Washover Sands Research Articles

Can 210Pb be used as a paleo-storm proxy?

There is increasing interest within the scientific community, as well as the public, to determine if tropical cyclones are increasing in frequency and/or magnitude because of climate change. Unfortunately, the instrumental weather record only extends over the last 100–150 years depending upon location. It is thus desirable to develop paleo-storm proxies to extend the tropical cyclone record to hundreds, if not thousands, of years. Overwash sand deposits, sediment grain size, and various geochemical parameters (e.g., δ13C, δ15N, C/N) have been applied successfully for coastal lake sediments. We present here another potential proxy candidate, the natural radionuclide 210Pb. With a 22.2-year half-life, 210Pb age dating is often used to calibrate other proxies over essentially the same period as the instrumental storm record. We hypothesize here that trends in the 210Pb profiles, in addition to providing chronological information, can provide independent records of storm deposits in some situations. To illustrate how 210Pb may serve as an additional storm proxy, we present data from sediment cores collected from the Chao Phraya Delta (Upper Gulf of Thailand), an area characterized by a rapidly retreating shoreline. Some of the 210Pb profiles mark sedimentary layers with anomalously low excess 210Pb activities interspersed between layers with significant excess activities. We suggest that these layers may result from rapid deposition offshore of older storm-eroded shoreline material. The estimated ages of these 210Pb-deficient layers match, within estimated uncertainties, years when typhoons or tropical storms are reported to have severely eroded the nearby Thai coastline. The matching of the time scales of 210Pb and recorded tropical cyclones, both about 100–150 years, allows this approach to be used to explore for storm deposits and tune geochemical and other proxies for extended study over time scales of several decades or longer.

Occurrence mode of Holocene tsunami overwash controlled by the geomorphic development along the eastern Nankai Trough, central Japan

Re-analysis of the lithological, paleontological, and geochemical data of three lagoonal sediment cores reveal the tsunami overwash history from 8000 to 6500 cal BP along the northern Suruga Bay coast, facing the eastern Nankai Trough. The coring sites are located in a transcect 0.8, 1.5, and 1.7 km inland, respectively, from the coastline at the time the overwash events occurred. The washover sand beds are distinguished from the lagoonal muds by the presence of quartz and mica, which are abundant on the outer (marine) side of the lagoon, as well as marine shell fossils. The increased C/S ratio often associated with sand beds, reflects input of open seawater to the reductive lagoon, and supports this interpretation. A maximum of eight tsunami deposits were identified between ∼7800 and 6500 cal BP, many of which can be correlated between the three cores. The magnitude of tsunami overwash implied by the thickness and grain size of tsunami deposits, and increase of C/S ratio following their deposition is relatively large at ∼7500-7200 cal BP during the post-glacial sea level rise and decreases with time during the subsequent high sea level stand. This occurrence mode (timing and scale of formation) of tsunami washover is explained by temporal changes in coastal geomorphology, rather than differences in the magnitude of individual tsunamis. Around 7500-7200 cal BP, sea level rise equilibrated with or exceeded the growth of the bay mouth barrier, and tsunamis could easily cross the small barrier and enter the lagoon, leaving behind thick and coarse-grained deposits. As the barrier becomes larger during the subsequent sea-level highstand, only the highest-amplitude waves exceeded the height of the barrier. By ∼6500 years ago, the barrier was high enough to prevent tsunamis from entering the lagoon. Similarly, the occurrence mode of tsunami deposits reported along the coast of Suruga Bay and Enshu-nada over the past 6000 years can be explained in relation to the growth of coastal barriers.

Environmental DNA signatures distinguish between tsunami and storm deposition in overwash sand

Sandy onshore deposits from tsunamis are difficult to distinguish from storm deposits, which makes it difficult to assess coastal hazards from the geological record. Here we analyse environmental DNA from microbial communities preserved in known tsunami and storm-deposited sediments and intercalating soils and non-marine sediments near Cuddalore, India, and Phra Thong Island, Thailand. Both sites were impacted by the 2004 Indian Ocean Tsunami and a subsequent storm flooding event (2011 Cyclone Thane at Cuddalore and a 2007 storm at Phra Thong Island). We show that the microbial communities in the overwash deposits are significantly different from soil and sediments that are not derived by overwash processes at both locations. Our method also successfully discriminates between modern tsunami deposits and storm deposits. We suggest molecular techniques have the potential to accurately discriminate overwash deposits from catastrophic natural events.

Sandy coast erosion under the conditions of a storm surge combined with a spring tide

By comparing the changes of beaches and features in the southeastern coast of Xiamen Island before and after Typhoon No. 9914, the beach cycle and coast erosion processes under the condition of superimposed the spring tide of storm surge were discussed. The study showed that during Typhoon No. 9914, the coastal water level rose to 4.04m above the main sea level (MSL). The storm surge elevation was 1.43m. The stormy waves with 22m/s onshore winds brought overwash onto Huandao Road, up to the main sea level of more than 8.5m, depositing about 8-10cm of beach sands on the road. It caused the beach berm to disappear completely. The sand prism lying in the high tidal zone was scoured. Part of the sand of the prism was washed upward away from the beach, part of which was brought to the low tide zone. The bare shoreface without sand prism was scoured directly by waves and currents. Although the sandy sediment which was brought to the deeper zone by the storm can come back to the shoreface, but the overwash sand could not be returned after the storm, and the prime failed to return to its original condition for a long time, eventually leading to beach erosion and coast retreat.

Hurricane Harvey Storm Sedimentation in the San Bernard National Wildlife Refuge, Texas: Fluvial Versus Storm Surge Deposition

Few studies have documented the characteristics of fluvial flooding-induced storm deposits associated with a modern hurricane. Hurricane Harvey (2017) caused extensive flooding in coastal Texas due to a combination of storm surge and heavy precipitation. This study investigates the depositional process associated with Hurricane Harvey by means of loss-on-ignition (LOI) and X-ray fluorescence (XRF) analyses of 9 short cores and 17 surface samples collected from the San Bernard National Wildlife Refuge (SBNWR), Texas. Hurricane Harvey caused the largest flood within SBNWR over the last 28 years, and freshwater flooding from the San Bernard River was the predominant cause of this inundation. A distinct washover sand layer is lacking at all coring sites, but the intrusion of seawater can still be detected by a peak in the chlorine/bromine (Cl/Br) ratio of most sediment cores. Our study shows that Cl/Br ratios are higher in coastal environments than in terrestrial environments, thereby confirming that this elemental ratio can be used as a salinity indicator and, as a corollary, evidence of marine intrusion into lower-salinity environments. The ensuing phase of freshwater flooding and fluvial sedimentation is represented by a distinct flood deposit in only three cores, but is absent or indistinct in most cores. The elusiveness of the Harvey fluvial flood deposit can be explained by the relatively low discharge and suspended sediment load of the San Bernard River, the uneven distribution of this event deposit, and its indistinctiveness with the underlying deposits laid down by previous flood events.

Identifying possible tsunami deposits on the Shizuoka Plain, Japan and their correlation with earthquake activity over the past 4000 years

Three washover sand beds, ranging from 15 to 34 cm in thickness, were recorded in a lagoonal mud sequence on the Shizuoka coast of central Japan, which faces the Suruga Trough. The sand beds were composed of well-sorted and well-rounded beach sand derived by a marine inundation. The basal erosion surface, mud clasts, and presence of both inverse and normal grading suggest that the sand beds formed as a result of high-energy deposition. The sand beds are multilayered, with fine alternations of sand sheets and mud drapes, which are consistent with deposition from a long-period wave train. Radiocarbon dates obtained from the three washover deposits are around ad 1000, 3565–3486 cal. yr BP, and 4000 cal. yr BP. Vertical changes in the diatom assemblages suggest a gradually increasing inflow of seawater up to the second sand bed, followed by a rapid change to freshwater conditions just above the bed. The gradual increase of seawater inflow begins again just above the second sand bed. We conclude that this series of sequential environmental changes indicates interseismic subsidence and coseismic uplift. The study area experienced around 1 m of uplift during the ad 1854 Ansei Tokai earthquake (Mw 8.4). In contrast, the area has subsided gradually ( c. 6 mm/yr) during the present interseismic period. The youngest sand bed may be correlated with the ad 1096 Eicho earthquake, which caused severe damage along the Shizuoka coast.

Coastal geomorphic conditions and styles of storm surge washover deposits from Southern Thailand

The characteristics of tropical storm washover deposits laid down during the years 2007 to 2011 along the southern peninsular coast of the Gulf of Thailand (GOT) were described in relation to their different geomorphic conditions, including perched fan, washover terrace and sheetwash lineations preserved behind the beach zone within 100m of the shoreline. As a result, washover terrace and sheetwash lineations were found where the beach configuration was uniform and promoted an unconfined flow. Non-uniform beach configurations that promoted a confined flow resulted in a perched fan deposit. Washover sediments were differentiated into two types based on sedimentary characteristics, including (i) a thick-bedded sand of multiple reverse grading layers and (ii) a medium-bedded sand of multiple normal grading layers. In the case of thick-bedded washover deposits, the internal sedimentary structures were characterized by the presence of sub-horizontal bedding, reverse grading, lamination, foreset bedding and wavy bedding, whereas, horizontal bedding, normal grading, and dunes were the dominant structures in the medium-bedded washover sand. Rip-up clasts were rare and recognized only in the washover deposits in the bottom unit, which reflects the condition when a mud supply was available. All washover successions were found in the landward inclined-bedding with a basal sharp contact. A high elevated beach ridge associated with a large swale at the backshore proved suitable for a thick-bedded washover type, whereas a small beach ridge with uniformly flat backshore topography promoted a medium-bedded washover sediment.

600-year sedimentary archive of hurricane strikes in a prograding beach ridge plain, southwestern Louisiana

This study tests a novel approach to paleotempestology, substituting the lateral time-depth of a prograding beach ridge plain for the vertical time-depth of an aggrading coastal lake, pond, lagoon, swamp or marsh. Trenching and coring of a beach ridge plain in southwestern Louisiana revealed six sand beds and one shell bed, interpreted as hurricane washover deposits. The sand beds are readily distinguished from enclosing marsh sediments by their higher sand content, lower organic content and contrasting microfossil assemblages. Based on the modern analogs of hurricanes Audrey (1957), Rita (2005) and Ike (2008), and consideration of nearby landfalling hurricanes in the historical record, it was determined that the storm intensity threshold of the study site is equivalent to a Category 3 hurricane. There is a wide variation in hurricane strike frequency between this site and other sites bordering the Gulf of Mexico. This variation results from differences in site sensitivity and the nature of geologic or geochemical proxies used to derive hurricane strike records. The approach demonstrated by this study could have applicability at other sites around the world where beach ridge plains are subject to tropical cyclone strikes. ► A new approach for paleotempestological research is successfully tested. ► Washover sand beds in a beach ridge plain record 600 years of hurricane strikes. ► Washover deposits are distinguished by texture, organic content and microfossils. ► Gulf of Mexico hurricane frequencies vary because of differences in site sensitivity. ► This new approach could be applicable at other sites around the world.

A 1900‐year paleohurricane record from Wassaw Island, Georgia, USA

AbstractWe present here the first paleotempestology record from Wassaw Island on the Georgia Bight, located in the south Atlantic coast of the United States. In the historical period, the Georgia Bight has experienced less frequent hits by hurricanes than other locations along the US Gulf and Atlantic coasts. The 1900‐year record inferred from the overwash sand layers from a back‐barrier marsh on Wassaw Island suggests that the island was directly struck by major storms on nine occasions during this interval. The Wassaw Island record shows alternating regimes, with periods of increased activity from >2000 a BP until ∼1100 a BP, and ∼100 a BP until the present, sandwiching a quiet period from ∼1100 to 250 a BP. Storm deposits from the most recent active period are perhaps amalgamated, indicating that site‐specific conditions may result in event undercounting and suggests that the relative thickness of sand layers in the sedimentary record is not always indicative of hurricane strength. Copyright © 2011 John Wiley & Sons, Ltd.

Inland fields of dispersed cobbles and boulders as evidence for a tsunami on Anegada, British Virgin Islands

Marine overwash from the north a few centuries ago transported hundreds of angular cobbles and boulders tens to hundreds of meters southward from limestone outcrops in the interior of Anegada, 140 km east–northeast of Puerto Rico. We examined two of several cobble and boulder fields as part of an effort to interpret whether the overwash resulted from a tsunami or a storm in a location where both events are known to occur. One of the cobble and boulder field extends 200 m southward from limestone outcrops that are 300 m inland from the island’s north shore. The other field extends 100 m southward from a limestone knoll located 800 m from the nearest shore. In the two fields, we measured the size, orientation, and spatial distribution of a total of 161 clasts and determined their stratigraphic positions with respect to an overwash sand and shell sheet deposit. In both fields, we found the spacing between clasts increased southward and that clast long-axis orientations are consistent with a transport trending north–south. Almost half the clasts are partially buried in a landward thinning and fining overwash sand and none were found embedded in the shelly mud of a pre-overwash marine pond. The two cobble and boulder fields resemble modern tsunami deposits in which dispersed clasts extend inland as a single layer. The fields contrast with coarse clast storm deposits that often form wedge-shaped shore-parallel ridges. These comparisons suggest that the overwash resulted from a tsunami and not from a storm.

Feasibility Study Analysis for Riverine Sand Mining/Scofield Island Restoration

A detailed feasibility study was performed to evaluate mining and transporting sand from the Mississippi River to restore Scofield Island, a rapidly-deteriorating barrier island in Plaquemines Parish, Louisiana. The proposed ecosystem restoration project includes reconstructing the beach and dune overtop the remaining island framework and closing existing breaches with riverine sand; and utilizing mixed sediments from an offshore mixed sediment source to construct a back-barrier marsh platform to create and sustain natural resource habitats and serve as the rollover platform for overwash sand. Studied and evaluated were the sand sources in the Mississippi River; methods for excavating and transporting the sand to Scofield Island; conveyance corridors from the river to the island; potential environmental and socioeconomic impacts; and estimated costs for various combinations of the aforementioned. Evaluation of eight alternative combinations of sand sources, excavation methods, and conveyance corridors on the basis of sixteen controlling factors and impact issues resulted in the recommendation of two riverine borrow areas and one conveyance corridor along an existing navigation waterway.

Transgressive Ravinement versus Depth of Closure: A Geological Perspective from the Upper Texas Coast

Abstract The upper Texas coast is one of the most populated areas along the Gulf of Mexico. Three dynamic barriers along this section of coastline (Bolivar Peninsula, Galveston Island, and Follets Island) have a well-documented history of shoreline change. Numerous engineering studies incorporating both sedimentological data and numerical models have been established for this system to understand sediment fluxes. However, rarely have previous studies examined sediment fluxes for the upper Texas coast in light of certain fundamental concepts of coastal geology. Here, we discuss the current theory and understanding of barrier island dynamics from a geologic standpoint as they relate to sediment budgets for the upper Texas coast. From sediment cores, we quantify both shoreface and washover sand fluxes, which previously were not incorporated as sand sinks into sediment budgets for this system. Shoreface sand fluxes represent a sizable portion of the total budget, whereas modern washover sand fluxes are minima...

Testing the use of feldspars for optical dating of hurricane overwash deposits

The geological record preserved in coastal salt marshes provides an opportunity to determine past hurricane activity during the Late Holocene in New England, USA. High precision dating is important to correlate overwash sand layers associated with hurricane strikes between different sites along the coastline. Three different optical dating methods have been tested and compared with independent age control; i) optically stimulated luminescence from quartz, ii) infrared stimulated luminescence from K-feldspar, and iii) a subtraction method. Quartz and K-feldspar dating results for three samples in a core from Round Hill Beach Marsh are in stratigraphic order and they are consistent within errors with radiocarbon ages and with each other. Subtraction dating results agreed with the quartz and K-feldspar ages for two of the three samples, but the subtraction age of the youngest sample gave an age underestimate. Replicate equivalent dose values from quartz showed a larger variation than those from feldspars, and this resulted in larger errors for the quartz and subtraction ages than those based on feldspars. K-feldspar yields the most precise optical ages, but is complicated by the need to correct for anomalous fading. Both quartz and K-feldspar are suitable for optical dating of hurricane overwash deposits in New England.

A 1200-year proxy record of hurricanes and fires from the Gulf of Mexico coast: Testing the hypothesis of hurricane–fire interactions

We present here the first high-resolution pollen record of vegetation response to interactions of hurricane and fire disturbances over the past 1200 yr from a small lake in Alabama on the Gulf of Mexico coast. The paleotempestological record inferred from the overwash sand layers suggests that the Alabama coast was directly struck by Saffir–Simpson category 4 or 5 hurricanes twice during the last 1200 yr, around 1170 and 860 cal yr BP, suggesting an annual landfall probability of 0.17% for these intense hurricanes. The charcoal data suggest that intense fires occurred after each of these hurricanes. The pollen data suggest that populations of halophytic plants (Chenopodiaceae) and heliophytic shrubs ( Myrica) expanded after the hurricane strikes, probably due to saltwater intrusion into the marshes and soil salinization caused by overwash processes. Populations of pines ( Pinus sp.) decreased significantly after each intense hurricane and the ensuing intense fire, suggesting that repeated hurricane–fire interactions resulted in high tree mortality and probably impeded recruitment and recovery. Our data support the hypothesis that the likelihood and intensity of fire increased significantly after a major hurricane, producing responses by vegetation that are more complex and unpredictable than if the disturbance agents were acting singly and independently.

Foraminiferal and Sedimentary Record of Late Holocene Barrier Island Evolution, Pea Island, North Carolina: The Role of Storm Overwash, Inlet Processes, and Anthropogenic Modification

Abstract 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.

High-Resolution Subsurface (GPR) Imaging and Sedimentology of Coastal Ponds, Maine, U.S.A.: Implications for Holocene Back-Barrier Evolution

Ground-penetrating radar (GPR) transects and sediment cores have been used to examine the basement morphology, stratig- raphy, and environmental history of maritime ponds along the pen- insular coast of Maine. Silver Lake, Lily Pond, and North Pond are shallow ( , 3 m) water bodies bordered by steep bedrock ridges in the north, east, and west, and sandy barriers to the south. The bedrock basins of the ponds are formed in metasedimentary rocks surrounded by resistant pegmatitic intrusions. A dense network of GPR traverses obtained over the ice-covered Silver Lake reveals a series of prominent wavy-parallel and basin-fill reflector geometries terminating against the bedrock or grading into the barrier sediments and interpreted as organic lake-bottom facies. The transparent units represent sand-rich horizons, mostly eolian in origin. Convex-up structures found both on the surface and within the basin-fill sequence are interpreted as pre- served parts of coastal dunes. The present study indicates that fresh- water conditions prevailed since at least 4.6 ka, with an initial sedi- mentation rate of 1.7 mm/yr. The position of this unit below the con- temporary sea level suggests presence of a welded barrier by that time. Radar profiles taken along the shores of Lily Pond, a small water body behind the Sand Dune Barrier, indicate a significantly larger areal extent of the pond in the past. A succession of organic deposits over- lying a Pleistocene glaciomarine unit indicates progressive inundation of the paleo-lagoon by rising sea level. Saltwater peat seaward of Lily Pond was buried by washover sands about 1.2 ka, and a narrow pond existed here prior to dredging and artificial infilling of its eastern part in the 1950s-60s. The organic and eolian units are absent in the North Pond, where sedimentary fill consists of glaciomarine clay overlain by marine sands. A proposed three-stage model of pond evolution along an embayed coastline consists of: (1) organic accumulation in an up- land depression during lower sea level; (2) predominantly washover or tidal deposition in a lagoon (Stage 2a) or blocked coastal pond (Stage 2b) during initial transgression, and (3) mainly eolian and organic de- position behind a prograded or aggraded barrier. Future accelerated rise in relative sea level and inadequate sediment supply will cause many back-barrier ponds to reenter Stage 2 of the proposed model.

Reconstruction of Prehistoric Landfall Frequencies of Catastrophic Hurricanes in Northwestern Florida from Lake Sediment Records

Sediment cores from Western Lake provide a 7000-yr record of coastal environmental changes and catastrophic hurricane landfalls along the Gulf Coast of the Florida Panhandle. Using Hurricane Opal as a modern analog, we infer that overwash sand layers occurring near the center of the lake were caused by catastrophic hurricanes of category 4 or 5 intensity. Few catastrophic hurricanes struck the Western Lake area during two quiescent periods 3400–5000 and 0–1000 14C yr B.P. The landfall probabilities increased dramatically to ca. 0.5% per yr during an “hyperactive” period from 1000–3400 14C yr B.P., especially in the first millennium A.D. The millennial-scale variability in catastrophic hurricane landfalls along the Gulf Coast is probably controlled by shifts in the position of the jet stream and the Bermuda High.

Depositional environment of the Vejle Fjord Formation of the Upper Oligocene-Lower Miocene of Denmark: a barrier island/barrier-protected depositional complex

The Vejle Fjord Formation was deposited in the coastal area at the eastern margin of the Upper Oligocene to Lower Miocene North Sea. Detailed studies of lithology and depositional structures demonstrate that coarsening-upwards successions resulted from landwards migration of barrier complexes as a response to relative sea-level rise. The formation of barriers, their migration and construction of new barriers was controlled by a varying balance between sediment supply and sea-level rise. The exposed sediments are mainly back-barrier deposits and represent deposition on the lagoon-facing barrier beach, wash-over fans, tidal flood deltas, tidal flats and the lagoonal floor. The barriers themselves are only sparsely represented in the studied exposures. Their influence on the depositional pattern is revealed by the formation of storm wash-over deposits and tidal inlet/tidal delta deposits. The destructional pattern of the barriers (storm erosion or tidal inlet widening) was apparently controlled by the orientation of barrier sections relative to the prevailing storm direction. A back-barrier beach deposit was developed with landwards-dipping heavy-mineral lamination. It forms part of a shallowing-upwards succession and represents a transgressive phase. Wash-over sands are up to 50 cm thick massive sand beds which pinch out laterally and interdigitate with lagoonal mud. Tidal inlet/tidal delta deposits are sandy intercalations in the lagoonal mud. The thickness is highly variable and marginal parts are strongly bioturbated. The tidal flat facies is dominated by small-scale channel fills of heterolithic deposits with a distinctive tidal rhythmicity, both on a single-tide scale and a neap—spring scale. The Vejle Fjord Formation is constructed of transgressive coarsening-upwards successions, which represent the growth and migration of barriers over their fine-grained back-barrier deposits. A large supply of clastic material forced new barriers to form further seawards than older ones, resulting in an overall regressive trend.

Towards an integrated study of the depositional environment of the Bencliff Grit (Upper Jurassic) of Dorset

Abstract An attempt to establish the depositional environment of the Bencliff Grit and its stratigraphic relationships is made using sedimentology, micropalaeontology, palynology and ichnology. Integration of these techniques demonstrates that the main sand units that characterize the Bencliff Grit represent periodic incursions by unidirectional west- and WNW-directed high-density flows, into water depths of at least 5 m from which biological recovery was relatively slow. An essentially autogenic process with dune migration over a colonized interdune area can probably be rejected. The ‘event’ sand units were not associated with colonized sediment-water interfaces. There are at least eight thin units of heterolithic muds and sands closely associated with two suites of marine trace fossils representing sand ( Diplocraterion habichi ) and mud ( D. parallelum ) associations. All mud samples are characterized by a signature of marine palynomorphs and microfossils. The palynofacies show significant differences which correlate with sedimentary facies. These include a palynofacies indicative of rapid sedimentation (in muds immediately following sands). In muds associated with the marine trace fossils a diagenetically modified assemblage is present. A bay or lagoonal setting with back-barrier washover sands is tentatively favoured rather than the intertidal, shoreface or estuary model previously used. The base of the Bencliff Grit does not a priori represent a sequence boundary and there are no parasequences within the formation. A sequence boundary may be present within the top 1 m of the formation, associated with a complex transgressive surface.

Reservoir Heterogeneity at West 76 Field: An Opportunity for Increased Oil Recovery by Geologically Targeted Infill Drilling

West 76 is a typical field of the Eocene Jackson-Yegua Barrier/Strandplain sandstone play in south Texas. Located in northwest Duval County, the field has produced 4.6 million barrels (MMbbl) as of 1988 and has an estimated 6 MMbbl of remaining mobile oil. The Jackson-Yegua play, which includes nearly 300 fields, has produced 624 MMbbl (as of 1988) and has estimated remaining mobile oil in excess of 1 billion barrels (Bbbl). Production at West 76 is from the Cole Sands of the uppermost Jackson Group at depths of 1,300 to 1,400 ft. The trapping mechanism is principally stratigraphic, but small normal faults influence production trends. Reservoir geometry is highly complex with numerous internal permeability barriers. The reservoir section was constructed by a progradational and overlying retrogradational barrier beach system that deposited discontinuous strike-oriented beach ridges, a strike-oriented tidal channel unit, and sand-poor lagoonal facies. Production trends mirror the strike-aligned beach-ridge and tidal-channel facies but also bear a minor dip-oriented component associated with the washover sand facies. Infill wells that produce from beach-ridge facies at rates an order of magnitude higher than existing, neighboring wells reflect the significant reservoir heterogeneity and highlight the considerable potential for untapped reservoir compartments. Identification of thesemore » compartments from detailed characterization of the reservoir provides targets for infill drilling and, ultimately, increased oil recovery. The geologic heterogeneity at West 76 has application to the entire Jackson-Yeuga Barrier/Strandplain sandstone play and increased recovery of the estimated 1 Bbbl of remaining mobile oil.« less