Continued Sea-level Rise Research Articles

Assessing ‘coastal squeeze’ of wetlands at the Yellow River Delta in China: A case study

Coastal wetlands worldwide are subject to increasing threats from continued sea level rise (SLR), while their potential adaptation through land-ward migration is often impeded by natural or man-made barriers. The resultant sea- and land-ward squeeze exacerbates the loss of wetlands, causing severe ecological consequences. To address this issue for coastal wetlands at the Yellow River Delta (YRD) in China, the present study adapted a fuzzy-system-model (FSM) based coastal squeeze assessment method (Torio and Chmura, 2013) to assess the potential of coastal squeeze under assumed future SLR scenarios. Coastal squeeze indices for slope and surface imperviousness were integrated to generate the composite coastal squeeze index (CCSI) as a unified metric that accounts for both factors as the primary contributors to coastal squeeze. The distribution of the confidence-weighted CCSI was used to identify vulnerable area at three selected study sites, and results for three representative years, i.e., 1989, 2000 and 2010, were compared to illustrate the historical changes in recent decades. Due to the predominately flat topography at the YRD, slope was found to be an insignificant contributor to coastal squeeze, whereas surface imperviousness plays a dominant role. As such, the coastal squeeze potentials at the three study sites in 2000 appeared to be considerably higher than those at 1989 and 2010 as the surface imperviousness experienced increasing-then-decreasing variation arising from concurrent land cover change. The average coastal squeeze potential at the three study sites in 2000 also tended to be more sensitive to the assumed SLR scenarios, and featured a prominent peak at 1.5 m SLR. The present study showcases the assessment of coastal squeeze of wetlands at the YRD and the region, and provides important references for coastal wetland conservation efforts under increasing threats from climate change and human activities.

RELATIONSHIP BETWEEN SEQUENCE STRATIGRAPHY AND RELATIVE SEA-LEVEL CHANGES

The continuous sea-level rise will result in conditions where the level of accommodation space is greater than that of sediment supply produced undertransgression conditions. When the sea level reaches its maximum point, the sedimentation rate will exceed the sea level rise and aggrades becomes more dominant progradation will result in new Highstand System Tract (HST) condition. Keyword: Accommodation, Sea level changes, Sedimentation, Sequence, Stratigraphy

Ostracods biostratigraphy of the Oligocene-Miocene carbonate platform in the Northeastern Amazonia coast and its correlation with the Caribbean region

Oligocene-Miocene ostracods biozones are proposed for the ∼65 m-thick platform carbonate succession exposed in the Northeastern Amazonia coast, Brazil. Previous biostratigraphic studies based on planktonic foraminifera, nannofossils and palynomorphs are poorly age constrained and have hindered the correlation with other units of the Atlantic Equatorial margin. Tectonic stability of the Northeastern Amazonia coast during Neogene, associated with reduced riverine inflow and continuous sea level rise, allowed the establishment of lagoon/mangroves, tidal channel and shallow platform settings favoring massive proliferation of benthic ostracods. The recurrence of these depositional systems along of entire Oligocene-Miocene succession contributed mainly for the preservation of typical assemblages of lagoonal ostracods. Among thirty-two ostracods genera identified, the most of them are generally polyhalines associated with a mesohaline genus as Perissocytheridea. Rare ostracods genera typical of offshore zone indicate limited oceanic connection with lagoon. Additionally, the rare presence of Cyprideis indicates a relatively stable salinity degree suggesting change in the lagoon dynamic until estuarine conditions. The ostracods comprise more than 100 species, ranging from Upper Oligocene to Lower Miocene with five index species correspondent to a single zone called the Cytherella stainforthi Zone that was subdivided in four sub-biozones: 1) Jugosocythereis pannosa, 2) Quadracythere brachypygaia, 3) Triebelina crumena and 4) Neocaudites macertus. This new zonation was calibrated with the Blow's and Wade's planktonic foraminifers zones (N.3 to N.7 zones corresponding to O6 to M4b of Wade) and with van den Bold's zonation in the Neogene Caribbean region. Ostracod assemblages described here provide an excellent biostragraphic framework for local, intrabasinal and regional correlation for the Oligocene-Miocene deposits of the Northeastern Amazonia coast and Caribbean regions. The strong similarity of to the Caribbean deposits open a discussion about the possible paleobiogeographic affinities between the biotas of the Equatorial Atlantic during the Neogene.

The Future Prediction of the One-Dimensional Topography of the Estuary Delta of the Shirakawa River

Predicting the long-term topographical change based on results of a time-slice experiment using a General Circulation Model (GCM) is difficult because actual change is a result of the continuum of events occurring in succession leading from the past to the future. We developed a one-dimensional topographical model of an estuary delta as the first step of assessing climate change effects. Three major effects, i.e. tidal flow, waves and sediment supply from the river, were included in this model. In order to estimate the sensitivity of these effects, simulations with virtual conditions were conducted. These simulations show equilibrium profiles that are close to the results of Roberts et al. [2000] “Predicting the profile of intertidal mudflats formed by cross-shore tidal currents,” Proc. Marine Sci. 3, 263–285.]. The simulation results were validated with observation data from the Shirakawa River delta. As a long-term prediction (about 37 years), the propagation of the rollover point was less than the actual data showed. The gradient of the subtidal zone was gentler than that observed. However, the short-term prediction (about 17 years) agrees with the observation data. These results show that old, unreliable, observation data used as a boundary condition significantly affects the reproducibility of the actual tidal flat profile. Finally, the effect of continuous Sea Level Rise (SLR) over 100 years from the present was investigated. As expected, the simulation results show a shift of the shoreline landward. The water depths in the intertidal and subtidal zones increase compared to a no-SLR condition. Therefore, the topset area grows as a consequence of SLR. Additionally, it was shown that future accumulation in the subtidal zone is reduced with SLR.

Ground-Penetrating-Radar Characterization and Porosity Evolution of An Upper Pleistocene Oolite-Capped Depositional Cycle, Red Bays, Northwest Andros Island, Great Bahama Bank

Abstract: Linkages among surface sediments, depositional processes, geomorphic forms, stratigraphic architecture, and pore distribution in Bahamian sand bodies and oolite-capped depositional successions have been characterized in recent studies. An understanding of how these parameters, especially porosity, are preserved or modified in the eogenetic environment is essential in bridging the gap between modern and ancient analogs. Two complementary 3D (200 MHz and 400 MHz) ground-penetrating-radar surveys and three shallow cores reveal that the uppermost part of the upper Pleistocene (Marine Isotope Stage 5e) Lucayan Formation at Red Bays, Andros Island, Great Bahama Bank, comprises a single, 6-m-thick upward-shallowing parasequence. Six radar packages (P1–P6) bounded by radar surfaces (S1–S6) have been identified in the two 3D radar volumes. The stratigraphic succession indicates development of a burrowed backshoal lagoon during early flooding of the bank top followed by deposition of flood-tide-driven, low-angle sheet sands and sigmoidal subaqueous dune deposits as the shelf-margin sand shoal moved bankward as a function of continued sea-level rise. Constructional accommodation on the front of the prograding subaqueous dune in the northwest part of the survey area and erosional accommodation created by downcutting of a shallow tidal channel into the upper part of the subaqueous dune depositional unit in the northeast part of the study area were filled with peloid- and ooid-dominated carbonate sands as sea level stabilized. The uppermost radar package is a thin (0.15 to 0.55 m), partially calichified carbonate sand sheet that mantles the entire survey site and that reflects late highstand and fall of sea level. Exposure of the studied interval to meteoric vadose diagenesis over the past 100,000+ years has resulted in partial stabilization of the largely aragonitic precursor sediment through selective partial dissolution of aragonitic grains (mainly ooid cortical layers, peloids, and mollusk shells) accompanied by precipitation of patchily distributed low-magnesium calcite cement. Core data demonstrate a relationship between stratigraphically controlled sedimentological attributes, diagenesis, and pore distribution. Three distinctive zones of porosity were present upon deposition: a lower zone of relatively high interparticle porosity (21.3% to 33.2%) in the medial part of P1, a low-porosity zone (

Occurrence of high-diversity metazoan- to microbial-dominated bioconstructions in a shallow Kimmeridgian carbonate ramp (Jabaloyas, Spain)

The horizontal and vertical transitions of a wide range of bioconstructions are documented from the shallow domains of a Kimmeridgian carbonate ramp (Upper Jurassic) in the Jabaloyas area of NE Spain. The bioconstructions include microbial buildups, coral-bearing thrombolite buildups, coral-microbial buildups, branching coral patches, oyster patches, and stromatoporoid carpets. Buildups form stacked pinnacles up to 19 m thick, within a broad spectrum of coeval inter-buildup carbonate facies. Coral-bearing thrombolites are coincident with shallow-marine oolitic sands, indicating development during the initial platform flooding (unit 1). During the continued sea-level rise (units 2 and 3), coral-microbial buildups [encrusted by Crescentiella (Tubiphytes) and serpulids] were established from proximal to distal mid-ramp domains, and these showed an increasing proportion of microbial crust in distal domains. Inter-buildup oolitic facies sharply grade down-dip to hummocky cross-stratified intraclastic, peloidal, and skeletal deposits, mostly sourced from the coral-microbial buildups. The lower part of unit 4 was dominated by microbialites in the proximal areas, related to local fresh-water input causing seawater stratification and oxygen depletion. The upper part of unit 4 indicates an initial recovery of metazoan frame builders, with abundant branching corals. During the late regression (units 5 and 6), Marinella lugeoni red algae, oyster patches, and stromatoporoid boulders developed close to the shoreline in well-oxygenated waters with high nutrient content. The reported data contribute to the discussion of the optimal environmental conditions for each “bioconstruction window” in Jabaloyas, namely sediment and nutrient supply, water depth, water oxygenation, wave energy and light availability.

Adapting to rates versus amounts of climate change: a case of adaptation to sea-level rise

Adaptation is the process of adjusting to climate change in order to moderate harm or exploit beneficial opportunities associated with it. Most adaptation strategies are designed to adjust to a new climate state. However, despite our best efforts to curtail greenhouse gas emissions, climate is likely to continue changing far into the future. Here, we show how considering rates of change affects the projected optimal adaptation strategy. We ground our discussion with an example of optimal investment in the face of continued sea-level rise, presenting a quantitative model that illustrates the interplay among physical and economic factors governing coastal development decisions such as rate of sea-level rise, land slope, discount rate, and depreciation rate. This model shows that the determination of optimal investment strategies depends on taking into account future rates of sea-level rise, as well as social and political constraints. This general approach also applies to the development of improved strategies to adapt to ongoing trends in temperature, precipitation, and other climate variables. Adaptation to some amount of change instead of adaptation to ongoing rates of change may produce inaccurate estimates of damages to the social systems and their ability to respond to external pressures.

How effective is albedo modification (solar radiation management geoengineering) in preventing sea-level rise from the Greenland Ice Sheet?

Albedo modification (AM) is sometimes characterized as a potential means of avoiding climate threshold responses, including large-scale ice sheet mass loss. Previous work has investigated the effects of AM on total sea-level rise over the present century, as well as AM’s ability to reduce long-term (≫103 yr) contributions to sea-level rise from the Greenland Ice Sheet (GIS). These studies have broken new ground, but neglect important feedbacks in the GIS system, or are silent on AM’s effectiveness over the short time scales that may be most relevant for decision-making (<103 yr). Here, we assess AM’s ability to reduce GIS sea-level contributions over decades to centuries, using a simplified ice sheet model. We drive this model using a business-as-usual base temperature forcing scenario, as well as scenarios that reflect AM-induced temperature stabilization or temperature drawdown. Our model results suggest that (i) AM produces substantial near-term reductions in the rate of GIS-driven sea-level rise. However, (ii) sea-level rise contributions from the GIS continue after AM begins. These continued sea level rise contributions persist for decades to centuries after temperature stabilization and temperature drawdown begin, unless AM begins in the next few decades. Moreover, (iii) any regrowth of the GIS is delayed by decades or centuries after temperature drawdown begins, and is slow compared to pre-AM rates of mass loss. Combined with recent work that suggests AM would not prevent mass loss from the West Antarctic Ice Sheet, our results provide a nuanced picture of AM’s possible effects on future sea-level rise.

Famennian glaciation in the eastern side of Parnaíba Basin, Brazil: evidence of advance and retreat of glacier in Cabeças Formation

ABSTRACTGlaciotectonic features studied in the siliciclastic deposits of Cabeças Formation, Upper Devonian, represent the first evidence of Famennian glaciation in Southeastern Parnaíba Basin, Brazil. Outcrop-based stratigraphic and facies analyses combined with geometric-structural studies of these deposits allowed defining three facies association (FA). They represent the advance-retreat cycle of a glacier. There are: delta front facies association (FA1) composed of massive mudstone, sigmoidal, medium-grained sandstone with cross-bedding and massive conglomerate organized in coarsening- and thickening-upward cycles; subglacial facies association (FA2) with massive, pebbly diamictite (sandstone, mudstone and volcanic pebbles) and deformational features, such as intraformational breccia, clastic dikes and sills of diamictite, folds, thrust and normal faults, sandstone pods and detachment surface; and melt-out delta front facies associations (FA3), which include massive or bedded (sigmoidal cross-bedding or parallel bedding) sandstones. Three depositional phases can be indicated to Cabeças Formation: installation of a delta system (FA1) supplied by uplifted areas in the Southeastern border of the basin; coastal glacier advance causing tangential substrate shearing and erosion (FA1) in the subglacial zone (FA2), thus developing detachment surface, disruption and rotation of sand beds or pods immersed in a diamicton; and retreat of glaciers accompanied by relative sea level-rise, installation of a high-energy melt-out delta (FA3) and unloading due to ice retreat that generates normal faults, mass landslide, folding and injection dykes and sills. The continuous sea-level rise led to the deposition of fine-grained strata of Longá Formation in the offshore/shoreface transition in the Early Carboniferous.

Sea-level rise and other influences on decadal-scale salinity variability in a coastal plain estuary

The response of salinity in the Delaware Estuary to climatic variations is determined using statistical models and long-term (1950-present) records of salinity from the U.S. Geological Survey and the Haskin Shellfish Research Laboratory. The statistical models include non-parametric terms and are robust against autocorrelated and heteroscedastic errors. After using the models to adjust for the influence of streamflow and seasonal effects on salinity, several locations in the estuary show significant upward trends in salinity. Insignificant trends are found at locations that are normally upstream of the salt front. The models indicate a positive correlation between rising sea levels and increasing residual salinity, with salinity rising from 2.5 to 4.4 per meter of sea-level rise. These results are consistent with results from 1D and dynamical models. Wind stress also appears to play some role in driving salinity variations, consistent with its effect on vertical mixing and Ekman transport between the estuary and the ocean. The results suggest that continued sea-level rise in the future will cause salinity to increase regardless of any change in streamflow.

Middle- to late-Holocene storminess in Brittany (NW France): Part II – The chronology of events and climate forcing

This study focuses on the recurring climate conditions required for the largest storms occurring in NW France (Brittany). It is based on the analysed records of storm events along Western Brittany coast (see Part I). In this manuscript (Part II), storm recurrence is explored along with forcing mechanisms. Periods of more frequent storm events over the two last centuries are analysed first in order to link these events with possible forcing mechanisms (North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO) modes) triggering the most destructive storms. Then, palaeostorm events are discussed at the Holocene scale, from 6000 yr BP to present, to verify the forcing mechanisms. Most recorded events appear to be linked with cooling episodes, mostly in winter, a transition to or from a negative winter NAO mode, a positive AMO mode. Extreme storms occur immediately prior to the ‘Medieval Warm Period’ (MWP). Maximum effects are reached prior to the onset of the MWP and during the Maunder and Dalton solar minima. Low storm activity occurred during the Spörer Minimum linked to an acceleration of the Atlantic Meridional Overturning Circulation (AMOC). Main storm triggers seem to correspond to a positive AMO mode with an unstable jetstream configuration driving a negative NAO. In this study, four specific weather configurations were defined to explain each type of recorded storminess. The strongest storms correspond to low AMO and decennial-negative NAO modes (e.g. ‘Little Ice Age’), or high AMO in association with dominant low NAO modes, as during the early Middle Age and present-day period. Fresh or warm oceans in association with a positive NAO mode are stormy but with very low sting storms frequency. Although in agreement with the orbital forcing and the Holocene glacial history, increasing storm frequency and intensity is most probably partly biased by continuous sea-level rise and resulting erosion.

Shoreline changes interpreted from multi-temporal aerial photographs and high resolution satellite images: Wotje Atoll, Marshall Islands

Wotje Atoll is located at 9°25′N and 170°04′E within the Republic of the Marshall Islands in the central Pacific Ocean. As on other atolls, the islands perched along the rim of Wotje are low-lying and considered highly vulnerable to the impacts of climate change. A widely anticipated impact of continued sea level rise is the chronic erosion of island shorelines. Using a combination of aerial photographs and satellite imagery shoreline changes are assessed over a 67-year period characterized by rising sea level. Results indicate that between 1945 and 2010 shoreline accretion is more prevalent than erosion, with an average Net Shoreline Movement (NSM) of +1.74m, indicating accretion. Shorelines were accretionary along the lagoon, ocean and channel facing shorelines, as well as on elongate spits and small islands. A high-frequency assessment of shoreline change on a subset of islands in the east of Wotje reveals that islands were stable, with a balance between shoreline accretion and erosion. Shorelines interpreted from high resolution satellite imagery captured between 2004 and 2012 indicate that shorelines within this sample of islands are largely in an erosive state. The post-2004 shift toward erosion may be sea level rise induced, or part of an unresolved shoreline oscillation. This study demonstrates the critical need for improved shoreline change monitoring within atoll settings in order to assess sea level rise impacts along island shorelines.

Mid-Holocene mangrove succession and its response to sea-level change in the upper Mekong River delta, Cambodia

Middle Holocene vegetation and mangrove successions are clearly evident in the palynological records of two cores from the upper Mekong River delta in Cambodia. Spanning from ~9.4 to 6.3calkaBP, the cores mainly record a transgressive sequence from floodplain freshwater marsh to tidal flat, which was overlain by mangrove. Corresponding to the decelerated sea-level rise at ~8.3calkaBP, pioneer mangrove species Sonneratia alba and Sonneratia caseolaris appeared in the sediments, and then was replaced by regressive mangrove succession containing upward-increasing abundances of Rhizophora apiculata and Bruguiera spp. High salinity- and flooding-tolerant community S. alba was developed at the western core site PSG at ~8.2calkaBP, and the eastern core site PK at ~7.5calkaBP. The time difference of S. alba appearance between the two sites might be resulted from the complexity of sedimentary environment, where a higher sediment supply was provided to the western floodplain than to the eastern floodplain. After 7.5calkaBP, aggradational stacking of intertidal sediments, of which the thickness is larger than the present maximum tidal range, may have resulted from continuous sea-level rise during 7.5–7.0calkaBP.

Preservation of a drowned gravel barrier complex: A landscape evolution study from the north-eastern English Channel

Landscape response to post-glacial relative sea level during the Quaternary is documented using an integrated dataset of multibeam bathymetry and 2D seismic reflection profiles from the Hastings Bank area in the north-eastern English Channel. Mapping of nine seismic stratigraphic units calibrated to lithological information from multiple vibrocores has enabled the interpretation of fluvial, shoreface, barrier, washover fan, back-barrier and tidal environments of deposition. The interpreted landscape evolution is as follows: (i) fluvial incision of bedrock during sea-level lowstand; (ii) progradation of a shoreline and then development of a barrier complex as sea-level rose; (iii) recycling and breaching of the barrier; (iv) rapid drowning of the barrier complex; (v) landward migration of the shoreline through continued sea-level rise; and (vi) complete abandonment and submarine preservation of the barrier complex during sea-level highstand. The previously undocumented, yet exceptionally well preserved, drowned barrier complex at Hastings Bank records phases of barrier initiation, breakdown and retreat, and documents coastal response to high rates of relative sea-level rise. Initial development of the barrier complex required a sufficient supply of sediment, maintained by offshore sources, to keep pace with rising sea level, which permitted progradation of a shoreline and development of a barrier complex. Inherited topography in the north-eastern English Channel is an important factor in the development of the barrier complex. Phases of barrier breakdown occur when sediment supply is outpaced by a rapid increase in accommodation controlled by existing basement morphology and rising sea levels. Subsequently, the barrier responds through internal reorganisation by breaching and reworking of existing sediment bodies. Barrier retreat is characterised by a phase of ‘sediment surplus’ overstepping under rapid rates of sea-level rise where increased water depths limit wave reworking, followed by a phase of discontinuous retreat where the shoreline steps back through ‘sediment deficit’ overstepping. Hastings Bank presents a rare opportunity to examine the conditions and processes that control barrier response to sea-level rise and, to assess the preservation potential of barrier deposits as a function of the style of retreat.

Wind-Driven Sea-Level Variation Influences Dynamics of Salt Marsh Vegetation

Long-term variation of mean sea level has been considered the primary exogenous factor of vegetation dynamics in salt marshes. In this study, we address the importance of short-term, wind-induced rise of the sea surface in such biogeographic changes. There was an unusual opportunity for examining field data on plant species frequency, sea-level variation, and sedimentation acquired from the Skallingen salt marsh in Denmark since the 1930s. The environmental and floristic history of Skallingen was summarized as (1) continuous sea-level rise with temporal variability (2.3–5.0 mm yr−1), (2) continuous sedimentation with spatial variability (2.0–4.0 mm yr−1), (3) increased frequency of over-marsh flooding events, and (4) contemporary dominance of Halimione portulacoides, indicating little progressive succession toward a later phase. Conventionally, recent eustatic sea-level rise was believed to drive the increased frequency of flooding and such retarded succession. Skallingen, however, has showed more or less equilibrated yearly rates between sea-level rise and surface accretion. This implies that the long-term, gradual sea-level rise alone might not be enough to explain the increased inundation frequency across the marsh. Here, we suggest an alternative chain: Recent trends in the North Atlantic Oscillation index toward its positive phase have led to increased storminess and wind tides on the ocean surface, resulting in increased frequency, duration, and depth of submergence, and hence, waterlogging of marsh soils, which has retarded ecological succession. To conclude, we stress the need for a multitemporal perspective that recognizes the significance of short-term sea-level fluctuations nested within long-term trends.

Microbial deposits in upper Miocene carbonates, Mallorca, Spain

The Santanyí Limestone, a 30–35-m thick upper Miocene limestone succession cropping out in Mallorca, contains abundant microbialite deposits, the shape, microstructure and texture of which was controlled by environmental factors: depth, energy and salinity. Three main types of microbialites are distinguished: (1) domed (DNOS) and stratiform, mostly undulate (UNOS) non-oolitic stromatolites, (2) undulate oolitic laminites (UOL) and (3) domed-oolitic thrombolites (DOTs). Based on lithofacies associations and occurrence of microbialite types, the Santanyí Limestone succession is subdivided into five stratigraphic units (I to V) separated by sharp surfaces. Within units II, III and V, the vertical evolution of microbialites was induced by changes in accommodation space/depth: (1) intertidal/very-shallow subtidal conditions at the base were induced by flooding over a wide area, (2) continued sea-level rise caused submergence to subtidal conditions, and (3) a significant bathymetric decrease created the sharp surface bounding these units. In units II and III, NOS accumulated in variable energy and depth conditions, as buildups with thick, somewhat discontinuous and mostly non-isopachous lamination, surrounded by oolitic grainstones with wave and current structures and oolitic intraclasts. In contrast, thin and generally regular and smooth lamination of NOS in unit V suggests, along with the absence of oolite grainstones and macrobiota, calm and restricted, maybe more saline, conditions. UOL, consisting of oolitic layers separated by thin micritic laminae, developed adjacent to NOS in units II and III and to DOT at the lower part of unit III, in shallow-water and low-energy conditions. Both ooids and micrite laminae have evidence for biogenesis. Micritized ooids containing microbial remains are common. Micritic laminae in UOL and the dark micritic laminae in NOS are thought to represent bacterially enhanced calcite precipitation and lithification during periods of low sedimentation. Oolitic thrombolites containing macrobiota are only present in unit III. They represent deeper and open-marine conditions affected by high-energy events, in which microbially mediated precipitation favoured microbialite accretion and lithification.

Review of the Geologic History of the Pontchartrain Basin, Northern Gulf of Mexico

Abstract The Pontchartrain Basin extends over 44,000 km2 from northern Mississippi to the Gulf of Mexico and includes one of the largest and most important estuarine systems in the United States. The basin supports a variety of environments, from woodlands in the north to wetlands in the south, and a growing socioeconomic infrastructure that has led to rapid development of the southern half of the basin over the past two centuries. To properly administer this infrastructure, managers need to understand the complex geologic framework of the basin and how it will respond to continued sea-level rise, variable rates and magnitudes of land subsidence, and human alteration of the landscape. This article summarizes the body of work that describes the regional evolution and stratigraphic architecture of the Pontchartrain Basin. The northern two-thirds of the basin is underlain by a stratigraphy of undifferentiated sands and clays deposited throughout the Plio-Pleistocene by glacially influenced rivers. These depo...

Paleoenvironmental evolution and prehistoric human environment, in the embayment of Palamari (Skyros Island, Greece) during Middle-Late Holocene

Palamari Bay is located on the northeastern coast of Skyros Island (Sporades Islands, Aegean Sea). At the northern edge of the bay a fortified prehistoric settlement is found, dated between 2800 and 1700 BC (Early Bronze Age II–Middle Bronze Age I). Detailed geomorphological mapping of the coastal alluvial plain and paleontological, micropaleontological, palynological, sedimentological and micromorphological studies of the Holocene coastal deposits have been conducted in order to reconstruct the palaeoenvironment and the landscape evolution of the broader area of Palamari Bay. Three main sedimentary units were recognized (A, B and C, from oldest to youngest). The lowermost sedimentary unit A, deposited between before 7500 and 3500 cal BP, consists of sediment deposited from high to moderate energy fresh water flows with some suspended load fallout in established water bodies. The microfauna indicates a shallow fresh water environment. However, a tendency to oligohaline conditions was established gradually. During the same period, the Palamari area was characterized by open mixed deciduous forests that gradually retreated as a possible consequence of the intensification of anthropic activity, associated with the settlement of Palamari. Indications of cultivating and grazing activities in the vicinity of the lagoon were identified, pointing to a strong human presence since the Neolithic. Between about 6000 and 3500 cal BP, the embayment was a lagoon southeasterly connected to the sea, therefore sheltered and protected from northeastern winds. The overlying unit B (ca. 3500–800 cal BP) is characterized by the dominance of brackish water microfauna, indicating a brackish stagnant shallow water depositional environment, which was periodically supplied with fresh water from the surrounding springs. As the result of the continuous sea-level rise during the Late Holocene, part of the northern headland was submerged. The decline of the Palamari settlement at the time of the establishment of Unit B might be related to the observed changes that rendered the embayment a restricted body of water. The uppermost sedimentary unit C corresponds to a backshore environment dominated by aeolian activity modified by fluvial processes.

Water Resources Policy and Practice Issues Exposed by Katrina

Water Resources Policy and Practice Issues Exposed by Katrina

Morphodynamics of Tidal Inlet Systems

In this review we discuss the morphodynamics of tidal inlet systems that are typical of barrier coasts formed during a period of continuous sea-level rise during the Holocene. The morphodynamics concerns feedbacks between three major components: the hydrodynamics of tidal currents and wind waves; the erosion, deposition, and transport of sediment under the action of the former hydrodynamic agencies; and the morphology proper, which results from the divergence of the sediment transport. We discuss the morphodynamics of the different units that characterize a tidal inlet system: the overall system, the ebb-tidal delta, the tidal channels, channel networks, tidal bars and meanders, and finally the intertidal zone of tidal flats and salt marshes. In most of these units, stability analysis is a major guide to the establishment of equilibrium structures.