GENESIS OF THE HONDSRUG A SAALIAN MEGAFLUTE, Drenthe, the Netherlands ASPIRING EUROPEAN GEOPARK September 2012 E.P.H.Bregman F.W.H.Smit PROVINCE OF DRENTHE UTRECHT UNIVERSITY THE NETHERLANDS www. Geoparkdehondsrug.nl 1 Colophon E.P.H. Bregman, MSc, Province of Drenthe, Utrecht University. Adress: Province of Drenthe, Westerbrink 1, 9400 AC Assen. E-mail: [email protected] F.W.H. Smit, BSc Utrecht University, MSc Århus University (Denmark) E-mail: [email protected] This report is published by the Steering Group aspiring EUROPEAN GEOPARK de Hondsrug and will (partly or modified) be published as part of a Ph-D thesis of E.P.H.Bregman. Reprodution of this study (text and figures) at any way, or using data for presentations, lectures or publications is only allowed with permission of the main author, E.P.H.Bregman. © (2012) Steering Group aspiring EUROPEAN GEOPARK de HONDSRUG/E.P.H.Bregman This study is ordered by the Province of Drenthe and study is done under auspiciën of the Utrecht University, Faculty Geoscience, department Physical Geography. The Netherlands 2 Contents List of figures............................................................................................................................ 6 A proposed European Geopark................................................................................................ 8 1. Introduction.....................................................................................................................11 1.1 Framework of the research.............................................................................................. 11 1.2 Geological setting............................................................................................................. 12 1.2.1 Large-scale geological context .................................................................................. 12 1.2.2 Salt diapirs................................................................................................................. 13 1.2.3 Shallow substratum .................................................................................................. 14 1.2.4 Hondsrug ice stream area ......................................................................................... 16 1.3 Aim of the research.......................................................................................................... 18 1.4 Hondsrug Regional Research History ............................................................................... 19 1.4.1: 1880–1900 Prof. F.J.P. van Calker: the Hondsrug as an end moraine...................... 19 1.4.2: 1902–1907 Prof. E. Dubois vs Dr H.G. Jonker........................................................... 19 1.4.3: 1950–1980 Maarleveld, Ter Wee, Zonneveld, de Gans ........................................... 21 1.4.4: 1980–1990 Rappol, Zandstra, Van den Berg and Beets (1987)................................ 21 1.4.5: 2008–2012 Pierik, Bregman and Cohen................................................................... 22 2. Methods and materials....................................................................................................26 2.1 Methods of data collection.............................................................................................. 26 2.2 Methods of data interpretation....................................................................................... 26 2.3 Hondsrug area and Study of ice streams ......................................................................... 29 3. Glacial sediments and subglacial deformation..................................................................32 3.1 Deformation horizons in an unlithified bed according to Boulton (1995) ....................... 32 3.2 Ice flow affecting the glacier bed..................................................................................... 33 3.2.1 Boulton and Jones’ (1979) deformation model ........................................................ 33 3.2.2 Hallet’s (1996) deformation model........................................................................... 35 3.3 Abrasion models .............................................................................................................. 35 3.4 Reversed groundwater flows ........................................................................................... 36 3.5 The floting mechanism..................................................................................................... 37 3.6 Saltdome geothermal heatflow below ice ....................................................................... 39 3.7 Types of till on the Hondsrug complex............................................................................. 41 4. Lithological observations on the Hondsrug.......................................................................45 3 4.1 Location 1: Donderen area............................................................................................... 45 4.1.1 Geological interpretation.............................................................................................. 47 4.2 Location 2: Gieten............................................................................................................ 48 4.2.1 Structures.................................................................................................................. 50 4.2.2. Geological interpretation ......................................................................................... 50 4.3 Location 3: Gasselte......................................................................................................... 53 4.3.1. Structures................................................................................................................. 53 4.3.2 Geological interpretation.......................................................................................... 53 4.4 Location 4: Borger............................................................................................................ 54 4.4.1 Structures.................................................................................................................. 55 4.4.2. Geological interpretation......................................................................................... 57 4.5 Location 5: Valthe/Odoorn: GPR measurements............................................................. 58 4.5.1 Structures.................................................................................................................. 58 4.5.2. Geological interpretation............................................................................................. 59 4.6 Location 6: Klazienaveen.................................................................................................. 60 4.6.1 Structures............................................................................................................. 63 4.6.2 Geological interpretation.......................................................................................... 63 5. Glaciological interpretation ........................................................................................65 5.1 Location 1: Donderen....................................................................................................... 65 5.2 Location 2: Gieten............................................................................................................ 65 5.3 Location 3: Gasselte ..................................................................................................... 67 5.4 Location 4: Borger ........................................................................................................ 68 5.5 Location 5: GPR measurements at Valthe/Odoorn ...................................................... 68 5.6 Location 6: Klazienaveen.............................................................................................. 68 5.7 Geology and glaciology................................................................................................. 69 5.7.1 Location 1: Donderen/Zeijen .................................................................................... 69 5.7.2 Location 2: Gieten..................................................................................................... 69 5.7.3 Location 3: Gasselte .................................................................................................. 70 5.7.4 Location 4: Borger..................................................................................................... 70 5.7.5 Location 6: Klazienaveen........................................................................................... 70 5.8 Summary.......................................................................................................................... 71 6. The role of ‘deeper’ geology in the behaviour of glaciers .................................................74 6.1 Introduction ..................................................................................................................... 74 6.1.1 Implications of forebulging in the Hondsrug area..................................................... 74 4 6.1.2 Surface morphology and deeper geological structures in the Netherlands.............. 78 6.1.5. Thickness of tills, ‘deep’geology and sub-surface temperatures ................................. 84 6.1.6 . Ridges that formed...................................................................................................... 86 6.2. Overview of the IML.......................................................................................................