Late Holocene Sea Level Research Articles

A record of late Holocene sea level and human impacts from the southeastern Coast of Sri Lanka

AMS radiocarbon-dated palynological evidence from Embilikala Lagoon in Bundala National Park (one of the Ramsar wetland sites) on the southeast coast of Sri Lanka indicates palaeoenvironmental changes during the last 2,700 years. The persistence of fewer mangroves (eg Rhizophoraceae taxa) suggests that sea level low stands occurred between 2,700 and 1750 cal yr BP. From the later age, the relative sea level rose, and reached the present sea level at 950 cal yr BP as indicated by the mangrove maximum. At 2,250, 700–400 and 200–150 cal yr BP, the sudden increase in marine dinoflagellate cysts (eg Spiniferites mirabilis) and foraminifera (Globigerinoides ruber) suggests increased marine influence. This is consistent with a decrease in mangrove habitats. Between 2,700 and 950 cal yr BP, severely degraded dry monsoon forests and minimal levels mangrove suggest human and marine influences were the critical drivers for changing the major vegetation types along the southeastern coast. Vegetation changes have been drastic over the last millennia.

Contemporary Salt-Marsh Foraminifera from Southern California and Implications for Reconstructing Late Holocene Sea-Level Changes

Abstract We report on the distribution of contemporary foraminifera in salt marshes in Mission Bay and Carpinteria Slough, Southern California. Combining these data with existing datasets from Seal Beach and Tijuana, we explore the potential for a regional training set to underpin quantitative reconstructions of paleoenvironmental change from foraminifera preserved in salt-marsh sediments. We demonstrate that species’ distributions are highly dependent on elevation, suggesting fossil foraminiferal assemblages here, as in many other regions, are useful depositional elevation indicators. Transfer functions provide predictions from Mission Bay cores with decimeter-scale uncertainties. Nevertheless, interpretation of marsh-surface elevation change is complicated by a complex geomorphic setting and anthropogenic impacts. An abrupt change in elevation in the mid-1700s may be related to lateral spreading of water-saturated sediments during an earthquake on the Rose Canyon fault, suggesting the potential for foraminifera to support new palaeoseismic and sea-level records for the region.

Mid- to Late Holocene sealevel changes at Abrolhos Archipelago and Bank, southwestern Atlantic, Brazil

This study presents spatiotemporal paleo-sea-level reconstructions from Abrolhos archipelago and Abrolhos Bank, and fill in a coastline gap of 500 km where no precise paleo-sea level reconstruction exists. The reconstructions are based on sedimentary, biological and geomorphological evidences. The data indicates sea-levels up to 2.9 m higher than the current one between the Mid- to Late Holocene, in agreement with the empirical sea-level envelope and with predictions of geophysical sea-level models for the Brazilian coast. The data suggests that there was little, if any, hydroisostatic compensation across 55 km of the continental shelf in the study area, between the archipelago and the mainland coast, given that similar elevations of the post-glacial sea-level maximum exist in both places.

Late-Holocene sea levels from vermetids and barnacles at Ponta do Papagaio, 27° 50′S latitude and a comparison with other sectors of southern Brazil

The height difference between paleo-vermetids and present homologous bioconstructions remains as the best Mid- to Late-Holocene paleo-sea level indicator on the Brazilian coast. The vertical range of the vermetid bioconstructions and, consequently, their precision as a sea-level indicator, varies from ±0.1 to ±1.0 m according to local conditions such as wave energy exposure and tidal range. However, live vermetid bioconstructions are scarce or do not occur at several places south of 23°S latitude, which has led to the use of other bioconstructions (e.g. Phragmatopoma caudata) as a homologous reference level, adding uncertainties to the paleo-sea level reconstructions. At the Southeast Brazilian coast, from 25° 30′ S to 28° 37′ S latitude, the precision varies from ±0.5 to ±1.0 m. At the Ponta do Papagaio headland, at 27°50′38″- 44″ S latitude, the occurrence of the subfossil barnacle Tetraclita stalactifera included in the remains of Holocene vermetids (Petaloconchus varians (d'Orbigny, 1839)) bioconstructions allowed the authors to adopt the living fringe of this barnacle species as a homologous reference level and thereby improve the accuracy of paleo-sea level reconstructions (error margin of only ± 0.5 to ± 0.3 m). The paleo-sea level obtained at Ponta do Papagaio by this method varied between +2.4 and 0.8 m. The resultant relative sea-level curve is included in the empiric sea-level envelop previously determined for the Brazilian coast, south of 28°S latitude, and matches with the far-field eustatic sea-level models. It is also similar to other curves defined for Southern Brazil regions such as Laguna-Imbituba (Santa Marta Cape surroundings, 85-40 km to South from Ponta do Papagaio), São Francisco do Sul (180 km North) and Paraná (220–260 km North). However, the height of 2.4 ± 0.3 m at 4 ky BP at Ponta do Papagaio is similar to the two cited regions to the North, but higher than the one at Laguna-Imbituba for the same period. This difference may not be significant, as it is within the ±1.0 m error margin adopted in the inference of the paleo-sea level at Laguna-Imbituba. If it is significant, it can be attributed to a local lowering of relative sea-level by thermosteric and dynamic effects of the Santa Marta Cape coastal upwelling strengthening at the epoch of maximum sea-level. This work also suggests further quantification of the living vertical distribution of vermetids and other species used as reference species (e.g. Tetraclita stalactifera, Phragmatopoma caudata), under different bedrock morphology, wave exposure and oceanographic conditions, as a necessary way to improve the precision of paleo-sea level reconstructions.

Landscape and geology as controls on Bronze Age human dispersal: a case study from Sardinia (Italy)

ABSTRACT The interaction of human dispersal patterns with landscape features can in many cases provide useful information on the sustenance strategies of past communities. Mapping the present landscape is a necessary step in recognizing the nature, impact, and diffusion of the processes which drive the behaviour of past populations and modify palaeolandscapes. We constructed a map of the land units in the southwestern corner of Sardinia and compared them with the distribution of known Bronze Age megalithic towers called nuraghes. The vast majority of nuraghes are near the plains or at mid elevations close to the river network, in areas with the highest landscape diversity. The occurrence of nuraghes also seems to be related to elevated outcrops giving the advantage of a raised position and stable foundations. Denudation processes, Late Holocene sea level rise, and anthropogenic disturbance seem to be the most important factors driving changes in the palaeolandscape.

Response of bay ostracod assemblages to Late Holocene sea-level, centennial-scale climate, and human-induced factors in northeast Beppu Bay, Japan

This study clarified the centennial-scale changes in meiobenthic bay ostracod assemblages in Japan over the past approximately 3000 years with relation to various human-induced and natural environmental factors. These factors were inferred via integrated multiproxy methods of high-resolution geological analyses of core sediments obtained from a shallow bay off a coastal plain, along with literature surveys of archeological and historical records. Five intervals were defined based on multivariate analyses of ostracod assemblages. The ostracod assemblage was stable before around the 6th century because of aggradational sedimentation related to gradual increases in sea level. Since then, the composite factors such as the development of a sandy spit near the study site, stable sea level, regional tectonics, regional centennial-scale climatic change possibly related to El Niño Southern Oscillation (ENSO), and flood mitigation by human settlement in the coastal plains triggered the formation of tidal flats and subtidal sandy areas with seagrass beds. This has markedly influenced offshore bay ostracod assemblages since around the 12th century. Anthropogenic impacts, such as reclamation and various artificial constructions since the late 20th century caused the disappearance of seagrass beds, input of coarser sediment into offshore bays, and increased nutrient loads. Therefore, ostracod assemblages have changed drastically. Ostracod assemblages near the boundary between land and sea have been affected by multiple complex factors, such as regional climate and depositional and human-induced processes during the Late Holocene.

Rethinking Reef Island Stability in Relation to Anthropogenic Sea Level Rise

AbstractUnprecedented rates of anthropogenic sea level rise (ASLR) and attendant wave‐driven flooding and salinization threaten the stability (and habitability) of atoll islands. Thus, there is doubt regarding the continued existence of sovereign atoll nations and unique, place‐based indigenous atoll cultures. Evidence that some atoll islands may have originally formed in the latter stages of post‐glacial sea level rise (SLR) has been interpreted to mean they will persist under accelerating ASLR. These forecasts are at odds with interpretations that atoll islands will succumb to rising seas. To shed light on conflicting models of island stability, we develop a multitemporal island vulnerability assessment (MIVA) to anticipate island instability and apply it in the Republic of the Marshall Islands (RMI) where there is a history of previous research. Using evidence from geological and historical records of island response to changing late Holocene sea level and modern tide, wave, and groundwater observations, we identify thresholds where islands pass from stable to unstable phases due to projected local, relative ASLR. Under the most likely scenario (intermediate‐high) where ASLR reaches 1.91 m by 2100, island stability deteriorates by midcentury as historical rates of SLR at RMI increase threefold, and temporary flood events deteriorate potable groundwater and agroforests. In the second half of the century, as ASLR exceeds geological sea level thresholds, permanent island instability will be inevitable with no action. We conclude that these islands are already trending into declining stability due to ASLR as documented by published observations of extreme tides, wave inundation, salinization, and sediment mobilization.

A late-Holocene record of coastal wetland development and fire regimes in tropical northern Australia

This study presents three records of environmental change during the late-Holocene from wetlands across Bentinck Island in the South Wellesley Islands, northern Australia. Radiometric dating provided ages for sediment cores with the longest chronology spanning the last 1250 cal. yr BP. Palynological results show the diverse mangrove community transitioned to woodland- and wetland-dominated vegetation over the last 850 years on the southeast coast. The key driver of this landscape change was likely late-Holocene sea level regression and coastal progradation in the Gulf of Carpentaria. This study found freshwater wetlands expanded across Bentick Island over the last 500 years, with sedges and rushes peaking in the last 350 years. Macroscopic and microscopic charcoal records, coupled with archaeological evidence, highlights the spatial and temporal variation in fire regimes across the island, reflecting the traditional fire management practices of the Kaiadilt people during the late-Holocene. This study finds a significant increase in charcoal accumulation in the 1900s when Kaiadilt fire practices were disrupted and the South Wellesley Islands were abandoned. The pollen record reflects little change in the vegetation despite the shifting fire regime, highlighting the importance of multi-proxy approaches to reconstructing past environments in tropical northern Australia where vegetation is adapted to fire.

Geoarcheomorphosites under Strong Urbanization Pressure at the Tineh Plain, NE of the Nile Delta, Egypt

Most geologic and geomorphologic features emerged on a deltaic plain resulted from the interplay of marine, land and river, of which are some have the potential to be a geoheritage site, this is called a geomorphosite. Over time, human impact due to settlements on the geomorphosite, reshaped and transformed the site to geoarcheomorphosite. The Great Pelusium, or Tell El-Farama, which is located along the Tineh Plain at the NE extreme of the Nile Delta between the third and fifth c. AD, is classified as a geoarcheomorphosite. The location includes several geomorphosites, such as the accreted coastal ridges, which record Late Holocene sea level changes. It also includes traces of the flash flood on the Pelusiac branch during the eighth c. AD, with the fluvial flood plain, natural levee, and crevasse splays, on which the Great Pelusium, Tell El-Luli, Tell El-Fadah, and Tell El-Makhzan were constructed. Recently, the area subjected to a hub development project, which may represent anthropogenic hazards that threaten the Great Pelusium. This study aims to quantify the potential anthropogenic hazards. The change detection shows that in 1984 the area of the geoarcheomorphosites was 424.8 km2, representing approximately 67.1% of the Tineh Plain, in addition to the sand dune area of 75 km2, representing 11.8%. In 2018, the area saw agricultural activities, fish farms, and an urban expansion that covered approximately 244.2 km2, representing 38% of the Tineh Plain. The construction of a new hub in the Suez Canal corridor and the addition of a new community of one million people in an area of 164 km2, representing 30.3% of the plain, will add more pressure on the geodiversity. A conservation plan is recommended in the form of sustainable development to save an important area of geoheritage in Egypt and convert the area into a tourism destination.

Preface: Celebration of the Career of Robert Nathan Ginsburg

Preface: Celebration of the Career of Robert Nathan Ginsburg

Reconstruction of Late Pleistocene and Holocene Sea Level Curve for the East Coast of India

ABSTRACT Holocene sea level curve has been generated for the East Coast of India. About seventy five 14C dates which are available from published works on coastal plains and offshore regions of the East Coast were considered and were subsequently calibrated into calendar years for analysis and plotting thereof. From the 100m depth, a moderate rate of sea level rising at the rate of about 0.88m/100 years is observed during 14,800 to 10,800 YBP. In between 10,800 to 9,200 YBP, a steep rise (Sea Level Rise - SR1) is noticed at the rate of 2.06m/100 years. Following a brief sluggish phase (for nearly about 1,100 years) of slow rising around 0.82m/100 years, another steep rate of rising of about 2.22m/100 years (SR2) is observed during 8,100 to 7,200 YBP. After that period to the Recent, there were 5 minor fluctuations with regression phases dominating over transgression phases in terms of duration and magnitude. It is also observed that the magnitude of all five high stands in between 7,200 to the recent has a decreasing trend from +4m to 0m. It obviously indicates that the most of the present day coastal plains were once under the sea as evidenced by the presence of many inland leftover paleo delta signatures in the East Coast of India.

Holocene foraminiferal and geochemical records in the coastal karst dolines of Cres Island, Croatia

Numerous karst dolines have been formed along the Croatian coast and many have been submerged during the Late Glacial and Holocene sea level rise. The coastal area of Cres Island in the Northern Adriatic is a typical example of this geomorphological setting, where transitional forms from subaerial to submerged dolines are present. Once dolines are formed they can accumulate soil, water and sediments due to their morphology. Sediments are an especially valuable source of environmental data. This paper presents the results of the study of foraminiferal assemblages and sediment geochemistry, supplemented with grain-size and mineralogical data, from the marine ponds developed in the karst dolines on Cres Island. Obtained data is correlated with the sediment core record from submerged dolines in the present-day embayments along the coastal zone of Cres Island. In total, 3 sediment cores were collected in the marine ponds Marinska, Arcij and Podbrajde, while 2 longer sediment cores have been extracted from the Jaz and Sonte embayments. The Marinska, Arcij and Podbrajde marine ponds have distinct geochemical and mineralogical sediment compositions, with monospecific foraminiferal assemblages and generally differ from each other. The common characteristics are their high N and P concentrations and the algal origin of organic matter. Agglutinated foraminiferal taxa (Haplophragmoides canariensis and Trochammina inflata), typical for intertidal environments, are abundant in the brackish-water Marinska pond, while stress-tolerant species Ammonia tepida has been identified in the Arcij marine pond. Environmental conditions in the Podbrajde marine pond did not facilitate the development of a rich foraminiferal fauna. Results from the present-day marine ponds enabled recognition of similar environments in the sediment cores collected in the Jaz and Sonte embayments that were progressively inundated during the Holocene sea level rise. A palaeo-marine pond existed in the Sonte embayment until 6610 cal BP, when the sea flooded the investigated area. A marine pond in the Jaz embayment was formed at 711 cal BP. Low-diversity foraminiferal assemblages in these palaeo-ponds are similar to those recognized in the present-day Arcij marine pond on Cres Island. However, differences in the geochemical composition of palaeo-marine ponds, in comparison to the present-day ponds, exist. They might be attributed to climate variability over time and variations in the geological setting of each environment. High Mo concentrations and abundant organic matter content are the main sediment characteristics of the recognized palaeo-marine ponds in the Jaz and Sonte embayments.

Late Holocene sea level change along the coast of Fethiye Gulf in southwestern Turkey

AbstractIn the Fethiye Gulf on the southwest coast of Turkey, several submerged archaeological sites provide useful data about relative sea level changes since the Byzantine period. The current elevations of contemporary archaeological structures were measured to determine the amount of relative sea level change. The archaeological sea level markers in this seismically active region provide new data about the amount and period of relative sea level rise. Taking into consideration the time of the last use of the structures, instead of their time of construction, three different rates of vertical land movement of 2.18 ± 0.3, 2.96 ± 0.3, and 3.29 ± 0.5 mm/yr were estimated. These data indicate that tectonic activity differs from region to region, most likely related to local normal faults in the gulf. Recent earthquakes have confirmed active seismicity in this area. These results demonstrate that the changing sea levels in the Fethiye Gulf have been strongly influenced by vertical tectonic movement over the last 1,400 years. Results also contribute to studies of future coastal changes in the Fethiye Gulf and its surroundings.

Mid and Late Holocene sea level variations in the Canary Islands

The eastern coast of Fuerteventura (Canary Islands, Spain) hosts the most complete and representative emergent Holocene marine deposits in the middle latitudes (27°N to 30°N) of the eastern Atlantic Ocean. The deposits consist of berms of gravel and foreshore sands which form beach rocks comprising >62 bed sets, with each bed set containing dozens of individual laminations suggesting a cyclical cause as, for example, the orbital movement of the Earth. Calibrated radiocarbon ages place a group of older Holocene highstands of Fuerteventura at around the Mid-Late Holocene boundary (around 4.2 kyr B.P.), and another group of more recent highstands in the Dark Age Period (around 1.4 kyr B.P.) of the Northern Hemisphere. They have been recorded at 4 m and 3.5 m apmsl respectively. The present-day tidal amplitude is around 3 m. Assuming a similar value for the Holocene, the corresponding relative sea level rises were around 2.5 m and 2 m apmsl respectively. Moreover, terrestrial deposits intercalated between the marine deposits indicate a lowering of the sea level at ca. 3 kyr B.P. When the sea levels reached their highstands during these two periods, the sea surface temperatures (SST) at the southern tip of the cold Canary Current were, respectively, 0.5 and 1.5 °C colder than the present-day SST (21.23 °C). The fossil fauna content confirms that these highstands occurred in cold conditions. In contrast, the present SST reaches the range of temperatures of the Holocene Optimum in the area.Fuerteventura has been vertically stable since the last interglacial period, and the sedimentology of the deposits precludes an origin from tsunamis or storms. This island is in a far-field region in terms of glacial isostatic adjustment (GIA) processes. Here, we suggest that the deposits may be related to GIA and ice mass losses effects in the Southern Hemisphere.

Quaternary sealevel changes and coastal evolution of the Island of Trindade, Brazil

The present work presented the first dated paleosealevel indicators and new paleogeographic reconstructions of the Island of Trindade. All evidence for Holocene sealevels point to the elevations higher than the present in the age interval between 5.06 ka and 0.55 ka. The altitude and ages of the reconstructions are in good agreement with hindcast model curves and the empirical sealevel envelope for the mainland eastern and northeastern Brazilian coast. However, the position of paleo vermetid-reef indicates that sealevel was lower than eustatic elevation, suggesting an effect of island subsidence. In contrast to the Brazilian mainland coastal zone, where conspicuous evidences of Pleistocene highstands were recorded, no evidence of sealevels predating the Holocene has ever been observed on the island. This could be attributed to intense coastal erosion and log-term island subsidence.A volcanic edifice rising more than 5500 m above the ocean floor was built by magmatic activity that extended over the late Pliocene and early Pleistocene. After the cessation of volcanic build up, the island started to shrink due to subaerial and marine erosion. During Pleistocene sealevel lowstands, alluvial fans were formed beyond the present limits of emerged areas. They were enclosed within and preserved from erosion by the Middle to Late Pleistocene lava flows and pyroclastic deposits. During Late Pleistocene sealevel highstand, intense coastal erosion removed the distal parts of the alluvial fans. It is very likely that at that time the entire coast of the island experienced intense erosion and subsidence as deduced from the absence of Pleistocene coastal deposits, which are widespread along mainland Brazilian coast.The east coast of the island was dominated by high sea cliffs sculpted into volcanic rocks. A volcanic cone was subsequently formed, when the sealevel was lower than present during the Late Pleistocene to early Holocene. During the mid to late Holocene sealevel highstand the volcanic cone was partially eroded and a bay formed, where vermetid-reefs grow and sand beach deposits prograded until the bay was infilled. During the sealevel maximum, wave-cut terraces were formed and sea cliffs were active. During the lowering of the sealevel, cliffs became inactive and vermetid-reefs were eroded. Beach erosion and aeolian deflation presently prevails, indicating a low sediment supply.

전라북도 곰소만 일대의 전통 소금(자염) 생산 기록으로 본 현세 후기 해수면 변동

우리나라의 전통적인 소금은 바닷물을 끓여 증발시켜 얻는 자염이다. 부안과 고창 일대의 곰소만에서는 바닷물을 농축시킨 함수를 얻기 위해서 섯구덩을 만드는데, 이때 섯구덩의 위치는 갯벌 최상부의 사리(대조) 때에만 바닷물이 들어오는 가장 육지쪽 장소를 선택하게 된다. 고문헌 기록을 근거로 고창군 심원면 사등마을의 검당포(검당마을) 일대의 섯구덩의 위치가 역사시대 동안 변하였다는 것을 파악하였다. 1900년대 초기에는 검당마을 바로 앞에 섯구덩을 만들었다. 500년 전후 시기에는 백제 때의 제방인 김제 벽골제, 익산 황등제, 정읍 눌제의 위치와 기능을 근거로 섯구덩의 위치가 1900년대 초기의 위치와 거의 유사하였을 것으로 추정하였다. 1500년 전후 시기에는 조선 초기의 신증동국여지승람(1530)의 기록을 근거로 섯구덩의 위치가 바다쪽으로 약 800 m 정도 들어간 곳으로 옮겨졌으며, 1800년대 이후에는 택리지(1751)와 지방지도의 고부군 지도(1872) 등의 기록을 근거로 섯구덩 위치가 다시 검당마을 바로 앞으로 이동한 것으로 보았다. 이렇게 1500년대와 1800년대 이후에 섯구덩 위치가 차이를 보이는데, 이는 해수면 높이의 변화가 있었음을 시사하는 것이다. 역사 기록에 의해 추론한 해수면 변화는 지역적이나 전지구적 해수면 변동 양상과 거의 일치한다.

Sea level controls on palaeochannel development within the Swan River estuary during the Late Pleistocene to Holocene

High-resolution seismic profiles were conducted across the metropolitan area of the Swan River estuary (Perth, Western Australia) to explore the sub-surficial stratigraphic architecture, down to a depth of about 40m below the river bed. The acoustic profiles revealed a complex system of palaeochannels where three main unconformities (R1, R2, R3) bound as many seismic units (U1, U2, U3), over the acoustic basement. Integrating these data with sediment borehole analysis, LiDAR data and available literature of the geology and stratigraphy of the area, it was possible to determine the development of these stratigraphic units, in response to Late Pleistocene and Holocene sea level fluctuations and conditioned by pre-existing topography and depositional palaeoenvironments during the last ~130,000years. The deepest unit (U3) can be interpreted as the Perth Formation, which consists of interbedded sediments that were deposited in a large palaeo-valley downcutting into the underlying acoustic basement (bedrock: Tamala Limestone and Kings Park Formation), under a fluvial to estuarine setting, existing between ~130 and 80ky BP (in the Last Interglacial).The middle unit (U2), composed of heterogenic fluvial (possibly lacustrine) and estuarine sediments, represents the Swan River Formation. Similarly to the Perth Formation, the formation infills channels incised in older formations and reflects the hydrogeological conditions linked with sea level fluctuation changes during the Last Glacial low stand. Holocene (last ~10ky) fluvial and estuarine deposits form the shallowest unit (U1). These sediments have a highly variable internal structure, ranging from heavily layered, filling palaeochannels, to hard and chaotic, atop pre-existing topographic highs. The wave-dominated Swan River system shares several similarities with a number of estuaries worldwide, such as Burrill Lake (NSW, Australia) and Arcachon Lagoon (Aquitaine, France). This research represents the first environmental high-resolution acoustic investigation in the middle reach of the Swan River estuary.

Geochemical investigation of the South Wellesley Island wetlands: Insight into wetland development during the Holocene in tropical northern Australia

The South Wellesley Islands in the Gulf of Carpentaria, northern Australia, were the recent focus of a palynological investigation which found vegetation change during the Holocene was driven by coastal progradation and regional climate. Here, we present new elemental data from x-ray fluorescence core scanning which provides non-destructive, continuous and high resolution analysis from three wetlands across Bentinck Island, the largest of the South Wellesley Islands. Elemental data and grain size analyses are combined with lead-210 (210Pb) and accelerator mass spectrometry (AMS) carbon-14 (14C) dates. An open coastal environment was present 1250 cal. a BP on the south east coast of Bentinck Island, with sediment supply incorporating fluvial deposition and detrital input of titanium and iron from eroding lateritic bedrock. Prograding shorelines, dune development and river diversion formed a series of swales parallel to the coast by ~800 cal. a BP, forming the Marralda wetlands. Wetlands developed at sites on the north and west coasts ~500 and ~450 cal. a BP, respectively. Geochemical and grain size analyses indicate that wetlands formed as accreting tidal mudflats or within inter-dune swales that intercepted groundwater draining to the coastal margins. The timing of wetland initiation indicates localised late-Holocene sea level regression, stabilisation and coastal plain development in the Gulf of Carpentaria. Elemental data provide new records of wetland development across Bentinck Island, highlighting the value of a multi-proxy approach to understanding environmental change during the Holocene in tropical northern Australia.

Marine notches in the Maltese islands (central Mediterranean Sea)

We present the first detailed survey of tidal notches in the central Mediterranean area, in particular along the coastline of Gozo and Comino (Malta). The Maltese Islands represent one of the few sites in the Sicily Channel which exhibits coastal carbonate rocks. Marine notches on the islands of Gozo and Comino were surveyed by means of a seven day continuous snorkeling survey around the entire perimeter of the two islands. We surveyed the occurrence, lack and typology of marine notches and we correlated them with late Holocene sea level changes. Sea temperature (T) and electrical conductivity (EC) were collected along the route in order to locate the submarine springs and to relate them to the surveyed notches.A well-carved continuous roof notch was discovered along most of the plunging cliffs. It is well-carved out, in particular along the northern and western coast of Gozo. It develops from about 0.2 m above the mean sea level down and it can be up to 1.5–2 m deep. On the contrary, tidal notches are localised only in 8 sites. In 2 sites, Vermetid trottoirs develop at low tide level. In addition, at about −7 m to −10 m m.s.l., a 2–5 m wide marine terrace develops along extensive tracts of plunging cliffs, always in correspondence with the roof notches. This submerged terrace seem to be the result of the late Holocene slowdown of the sea level rise, which started to smooth the terrace and to carve out the submerged part of the roof notch, thanks to the exposed location of the islands and the favourable lithology.Through the collection of hydrological data, the presence of 21 submarine springs were detected. They occur mainly in the south-western coast of Gozo and on eastern coast of Comino. Anyway, marine notches seem not to be related to the freshwater outflow, such as those in the Adriatic Sea, because the studied islands are very exposed. As a consequence, along the Maltese islands bioerosion seems to be the most effective process in notch development.

Timing, magnitude and effects of late Holocene sea level drawdown on island habitability, Aitutaki, Cook Islands

ABSTRACTGeologist Bill Dickinson argued that prior to late Holocene sea level fall, in many Pacific island settings low‐lying islands were awash, shallow nearshore environments were restricted and human settlement was constrained or sometimes impossible. Stable coastlines and islets of modern configuration only developed after the “cross‐over date”, when declining high‐tide levels fell below mid‐Holocene low‐tide levels, a regionally variable process. We evaluate evidence from the almost‐atoll of Aitutaki, Cook Islands against this model, providing: (1) a local late Holocene sea level reconstruction including nine U/Th‐dated microatolls; (2) 22 new AMS dates on human activities, many from small, low‐lying offshore islets; and (3) elevation data for 14C‐dated cultural deposits on three islets. Our results include an early first millennium sea level position 0.74–0.97 m (± 0.126) above modern height‐of‐living‐corals, an eighth to eleventh century AD minimum relative to the long‐term trend, and a sea level rise peaking in the mid‐fourteenth to sixteenth centuries. This reconstruction, combined with twelfth century AD Cocos nucifera charcoal, informs on the timing and distribution of human activities across Aitutaki's evolving land and seascapes and sea level impacts. While our findings do not contradict Dickinson's model of sea level constrained island settlement, other explanations cannot be excluded.