Present Sea Level Research Articles

Stratigraphy and chronology of the Cala Mosca site, SW Sardinia (Italy)

AbstractThe relict beach deposit of the Cala Mosca marine terrace is considered an important section of Marine Isotopic Stage (MIS) 5e (ca. 125 ka) sea-level highstands. Analysis of the stratigraphy and sediments of the deposit indicates the presence of a composite marine terrace comprising two superimposed marine units, luminescence dated to the MIS 5e (137 ± 7, 134 ± 7 ka) and MIS 5c (92 ± 6 ka) substages. The stratigraphic superimposition of the two highstands, both placed ~5 m above present sea level, agrees with other areas along the Sardinia coasts. The evident superimposition of two sea-level highstands and development of the composite terrace cannot be accounted solely by high-frequency sea-level oscillation that occurred within MIS 5 for the Mediterranean Sea. This suggests controversial, but significant, regional versus local tectonic activity occurred during the Late Pleistocene.

Middle-late Pleistocene chronology of palaeoshorelines and uplift history in the low-rising to stable Apulian foreland: Overprinting and reoccupation

To refine knowledge about terrace phases and uplift history for a tectonically poor deformed region, we apply the synchronous correlation method to reconstruct the chronology of a poorly constrained sequence of raised palaeoshorelines on the Apulian foreland, southern Italy. This work uses new chronological constraints obtained by amino acid racemisation (AAR) and isoleucine/alloisoleucine epimerisation (IE) on Patella spp., Thetystrombus latus (Gmelin), Glycymeris sp., and ostracods and U-series dating on corals Hoplangia durotrix Gosse and Cladocora caespitosa Linneo. This procedure provides a quantitative estimate of the vertical movements and associated rates within a region of the Apulian foreland. The synchronous correlation method uses sea-level highstands and uplift rate(s) as inputs; in particular, for sea-level highstands, the inputs are the age of the highstands and the sea-level elevation of the highstands relative to the present-day sea level. The output is a set of currently expected elevations of each sea-level highstand (the present elevations of palaeoshorelines). We then used regression analysis to assess the robustness between our observed palaeoshorelines and expected elevations of sea-level highstands. Our results show that the best fitting scenario is obtained using the sea-level curves of (i) Waelbroeck et al. (2002) from present to 410 ky BP and (ii) Rohling et al. (2014) from 410 to 590 ky BP as inputs for our synchronous correlation method, with uplift rates ranging from 0.09 mm/y to 0.07 mm/y with a mean value of 0.08 mm/y from 590 ky BP onwards.We recognised palaeoshorelines in the field belonging to the following highstands: 120 ky BP (MIS 5.5, second peak), 127 ky BP (MIS 5.5, first peak), 212 ky BP (MIS 7.3), 330 ky BP (MIS 9.3), 410 (MIS 11), 525 ky BP (MIS 13.3), and 590 ky BP (MIS 15). Our results show field observations of the reoccupation effect of younger palaeoshorelines over older ones due to the relatively slow uplift rates measured in the investigated area as predicted by our synchronous correlation method. In particular, we show a well-mapped and described reoccupation of the MIS 5.5 palaeoshoreline over the MIS 7.3 palaeoshoreline, constrained by new absolute dating.In addition, the data from the Apulian foreland suggest an MIS 7.3 highstand close to the present sea level.

Holocene shore‐level changes, southern Lolland and the Femern Belt, Denmark

ABSTRACTWe propose a new shore‐level displacement curve for southern Lolland and the Femern Belt in south‐eastern Denmark based on 94 new and four published radiocarbon ages of organic material and shells of marine molluscs. Mires existed in the deeper parts of the Femern Belt during the Early Holocene, and a large lake formed as the water level gradually rose. The lake phase was followed first by a brackish‐water phase from c. 8500 cal a bp and by a marine phase after c. 7800 cal a bp when the relative sea level was ~8 m lower than at present. Over the past 6500 years the sea level has gradually risen by ~2 m and reached its highest level in recent times. There are no indications of a higher than present sea level in the area and no indications of 1–2 m sea‐level oscillations as reported from other parts of the region. The relative sea‐level curve for southern Lolland differs from relative sea‐level curves from northern parts of Denmark, which are more influenced by glacio‐isostatic uplift. Southern Lolland has been uplifted by 4–5 m over the last 8000 years, whereas the Limfjord region in northern Denmark has been uplifted by around 12 m during the same period.

Holocene relative water level and storminess variation recorded in the coastal peat bogs of the Vistula Lagoon, southern Baltic Sea

The history of regional sea-level changes is critically important for building global environmental reconstruction models and identifying major driving forces. The coastal peatlands located on the terraces of the Vistula Lagoon (Gulf of Gdańsk, southern Baltic Sea) are one of the most valuable, and not yet fully explored, archives of the regional history of sea-level and storminess changes during the middle and late Holocene. The comprehensive analysis of peat and gyttja allowed establishing radiocarbon calibrated time series of stable carbon isotope composition (δ13C), pollen and diatom data. The results indicate that the sea-level increased from ∼20 to 8 m below present sea level between 9000 and 7000 yr b2k at an average rate of ∼6 mm/year. Around 5000 yr b2k, the sea-level was ∼2.5 m lower than at present, which indicates a decrease in the rate of sea-level rise to ∼2.75 mm/year between 7000 and 5000 yr b2k. During the last 5000 years, the sea-level had risen at ∼0.5 mm/year to the present position. Changes in brackish diatoms, Pediastrum sp. concentrations, and maxima of δ13C suggest ten periods of increased rates of sea-level rise and storminess between 7000 and 1500 yr b2k. Increased sea-levels and stormy surges on the peat surface occurred mainly during cold periods or the periods of transitions. These observations are in good agreement with climate fluctuations in the Northern Hemisphere related to the variations in total regional solar irradiation.

Limited Mediterranean sea-level drop during the Messinian salinity crisis inferred from the buried Nile canyon

The extreme Mediterranean sea-level drop during the Messinian salinity crisis has been known for >50 years, but its amplitude and duration remain a challenge. Here we estimate its amplitude by restoring the topography of the Messinian Nile canyon and the vertical position of the Messinian coastline by unloading of post-Messinian sediment and accounting for flexural isostasy and compaction. We estimate the original depth of the geomorphological base level of the Nile River at ~600 m below present sea level, implying a drawdown 2–4 times smaller than previously estimated from the Nile canyon and suggesting that salt precipitated under 1–3 km deep waters. This conclusion is at odds with the nearly-desiccated basin model (>2 km drawdown) dominating the scientific literature for 50 years. Yet, a 600 m drawdown is ca. five times larger than eustatic fluctuations and its impact on the Mediterranean continental margins is incomparable to any glacial sea-level fall.

Geology of Ayn Al Majdoub Karstic Lake, Benghazi, NE Libya

The major karstic area in Libya known as Ayn Zayanah system is a unique phenomenon of concentrated karstic surface and subsurface dolines and channels. By focusing on Al Majdoub Lake, as a case study, we can better understand how lithology, structure and hydrology contribute to the regional formation of the Karstic system. Geologically, the limestones of the middle Miocene, Benghazi Formation is forming the northern side of Benghazi region, which is characterized by well-developed surficial, interface, surface and subsurface karstic features that are open or filled with sediment. The formation of Ayn Majdoub doline is filled with saline water, which is attributed to the dissolution of a buried carbonate layer by fresh groundwater due to the drop of the Sea level and the associated groundwater levels. This is combined with epeirogenesis movements, which have caused the development of karstification to reach a depth of 130-150 m below present sea level in the Benghazi plain. Through this Karstic system, groundwater seeps from Benghazi Basin towards the Ayn Zayanah (The Spring) and then to the Blue Lagoon (The Lake) finally to the sea.

Late Quaternary neotectonics in the Bird’s Head Peninsula (West Papua), Indonesia: Implications for plate motions in northwestern New Guinea, western Pacific

New Guinea is a mountainous island in a tectonically active setting with regions experiencing rapid uplift rates as shown by the celebrated emergent coral reef terraces of the Huon Peninsula. In the northern Bird’s Head Peninsula of northwestern New Guinea, rapid uplift has been a feature of the tectonic history over the past 2.7 Ma with the development of the mountainous and highly dissected Kemum High (up to 2200 m) associated with the formation of the Central Bird’s Head Monocline, implying a long-term uplift rate approaching 0.8 m/ka. In this work, Late Quaternary uplift rates of up to 1.28 m/ka were determined for emergent coral reefs in the Manokwari region (northeast of the much larger Kemum High). The rapid uplift rates are based on 230Th-U ages (2.7 ± 0.3 to 246.3 ± 8.0 ka with most ages in the range 69–128 ka) on corals and coralline algae, sampled from calcarenites at elevations of 2.45–77.5 m above present sea level. The rapid uplift indicates neotectonic activity reflecting crustal thickening in the Quaternary and neptunian dykes probably related to gravitational instability. The present-day tectonic setting of the Bird’s Head Peninsula is cryptic, but the combination of uplift and tectonic activity shown by the earthquakes are consistent with ongoing oblique convergence between the Bird’s Head and the adjacent Pacific-Caroline plate. Over the past 2 Ma, plate motion between the Bird’s Head Peninsula and the Pacific-Caroline Plate has been accommodated by incipient south-dipping subduction along the Manokwari Trough to the north (with longer-lived subduction along the New Guinea Trench) and sinistral strike-slip movement along the Yapen fault whereas the Sorong Fault has been largely inactive.

Coastal palaeoenvironmental record of Late Bronze to Iron Age harbour development at Liman Tepe-Clazomenae, western Anatolia, Turkey

Liman Tepe-Clazomenae, located in the southern Bay of Izmir, Turkey, was an important Early Bronze Age to Classical Period trading port and cultural centre in the eastern Aegean. The mainland harbour, now submerged ~1.5–2 m below present sea level, is one of the best-preserved examples of an Iron Age (Archaic Period; ca. 7th–6th c. BCE) semi-enclosed harbour (>5 ha) with engineered breakwater structures. A multi-proxy study (micropalaeontology, micro-XRF core scanning) was conducted on seven harbour sediment cores and integrated with geophysical data to map the harbour structures and document coastal palaeoenvironmental changes. Bathymetry and side-scan mapping revealed two broad (>35 m) rubble-constructed breakwater structures and a submerged headland that divided the harbour into two separate sub-basins. Linear magnetic anomalies within the eastern breakwater indicate a buried pier structure, recording possible augmentation of a Late Bronze Age (LBA) or Early Iron Age (EIA) proto-harbour embayment. The harbour basin stratigraphy comprises foreshore and upper shoreface deposits overlying terrigenous clays across a marine transgressive surface. A distinctive silt-rich chemofacies with increased Ti/Ca and decreased Si marks a transition from a sandy marine shoreface to a low energy, sheltered LBA proto-harbour embayment. The Iron Age harbour construction (ca. 7th–6th c. BCE) is recorded by a rise in Rosalina, decreased Ti/Ca and the appearance of Archaic pottery. The harbour was in use from the Archaic to early Classical periods and served as Clazomenae's mainland commercial port.

Sea level along the world’s coastlines can be measured by a network of virtual altimetry stations

For nearly 30 years, space-based radar altimetry has been routinely measuring changes in sea level at global and regional scales. But this technique designed for the open ocean does not provide reliable sea level data within 20 km to the coast, mostly due to land contamination within the radar echo in the vicinity of the coast. This problem can now be overcome through dedicated reprocessing, allowing the retrieval of valid sea level data in the 0-20 km band from the coast, and then the access to novel information on sea level change in the world coastal zones. Here we present sea level anomalies and associated coastal sea level trends at 756 altimetry-based virtual coastal stations located along the coasts of North and South America, Northeast Atlantic, Mediterranean Sea, Africa, North Indian Ocean, Asia and Australia. This new dataset, derived from the reprocessing of high-resolution (300 m) along-track altimetry data from the Jason-1, 2 and 3 missions from January 2002 to December 2019, allows the analysis of the decadal evolution of coastal sea level and fills the coastal gap where sparse sea level information is currently available.

Timing of Sedimentary Evolution and Transgressions in the Bohai Sea During the Last ∼200 ka: Constraints from Luminescence Dating of a Core from the Yellow River Delta

The southwestern coast of the Bohai Sea is a favorable area to study land-sea interactions and palaeoenvironmental changes. The Bohai Sea hosts vast volumes of sediment discharged from rivers of mainland China and has undergone large-scale sea-level fluctuations during the Quaternary. Three transgressions have been previously determined for the Bohai Sea since the late Pleistocene. However, the timings of the two earlier transgressions are still unclear. Here we present chronological, micropalaeontological, and sedimentological data for an 80-m-long sediment core recovered from the modern Yellow River delta. The changes in grain size and foraminiferal assemblages suggest the occurrence of three marine sedimentary units, M-3, M-2, and M-1, that represent transgressions of the Bohai Sea. We applied optically stimulated luminescence dating using both quartz and feldspar minerals on 15 samples obtained from core YRD-1401 and eight radiocarbon ages using fragments of microfossils shells and organic carbon. Our quartz optically stimulated luminescence ages for M-2 (ca. 60 ka), are consistent with K-feldspar post-infrared stimulated luminescence ages, suggesting that M-2 on the southwestern coast of the Bohai Sea was deposited during early MIS 3. The sea level of the Bohai Sea during early MIS 3 is estimated to have ranged from 26.8 to 19.9 m below the present sea level. Luminescence ages and foraminiferal assemblages indicate that M-3 was likely formed during MIS 5 and a tidal-river environment prevailed on the southwestern coast of the Bohai Sea during MIS 6 or earlier.

Luminescence characteristics of coastal sediments in Langhovde, East Antarctica

The Late Pleistocene sea-level history of Antarctica is key to understanding and predicting the responses of icesheets, which significantly contribute to the global sea level, to changing climates. Coastal sediments at Lützow-Holm Bay, East Antarctica, have yielded radiocarbon ages of Holocene and Marine Oxygen Isotope Stage (MIS) 3 from deposits above the present sea level, suggesting that there have been two episodes of sea-level highstand. However, radiocarbon dating is likely to be less accurate for dating sediments close to or older than 40–50 ka, the upper limit of its application. We thus explored the applicability of luminescence dating to coastal sediments newly sampled from Langhovde on the eastern coast of Lützow-Holm Bay. Samples were collected from a trench <1 m deep and at several meters above the present sea level. Quartz coarse and fine grains, K-feldspar coarse grains, and polymineral fine grains were extracted from the samples. Quartz coarse and fine grains both showed very low optically stimulated luminescence sensitivity and no fast component and thus were not considered further. Dose-recovery tests on post-infrared infrared-stimulated luminescence (post-IR IRSL) signals of K-feldspar and polymineral grains yielded variable results and suggested acceptable measurement conditions for each grain size fraction and expected equivalent dose. Preliminary measurements revealed that the trench section can be divided into the upper and lower layers, corresponding to the Holocene and MIS 7, respectively. Further application of post-IR IRSL dating to coastal sediments, including to previously radiocarbon-dated sections, could refine our understanding of the late Quaternary relative sea-level history in East Antarctica.

Coastal progradation associated with sea-level oscillations in the later phase of the Last Interglacial period, central Japan

Stratigraphic records of minor sea-level highstands in Marine Oxygen Isotope Stage (MIS) 5c and 5a are valuable archives of late Pleistocene sea levels and paleoenvironments, but have been identified less commonly in siliciclastic coastal systems than the highstand of MIS 5e. In the Kanto Plain, central Japan, the Iioka terrace comprises the seaward margin of the uplifted Last Interglacial (MIS 5) marine terrace. Sedimentological characterization, post-infrared infrared stimulated luminescence (pIRIR) dating, and tephra and paleontological analyses of the Iioka terrace allow identification of a wave-dominated coastal sedimentary system that prograded onto the Pliocene-Pleistocene basement during MIS 5c and 5a. The pIRIR ages of the coastal deposits range from ca. 80 to 112 ka and define a seaward younging trend, which is corroborated by the seaward lowering of the terrace surfaces. In an outcrop in the seaward part, two pIRIR ages were obtained above and below the tephra layer On-Pm1 (95.7 ka), supporting the general validity of the pIRIR chronology. The elevation of beach facies in the landward part (ca. 53 m above the present sea level) abruptly lowers (to ca. 37 m) and is further truncated by fluvial incision in the seaward part. The pIRIR ages include uncertainties that prevent distinction between MIS 5c and 5a. However, the abrupt and large gap in the beach levels between the central and seaward parts suggests the presence of a minor unconformity between MIS 5c and 5a; contemporary uplift may account for the gap. The Iioka terrace is thus interpreted as representing the successive downdip accretion of depositional sequences controlled by relative sea-level changes in the later Last Interglacial period. The refined characterization of the Iioka terrace allows reevaluation of the tectonic uplift rate of this area as ca. 0.7 mm/yr, twice the rate assuming correlation of the deposits with MIS 5e. Such refinement is likely elsewhere if marginal marine terraces are characterized in detail, as carried out here.

Evidence of Former Sea Levels from a Passive Seismic Survey at a Sandy Beach; Perranporth, SW England, UK

Since the end of the last glaciation, the United Kingdom’s land surface has been altered by isostatic rebound, rising in the north and sinking in the south. Numerous studies have been published documenting the impact of isostatic rebound on relative sea levels. However, due to the difficulties in acquiring evidence to prove former sea levels, locally, these data can be sparse or absent. In this work, we explored the suitability of the passive seismic survey (PSS) method to estimate the contemporaneous beach thickness in coastal environments where there is a high impedance contrast between the beach deposits and the underlying wave-cut platform. We conducted a three-day survey at Perran Beach, Cornwall, collected 149 measurements using PSS, and interpreted the observations supported by auxiliary topographical, geological, and independent geophysical observation in the study area. The study site is a contemporaneous beach mostly composed of sand underlain by a wave-cut platform composed of igneous and sedimentary rock, therefore high impedance contrast with the sandy beach is anticipated. The elevation of the bedrock relative to the topographical elevation suggests that the bedrock elevation is −15 m ± 5 m below the present day mean sea level, which is coherent with the observation of relative sea level rise along the region of the south-west. The present study contributes to our current limited understanding of land and sea level movements by providing further subsurface information to the coastal geological archive of south-west England, a region currently in need of more data to reconstruct land- and sea-level movements.

The Elbe Palaeovalley: Evolution from an ice-marginal valley to a sedimentary trap (SE North Sea)

The southeastern North Sea was a sub-aerially exposed periglacial environment during the late Weichselian. At that time, the approximately 210 km long and 40 km wide SE–NW trending Elbe Palaeovalley (EPV) was the main conduit for meltwater from the southern margin of the Scandinavian ice sheet and rivers draining the North European plain. Only few studies investigated the environmental organization of the Northwest European shelves during deglacial sea level rise resulting in vague reconstructions of the drainage systems. Here, a detailed analysis of sediment echo-sounder data and core samples are presented to study the EPV morphology and stratigraphic infill. The valley base is about 65 m below the present sea-level. This SE-NW palaeo-drainage with its braided system developed during the MIS 2 sea level fall and lowstand in a periglacial environment. During deglacial sea-level rise, the EPV evolved into an estuary with tributaries, intertidal and subtidal flats. After the early Holocene (∼10 cal ka BP), ongoing sea-level rise drowned the EPV system which became the major sedimentary trap in the southern North Sea. Successive sea level rise and associated changes in the hydrodynamic regime led to three stages of shelf organization that were recorded in the valley infill successions: (1) shallow basin with restricted connections to Atlantic water; (2) the southwestern connection with the Dover Strait; (3) the open marine environment at 5.8 cal ka BP after the drowning of Dogger Bank.

Mesophotic Depth Biogenic Accumulations (“Biogenic Mounds”) Offshore the Maltese Islands, Central Mediterranean Sea

The mesophotic domain is a poorly explored part of the oceans, notably in the Mediterranean Sea. Benthic communities in these depths are not well documented and as such are under higher risk from anthropogenic impacts. Hard substrate habitats in this depth window are not common and are a key ecotope. The Malta Plateau in the central Mediterranean, which is characterized by low sedimentation rates, offers a potentially unexplored domain for these features. Bathymetric and backscatter data offshore of the eastern coast of the island of Malta were used to identify &amp;gt; 1,700 small structures in mesophotic depths. These structures were verified to be biogenic mounds by dives. The mounds extend from several meters to tens of meters in diameter and occur in two main depth windows −40 to 83 meters below present sea level (mbpsl) and 83–120 mbpsl—each formed probably in a different stage during the last glacial cycle. The mounds are composed of interlocking bioconstruction by encrusting organisms and are colonized by sponges and various cold water corals (most of which are protected; e.g., Madrepora oculata). This unique and important habitat is currently under grave threat by human activity, most immediately by trawling and anchoring activity.

Holocene relative sea-level changes in the eastern part of Pomeranian Bay and the Szczecin Lagoon, Southern Baltic Sea

Sea-level changes of the Baltic Sea have been in the focus since the beginning of Baltic history studies. The main goal of the study is to reconstruct Holocene sea-level changes in the eastern part of Pomeranian Bay and the Szczecin Lagoon. For this purpose, 171 radiocarbon dates were used for the eastern part of Pomeranian Bay and 131 radiocarbon dates for the Szczecin Lagoon. The data allow reconstructing sea-level changes in the last 8500 years in the eastern part of Pomeranian Bay and 7500 years in the Szczecin Lagoon. The sea level 8500 yr b2k was ca. 16 m in Pomeranian Bay, while 7500 yr b2k in the Szczecin Lagoon, it was ca. 8 m below the present sea level. Initially, the fast sea-level rise (up to 9.0 mm/yr) slowed down about 6000 yr b2k to ca. 1.0 mm/yr. In the last 5000 years, the sea level rose at a rate of 0.5 mm/yr in both sites. Analysed data allow distinguishing an extreme event (or events) that disturbed a rather regular course of sea-level rise, which occurred between 7314 and 7022 yr b2k. The history of sea-level changes was similar in the eastern part of Pomeranian Bay and the Szczecin Lagoon despite differences in the geological structure of the pre-Quaternary bedrock and potential various trends in vertical crustal movements. Similarities to some other regions of the southern Baltic and the world ocean allow assuming that sea-level changes in the study area in the last 9000 years in general were eustatic in nature.

Tidal change in response to the relative sea level rise and marsh accretion in a tidally choked estuary

Tidal range is a key factor for flooding, mixing, and transport in estuaries. Sea level rise is expected to change tidal range in the future. This change is complex, and has been showed to either increase or decrease, and vary along the estuary axis. Large changes are expected to occur in costal Louisiana, as it is experiencing some of the highest relative sea level rise (RSLR) rates in the continental USA (0.92 cm yr−1). A finite volume community ocean model was used to investigate how tidal dynamics in Barataria Bay estuary will be affected by future RSLR and marsh accretion scenarios. Under the present sea level condition, five major tidal choking areas – where tidal range reduces sharply, and phase lags develops – were identified. RSLR reduced tidal choking intensity and thus increased tidal range within the estuary. Contrary to previous modeling analyses in other estuaries suggesting that flooding of the low-lying land with sea level rise would increase frictional effects and thus reduce tidal range, this study suggested that tidal range in a choked tidal system like Barataria Bay increases even when accompanied by extensive land inundation. This occurs because the channel conveyance effects are larger than the frictional effects of the low-lying areas. In the lower and the middle bay, the largest increase in tidal range occurred when the marsh area was assumed to keep pace with RSLR. Under this condition, mean tidal range could increase by a maximum of 16 cm compared to the present-day sea level condition. However, in the upper bay the largest increase in tidal range occurred when no accretion was assumed. Under this condition, mean tidal range could increase by a maximum of 13 cm. RSLR also induced amplification of tides at the head of the estuary. A detailed momentum balance analysis indicated that sea level rise shifts tidal wave regime from a dissipative tidal wave to a progressive wave, which is more susceptible to tidal amplification.

Late Pleistocene submarine terraces in the Eastern Mediterranean, central Lebanon, Byblos: Revealing their formation time frame through modeling

Important evidence related to sea-level fluctuation, human evolution and dispersal that took place onshore during the Late Pleistocene and Holocene eras, are currently found underwater due to the sea-level rise. In this study, we present submarine relative paleo sea-level indicators found offshore the Lebanese coastline, at large from the prominent ancient city of Byblos. Two different submarine erosional terrace sequences were identified at depths ranging from −40 to −25m (“distant” sequence) and −11 to 0m (“nearshore” sequence) below present sea level, by using a combination of high-resolution geophysical means and terrain data analysis techniques. In the absence of datings, a model that uses relative sea-level curves for different uplift rates and examines the terraces' formation for various cliff retreat rates (derived from literature and on-field GPS measurements) was built. This model indicates the most possible time frames of the submarine terraces’ (STs) formation. The “nearshore” terrace sequence is suggested to have originally been formed during Marine Isotope Stage 5a (MIS5a) sea-level highstand, while it was possibly re-flattened during the first MIS1 sea-level slowdown (8–6 ka BP). The “distant” sequence formation is placed between the MIS4 to MIS3 transition (∼62–50 ka BP), and during MIS3 sea-level highstands within 45–35 ka BP. It was also found that a long-term uplift rate of 0.28–0.37 mm/a and cliff retreat rate of 0.03–0.09 m/a best fit our data and existing onshore relative sea-level indicators. The formation of the STs at this time was further supported by chronologically intercurrent uplifting events that facilitated their formation and preservation. Finally, our model supports recent ice-sheet reconstructions related to higher MIS3 values since sea-level curves that were tested for this scenario (eustatically reaching up to −37/−38m depth), proved more successful in the formation of the “distant” sequence.

Curation of Digital Archaeological Data in Norway

Archaeological documentation from surveys and excavations in Norway are created by a limited number of actors. Excavations are mainly carried out by the five university museums. NIKU (Norwegian Institute for Cultural Research) is responsible for excavations of medieval cities and churches. Maritime museums excavate in lakes, rivers, and below past and present sea level. Archaeological surveys are mainly the responsibility of the counties. Riksantikvaren (Directorate of National Heritage) is responsible for the national Historic Environment Records (HER), Askeladden, which offers the possibility to upload or insert links to reports from archaeological investigations. Riksantikvaren also archives excavation documentation from churches and medieval cities. The Norwegian university museums have, since the 1990s, cooperated on digitising a national repository and making the collections available online. Presently there are also repositories at the maritime museums, Riksantikvaren and the counties. The infrastructure ADED (Archaeological Digital Excavation Documentation) is a repository for detailed excavation documentation, and the BItFROST infrastructure project contributes to better storage and availability of 3D data. Future development will be more complete national databases, and towards closer international cooperation, creating better integration and availability of several repositories.

Postglacial sea-level lowstand on Cumberland Peninsula, Baffin Island, Nunavut

This study investigates the postglacial sea-level history of eastern Cumberland Peninsula, a region of Baffin Island, Nunavut, where submerged terraces were documented in the 1970s. The elevation gradient of emerged postglacial marine-limit deltas and fiord-head moraines led Arthur Dyke to propose a conceptual model for continuous postglacial submergence of the eastern peninsula. Multibeam mapping over the past decade has revealed eight unequivocal submerged deltas at 19–45 m below present sea level (b.s.l.) and other relict shore-zone landforms (boulder barricade, spits, and sill platform) at 16–51 m b.s.l. Over a distance of 115 km from Qikiqtarjuaq to Cape Dyer, the submerged coastal features increase in depth toward the east, with a slope (0.36 m/km) less than that of the marine-limit shoreline previously documented (0.58–0.62 m/km). The submerged ice-proximal deltas, deglacial ice limits, and radiocarbon ages constrain the postglacial lowstand between 9.9 and 1.4 ka cal BP. The glacial-isostatic model ICE-7G_NA (VM7) computes a lowstand relative sea level at 8.0 ka, the depth of which increases eastward at 0.28 m/km. The difference between observed and model-derived lowstand depths ranges from 1 m in the west to 10 m in the east and the predicted tilt is significantly less than observed (p = 0.0008). The model results, emerging data on Holocene glacial readvances on eastern Baffin Island, and evidence for proglacial delta formation point to a Cockburn (9.5–8.2 ka) age for the lowstand, most likely later in this range. This study confirms the 1970s conceptual model of postglacial submergence in outer Cumberland Peninsula and provides field evidence for further refinement of glacial-isostatic adjustment models.