Abstract
Identification of sea-level proxies is important for reconstruction of past sea-level variation. Methods for reconstructing Holocene relative sea-level curves are crucial for quantification of the impact of Greenland ice thickness variation on global sea level and vertical land movement. Arctic beach ridges constitute important potential archives of sea-level variation. However, their surface morphology may have undergone modification since deposition due to freezing/thawing processes and erosion, and their morphology may therefore not be trustworthy for sea-level reconstruction. Therefore, geophysical imaging is used to examine the internal structures of the beach ridges and to define a sea-level proxy unaffected by surface processes. The GPR reflections from study sites in West and South Greenland show deposition of beachface deposits and upper shoreface deposits; the contact between steeply dipping beachface reflections and less-dipping shoreface reflections is used as sea-level proxy. Numerous points are identified along GPR transects facilitating reconstruction of relative sea-level variation of hitherto unprecedented resolution. Erosional events and deformation caused by freezing/thawing processes are clearly delineated. The approach constitutes a solid base for reconstruction of relative sea-level curves affected by a well-defined vertical land movement history since the studied beach ridge systems represent long time intervals and only relatively small spatial extents.
Highlights
Curves of relative sea-level variation during the Holocene in Greenland and the surrounding Arctic are critical for our understanding of past and present absolute sea-level change as well as to reveal the impact of vertical land movement due to ice sheet thickness variations or other effects[1,2,3]
The three study sites investigated here represent areas where the surface morphology of the beach ridge systems is exposed to varying extent
The final processed data facilitate interpretation of internal beach ridge system layering and structure with the same degree of resolution as obtained at other study sites in temperate regions, where beach ridge systems are composed of finer-grained mixed sand and gravel[19,20,26]
Summary
Curves of relative sea-level variation during the Holocene in Greenland and the surrounding Arctic are critical for our understanding of past and present absolute sea-level change as well as to reveal the impact of vertical land movement due to ice sheet thickness variations or other (e.g. tectonic) effects[1,2,3]. Several studies of Holocene sea-level changes in Greenland and the surrounding Arctic have been made based on geological and geographical investigations of e.g. isolation basins, beach ridge morphology, salt marsh deposits, and mapping of paleo-shorelines[2,4,5,6,7,8,9,10,11,12,13]. Markers of-sea-level have been identified in GPR data collected in fossil beach deposits in Japan[16] and in the micro tidal environment of southwest Scandinavia[23] Such markers allow for detailed reconstruction of Holocene sea-level variation[19,20,26]
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