Showing papers on "Sea-level curve published in 2007"

An inflection in the rate of early mid-Holocene eustatic sea-level rise: A new sea-level curve from Singapore

Abstract: This study presents a sea-level curve from ~9500 to ~6500 cal BP for the farfield location of Singapore, on the Sunda Shelf in southeast Asia. The curve is based on more than 50 radiocarbon dates from elevations of +1.43 m to −15.09 m representing sea-level index points in intertidal mangrove and shallow marine sediments deposited by sea-level rise accompanying deglaciation. The results indicate that mean sea level rose rapidly from around −17 m at 9500 cal BP to around −3 m by 8000 cal BP. After this time, the data suggest (but do not unequivocally prove) that the rate of sea-rise slowed for a period of 300–500 years centred on ~7700 cal BP, shortly after the cessation of meltwater input to the oceans from the northern hemisphere. Renewed sea-level rise amounting to 3–5 m began around 7400 cal BP and was complete by 7000 cal BP. The existence of an inflection in the rate of sea-level rise, with a slow-down centred on ~7700 cal BP, is broadly consistent with other available sea-level curves over this interval and is supported by evidence of stable shorelines and delta initiation elsewhere at this time, as well as evidence of comparatively rapid retreat of the West Antarctic ice sheet beginning around 7500 cal BP. 'Stepped' sea-level rise occurring shortly after 7500 cal BP and also earlier during deglaciation may have served to focus significant post-glacial episodes of human maritime/coastal dispersal, into comparatively narrow time intervals.

A new Holocene sea‐level curve for the southern North Sea

Abstract: Behre, K.-E. 2007 (January): A new Holocene sea-level curve for the southern North Sea. Boreas, Vol. 36, pp. 82–102. Oslo. ISSN 0300–9483. A new sea-level curve (MHW, mean high water level) for the southern North Sea is presented, spanning the last 10000 years and based on new data recently obtained along the German coast. The 118 dates were selected from basal as well as intercalated peats of the Holocene sequence and archaeological dates from the last 3000 years. Because of different MHW levels along the German North Sea coast, all data were corrected to the standard tide gauge at Wilhelmshaven to make them comparable. Special advantages of this area for sea-level reconstructions are negligible tectonic and isostatic subsidence and the absence of coastal barrier systems that might have mitigated or masked sea-level changes. Changes of water level had therefore immediate consequences for the facies and could be dated exactly. The chronostratigraphic Calais-Dunkirk system has been improved and adapted to the new data. Altogether seven regressions (R 1-R 7) have been identified, each of them characterized by a distinct decline in sea level. These fluctuations are in accord with the evidence from other parts of the North Sea region. A draft of former North Sea shorelines is presented on the basis of this sea-level curve.

Microphytoplankton diversity curves of the Chinese Ordovician

Abstract: Following the publication of a regional diversity curve of the Ordovician organic-walled microphytoplankton (acritarchs) from the Yangtze Platform at the species level (Servais et al., 2004), a diversity curve for China is here presented using all literature data at the generic level. The Chinese curve is a compilation of three separate curves from the three major continental blocks that constituted China in the Ordovician: South China (including the Yangtze Platform), Tarim and North China. The diversity changes can partly be related to sea level changes, both at a regional (South Chinese sea level curve) and at a global level (global curve). The totalised curve for all Chinese localities indicates peaks in diversity that apparently correspond to three sea level highstands at a global level at the early-middle Ordovician boundary (middle "Arenigian"), at the Sandbian-Katian boundary (middle "Caradocian") and during the upper Katian (pre-Hirnantian "Ashgillian") Boda Event (Fortey and Cocks, 2005).

Late Quaternary Sea Level Changes on Brock and Prince Patrick Islands, Western Canadian Arctic Archipelago

Abstract: Emerged shorelines are few and poorly defined on Prince Patrick and Brock islands. The sparse radiocarbon dates show emergence of only 10 m through the Holocene on the Arctic Ocean coast, increasing to 20 m 100 km to the east. Hence, from Brock Island, representative of westernmost coasts, the sea level curve since the latest Pleistocene has a very low gradient, whereas on eastern Prince Patrick Island the curve takes the more typical exponential form. A decline in isobases towards the west is thus registered. Drowned estuaries, breached lakes, and coastal barriers, particularly in southwest Prince Patrick Island, suggest that the sea is now transgressing at a rate that decreases towards the north end of the island, hence there is also a component of tilt to the south. Delevelling is assumed to result from undefined ice loads, but may have a tectonic component. The sole prominent raised marine deposit is a ridge probably built in a period of more mobile sea ice, possibly at a time of stable or slightly rising sea level in the middle or early Holocene. It winds discontinuously along several hundred of kilometres of the shores of the Arctic Ocean and connecting channels, declining to the south.

Relict benthic foraminifera in surface sediments off central east coast of India as indicator of sea level changes

Abstract: An attempt has been made to reconstruct sea-level variations along the central east coast of India during the late Pleistocene and early Holocene. A total of 39 surface sediment samples collected from water depth range of 27 – 2,777 m were studied for foraminiferal content. The samples within the depth range of 36-110 m showed presence of relict foraminiferal tests along with recent foraminifers. The relict foraminiferal assemblage of Amphistegina, Operculina, Calcarina and Alveolinella in the selected surface samples is characteristic of coral reef environment and has been inferred as evidence for past low sea levels. Based on extrapolation of previously published radiocarbon dates from the region, we propose a pliable sea level curve for the period between ~9,000 to ~14,000 years BP.

A new AMS 14C-dated Holocene Caspian Sea level curve

Abstract: New data on Holocene Caspian sea level change are presented from the Volga delta in Russia, the Kura in Azerbaijan and the Turali barrier coast in Dagestan. The oldest AMS 14C data from several drillings in the Volga delta suggest a lowstand around 8000 BP, in harmony with earlier data obtained by conventional methods. Volga delta data suggest a continuously rising sea level between 5000 and 3000 BP until a highstand is reached at -25 m around 2600 BP, as documented in the Dagestan barrier coast corresponding with the well-known cool and humid period at the start of the Subatlanticum. The historically well-known mediaeval Derbent regression down to -34 m, and possibly even -45 m, is recorded in the deeper parts of the offshore Kura delta in Azerbaijan, coinciding with the Warm Mediaeval Period, and a second highstand in the Little Ice Age is documented in the outermost barrier in Dagestan. Our data corroborate a correlation of Caspian Sea Level with changes in solar activity.