene age while the lower terrace 6 m msl contains 2 middle to late pleistocene sequences separating the 2 terraces is a variably sloping escarpment cedarville created by erosion during at least 2 high sea level events intensive radar imaging and boring of these 6 unconformity bounded units allows for their interpretation in a sequence stratigraphic context identifying transgressive highstand and regressive phases higher than present sea levels of 14 12 6 and 16 m during the middle pleistocene and 5 m during the middle and or late pleistocene are indicated by these sedimentary sequences suggesting relative stability of this section of the atlantic coastal plain during the past 500 ka gpr analysis of coastal drainage modification reveals a contrasting lowstand sequence of incised paleovalleys supporting the interpretation that these bay margin deposits contain one of the most complete sections of late quaternary highstand stratigraphy in the mid atlantic region for appendix see http www elsevier nl locate quascirev

quaternary depositional patterns and sea level fluctuations northeastern north carolina abstract a detailed record of late quaternary sea level oscillations is preserved within the upper 45 m of deposits along an eight km transect across croatan sound a drowned tributary of the roanoke albemarle drainage system northeastern north carolina drill hole and seismic data reveal nine relatively complete sequences filling an antecedent valley comprised of discontinuous middle and early pleistocene deposits on interfluves lithologically similar marine deposits of different sequences occur stacked in vertical succession and separated by ravinement surfaces within the paleo drainage marine deposits are separated by fluvial and or estuarine sediments deposited during periods of lowered sea level foraminiferal and molluscan fossil assemblages indicate that marine facies were deposited in a shallow marine embayment with open connection to shelf waters each sequence modifies or truncates portions of the preceding sequence or sequences sequence boundaries are the product of a combination of fluvial estuarine and marine erosional processes stratigraphic and age analyses constrain the ages of sequences to late marine isotope stage mis 6 and younger 140 ka to present indicating multiple sea level oscillations during this interval elevations of highstand deposits associated with late mis 5 and mis 3 imply that sea level was either similar to present during those times or that the region may have been influenced by glacio isostatic uplift and subsidence

the record of major quaternary sea level changes in a large coastal plain estuary chesapeake bay eastern united states abstract seismic reflection surveys of the chesapeake bay combined with geologic mapping and analysis of boreholes on the delmarva peninsula provide evidence of at least three generations of the susquehanna river system and three generations of the chesapeake bay the evidence for ancient courses of the susquehanna river is preserved as three distinct paleochannels and evidence for ancient versions of the chesapeake bay is preserved as three sets of paleochannel fill beneath the bay and three generations of barrier spit deposits on the southern delmarva peninsula the paleochannels represent relative sea level minima and the channel fill and barrier spit deposits represents relative sea level maxima a history of three major marine transgressions is recorded in the stratigraphy preserved in the filled paleochannels and in the overlying barrier spit complexes three systematic progressions from fluvial to estuarine to bay or nearshore marine environments this sea level record seems to be compatible with the saw toothed pattern of the marine oxygen isotope record and with the concept of glacial interglacial terminations it also seems to have a climax character in which most of the preserved evidence is related to the largest terminations and to the extreme sea level positions that bound those terminations the three paleochannel fill and barrier spit complexes appear to correspond to oxygen isotope stages 1 5 and either 7 or 11 the three related paleochannels correspond to stages 2 6 and either 8 or 12

micro scale analysis of tree ring δ18o and δ13c on α cellulose spline reveals high resolution intra annual climate variability and tropical cyclone activity high resolution analysis of stable carbon and oxygen isotopic composition 13c and 18o of tree ring cellulose has been increasingly in demand for the study of climate seasonality droughts and tropical cyclone hurricane activity the peeling grinding method commonly used for tree ring cellulose preparation is both time consuming and labor intensive and often results in cross tracheid sampling that masks high frequency intra annual climate signals and short term climate events here we present a new method by extracting tree ring cellulose directly from wholewood spline that omits the peeling grinding step and allows for micro scale 13c and 18o analysis that facilitates high resolution seasonal climate study this ultrasound assisted non destructive extraction method has significantly increased the output of tree ring cellulose preparation while retaining the wood cell fabric wood cell wall fibers collected from the cellulose spline were directly loaded into pre weighed silver or tin capsules and packed after oven drying for stable oxygen or carbon isotope analysis a 3 045 mm annual ring subdivided over 26 sections for 13c and 18o analysis revealed remarkable intra annual isotopic variations 1 62 for 13c and 5 85 for 18o the intra annual 13c values inversely covary with the seasonal precipitation pattern suggesting moisture regulation on tree ring 13c variations the high resolution 18o analysis unravels tropical cyclone activities hurricanes frances and ivan in 2004 that are characterized by an abrupt decline in 18o values by 2 6 with a v shape pattern in tree ring latewood an algorithm is developed for establishing regional patterns of tree ring seasonal 13c and 18o for the study of the mean state of climate seasonality and its anomalies

quaternary stratigraphy and sea level history of the u s middle atlantic coastal plain abstract middle atlantic inner continental shelf stratigraphic studies document a regional late pleistocene fossiliferous mud deposit from northern new jersey to cape lookout north carolina seismic reconnaissance and detailed stratigraphic analyses reveal the nature of the mud termed unit q2 on the maryland inner continental shelf extensive amino acid relative age determinations from the single genus mulinia combined with additional amino acid analyses from onshore deposits having radiometric dates for calibration indicate an age range for unit q2 corresponding to oxygen isotope stage 5 ostracode assemblages delineate four distinct climatic episodes in unit q2 enabling correlation of the zones in q2 to the deep sea isotopic record of climatic fluctuations substages in stage 5 late stage 5 is represented on the maryland shelf by the 6 meter thick mud of unit q2 deposited in an open shelf environment at slightly depressed sea levels relative to substage 5e late stage 5 sea levels including sea level minima can be estimated for the mid atlantic coastal plain by direct measurement of the altitudes of ostracode zone boundaries offshore and from peak transgressive facies in correlative deposits onshore late stage 5 sea levels determined from the inner shelf and adjacent nearshore facies on the atlantic coast comprise the most complete sea level history for stage 5 yet proposed some recent revisions of glacioeustatic sea level models advocate slightly higher sea levels during late stage 5 substage 5c in particular than originally estimated from uplifting reef tracts and support sea levels higher than estimates from deep sea isotopic records the sea level record from the maryland inner continental shelf confirms these recent estimates in an area of minimal tectonism and adds sea level minima estimates for substages 5d and 5b offshore a more complete record of stage 5 is preserved than in onshore deposits which are limited to peak transgressive facies discrepancies in correlation among emerged coastal plain facies therefore become resolvable within the context provided by the shelf stratigraphy

influence of subsidence on the anatomy of marine siliciclastic sequences and on the distribution of shell and bone beds skeletal concentrations are common foci for palaeontological collecting yet vary widely in their expected levels of taphonomic bias depending on whether they are comparatively simple event concentrations more complex accretionary accumulations of either normal or condensed thickness or residual lags that mark horizons of significant erosional corrosional truncation of the record table 1 these different types and their intermediates also have different potential for use in basin analysis for example as marker beds bathymetric indicators and clues to hiatuses the stratigraphy and taphonomy of marine siliciclastic sequences from a spectrum of basin types have been examined to determine the extent to which shell and bone beds are linked to physical stratigraphic features such as discontinuity surfaces and transgressive regressive cycles at various scales and thus the extent to which physical processes might influence palaeontological data this series of basin scale studies has also provided an opportunity to assess the practical utility of skeletal concentrations in reconstructing basin history and to investigate subsidence related variation both in skeletal accumulation and in the anatomy of siliciclastic sequences field studies have been restricted to post palaeozoic primarily neogene sections in warm temperate to subtropical palaeolatitudes and have focused on marine facies tracts developed in shelf and shallower water depths during phases of coastal onlap sequence stratigraphic terms are used here to describe physical aspects of the record and do not imply any particular chronostratigraphic value or genetic i e eustatic origin the results of this work indicate that a skeletal concentrations are distributed fairly systematically within marine sequences both in

late pleistocene drainage systems beneath delaware bay abstract analyses of an extensive grid of seismic reflection profiles along with previously published sedimentary data and geologic information from surrounding coastal areas outline the ancestral drainage systems of the delaware river beneath lower delaware bay major paleovalleys within these systems have southeast trends relief of 10 35 m widths of 1 8 km and axial depths of 31 57 m below present sea level the oldest drainage system was carved into miocene sands probably during the late illinoian lowstand of sea level it followed a course under the northern half of the bay continued beneath the cape may peninsula and extended onto the present continental shelf this system was buried by a transgressive sequence of fluvial estuarine and shallow marine sediments during sangamonian time at the height of the sangamonian sea level transgression littoral and nearshore processes built the cape may peninsula southward over the northern drainage system and formed a contiguous submarine sedimentary ridge that extended partway across the present entrance to the bay when sea level fell during late wisconsinan time a second drainage system was eroded beneath the southern half of the bay in response to the southerly shift of the bay mouth this system which continued across the shelf was cut into coastal plain deposits of miocene and younger age and included not only the trunk valley of the delaware river but a large tributary valley formed by the convergence of secondary streams that drained the delaware coastal area during the holocene rise of sea level the southern drainage system was covered by a transgressive sequence of fluvial estuarine and paralic deposits that accumulated due to the passage of the estuarine circulation cell and to the landward and upward migration of coastal sedimentary environments some holocene deposits have been scoured subsequently by strong tidal currents the southward migration of the ancestral drainage systems beneath delaware bay is analogous to that found under nearby chesapeake bay in both areas shifts in the bay mouths and river courses have preserved the morphologies and sedimentary fill of former drainage systems and provided a clear record of major sea level fluctuations data from this study demonstrate that important information concerning ancient estuarine environments can be derived from the locations and characteristics of former fluvial systems

compound incised valley characterization by high resolution seismics in a wave dominated setting example of the aude and orb rivers languedoc inner shelf gulf of lion france a branch of a time calibrated late quaternary compound incised valley complex is investigated using high and very high resolution seismic data the incised valley system is confined on the inner shelf and entrenched parallel to the shore in unconsolidated pliocene deposits the infilling of the incised valley system comprises three sigmoidal bodies dipping progressively downstream representing depositional sequences the lowermost sequences are less well preserved at their downstream extremity and the whole system is both aggrading and prograding older pleistocene late quaternary sequences could be preserved under the coastal plain individual sequences are closely similar to the classic model of a microtidal incised valley fill nevertheless the central estuary bay basin muds are seen to interfinger locally with high energy deposits that represent potential reservoirs the properties prograding and aggrading architecture and occurrence of high energy deposits and preservation of these compound incised valley fill deposits are attributed to general glacio eustatic cycles and local atmospheric and oceanic regime and proximity of the hinge line conditions data acquisition strategy is a determining factor to interpret such systems