Spit Formation Research Articles

Global Distribution and Morphology of Deltaic Barrier Island Systems

ABSTRACT There are approximately 400 barrier islands on the world's deltaic plains, with a combined length of 4,100 kilometers. They make up 30% of the world's estimated barrier islands (by length). Deltaic barrier islands make up more than half of barrier islands in South America, Asia, and Africa, but only 5% in North America and Europe due to differing sea level rise history. Barrier islands are present on all types of deltas, including wave, tide, and river dominated deltas. The transgressive model of barrier island formation on the Mississippi Delta is well understood, but applies to relatively few deltaic barrier island chains. Spit formation, and to a lesser extent beach ridge accretion, on active lobes appear to be the most dominant processes of barrier island formation. A simple morphologic classification based on island length and inlet width is presented. Five island types (Nile, Mangoky, Niger, Gurupi, Mekong, and Mississippi) are described, relating island, inlet, and shoreface morphology to ...

Late- and Postglacial Sea-Level Change and Paleoenvironments in the Oder Estuary, Southern Baltic Sea

Knowledge of sea-level change in the southern Baltic Sea region is important for understanding the variations in late Pleistocene and Holocene sea-level change across northern Europe. These variations are a consequence of the response of the Earth's crust to the deglaciation of Fennoscandia and of the water added to the oceans from the melting of all Pleistocene ice sheets. The sedimentological and geochemical composition of five sediment cores from the lagoonal Oder Estuary offers new observational evidence for sea-level change and coastal development in the southern Baltic Sea region. The combined use of several geochemical proxies (organic carbon, nitrogen, calcium carbonate and biogenic opal contents, Corg/S and Corg/N ratios, δ13C values of organic matter, and δ15N values) is a new approach for the study area. The chemical evidence of this multiproxy approach allows clear identification of several stages in the development of the lagoonal environment: postglacial lake stages with sandy sedimentation during the Older Dryas and the Allerød stades, lacustrine phases with high autochthonous productivity during the Atlantic stade, terrestrial stages with peat formation at the beginning of the Subboreal stade, sedimentation as a result of marine transgression, and brackish sedimentation after the formation of sand spits and barrier islands during the Subatlantic stade. The stages are the result of regional sea-level change owing to complex shoreline development. They support the tentative sea-level curve proposed nearly 20 years ago for the region. In addition, changes in Oder River input in response to climate conditions is monitored. Whereas high terrigenous input of organic matter from the Oder River occurred during periods of humid climate during the Allerød, Atlantic, and Subatlantic stades, Oder River discharge decreased with drier and cooler climate conditions during the Subboreal stade. Furthermore, the geochemical evidence points to local anomalies such as the significance of river input and additional sulfate supply into the Oder lagoon for the composition of the sediments. Overall, the results provide a framework for future studies, which would allow for a more detailed comparison with other, similar environments.

The palaeoenvironments of coastal lagoons in the southern Baltic Sea, II. δ13C and δ15N ratios of organic matter — sources and sediments

Organic carbon and nitrogen isotope values ( δ 13C, δ 15N) and C/N ratios of six sediment cores from six coastal lagoons (including the Oder Estuary) were measured to chart the coastal development and to reconstruct the local palaeoenvironments of the southern Baltic Sea region during the Holocene. In addition, δ 13C, δ 15N and C/N values of major organic matter sources in the coastal lagoons and their drainage areas are investigated to determine the origin of organic matter (i.e. terrigenous or marine) in the sediments: plankton, aquatic macrophytes, typical C3 shore plants and peat. The δ 13C, δ 15N and C/N values of the samples collected show the clearly identifiable stages in the development of the water bodies: post-glacial lake stages with sandy sedimentation, lacustrine phases with high autochthonous productivity, terrestrial stages with peat formation, sedimentation as a result of marine transgression, and brackish sedimentation after the formation of sand spits and barrier islands. These stages are the results of sea level changes in the region. The values allow derivation of differences in the palaeoenvironments of the lagoons in the study area. A distinct terrestrial input is evident in the sediments of the lagoonal Oder Estuary, which can be attributed to the direct inflow of the Oder River into the lagoon. The isotope and C/N values also suggest a contribution of C4 plant detritus for the water bodies in the northeastern part of the study area (Barther Bodden, Grabow). The burial of autochthonous organic matter (i.e. plankton, aquatic macrophytes) in the sediment could be derived for all lagoons in this investigation.

The palaeoenvironments of coastal lagoons in the southern Baltic Sea, I. The application of sedimentary C org/N ratios as source indicators of organic matter

C/N ratios of organic matter sources in coastal lagoons and their drainage areas in the southern Baltic Sea region are investigated to determine the origin of organic matter (i.e. terrigenous or marine) in the sediments of the lagoons. These ratios are compared with δ 13C values in the area. Terrestrial plants in the study area show C/N ratios between 10 and 85, whereas aquatic macrophytes have values in the range of 6 to 44. Peat and shore vegetation have C/N ratios between 15 and 16, and plankton shows values close to 6. In conjunction with δ 13C values, the C/N ratios in the sediments allow the reconstruction of the Holocene palaeoenvironments and palaeoecology in the lagoons (Oder Estuary and Greifswalder Bodden). Distinct stages in the development of the water bodies, resulting from sea level changes in the region, can be derived: post-glacial lake stages with sandy sedimentation, lacustrine phases with high autochthonous productivity, terrestrial stages with peat formation, sedimentation as a result of marine transgression, and brackish sedimentation after the formation of sand spits and barrier islands. The application of C org/N tot ratios instead of C org/N org does not have any significant influence on the interpretation of the data and may thus be used in the coastal sediments of the southern Baltic Sea after having applied the test procedures presented in this study.

The middle and late Holocene Barrier Spit System at Vejers, Denmark: Structure and Development

Georadar data (72 km) combined with borings and datings form the basis of a study of the three-dimensional build-up of the middle and late Holocene barrier spit system at Vejers, Denmark. The georadar data reveal one barrier spit covering 15-20 km2 , with an average thickness of approximately 10 meters. This barrier spit shows a tripartite build-up. At the base a shoal sand unit of well-sorted, fine- to medium-grained sand occurs. The overlying interval constitutes a barrier core unit, stretching from north to south, and composed of alternating layers of westward dipping coarse sand- and gravel layers. At the top of these layers aeolian sand sheet and dune deposits occur. The barrier core unit is followed to the east by a back-barrier unit of fine- to medium-grained sand, with a varying content of silt and plant fragments. These deposits are also overlain by aeolian sediments. A second, smaller and more inland situated barrier spit occurs in the central and southern parts of the investigated area. It appears that barrier spit formation took place in three main stages. The initial stage occurred between c. 6500 and c. 4000 B.P. (transgressive period). Barrier spit consolidation and rapid growth took place between c. 4000 B.P. and c. 1200 A.D. (early highstand period). Final development and large-scale dune formation took place after 1200 A.D. (highstand period). The dominance of west-ward dipping strata in the spit deposits indicates consistent seaward progradation of the spit. The shape of the spit indicates southward growth. Apparently the spit formed under the influence of a strong southward directed littoral drift, but the overall alignment of the spit was controlled by swash processes.

Etude " in situ " du fonctionnement des brise-lames de protection du littoral sud du petit golfe de Tunis (Tunisie)

The current estimations of essential factors of coastal dynamics in the smallerGulf of Tunis relate erosion of the coasts, substantial as of the 50's, and strongly accelerating since then, to human action on the continent. The localized disappearance of beaches followed by the attack of coastal infrastructures by swell, led to the installing of defense installations. More particularly, along the South coast beaches, 17 breakwaters, isolated or in series, form a natural laboratory. The position of these installations, all above water, was studied as of the installation: origin of the trapped sand, influence of artificial refill, formation and evolution of sand spits and sometimes tombolos. The influence of conventional waterbreak characteristic dimensions ( length, distance to the shore, spacing of any) on their efficiency led to a proposal to optimize dimensioning in order to satisfy a triple requirement of protection of the beaches around the Gulf of Tunis: to retain as much sand as possible, but without the formation of tombolo, white preventing erosion along the bank lines due to the installations.

A model of coastal evolution in a transgressed thermokarst topography, Canadian Beaufort Sea

The coast of the Southern Canadian Beaufort Sea consists of bluffs of ice-bearing Quaternary sediments, and of spits and barrier islands enclosing (more or less completely) lagoons and complex embayments formed by the breaching of thaw lakes. The study of the evolution of this coast developed in a thermokarst topography and of the shallow stratigraphy of the inner continental shelf has resulted in the development of a conceptual model of coastal evolution. Five stages have been defined in this model which form an idealized continuum of coastal evolution. According to the model, the formation of embayments, spits and barrier islands is primarily controlled by the pre-existing topography, relative sealevel rise and local sediment supply. Sealevel rise over a topography of thermokarst basins formed in ice-bearing sediments leads to the formation of embayments and rapidly eroding headlands from which spits develop. Geomorphic evidence suggests that barrier islands mainly form by spit breaching or by erosion of tundra islands. Breached-lake basins act as sediment sinks and may restrict the development of coastal accumulation features. Spits and barrier islands are rapidly retreating landward, the mean retreat rates being 2.2 m a −1 and 3.9 m a −1 respectively. On an annual time-scale, spits and barrier islands retreat in response to episodic storm-generated overwash events, but on a geologic time-scale, relative sealevel rise in the major forcing mechanism of landward migration. While retreating landward, these coastal accumulation features may be drowned and possibly partially preserved in breached lake basins. During the Holocene transgression, the shoreface has undergone erosional retreat, partly eroding the pre-existing topography but preserving the bottom of some breached thaw lakes and lagoons which are now overlain by a transgressive sand sheet on the inner shelf. Our observations provide the basis of a semi-quantitative model of shoreline changes for the barrier coast of the Canadian Beaufort Sea which relates coastal stability to bluff erosion, ground-ice content, sediment texture, offshore sediment supply, wave energy, volume of breached lake basins, relative sealevel rise, and regional slope.

Rapid formation and degradation of barrier spits in areas with low rates of littoral drift

A small barrier beach exposed to low-energy waves and a small tidal range (0.7 m) along Nantucket Sound, Mass., has experienced a remarkable growth phase followed by rapid attrition during the past century. In a region of low longshore-transport rates, the barrier spit elongated approximately 1.5 km from 1844 to 1954, developing beyond the baymouth, parallel to the adjacent Nantucket Sound coast. Degradation of the barrier spit was initiated by a succession of hurricanes in 1954 (Carol, Edna and Hazel). A breach opened and stabilized near the bay end of the one kilometer long inlet channel, providing direct access for exchange of baywater with Nantucket Sound, and separating the barrier beach into two nearly equal limbs. The disconnected northeast limb migrated shorewards, beginning near the 1954 inlet and progressing northeastward, filling the relict inlet channel behind it. At present, about ten percent of the northeast limb is subaerial: the rest of the limb has completely filled the former channel and disappeared. The southwest limb of the barrier beach has migrated shoreward, but otherwise has not changed significantly since the breach. A new mechanism is proposed for spit elongation when the inlet thalweg parallels the beach axis, in which material scoured from the lengthening inlet is the dominant source for spit accretion (perhaps initially deposited as a linear channel-margin bar which later becomes subaerial). The lengthening spit causes the parallel inlet to elongate, which in turn further lengthens the spit, in a self-generating fashion. This mechanism provides both a source of sediment for elongating the barrier spit, and a sink for material scoured from the lengthening inlet. The proposed mechanism for spit growth may be applicable to other locations with low wave energy, small tidal prisms and low longshore sand transport rates, suggesting that estimates of directions and rates of longshore sand transport based on spit geomorphology and development be scrutinized on a case-by-case basis.

The formation and evolution of Point Pelee, western Lake Erie

Point Pelee originated as a sandy foreland enclosing a marsh approximately 4000 years BP. A reconstruction of paleoenvironmental conditions prior to that time suggests strongly that it was formed initially by the progressive merging of beach ridges and dunes formed on opposite sides of the Pelee-Lorain moraine when rising lake levels in the western basin of Lake Erie were 3 to 4 m below present lake datum (173.4 m above sea level). Since that time, it has retreated to its present position and orientation under the influence of slowly rising lake levels and increasing wave energy from both sides.Such an evolution, though different from conventional mechanisms of spit formation, is supported by evidence derived from the local post glacial stratigraphy and the geomorphology of relict features preserved on the Point and on the shoal area to the south.

Coastal Processes and Depositional Patterns on Cape Ann, Massachusetts

ABSTRACT Four beaches on the southeastern coast of Cape Ann were studied to determine sediment source, transport, and depositional patterns. Methods of analysis included beach profiling, sediment sampling, and simulated wave refraction. Wave energy, resulting primarily from northeast storms and the prevailing southwesterlies, concentrates on nearshore island and headland complexes. Due to wave refraction, northeast flowing longshore currents are found at Long, Cape Hedge and Pebbly Beaches. At Good Harbor, longshore drift is predominantly southwestward. The wave energy and refraction patterns determine beach gradients and grain size distribution. Predominate direction of longshore drift and systematic internal decreases in grain sizes support a spit formation for the baymouth barrier beaches. and-size sediments are primarily glacial in origin and secondarily a result of erosion of the crystalline headlands. The source of cobbles at Cape Hedge and Pebbly Beaches is believed to he a moraine which intersects the shoreline at Cape Hedge.

A Simulation Model of a Complex Recurved Spit

A simulation model of a particular coastal spit is presented to illustrate the value of such models in studying the processes that lead to spit formation. Hurst Castle spit in Hampshire was chosen for the model as it has a distinctive form due to the operation of several easily identified wave types. The processes forming the spit have been discussed by W. V. Lewis. The main ridge, which is composed of shingle, is prolonged by westerly waves, while storm waves build it up. The recurves are formed of material drifted round the end of the main ridge by waves from a southerly point. Waves from the northeast, coming down the Solent, build the lateral recurves. These become longer and more numerous toward the distal end of the spit. The computer program simulates the operation of waves from the west, storm waves, southeasterly waves, and waves from the northeast. In addition, a depth factor simulates the increasing depth of water offshore. This accounts for the increase in number of recurves toward the distal end. A refraction factor allows the curvature of the main ridge to be simulated. The proportion of random numbers allocated to these variables can be adjusted in the data input to elucidate the part they play in the formation of the spit. The close fit of the standard spit to the real spit suggests that the controlling variables are being correctly simulated.

Chenier versus Barrier, Genetic and Stratigraphic Distinction: ABSTRACT

Barrier islands and cheniers are elongate, narrow sand bodies which may appear similar where preserved in the sedimentary record. However, their modes of origin and sequence of development are distinctive. Differentiation of these features is important in the interpretation of the depositional environments, paleogeography, and geologic history of coastal areas. Chenier development begins with progradation by deposition of clay, silt, and sand. Rapid sedimentation precludes removal of fine material. Progradation is followed by reworking, shore retreat, and formation of a ridge at the head of the beach. Fines are transported seaward and along the shore. Sand is concentrated on the upper beach and over the adjacent marsh, and is transported along the shore, possibly accumulating in areas not actively eroding. The contact of the chenier with marsh and mud-flat deposits is disconformable beneath transgressive sand deposits, but may be intertonguing for laterally transported deposits. Increasing rates of sedimentation reinitiate mud-flat progradation and the sand ridge is left as chenier. Holocene cheniers are commonly less than 15 feet thick. Barriers originate from a topographic ridge at the head of the beach which subsequently is partly submerged. Lagoonal-marsh sediments are deposited behind the barrier; however, continued subsidence accompanied by transgression may result in a complex intertonguing of barrier and lagoonal-marsh sediments. Barriers also form as spits and may develop seaward from a pre-existing barrier. Repeated spit formation results in the formation of sand bodies enclosed in finer sediments. Barriers, like cheniers, may be eroded, reworked, and moved landward over the adjacent marsh. Barriers predate the lagoonal-marsh sediments, whereas the sand ridge of the chenier develops on, and seaward from, existing marsh and mud-flat deposits. End_of_Article - Last_Page 471------------

Iroquois beach in Ontario

Research Article| January 01, 1904 Iroquois beach in Ontario A. P. COLEMAN A. P. COLEMAN Search for other works by this author on: GSW Google Scholar GSA Bulletin (1904) 15 (1): 347–368. https://doi.org/10.1130/GSAB-15-347 Article history first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation A. P. COLEMAN; Iroquois beach in Ontario. GSA Bulletin 1904;; 15 (1): 347–368. doi: https://doi.org/10.1130/GSAB-15-347 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract IntroductionThe signs of wave action in the cutting of cliffs, the piling up of beach sands and gravels, and the formation of bars or spits across the mouth of bays are so well marked on the old Iroquois beach that it was early recognized as a shore formation by farmers and land surveyors, as well as geologists. The first written mention of the beach in Ontario is contained in Thomas Roy’s paper on the “Ancient State of the North American Continent,” read by Sir Charles Lyell before the Geological Society of London in 1837; * and Lyell was so much interested in the account of the series of terraces which Roy described that on his visit to America he crossed from Niagara to Toronto in 1842 to examine them. Roy noted a number of sand and gravel beaches at various levels above lake Ontario up to 762 feet, and . . . This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.