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Hurricanes with high winds can generate strong ocean circulation, storm surges, and large surface waves that impact coastal regions. In 2018, Hurricane Florence crossed the narrow continental shelf and made landfall in Onslow Bay, North Carolina, USA, a 160 km curved embayment rimmed by a chain of barrier islands with inlets and narrow back-barrier lagoons. This storm had significant impacts to Bear Island, an undeveloped barrier island, including overwash and shoreline recession of the beach/dune system of up to 40 m. The objective of this study is to apply a flexible mesh numerical model to investigate wave generation by wind over the ocean, and the fine-scale response of flow and storm surge in shallow nearshore areas including inlets and back-barrier estuaries. The hydrodynamic conditions surrounding four different barrier island systems that received different hurricane wind and wave forcing relative to the cyclone eye are investigated. The highest total water levels around the barrier islands are driven by the combined tide, storm surge and waves, resulting in complex circulation patterns related to the network of shallow channels in the back-barrier environment. [ABSTRACT FROM AUTHOR]

Pamlico Sound, a large back‐barrier estuary in North Carolina, is under threat of climate change due to increased storm activity and sea level rise. The response of this system is investigated by considering what has already happened during changes in sea level over the late Holocene epoch. The hydrodynamic changes that occurred in response to geomorphic evolution are simulated using a 3‐D numerical model for four distinct "time‐slice" scenarios. To accomplish this, the present‐day bathymetry was obtained from a high‐resolution digital elevation model, and paleobathymetric grids were developed from sediment cores and seismic observations. Using the same hydrodynamic forcing for each geomorphic scenario, the models are compared to assess the combined response to: different inlets connecting the back‐barrier estuary to the ocean, changes in basin geomorphology due to sedimentation, and sea level rise. The results indicate that these factors have a considerable effect on hydrodynamics, waves, and salinity in the estuary. The time‐averaged tidal ranges were up to 3 times as high for the past environments in comparison with present‐day water level elevations, and maximum current velocities were over 3 times higher in regions close to paleo‐inlets. The simulations for each time slice suggest that the salinity distribution in Pamlico Sound is strongly influenced by the hydraulic connectivity with other estuaries and the number and size of tidal inlets through the barrier island system. The results indicate that changes to barrier systems induce strong, nonuniform, and complex responses in back‐barrier estuaries with regime shifts in hydrodynamic energy and water mass properties. Key Points: A modeling approach is developed for simulating the response of an estuary to different geomorphological conditions over a long time scaleGeological observations were used to define inlet locations, basin morphology, and sea levels in the hydrodynamic modelThe results indicate controls on the water levels, current velocities, and salinity distributions in paleo‐estuarine environments [ABSTRACT FROM AUTHOR]

In support of efforts to reconstruct relative sea level ( RSL), we investigated the utility of foraminifera, diatoms and bulk-sediment geochemistry (δ13C, C:N and parameters measured by Rock-Eval pyrolysis) as sea-level indicators in Eurasian sub-Arctic salt marshes. At three salt marshes (<15 km apart) in Dvina Bay (White Sea, Russia), we collected surface sediment samples along transects from subtidal to Taiga forest environments. Foraminifera at all sites formed bipartite assemblages, where elevations below mean high higher water ( MHHW) were dominated by Miliammina spp. and elevations between MHHW and the highest occurrence of foraminifera were dominated by Jadammina macrescens and Balticammina pseudomacrescens. Five high-diversity groups of diatoms were identified and they displayed pronounced variability amongst the study sites. Bulk-sediment geochemistry recognized two groups (clastic-dominated environments below MHHW and organic-rich environments above MHHW). As one group included subtidal elevations and the other included supratidal elevations, we conclude that the measured geochemical parameters are not stand-alone sea-level indicators. Core JT2012 captured a regressive sediment succession of clastic, tidal-flat sediment overlain by salt-marsh organic silt and freshwater peat. The salt-marsh sediment accumulated at 2804±52 years before present and preserved foraminifera ( Jadammina macrescens and Balticammina pseudomacrescens) with good analogy to modern assemblages indicating that RSL was +2.60±0.47 m at this time. Diatoms confirm that marine influence decreased through time, but the lack of analogy between modern and core assemblages limited their utility as sea-level indicators. Geochemical parameters also indicate a reduction in marine influence through time. We conclude that RSL reconstructions derived from salt-marsh sediment preserved beneath Eurasian sub-Arctic peatlands can provide valuable insight into the spatio-temporal evolution of the Fennoscandian and Eurasian ice sheets. [ABSTRACT FROM AUTHOR]

Moran, K.L.; Mallinson, D.J.; Culver, S.J.; Leorri, E., and Mulligan, R.P., 2015. Late Holocene evolution of Currituck Sound, North Carolina, USA: Environmental change driven by sea-level rise, storms, and barrier island morphology. The Holocene evolution of Currituck Sound, North Carolina, is investigated using geological data and a hydrodynamic model to understand how this depositional basin changed in response to sea-level rise and regional climate patterns. Five depositional units (one Pleistocene and four Holocene) are defined based on geophysical surveys, lithofacies, biofacies, and geochronological data. The earliest Holocene unit ( ca. 5000 cal YBP) represents a midsalinity (10-25‰) sand shoal above the transgressive ravinement surface. This unit is overlain, successively, by (1) a freshwater swamp forest deposit, (2) a relatively saline (25-35‰) back-barrier estuarine deposit associated with increased inlet activity, and (3) a mid- to low-salinity (<10‰) deposit that is typical of modern (post-1827) Currituck Sound, a back-barrier estuary with no inlets in the barrier island. Geomorphic reconstructions provided the boundary conditions input to hydrodynamically model tide and current patterns and to constrain the probable size and location of inlets. The evolution of this system depends on sea-level rise and barrier morphology, regional hydrological factors, and regional climatic conditions, which modulate storm impacts and inlet activity along the fronting barrier system. The late Holocene stratigraphy reflects climate variability also recorded in the sediments of Chesapeake Bay (to the north) and Pamlico Sound (to the south) and is consistent with an increase in tropical cyclone activity during the Medieval Climate Anomaly and subsequent decrease in tropical storm activity since ca. 500 cal YBP. [ABSTRACT FROM AUTHOR]

Salt-marsh sediments provide accurate and precise reconstructions of late Holocene relative sea-level changes. However, compaction of salt-marsh stratigraphies can cause post-depositional lowering (PDL) of the samples used to reconstruct sea level, creating an estimation of former sea level that is too low and a rate of rise that is too great. We estimated the contribution of compaction to late Holocene sea-level trends reconstructed at Tump Point, North Carolina, USA. We used a geotechnical model that was empirically calibrated by performing tests on surface sediments from modern depositional environments analogous to those encountered in the sediment core. The model generated depth-specific estimates of PDL, allowing samples to be returned to their depositional altitudes. After removing an estimate of land-level change, error-in-variables changepoint analysis of the decompacted and original sea-level reconstructions identified three trends. Compaction did not generate artificial sea-level trends and cannot be invoked as a causal mechanism for the features in the Tump Point record. The maximum relative contribution of compaction to reconstructed sea-level change was 12%. The decompacted sea-level record shows 1.71 mm yr − 1 of rise since AD 1845. [ABSTRACT FROM AUTHOR]

Micropaleontological, geophysical, and chronologic data indicate that normal salinity conditions occurred over currently estuarine back-barrier areas of the Outer Banks of eastern North Carolina during the peak of the Medieval Climate Anomaly. Sedimentary units several meters thick, containing foraminiferal assemblages usually found on the continental shelf of North Carolina, are present in 16 vibracores acquired from the shallow shoals of Pamlico Sound behind Cape Hatteras. Optically stimulated luminescence age estimates from these normal salinity units range from approximately 1360 to 980 calibrated years (cal yr) BP, corresponding with a previously documented collapse of a segment of the southern Outer Banks. It is vital to understand past scenarios of barrier island formation and segmentation to provide insight on how these islands may react to future change in climate and sea level. [ABSTRACT FROM AUTHOR]

Lithofacies analysis is fundamental to unravelling the succession of depositional environments associated with sea-level fluctuations. These successions and their timing are often poorly understood. This report defines lithofacies encountered within the north-eastern North Carolina and south-eastern Virginia Quaternary section, interprets their depositional environments, presents a model for coastal depositional sequence development in a passive margin setting and uses this understanding to develop the stratigraphy and Quaternary evolutionary history of the region. Data were obtained from numerous drill cores and outcrops. Chronology was based on age estimates acquired using optically stimulated luminescence, amino acid racemization, Uranium series and radiocarbon dating techniques. Geomorphic patterns were identified and interpreted using light detection and ranging imagery. Since lithofacies occurrence, distribution and stratigraphic patterns are different on interfluves than in palaeo-valleys, this study focused on interfluves to obtain a record of highstand sea-level cycles with minimal alteration by fluvial processes during subsequent lowstands. Nine primary lithofacies and four diagenetic facies were identified in outcrops and cores. The uppermost depositional sequence on interfluves exhibits an upward succession from shelly marine lithofacies to tidal estuarine lithofacies and is bounded below by a marine ravinement surface and above by the modern land surface. Older depositional sequences in the subsurface are typically bounded above and below by marine ravinement surfaces. Portions of seven depositional sequences were recognized and interpreted to represent deposition from late middle Pleistocene to present. Erosional processes associated with each successive depositional sequence removed portions of older depositional sequences. The stratigraphic record of the most recent sea-level highstands (Marine Isotope Stage 5a and Marine Isotope Stage 3) is best preserved. Glacio-isostatic adjustment has influenced depositional patterns so that deposits associated with late Quaternary sea-level highstands (Marine Isotope Stages 5c, 5a and 3), which did not reach as high as present sea-level according to equatorial eustatic records, are uplifted and emergent within the study area. [ABSTRACT FROM AUTHOR]

Abstract: Foraminiferal analyses of 404 contiguous samples, supported by diatom, lithologic, geochronologic and seismic data, reveal both rapid and gradual Holocene paleoenvironmental changes in an 8.21-m vibracore taken from southern Pamlico Sound, North Carolina. Data record initial flooding of a latest Pleistocene river drainage and the formation of an estuary 9000yr ago. Estuarine conditions were punctuated by two intervals of marine influence from approximately 4100 to 3700 and 1150 to 500calyr BP. Foraminiferal assemblages in the muddy sand facies that accumulated during these intervals contain many well-preserved benthic foraminiferal species, which occur today in open marine settings as deep as the mid shelf, and significant numbers of well-preserved planktonic foraminifera, some typical of Gulf Stream waters. We postulate that these marine-influenced units resulted from temporary destruction of the southern Outer Banks barrier islands by hurricanes. The second increase in marine influence is coeval with increased rate of sea-level rise and a peak in Atlantic tropical cyclone activity during the Medieval Climate Anomaly. This high-resolution analysis demonstrates the range of environmental variability and the rapidity of coastal change that can result from the interplay of changing climate, sea level and geomorphology in an estuarine setting. [Copyright &y& Elsevier]

Abstract: The Outer Banks barrier islands of North Carolina, USA, contain a geologic record of inlet activity that extends from ca. 2200calyr BP to the present, and can be used as a proxy for storm activity. Optically stimulated luminescence (OSL) dating (26 samples) of inlet-fill and flood tide delta deposits, recognized in cores and geophysical data, provides the basis for understanding the chronology of storm impacts and comparison to other paleoclimate proxy data. OSL ages of historical inlet fill compare favorably to historical documentation of inlet activity, providing confidence in the technique. Comparison suggests that the Medieval Warm Period (MWP) and Little Ice Age (LIA) were both characterized by elevated storm conditions as indicated by much greater inlet activity relative to today. Given present understanding of atmospheric circulation patterns and sea-surface temperatures during the MWP and LIA, we suggest that increased inlet activity during the MWP responded to intensified hurricane impacts, while elevated inlet activity during the LIA was in response to increased nor''easter activity. A general decrease in storminess at mid-latitudes in the North Atlantic over the last 300yr has allowed the system to evolve into a more continuous barrier with few inlets. [Copyright &y& Elsevier]

We compared the use of δ13C values and C:N ratios from salt-marsh sediments to reconstruct relative sea level (RSL) with an established approach using foraminifera. Analysis of bulk-organic sediment and plant samples collected along transects at two sites in North Carolina, USA demonstrates that sediment δ13C values can be used to distinguish between Spartina alterniflora-dominated low marsh (C4 photosynthetic pathway, δ13C values from -17.6‰ to 16.1‰) and Juncus roemerianus-dominated high marsh (C3 photosynthetic pathway, δ13C values from -28.2‰ to -21.8‰) environments. Juncus roemerianus plants undergo little decompositional change in δ13C (average 0.8‰), although there is a clear difference between Spartina alterniflora tissue and bulk-organic sediments (approximately 4‰). C:N ratios on bulk-organic sediment from freshwater upland and salt-marsh environments converge during early diagenesis, rendering them of little use in reconstructing RSL. The utility of δ13C values as a sea-level indicator is limited by the elevational range of C4 plants, making it difficult to recognize salt-marsh subenvironments and improve the precision of RSL reconstructions. Furthermore, Juncus roemerianus-dominated high marsh and freshwater upland sediments cannot be adequately distinguished with δ13C values. [ABSTRACT FROM AUTHOR]

Abstract: Foraminifera and diatoms preserved in salt-marsh sediments have been used to produce high-resolution records of Holocene relative sea-level (RSL) change. To determine which of these microfossil groups is most appropriate for this purpose we investigated their relative utility from salt marshes in North Carolina, USA. Regional-scale transfer functions were developed using foraminifera, diatoms and a combination of both (multi-proxy) from three salt marshes (Oregon Inlet, Currituck Barrier Island and Pea Island). We evaluated each approach on the basis of transfer-function performance. Foraminifera, diatoms and multi-proxy-based transfer functions all demonstrated a strong relationship between observed and predicted elevations (r 2 jack >0.74 and RMSEP<0.05 m), suggesting that they have equal utility. Application of the transfer functions to a fossil core from Salvo to reconstruct former sea levels enabled us to consider relative utility in light of ‘paleo-performance’. Fossil foraminifera had strong modern analogues, whilst diatoms had poor modern analogues making them unreliable. This result reflects the high diversity and site-specific distribution of modern diatoms. Consequently, we used foraminifera to reconstruct RSL change for the period since ∼AD 1800 using a 210Pb- and 14C-based chronology, and we were able to reconcile this with tide-gauge records. [Copyright &y& Elsevier]

We collected modern foraminiferal and environmental data from three back-barrier intertidal sites (Currituck Barrier Island, Oregon Inlet, and Pea Island) of the Outer Banks, North Carolina, United States, which have different salinity settings and a wind-driven tidal regime. The foraminiferal assemblages indicate that a vertical zonation of foraminifera occurs, with several significant site-specific variations of assemblages. The intertidal zone can be divided into two elements: first, an agglutinated assemblage that is restricted to the vegetated marsh and is dominated by Ammoboculites crossus, Ammobaculites subeotenulotus, Arenoporrello mexicana, Jadammine macrescens, Miliammina fusca, and Trochammina inflata and, second, a calcareous assemblage that dominates the mudflats and sandflats of the intertidal zone, characterized by Ammonia parkinsoniana, Elphidium excavatum, and Haynesina germanica. We used canonical correspondence analysis and partial canonical correspondence analyses of the foraminiferal and environmental data from the Outer Banks to support the hypothesis that the distribution of foraminifera in the intertidal zone is a direct function of elevation, with the duration and frequency of inundation as the most important factors. Partial canonical correspondence analyses and Monte Carlo permutation tests suggest that all available environmental variables except pH play a significant role in understanding the variations in foraminiferal data. [ABSTRACT FROM AUTHOR]

A comparison of two sections of the Outer Banks, North Carolina, USA (Pea Island and Avon-Buxton areas), reveals the importance of the interplay between oceanic and estuarine shoreline dynamics to long-term changes in barrier island width. From 1852 to 1998, the northern portion of Pea laland experienced an average net increase in width of 431 m (3 m/y); this area experienced low to moderate rates of oceanic shoreline erosion and high rates of back-barrier land accretion via overwash and formation of flood tidal delta islands. In contrast, between 1852 and 1998, the width of the southern portion of Pea Island and the Avon-Buxton area decreased an average of 515 m (4 m/y) and 594 m (4 m /y), respectively, because of high rates of oceanic shoreline erosion and variable changes in estuarine shoreline accretion and erosion. Net gain or net loss of barrier island width is strongly dependent on the natural depositional processes of overwash and flood tide delta formation. Anthropogenic modifications to the barrier island, such as construction of barrier dune ridges, planting of stabilizing vegetation, and urban development, can curtail or even eliminate the natural, self-sustaining processes of overwash and inlet dynamics. [ABSTRACT FROM AUTHOR]

A comparison of two sections of the Outer Banks, North Carolina, USA (Pea Island and Avon-Buxton areas), reveals the importance of the interplay between oceanic and estuarine shoreline dynamics to long-term changes in barrier island width. From 1852 to 1998, the northern portion of Pea Island experienced an average net increase in width of 431 m (3 m/y); this area experienced low to moderate rates of oceanic shoreline erosion and high rates of back-barrier land accretion via overwash and formation of flood tidal delta islands. In contrast, between 1852 and 1998, the width of the southern portion of Pea Island and the Avon-Buxton area decreased an average of 515 m (4 m/y) and 594 m (4 m/y), respectively, because of high rates of oceanic shoreline erosion and variable changes in estuarine shoreline accretion and erosion. Net gain or net loss of barrier island width is strongly dependent on the natural depositional processes of overwash and flood tide delta formation. Anthropogenic modifications to the barrier island, such as construction of barrier dune ridges, planting of stabilizing vegetation, and urban development, can curtail or even eliminate the natural, self-sustaining processes of overwash and inlet dynamics. [ABSTRACT FROM AUTHOR]

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. [Copyright &y& Elsevier]

Foraminiferal and sedimentary data, supplemented with geochemical dating and ground-penetrating radar transects, show that the barrier island at Pea Island National Wildlife Refuge just north of Rodanthe, North Carolina, has been dominated by a combination of inlet and overwash processes for at least 1000 years. The stratigraphic record of several vibracores does not preserve every, or even many, overwash events but, instead, is characterized by three to four fining-upward sequences. The last three commence with overwash sand or gravel that is overlain by a variety of finer-grained estuarine, inlet, and marsh deposits. The dynamic nature of this segment of the Outer Banks was muted in the late 1930s by construction of artificial barrier dune ridges, extensive planting of grass and shrubs, and construction of Highway 12 in 1953. Subsequently, the road and barrier dune ridge were rebuilt and relocated several times following storm events. [ABSTRACT FROM AUTHOR]

Tests the validity of generalization on the relationship between species distribution-abundance-occurrence and species duration for benthic foraminifera. Representation of time slices in the Salisbury and Alberale embayments; Temporal components of fauna within time slices; Statistical analyses of data by time slice; Statistical analyses of modern foraminifera; Significance of the OX temporal component.

Summary The distribution of benthic foraminifera around the continental margins of North America is extensively documented. Data from 2673 localities consists of a synonomized list of 2329 species (S) and 61 369 occurrences (n). Here, the margins are divided into five geographical regions: Pacific (PA), S =965, n=19 014; Arctic (AR), S=458, n=7342; Atlantic (AT), S=878, n=10 034; Gulf of Mexico (GM), S=849, n=18 011; Caribbean (CR), S=1188, N=6968. As for many other organisms, species richness is lowest in the Arctic and highest in the Caribbean. In each region, the distribution of species richness and occurrences is a log series. Consequently, the entire series of species occurrences is predicted by the single proportionality constant, α. After log series rarefaction, differences in species richness among areas are nearly all accounted for by species occurring ≤10 times. Most of the differences are accounted for by species occurring once, less by twice, and so on. For example, species occurring once account for 81% of the difference in species richness between the Atlantic and Caribbean, and those occurring once and twice account for 87% of the difference. Most rare species have no fossil record and most endemic species are rare. Probably most of these species evolved recently indicating more origination in species-rich areas. High origination might also be coupled with less extinction. Although each of the five regions can easily be distinguished by differences in composition, in all regions the 10 most abundantly occurring species exhibit nearly equal proportions of occurrences. No region is dominated by only one or two species. All regions exhibit the log series distribution, have nearly equal proportions for abundant species, and differ only in the number of rare species that coexist. Thus, from the point of view of the distribution of occurrences, the most striking aspect is the similarity among regions. [ABSTRACT FROM AUTHOR]

Analyzes the species diversity and dispersal of benthic foraminifera. Suitability of foraminifera for examining the distribution of species in space and time; Similarity of species diversity patterns between benthic foraminifera and marine macroinvertebrates; Observation of the increase of species diversity from high to low latitudes; Distributional data; Species occurrence and diversity.

Studies the burrows and trails produced by Quinqueloculina impressa Reuss, a benthic foraminifer, in fine-grained sediment. Assessment of the capability of the benthic foraminifer Quinqueloculina impressa Reuss for producing sediment disturbances and ichnofossils; Distinct burrows in silts and silty-clays; Types of burrows.