Abstract
AbstractRelative sea-level (RSL) data provide constraints on land uplift associated with former ice loading and can be used to differentiate between contrasting ice unloading scenarios. Isolation basin, coastal lowland and geomorphological evidence is employed to reconstruct RSL changes in northwest (NW) Iceland, which may have experienced contrasting uplift patterns. Under local (NW) uplift, highest RSL would be expected in central Vestfirðir, whereas highest RSL would be closest to the main ice-loading centre under regional (central Iceland) uplift. Four new RSL records are presented based on 16 sea-level index points and 4 limiting ages from sites principally focussed along a transect away from central Iceland. The new RSL records highlight spatial variability of Holocene RSL changes and provide constraints on deglaciation. There is an increase in marine limit elevation with proximity to the proposed principal ice loading centre in central Iceland. Highest recorded marine limit shorelines are found in Hrútafjörður-Heggstaðanes (southeast), the lowest in Hlöðuvík and Rekavík bak Látrum (north), and at an intermediate elevation in Reykjanes-Laugardalur (central Vestfirðir). Evidence from Breiðavik-Látrar records early rapid deglaciation in Breiðafjörður or a complex interplay of multiple uplift centres. RSL fell rapidly following deglaciation in several locations as a result of the quick response of the Icelandic lithosphere to unloading. The RSL data along the transect show an uplift pattern consistent with extensive regional glaciation emanating from central Iceland, which could have implications for ice sheet configuration and patterns of deglaciation, glacio-isostatic adjustment modelling and the volume of meltwater input into the North Atlantic.
Highlights
Isolation basin and coastal lowland evidence from NW Iceland demonstrates spatial variability in Relative sea-level (RSL) changes recorded in the region
These differences are shown through the elevation of the local marine limit in Hlo€ðuvík and Rekavík bak Latrum (NW), Reykjanes-Laugardalur and Hrútafjo€rður-Heggstaðanes (SE), as well as the rates of subsequent RSL changes
There is evidence for RSL fall below present sea level during the early Holocene
Summary
A range of evidence has been used to investigate the lateral and vertical extent of the Last Glacial Maximum (LGM) Icelandic Ice Sheet (IIS), including glacial geomorphology, striation mapping (e.g. Thoroddsen, 1905e1906; Hoppe, 1968, 1982), sedimentology (e.g. Syvitski et al, 1999; Andrews et al, 2000), seismic profiling (Egloff and Johnson, 1979), submerged feature mapping (Spagnolo and Clark, 2009), ice sheet modelling (Hubbard et al, 2006; Hubbard, 2006), marine limit mapping (Norðdahl and Petursson, 2005; Norðdahl et al, 2008), and ocean coring (Andrews et al, 2000; Eiríksson et al, 2000). Lloyd and Evans, 2002) and analysis of sediment and microfossil datasets allows the identification of three isolation contacts e diatomological, hydrological and sedimentological - which can subsequently be linked to positions within the tidal frame (Kjemperud, 1986). Radiocarbon dates at these isolation contacts provide constraints on the timing of RSL change and the resulting RSL curves may in turn determine patterns of postglacial land-level change Radiocarbon dates at these isolation contacts provide constraints on the timing of RSL change and the resulting RSL curves may in turn determine patterns of postglacial land-level change (e.g. Long et al, 2011), allowing an assessment of former ice loading patterns
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