Beach-ridge architecture constrained by beach topography and Ground-Penetrating Radar, Itilleq (Lakse Bugt), Disko, Greenland – Implications for sea-level reconstructions.

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Detailed topographical data and high-resolution ground-penetrating radar (GPR) reflection data are presented from the present-day beach and across successive raised beach-ridges at Itilleq (Disko, West Greenland). In the western part of our study area, the present low-tide level is well-marked by an abrupt change in clast size, between the sandy foreshore and the upper shoreface, which is characterized by frequently occurring large clasts. The main part of both fine and large clasts appears to be locally derived. Seaward-dipping reflections form down-lap points, which are clearly identified in all beach-ridge GPR profiles. Most of them are located at the boundary between a unit with reflection characteristics representing palaeo foreshore deposits, and a deeper and more complex radar unit characterized by diffractions, which, however, is not penetrated to large depths by the GPR signals. Based on observations of the active shoreface regime, large clasts are interpreted to give rise to scattering observed near the top of the deeper radar unit. We regard the down-lap points located at this radar boundary as markers of palaeo low-tide level. In some places, scattering hyperbolas are more pronounced and frequent than in others, suggesting differences in the occurrence of large boulders.
Original languageEnglish
JournalBulletin of the Geological Society of Denmark
Pages (from-to)167-179
Number of pages13
Publication statusPublished - 2018

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