Modern Shoreline Research Articles

Identifying and Constraining Marsh-Type Transitions in Response to Increasing Erosion over the Past Century

Marsh environments, characterized by their flora and fauna, change laterally in response to shoreline erosion, water levels and inundation, and anthropogenic activities. The Grand Bay coastal system (USA) has undergone multiple large-scale geomorphic and hydrologic changes resulting in altered sediment supply, depositional patterns, and degraded barrier islands, leaving wetland salt marshes vulnerable to increased wave activity. Two shore-perpendicular transect sites, one along a low-activity shoreline and the other in a high activity area of the same bay-marsh complex, were sampled to investigate how the marshes within 50 m of the modern shoreline have responded to different levels of increased wave activity over the past century. Surface sediments graded finer and more organic with increased distance from the shoreline while cores generally exhibited a coarsening upwards grain-size trend; all cores contained multiple large sedimentological shifts. 210Pb-based mass accumulation rates over the last two decades were greater than the long-term (centurial) average at each site with the fastest accumulation rates of 7.81 ± 1.58 and 7.79 ± 1.63 kg/m2/year at the sites nearest the shoreline. A shoreline change analysis of three time-slices (1848–2017, 1957–2017, 2016–2017) shows increased erosion at both sites since 1848 with modern rates of −0.95 and −0.88 m/year. Downcore sedimentology, mass accumulation rates, and shoreline change rates paired with foraminiferal biofacies and identification of local estuarine indicator species, Paratrochammina simplissima, aided in identifying paleo marsh types, their relative proximity to the shoreline, and sediment provenance. The high-energy marsh site transitioned from middle marsh to low marsh in the 1960s, and the low-energy marsh site transitioned later, at the end of the twentieth and early twenty-first century, due to its more protected location. Marsh type transition corresponds chronologically with the coarsening upwards grain-size trend observed and the degradation of Grand Batture Island; since its submergence, signatures of multiple storm event have been preserved downcore.

Jurassic paleosurfaces with fecal mounds reveal the last supper of arenicolid worms

Exceptional paleosurfaces preserving fecal casting mounds occur in the Upper Jurassic Lastres Formation of Spain. As in modern shorelines, these biogenic structures are associated with straight to sinuous-crested ripples showing the interplay of biological and physical processes in a low-energy marine environment. These trace fossils display characteristics, distribution, and densities like those of modern arenicolid populations (approximately 35 specimens per m2). Under close examination, these fecal casting mounds are morphologically undistinguishable from those produced by recent arenicolids (e.g. Arenicola marina, Abarenicola pacifica), providing evidence of the presence of these polychaetes in the Late Jurassic. As their modern counterparts, fossil arenicolids very likely modified their environment generating a seabed topography and impacting ancient benthic communities, sediment characteristics, and sediment biogeochemistry. Although the presence of oxic microhabitats and biogeochemical processes cannot be accurately measured in the fossil record, comparison with the work of modern populations allows to make inferences on sediment reworking and bioirrigation potential. In addition, association with grazing trails supports the idea of fertilization and modulation of food resources to other species. These paleosurfaces underscore the significance of high-fidelity snapshots in the fossil record (true substrates) to reconstruct past ecologies and sediment biogeochemistry. A new ichnotaxon, Cumulusichnus asturiensis n. igen. and n. isp., is defined.

Beachrocks and lithified barriers in the Gulf of Lions (western Mediterranean Sea) as new markers of the last sea‐level rise

AbstractThe Gulf of Lions shelf (southern part of the French Mediterranean coast) displays several occurrences of beachrocks, thus offering an exceptional opportunity to determine the stages of the last marine transgression. These beachrocks crop out especially on the outer shelf and near the modern shoreline. In addition, several other exposures are located on the inner shelf between 10 m and 25 m. The absence of exposure on the middle shelf (water depths of 25 to 90 m) is probably related to a higher rate of sea‐level rise. Most of the beachrocks occur at the top of two or three parallel and contiguous barriers. The seaward barriers are generally less lithified than the inner barriers. Each barrier displays an asymmetrical profile, the seaward slope being more accentuated. This gently‐dipping landward slope forms part of the outer trough resulting from resuspension due to enhanced turbulence at the barrier toe. Almost all of these beachrocks are coarse quartz‐rich sandstones and conglomerates, whose large pore space has been first filled by magnesian calcite (ca 11 mol.% MgCO3), which predominantly fills the voids. Secondary sparites or microsparites, also composed of high‐magnesian calcite, may develop locally in the last remaining voids. Finally, more rarely and very locally (for example, Pierres de Sète), a late‐stage cementation of low‐magnesian calcite is observed which expresses a brief episode of influence from a nearby freshwater groundwater table. The δ18O and δ13C values reflect the relative geochemical homogeneity of these Gulf of Lions beachrocks. However, they are quite distinct from other marine cements and, in particular, those of the eastern Mediterranean, expressing lower temperatures and a lack of influence of dissolved carbon linked to terrigenous fluxes. Based on the radiocarbon ages of these calcitic cements, this study proposes new index points on sea‐level positions in the Gulf of Lions from −95 to 108 m to −0.3 m water depths, between ca 18 583 a cal bp and 633 a cal bp.

The Late Quaternary geological history of the upper and central Sydney estuary (Australia)

Sydney estuary, on the east coast of Australia, is a small, drowned river valley with a narrow, sinusoidal channel in the upper reaches; a wide, U-shaped valley with large embayments and tributaries in the central section; and an extensive, more marine lower waterway. The estuary has experienced repeated flooding episodes during Quaternary high sea-level stands, in the absence of neotectonism. The present work considered only the upper and central estuary and therefore, potentially records the highest Quaternary sea-level stands.Valuable information on the geology and sedimentology of Sydney estuary stored in poorly-accessible grey literature has been synthesised and summarised in the current work. The first seismic-stratigraphic model was correlated to borehole data to provide a new Late Quaternary geologic history for the upper and central estuary. Limited absolute geochronological data necessitated reliance on stratigraphic correlation and conformity (uniformitarianism).A basal fluvial unit was overlain by a thick, extensive estuarine sequence, which was followed by fluvial marsh and channel sands and muds with minor wood, gravel and peat. Holocene estuarine muds mantled the upper surface of the estuary. Seismic expression was generally consistent with this lithologic subdivision. The thick estuarine unit acted as an important chronological marker horizon and played a critical role in controlling seismic interpretation throughout this part of the estuary. The paleo-estuarine sequence onlaps the modern shoreline and was most likely deposited during the Last Interglacial highstand (MIS 5.5 at 130–115 kyBP) when relative sea-level in Sydney estuary was between ＋4.5 m to ＋5.5 m above the present surface. The channel and marsh sequences were probably backstepping, progradational units in the upper estuary and possibly bayhead deltaic deposits in the central section. An erosional upper surface, as well as the stratigraphic position of these sequences, suggested deposition during a subsequent Interstadial event, most likely the MIS 5.1 at 82–87 kyBP. The knowledge generated by this study provided useful information for greater understanding of Quaternary estuarine evolution on the Australian east coast and for current and future construction projects in and across the estuary.

Coastal paleolandscapes of far southern Peru: Implications for Late Pleistocene human settlement

Archaeological evidence indicates that initial coastal settlement of western South America took place near the end of the Last Glacial Maximum (LGM) when sea level was between 40 and 100 m lower than today. Beginning around 15,000 cal BP, and for roughly the next 8,000 years, sea levels rose, eventually covering these formerly exposed and potentially human-occupied landscapes. We use bathymetric data and the reconstructed global mean sea level curve from the Last Glacial Maximum to the Holocene to describe the paleolandscapes associated with the Late Pleistocene and Early Holocene coastal occupations at five sites located in far southern Peru. We constructed cross-sections perpendicular to the modern shoreline at the various locales to determine the approximate extent of the exposed land surface and the proximity of the communities at the sites of Quebrada de los Burros, Quebrada Tacahuay, the Ring Site, Kilometer 4 (K4), and Quebrada Miraflores to the ocean and various littoral habitats. Our analysis identifies previously undocumented littoral habitats consisting of large, shallow-water bays, significant rocky headlands, and beach habitats. We propose several methods of future research to identify potentially submerged sites and the marine paleolandscape of the study region. Knowing the paleolandscapes contributes to refining Pacific coast migration and settlement models for South America.

Coseismic (20 July 2017 Bodrum-Kos) and paleoseismic markers of coastal deformations in the Gulf of Gökova, Aegean Sea, SW Turkey

The Gulf of Gökova is one of the earthquake-prone areas in the Aegean Sea and southwestern Turkey. The paleoseismology of the region is not well known because of the lack of robust field data. In this study, we focused on marine tidal notches as geomorphic markers of modern and paleoseismic deformations. Our geomorphic surveys suggest that the 20 July 2017 Bodrum-Kos Earthquake coseismically uplifted the Karaada Islet at the Turkish coast. We also provide new observations for the entire coastal area of the Gulf of Gökova. The six well preserved uplifted notch levels up to 1.5 m a.s.l. at the east of Ören town are geomorphic markers of offshore earthquakes along the northern shores. Radiocarbon dating 14C results suggest that the last 0.5 m of this uplift occurred in the last 2314 ± 32 years. The four well-preserved marine tidal notches up to 1.2 m a.s.l. indicate the earthquake-related uplift along the southern shores. There are also submerged shorelines along the southern shores at 1 m and 3–4 m below sea level as geomorphic markers of relative sea-level change. The evidence of a longer-term deformation is the presence of an uplifted wave-cut marine terrace on the southern shore. We do not have age data, but the inner edge elevation of the terrace is 238 m above modern sea level. In this study, we reveal that the shores of the Gulf of Gökova have been uplifting since the Pleistocene and Holocene, with a high probability of large magnitude offshore earthquakes occurring on normal faults very close to the modern shoreline.

Late Pleistocene-Holocene fossils from Mirim Lake, southern Brazil, and their paleoenvironmental significance: II – Mollusks

The fossil molluscan assemblages found on the shores of Mirim Lake, in southern Brazil and Uruguay, provide information about the environmental changes and geological evolution of that water body. The storm-generated shell deposits at Latinos Spit on the Brazilian shore are dominated by the estuarine bivalve Erodona mactroides, represented mostly by juveniles, and the gastropod Heleobia australis. Species previously unrecorded in this site include the marine gastropods Cylichnella bidentata, Buccinanops cochlidium and Pachycymbiola brasiliana, and the bivalves Tagelus plebeius, Ostrea puelchana, Crassostrea cf. praia, Mactra isabelleana, Anomalocardia flexuosa and Cyrtopleura costata. The two latter currently inhabit tropical areas to the north of Rio Grande do Sul, and their presence in Mirim Lake indicates average coastal water temperatures about 2–3 °C warmer than today. This condition promoted the precipitation of calcium carbonate from dissolved shells, thus cementing together sand and shells in the form of coquinas. The stratigraphic succession, OSL ages obtained in quartz sand from one coquina, radiocarbon dated shells, and δ13C and δ18O of five E. mactroides and five marine species indicate that Mirim Lake became a brackish lagoon around 7.6 ka ago, in response to the postglacial marine transgression (PMT), followed by fully marine conditions during the sea-level highstand of 6–5 ka BP. Marine influence was reduced after ∼4 ka BP as the result of sea-level fall and the closure of the connection with the ocean, related to the evolution of the sandy barrier that originated the modern shoreline. The environmental changes recorded in Mirim Lake help understand how coastal lagoons and their associated ecosystems respond to sea-level oscillations, which may be relevant to address future responses of these water bodies to the ongoing climate change.

Exploration of chronological development of coastal landscape: A review on geological and geomorphological history of Subarnarekha chenier delta region, West Bengal, India

The physiography of the alluvium coast plays a very significant role to influence the coastal morphodynamics in response to outer environmental impacts with a significant change in boundary conditions of the local area. The present study deals with the chronological development of coastal landform units in different orders of formations, their surface morphometry, drainage features, hydro-geomorphology, nature of shoreline dynamics of the coastal plain topography. The chronology of the coastal evolution is explained in this study with the application of available Optically Stimulated Luminescence (OSL) and Radio Carbon dating records of different landform units. The existing works of literature, estimation of present-day wave hydro-dynamics and estimation of the energy level along with the sediment budget of the near shores are considered to predict and establish the geological and geomorphological evolution of Subarnarekha chenier delta. The present study reveals that the chenier plain is the product of the combination of sediment discharge into the coastal zones by fluvio marine deposition with the presence of strong longshore currents at the sea face, activities of repeated coastal storms, impacts of tectonics and past sea-level fluctuations. The modern shoreline beach ridge cheniers are segmented by older distributary channels and modified by present-day coastal processes. It is the specialized coastal plain topography of alluvium surface with beach ridge chenier and swales makeup the topographic diversity of the coastal belt. There are three bifurcated ridges in the form of narrow and low height ridges in the wide valley flat surface in between Ramnagar–Deuli beach ridge section and Digha–Junput beach ridge section. The three barriers are separated by linear depressions running parallel to the present ridgelines and represent as linear tidal basins of that time.

Holocene progradation and retrogradation of the Central Texas Coast regulated by alongshore and cross‐shore sediment flux variability

AbstractFifteen transects of sediment cores located off the central Texas coast between Matagorda Peninsula and North Padre Island were investigated to examine the offshore record of Holocene evolution of the central Texas coast. The transects extend from near the modern shoreline to beyond the toe of the shoreface. Lithology, grain size and fossil content were used to identify upper shoreface, lower shoreface, ebb‐tidal delta and marine mud lithofacies. Interpretations of these core transects show a general stratigraphic pattern across the study area that indicates three major episodes of shoreface displacement. First, there was an episode of shoreface progradation that extended up to 5 km seaward. Second, an episode of landward shoreline displacement is indicated by 3–4 km of marine mud onlap. Third, the marine muds are overlain by shoreface sands, which indicates another episode of shoreface progradation of up to 5 km seaward. Radiocarbon ages constrain the onset of the first episode of progradation to ca 6.5 ka, ending at ca 5.0 ka when the rate of sea‐level rise slowed from an average rate of 1.6–0.5 mm/yr. Results from sediment budget calculations and sediment transport modelling based on reasonable estimates of an ancient shoreline shape and wave climate indicate that the first progradation was a result of sand supplied from erosion of the offshore Colorado and Rio Grande deltas. The transgressive phase occurred between ca 4.9 ka and ca 1.6 ka and coincided with a major expansion of the Texas Mud Blanket, which resulted in burial of offshore sand sources and the shoreface being inundated with mud. The second, more recent episode of shoreface progradation began ca 500 years ago with a maximum rate of ca 6 m/yr. This most recent change signals a healing phase of coastal evolution from the late Holocene transgressive event. Currently, the shoreline along the central Texas coast is retreating landward at an average rate of 0.30 m/yr, indicating that the second progradation event has ended.

Characterising the Ongole Coastal Dunefield of SE India: Formation and Temporal Constraints

Abstract The Ongole coastal dunefield (OCD) is about 20 km long and 2.5 to 3 km wide, and is located to the east of Ongole town between the mouth of the Paleru river in the south and a small creek in the north. Much of the dunefield lies 3-5 m above sea level with some large dune ridges reaching 10-12 m. The area landward of the dune field consists of an extensive marsh. Optically stimulated luminescence (OSL) dating of 12 sub-surface sediments from three sites near the western edge of the dunefield gives almost concurrent age of 5.1±0.4 ka. Radiocarbon dating of one shell from a similar location also corroborates the OSL age while the age of another shell taken closer from the modern shoreline gives a date of 3.29±0.5 ka. The age of the deposits and morphology of the dunefield indicate that it was probably initiated on some form of barrier system at the end of the Holocene transgression.

An assessment of geomorphic evolution and some erosion affected areas of Digha-Sankarpur coastal tract, West Bengal, India

The coastal sites of Ramnagar-I and Ramnagar-II Administrative Blocks (Kanthi Coastal Plain), Purba Medinipur District, West Bengal, India, reveal various morphological features, which are represented by four categories of surface formation under different processes in the present study through a contour plan with 50 cm contour interval. The first category of landform being some isolated ridges with above 10 m elevation, which are stretched out in a linear pattern parallel to the modern shoreline behind Ramnagar-Deuli beach ridge section. The second set of landforms of the area which ranges from 7 m to 10 m elevation from the MSL is extended in the form of sandy terrace and continuous sand ridge surface along the sides of the first category landform. The third category of landform is visible along the edges of the second category of continuous sand ridge topography in the form of an extensive sandy tract with the reactivated sand surface.Last category of the ancient surface with an elevation of 2.5 m to 5.0 m above MSL is also clearly visible from the wide valley flat surface depressions in between the Contai-Paniparul beach ridge section and Ramnagar-Deuli beach ridge section at present. Some crenulated ridges of sandy sediments observed in the the present contour plan, particularly along the bank of abandoned channels. These are most probably evolved in the ancient period by natural levee depositions from various fluvio-tidal channels of the coastal plain. They are also categorized into older natural levees and younger natural levees delineated from the tonal contrasts of images and field verification of lose sediments. The older natural levees represent oxidized soils and the younger one represents the grey white color of sediments. Tidal prisms are the result of spring time tidal waves, keeping pressure on the seaward sides and spill over the backshore area by entering into the tidal channels at the time of high tide in the coastal belt. The study reveal the effects of significant increase of tidal prism estimated from 1990 to 2017.

Age constraints on surface deformation recorded by fossil shorelines at Cape Range, Western Australia

Abstract Laterally continuous terraces along the western flank of Cape Range, Western Australia, record both past sea-level highstands and postdepositional vertical displacement. Four distinct fossil coral reef terraces extend nearly the entire length of the slowly uplifting anticlinal structure (∼100 km), enabling documentation of the timing and degree of deformation-induced elevation contamination of past sea-level estimates from fossil shorelines. Here, we present detailed elevations of the four terraces using differential global positioning system (DGPS) and airborne light detection and ranging (LiDAR) data sets, along with new ages for the three upper terraces. Geochemical dating using strontium isotope stratigraphy techniques revealed, from highest to lowest elevation: a late Miocene reef terrace, a late Pliocene shoreline, and a prominent mid-Pleistocene reef terrace (probably associated with the marine oxygen isotope stage 33–31 interglacial), along with a broad last interglacial (Eemian) reef terrace and lagoon, which terminate at the modern shoreline. Laterally variable elevation data integrated with newly defined ages for the terraces demonstrate a gradual and continuous relative deformation in the region that spans at least the last 6.5 m.y. and constrains the emergence of the Cape Range to sometime prior to the late Miocene. This data set also shows that the most recent interglacial shoreline has undergone <1.3 m of vertical warping, suggesting minimal deformation since deposition. By tracing relative uplift rates over multiple terraces for ∼100 km of coastline, we placed constraints on maximum relative sea level (RSL) for the older terraces. Most notably, we were able to place strict maximum RSL elevations of <+34 m on the Pliocene terrace and <+16.5 m on the mid-Pleistocene terrace, with probable RSL being somewhat lower.

Comparative morphosedimentary framework of small subtropical islands offshore Kuwait

Five small islands offshore of the State of Kuwait in the northern Arabian Gulf (Miskan, Awhah, Kubbar, Qaruh, and Umm Al-Maradem) occur in differing structural settings and have evolved in a dynamic environment of shifting fluvial depocenters, fluctuating Holocene sea level, and variable tidal conditions. As a first step in reconstructing the origin and evolution of the islands, bathymetric charts, historical photographs, topographic profiles, and sediment samples were used to investigate their geomorphology and sedimentary environments. The subaerial portion of the islands varies in area from 0.04 to 0.57 km2. The plan-shape ellipticity ranges from nearly circular (0.10) to oval-shaped (0.54). The northern two islands (Miskan and Awhah) experience mesotidal conditions and are situated on a shallow platform (<5 m below mean sea level), which is part of a larger Failaka Island structure. In contrast, the three southern sites have a microtidal regime and sit atop small isolated platforms of aggrading perched reef origin, which descend steeply to more than 20–30 m depth within 3 km of the islands. Topographic profiles indicate that island interiors are composed of beach-ridge sets, whereas modern shoreline consists of segments of beachrock platforms alternating with depositional salients and flying spits in areas of longshore transport convergence. The proportion of total shoreline length represented by exposed beachrock varies from 4 to 46%. Beach sediments consist of very coarse to medium sand and variable sorting, primarily due to the degree of attrition of bioclastic material. A simple conceptual model is proposed to describe the general evolutionary trajectory of end-member islands. Both their accretion during the Late Holocene sea-level stillstand and decadal-scale persistence of sediment transport convergence sites (salients) suggest a morphosedimentary stability of the islands in the near future.

Basin-scale stratigraphic correlation of late Pleistocene-Holocene (MIS 5e-MIS 1) strata across the rapidly subsiding Po Basin (northern Italy)

Eight stratigraphic transects, 40–140 km long reveal, for the first time on a regional scale, a comprehensive picture of facies architecture of the highly preserved Late Pleistocene-Holocene sedimentary succession from the rapidly subsiding Po Basin. Facies analysis and pollen-based correlation, supported by radiocarbon, electron-spin resonance and optically stimulated luminescence dates, enabled the attribution of distinct stratigraphic intervals to Marine Isotope Stages (MIS) 6 to 1.Basin-scale facies changes appear to have been driven mostly by glacio-eustatic oscillations falling in the Milankovitch band (∼100 ky). The MIS 5e coastal wedge was tracked continuously beneath the modern shoreline, for over 110 km along strike. Along-dip (west-east) stratigraphic correlation over 140 km revealed the characteristic landward transition from shallow-marine and coastal facies to lagoonal, swamp, and floodplain deposits.The MIS 5d-MIS 2 stratigraphic succession, up to 95-m-thick, records the stepped, basinward shift of facies related to the post-MIS 5e sea-level fall. In particular, lagoon and swamp facies mark minor transgressions (Substages 5c and 5a), whereas thick floodplain deposits and laterally extensive (>40 km) fluvial channel-belts, up to 30 m thick, characterized the glacial periods (MIS 4 and MIS 2).The Holocene (MIS 1) coastal wedge shares many similarities in terms of facies architecture and geometry with its MIS 5e counterpart, though maximum landward marine incursion during the MIS 5e transgression was 10 km farther inland (36 km inland of modern shoreline). Organic-rich (freshwater swamp) environments developed > 100 km landwards of the present-day coastline.The MIS 5e-MIS 1 succession of the Po Basin displays an exceptional thickness, up to 130 m. Minimum values (∼20 m) are recorded close to the Apennine margin and above the buried actively growing anticlines. The spatial distribution and geometry of the MIS 5e-MIS 1 strata, as well as rapidly varying subsidence rates (from 0.2 to 1.0 mm/y) reflect the strong influence of the structural setting (location of major thrust fronts) over the creation/destruction of accommodation.

Characteristics and context of high-energy, tidally modulated, barred shoreface deposits: Kimmeridgian–Tithonian sandstones, Weald Basin, southern U.K. and northern France

ABSTRACTThe influence of tides on the sedimentology of wave-dominated shorefaces has been emphasized in recent studies of modern shorelines and related facies models, but few ancient examples have been reported to date. Herein, we use a case study from the stratigraphic record to develop a revised facies model and predictive spatio-temporal framework for high-energy, tidally modulated, wave-dominated, barred shorefaces.Kimmeridgian–Tithonian shallow-marine sandstones in the Weald Basin (southern England and northern France) occur as a series of laterally extensive tongues that are 5–24 m thick. Each tongue coarsens upward in its lower part and fines upward in its upper part. The lower part of each upward-coarsening succession consists of variably stacked, hummocky cross-stratified, very fine- to fine-grained sandstone beds and mudstone interbeds that are moderately to intensely bioturbated by a mixed Skolithos and Cruziana Ichnofacies. This lower part of the succession is interpreted to record deposition on the subtidal lower shoreface, between effective storm wave base and fairweather wave base. The upper part of each upward-coarsening succession comprises cross-bedded, medium- to coarse-grained sandstones that are pervasively intercalated with mudstone-draped, wave-rippled surfaces (including interference ripples) which mantle the erosional bases of trough cross-sets. Bioturbation is patchy, and constitutes a low-diversity Skolithos Ichnofacies. Cross-bedded sandstones are arranged into cosets superimposed on steeply dipping (up to 10°) clinoforms that dip offshore and alongshore, and extend through the succession. These deposits are interpreted to record shallow subtidal and intertidal bars on the upper shoreface, which likely contained laterally migrating rip channels or formed part of a spit. The lower, upward-coarsening part of each sandstone tongue represents an upward-shallowing, regressive shoreface succession in which the internal bedding of upper-shoreface sandstones was modulated by tidal changes in water depth. The upper, upward-fining part of each sandstone tongue typically comprises an erosionally based bioclastic lag overlain by subtidal lower-shoreface deposits, and constitutes an upward-deepening succession developed during transgression.Regressive–transgressive sandstone tongues fringe the northeastern margin of the basin, which was exposed to an energetic wave climate driven by westerly and southwesterly winds with a fetch of 200–600 km. The high tidal range interpreted from the shoreface sandstone tongues is attributed to resonant amplification in a broad (150–200 km), shallow (18–33 m) embayment as the tidal wave propagated from the Tethys Ocean into the adjacent intracratonic Laurasian Seaway, of which the Weald Basin was a part.

Late Quaternary sequence stratigraphy as a tool for groundwater exploration: Lessons from the Po River Basin (northern Italy)

Sequence stratigraphy, typically used for hydrocarbon exploration in ancient strata, can be applied to late Quaternary successions to decipher complex spatial relations among their aquifers. Late Pleistocene–Holocene strata of the Po Basin were investigated using a sequence stratigraphic approach to produce a high-resolution model for guiding groundwater exploitation. Because facies tend to be diachronous across depositional basins, facies analysis was done within the conformable intervals of strata revealed by sequence stratigraphy to accurately interpret and map coeval lateral facies relations. Volumetric assessments, sand-distribution mapping, hydraulic characterization of facies, and spatial variations of hydraulic parameters revealed two aquifer systems: the lowstand systems tract (LST) and the highstand systems tract (HST) vertically separated by an aquitard, the transgressive systems tract (TST). The LST aquifer consists of amalgamated fluvial sands (average transmissivity: 3.5 E-3 m2/s [37.7 E-3 ft2/s]) with considerable width (>25 km [>16 mi]) preferentially elongated downstream. The widespread TST aquitard is dominated volumetrically (∼57%) by low-permeability estuarine deposits. The HST aquifer (average transmissivity: 5.4 E-5 m2/s [58.1 E-5 ft2/s]) is 5–10 km (∼3-6 mi) wide, elongated parallel to the modern shoreline. Sequence stratigraphic analysis at the parasequence scale revealed an almost unprecedented level of detailed insight into aquifer (or aquiclude) dimensions and the complex distribution of hydraulic parameters in the subsurface, showing that similar facies have different permeabilities depending on systems tract. In contrast, lithostratigraphic mapping obscures subsurface connectivity and directional trends and has minimal predictive power away from control. These insights should be useful for guiding correlation and mapping of the deep subsurface and for hydrocarbon reservoir modelers.

Quality characteristics of Ilmenit minerals in the south central of Vietnam by SEM and QEMSCAN analysis

Placer deposit along the South Central Coast of Viet Nam is formed by the enrichment of heavy minerals through a combination of transportation, weathering, erosion and deposition processes. Ilmenite placer forms continuously along the South Central Coast from local origin when the shoreline is far from the modern shoreline formed during the marine transgression process from the late Plestocene to Holocene. The morphological and localization characteristics of Ilmenite have been clarified on the distribution trend with SEM method combined with QEMSCAN. Meticulous research on Ilmenite's grain structure and chemical composition in the study area has shown a tendency to significantly enrich the quality of Ti placer according to the upward trend in the north-south direction. In the south, the Ilmenite placer has smaller particle size but better selective roundness and better quality than in the northern part of the study area. The enrichment of TiO2 content with increasing trend from North to South was observed due to the strong weathering process associated with ancient coastline which is very far away from current shoreline so heavy minerals are accumulates locally and light minerals are carried away. The southern region of the South Central Coast region is home to the highest gap between the ancient shoreline and the current coastline. This study has shown the trend of the quality distribution of Ilmenite as well as of other heavy minerals as the basis for future mineral exploration planning.

Indication of Holocene sea-level stability in the southern Laptev Sea recorded by beach ridges in north-east Siberia, Russia

The rapid warming of the Arctic may affect the stability of coastal geomorphological systems. Prograded sequences of wave-built deposits, so-called beach-ridge systems, preserve a proxy record of the long-term variability in the drivers of coastal evolution. Information on relative sea level (RSL), climate forcing and sediment supply can be reconstructed from these archives. Buor Khaya Bay is one of the few places along the Siberian Arctic coast where wide beach-ridge systems exist. A previously undescribed field site was surveyed in order to obtain information on the geomorphological processes along the modern shoreline under the current environmental conditions, and the characteristics of the Holocene beach-ridge deposits (e.g., elevation, sediment and age). Our data show that the system formed under storm wave/surge conditions. The beach ridges prograded ca. 1100 m between 6200 and 2600 cal yr BP, with only minor variations in surface elevation. This suggests a continuous and high sediment supply and similar storm wave run-up heights during that time. This relationship is interpreted as indicating RSL stability at a similar-to-present elevation during the period of beach-ridge formation. The hiatus in coastal progradation is concurrent with a deteriorating climate (cooling) in the Laptev Sea area and our data hence suggest increased rates of coastal change during periods of warmer climate conditions. Our study illustrates the potential of coastal sedimentary archives to provide a more complete view of the forcing, resilience and long-term evolution of unconsolidated Arctic coasts in a changing environment.

The first directly dated evidence for Palaeolithic occupation on the Indian coast at Sandhav, Kachchh

South Asia has a rich Palaeolithic heritage, and chronological resolution for this record has substantially improved over the past decade as a result of focused, interdisciplinary research at a number of key sites. Expanding the spatial diversity of dated Palaeolithic sites in South Asia grows increasingly important to examine how patterns of change through time vary within and between the region’s diverse habitats. Critically, alternate models of modern human dispersals into South Asia highlight the significance of either coastal or continental routes of dispersal, but currently no coastal Palaeolithic sites directly dating to the timeframe of human expansions are known. Our previous research in Kachchh was the first study to clearly identify the presence of Palaeolithic sites in Late Pleistocene landscapes in close proximity to the Indian Ocean coastline. Here, we present the first results of surface survey and test excavation at the site of Sandhav (Kachchh, India), approximately 25 km from the modern shoreline. We characterise the geomorphology of the landscape, highlighting multiple phases of alluvial aggradation and post-depositional carbonate formation, associated with Palaeolithic artefacts. To date, excavations have tested the uppermost Pleistocene deposit, yielding a small collection of fresh Middle Palaeolithic artefacts associated with a luminescence age dating to the first half of MIS 5 (∼114 ka), which provides a minimum age for Late Acheulean artefacts in underlying units. We discuss our findings in the context of debates surrounding the timing, lithic technologies, and ecologies associated with the expansions of modern humans into South Asia.

Geological and soil maps of the Palaeo-Agulhas Plain for the Last Glacial Maximum

The South African Cape South Coast is bordered by one of the broadest continental shelves in Africa. The Agulhas Bank, inshore shelf and presently exposed coastal plain make up the Palaeo-Agulhas Plain (PAP), though our area of study extends beyond this limit and as far inland as the first mountain belt. Quaternary sea levels have been significantly lower than at present for ∼90% of the Pleistocene, exposing a terrestrial ecosystem on what is now the submerged shelf. The presently drowned component makes up 94% of the total area of the PAP. Past work has hypothesised a contrast in character of this submerged landscape when compared to the subaerial environment. Here, we assimilate newly-acquired geophysical and geological datasets to produce geological- and soil maps from the Last Glacial Maximum on a scale of 1:750,000, covering an area of ∼55,000 km. Three broad geomorphic zones are defined, including the Western section from Cape Agulhas to Cape Infanta, the Central section from Cape Infanta to Knysna and the Eastern section extending eastward of Knysna. We demonstrate that Mesozoic sedimentary deposits crop out near the surface on this current-swept shelf and soils derived from siltstone and shale bedrock are prominent when the coast is up to 64 km distant from the modern shoreline at its maximum point. Beyond this, weathered limestone dominates the substrate sequences on the Agulhas Bank. We show that the submerged landscape was a unique terrestrial environment and that there is no exact modern-day analogue in the region other than a small (∼70 km2) area located at the edge of the Agulhas Plain near Cape Agulhas, and map major contrasts in the geological, topographic and edaphic nature of the landscape from the onshore to the offshore. The expansion of this plain is coupled with exaggerated floodplains, meandering shallowly incised rivers and wetlands. The submerged shelf is dominated by fertile soils compared to the dissected onshore belt, and extensive calcareous dunefields extending up to 10 km inland from their associated palaeoshorelines covered much of the emergent shelf. Sedimentary bedforms may have obstructed or slowed drainage as suggested by leached palaeosols and carbonate mixing observed in petrographic thin sections and grain mounts. The data show a low-relief “plains” landscape, which contrasts strongly to the topographically complex contemporary coastal foreland.