Using sediment facies & ground penetrating radar profiles to investigate the internal architecture and genesis of De Geer moraines

• DOI: 10.5194/egusphere-egu24-574
• Publication Date: 2024-03-08T09:25:42Z
• Authors: Gwyneth Rivers; Robert Storrar; Joni Mäkinen; Antti Ojala; Naomi Holmes; Camilla Holmroos

De Geer moraines (DGMs) have the potential to generate very high-resolution spatial and temporal ice margin reconstructions (~annual in contrast 100-500 years, current state-of-the-art). Existing studies suggest that DGMs likely form annually a sub-aqueous, ice-marginal environment whereby basal sediments are advected deposited at grounding-line during seasonal advances. However, there also been suggestions of crevasse-fill origin challenges this regularity. Whilst spatiotemporal properties disputed, balance evidence suggests an depositional with annual/seasonal regularities. Understanding processes related DGM formation is therefore critical, as it underpins ability use delineate retreat unprecedented (potentially annual) resolutions. A recent large-scale 3D morphometry study Crevasse-Squeeze Ridges (CSRs) was undertaken constrain landform metrics explore their processes. The results revealed statistically significant differences across all morphometrics between sampled CSRs. were found be lower-relief, narrower, slightly more asymmetrical, sinuous than studied support marginal environment. Furthermore, tendencies for cross-sectional asymmetry unidirectional push movement involved formation. These inferences, however, must supported geophysical and/or sedimentological investigations. Here we present field using (Ground Penetrating Radar) techniques investigate internal architecture southwest Finland. Sedimentological data acquired from two excavated exposures 55 GPR profiles obtained four different locations SW Radar facies identified corroborated lithofacies units observed ca. 30 m long trench excavations. Typically, these comprise stacked thrusted planes laminated clay diamicton on proximal slopes, sheared surfaces indicative proglacial pushing/overriding, gravity-driven flow deposits distal slopes. At places, glaciotectonic structures such dipping, faults folds identified. may used complement existing study, constraining main validating indicators. This can ultimately foundation climatic significance ridges, thus meriting further work deglaciation.