Holocene Relative Sea-level History Research Articles

The middle-to-late Holocene relative sea-level history, highstand and levering effect on the east coast of Malay Peninsula

This study was conducted to (1) investigate a former mangrove wetland on the east coast of Peninsular Malaysia near Kuantan and produce new sea-level index points (SLIP), and to (2) re-analyzed the modern vegetation and pollen results from a mangrove-swamp transect within the nearby estuary to establish the relationship between vegetation zones and tidal levels for estimating indicative meanings (IM) for the SLIPs. The results indicate that the modern floral and pollen zones match well with the fossil ones, and four IMs were appropriately established. Combining with the recently published SLIPs from Terengganu, the 15 new SLIPs from Kuantan were used to reconstruct the middle-to-late Holocene relative sea-level (RSL) history for the east coast of the Malay Peninsula. This history shows that the RSL reached c. 1.5 m msl around 6500 cal. a BP and rose to c. 2.0 m msl by 4500 cal. a BP. This phase of RSL rise in this far-field site supports the hypothesis that additional ice melting occurred between 7000 and 4000 cal. a BP. During this phase of RSL rise, erosion and redeposition of estuarine sediments occurred at the study site. Since 4000 cal. a BP, the RSL fell gradually to below the present height by 800 cal. a BP. In general, this RSL history matches well with the GIA model with the ICE4G melting history. Furthermore, the SLIPs from the east coast are systematically lower in elevation than those recorded in the west coast. The difference is about 1.5 m in the beginning of the middle Holocene and it decreases gradually towards the late Holocene. This difference, thus, implies the existence of continental levering during the Holocene.

Paleoclimate and Holocene relative sea-level history of the east coast of India

The Holocene sea-level history of the east coast of India is relatively unexplored. We analysed a 17.37-m-long sediment core from Kolleru Lake, a fresh waterbody located in a deltaic setting along the east coast of India, to reconstruct the climate, environmental, and sea-level history of the region. Sedimentary facies and pollen assemblages, with nine accelerator mass spectrometry 14C dates (two mollusk shells and seven plant samples) from the core revealed Holocene relative sea-level changes, and provide the first insights into the climate of the region from the Last Glacial Maximum (LGM) to present. A layer of anhydrous calcium sulfate at the core bottom, along with a 14C age of 18.4 cal ka BP, combined with the absence of pollen in mottled yellowish clay, indicated a desiccated lake surface, reflecting a dry LGM climate. Palynomorphs in the overlying calcareous-concretion-bearing light brown silty clay showed a change from arid terrestrial herbaceous plants to freshwater taxa, indicating a change from dry to wet climate after the LGM and before 8.0 cal ka BP. Further upward in the core, black, sticky silty clay with abundant mangrove pollen and mollusk shells indicated a marine environment in Kolleru Lake and aggradational sediment stacking related to the middle Holocene sea-level rise from 8.0 to 4.9 cal ka BP. The uppermost sandy/silty clay, with terrestrial/aquatic pollen and a 14C age of 3.7 cal ka BP indicated a freshwater environment during the late Holocene. Our results show that Kolleru Lake, on the east coast of India, changed from a desiccated state during the dry LGM to a brackish lagoon during the middle Holocene, and then to a freshwater lake by the late Holocene, under the influence of climate and relative sea-level changes.

A below-the-present late Holocene relative sea level and the glacial isostatic adjustment during the Holocene in the Malay Peninsula

This study has reconstructed the Holocene relative sea-level history in the relatively tectonically stable Malay Peninsula with two specific objectives: quantifying the sea-level indicative meanings of mangrove sediments and producing new high-quality sea-level index points. In this study, a wetland on the east coast of the Peninsula was extensively surveyed; the elevational relationship between habitat zones and their pollen and diatom assemblages was established; and a number of indicative meanings were precisely quantified for this wetland. This quantified relationship is extrapolated to other coastal sites of the Peninsula for re-calibration of previously published mangrove-based sea-level data. The reconstructed sea-level history from the new and re-calibrated data demonstrates a period of rapid sea-level rise at a rate of 15.8 ± 3.9 mm/a between 10,500 cal a BP at −35.0 ± 4.3 m and 9000 cal a BP at −14.2 ± 1.6 m. The rate of rising sea level was gradually reduced to zero from 9000 to 5000 cal a BP, and by the end of this period the relative sea level reached a highstand of c. 3.3 ± 0.2 m. Over the past 5000 years relative sea level fell to its lowest point at −0.6 ± 0.1 m by 800 cal a BP. This far-field sea-level history has been driven by the global ice-volume change and glacial isostatic adjustment, and it matches well with the modelled ice-volume equivalent sea level.

A base-level stratigraphic approach to determining Holocene subsidence of the Ganges–Meghna–Brahmaputra Delta plain

Relative sea level history, which is the result of the combined effects of land subsidence, sediment supply and absolute sea level history may be reconstructed from preserved sediment thicknesses. However, variations in the preserved sediment thicknesses between different sedimentary environments strongly limit the accuracy of this type of geological approach, particularly in fluvial channelized systems, such as delta plains. To address this, we apply three different and independent stratigraphic approaches to the case of the Ganges–Brahmaputra–Meghna Delta (GBMD). Our approach has been made possible by a broad dataset of geological archives we have collected, which includes more than 400 hand-drilled stratigraphic wells, 198 radiocarbon ages, and river seismic reflection data (255 km of high-resolution multichannel seismic images). The seaward gradient of accommodation and the limit of the subsiding delta plain are estimated, assuming that the delta is near or at the base-level, which is considered to be the relative sea-level. First, a statistical analysis of the variability of preserved sediment thicknesses is used to derive the average pattern of accommodation from the Holocene isopach. Secondly, the preserved sediment thicknesses are analyzed by geomorphotectonic domains to estimate an average pattern of accommodation. Thirdly, the burial history of the seismically imaged last glacial incision of the Brahmaputra River is reconstructed. Results suggest that the variability of preserved sediment thicknesses can be up to 35% in a delta plain between river channel and flood plain deposits for the same relative sea-level history. Taking this variability into consideration, the Holocene relative sea-level history of the GBMD and the most likely pattern of subsidence are determined. Results provide evidence of moderate Holocene subsidence over the delta, gently increasing seaward from <0.2 mm/yr landward of the Hinge Zone, which can be considered as the northern limit of the subsiding delta plain, to 2 ± 0.7 mm/yr in the middle fluvial delta to 4 ± 1.4 mm/yr in the lower tidal delta. This enables us to construct the first millennial-scale map of subsidence pattern on the GBMD in which uncertainties on subsidence rates are provided. This map may aid in evaluating the negative impact that human modification may have on subsidence and relative sea level in the GBMD, and thereby help to determine better sustainable coastal management practices for the GBMD and other large delta plains.

Holocene relative sea level history and Storegga tsunami run‐up in Lyngen, northern Norway

ABSTRACTWe re‐investigated three isolation basins in Lyngen in Troms, Norway, that contained a mixed facies of terrestrial and marine origin. Here we show that the mixed facies was deposited by the Storegga tsunami. We reconstruct the run‐up of the tsunami to 6–7 m above mean sea level of that time, in agreement with numerical modelling. In addition, our new cores revealed a layer of lake‐gyttja below marine deposits, and radiocarbon ages of plant fragments extracted from that gyttja date the sea level lowstand to 9400 cal a BP. These ages, and our new understanding of the mixed facies as Storegga tsunami deposits, improve the previously published sea‐level curve. The radiocarbon age of a sea urchin, assumed to have been killed in the Storegga tsunami event, shows that the reservoir age of the coastal waters in Troms was 400 years (ΔR = 45 ± 41) at that time − similar to the present‐day value.

Holocene relative sea level history from phreatic overgrowths on speleothems (POS) on Minami Daito Island, Northern Philippine Sea

This research aims to elucidate the Holocene sea level (SL) variability on Minami Daito Island, Japan, where no previous such research has been done due to the apparent absence of any SL indicators. Here we use phreatic overgrowths on speleothems (POS) in a cave as an alternative SL indicator. The relationship between the highest modern groundwater fluctuation level (GWFL) and the highest POS level was studied, and the oldest POS calcite was dated using the radiocarbon method considering the dead carbon proportion (the “reservoir effect”). The results show that SL reached its Holocene maximum between ca. 5.1 and 4.6 ka cal BP, after which it remained more or less stable till the present day, with a possible minor sea-level drawdown of ca. 30–35 cm. Although the timing of the maximum Holocene SL coincides with mid-Holocene SL highstand observed across the tropical and subtropical Indo-Pacific, the relative stability of the SL after reaching its peak is not expected in the given subtropical setting. The SL on Minami Daito did not have a distinct highstand in the Holocene and instead followed closely the eustatic sea-level change. These findings are important in better understanding the mechanisms that control local relative SL variability and show the high value of POS as precise SL indicator.

A Revised Late Holocene Sea-Level Record for Northern Massachusetts, USA

Abstract Accelerator mass spectrometry (AMS) radiocarbon dating of basal high-marsh sediments from Romney Marsh, Revere, Massachusetts, provides a revised reconstruction of the late Holocene relative sea-level history of the region. After correction for changes in tidal amplitude, the sea-level change envelope reconstructed from five AMS radiocarbon dates of basal marsh sediments at Romney Marsh in Revere, Massachusetts, indicates a rise in mean sea level (MSL) of close to 2.6 m in the past 3300 years. The data indicate a possible decrease in the average rate of rise from 0.80 ± 0.25 mm/y between 3300 to 1000 YBP to a rate of 0.52 ± 0.62 mm/y between 1000 YBP and the past 150 to 500 years. An increase in the rate of sea-level rise is evident over the past few hundred years. A slowing of the rate of sea-level rise between 1000 YBP and historic times and the increase in the rate of rise to modern values is also evident in other sea-level records from Maine and Connecticut. The coherence between these sea-le...

Late Holocene sea-level changes and isostasy in western Denmark

Cores and exposed cliff sections in salt marshes around Ho Bugt, a tidal embayment in the northernmost part of the Danish Wadden Sea, were subjected to 14C dating and litho- and biostratigraphical analyses to reconstruct paleoenvironmental changes and to establish a late Holocene relative sea-level history. Four stages in the late Holocene development of Ho Bugt can be identified: (1) groundwater-table rise and growth of basal peat (from at least 2300 BC to AD 0); (2) salt-marsh formation (0 to AD 250); (3) a freshening phase (AD 250 to AD 1600?), culminating in the drying out of the marshes and producing a distinct black horizon followed by an aeolian phase with sand deposition; and (4) renewed salt-marsh deposition (AD 1600? to present). From 16 calibrated AMS radiocarbon ages on fossil plant fragments and 4 calibrated conventional radiocarbon ages on peat, we reconstructed a local relative sea-level history that shows a steady sea-level rise of 4 m since 4000 cal yr BP. Contrary to suggestions made in the literature, the relative sea-level record of Ho Bugt does not contain a late Holocene highstand. Relative sea-level changes at Ho Bugt are controlled by glacio-isostatic subsidence and can be duplicated by a glacial isostatic adjustment model in which no water is added to the world's oceans after ca. 5000 cal yr BP.

Holocene relative sea-level history of the Southern Victoria Land Coast, Antarctica

More than 130 radiocarbon dates of penguin remains and guano, sealskin, shells, and seaweed from raised beach ridges afford relative sea-level information for southern Victoria Land. A new relative sea-level curve suggests that the final unloading of grounded ice from the coast took place about 6600 14C years BP, in keeping with previous estimates of the timing of deglaciation. Since this time, the coast has experienced 32 m of relative sea-level fall at rates ranging from 2 to 15 mm/year, consistent with glacioisostatic rebound.

Coastal morpho-stratigraphy and Holocene relative sea level changes at Tuapaat, southeastern Disko Island, central West Greenland

The geomorphology of a coarse clastic coastal landscape at Tuapaat (69°24'N 52°36'W), southeastern Disko Island, central West Greenland, is described, and a coastal morpho-stratigraphy of the landscape is constructed. 14C ages on marine shells, whale bones, peat and gyttja are used to construct relative sea level changes throughout the Holocene. The emergence of SE Disko Island occurred in the early part of the Holocene. The Holocene marine limit is situated ca. 80m a.s.l. Between 4.7 and 1.0ka BP, the relative sea level approached the present sea level and it has probably been below present sea level between 4.7 ka BP and the present. The morpho-stratigraphy in the lowest part of the coastal landscape at Tuapaat suggests a complex late Holocene relative sea level history which includes at least 3-4 transgressions during the last ca. 2.5 ka.

Holocene Relative Sea-Level Changes Indicated by Morphostratigraphic Sequences; Sinigfik, Disko Island, West Greenland

Morten Rasch & Niels Nielsen: Holocene Relative Sea-level Changes Indicated by Morphostratigraphic Sequences; Sinigfik, Disko Island, West Greenland. Geografisk Tidsskrift, Danish Journal of Geography 94:xx–xx, Copenhagen, Dec. 1994. A morphostratigraphic method is introduced in a study of Holocene relative sea-level changes at Sinigfik on the south coast of Disko Island, West Greenland. The method allows detection of relative sea-level rise interrupting the general Holocene emergence. It is concluded that the Holocene relative sea-level history at Sinigfik was one of steady emergence prior to c. 3 ka B P. A complex morphostratigraphic sequence near the present coastline might result from two emergence/submergence events within the last millenium. The geomorphology of the present coastline indicates extensive coastal recession, probably resulting from a relative sea- level rise at present.