optically stimulated luminescence age controls on late pleistocene and holocene coastal lithosomes north carolina usa luminescence ages from a variety of coastal features on the north carolina coastal plain provide age control for shoreline formation and relative sea level position during the late pleistocene a series of paleoshoreline ridges dating to marine isotope stage mis 5a and mis 3 have been defined the kitty hawk beach ridges on the modern outer banks yield ages of 3 to 2 ka oxygen isotope data are used to place these deposits in the context of global climate and sea level change the occurrence of mis 5a and mis 3 shorelines suggests that glacio isostatic adjustment gia of the study area is large ca 22 to 26 m as suggested and modeled by other workers and or mis 3 sea level was briefly higher than suggested by some coral reef studies correcting the shoreline elevations for gia brings their elevation in line with other sea level indicators the age of the kitty hawk beach ridges places the holocene shoreline well west of its present location at ca 3 to 2 ka the age of shoreline progradation is consistent with the ages of other beach ridge complexes in the southeast usa suggesting some regionally contemporaneous forcing mechanism

geomorphic thresholds and complex response of fluvial systems some implications for sequence stratigraphy first generation sequence stratigraphic models have dealt in a very rudimentary fashion with the response of fluvial systems to eustasy a major element of presently accepted models is that rivers incise when sea level falls and aggrade during the ensuing rise well established geomorphic principles state that fluvial systems are complex process response systems that can adjust to internal and external changes in other ways besides incision and aggradation by modifying their stream patterns and channel geometries application of geomorphic principles to sequence stratigraphic models results in the following observations during eustatic lowstands rivers may adjust to lowered base levels and changes in slope by modifying channel patterns therefore not all lowstands produce type 1 sequence boundaries type 1 sequence boundaries characterized by fluvial valley incision are more likely to develop when sea level drops below the shelf slope break resulting in topological relief near the strandline in which headwardly eroding knickpoints form rates of eustatic change although rapid in a geological context are sufficiently low that geomorphic systems can easily maintain their equilibrium during eustatic changes and migrate back and forth across the shelf without major modifications finally und r conditions of relatively static sea level sequences and parasequences of the same scale in time and space as those which form during eustatic change can be deposited as the result of purely intrinsic causes and responses of a fluvial system in general eustasy controls the location of deposition and erosion but the resultant stratal geometry is controlled by sediment supply and processes acting on the sediments as the shoreline moves across the shelf in response to eustasy

regional seismic stratigraphy and controls on the quaternary evolution of the cape hatteras region of the atlantic passive margin usa abstract seismic and core data combined with amino acid racemization and strontium isotope age data enable the definition of the quaternary stratigraphic framework and recognition of geologic controls on the development of the modern coastal system of north carolina u s a seven regionally continuous high amplitude reflections are defined which bound six seismic stratigraphic units consisting of multiple regionally discontinuous depositional sequences and parasequence sets and enable an understanding of the evolution of this margin data reveal the progressive eastward progradation and aggradation of the quaternary shelf the early pleistocene inner shelf occurs at a depth of ca 20 40 m beneath the western part of the modern estuarine system pamlico sound a mid to outer shelf lowstand terrace also early pleistocene with shelf sand ridge deposits comprising parasequence sets within a transgressive systems tract occurs at a deeper level ca 45 70 m beneath the modern barrier island system the outer banks and northern pamlico sound seismic and foraminiferal paleoenvironmental data from cores indicate the occurrence of lowstand strandplain shoreline deposits on the early to middle pleistocene shelf middle to late pleistocene deposits occur above a prominent unconformity and marine flooding surface that truncates underlying units and contain numerous filled fluvial valleys that are incised into the early and middle pleistocene deposits the stratigraphic framework suggests margin progradation and aggradation modified by an increase in the magnitude of sea level fluctuations during the middle to late pleistocene expressed as falling stage lowstand transgressive and highstand systems tracts thick stratigraphic sequences occur within the middle pleistocene section suggesting the occurrence of high capacity fluvial point sources debouching into the area from the west and north furthermore the antecedent topography plays a significant role in the evolution of the geomorphology and stratigraphy of this marginal system

bayhead deltas and shorelines insights from modern and ancient examples abstract bayhead deltas are important components of the rock record as well as modern estuaries hosting important hydrocarbon reservoirs and many coastal cities ports and large expanses of wetlands despite their significance few studies have summarized their occurrence and sedimentary characteristics in this paper we review the stratigraphic sedimentary and geomorphic characteristics of 68 modern and ancient bayhead deltas bayhead deltas are found in incised valleys structural basins fjords interdistributary bays of larger open ocean deltas and other backbarrier environments except for within fjords they generally prograde into shallower and more brackish waters than their open ocean equivalents as a result 80 of modern 68 of quaternary and 67 of ancient bayhead deltas have clinoform thicknesses of 10 m or less with 73 of modern bayhead deltas having clinoform thicknesses of 5 m or less additionally 89 of modern 81 of quaternary and 77 of ancient bayhead deltas examined are fluvial dominated we distinguish true bayhead deltas from their genetically similar bayhead shorelines which are not constructional features but sites of enhanced marsh or estuarine sedimentation near river mouths with inadequate rates of sediment delivery to form distributary channels and prograde into the estuary or lagoon we also distinguish confined bayhead deltas found in incised valleys structural basins and fjords from unconfined bayhead deltas found as incipient lobes of larger delta complexes and other back barrier lagoons the architecture of confined bayhead deltas is largely influenced by the limited accommodation brought about by the walls of the flooded valleys in which they are located as such confined bayhead delta ontogeny is controlled by many autogenic interactions within these valley walls both confined and unconfined bayhead deltas are sensitive to sea level rise climate controlled changes in sediment flux and tectonics their relatively small size connection with the terrestrial system and protected nature make them the ideal depositional system to record earth history including sea level and climate changes

burning peat and reworking loess contribute to the formation and evolution of a large carolina bay basin abstract carolina bays are nearly ubiquitous along 1300 km of the north american atlantic coastal plain but relatively few bays have been examined in detail making their formation and evolution a topic of controversy the lake mattamuskeet basin eastern north carolina usa is a conglomeration of multiple carolina bays that form a 162 km2 lake the eastern shoreline of the lake is made up of a 2 9 km wide plain of parabolic ridges that recorded rapid shoreface progradation the lower shoreface deposit contains abundant charcoal beds and laminae dated 6465 6863 cal yr bp corresponding with initiation of a lacustrine environment in the eastern part of the lake a core from the western part of the lake sampled a 1541 1633 cal yr bp charcoal bed at the base of the lacustrine unit indicating formation of this part of the basin postdates the eastern basin lake mattamuskeet has no relationship to the younger dryas or a linked impact event because rim accretion significantly postdates 12 000 cal yr bp the shoreline progradation and association of charcoal beds with the oldest lake sediment in both main parts of the basin suggest that fire and subsequent hydrodynamic processes were associated with initial formation of these carolina bays

late pleistocene to holocene evolution of the emba delta kazakhstan and coastline of the north eastern caspian sea sediment ostracods pollen and dinoflagellate cyst records six cores each approximately 10 m long of late pleistocene to holocene age were studied from the emba delta region in the north eastern caspian sea radiocarbon dates provide ages within the range of 47 820 to 12 020 cal bp for the middle sections and for post 1950 close to surface the ages fall within marine isotope stage mis 3 mis 2 and mis 1 with mis 4 also inferred four lithological units are present each separated by an erosional contact unit 4 is equated with mis 4 and consists of over consolidated east west trending aeolian sands deposited during the late pleistocene atelian lowstand unit 3 is equated with mis 3 and is a low energy shallow open water or lagoonal deposit based on ostracod faunas pollen from mesophilic trees is common confirming warm climatic conditions floristic elements such as engelhardia and carya were shared with east asia frequent taxodiaceae pollen occurs derived from glyptostrobus pensilis a seasonal freshwater swamp tree now found naturally only in isolated relict stands in east asia this suggests that the north eastern caspian region was a refugium supporting glyptostrobus swamp vegetation during mis 3 there is no evidence to indicate that these are reworked occurrences unit 2 consists of early khvalynian transgressive barrier sands and unit 1 of shoreface sands and muds of holocene age the late khvalynian highstand and the last glacial maximum lgm record are eroded by the mangyshlak unconformity after ca 12 500 cal bp the holocene interval contains frequent foraminifera and dinoflagellate cysts dinocysts of restricted marine affinity e g lingulodinium machaerophorum the dinocysts pterocysta cruciformis and impagidinium inaequalis are found commonly in the caspian sea for the first time results are compared with palynological and ostracod assemblages in surface samples from the eastern caspian sea coastal region

the early khvalynian stage in the caspian sea evolution pollen records palynofloras and reconstructions of paleoenvironments abstract in addressing the controversial issues of the late pleistocene paleogeography of the caspian basin an important role is given to the results of the spore pollen analysis and based on them reconstructions of climate and vegetation changes in the northern caspian region during the development of the early khvalynian transgression in this paper we present the main results of the palynological study of deposits chocolate clays and the overlying and underlying layers from the srednyaya akhtuba section of maximum stage of the early khvalynian transgression the materials are illustrated by pollen diagram with the data of spore pollen analysis and the detailed list of palynoflora recovered from the studied lower khvalynian sequences and complemented with photographs of pollen belonging to the principal autochtonous taxa and for comparison to some redeposited palynomorphs palynological materials indicate subaqual brackish marine and freshwater sedimentation of the sediments studied in periglacial landscapes and for the most part under very harsh climatic conditions the performed climate stratigraphic reconstructions do not contradict the data of absolute dating on the accumulation of the studied deposits during the late valdai ostashkov late glacial period during this interval in the territory of the study area plant communities of the glacial climate tundra steppe periglacial forest steppe periglacial steppe periglacial parklands and periglacial forests were developed the widespread occurrence in the composition of the periglacial vegetation cover of the studied region of the yernik formations from betula nana and shrub communities from betula fruticosa b nana alnaster fruticosus juniperus etc testifies to the severe climatic conditions and possibly the existence of sporadic permafrost in the cold stages stadials of the ostashkov late glacial period

the ponto caspian basin as a final trap for southeastern scandinavian ice sheet meltwater this paper provides new data on the evolution of the caspian sea and black sea from the last glacial maximum until ca 12 cal kyr bp we present new analyses clay mineralogy grain size nd isotopes and pollen applied to sediments from the river terraces in the lower volga from the middle caspian sea and from the western part of the black sea the results show that during the last deglaciation the ponto caspian basin collected meltwater and fine grained sediment from the southern margin of the scandinavian ice sheet sis via the dniepr and volga rivers it induced the deposition of characteristic red brownish chocolate coloured illite rich sediments red layers in the black sea and chocolate clays in the caspian sea that originated from the baltic shield area according to nd data this general evolution common to both seas was nevertheless differentiated over time due to the specificities of their catchment areas and due to the movement of the southern margin of the sis our results indicate that in the eastern part of the east european plain the meltwater from the sis margin supplied the caspian sea during the deglaciation until 13 8 cal kyr bp and possibly from the lgm that led to the early khvalynian transgressive stage s and chocolate clays deposition in the now emerged northern flat part of the caspian sea river terraces in the modern lower volga and in its middle basin in the western part of the east european plain our results confirm the release of meltwater from the sis margin into the black sea that occurred between 17 2 and 15 7 cal kyr bp as previously proposed indeed recent findings concerning the evolution of the southern margin of the sis and the black sea show that during the last deglaciation occurred a westward release of meltwater into the north atlantic between ca 20 and 16 7 cal kyr bp and a southward one into the black sea between 17 2 and 15 7 cal kyr bp after the red layers chocolate clays deposition in both seas and until 12 cal kyr bp smectite became the dominant clay mineral the east european plain is clearly identified as the source for smectite in the caspian sea sediments in the black sea smectite originated either from the east european plain or from the danube river catchment previous studies consider smectite as being only of anatolian origin however our results highlight both the european source for smectite and the impact of this source on the depositional environment of the black sea during considered period

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

on the fundamental difference between coal rank and coal type abstract this article addresses the fundamental difference between coal rank and coal type while theoretically settled long ago as being different aspects of coal systems science the two concepts are still often confounded in recent years this has resulted in the publication of several works stating that coal type changes with coal rank coal type refers solely to coals depositional origin and the maceral mineral admixture resulting from that origin coal types typically fall in to two categories humic coals developed from peat and sapropelic coals developed from organic mud either type may be allocthonous or autochthonous and within types further refinement of depositional environment can be made coal rank refers to the changes in geochemistry and resultant changes in reflectance caused by increasing thermal maturity of the coal thus it provides an overprint of maturity on existing coal types with proper techniques such as use of crossed polars and etching maceral forms can be differentiated even at high ranks and the original coal type determined

quantitative modeling of the evolution and geometry of incised valleys abstract incised valleys are critical stratigraphic features for unraveling long term earth surface processes and depositional history and commonly exhibit stratigraphic attributes that make them desirable fluid reservoirs while there is much descriptive documentation on architecture of incised valley fills and paleoenvironmental regimes relatively little work has focused on quantitative modeling of the dynamics of incised valley evolution here we use well constrained observations of incised valleys in experiments and the field to explore controls on valley geometry and develop a simple valley model to quantify the primary dynamics of incised valley evolution we document a strong tendency for incised valleys to widen downstream independent of the details of the relative base level curve or initial surface profile due primarily to the effects of increased sediment flux this is in general agreement with measurements of experimental and natural incised valleys though the degree of widening is less in natural systems due to greater sidewall resistance and smaller water discharge relative to valley size a first order model of incised valley evolution highlights three important trends valley aggradation and widening valley incision and widening and valley incision and narrowing the model reproduces the primary geometric responses to valley formation as measured from experiments valley width and depth both increase in response to increases in 1 local relative base level fall and 2 the initial offshore water depth finally we generalize the first order controls on valley geometry via dimensional analysis to show that long term valley narrowing is not readily produced from relative base level fall alone

influence of fluvial processes on the quaternary geologic framework of the continental shelf north carolina usa abstract digital single channel high resolution seismic reflection profiles were acquired from the insular continental shelf of north carolina usa along a data grid extending from oregon inlet northward 48 km to duck north carolina and from the nearshore zone seaward approximately 28 km total surveyed area 1334 km 2 these data were processed and interpreted to delineate principal reflecting horizons and develop a three dimensional seismic stratigraphic framework for the continental shelf that was compared to stratigraphic data from the shoreward back barrier estuarine and barrier island system six principal reflecting horizons designated r 0 through r 5 were present within the upper 60 m of the shelf stratigraphic succession three dimensional mapping of reflector r 1 demonstrated its origin from fluvial incision of the continental shelf during an episode or episodes of lowered sea level fluvial processes during development of reflector r 1 were responsible for extensive reworking and re deposition of sediment throughout most of the northern half of the study area five seismic stratigraphic units designated s 1 through s 5 were tentatively correlated with depositional sequences previously identified from the north carolina back barrier estuarine and barrier island system these five stratigraphic units span the quaternary period s 1 early holocene s 2 51 78 ka s 3 330 530 ka s 4 1 1 1 8 ma s 5 earliest pleistocene unit s 1 is composed of fine grained fluvial estuarine sediment that back filled incised streams during early holocene sea level rise the four other stratigraphic units s 2 s 5 display tabular depositional geometries low total relief and thicken toward the east southeast as their basal reflectors dip gently between 0 41 m km 1 0 02 and 0 54 m km 1 0 03 knowledge of the three dimensional subsurface stratigraphic architecture of the continental shelf enhances understanding of the development of shelf depositional successions and provides a framework for development of better quaternary sea level data especially offshore north carolina where such data are sparse

hardbottom morphology and relationship to the geologic framework mid atlantic continental shelf abstract high energy sediment starved continental shelves of the mid atlantic region have abundant hardbottoms that extend from the shoreface to the shelf edge because of the thin and irregularly distributed holocene sand sheet shelf morphology is determined mainly by outcropping tertiary and pleistocene stratigraphic units each unit and combination of units produces different hardbottom morphologies that depend upon the geometry and spatial relationships of the units lithology and patterns of stratification and subsequent weathering and erosion hardbottoms vary in surface relief from smooth flat surfaces to scarped surfaces with up to 10 m of relief the morphology ranges from sloping and stepped erosional ramps to vertical and undercut scarps with associated broad rubble ramps hardbottoms associated with each of the different gently dipping tertiary depositional sequences have distinctive morphologies hardbottoms developed on pleistocene units unconformably overlie the tertiary sequences as flat lying marine carbonates or cut into them as channel systems backfilled with fluvial and estuarine sediments initial dissection of hardbottoms produced highly convoluted surfaces that resulted from subaerial weathering stream erosion and karst formation during sea level lowstands during subsequent sea level highstands these rimary morphologies were greatly modified through the interaction of bioerosion and storms understanding continental shelf hardbottoms is critical for interpreting the sedimentology and stratigraphy of the atlantic coastal plain and for reconstructing paleoceanographic conditions for the following reasons 1 they are an extensive part of the stratigraphic record on shelves that are not actively subsiding and have small volumes of terrigenous input with low sediment accumulation rates 2 they are important stages in the formation of major stratigraphic unconformities condensed sections and sequence boundaries 3 they support diverse biological communities that produce primary carbonate sediments and are rapidly degraded and modified by bioerosion and physical processes supplying abundant new sediment to the continental shelf

wave train model for knickpoint migration rivers respond to a drop in their base level by incising the topography the upstream propagation of an incision as usually depicted by a knickpoint migration is thought to depend on several parameters such as the drainage area lithology and the amplitude of the base level drop we first investigate the case of the messinian salinity crisis that was characterized by the extreme base level fall 1500 m of the mediterranean sea at the end of the miocene the response of drainage areas of three orders of magnitude 103 to 106 km2 highlights the dominant role of the drainage area with a square root relationship in controlling the knickpoint migration after a base level fall a compilation of mean rates of knickpoint propagation for time durations ranging from 102 to 107 years displays a similar relationship indicating that successive wave trains of knickpoint can migrate in a river first wave trains linked to the release of the alluvial cover and then wave trains related to the bedrock incision which correspond to the real time response of rivers wave trains with very low retreat rates long lived knickpoints 1 my rather correspond to the response time of regional landscape

holocene evolution of the east texas coast and inner continental shelf along strike variability in coastal retreat rates abstract the low gradient east texas coast and inner continental shelf from sabine lake at the texas louisiana border to the western end of galveston island experienced extreme along strike variations in rates of holocene coastal retreat around 7 7 ka a barrier shoreline was located approximately 55 km offshore toward the western end of galveston island the shoreline retreated 55 km occupying a position on the lagoon side of the island by about 5 3 ka toward the texas louisiana border the shoreline retreated more gradually occupying a position seaward of sabine bank by 5 3 ka between 4 7 ka and 2 8 ka the shoreline at sabine bank retreated 30 km while galveston island prograded seaward bolivar peninsula began to accrete around 1 5 ka heald and sabine banks located on the inner continental shelf above terraced fluvial deposits of the trinity sabine incised valley are the only preserved remnants of these former shoreline positions fluctuating rates of sea level rise were not the forcing mechanism behind episodes of rapid shoreline retreat because these events were localized rather along strike variations in the rate of transgression were caused by the variable inner shelf gradients which increase towards the west and the orientation of the sabine incised valley and associated terraced fluvial deposits which trend northeast southwest parallel to shore as shorelines retreated over fluvial deposits these served as local sand sources that enabled barrier islands to persist figure 1 map of the east texas inner shelf showing locations of sabine heald and shepard banks paleotopographic map of the pleistocene surface thin contours siringan 1993 delineates the trinity sabine incised valley which formed during the last lowstand of sea level thomas and anderson 1994 bathymetric contours are shown as thick lines with bold numbers dots are core locations end page 405 offshore out of equilibrium with sea level once these sand sources became depleted and or sea level reached some critical threshold barrier shorelines became stranded offshore as banks and new shorelines formed landward the geologic setting of coastal areas specifically antecedent topography plays a primary role in controlling coastal evolution to accurately forecast long term centennial to millennial coastal evolution it is essential that impacts associated with variations in the underlying geology of coastal areas be incorporated into coastal forecasting models

controls on the geometry of incised valleys in the basal quartz unit lower cretaceous western canada sedimentary basin in southern alberta multiple episodes of fluvial erosion occurred during lower mannville basal quartz time early cretaceous creating a series of incised valley systems this study examines two of these valley networks in order to illustrate the geomorphic and genetic complexity of incised valley systems both valley networks are filled by a transgressive succession of fluvial to estuarine deposits isopach mapping of these deposits over an area of approximately 10 000 km 2 in southern alberta shows that both systems are dendritic to rectilinear in character with the trunk valley flowing from south to north along the length of the western canada sedimentary basin these systems were fed from the west south and east by a network of tributaries eustatic sea level changes may have played a role in initiating river incision but regional tectonic movements had an important influence on the history of accommodation change the periods of erosion appear to have been relatively brief because the valleys are narrow although confinement within cohesive mudstone rich paleosols of the underlying incised valley deposits may have slowed valley widening a relatively wet paleoclimate may also have contributed to the formation of narrow valleys by favoring the existence of single channel rivers the general morphology of the alberta foreland basin together with the distribution of unfilled relief associated with a preceding valley system and or of less resistant slightly older deposits determined the location of the trunk valleys uplift of the bow island arch sweetgrass arch to the east may have been responsible for a shift in the valley headwaters between the formation of the two valley systems synerosional block faulting in response to flexural loading had a significant influence on the geometry of the valley network through its control on the location and geometry of major tributary valleys the trunk valley is also significantly narrower and more deeply incised where it crosses the most pronounced uplifted block enhanced erosion at tributary junctions and valley bends produced localized areas ca 2 3 km in diameter where the valley fill is up to five times thicker and considerably coarser grained than the adjacent valley deposits such localized scour fills represent prime petroleum exploration targets

variations in shoreface progradation and ravinement along the texas coast gulf of mexico shoreface architecture evolution mid holocene to present and depths of transgressive ravinement were examined from sabine pass at the texas louisiana border to south padre island near the texas mexico border using 30 shoreface transects shoreface transects extend out to 16 m water depth each created from an echo sounding profile and on average seven sediment cores the shoreface is composed of three broad sedimentological facies the upper shoreface composed almost entirely of sand the proximal lower shoreface composed of sand with thickly to medium bedded 50 10 cm mud and the distal lower shoreface composed dominantly of mud with medium to thinly bedded 20 3 cm sand shoreface architecture and evolution is extremely variable along the texas coast shoreface gradients increase from 2 25 m km 1 in east texas to 3 50 m km 1 in south texas shoreface sands coarsen towards south texas east and south texas shoreface deposits are thin and retrograding whereas central texas shoreface deposits are thicker and prograding central texas is characterized by stacked shoreface successions whereas in east texas lower shoreface sands are preserved only in offshore banks preservation of shoreface deposits is low in south texas although eustatic fluctuations and accommodation space have a strong impact on overall mid holocene to present shoreface evolution and preservation potential along strike variations in sediment supply and wave energy are the main factors controlling shoreface architecture the transgressive ravinement surface varies from 6 to 15 m along the texas coast

seaward branching coastal plain and piedmont incised valley systems through multiple sea level cycles late quaternary examples from mobile bay and mississippi sound u s a abstract most incised valleys become more organized seaward through tributaries merging with the main trunk valley late quaternary incised valleys on the mississippi and alabama inner continental shelf branch seaward although they do coalesce towards the shelf break where they feed shelf edge deltas to link fluvial systems with their associated previously mapped incised valleys on the shelf and evaluate the contribution of small coastal plain valley systems to the lowstand systems tract high resolution seismic data and cores were collected from mobile bay eastern mississippi sound and the mobile bay head delta these data show four unconformity bounded stacked units and this study focuses on the upper two regionally mappable units the upper two unconformities were sampled in core as exposure surfaces and on the basis of stratigraphic position depth of incision and 14c dates are interpreted as sequence boundaries the shallowest sequence boundary a formed in response to the oxygen isotope stage 2 sea level lowstand while the underlying sequence boundary b formed in response to an earlier lowstand stage 6 a map of sequence boundary b shows a network of seaward branching valleys 20 35 m deep and 0 6 7 7 km wide that extend across mobile bay and mississippi sound these valleys which are bounded by well developed terraces are extensions of the piedmont mobile fluvial system and the coastal plain fowl and la batre fluvial systems a map of the stage 2 sequence boundary shows that all systems generally reoccupied their previous valley positions and are separated by interfluve plateaus valley fill between sequence boundary b and the stage 2 sequence boundary is generally composed of a basal unit of alluvial sediments overlain by bay head delta deposits however stage 2 to 1 valley fill is composed entirely of central basin sediments the presence of bay head delta deposits on the inner shelf indicates this depositional environment backstepped across the estuaries to modern positions backstepping likely occurred as the low gradient paleovalleys were inundated resulting in rapid rates of transgression fluvial gradients measured on sequence boundary b and the stage 2 sequence boundary below the modern mobile bay head delta plain and the estuaries are very low 1 3 0 3 m km the mobile bay head delta and upper mobile bay are confined by steep topography which opens basinward into the low gradient shorelines surrounding lower mobile bay and mississippi sound during falling sea level channel branching likely occurred as the low gradient fluvial systems extended basinward beyond the confined topography these channels incised as sea level fell below the steeper shelf break during the lowstand stage 2 valley morphology is partially influenced by the position of the underlying stage 6 valleys both coastal plain and piedmont valley systems exhibit compound fill indicating that differentiation between these types of incised valleys cannot be based on valley fill architecture alone

on the age of the khvalynian deposits of the caspian sea coasts according to 14c and 230th 234u methods during the second half of the late pleistocene the caspian experienced repeated transgressions early and late khvalynian and regressions enotaevsk and mangyshlak with an oscillation amplitude of 120 e150 m the question about the age of the khvalynian deposits is controversial the investigation presents the age chronology of the khvalynian deposits of the caspian coasts on the basis of marine terrace stratigraphy and 14 c and 230 th 234 u dating conducted in the laboratory of the saint petersburg state university forty samples of mollusc material from khvalynian deposits were dated for dating the shells of index genus didacna from the deposits of marine terraces with different elevations were sampled besides shells a fragment of bone from equus sp was dated the analysis of dating showed that during the maximum of the late valdai wurm glaciation the khvalynian basin was in a regressive situation the maximum stage 48 to 50 m of the early khvalynian transgression was not dated transgressive stages of the early khvalynian basin with sea levels of 35 and 22 m occurred during the period of deglaciation approximately 16 ka cal bp and 14 ka cal bp the transgressive stages of the late khvalynian basin with sea level at about 0 m and 12 m occurred 14e12 ka cal bp probably the age of deposits of makhachkala stage with level about 0 m reflected an allerod warming and the age of deposits of sartassy stage with level about 12 is associated with warming at the end of younger dryas under cold climate conditions of younger dryas the level of the late khvalynian basin fell increasingly continental climatic conditions during the boreal period of the holocene resulted in the mangyshlak regression 2015 elsevier ltd and inqua

controls on lower coastal plain valley morphology and fill architecture abstract small rivers that form at the apex of the coastal prism are common along many passive margins they typically have drainage basins 1000 km2 and their headwaters are isolated to low relief areas of the previous highstand shoreline as sea level fall exposes the apex of the coastal prism incision and drainage basin evolution of those small rivers should be strongly influenced by coastal paleotopography but previous work suggests that paleodischarge is the dominant control on incised valley dimension to examine the controls on the morphologic evolution of small incised valleys we examined 20 incised valleys in north carolina situated close to the last interglacial shoreline including coastal prism incised valleys which have well developed dendritic drainage networks on the highstand shoreline topography and tributary incised valleys which form adjacent to and merge with larger piedmont incised valleys coastal prism n 18 and tributary n 2 incised valley width measured at the common bayhead delta location is proportional to drainage basin area long term discharge however that comparison location overlaps with the knickzone only for the larger river systems the knickzone of small river systems is located down dip from the modern bay head delta which is likely due to slower rates of knickpoint migration we use geophysical and lithologic data from three incised valleys to highlight differences in regional valley morphology that can be used to distinguish between coastal prism and tributary incised valleys the newport and north coastal prism incised valleys connect to small sangamonian drainage networks of 210 km2 and 50 km2 respectively those valleys widen and deepen at the knickzone which is also where smaller tributary systems merge with the main trunk valley the scuppernong tributary incised valley has a drainage basin of 400 km2 and can be differentiated from other incised valleys based on the absence of a compound fill and continuous seaward deepening and widening from the upstream limit of the knickzone the knickzone is the junction of the scuppernong with the adjacent larger roanoke incised valley the depth of which controls base level for the scuppernong the dramatic scuppernong valley widening in a down dip direction is principally due to highly erosive bay ravinement processes associated with the adjacent much larger drowned roanoke incised valley these varying modes of valley evolution specifically controls of paleotopography on valley incision and ravinement explain the morphologies of small drowned river mouth estuaries and improve understanding of basin scale sediment transport pathways

late pleistocene climatic events reflected in the caspian sea geological history based on drilling data abstract the analysis of seismic acoustic profiles and drilling data from the northern caspian showed the climatic events are quite distinguishable in the upper pleistocene sedimentary sequence the climatic events of the first half of late pleistocene mis 5 resulted in the onset of two warm water transgressive basins late khazarian and hyrcanian ones though cooler than at the late khazarian transgression the climate during the hyrcanian time was attributable to interglacial one as the glacial stage mis 4 approached its maximum under conditions of a dry and cold climate the hyrcanian sea basin regressed the atelian regression of the caspian sea corresponded to mis 4 stage and to the initial phases of the mis 3 interstadial warming the development of the global interstadial warming led to a considerable increase in the surface runoff from the catchment and resulted in the rising of the atelian lake level and the onset of the first phase of the khvalynian transgression the sea level rising was interrupted at the time of maximum cooling and aridization at mis 2 and resumed when the ice sheet was decaying the conspicuous climatic events known as warm phases of bolling and allerod promoted the ice sheet melting along with thawing of permafrost the latter having been widespread in the volga drainage basin all the above contributed to the khvalynian transgression the chocolate clays were accumulated in the volga estuary as well as in depressions of the pre khvalynian topography phases of a noticeable cooling known as the oldest older and younger dryas marked by a decrease in the runoff volume from the caspian drainage basin are correlated with regressive stages in the khvalynian basin history the khvalynian came to its end at the time of the first sharp warming that resulted in the rise of the caspian level and is generally taken as marking the pleistocene holocene boundary the mangyshlakian regression is dated to the holocene and was essentially a response of the caspian sea to the increase in the climate continentality during the boreal period

how and where do incised valleys form if sea level remains above the shelf edge sequence stratigraphic models predict that during relative sea level fall rivers will cut incised valleys across the exposed continental shelf incision is driven by the exposure of convex up topography and consequent downstream increases in stream power modern shelf profiles from passive margin and foreland basin settings show that profile convexities occur at the shelf edge and at the current highstand coastline the coastal prism in nonglacial times which form much of earth9s history it is unlikely that the shelf edge was subaerially exposed during such periods patterns of incision would have been primarily determined by the shape of the coastal prism on the basis of modern shelf profiles from passive margin and foreland basin settings river incision of as much as 20 to 70 m would be centered upon the preceding highstand coastline and would be restricted to the inner part of the shelf deeper incised valleys would only result from exposure of the shelf edge or from the processes involved in the formation of submarine canyons

holocene sea level changes along the north carolina coastline and their implications for glacial isostatic adjustment models abstract we have synthesized new and existing relative sea level rsl data to produce a quality controlled spatially comprehensive database from the north carolina coastline the rsl database consists of 54 sea level index points that are quantitatively related to an appropriate tide level and assigned an error estimate and a further 33 limiting dates that confine the maximum and minimum elevations of rsl the temporal distribution of the index points is very uneven with only five index points older than 4000 cal a bp but the form of the holocene sea level trend is constrained by both terrestrial and marine limiting dates the data illustrate rsl rapidly rising during the early and mid holocene from an observed elevation of 35 7 1 1 m msl at 11062 10576 cal a bp to 4 2 m 0 4 m msl at 4240 3592 cal a bp we restricted comparisons between observations and predictions from the ice 5g vm2 with rotational feedback glacial isostatic adjustment gia model to the late holocene rsl last 4000 cal a bp because of the wealth of sea level data during this time interval the ice 5g vm2 model predicts significant spatial variations in rsl across north carolina thus we subdivided the observations into two regions the model forecasts an increase in the rate of sea level rise in region 1 albemarle currituck roanoke croatan and northern pamlico sounds compared to region 2 southern pamlico core and bogue sounds and farther south to wilmington the observations show late holocene sea level rising at 1 14 0 03 mm year 1 and 0 82 0 02 mm year 1 in regions 1 and 2 respectively the ice 5g vm2 predictions capture the general temporal trend of the observations although there is an apparent misfit for index points older than 2000 cal a bp it is presently unknown whether these misfits are caused by possible tectonic uplift associated with the mid carolina platform high or a flaw in the gia model a comparison of local tide gauge data with the late holocene rsl trends from regions 1 and 2 support the spatial variation in rsl across north carolina and imply an additional increase of mean sea level of greater than 2 mm year 1 during the latter half of the 20th century this is in general agreement with historical tide gauge and satellite altimetry data

linking framework geology and nearshore morphology correlation of paleo channels with shore oblique sandbars and gravel outcrops abstract this work describes a newly discovered spatial correlation between paleo channels and nearshore morphology along the barrier islands of northeastern north carolina and southeastern virginia u s mid atlantic coast these nearshore morphological features include regions of shore oblique sandbars and coincident gravel outcrops that previously have been linked to erosional hotspots at the shoreline these new findings have direct bearing on both nearshore morphodynamics and shoreline management paleo channels were identified in the chirp seismic record and compared to shore oblique sandbar locations discerned from bathymetric data and corroborated by gravel outcrops depicted in the side scan record both graphical correlation and statistical cross correlation analyses revealed a significant spatial relationship between these features with higher statistical correlation for channels 500 m wide seismic records also indicate that the gravel outcrops seen on the updrift flanks of the shore oblique bars are surface expressions of the underlying geology we hypothesize that these outcrops are composed of relict channel fill sediments that interact with the hydrodynamic regime to produce sorted bedforms the bathymetric anomalies then serve to alter incident wave energy and affect shoreline behavior the spatial and temporal stability of these features over several years and through a variety of wave conditions suggests some degree of underlying geologic control while the mechanisms responsible for this relationship remain speculative these results may bridge the gap between studies focusing on framework geology and its influence on shoreline change and those that investigate bar morphodynamics and the initiation of sorted bedforms

controls on late quaternary incised valley dimension along passive margins evaluated using empirical data incised valleys are canyon like features that initially form near the highstand shoreline and evolve over geological time as rivers erode into coastal plains and continental shelves to maintain equilibrium gradient profiles in response to sea level fall most of these valleys flood during sea level rise to form estuaries incised valley morphology strongly controls the rate of creation of sediment accommodation valley fill facies architecture and the preservation potential of coastal lithosomes on continental shelves and affects coastal physical processes nonetheless little is known about what dictates incised valley size and shape and whether these metrics can be used to explain principal formation processes the main control on alluvial channel morphology over human time scales is discharge this is based on numerous empirical studies and is well constrained because all variables are easily measured at this short time scale knowledge of long term river evolution over a complete glacio eustatic cycle on the contrary remains largely conceptual experimental and based on individual systems because variables that are thought to drive morphological change are not easily quantified in spite of this difficulty existing models of incised valley formation at the coast suggest that valley evolution is driven largely by downstream forcing mechanisms highlighting sea level and shelf gradient morphology as the dominant controls on valley incision although valleys are cut by rivers whose channels are a direct reflection of discharge little empirical data exist in coastal areas to address the degree to which valley evolution is governed by upstream controls the late quaternary is the best time period to examine because it provides the most complete sedimentary record and many variables including sea level tectonics substrate lithology and drainage network characteristics are accurately constrained here 38 late quaternary valleys along the coast of two different passive continental margins are compared which suggests that valley shape and size are governed primarily by upstream intrinsic controls such as discharge valley width depth and cross sectional area are found to be predictable at the highstand shoreline and are scaled with the size of their drainage basin which has important implications for estimating sediment discharge to continental shelves and deep water environments during periods of low sea level

transition of a regressive to a transgressive barrier island due to back barrier erosion increased storminess and low sediment supply bogue banks north carolina usa abstract although back barrier erosion is a prevalent process of island narrowing it is often overlooked in conceptual models of barrier island evolution in many wave dominated barrier island settings the absence of overwash precludes landward movement of the back barrier shoreline and hence the island as a whole from sustaining its width typically regressive barriers are wide and exhibit high elevations with the most seaward dune ridge possessing the highest elevation this morphology may prevent overwash and inlets from breaching the barrier and therefore the associated sediment from reaching the back barrier shoreline for millennia back barrier shoreline erosion from sea level rise and storms can be permanent in the absence of sediment supply from rivers overwash and inlet processes with continued narrowing and lowering of the island regressive barriers may reach a critical state making overwash and inlet formation imminent and transitioning the island to a transgressive barrier the modern day morphologic variability along the 40 km long island of bogue banks north carolina includes both regressive and transgressive segments making this setting ideal for examining whether the transition between these barrier island types is gradual or threshold driven bogue banks consists of two discrete segments characterized by high elevation beach ridges large island widths and stratigraphy consistent with regressive barrier islands these regressive island segments are separated by a broad narrow section of the island devoid of any washover fans flood tide deltas or other transgressive elements analyses of seismic data from the inner continental shelf reveal paleochannels intersecting the wide sections of the island while the narrow central part of the island occupies an inter fluvial area reworking of fluvial sediment from paleochannels was an important sediment source for the barrier during regression optically stimulated luminescence osl dates from the most landward beach ridges constrained initiation of island regression at 3000 cal yr bp close to when there was a significant decrease in the rate of relative sea level rise from 5 mm yr to 0 8 mm yr transects of cores seismic data ground penetrating radar data and radiocarbon and osl dates show that prior to 1500 cal yr bp the central narrow section of the island was wide and progradational similar to adjacent areas back barrier erosion of the central part of the barrier primarily caused island narrowing as a result of increased storminess which occurred around the medieval climate anomaly 1100 cal yr bp this part of the island was more vulnerable to erosion than adjacent areas due to increased bay ravinement bogue sound is widest there and its lower elevation farther away from paleochannel sediment source relict inlet channels exist along the central portion of the island formed within the last 250 yr and likely closed shortly after formation the presence of historical inlets along the narrow central section of the island indicates bogue banks may be nearing a critical width threshold and will subsequently transition to a transgressive barrier because the change in barrier morphology associated with back barrier erosion occurred over a period of time when the rate of sea level rise was relatively low low sediment supply and increased storm frequency are shown to be the main forcing mechanisms of island narrowing these impacts in addition to a predicted increase in sea level rise rates and human modifications e g maintenance of a high elevation foredune closing of inlets prevention of island overwash and associated sediment delivery to the back barrier shoreline will likely promote rapid transition of regressive barrier islands to those dominated by transgressive processes

fluvial responses to climate and sea level change a review and look forward summary fluvial landforms and deposits provide one of the most readily studied quaternary continental records and alluvial strata represent an important component in most ancient continental interior and continental margin successions moreover studies of the long term dynamics of fluvial systems and their responses to external or allogenic controls can play important roles in research concerning both global change and sequence stratigraphy as well as in studies of the dynamic interactions between tectonic activity and surface processes these themes were energized in the final decades of the twentieth century and may become increasingly important in the first decades of this millennium this review paper provides a historical perspective on the development of ideas in the fields of geomorphology quaternary geology vs sedimentary geology and then summarizes key processes that operate to produce alluvial stratigraphic records over time scales of 103 106 years of particular interest are changes in discharge regimes sediment supply and sediment storage en route from source terrains to sedimentary basins as well as changes in sea level and the concept of accommodation late quaternary stratigraphic records from the loire france mississippi usa colorado texas usa and rhine meuse the netherlands rivers are used to illustrate the influences of climate change on continental interior rivers as well as the influence of interacting climate and sea level change on continental margin systems the paper concludes with a look forward to a bright future for studies of fluvial response to climate and sea level change at present empirical field based research on fluvial response to climate and sea level change lags behind a the global change community s understanding of the magnitude and frequency of climate and sea level change b the sequence stratigraphic community s desire to interpret climate and especially sea level change as forcing mechanisms and c the modelling community s ability to generate numerical and physical models of surface processes and their stratigraphic results a major challenge for the future is to catch up which will require the development of more detailed and sophisticated quaternary stratigraphic sedimentological and geochronological frameworks in a variety of continental interior and continental margin settings there is a particular need for studies that seek to document fluvial responses to allogenic forcing over both shorter 102 103 years and longer 104 106 years time scales than has commonly been the case to date as well as in larger river systems from source to sink studies of quaternary systems in depositional basin settings are especially critical because they can provide realistic analogues for interpretation of the pre quaternary rock record

a late quaternary multiple paleovalley system from the adriatic coastal plain biferno river southern italy abstract a buried paleovalley system up to 2 km wide and exceeding 50 m in relief made up of multiple cross cutting depressions incised into the lower pleistocene bedrock is reported from the central adriatic coastal plain at the mouth of biferno river through a multi proxy approach that included geomorphological stratigraphic sedimentological and paleontological benthic foraminifers ostracods and molluscs investigations the facies architecture of distinct superposed valley fills is reconstructed and their relative chronology established along a transverse profile with extremely high data density average borehole spacing 75 m regional tectonic uplift appears as the major controlling factor of initial middle pleistocene river down cutting and paleovalley formation in contrast glacio eustatic fluctuations drove fluvial system response over the last 120 ky when valley incision was primarily induced by the last glacial base level lowering and climatic forcing a fragmented record of coastal and shallow marine deposits is available for the lower paleovalley fill which is penetrated by a limited borehole dataset multiple erosion phases probably related to the post mis 5e sea level fall are reconstructed from the upper paleovalley fill where a buried fluvial terrace succession is identified a few tens of meters below the ground surface the flat surfaces of two buried fluvial terraces suggest longer term stepped relative sea level fall and are correlated with fluvial incisions that took place possibly at the mis 5 4 transition and at the mis 3 2 transition respectively a laterally extensive gravel body developed on the valley floor during the last glacial maximum during the ensuing latest pleistocene early holocene sea level rise the biferno paleovalley was transformed into an estuary upstream from the maximum shoreline ingression the vertical succession of well drained floodplain poorly drained floodplain and swamp deposits evidences increasing marine influence in the estuary in response to continuing sea level rise the interfluves were drowned around 8 cal ky bp when brackish conditions developed in the study area decreasing marine influence in the uppermost 15 m of the paleovalley fill suggests the onset of the modern delta when the rate of sea level rise was overwhelmed by sediment supply delta progradation took place

the geology petrology palynology and geochemistry of permian coal basins in tanzania 2 songwe kiwira coalfield abstract this study provides coal quality petrological palynological and geochemical rock eval data on permian coal seams and associated shales and mudstones of the karoo supergroup of the songwe kiwira coalfield tanzania the coal seams which have a cumulative thickness of 6 80 m occur in the shale coal sandstone facies of the mchuchuma formation of artinskian to kungurian age coal quality data calorific values volatile matter contents and vitrinite reflectances indicate high volatile c bituminous to high volatile a bituminous coals having relatively high ash yields 22 49 wt and highly variable sulphur contents 0 17 9 2 wt they could be used to fuel small scale power generation units thereby providing electricity to nearby towns and villages also the coals could be used as a substitute for wood which is becoming increasingly scarce in rural tanzania charcoal is still the main energy source for cooking and wood is used extensively in brick kilns and for making roofing tiles petrological analysis indicated that the coals are dominated by dull to banded dull lithotypes with seams at the base of the mchuchuma formation enriched in inertinite macerals up to 83 vol whereas up section vitrinite contents increase palynological analyses indicated that the assemblage in the lower mchuchuma formation scheuringipollenites assemblage is dominated by trilete spores whereas in the remainder of the section non taeniate disaccates dominate scheuringipollenites protohaploxypinus assemblage facies critical macerals suggest for most seams a marsh wet forest swamp depositional setting which is consistent with the palynological data rock eval analyses indicate type ii iii kerogen with tmax c values ranging from 426 to 440 corresponding to the early stage of hydrocarbon generation thermal alteration indices 2 to 2 and vitrinite reflectance levels 0 60 0 83 ro support the rock eval maturity assessment and despite the predominance of terrestrial derived organic matter there is evidence of oil generation and expulsion in the form of cavity and fracture filling exsudatinite

control of upstream variables on incised valley dimension abstract it is well documented that sea level fell during the last glacial maximum shifting graded stream profiles out of equilibrium and causing rivers to incise into continental shelves although incised valleys have been heavily researched the interplay between upstream and downstream controls on incised valley dimension are not well constrained to address this lack of understanding we examined the cross sectional dimension of nine incised valleys located across the northern gulf of mexico margin and bounded by the sequence boundary associated with the last sea level lowstand these incised valleys are distinguished by drainage basins that vary in size by three orders of magnitude cover a margin that presently has a steep climate gradient and extend across a continental shelf that varies along strike in width and gradient incision depths vary for valleys that have similar gradient profiles but different drainage basin areas suggesting significant control of upstream variables on incised valley morphology additionally these data show a strong linear correlation between drainage basin area and incised valley cross sectional area this suggests applicability of the empirically derived relationship between modern discharge and cross sectional channel area to incised valleys when compared at the maximum highstand shoreline of the previous sequence incised valley dimension adjusts over a longer period than the lowstand and is in equilibrium with drainage basin area which is considered a proxy for long term discharge although base level fall promotes incision upstream variables control incised valley dimensions

the ponto caspian region environmental consequences of climate change during the late pleistocene evolution of the caspian and black sea pont basins environments was analyzed in comparison and both general and specific features of their development under multi scale and multi directional changes of climate during the late pleistocene were identified the cold extensive transgressions of the caspian sea and the transgressions of the caspian type of the pontian basin not exceeding the present sea level developed synchronously in the cold glacial climatic epochs the maximum height of level of the caspian transgressions was limited by the height of the manych threshold and the transgressions of the caspian type in the pontian basin by the height of the bosporus threshold the warm small transgressions of the caspian sea and the marine mediterranean type transgressions of the pont with maximum level developed during the warm interglacial epochs in the caspian these occurred mainly during the interglacial endothermal cool and moist phases while marine transgressions of the pont correlated with the interglacial transgressions of the world ocean the cold transgressions of the caspian sea and the caspian type transgressions of the pontian basin developed asynchronously with the transgressions of the world ocean

micropaleontologic record of late pliocene and quaternary paleoenvironments in the northern albemarle embayment north carolina u s a abstract micropaleontological data provide a strong actualistic basis for detailed interpretations of quaternary paleoenvironmental change the 90 m thick quaternary record of the albemarle embayment in the mid atlantic coastal plain of the usa provides an excellent opportunity to use such an approach in a region where the details of quaternary environmental change are poorly known the foraminiferal record in nine cores from the northern outer banks east of albemarle sound north carolina indicates the deposition of subhorizontal mostly open marine early to late pleistocene units unconformably upon a basement of late pliocene reduced oxygen fine grained shelf basin deposits pollen data record several warm cool fluctuations within the early to mid pleistocene deposits diatom data indicate that some fresh and brackish water units occur within the generally open marine pleistocene succession a channel cut by the paleo roanoke river during the last glacial sea level lowstand occurs in the northern part of the study area pollen indicates that the basal fluvial valley fill accumulated in cooler than modern climate conditions in the latest pleistocene overlying silts and muds accumulated under cool climatic estuarine conditions according to diatom and pollen data radiocarbon ages from the estuarine deposits indicate that the bulk of these sediments accumulated during the latest pleistocene the estuarine channel fill deposits are overlain by holocene open marine sands deposited as the rising sea transgressed into the estuary approximately 8 5 to 9 0 kyr bp within the barrier island drill cores of this study fully marine sedimentation occurred throughout the holocene however immediately west of the present barrier island mid to late holocene estuarine deposits underlie the modern albemarle sound the islands that currently form a continuous barrier across the mouth of albemarle sound have a complex history of holocene construction and destruction and large portions of them may be less than 3 kyr old the barrier island sands overlie open marine sands of colington shoal in the north and to the south overlie fluvial and marine sand filling paleo roanoke tributary valleys the pleistocene sediments underlying the northern outer banks study area are mainly of open inner to mid shelf origin if as is likely sea level continues to rise a return to such environmental conditions is likely in the near future

quantitative analysis of the stratigraphic architecture of incised valley fills a global comparison of quaternary systems abstract facies models of the internal fills of incised valleys developed in shelf and coastal settings during cycles of relative sea level change are largely conceptual descriptive and qualitative in form moreover they are commonly bespoke to individual examples here a database driven quantitative statistical analysis of 87 late quaternary incised valley fills ivfs has been undertaken to assess the general validity and predictive value of classical facies models for ivfs and to investigate the relative importance of possible controls on their stratigraphic organization based on datasets from the published literature stored in a sedimentological database the geometry and proportion of systems tracts and of architectural elements of different hierarchies within ivfs are quantified these variables were analysed to assess how they vary in relation to parameters that represent potential controlling factors relative sea level stage continental margin type drainage basin area valley geometry basin physiography and shoreline hydrodynamics the stratigraphic organization of the studied coastal plain ivfs is generally consistent with that represented in facies models the primary control being the rate and magnitude of relative sea level change however results from this study demonstrate significant variability in the stratigraphic architectures of ivfs which is not accounted for by existing models variations in the facies architecture of coastal plain and cross shelf valley fills can be attributed to controls other than sea level and expressed in relationships with continental margin type basin physiography catchment area river system size and shoreline hydrodynamics the following primary findings arise from this research i compared to their counterparts on passive margins coastal plain ivfs hosted on active margins contain on average a higher proportion of fluvial deposits and a lower proportion of central basin estuarine deposits estuarine deposits tend however to be thicker this suggests a control on ivf stratigraphic architecture exerted by distinct characteristics of the tectonic setting of the host continental margins notably basin physiography rates and mode of sediment supply and nature of sediment load ii the thickness and proportion of lowstand systems tract are positively correlated with coastal plain ivf dimensions likely reflecting the role of drainage basin area in dictating the scale of the fluvial systems that carved and infilled the valleys iii positive correlations are observed between the thickness of fluvial deposits bayhead delta deposits and central basin estuarine deposits versus coastal plain ivf dimensions and valley catchment area this suggests a control exerted by the river system scale on sediment supply rates and on the accommodation determined by valley size iv positive correlations between the thickness and proportion of barrier complex deposits within cross shelf ivfs versus mean shelf gradient indicate that the geometry of the shelf might control the establishment and preservation of barrier island environments in incised valleys located on the shelf v correlations between the width of coastal plain ivfs and present day mean tidal range at the shoreline indicate that tidal dynamics may contribute to the widening of the incised valleys positive correlation is observed between the proportion of tide dominated elements in highstand ivf deposits and ivf width suggesting possible effects of interplays between hydrodynamic conditions and the geometry of incised valleys on their infills this study highlights the complexity of the internal fills of incised valleys which must be considered when attempting the application of facies models of ivfs to rock record interpretations or as predictive tools in subsurface studies

chocolate clays of the northern caspian sea region distribution structure and origin abstract the chocolate clays commonly comprise a part of the lower khvalynian sequence in the northern caspian lowland and in the volga region the mode of occurrence varies from continuous to patchy mosaic all the clay deposits are confined to pre khvalynian depressions of various origins there are several sub facies distinguishable within the chocolate clay facies mono clayey typologic stratified sandy clayey and silty clayey judging from specific features of lithology geomorphic position mode of occurrence mollusc fauna composition and radiocarbon dates the chocolate clays represent a specific facies of the lower khvalynian sediments and cannot be considered as an individual stratigraphic unit