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This paper explores the resizing, reshaping and connectivity of islands by examining ongoing relations between land and sea in the context of the Channel Island of Guernsey. Ideas of materiality, temporality and vertical depth are employed to explore how contemporary tides and past sea‐level change impact island–island connections, and island–mainland connections between Guernsey and France. By focusing on the littoral zone as a space of encounter between land and sea, the paper explores some of the processes that challenge the notion of an island having fixed edges, emphasising the island's shape and size as always in flux. The paper then explores how tides alternatively reveal and hide material structures such as rocks and causeways, making the underwater scape temporally visible and differently accessible as an extension of land. It enables connections to be made and remade. This is demonstrated through the example of Guernsey and the tidal island of Lihou. The paper subsequently considers these ideas in the context of Quaternary sea‐level change. The land known as Guernsey alternated between literal island surrounded by water, and a steep‐sided plateau on the Normanno‐Breton plain, coinciding with interglacials and glacials. This connection is referred to as geologic. I argue that by acknowledging Guernsey's former visible connection with France, lack of contemporary visibility in the underwater scape does not render this a disconnection. Rather, the geologic, as further evidenced in the contemporary natural and built environment of Guernsey, continues through an underwater scape. It reappears in other Channal Islands and France, demonstrating ongoing connections at a land–sea–geologic interface. The paper argues for geology as a form of vertical depth. It calls for greater consideration of the geologic in the human geographical study of islands. [ABSTRACT FROM AUTHOR]

In submerged landscapes, distinguishing anthropogenic features versus natural ones is often challenging. We have developed a set of criteria to validate the identification of submerged anthropogenic remains that include examining the geological context, sea-level considerations, associated archaeological finds (including coastal survey), and documenting the broader archaeological context. Furthermore, our experience demonstrates that, while progress has been made in applying remote-sensing technologies to detect anthropogenic features on the seabed, there is no substitute for direct, visual assessment by an underwater archaeologist for verification of their anthropogenic status. We have applied these criteria to examine two published case studies detailing suspected anthropogenic stone features on the seabed in the Sicilian Channel. Our examination has led us to conclude that both localities are not anthropogenic features. The Pantelleria Vecchia Bank features represent natural outcrops on a submerged paleo-landscape that were shaped by depositional and erosional processes during transgression and regression periods. The suspected Lampedusa cultic site comprises natural features that are located on a submerged neo-landscape formed due to erosion and retreat of the coastal cliff since the mid-Holocene, when the sea level reached its present level. [ABSTRACT FROM AUTHOR]

Glacial isostatic adjustment (GIA) describes the response of the solid Earth, oceans, and gravitational field to the spatio‐temporal evolution of ice sheets during a glacial cycle. Present‐day vertical displacements and sea‐level changes vary throughout eastern North America in response to the melting of the Laurentide Ice Sheet following the Last Glacial Maximum. We use the open‐source software SELEN4.0 (a SealEveL EquatioN solver) to investigate the influence of GIA on vertical land motions and sea‐level changes in eastern North America. Further, we evaluate the uncertainties associated with the lithospheric thickness and viscosity structure using an ensemble modeling approach (129,956 total simulations). We identify the best‐fitting rheological profiles by comparing modeled vertical displacements to vertical velocity rates derived from Global Positioning System (GPS). We find a general pattern of subsidence (causing accelerated relative sea‐level rise) in the eastern United States region and uplift (causing relative sea‐level fall) in the eastern Canada region consistent with previous studies for two tested ice sheet models (ICE‐6G(VM5a) and ICE‐7G(VM7)). Overall, we find lower rates of modeled vertical displacement using ICE‐6G(VM5a) compared with ICE‐7G(VM7), which produces lower residuals when compared with the GPS‐derived vertical velocity rates. Our ensemble analysis identifies adjustments to the nominal VM5a and VM7 viscosity models that improve fits to the GPS‐imaged vertical velocity rates throughout eastern North America and on the North American Atlantic Coast. The differences in our best‐fitting models for inland versus coastal regions highlight the importance of exploring lateral viscosity variations for GIA modeling throughout North America and elsewhere. Plain Language Summary: Approximately 19,000–26,000 years ago a massive ice sheet covered Canada and a portion of the northern United States. We investigate the Earth's surface movements following the melting of the ice sheet throughout eastern North America. Through computational modeling, we predict rates of vertical land motion and relative sea‐level change throughout eastern North America. We see a general pattern of downward movements (causing relative sea‐level rise) in the eastern United States region and upward movements (causing relative sea‐level fall) in the eastern Canada region. However, modeled rates vary depending on the assumptions about Earth's internal structure. We test different models of Earth structure, based upon variations of the Earth structure profiles paired with two published models of ice sheet history. Our different models vary the lithospheric thickness and radial viscosity structure (viscosity varies by depth only). By comparing the rates of Earth's surface movements generated by these different models to published data of observed vertical land motions, we determine which Earth structure models produce the best fits to the published observations. Differences in the best‐fitting Earth structure for different regions of eastern North America indicate the importance of exploring Earth structures that vary both radially and laterally. Key Points: Modeled present‐day vertical displacement and sea‐level change rates fit observed data better using ICE‐6G(VM5a) compared with ICE‐7G(VM7)Ensemble analysis suggests adjustments to VM5a and VM7 viscosity models improve fits to geodetic data throughout eastern North AmericaRegional differences in best‐fitting Earth structure support the adoption of lateral viscosity in glacial isostatic adjustment modeling [ABSTRACT FROM AUTHOR]

Coastal sediment stratigraphies, their physical properties and microfossil assemblages are commonly used to reconstruct sea-level change. However, coastal sediments are affected by tidal, wave, aeolian, and overwashing processes at a range of elevations both within and above the tidal frame which means that their sea-level signatures may not always be clearly identified. Saltmarsh is a common coastal sedimentary environment along the Atlantic-facing coastline of northwest Ireland where bedrock headlands and an archipelago of small offshore islands have provided accommodation space for aggradational Holocene sediment sequences. A 2.85 m-long sediment sequence was investigated at Cloughglass, northwest Ireland. This shows weathered granite bedrock overlain by glacigenic cobbles and then in situ Pinus stumps within humified peat that is exposed in the upper foreshore. Above this, organic-rich and laminated saltmarsh sediments are arranged in packages (20–80 cm thick) bounded by undulating erosional surfaces. The saltmarsh sediments are unconformably overlain by a palaeosol (30 cm thick) and 1.5 m of recent dune sand. Sediment samples were removed at 5 cm intervals through the entire logged section and analysed for grain size properties, combustible organic content, CaCO 3 content, and microfossil assemblages. Five samples were dated by the AMS 14C method. Results show organic sediment accumulated around the pine tree stumps at ∼4400 cal yr BP but that later sedimentation was episodic, as evidenced by erosional surfaces throughout the saltmarsh part of the succession that may correspond to episodic storms or flood events. Three microfossil biostratigraphic zones are identified which broadly correspond to the sediment stratigraphy. The lowermost zone has poor preservation. The middle zone contains several halophytic species in low abundance but is dominated by the ubiquitous diatom Achnanthidium minutissimum. The uppermost zone is less diverse, with low but consistent abundance of predominately freshwater species and those that can tolerate brackish conditions. Integrating these results suggests that late Holocene coastal erosion and sea-level rise brought the coastline closer to the site over time, with a concomitant increase in wave and tidal influence as recorded in both sedimentary structures and biofacies. Subsequently, the land surface became stabilized with development of a dune palaeosol and decreased abundance of A. minutissimum. This evolutionary history reflects changing patterns of wave exposure and sediment supply as a result of changes in sand accumulation around the surrounding bedrock islands. Thus, the coastal stratigraphy more strongly reflects local sediment dynamics and accommodation space rather than regional sea-level change in the late Holocene. [ABSTRACT FROM AUTHOR]

Cuttings and logs from four boreholes in the Mediterranean Sea, offshore the northwestern side of the Nile Delta, Egypt (30°00'–30°24' N, 31°18'–31°30' E), were examined lithostratigraphically, biostratigraphically and paleoenvironmentally. Five planktonic foraminiferal zones were determined assigning the studied boreholes to be late Miocene-Early Pliocene in age. These zones are Globorotalia mediteraneaneana Zone Sphaeroidinellopsis seminulina Zone, Globorotalia margaritae margaritae Zone, Globorotalia puncticulata Zone and Globorotalia inflate. Studying benthonic foraminifera indicated a general shallowing upward trend in all boreholes and tracking the distribution of the foraminiferal assemblages by counting the total number of foraminifera and planktic/benthic ratios provide a history of the progression of deltaic facies with secondary cycles of sea-level change. [ABSTRACT FROM AUTHOR]

Nearshore incised valleys are important conduits for the transport of sediment, nutrients, pollutants and organic carbon from the continents to the sea. Therefore, it is essential to understand the autogenic evolution of deltas confined within incised valleys and how such evolution is affected by relative sea‐level rise. To date, limited research has focused on how deltas constrained by incised valleys or other forms of antecedent topography respond to rising sea level. An existing theory of autostratigraphy envisages scenarios in which two‐dimensional or unconfined three‐dimensional fan deltas can experience three evolutionary stages under constant rates of relative sea‐level rise and sediment supply: progradation, autoretreat and post‐autobreak transgression. In this work, an integrated study of geometric numerical models and physical experiments is undertaken to investigate autostratigraphic delta evolution for a variety of incised‐valley geometries, under conditions of constant rates of relative sea‐level rise and sediment supply. Results indicate that interplays of antecedent topography (valley geometries) and sediment mass balance expressed in resultant deltaic geometries can result in autogenic changes in shoreline dynamics and river avulsion frequency on deltas. The following primary findings arise. (i) Compared to valleys with rectangular and trapezoidal cross‐sectional profiles, valleys with triangular cross‐sections tend to contain deltas that experience faster rates of progradation, autoretreat and post‐autobreak transgression under rising sea level, and exhibit a more prominent convex‐seaward shoreline trajectory. (ii) The shoreline trajectory is also related to delta topset geometry, becoming more convex‐seaward under decreasing topset slopes. (iii) River avulsion frequency on deltas with rising sea level varies markedly across valleys with different geometries, even under the same rate of relative sea‐level rise; this is attributed to the difference in temporal evolution of shoreline migration for different valley geometries and the resultant difference in the delta topset aggradation. This study highlights complexities in responses of sedimentary systems under the confinement of different topographic configurations that have hitherto largely been overlooked in sequence‐stratigraphic models. The findings provide insight into future shoreline behaviour and river avulsion hazard on confined deltas, and for decoding the stratigraphic record. [ABSTRACT FROM AUTHOR]

This study presents the historical sequence of the inter-relationship between climate, sea-level change, hydromorphology, and the society in the "Delta of Neretva", Croatia. This study aims to support future-oriented planning, since the cumulative impact of climate and mean sea-level changes on the delta hydromorphology and socio-economy is very uncertain and difficult to predict. In particular, the sustainability development of the Delta of Neretva requires a long-range strategy that is complicated to outline. In the proposed approach, hydromorphology is used as a sustainability indicator since it considers both the physical character and water content of the delta and looks at how nature and human activities influence the biophysical system and economy. The direction of delta progression and persistence of socio-hydromorphology are evaluated with the assessment of system entropy generation considering the simple system state function. Such a method overcomes the difficulties posed by top–down and bottom–up approaches, making future scenarios and cumulative impacts visible and understandable to stakeholders. The historical co-evolution results indicate that the delta in the future could become a submerged estuary (rias), that is, a sea bay as a result of the subsequent delta progradation caused by an MSL rise, similar to the progradation during the Holocene, and decreasing sediment deposition due to anthropologic processes in their watershed. Technology (policy) assessment suggests that adaptation measures that gradually support environmental security and sustainable livelihoods, i.e., increase natural order at a society-acceptable cost, are preferable. [ABSTRACT FROM AUTHOR]

Sea‐level change threatens the U.S. East Coast. Thus, it is important to understand the underlying causes, including ocean dynamics. Most past studies emphasized links between coastal sea level and local atmospheric variability or large‐scale circulation and climate, but possible relationships with local ocean currents over the shelf and slope remain largely unexplored. Here we use 7 years of in situ velocity and sea‐level data to quantify the relationship between northeastern U.S. coastal sea level and variable Shelfbreak Jet transport south of Nantucket Island. At timescales of 1–15 days, southern New England coastal sea level and transport vary in anti‐phase, with magnitude‐squared coherences of ∼0.5 and admittance amplitudes of ∼0.3 m Sv−1. These results are consistent with a dominant geostrophic balance between along‐shelf transport and coastal sea level, corroborating a hypothesis made decades ago that was not tested due to the lack of transport data. Plain Language Summary: Sea‐level rise is an imminent threat to coastal communities worldwide, including the U.S. East Coast. Therefore, it is crucial to understand the processes driving regional sea‐level change. While past studies documented how coastal sea level may be influenced by large‐scale ocean circulation, less attention has been paid to the role of more local currents over the shelf and slope. Here we explore the relationship between coastal sea level along the northeastern U.S. and the Shelfbreak Jet, a current that flows along the shelfbreak from the Labrador Sea to Cape Hatteras (North Carolina). From 7 years of in situ data of both current velocities and water levels, we see that as coastal sea level rises, Shelfbreak Jet transport increases westward (and vice versa) on timescales of days to weeks. Our results lay the groundwork for understanding relationships between coastal sea level and local ocean dynamics elsewhere. Key Points: Daily Shelfbreak Jet transports and Southern New England coastal sea levels are anti‐correlated during 2014–2022The observed relationship between these two variables is consistent with geostrophic balanceFor this region, coastal sea levels are more sensitive to local ocean dynamics than to large‐scale circulation [ABSTRACT FROM AUTHOR]

Simple Summary: This study focuses on the assassin bug Sycanus bifidus, a widespread species in southern China, by analyzing its genetic data to trace how the Pleistocene's climate and geography influenced its distribution and evolution. There are two main genetic groups, which suggests that past climatic conditions and sea-level rises, especially concerning Hainan Island, profoundly impacted the spread and distribution of these bugs. This study's insights into the assassin bugs' historical population dynamics and adaptations to environmental changes emphasize the role of historical climatic fluctuations in shaping the distribution of species. The assassin bug Sycanus bifidus has a wide distribution across southern China. This study explored its distribution and evolution by analyzing mitochondrial and nuclear ribosomal RNA genes, revealing how Pleistocene climate and geological changes shaped its phylogeography. We identified two main clades, A and B, that diverged in the Middle Pleistocene. Hainan Island's populations form a unique group within Clade A, suggesting that the Qiongzhou Strait served as a dispersal corridor during glaciation. Rising sea levels likely separated the Hainan population afterward. Ecological niche modeling showed that both populations have been viable since the last interglacial period, with demographic analyses indicating possible expansions during the Middle and Late Pleistocene, driven by favorable climates. This study highlights the significant effects of Pleistocene sea-level and climatic changes on the distribution and evolution of S. bifidus in China. [ABSTRACT FROM AUTHOR]

Archaeological evidence for local environmental change is obscured by the tendency for humans to remove natural resources from places of procurement and deposit them elsewhere, sometimes at great distance. This is especially problematic for changes in relative sea level, which clearly affected the inhabitability of low-elevation coastal landforms but not necessarily the regional availability of resources of cultural or economic value. Needed are proxies for relative sea level from non-dietary taxa. One genus of terrestrial snails, Truncatella, offers good potential in this respect because of its specific niche at the interface between seawater and land. However, like food resources displaced by people, Truncatella shells are displaced by storms and redistributed landward of the coastline. Distinguishing between autochthonous and allochthonous deposits is essential to inferring relative sea level from the occurrence of this taxon alone. To this end, assemblages of Truncatella shell from stratified sites along the north Gulf Coast of Florida, USA are compared to associated archaeological snails of other taxa and to snail shells from the wrack of proximate foreshores to infer changes in relative sea level over the past four millennia. Variation in the morphology of shorelines and in the accumulation rates of archaeological midden mitigates any direct relationship between terrestrial snail frequencies and sea level, but the results of this study suggest that our approach can be applied to other non-dietary taxa occupying marginally terrestrial niches to refine estimates for sea level derived from the sedimentary records of geological cores. [ABSTRACT FROM AUTHOR]

Abstract Sea‐level change threatens the U.S. East Coast. Thus, it is important to understand the underlying causes, including ocean dynamics. Most past studies emphasized links between coastal sea level and local atmospheric variability or large‐scale circulation and climate, but possible relationships with local ocean currents over the shelf and slope remain largely unexplored. Here we use 7 years of in situ velocity and sea‐level data to quantify the relationship between northeastern U.S. coastal sea level and variable Shelfbreak Jet transport south of Nantucket Island. At timescales of 1–15 days, southern New England coastal sea level and transport vary in anti‐phase, with magnitude‐squared coherences of ∼0.5 and admittance amplitudes of ∼0.3 m Sv−1. These results are consistent with a dominant geostrophic balance between along‐shelf transport and coastal sea level, corroborating a hypothesis made decades ago that was not tested due to the lack of transport data.

In submerged landscapes, distinguishing anthropogenic features versus natural ones is often challenging. We have developed a set of criteria to validate the identification of submerged anthropogenic remains that include examining the geological context, sea-level considerations, associated archaeological finds (including coastal survey), and documenting the broader archaeological context. Furthermore, our experience demonstrates that, while progress has been made in applying remote-sensing technologies to detect anthropogenic features on the seabed, there is no substitute for direct, visual assessment by an underwater archaeologist for verification of their anthropogenic status. We have applied these criteria to examine two published case studies detailing suspected anthropogenic stone features on the seabed in the Sicilian Channel. Our examination has led us to conclude that both localities are not anthropogenic features. The Pantelleria Vecchia Bank features represent natural outcrops on a submerged paleo-landscape that were shaped by depositional and erosional processes during transgression and regression periods. The suspected Lampedusa cultic site comprises natural features that are located on a submerged neo-landscape formed due to erosion and retreat of the coastal cliff since the mid-Holocene, when the sea level reached its present level.

The late Asbian appears to mark the initial, well‐documented, onset of far‐field glacio‐eustatic changes in equatorial Mississippian strata. This work unravels the nature of cyclicity in upper Asbian shallow marine carbonates, using a combination of petrographic study, rock magnetic proxies and astrochronological testing on samples from the Trowbarrow section, NW England. Rock magnetic data express the content of two types of siliciclastic sources; a marine‐delivered magnetite‐dominated source, and an eolian‐delivered, hematite‐dominated source. The eolian‐sourced material generally peaked during regressive and low‐stand parts of the carbonate rhythms. Astrochronologic testing methods based around the average spectral misfit and TimeOpt methodology show the magnetite abundance proxies are principally carrying the astronomically forced signal. Two likely sedimentation rate models are derived from the five better magnetic proxies using evolutive methods. In addition, a set of three likely major hiatus levels are inferred in the sedimentation rate models, based on testing possible major hiatus scenarios with TimeOpt methods, using eccentricity modulation. From these, using the three best proxies, an average astrochronologic duration for the Trowbarrow section suggests a late Asbian duration of 1976 ± 86 kyr (1σ), and a basal late Asbian age of 334.48 ± 0.35 Ma (2σ). Coupled atmosphere‐ocean models for the late Paleozoic, suggest that lows in short eccentricity correspond to glacials, when inferred delivery of siliciclastic sediment to the carbonate ramp is generally at a maximum. The glacial and lower sea‐level intervals also coincide with maximum delivery of eolian siliciclastics, likely linked to increased aridity and less vegetation cover on adjacent and distal parts of Laurentia. Plain Language Summary: Around 332–333 million years ago changes in sea‐level driven by changes in polar ice volume were an important control on the sedimentation patterns through time in carbonates from low paleolatitudes. Understanding the pacing of these changes has implications for timescales and paleoceanographic processes. These cyclical changes in carbonate lithology are related to changes in magnetic properties within the late Asbian (late Visean) section at Trowbarrow in NW England. The magnetic changes principally express differences in the small content of silica‐based clastics, but also reflect changing Fe‐oxide mineralogy between times of hematite‐rich and magnetite‐rich clastic input. The changes are responding to differences in eolian delivery and marine dispersal of the clastics. Eolian delivery of clastics was at its peak near sea‐level lowstands, when nearby terrestrial systems were the most arid and supplying the most dust. Statistical assessments show that the magnetite abundance signal principally expresses changes in astronomical eccentricity. Primarily using the expected eccentricity pacing, two age models are constructed, which includes three levels of detectable hiatus in the section. Using these two age models and the three best magnetic proxies, the average late Asbian duration is 1976 ± 86 kyr, with the base of the late Asbian at 334.48 ± 0.35 Ma. Key Points: Rock magnetic properties show the included siliciclastics are from hematite‐rich eolian dust and marine‐dispersed sourcesThe magnetite mineral abundance proxies principally carry the primary eccentricity‐driven astronomical signalAn astrochronology for the late Asbian indicates its duration is 1976 ± 86 kyr [ABSTRACT FROM AUTHOR]

The Cryogenian period of the Neoproterozoic was marked by two Snowball Earth glaciations that bookended a non-glacial interval that lasted roughly 10 million years. The break-up of Rodinia in the early Neoproterozoic gave rise to numerous rift basins whose time-varying redox dynamics, linked to marine productivity and biogeochemical cycling, were likely controlled by varying degrees of basin restriction in response to sea-level change. Those drivers were associated with both global glaciations (Sturtian deglaciation and the possibly early onset of the Marinoan) and local tectonics (regional basin uplift/subsidence). To explore these relationships, we focus on the Datangpo Formation, an exceptional shale sequence deposited in a marginal rift basin in South China. The Datangpo succession comprises lower organic-rich black shales and upper organic-lean gray shales/siltstones. As elucidated by our integrated data, the former were deposited in H 2 S-rich, deep-water settings underlying highly productive surface waters. We attribute this productivity to elevated nutrient supplies replenished from the open ocean following a sea-level rise, as augmented by high terrestrial input of phosphate in the wake of the Sturtian deglaciation. By contrast, the gray shales/siltstones were associated with relatively shallow deposition in an oxic/suboxic water column with suppressed primary production. The major driver of this dramatic shift in water chemistry may lie with a greater extent of basin isolation and the corresponding reduction in nutrient fluxes from the global ocean due to a significant sea-level fall—possibly linked to regional basin uplift. At this time, the basin experienced an elevated influx of detrital clays and organic material, perhaps triggered by lower sea level. Surprisingly, we found that euxinic conditions prevailed in the water column for a substantial period following the onset of more isolated conditions. This relationship can be attributed to redox-dependent phosphorus cycling. Specifically, H 2 S-replete conditions facilitated regeneration of bioavailable phosphorus, initiating a positive feedback that allowed the persistence of anoxic waters. This study advances our understanding of nutrient cycling and biogeochemical evolution during the Cryogenian under the influence of large-scale sea-level fluctuations and associated time-varying connectivity to the open ocean that must have been common in many basins at this time. Furthermore, our study sheds novel light on the iron proxy and early sulfur cycling. Almost all of the terrestrial silicate-bound iron was likely converted into highly reactive phases due to strong chemical weathering, while sulfur data revealed isotopic stratification in the wake of Sturtian deglaciation, with important messages for interpretations of analogous data in the aftermath of other climate upheavals in Earth history. [ABSTRACT FROM AUTHOR]

Beach ridges are depositional features that allow reconstruction of past sea-level variations, sediment dynamics, and storm activity. However, there are still very few systematic studies focusing on beach ridges available from the Gulf of Thailand. Along the east coast, satellite images provide evidence of beach ridges in the Chanthaburi Province, extending as far as 6 km inland, oriented parallel to the current coastline. These can be divided into a set of landward ridges (5.3–6.0 km inland) and seaward ridges (0.4–1.8 km inland) that are separated by an arm of the Chanthaburi estuary. Optically stimulated luminescence dating of 26 sand samples from 12 pits of ridge profiles suggests that the landward set of beach ridges formed ca. 3500 yr ago, while the seaward set of ridges formed between ca. 2100–1200 years ago, which also includes the modern active beach. It appears that the landward set of beach ridges developed during a period of relatively stable sea level followed by a rapid regression presently occupied by the arm of the Chanthaburi estuary. The seaward set of beach ridges apparently reflects a millennium of slowly retreating coastline until the modern beach ridge formed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Effect of the supercontinent cycle (SC) on the longest-term sea level is studied. • Various scenarios of the SC are tested in a conceptual model of continental drift. • Plate flattening effect is essential to recover realistic sea-level fluctuations. The longest-term (first-order) sea-level change is considered to be within ∼ 200–300 million years, which is roughly half or less of the period of the supercontinent cycle of ∼ 500–700 Myr. It is recognized that the assembly of supercontinents involves either the closure of the "interior ocean" that resulted from the breakup of the supercontinent or the closure of the "exterior ocean" that surrounded the supercontinent. The former process is termed "extroversion," while the latter is termed "introversion," both of which are an end-member scenario of the supercontinent cycle. A "combination" process is also proposed to explain the complex behavior of continental drift on the actual Earth. Despite recent advances in a time-dependent mantle convection model, some difficulties still remain in self-consistently recovering plate tectonics and continental drift of the past Earth. Therefore, it is worth addressing the fundamental physics of the effects of the history of plate motion and the associated continental drift on the longest-term sea-level change from the perspevtive of the supercontinent cycle in a timescale of the order of 100 million years. In this study, a simple conceptual model of mantle convection with various supercontinent cycle processes was constructed, and the effects of the supercontinent cycle on the longest-term sea-level change were addressed. The sea-level change is estimated from bathymetry over the oceanic plates under different free parameters that control the fluctuation of the sea-level change. The present analytical results suggest that the asymptotic bathymetry due to the plate flattening effect of oceanic plates in the exterior and interior oceans is essential to recover the realistic magnitude of sea-level fluctuations that is comparable to the sea-level curve of the past Earth. In addition, the absolute volume change in the seawater due to its recycling into the mantle may be important to fit the observed sea-level curves from stratigraphic studies since 200 million years ago. [ABSTRACT FROM AUTHOR]

Sea-level rise directly caused by climate change is impacting coasts around the world and lowlying islands, requiring a continuous accurate monitoring. We analyze the sea-level data observed by 20 tide gauges located in the east coast of the United States of America (USA) over the period January 1972 to December 2021 by using an open-source toolbox SLR_APP. After mitigating noise using Principal Component Analysis (PCA) and Independent Component Analysis (ICA) method, we estimate the trend change and its uncertainty of sea-level considering the stochastic noise properties of the observations. The sea-level estimates and associated uncertainty are smaller than the raw observations after the noise reduction. Our results show that: the average values of the absolute trend change are 1.51 % and 0.82 %, and the mean trend uncertainty are reduced by 44.78 % and 21.26 % after PCA and ICA noise reduction, respectively. We conclude that PCA method performs better than ICA especially in reducing the associated trend uncertainty of the sea level change. Improving the sea-level rise estimation and prediction contribute globally to enhance public safety, in particular for the coastal communities. [ABSTRACT FROM AUTHOR]

Coastal East Africa has undergone massive transformations through the Late Holocene, with a combination of changes in sea level, increasing human settlement, and ensuing use of coastal resources. A comprehensive multi-proxy analysis, including pollen, phytolith, charcoal, stratigraphy, particle size, and geochemical data from sedimentary cores extracted from mangrove ecosystems combined with soils from archaeological contexts, provided valuable insights into vegetation dynamics, environmental changes, and human interactions within the mangrove ecosystem of Songo Mnara Island, Tanzania over the last 2590 BCE (4540 cal yr BP). The bottommost layers indicate a lack of vegetation, as deduced from the presence of coral rags and high calcium and carbonate content, possibly due to high mid-Holocene sea-level. Evidence of mangrove taxa suggests a decrease in sea level, enabling the establishment of mangroves from around 2590 BCE. A brief period of sea-level rise occurred between 90 BCE and 320 CE before sea-level fell until 1570 CE. Significant evidence of human activity is recorded from around 1400 CE indicated by increased charcoal, crop phytoliths, and evidence of marine resource utilisation. The timing of this human-environment interaction is also linked to the time of lower sea level. However, there was evidence suggesting human abandonment of the island from around 1500 CE. This coincided with a subsequent rise in sea levels and potentially prolonged drought conditions spanning from 1570 to 1700 CE. These factors likely contributed to a shortage of food resources in the area, impacting both agricultural practices due to the scarcity of natural freshwater and the accessibility of marine food resources. From 1700 CE to the present, fluctuations in sea level have been observed, with a signal of recent sea-level rise in tandem with shifts in mangrove, terrestrial herbaceous taxa and fire activity.The low sedimentation rates within mangrove areas suggest that the mangroves on Songo Mnara Island may not keep pace with the current rate of sea-level rise.

This study presents the historical sequence of the inter-relationship between climate, sea-level change, hydromorphology, and the society in the “Delta of Neretva”, Croatia. This study aims to support future-oriented planning, since the cumulative impact of climate and mean sea-level changes on the delta hydromorphology and socio-economy is very uncertain and difficult to predict. In particular, the sustainability development of the Delta of Neretva requires a long-range strategy that is complicated to outline. In the proposed approach, hydromorphology is used as a sustainability indicator since it considers both the physical character and water content of the delta and looks at how nature and human activities influence the biophysical system and economy. The direction of delta progression and persistence of socio-hydromorphology are evaluated with the assessment of system entropy generation considering the simple system state function. Such a method overcomes the difficulties posed by top–down and bottom–up approaches, making future scenarios and cumulative impacts visible and understandable to stakeholders. The historical co-evolution results indicate that the delta in the future could become a submerged estuary (rias), that is, a sea bay as a result of the subsequent delta progradation caused by an MSL rise, similar to the progradation during the Holocene, and decreasing sediment deposition due to anthropologic processes in their watershed. Technology (policy) assessment suggests that adaptation measures that gradually support environmental security and sustainable livelihoods, i.e., increase natural order at a society-acceptable cost, are preferable.

Cambrian System at the Shatan Section in northern Henan, North China, consists of sedimentary successions of tidal flat and shallow-water carbonate platform facies. Data of carbon isotope (δ13Ccarb) from this section reveals five positive δ13Ccarb (Pst-l–Pst-5) and five negative δ13Ccarb excursions (Nst-l–Nst-5). In the positive excursions, δ13Ccarb rises to 0.88‰, 1.05‰, 2.04‰, 1.00‰ and 2.97‰, respectively, while in the negative excursions δ13Ccarb drops to −8.00‰, −3.50‰, −1.00‰, −0.33‰ and around −2.00‰, respectively. On the basis of chronostratigraphy of Cambrian, the most remarkable carbon isotope excursions can be correlated regionally and globally. In addition, one second-order and ten third-order sequences have been recognized at this section. Correlating third-order sequences and chemostratigraphy indicates that carbonates from the basal part of the transgression system tract (TST) and the upper part of the high-water system (LHST) generally have lighter δ13Ccarb values, whereas massive carbonates with microbialite from the lower part of the high-water system tract (EHST) usually have heavier δ13Ccarb values. The association of δ13Ccarb values with sea-level fluctuations suggests that the positive carbon isotope excursions or high δ13Ccarb values may have been caused by an increase in the marine primary productivity in response to maximum seawater flooding during the transgression. [ABSTRACT FROM AUTHOR]

The paper deals with results of geological and geophysical study of the East Siberian Sea coastal areas are reported. Research activities started in 2018 in the frame of the State Geological Mapping Project (GK-1000/3) and continued in 2022 under support of the Russian Science Foundation. A seismo-stratigraphic scheme of the Quaternary sediment sequence has been compiled, and a conception of the paleogeographical evolution in the Late Pleistocene–Holocene has been proposed. [ABSTRACT FROM AUTHOR]

The Paleoproterozoic was an important stage in the evolution of life and the environment during Earth's history. Understanding astronomical rhythms and solar system behavior in the Paleoproterozoic is often challenging. In this study, ∼190 m high‐resolution magnetic susceptibility (MS) and ∼30 m high‐resolution Ba/Al data are used to conduct cyclostratigraphic analyses of the Chuanlinggou Formation in the Yanliao Rift, North China Craton. Spectral analysis indicates significant peaks at wavelengths of 12.1–7.7, 2.8–1.6, 0.58–0.33, and 0.29–0.22 m, which matches well with the astronomical cycles predicted by Waltham for ∼1,640 Ma. A 9.9‐Myr astronomical time scale is constructed by tuning the MS series to the 405‐kyr‐long eccentricity cycle. The geological records show ∼1.56‐Myr very long eccentricity period and ∼1.0‐Myr very long obliquity period (close to 3(s4 − s3) − 2(g4 − g3) = 0) in the Paleoproterozoic. The sea‐level change curve predicted by dynamic noise models reveals a significant ∼1.0‐Myr period, indicating that sea level fluctuation may have been driven by the very long obliquity period. Bayesian inversion is used to further estimate the evolution of the ancient Earth‐Moon orbital parameters, constraining a precession rate of 87.14 ± 0.25 arcsec/year and an Earth‐Moon distance of 341,530 ± 390 km for the Paleoproterozoic Changcheng System. These results indicate that astronomical orbital forcing may have played an important role in climate and sea‐level changes in the Precambrian, increasing the understanding of the fundamentals of global sea level fluctuations, orbitally driven mechanisms and the chaotic behavior of the Precambrian solar system. Plain Language Summary: Orbital parameters and long‐term behavior have changed during geological history. For the first time, we found new resonance states between Mars and Earth (i.e., a very long eccentricity period of ∼1.56 Myr and a very long obliquity period of ∼1.0 Myr) from the geological records of the Paleoproterozoic Changcheng System in the Yanliao Rift of the North China Craton. The reconstructed sea‐level change curve shows a significant ∼1.0‐Myr period, indicating that sea level fluctuations may have been driven by the very long obliquity period in the Precambrian. The orbital parameters in the Paleoproterozoic are recovered using Ba/Al ratios, and the calculated precession constant is 87.14 ± 0.25 arcsec/year. The Earth‐Moon distance was 341,530 ± 390 km, and the length of day (LOD) was 18.06 ± 0.05 hr, which indicates that lunar recession may have been slower in deep time. These results increase the understanding of astronomical rhythms and the chaotic behavior of the solar system in the Precambrian. Key Points: A new Earth‐Mars resonance state (3(s4 − s3) − 2(g4 − g3) = 0) is revealed from the Precambrian geological recordsThe ∼1.0‐Myr very long obliquity period significantly affected sea level fluctuations under the Mesoproterozoic greenhouse climate [ABSTRACT FROM AUTHOR]

We present evidence of sea-level changes over the past 15,000 years from dating sandy beach sediments in Nakhon Si Thammarat province. First, we classified various types of coastal landforms from satellite images. The orientations of beach ridges and old lagoons are very important to understanding the evolution of sea-level rise and fall. In this area, there were two groups of old sandy beaches: (i) the inner beach, and (ii) the outer beach, which were separated by old lagoons. Then, nine quartz-rich samples were analyzed using Optically Stimulated Luminescence analysis to estimate the ages of deposition. The results supported the concept that the inner series of old sandy beach deposits indicated the onset of sea-level regression occurring approximately 15,000 years ago (YA). Sea level still stands, derived from the erosion of the beach ridge and deposition of old tidal flats, were estimated to be between 10,000 and 4,000 YA. The old lagoon showed a period of being covered from approximately 4,000 to 2,000 YA before outer beach ridge deposition some 2,000 to 400 YA during sea-level regression. Considering these measured ages, the sandy beach sediments yield the oldest range of depositional ages among all the Holocene beach deposits in southern Thailand.

The assassin bug Sycanus bifidus has a wide distribution across southern China. This study explored its distribution and evolution by analyzing mitochondrial and nuclear ribosomal RNA genes, revealing how Pleistocene climate and geological changes shaped its phylogeography. We identified two main clades, A and B, that diverged in the Middle Pleistocene. Hainan Island’s populations form a unique group within Clade A, suggesting that the Qiongzhou Strait served as a dispersal corridor during glaciation. Rising sea levels likely separated the Hainan population afterward. Ecological niche modeling showed that both populations have been viable since the last interglacial period, with demographic analyses indicating possible expansions during the Middle and Late Pleistocene, driven by favorable climates. This study highlights the significant effects of Pleistocene sea-level and climatic changes on the distribution and evolution of S. bifidus in China.

ABSTRACTWe present and discuss the results of a geomorphological and geological study aimed at reconstructing the Plio-Quaternary evolution of the NW Sicily coastal belt , a low strain rate region in the central Mediterranean Sea.We performed morphometric and field analysis of Quaternary marine terraces extracting more than 300 shoreline location points subdivided into six orders. The obtained dataset was validate by investigating the morphological changes along topographic profiles and comparing the extracted locations and elevations with the stratigraphic boundaries in the Plio-Quaternary units.We distinguished two contiguous coastal sectors characterized by different paleo-shoreline elevations and Plio-Quaternary evolution, whose estimated uplift rates fit well with the well-known, regional eastward uplift rate increase along the Northern Sicilian continental margin.Obtained results, summarized in a geomorphological map and a morpho-evolutionary model, provide new valuable data to characterize the active deformation processes and the seismotectonic setting in this critical sector of the Africa-Europe plate boundary.

The 8.2 ka climate event is the most significant North Atlantic cooling event during the Holocene. Freshwater pulses from the melting Laurentide Ice Sheet draining into the North Atlantic Ocean are commonly thought to be its cause by perturbing the Atlantic Meridional Overturning Circulation. The timing, magnitude and number of freshwater pulses, however, remain uncertain. This is problematic for predicting future climate scenarios because it prevents rigorous testing of coupled ocean–atmosphere climate models against an otherwise excellent test case of climate effects of meltwater inputs into the North Atlantic. To address this knowledge gap, we present a high-resolution relative sea-level record from the Ythan Estuary, Scotland, spanning the centuries leading into the 8.2 ka climate event. The results show a ‘sea-level event’ with two distinct stages between 8,530 and 8,240 cal yr BP when rates of sea-level rise departed from the background rates of around 2 mm yr-1 and reached around 13 mm yr-1 and 4 mm yr-1, respectively. The maximum probable magnitude of local sea-level rise during the stages was 1.67 and 0.41 m, which equate to barystatic magnitudes of 2.39 and 0.58 m respectively after considering the geographic location relative to the source.For the first time, we demonstrate that Lake Agassiz-Ojibway drainage alone is insufficient to explain the large volumes of North Atlantic freshwater input, and that the collapse of the Hudson Bay Ice Saddle appears to have been the main source of meltwater in to the North Atlantic. By comparing the Ythan sea-level record with other sources of evidence, we hypothesise that an initial thinning of the Laurentide Ice Sheet enabled subglacial drainage of Lake Agassiz and subsequent collapse of the Hudson Bay Ice Saddle. This was followed by the terminal drainage of Lake Agassiz completing a sequence of events that likely forced the shift in the Atlantic Meridional Overturning Circulation and hence the 8.2 ka climate event.

Glacial isostatic adjustment (GIA) modeling is not only useful for understanding past relative sea‐level change but also for projecting future sea‐level change due to ongoing land deformation. However, GIA model predictions are subject to a range of uncertainties, most notably due to uncertainty in the input ice history. An effective way to reduce this uncertainty is to perform data‐model comparisons over a large ensemble of possible ice histories, but this is often impossible due to computational limitations. Here we address this problem by building a deep‐learning‐based GIA emulator that can mimic the behavior of a physics‐based GIA model while being computationally cheap to evaluate. Assuming a single 1‐D Earth rheology, our emulator shows 0.54 m mean absolute error on 150 out‐of‐sample testing data with <0.5 s emulation time. Using this emulator, two illustrative applications related to the calculation of barystatic sea level are provided for use by the sea‐level community. Plain Language Summary: Piecing together the history of ice sheet change during past glacial cycles is not only important for understanding past sea‐level change but also for predicting how ongoing glacial rebound contributes to future sea‐level change. Traditionally, a physics‐based "sea‐level model" is used to predict the sea‐level change associated with a particular reconstruction of past ice sheet change and compare the results with geological records of past sea level. However, a fundamental limitation of this approach is the need to compute sea‐level change for a large number of plausible ice histories, which is often prohibited by the computational resources required to repeatedly solve the complex physical equations. In this paper, we describe a machine‐learning‐based statistical model that can mimic the behavior of a physics‐based sea‐level model. This statistical model is computationally cheap and we demonstrate that it is able to accurately predict global sea‐level change for a suite of 150 "unseen" ice histories. Our statistical model predicts sea‐level change 100–1,000 times faster than a physics‐based model, making it an ideal tool for investigating and improving our understanding of global ice sheet change. Key Points: The first attempt to build a deep‐learning based Glacial isostatic adjustment (GIA) emulator that can accurately predict global sea‐level change based on a given ice modelThis emulator (GEORGIA) can predict global sea‐level change history within 0.5 s with minor emulation errorThis GIA emulator along with two illustrative applications are available for use by the wider sea‐level community [ABSTRACT FROM AUTHOR]

Chamosite is a common marine authigenic mineral and microbial involvement has been often assumed during its formation. However, the fossil record of such microbial activity is ambiguous. Chamosite oolitic ironstones widely occur in the Upper Ordovician of the Yangtze Platform, but their origin remains unclear. In this study, detailed sedimentological and mineralogical investigations on ironstones from the Haima section (south‐western Yangtze Platform) helped unravel the critical role of cyanobacterial activity during marine chamosite authigenesis. Stratigraphically, deposition of the Haima oolitic ironstones corresponded with an early Katian transgression, temporally equivalent to many other early Palaeozoic counterparts worldwide. Petrographic observations revealed that different chamosite forms (ooids, peloids and matrix) all developed in close association with calcified cyanobacteria, suggesting that cyanobacteria‐involved chamosite formation existed across a wide range of hydrodynamic conditions from above fair‐weather wave base to below storm wave base. Further mineralogical characterization (backscatter imaging and electron‐microprobe analyses) at single‐grain scale revealed clear mineral zonation from the matrix (dispersed iron oxide and microquartz) through the calcified cyanobacterial sheaths (dispersed chamosite) to the ooid (chamosite). This zonation is best explained by cyanobacterial microbial mats that created benthic reducing and high‐pH conditions. These conditions drove near‐seafloor, dispersed iron oxide and microquartz (primary precipitates formed in oxic seawater) to form chamosite. The authigenic chamosite, originally dispersed within and surrounding the microbial mats, could be reworked to develop other chamositic grains. It is proposed here that the early Katian transgression was responsible for the chamosite–oolitic–ironstone development. The marine transgression submerged earlier‐exposed lands and likely supplied Fe‐Al‐rich colloidal materials to an open marine setting for the chamosite authigenesis. Moreover, transgression likely triggered upwelling, delivered ferruginous deeper water as an extra Fe source and provided nutrients for the cyanobacterial microbial‐mat development, which was essential for the widespread chamosite authigenesis across the south‐western Yangtze Platform. [ABSTRACT FROM AUTHOR]

The Pliocene shelf-edge delta (SED) in the Papuan Basin was formed by deposition of the Pliocene Orubadi Formation. On the basis of a comprehensive analysis of seismic, wireline and mud logging, and paleontological data, the stratigraphic framework, depositional system and controlling factors on the SED development were established. The Orubadi Formation includes a parallel unconformity. Internally, two third-order sequences (SQ1/SQ2) are identified, and system tracts within the sequence layers are determined by the onlaps. By tracing changes in the shoreline trajectories within the sequence, the SED was divided into six phases in the study area, with seaward advances of ∼1543–5400 m during a single phase. The thickness of the foreset is ∼309–887 m, exhibiting sigmoid or sigmoid-tangential seismic reflections. The stratigraphic patterns and sedimentary system evolution of the Orubadi Formation are determined by the interplay between sea-level changes, sediment supply, tectonic evolution and paleogeomorphology. The Coral Sea spreading provided accommodation for the SED. The Miocene–Pliocene uplift and the middle Miocene arc–continent collision in northern PNG, which caused uplift and erosion of mountains in the late Miocene to Pliocene, is the major source of sediments. The large sediment supply and sea-level changes from SQ1–SQ2 indicate an overall relative sea-level fall resulted in rapid shelf margin advancement into the basin, with the Miocene carbonate platform edge providing the necessary slope conditions for material transport. This abundant sediment supply led to the significant development of the SED. This study provides robust insights for deep-water oil and gas exploration in the Papuan Basin. The Pliocene shelf-edge delta (SED) in the Papuan Basin was formed in a compression setting with arc–continent collision. In the Orubadi Formation, the overall trend of sea-level change is decreasing, and the delta is divided into six stages. The Pliocene SED is controlled by the interplay between sea-level changes, sediment supply, tectonic evolution and paleogeomorphological. [ABSTRACT FROM AUTHOR]

The Ningfeng Plain on the South Hangzhou Bay in eastern China has long been recognized as a critical location for understanding the complex relationship between paleoenvironmental changes and human activities. Despite frequent hydrological alterations, the development of Neolithic cultures in this region offers a valuable opportunity to comprehend how ancient societies adapted to environmental transformations in the coastal zone. In this study, the authors analyzed a recently obtained sediment core (LJQ) from the Lujiaqiao archaeological site in order to reconstruct the coastal evolution of the study area over the Holocene. The foraminifera assemblage in core LJQ indicates that the study area was located in a coastal-littoral environment approximately 8.1–7.5 cal kyr BP, which gradually transitioned to an estuary receiving significant input from the open marine around 7.5–7.2 cal kyr BP. Magnetic parameters of the core then reveal the formation of a tidal brackish marsh during a period of marine regression around 7.2–5.5 cal kyr BP. The authors identified at least three episodes of elevated groundwater, likely caused by minor sea-level fluctuations. After 5.5 cal kyr BP, the influence of seawater diminished while freshwater influx increased, resulting in land formation and the development of a freshwater wetland. The Hemudu Culture first appeared in the hinterland of the Ningfeng Plain around 6.5–6.0 cal kyr BP. However, the instability of groundwater hydrological conditions would have hindered the development of Neolithic culture until the formation of the freshwater wetland at 5.5 cal kyr BP, yet the subsequent emmigration of the Liangzhu Culture was not related to any discernible environmental degradation. This study sheds new light on the complexity of the dynamic interplay between humans and their environment over time. [ABSTRACT FROM AUTHOR]

Coastal areas are extremely sensitive to variations in environmental conditions. The interaction of marine and continental processes causes a high degree of dynamism, generating depositional formations of great value for palaeoenvironmental reconstruction. This paper focuses on two pedostratigraphic deposits located under the current beach, in close proximity to archaeological tumuli located on Areoso Island (Ría de Arousa, NW Iberian Peninsula). Employing a geoarchaeological approach, sea-level rise, environmental conditions and human occupation over a 6000-year period are interpreted. The results of granulometric and mineralogical data, elemental composition and stratigraphic features, help to identify three successive environments: continental (rock weathering, soil formation and erosion); a transition to a coastal environment; and the establishment of full coastal conditions. The geomorphological evolution of the last 6.0 kyr BP has been controlled by climate, sea-level rise and human activity. The continental facies shows evidence of low sea-level up to 4.8 kyr BP and the first evidence of coastal processes after 3.2 kyr BP. These pedostratigraphic deposits located in an open coastal system improve the Holocene sea-level rise curve in the NW Iberian Peninsula and help to understand the context in which the most important archaeological structures on the island (the tumuli) began to be eroded. [ABSTRACT FROM AUTHOR]

The lack of suitable indicators of changes in such as sea‐level and circulation has been a major limit to paleoenvironmental and paleoceanographic investigations in continental shelf regions. This paper presents an environmental magnetic study by comparing two late‐Quaternary sediment cores (DH02 and DH03) from the outer shelf of the East China Sea (ECS). Late and early Marine Isotope Stage (MIS) 3 sediments were deposited in a prodelta under cold coastal currents and an open‐shelf with the Taiwan Warm Current and upwelling. The dominant iron‐bearing minerals of the late and early MIS 3 sediments are authigenic greigite (Fe3S4) and pyrite (FeS2), respectively, which were assumed to be formed nearly syndepositionally. The overlying sediments, however, are magnetically dominated by detrital magnetite. This pattern corresponds well to the temporal changes in sea‐level over this period. The widespread occurrence of greigite in the late MIS 3 sediments can also be used for future stratigraphic division and correlation in the ECS. Additionally, compared to microfossil assemblages, rock magnetic parameters based on greigite may be more sensitive to environmental changes on continental shelves. Furthermore, the inter‐borehole spatial comparisons imply not only a sedimentary hiatus/erosion of at least 30‐m thickness in core DH02, most probably during the Last Glacial Maximum, but also that core DH02 was in a more reductive environment than core DH03 during late MIS 3. The findings highlight the potential of authigenic greigite as an indicator of spatiotemporal changes in paleoenvironmental and paleoceanographic conditions on the continental shelf at orbital or even suborbital timescales. Plain Language Summary: Environmental and oceanographic conditions on continental shelves are vital for sedimentation processes and human settlements, but the reconstruction of their evolution is hindered by the lack of effective indicators. Recent studies have indicated that syndepositional formation of greigite, a precursor to pyrite, is highly likely in shallow‐water environments with rapid sedimentation. Here, two sediment cores meridionally traversing the outer shelf of the East China Sea were investigated. The magnetic mineral assemblage and sedimentary environment exhibited almost identical change patterns, with pyrite, greigite, and magnetite as the major magnetic minerals of the early and late Marine Isotope Stage 3, and Last Glacial Maximum/last deglacial deposits, respectively. This agreeably reflects the temporal fluctuations in sea‐level and ocean circulation. By comparing the two cores, the spatial characteristics of stratigraphy and redox conditions could be determined clearly. This study thus provides a good reference for paleoenvironmental and paleoceanographic research based on authigenic greigite in continental shelf sediments. Key Points: Greigite was further confirmed as the major magnetic mineral of the late Marine Isotope Stage 3 deposits widespread on the outer shelf of the East China SeaSpatiotemporal changes in environmental and oceanographic conditions on the continental shelf are well revealed by greigite‐based parametersAuthigenic greigite can serve as a sensitive indicator for paleoenvironmental and paleoceanographic studies in continental shelf regions [ABSTRACT FROM AUTHOR]

Under the influence of global warming, the problem of sea-level rise is becoming increasingly prominent. The northern part of the South China Sea (SCS) is low lying, with intense economic development, and densely populated. These characteristics make the region extremely sensitive to the consequences of rising sea levels. This study aims to reveal the trends of sea-level changes in the northern SCS and provide scientific insights into the potential flooding risks in low-lying areas. To achieve this, the Ensemble Empirical Mode Decomposition (EEMD) method is used to analyze the water level time series data from three tide gauges along the coast of Hong Kong. This analysis reveals the multidimensional change characteristics and response mechanisms of the sea level in the SCS. The findings reveal distinct seasonal, interannual, decadal, and interdecadal variations in sea-level changes. Furthermore, we explore the impact of the El Niño-Southern Oscillation (ENSO) on sea-level changes in the study area, finding a 6-month lagged correlation between the sea level and ENSO. Spatially, the rate of sea-level change is faster in nearshore areas than in the open ocean and higher in the northern regions than in the southern regions. The Multifractal Detrended Fluctuation Analysis (MF-DFA) method is employed to analyze the sea-level change time series, revealing long-range correlations and multifractal characteristics. In addition, we propose a sea-level prediction method that combines EEMD with Long Short-Term Memory (LSTM) neural networks and conducts empirical research on sea-level changes in the northern South China Sea. The results indicate that the EEMD-LSTM model outperforms the standalone LSTM model in terms of predictive accuracy, effectively eliminating noise from signals and providing a valuable reference. In summary, this research delves into the multiscale characteristics and influencing factors of sea-level changes in the northern SCS, proposing an improved sea-level prediction method that integrates EEMD and LSTM. The findings lay the groundwork for evaluating the risks of sea-level rise in low-lying regions of the northern SCS and inform future response strategies. [ABSTRACT FROM AUTHOR]

Tano, A.R.; Djakouré, S.; Yao, S.; Kouadio, Y., and Aman, A., 2023. Characterization of coastal flooding events along Cote d'Ivoire (West Africa). Journal of Coastal Research, 39(3), 494–501. Charlotte (North Carolina), ISSN 0749-0208. Sea-level rise and associated extreme events threaten coastal resources and human life through coastal flooding. Although these risks increase annually with the continuous rise in mean sea level, the extent of the affected surfaces and the duration of their exposure remain poorly understood. This study determined the flood risk levels and the durations of inundation along the coastal zone of Cote d'Ivoire by analyzing tide, storm surge waves, and coastal elevation over the period 1993–2019. The coastal flooding index (CFI), which is the difference between coastal elevation and total water height induced by coastal processes, was computed for each coastal subsection of the Ivorian coastal area. The results showed that the coastal section ranging between Cape Palmas and Vridi is less exposed to flooding, while the subsection between Vridi and Cape Three Points, particularly in Bassam, is exposed more to flooding. The duration of flooded areas ranged between 2 and 7 days. Waves and tides, which represent more than 90% of sea-level variation, are the main physical forcing mechanisms that induce coastal flooding. The study revealed that CFI will increase in the future and the flooded areas will increase, particularly along the eastern part of the coast. The identified high-flood-risk areas will require rapid interventions to protect coastal ecosystems, infrastructure, and vulnerable coastal dwellers. The results of this study could help in development of an early warning system. [ABSTRACT FROM AUTHOR]

Based on the analysis of lithology, lithofacies combinations, sedimentary structures, and fossil types in five geological sections measured through fieldwork, this paper comprehensively elucidates the sedimentary evolution characteristics of the Jurassic period in the South Qiangtang area. The South Qiangtang Basin is renowned for preserving the most complete Jurassic marine sedimentary strata in China, and it primarily consists of a mixed platform environment of carbonate and clastic rocks. The Jurassic strata in the South Qiangtang Basin range from the Quse Formation at the base to the Suowa Formation at the summit, with sedimentary facies evolving from the outer shelf to the subtidal zone, and seawater depth gradually becoming shallower. This trend may be associated with the division and expansion of the Bangong–Nujiang suture zone during the Late Triassic, subduction in the Middle Jurassic, and the suture and splicing of the Qiangtang–Lhasa plate during the Late Jurassic tectonic movements. In conclusion, this research presents a comprehensive analysis of the sedimentary evolution of the Jurassic period in the South Qiangtang Basin for the first time. The findings offer significant contributions to the understanding of the region's geological history and serve as a valuable foundation for future investigations. [ABSTRACT FROM AUTHOR]

The rapid rise of glacioeustatic change is the most extreme paleoenvironment alteration in the aftermath of Snowball Earth. Although geologists conducted a lot of multi-subdiscipline research on this issue previously, there still exists the potential room for further discussions of the process in detail. For decades, the practice proved that the Fischer plot is a simple and robust tool to illustrate the fluctuations of accommodation patterns v.s. cycle sets or strata depth which could be interpreted as relative sea-level changes. This research simulates the Fischer plot to unravel the sea-level change in the aftermath of Marinoan glaciation by measuring the lower Ediacaran Doushantuo Formation in Shennongjia, South China. The result shows that 131 fifth-order cycles and nine third-order cycles help us propose a completed second-order cycle variation of ice melting-forced sea-level change, i.e., (1) early high-frequency and slow to rapid stepwise rising, and (2) followed by a stable decrease in the latter. In addition, the vertical sedimentary facies of the lower Doushantuo Formation display, in ascending order, (1) intertidal carbonate rock, (2) subtidal clastics with turbidite, and (3) intertidal lagoon fine clastics, indicating the process of the relative waxing and waning of sea-level. Such interpretation of the Fischer plot and the sedimentary facies' vertical evolution is beneficial for studying the high-frequency sea-level change and paleogeographic reconstruction of post-Marinoan deglaciation. [ABSTRACT FROM AUTHOR]

The first records of Greenland Vikings date to 985 CE. Archaeological evidence yields insight into how Vikings lived, yet drivers of their disappearance in the 15th century remain enigmatic. Research suggests a combination of environmental and socioeconomic factors, and the climatic shift from the Medieval Warm Period (~900 to 1250 CE) to the Little Ice Age (~1250 to 1900 CE) may have forced them to abandon Greenland. Glacial geomorphology and paleoclimate research suggest that the Southern Greenland Ice Sheet readvanced during Viking occupation, peaking in the Little Ice Age. Counterintuitively, the readvance caused sea-level rise near the ice margin due to increased gravitational attraction toward the ice sheet and crustal subsidence. We estimate ice growth in Southwestern Greenland using geomorphological indicators and lake core data from previous literature. We calculate the effect of ice growth on regional sea level by applying our ice history to a geophysical model of sea level with a resolution of ~1 km across Southwestern Greenland and compare the results to archaeological evidence. The results indicate that sea level rose up to ~3.3moutside the glaciation zone during Viking settlement, producing shoreline retreat of hundreds of meters. Sea-level rise was progressive and encompassed the entire Eastern Settlement. Moreover, pervasive flooding would have forced abandonment of many coastal sites. These processes likely contributed to the suite of vulnerabilities that led to Viking abandonment of Greenland. Sea-level change thus represents an integral, missing element of the Viking story. [ABSTRACT FROM AUTHOR]

Abstract Glacial isostatic adjustment (GIA) modeling is not only useful for understanding past relative sea‐level change but also for projecting future sea‐level change due to ongoing land deformation. However, GIA model predictions are subject to a range of uncertainties, most notably due to uncertainty in the input ice history. An effective way to reduce this uncertainty is to perform data‐model comparisons over a large ensemble of possible ice histories, but this is often impossible due to computational limitations. Here we address this problem by building a deep‐learning‐based GIA emulator that can mimic the behavior of a physics‐based GIA model while being computationally cheap to evaluate. Assuming a single 1‐D Earth rheology, our emulator shows 0.54 m mean absolute error on 150 out‐of‐sample testing data with

Carbon isotopes can be used to interpret sea‐level changes during deposition, but the accuracy of sea‐level changes indicated by shallow‐water carbonates remains unclear. We carried out sedimentary microfacies and stable isotope analysis of carbonate rocks in Upper Ordovician Lianglitage Formation in Tazhong area, Tarim Basin, to examine the response of isotopes to high‐frequency cycles of shallow‐water carbonate rocks. The Lianglitage limestones can be divided into four types of microfacies that were deposited in reef and shoal environments on a platform margin. A total of sixty‐one (61) selected limestone samples have the δ13C value varying from 0.5993‰ to 1.6228‰ (average 1.1364‰). The extremely low correlation coefficient of carbon and oxygen isotopes indicate that the samples can represent the deposition seawater, thus the estimated Z value and temperature show that the Lianglitage Formation was deposited in the normal marine environment in a tropical to subtropical zone. The Lianglitage Formation shows a clear deposition trend from tidal flat to reef shoal and then to an open platform. The sedimentary environment controls the difference in carbon and oxygen isotopes of shallow‐water carbonates through the rate of burial of organic carbon, and thus the δ13C tend to increase when sea level rise. Hence the carbon isotopic composition of shallow‐water carbonate rocks can reflect sea‐level changes. The δ13C of Lianglitage Formation in well TZ72 shows four sedimentary cycles (20–40‐meters‐thick) controlled by sea‐level changes, which were also recorded in this Formation from other parts of the Tarim Basin. [ABSTRACT FROM AUTHOR]

A high-resolution multiproxy sedimentary record comprising pollen, charcoal, trace element, stratigraphy and particle size data is used to reveal environmental changes from the mangrove ecosystem at Unguja Ukuu, Zanzibar, Tanzania, over the last 5000 years. Historical human–environment interactions over the last millennia are explored by a comparison of the stratigraphic and archaeological data. The area was characterised by a mixture of mangrove forest and beaches, indicating a low level of tidal inundation to at least 3300 BCE. From 2750 BCE, mangrove forest expanded as the area experienced sea-level rise. Further sea-level rise is recorded between 600 and 1100 CE, indicated by the pollen record, particle size analysis and the presence of shell fragments. After 1100 CE, mangrove forest decreased with back mangrove species increasing, indicating a falling sea level. Cocos nucifera decreased after 1900 CE, which reflects a recent sea-level rise and possibly a phase of exploitation. Cereal pollen shows a high presence at around 1500 CE, which coincided with the arrival of the Portuguese on Zanzibar and the transition to Omani colonisation. The sedimentation rate in the core top indicates that mangroves in Unguja Ukuu cannot keep pace with the current rate of sea-level rise. [ABSTRACT FROM AUTHOR]

Stratigraphic data from salt marshes provide accurate reconstructions of Holocene relative sea-level (RSL) change and necessary constraints to models of glacial isostatic adjustment (GIA), which is the dominant cause of Late-Holocene RSL rise along the U.S. mid-Atlantic coast. Here, we produce a new Mid- to Late-Holocene RSL record from a salt marsh bordering Great Bay in southern New Jersey using basal peats. We use a multi-proxy approach (foraminifera and geochemistry) to identify the indicative meaning of the basal peats and produce sea-level index points (SLIPs) that include a vertical uncertainty for tidal range change and sediment compaction and a temporal uncertainty based on high precision Accelerator Mass Spectrometry radiocarbon dating of salt-marsh plant macrofossils. The 14 basal SLIPs range from 1211 ± 56 years BP to 4414 ± 112 years BP, which we combine with published RSL data from southern New Jersey and use with a spatiotemporal statistical model to show that RSL rose 8.6 m at an average rate of 1.7 ± 0.1 mm/year (1σ) from 5000 years BP to present. We compare the RSL changes with an ensemble of 1D (laterally homogenous) and site-specific 3D (laterally heterogeneous) GIA models, which tend to overestimate the magnitude of RSL rise over the last 5000 years. The continued discrepancy between RSL data and GIA models highlights the importance of using a wide array of ice model and viscosity model parameters to more precisely fit site-specific RSL data along the U.S. mid-Atlantic coast. [ABSTRACT FROM AUTHOR]

Paleoshorelines serve as measures of ancient sea level and ice volume but are affected by solid Earth deformation including processes such as glacial isostatic adjustment (GIA) and mantle dynamic topography (DT). The early Pliocene Epoch is an important target for sea‐level reconstructions as it contains information about the stability of ice sheets during a climate warmer than today. Along the southeastern passive margin of Argentina, three paleoshorelines date to early Pliocene times (4.8–5.5 Ma), and their variable present‐day elevations (36–180 m) reflect a unique topographic deformation signature. We use a mantle convection model to back‐advect present‐day buoyancy variations, including those that correspond to the Patagonian slab window. Varying the viscosity and initial tomography‐derived mantle buoyancy structures allows us to compute a suite of predictions of DT change that, when compared to GIA‐corrected shoreline elevations, makes it possible to identify both the most likely convection parameters and the most likely DT change. Our simulations illuminate an interplay of upwelling asthenosphere through the Patagonian slab window and coincident downwelling of the subducted Nazca slab in the mantle transition zone. This flow leads to differential upwarping of the southern Patagonian foreland since early Pliocene times, in line with the observations. Using our most likely DT change leads to an estimate of global mean sea level of 17.5 ± 6.4 m (1σ) in the early Pliocene Epoch. This confirms that sea level was significantly higher than present and can be used to calibrate ice sheet models. Plain Language Summary: Understanding the height of global mean sea level (GMSL) during the early Pliocene Epoch, when Earth's climate was warmer than today, will help to improve predictive models of current sea‐level rise. In eastern Patagonia, shorelines that formed during this time period have been uplifted due to convective flow in the mantle beneath southern South America. We model both mantle flow and the effects of ice sheet loading changes, which also cause Earth's topography to evolve through time, to correct the present‐day elevations of these shorelines. After subtracting out the effects of solid Earth deformation, we calculate a GMSL of 17.5 ± 6.4 m (1σ) in the early Pliocene Epoch. Key Points: Mantle flow through the Patagonian slab window, coupled with slab ponding in the mantle transition zone, has uplifted eastern Patagonia since 5 MaAccounting for the effects of solid Earth deformation through time, global mean sea level (GMSL) was 17.5 ± 6.4 m (1σ) in the early Pliocene EpochAntarctic ice is estimated to have been smaller in the Pliocene by 9.5 ± 6.9 m of GMSL equivalent [ABSTRACT FROM AUTHOR]

We present and discuss the results of a geomorphological and geological study aimed at reconstructing the Plio-Quaternary evolution of the NW Sicily coastal belt, a low strain rate region in the central Mediterranean Sea. We performed morphometric and field analysis of Quaternary marine terraces extracting more than 300 shoreline location points subdivided into six orders. The obtained dataset was validate by investigating the morphological changes along topographic profiles and comparing the extracted locations and elevations with the stratigraphic boundaries in the Plio-Quaternary units. We distinguished two contiguous coastal sectors characterized by different paleo-shoreline elevations and Plio-Quaternary evolution, whose estimated uplift rates fit well with the well-known, regional eastward uplift rate increase along the Northern Sicilian continental margin. Obtained results, summarized in a geomorphological map and a morpho-evolutionary model, provide new valuable data to characterize the active deformation processes and the seismotectonic setting in this critical sector of the Africa-Europe plate boundary. [ABSTRACT FROM AUTHOR]

Coastal areas are dynamic and complex systems exposed to waves, high tides, and storm surges. Often, these areas are densely populated and have essential socio-economic values for the region and country. Any changes or disruptions can cause a tremendous social burden. Coastal Vulnerability Index (CVI) is one of the most used and straightforward methods to assess coastal vulnerability. This paper aims to analyse and summarise the current state of published coastal vulnerability indices. The analysis seeks to develop a regional vulnerability index for the eastern Adriatic coast, specifically for the Istrian peninsula. A total of 18 published papers were reviewed. A detailed survey was performed on three groups of variables that represent (a) the physical features of the coast, (b) the amount of influence of wave energy on the coast, and (c) exposed socio-economic factors. While choosing Physical and ecological variables is relatively straightforward, choosing Socio-economic variables is particularly challenging. The number of variables differs significantly from one author to another. As a result of the huge variety of global coastal characteristics and different research approaches, there is no universal CVI. Therefore, analysed indices are not suited for the calculation of the vulnerability of the Istrian coast without modification. A 5 × 5 m cell dimension was proposed as the most suitable for analysing the physical vulnerability of the Croatian coast of Istria. [ABSTRACT FROM AUTHOR]

The Poigny borehole near Provins (Seine-et-Marne) provides the most complete single pristine section through the Upper Cretaceous Chalk of the Paris Basin. A well preserved and diverse palynoflora including 236 species and subspecies of organic-walled dinoflagellate cysts (dinocysts) is documented from the borehole, together with a high-resolution carbon-isotope curve (${\delta }^{13}$C$_{\mathrm{carb}}$) for the Coniacian–Campanian interval. Integration of the palynological and ${\delta }^{13}$C$_{\mathrm{carb}}$ data provides a basis for a chemostratigraphic and biostratigraphic correlation to England and Germany. Carbon isotope events (CIEs) are used to refine the placement of sub-stage boundaries in the core, and to calibrate and correlate distinctive palynological events with those from other European sections. Thirty-three palynological events in the upper Coniacian–Campanian, judged to be of biostratigraphic significance, are described. Palynological assemblages, the peridinioid/gonyaulacoid (P/G) dinocyst ratio and clay mineralogy are compared to depositional sequences and implicate sea-level as a major driver of palaeoenvironmental change.