Barrier Coastline Research Articles

Application of geomorphological maps and LiDAR to volumetrically measure coastal geomorphological change from Hurricane Sandy at Fire Island National Seashore

The geomorphological map offers a snapshot of the landforms generated through topographical response to physical process drivers within a given landscape. A comparison of geomorphological maps with consistently and objectively identified landform boundaries allows for the assessment of spatiotemporal variations in process-response dynamics that represent the fundamental nature of geomorphological evolution, and form a basis to derive quantitative metrics of landform development. Two geomorphological maps of Fire Island National Seashore created from LiDAR datasets and orthophotography collected prior to and immediately following Hurricane Sandy were compared according to consistent and objective criteria. The mapped geomorphology and the LiDAR elevation data facilitated the use of regional-residual separation methods to assign sediment volumes to specific processes and landforms. This led to the calculation of sediment volumes deposited as beaches, foredunes, and washover deposits before and after the storm and to the quantification of the changes associated with the storm across the entire 50 km stretch of barrier coastline that comprises Fire Island. The temporal comparisons indicated that different portions of Fire Island exhibited variable geomorphological responses to a major storm. Notably, the central and western portion of the island, from 6 km to 36 km from the mouth of Fire Island Inlet, experienced substantial losses to coastal dunes — on the order of 2.9 × 106 m3 of sediment. The beaches in this segment of the coastline gained volume (~86,000 m3) in the storm indicating that the dunes provided a source of sediment to the beach, both buffering erosion and supplying sand to the littoral system. The eastern third of the island experienced beach erosion (~540,000 m3) and erosion of the dunes (~350,000 m3), as well as a significant amount of overwash deposition (~250,000 m3) that represents a transfer of sediment from the beach/dune reservoir to the backbarrier. This mode of geomorphological evolution adds elevation to the backbarrier at the expense of sediment available to buffer the shoreline position. Two 6 km strecthes of Fire Island coastline, Bellport/Old Inlet and Talisman/Watch Hill, exemplify the geomorphological response of the eastern and central potions of the island to the impact of Hurricane Sandy: 1) at Bellport/Old Inlet, overwash deposition was partially sourced from beach deposits adding elevation to the backbarrier at the expense of the shoreline position; and 2) at Talisman/Watch Hill, sediment stored in dune systems was transferred to the beach to slow storm induced shoreline retreat, and the dune buffer and its associated resilience was reduced.In quantifying the system response of a barrier island to a major storm event like Hurricane Sandy, we demonstrate the feasibility and utility of deriving metrics of geomorphological change from geomorphological maps. This approach of quantifying process-response outcomes through mapping is broadly applicable to a variety of geomorphological settings and timescales given a consistent means of boundary determination and using regional-residual separation.

Modelling gravel barrier response to storms and sudden relative sea-level change using XBeach-G

This paper investigates the response of a mixed sand and gravel (MSG) barrier coastline to storms and sudden relative sea-level change using the numerical model XBeach-G. The barrier beaches of southern Hawke's Bay, New Zealand provide a natural laboratory for the work owing to spatial variability in instantaneous land deformation that occurred during the 1931 Hawke's Bay earthquake. Historic (1931) and contemporary (2017) morphodynamics of one tectonically uplifted (+1.5 m) and one subsided (−0.78 m) barrier were modelled under energetic waves (Hs 1–6 m). XBeach-G was designed to simulate pure gravel beach morphodynamics, but despite this, the model demonstrated high quantitative skill when calibrated for the MSG coast. Results reveal the storm impact regimes of each profile and potential linkages to decadal-scale barrier development observed in historical beach profile data. Storm-swash processes at the uplifted profile indicate long-term barrier stability due to a lack of change at the barrier crest, and ridge building observed in model simulations provides a potential formative mechanism for decadal-scale beach progradation. At the subsided barrier, modelled historic crest build-up (up to 0.3 m) and narrowing (over 5 m) indicate an overtopping mode of response to sudden relative sea-level rise. Simulation results are consistent with historical beach profile observations that also show chronic narrowing of the subsided barrier through time. Simulations of the modern barrier draw attention to the possibility that it may be on a trajectory toward catastrophic breakdown under extreme conditions, but further work is needed to distinguish the relative importance of historical sudden sea-level rise versus deficits in sediment supply to this shoreline.

Regional coastal flood risk assessment for a tidally dominant, natural coastal setting: North Norfolk, southern North Sea

A Coastal Risk Assessment Framework (CRAF) provides two levels of coastal risk and vulnerability assessment, by combining information on the spatially variable hazard and exposure. In Phase 1, areas of greatest risk or ‘hotspots’ are identified. In Phase 2, these hotspots are then analysed in greater detail to identify both direct and indirect extreme event impacts. This approach was applied to the barrier coastline of North Norfolk, eastern England. The CRAF identified high risk coastal hotspots on the basis of both hazard impacts (swash regime (tide + surge + wave runup) and overwash/terrestrial inundation regimes) from a 1 in 115 year return period storm and a range of land use, infrastructure, economic and social vulnerability indicators. Hazard extents and hazard severity, in some locations modified by the presence of intertidal saltmarsh, were calculated for 45, 1–2 km wide sections along the topographically complex coast. When combined with five exposure indicators, eight hotspots were identified along the 45 km long frontage. In a 2nd phase, two of these hotspots, one a chain of small villages (Brancaster/Brancaster Staithe/Burnham Deepdale) and one a small town (Wells-next-the-Sea), were compared in more detail using a suite of coastal inundation and impact assessment models to determine both direct and indirect impacts. Hazards at this higher resolution were calculated using the 1D process-based XBeach model and the 2D LISFLOOD inundation model. Vulnerability to the hazards was calculated using the INDRA (Integrated Disruption Assessment) model with comparison of the two hotspots through the use of a Multi Criteria Analysis (MCA). The selection of hazard hotspots and comparison of hotspots using these techniques allows areas at greatest risk to be identified, of vital importance for coastal management and resource allocation.

Storm impacts and shoreline recovery: Mechanisms and controls in the southern North Sea

Storm impacts play a significant role in shoreline dynamics on barrier coastlines. Furthermore, inter-storm recovery is a key parameter determining long-term coastal resilience to climate change, storminess variability and sea level rise. Over the last decade, four extreme storms, with strong energetic waves and high still water levels resulting from high spring tides and large skew surge residuals, have impacted the shoreline of the southern North Sea. The 5th December 2013 storm, with the highest run-up levels recorded in the last 60years, resulted in large sections of the frontline of the North Norfolk coast being translated inland by over 10m. Storms in March and November 2007 also generated barrier scarping and shoreline retreat, although not on the scale of 2013. Between 2008 and 2013, a calm period, recovery dominated barrier position and elevation but was spatially differentiated alongshore. For one study area, Scolt Head Island, no recovery was seen; this section of the coast is being reset episodically landwards during storms. By contrast, the study area at Holkham Bay showed considerable recovery between 2008 and 2013, with barrier sections developing seaward through foredune recovery. The third study area, Brancaster Bay, showed partial recovery in barrier location and elevation. Results suggest that recovery is promoted by high sediment supply and onshore intertidal bar migration, at rates of 40ma−1. These processes bring sand to elevations where substrate drying enables aeolian processes to entrain and transport sand from upper foreshores to foredunes. We identify three potential sediment transport pathways that create a region of positive diffusivity at Holkham Bay. During calm periods, a general westward movement of sediment from the drift divide at Sheringham sources the intertidal bar and foredune development at Holkham Bay. However, during and following storms the drift switches to eastward, not only on the beach itself but also below the –7m isobath. Sediment from the eroding barrier at Brancaster Bay, and especially Scolt Head Island, also sources the sediment sink of Holkham Bay. Knowledge of foredune growth and barrier recovery in natural systems are vital aspects of future coastal management planning with accelerated sea-level rise and storminess variability.

Major coastal impact induced by a 1000-year storm event

Extreme storms and storm surges may induce major changes along sandy barrier coastlines, potentially causing substantial environmental and economic damage. We show that the most destructive storm (the 1634 AD storm) documented for the northern Wadden Sea within the last thousand years both caused permanent barrier breaching and initiated accumulation of up to several metres of marine sand. An aggradational storm shoal and a prograding shoreface sand unit having thicknesses of up to 8 m and 5 m respectively were deposited as a result of the storm and during the subsequent 30 to 40 years long healing phase, on the eroded shoreface. Our results demonstrate that millennial-scale storms can induce large-scale and long-term changes on barrier coastlines and shorefaces, and that coastal changes assumed to take place over centuries or even millennia may occur in association with and be triggered by a single extreme storm event.

The global Mio–Pliocene climatic equability and coastal ostracod faunas of southeast Australia

This study on the Mio–Pliocene ostracod successions of southeast Australia outlines several faunal events indicative of climate warming and/or increased rainfall events. Ostracod faunas associated with a late Late Miocene sea level rise event suggest that the climate of this time in southeast Australia was similar to, or slightly warmer than that of present day southeast Australia. However, it was probably wetter and significantly warmer than immediately preceding (mid Late Miocene) palaeoclimatic conditions within the region. Evidence for a change to wetter and warmer conditions during the late Late Miocene is seen in the appearance of various extant euryhaline and semi-thermophilic ostracod species in coastal ostracod faunas. The appearance of euryhaline species, which are mostly absent from older shallow marine Cenozoic strata of the Bass Strait hinterland, suggests a major influx of fresh water into coastal marine settings, which contributed to the initial phase of development of the southeast Australian late Neogene barrier coastline and associated marginal marine palaeoenvironments. During the time interval latest Miocene to earliest Pliocene, and during the early Late Pliocene, two subsequent global sea level rise events are also preserved in the southeast Australian coastal plain. Many of the species present in ostracod faunas associated with these two events are the same as in older local late Late Miocene faunas. In earliest (?) Pliocene faunas, there is minor evidence for the reappearance of semi-thermophilic ostracods. Faunas of early Late Pliocene age often exhibit a conspicuous faunal dominance by, or large abundance of euryhaline species, indicating the particularly strong influence of fresh water influxes into coastal marine palaeoenvironments. This may reflect the presence of especially wet local temperate palaeoclimatic conditions during a time of equable global climates. Succeeding estuarine, lagoonal and coastal embayment ostracod faunas of late Late Pliocene age are associated with marginal marine sediments that are interbedded with coastal dune aeolianites. This suggests an overall seaward retreat of marginal marine environments that was initiated by a major global sea level fall linked to the onset of cooler Late Pliocene and Quaternary global climates.

Sedimentary evolution of the north Norfolk barrier coastline in the context of Holocene sea-level change

Abstract Holocene sediments of the north Norfolk coast (NNC) between Weybourne and Hunstanton have been studied using geophysical, sedimentological, biofacial and dating techniques. New cores and refraction seismic data have defined the topography of the pre-Holocene surface and show that the NNC sediment prism is underlain by an east-west trending Quaternary trough, probably a palaeo-river-valley. The age of the Holocene fill has been dated using radiocarbon and luminescence dates, while sedimentation rates were constrained by, and compared with, modern rates using radionuclide data. The Holocene sediments are divided into a sandy-barrier lithofacies association (LFA), and a muddy-silty-peat back-barrier LFA. The oldest Holocene sediments are peats, formed on an undulating till surface. These peats were forming by 11-10 cal. ka bp and continued to form until at least 7 cal. ka bp in a number of places. As Holocene sea-level rose, marine mudflat and saltmarsh environments began to form between 7 and 6 cal. ka bp east of Holkham and around 6 cal. ka bp or younger west of Holkham. A marked erosion surface between the barrier and back-barrier LFA in the Holkham to Burnham Overy area is imperfectly dated at <3 cal. ka bp , but suggests the sediment prism has thinned by about 3 km over 6 to c . 3cal. ka bp . This surface probably records the westward progress of laterally migrating tidal channels that caused back-barrier sediment erosion, along with shoreface processes, as sea-level rose. Small-scale regressive and transgressive saltmarsh sequences occur at different elevations along strike but cannot be correlated, suggesting that the control on saltmarsh and mudflat development is autocyclic rather than allocyclic. Generally, transgressive and regressive events are related to disposition of coastal barriers and these are superimposed on a general facies evolution governed by regional sea-level change. Predictions about how this barrier coastline might respond to increased rates of regional sea-level change caused by global warming, or climatic events like increased storminess, require an understanding of how specific segments of the coastline have responded over millennial time-scales. This longer-term evolution provides the baseline information for decision making and management strategy. It is likely that sandy sediment supply is limited on the NNC and this implies that the barriers will continue to move landward, probably at increased rates relative to today, suggesting that parts of the NNC will become more vulnerable to erosion and flooding.

Classification of paraglacial barrier systems: coastal New England, USA

The New England coast harbours a wide variety of barrier forms, which we organize into six barrier‐coastline types. The barriers develop in response to the relative importance of several spatially and temporally variable parameters, particularly antecedent topography and geology, sediment abundance and size, exposure to wave and tidal energy and sea‐level history. The six coastline types can also be identified in other paraglacial regions. Existing barrier‐coastline classification schemes do not allow consistent subdivision of paraglacial barrier coasts. This paper presents a new scheme that is applicable to paraglacial and non‐paraglacial barrier coasts alike. Aside from hydrodynamic regime, which forms the basis of the barrier classification most commonly used to date, it includes a compartmentalization factor. Sediment‐starved ‘isolated’ (‘type 1’) barrier coastlines are characterized by short, widely spaced barriers. Small, localized updrift and offshore sources have provided sediment for short barriers along ‘clustered headland‐separated’ (‘type 2’) barrier coastlines. Various amounts of sediment from larger updrift and offshore glaciofluvial deposits or directly from rivers have formed the longer barriers along ‘wave‐dominated mainland‐segmented’ (‘type 3a’), ‘mixed‐energy mainland‐segmented’ (‘type 3b’), ‘wave‐dominated inlet‐segmented’ (‘type 4a’) and ‘mixed‐energy inlet‐segmented’ (‘type 4b’) barrier coastlines. Geomorphic form, grain size and stratigraphy can be used to characterize individual barriers along barrier coastlines. Most paraglacial barriers form as spits, but many are transformed subsequently. Welded barriers are common along ‘type 1’ and ‘type 2’ coasts. Baymouth barriers are characteristic of ‘type 3’ coasts, and barrier islands occur exclusively along ‘type 4’ coasts. The coarsest grained barriers are located along ‘type 1’ and ‘type 2’ coasts. Progradational barrier sections are concentrated along ‘type 3’ and ‘type 4’ coasts with abundant sediment supply, but are also present along ‘type 2’ coasts. Temporary increases in sediment supply, common in paraglacial regions, result in transitions between retrogradational and progradational barrier behaviour, which may be recognized on shore‐perpendicular stratigraphic cross‐sections.

Geomorphic response-type model for barrier coastlines: a regional perspective

Based on quantitative documentation of historical changes in shoreline position between 1847 and 1991, eight geomorphic response-types were established for classifying megascale changes along barrier coastlines: (1) lateral movement, (2) advance, (3) dynamic equilibrium, (4) retreat, (5) in-place narrowing, (6) landward rollover, (7) breakup, and (8) rotational instability. Long-term (decades to centuries) monitoring of shoreline position over a spatial scale of 10 to 100 km provides a scientific basis for documenting process-response relationships that shape regional coastal morphodynamics. Although megascale shoreline change studies often are lacking, this type of information is critical for developing realistic research and management strategies regarding form/process relationships in coastal depositional systems. The spatial distribution of geomorphic response-types is delineated along the barrier coastlines of Louisiana, Mississippi, and southern Georgia/northern Florida. At megascale, the rate of relative sea level rise along these barrier coastlines appears to be one of the major factors controlling the occurrence of geomorphic response-types; however, sediment supply exerts significant influence on shoreline response as well.

Clastic Sequences Developed During Glacio-Eustatic Sea Level Fluctuations on a Sandy Barrier Coastline: ABSTRACT

Seismic reflection (Geopulse) profiles from a 125 km{sup 2} grid on the New Jersey low-mesotidal sandy barrier coastline reveal a 30-m sediment thickness composed of three unconformity bounded parasequences. Vibracores from 12 sites reveal a variety of depositional environments that existed during the most recent glacio-eustatic sea level fluctuations on this stable passive margin. Environments include fluvial, during glacial lowstands; barrier islands with back-barrier lagoons and pro-barrier ebb tidal deltas and shore-attached ridges; and below storm-wave base shelves during interglacial highstands. Following the last major interglacial (Sangamon, {approx} 125KA), sea level fell and rivers eroded a planar seaward dipping surface by the early Wisconsinan time ({approx}70KA). As sea level rose during the mid-Wisconsinan ({approx} 50KA), a barrier island shoreline migrated to within 0.2-1.7 km of the modern shoreline. Maximum highstand of mid Wisconsinan sea level was 20 m below present. Sea level fell again during the late Wisconsinan ({approx}20KA). A barrier island/lagoonal system developed under rising sea level at least by the early middle Holocene based on peats (8,800 BP) in lagoonal muds cored from {minus}12 m. The root of the mid-Wisconsinan barrier system was preserved under early Holocene transgressive sediments. The modern coastal and inner continental shelf deposits aremore » relatively thin (3-4 m) pebbly sands overlying a prominent ravinement surface unconformity formed during the Holocene sea level rise. Isopach maps constructed for this surface indicate up to 7 m of relief eroded into muds beneath the ebb tidal delta and the shore-attached ridges. The ridges and delta shielded the underlying fine sediments during sea level rise. Based on a reasonable Atlantic shoreline transgression rate of 2 m/yr, the modern Barnegat Inlet ebb tidal delta has existed in its general location for at least 800 years.« less

Coal reviewed: depositional controls, modern analogues and ancient climates

Summary Ancient economic coals usually contain more than 90% organic matter and less than 1% sulphur. Sedimentological reconstructions show the interbedded clastics to be fluvial-plain, deltaic, barrier coastline, estuarine or alluvial-fan deposits. However, bases of coal beds unconformably transgress these various facies, and coals only rarely pass laterally into clastic facies. Thus coal-forming peats post-dated the underlying clastic sedimentation and most coals did not form in deltas. Local coal thicknesses can be controlled by compaction of underlying sediment, syndepositional faulting, or basement structure. Coals with more than 1%–2% sulphur are usually overlain within 10 m by marine sediments which provided SO 4 2− by diffusion. However, most coals contain less sulphur and must be freshwater in origin. Lithotype and spore profiles vertically through coals indicate a characteristic change of peat floras. This resulted from equisites-dominated seat earths, followed by diverse tree-sized vegetation which formed bright coal and lastly by low diversity stunted vegetation which formed dull coal. These features compare well with peats formed in modern ombrogenous blanket or raised bogs. The ancient mires formed in rainwaters (low sulphur), excluded clastic sediments (low ash), had a lateral floral zonation, usually post-dated clastic deposition and occurred inland from the shoreline. Modern ombrogenous mires are abundant, especially in humid temperate climates. These peats are forming today during a period of long-term climatic cooling in areas with a frequent reliable rainfall. Ancient coals may also have formed during long-term climatic cooling epochs when volcanic CO 2 was being removed from the atmosphere. This could be regarded as a Gaian biosphere maintaining Earth temperatures similar to those of the present day.

Washover of Deltaic Barriers on Louisiana Coast: ABSTRACT

Washover processes are an important factor in the transgressive development of barrier coastlines. Sea level elevation necessary for overwash is composed of a storm surge component, a wave setup component, a wave runup component, and an astronomical tide component. The nature and severity of overwash are a function of overwash elevation, its frequency of occurrence, and regional barrier geometry. Washover deposits on Louisiana barriers commonly account for over 50% of total sediment storage. Louisiana barriers have evolved by deltaic distributary abandonment; continuing sequential evolution of Mississippi delta complexes has generated a corresponding sequence of transgressive barriers. The resulting spectrum of barrier geometries has provided an ideal field site for the examination of washover form variability and its controlling processes. End_of_Article - Last_Page 1682------------

Post-Pleistocene history of the United States inner continental shelf: Significance to origin of barrier islands

Segments of the U.S. Atlantic coast differ markedly in shoreline and shelf configuration because of both geologic setting and Quaternary geologic history. Regional trends in shelf structure, sediment sources, and history correlate with regional trends in adjacent shoreline configuration, and the Holocene transgressive history of the shelf has a direct bearing on the evolution of the present coastline. The shelf sedimentary record, particularly in the mid-Atlantic region, contains substantive evidence that precursors to existing barrier islands were common in Holocene time. Nearshore linear shoals are associated with barrier-island coastlines, and their continuity in position on the shelf, coupled with the presence of an underlying lagoonal substrate, implies persistent retreat of a barrier coastline during sea-level rise. Retreat paths of shoals off large capes and estuaries similarly indicate a consistency in shoreline type and orientation through time. Collectively, this information strongly suggests that barrier islands of the U.S. Atlantic coast originated far out on the shelf, and it invalidates certain criteria (coastal linearity, lithology of sediments beneath the modern lagoon) formerly cited as evidence for mode of formation. Understanding how and the processes by which barriers evolved relate directly to present and future behavior of barriers. Sediments eroded from the foreshore and shoreface are transported both along the coast and landward, aggrading as nearshore shoals, spits, tidal deltas, dunes, and overwash fans. Barrier islands lengthen both by sand accumulation (spit extension) and by submergence (deepening and headward extension of the lagoon). Development of barrier islands is influenced by rate of sea-level advance and sediment supply. Once initiated, barrier islands lengthen and retrograde through a combination of processes, including spit elongation, overwash, and flooding of back barrier lagoons.

Criteria for Recognizing Ancient Barrier Coastlines: ABSTRACT

Worldwide modern barrier coastlines constitute a minor part of the total coastlines of all the continents. The aggregate length of present barrier coastlines in the world is approximately 3,530 mi, distributed as follows: North America, 2,000 mi; Europe, 500 mi; South America, 350 mi; Africa, 300 mi; Australia, 200 mi; and Asia, 200 mi. Barrier islands commonly border coastal plains adjacent to broad continental shelves. They form in areas of abundant sand accumulation where longshore currents are prominent. Sandstone lenses which represent ancient barrier islands would be expected in thick wedges of interfingering terrestrial and marine sandstone, siltstone, and mudstone. Barrier islands of Pleistocene age have been recognized inshore from present End_Page 706------------------------------ coastlines, and drowned Holocene barrier coastline features have been described on the continental shelves. Pre-Holocene linear sandstone bodies resembling barrier islands have been described in ancient rocks of Pennsylvanian, Cretaceous, and Tertiary ages. Probable barrier island sandstone bodies in ancient rocks have been described by previous investigators on the basis of comparison with features of modern analogs: geometry, sedimentary structures within the sand lens, physical properties of the sand, and the nature of associated environments. Recognition criteria used in this report are based partly on previous work and partly on recent studies along the Texas and North Carolina coasts. Barrier islands are linear, have a length to width ratio generally greater than 10:1 and commonly are less than 60 ft thick. Padre Island, Texas, consists of four morphological units that have characteristic sedimentary structures: beach, foredune, barrier flats, and wind tidal flats--though the development of the foredunes and wind tidal flats changes considerably from north to south. Along the North Carolina coast, wind tidal flats are absent, but accretionary beach ridges are locally prominent. Superimposed on the islands of both coasts are storm washovers of hurricane origin that breach the foredunes and channel inlets that cross the island and connect the sea with the lagoon behind the islands. Beaches contain laminae of different thicknesses that dip principally seaward; the san is locally shelly and fine laminae of heavy minerals may be prominent. The foredunes are markedly cross-bedded in an oriented pattern that reflects strongly the predominant wind direction. Barrier flats are underlain by sand which ranges from structureless to highly laminated; vegetal remains are common. Wind tidal-flat sediments that border the lagoon are an interlayered mixture of sand beds containing some fine shell fragments, and laminae of clay and algal remains. Sand is fine grained throughout. However, shell fragments, locally abundant, exhibit greater variability in size, shape, and sorting. Sand which refills channel inlets ranges from horizontally bedded to structureless; this contrasts sharply with the cut-and-fill cross-bedded sand common in stream-channel deposits. The associated lagoon sediments are organic and calcareous mud which interfingers with barrier-island sand; the fauna is less diverse than that of the open sea and unbroken shells are abundant. Tongues of sand--washover deltas and fans which are built by storm flood tides--are prominent local features of the lagoons. Marshes overlying peat are characteristic of the inshore side of the bays along the North Carolina coast. The geometry and alignment of the barrier islands and the close association of the sand in the barrier island with the organic mud of the lagoon are the key factors for the recognition of a barrier coastline. Attendant washover deltas and fans, cross-cutting inlet fill, and associated biota are important supplementary aids. End_of_Article - Last_Page 707------------

The Significance and Limitations of Statistical Parameters for Distinguishing Ancient and Modern Sedimentary Environments of the Lower Georgia Coastal Plain

ABSTRACT The lower Coastal Plain of Georgia is considered to be a significant area for the study of preserved coastline sediments because ancient deposits are generally well preserved and provide a comprehensive record of the geomorphological and sedimentological history of the region. Samples have been collected from six Pleistocene barrier coastlines and the Holocene coast in an attempt to evaluate the significance and limitations of statistical parameters for distinguishing ancient and modern sedimentary environments. The sediments of each barrier coastline can be subdivided into lagoon-salt marsh and barrier-island facies. The former include estuarine and tidal channel sediments whereas the barrier facies also include dune, littoral, shallow neritic and offshore channel deposits. Barrier island sands are better sorted than those from lagoon-salt marsh environments although all samples have mean grain size values higher than 1.50. The coarsest sediments in the barrier island environments are found in the tidal inlets and channels, and about 70 percent of the samples are negatively skewed. Diagenesis possibly accounts for a small percentage of positively skewed Pleistocene barrier island sands. About 30 percent of the lagoon-salt marsh sands are positively skewed. More than 90 percent of the Holocene beach sands are negatively skewed, but about 70 percent of the dune sands show positive skewness. The sign of skewness in this study is related to energy variations in different sedimentary environments, despite the fact that investigations of paleoenvironments in general can present interpretative problems.