Universiteit Utrecht
, Geomorphological evidence (2)
Indicator value: glacial forms are often only a qualitative indicator of past glacial conditions. However,
the geographical extent can be used to estimate past climate conditions quantitatively.
Striations: indicative of past glacial activity, together with crescentic scars; indicators of ice flow
directions.
Drumlins: elongated hill, formed by glacial ice acting on underlying unconsolidated till or moraine. Have
no sedimentary structures (very mixed) and show the flow direction
Eskers: long, winding ridge of stratified sand and gravel (glacial maximum), formed within ice-walled tunnels
by streams which flowed within and under glaciers. Indicate ice conditions, not the ice flow direction.
Pingo: Closed system (continuous permafrost), open system (discontinuous permafrost + depth related to
permafrost thickness, 20m in North-NL and 3m in South-NL.). First one is described in the Netherlands in
1955.
- Pingo too steep, insulating sediment cover slips down and ice will melt result is a rim around a lake.
- After final melting of permafrost due to T rise, a circular lake with or without a rim is formed
Pleniglacial; formation of ice lense under permafrost conditions
Late pleniglacial; growth of pingo with shrub vegetation cover (betula nana, salix herbacea) Early
lateglacial (bølling interstadial); decay of pingo due melting permafrost
Lateglacial (allerød interstadial); permafrost completely disappeared and a lake exists with remains of the
cover at the bottom
Present day; nearly complete lateglacial – Holocene fill with younger dryas sand layer
Palsa: Low, oval, frost heave occurring in polar and subpolar climates. Contains permanently frozen ice
lenses, discontinuous permafrost, smaller than pingo. Are formed in peat.
Site selection and sampling (3)
Site selection by mapping detailed cross sectioning coring (not just boring) work precisely
take good notice and notes Different methods require different materials
Activity; point bar deposits = OSL
End of activity; residual channel fill = Pollen + 14C | plug bar deposits: OSL
Normal coring for sandy deposits: Edelman and van der Staaij suction-corer
Clay and peat: Open gouge (possible contamination)
Sandy deposits: van der Horst (real corer hammered into sediment) Closed
chambers: Russian corer
Exact depth, no contamination, light weight (2p), hand corer, small sample size, 50 cm recovery
Bohncke-boor
Piston corer (no contamination), middle weight (3p), hand corer, large sample size, 100 cm recovery
Livingstone piston corer
Coring frame (powerful), no contamination, heavy weight (4p), hand corer with frame, largest sample size,
100 cm recovery
Uwitec coring platform: for lakes
Clay deposits; flooding, Soil horizons; no flooding
