Pingos in Denmark A comparison between pingo remnants in the Netherlands and circular depressions in South Jutland Utrecht University Faculty of Geosciences Department of Physical Geography 4th of July 2016 By: Machteld Caspers (3594254) Supervisor: dr. W.Z. Hoek Co-supervisor: PhD candidate Marjolein T.I.J. Gouw-Bouman 0 Abstract Continuous and discontinuous permafrost zones extended over large parts of north-western Europe during the Weichselian glaciation, presumably as a result of hydrostatic groundwater pressure in partially frozen aquifers. This led to the formation of pingos regionally, in a fringe around the maximum extent of the ice sheet. In addition to the Netherlands, hardly any studies (Kolstrup, 1985) have focussed on the possible presence of pingo remnants further north, closer to the Sciandinavian Ice Sheet front, like Denmark. This study aims to present evidence of pingo remnants in Denmark and to compare this evidence with pingo remnants found in the Netherlands. A DEM and field survey in Southern Jutland revealed some of the characteristic geomorphological pingo remnant features, such as large isolated circular depressions. Moreover, the infill of one of the circular depressions appears to be comparable to that of pingo remnants in the Netherlands. The palynological results show a typical Late Glacial infill at the base. These first results are not conclusive, but they indicate that it is likely that some circular depressions in Denmark can be regarded as pingo remnants. I Table of contents Abstract ________________________________________________________________________ I Table of contents ________________________________________________________________ II List of figures ___________________________________________________________________ IV List of tables ____________________________________________________________________ V 1. Introduction ________________________________________________________________ 1 2. Circular depressions in former (peri)glacial environments ___________________________ 3 2.1 Pingos _____________________________________________________________________________ 3 2.1.1 Hydrostatic (closed-system) pingos __________________________________________________ 4 2.1.2 Hydraulic (open-system) pingos ____________________________________________________ 5 2.2 Pingo failure and decay _______________________________________________________________ 7 2.2.1. Mechanically induced failure ______________________________________________________ 7 2.2.2 Climatic failure __________________________________________________________________ 8 2.3 Pingo remnants _____________________________________________________________________ 9 2.4 Alternative explanations _____________________________________________________________ 11 2.4.1 Pitted Sandar with kettle holes ____________________________________________________ 11 2.4.2 Palsas ________________________________________________________________________ 12 2.4.3 Small perennial ice-cored mounds _________________________________________________ 12 3. Vegetation development _____________________________________________________ 14 3.1 The Netherlands ___________________________________________________________________ 14 3.1.1 Zone 1 ________________________________________________________________________ 14 3.1.2 Zone 2 ________________________________________________________________________ 15 3.1.3 Zone 3 ________________________________________________________________________ 15 3.1.4 Zone 4 ________________________________________________________________________ 16 3.1.5 Zone 5 ________________________________________________________________________ 16 3.2 Denmark _________________________________________________________________________ 16 4. Study area _________________________________________________________________ 17 4.1 Glacial history _____________________________________________________________________ 17 4.1.1 Saalian _______________________________________________________________________ 17 4.1.2. Weichselian ___________________________________________________________________ 18 4.2 Location and local deposits ___________________________________________________________ 19 4.2.1 Drenthe, the Netherlands ________________________________________________________ 19 4.2.2 South Jutland, Denmark __________________________________________________________ 20 5. Methods __________________________________________________________________ 21 5.1 Fieldwork _________________________________________________________________________ 21 5.1.1 Area selection __________________________________________________________________ 21 5.1.2 Site selection __________________________________________________________________ 21 5.1.3 Coring ________________________________________________________________________ 21 5.1.4 Bathymetry ____________________________________________________________________ 22 5.2 Laboratory methods ________________________________________________________________ 22 5.2.1 Lithological description __________________________________________________________ 22 5.2.2 Loss On Ignition ________________________________________________________________ 23 5.2.3 CaCO3 ________________________________________________________________________ 23 5.2.4 Pollen analysis _________________________________________________________________ 24 II 5.3 Age model ________________________________________________________________________ 24 6. Results ___________________________________________________________________ 25 6.1 Geomorphology and lithology _________________________________________________________ 25 6.1.1 Blauw Gat, the Netherlands _______________________________________________________ 26 6.1.2 Groot Veen, the Netherlands ______________________________________________________ 29 6.1.3 MIK, Denmark _________________________________________________________________ 32 6.1.4 PAD, Denmark _________________________________________________________________ 34 6.2 LOI results ________________________________________________________________________ 36 6.2.1 Blauw Gat, the Netherlands _______________________________________________________ 36 6.2.2 Groot Veen, the Netherlands ______________________________________________________ 37 6.2.3 MIK, Denmark _________________________________________________________________ 38 6.2.4 PAD, Denmark _________________________________________________________________ 38 6.2.5 Interpretation and preliminary conclusions Dutch sites _________________________________ 39 6.2.6 Interpretation and preliminary conclusions Danish sites ________________________________ 39 6.3 Pollen results ______________________________________________________________________ 41 6.3.1 Pollen diagram Blauw Gat, the Netherlands __________________________________________ 41 6.3.2 Pollen diagram Groot Veen, the Netherlands _________________________________________ 42 6.3.3 Pollen diagram MIK, Denmark _____________________________________________________ 44 6.3.4 Pollen diagram PAD Denmark _____________________________________________________ 45 6.3.5 Interpretation and preliminary conclusions Dutch pollen spectra _________________________ 46 6.3.6 Interpretation preliminary conclusions Danish pollen spectra ____________________________ 47 7. Discussion _________________________________________________________________ 48 7.1 Geomorphology ____________________________________________________________________ 48 7.2 Lithology _________________________________________________________________________ 48 7.3 LOI ______________________________________________________________________________ 49 7.4 Pollen diagrams ____________________________________________________________________ 50 7.5 Combining the results _______________________________________________________________ 50 8. Conclusions ________________________________________________________________ 52 9. References ________________________________________________________________ 54 10. Appendices _________________________________________________________________ 58 10.1 Pollen preparation guidelines (Dutch) _________________________________________________ 58 10.2 Coring descriptions ________________________________________________________________ 60 10.3 Complete LOI graphs _______________________________________________________________ 66 10.4 Complete pollen diagrams __________________________________________________________ 68 10.5 Pollen diagram Rijks Geologische Dienst _______________________________________________ 72 III List of figures Figure 1: Formation of a hydrostatic (closed system) pingo (Harris & Ross, 2007) ................................................. 5 Figure 2: Formation of a hydraulic (open-system) pingo (Yoshikawa, 2013) .......................................................... 6 Figure 3: Dilation cracking in a pingo (Mackay, 1998) ............................................................................................ 8 Figure 4: Relationship pingo collapse and temperature; a) climatic warming scenario, b) climatic stable scenario, c) climatic cooling scenario ( Mackay, 1988) .......................................................................................................... 9 Figure 5: Different types of pitted sandar ( Benn & Evans, 2010) ......................................................................... 12 Figure 6: Marked approximation of the study area (black box), focus areas (red circles) and glacial configuration of Scandinavian Ice Sheet during the Late Saalian (white