Paraglacial Sediment Storage Quantification in the Turtmann Valley, Swiss Alps
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Paraglacial sediment storage quantification in the Turtmann Valley, Swiss Alps Dissertation zur Erlangung des Doktorgrades (Dr. rer. nat.) der Mathematisch-Naturwissenschaftlichen Fakultät der Rheinischen Friedrich-Wilhelms-Universität Bonn vorgelegt von Jan-Christoph Otto aus Lemgo Bonn 2006 Angefertigt mit Genehmigung der Mathematisch-Naturwissenschaftlichen Fakultät der Rheinischen Friedrich-Wilhelms-Universität Bonn 1. Referent: Prof. Dr. Richard Dikau 2. Referent: Prof. Dr. Lothar Schrott Tag der Promotion: 20.11.06 Diese Dissertation ist auf dem Hochschulschriftenserver der ULB Bonn http://hss.ulb.uni-bonn.de/diss_online elektronisch publiziert. CONTENTS CONTENTS I LIST OF FIGURES III LIST OF TABLES VII 1 PROBLEM STATEMENT AND MAIN OBJECTIVES 1 2 SCIENTIFIC FRAMEWORK 3 2.1 MOUNTAIN ENVIRONMENTS AS GEOMORPHOLOGICAL SYSTEMS 3 2.1.1 Time and space in mountain geosystems 8 2.2 THE SEDIMENT BUDGET APPROACH 11 2.2.1 Denudation rates and sediment yield 16 2.2.2 Sediment budget and storage quantification 17 2.3 EVOLUTION OF MOUNTAIN LANDSCAPE SYSTEMS 21 2.3.1 Uplift and erosion of mountains 21 2.3.2 The paraglacial sedimentation cycle 23 2.4 SEDIMENT STORAGE LANDFORMS 30 2.4.1 Talus slopes and talus cones 30 2.4.2 Block slopes 33 2.4.3 Rockglaciers 34 2.4.4 Moraines 36 2.4.5 Rock fall deposits 37 2.4.6 Alluvial deposits 38 3 METHODS FOR SEDIMENT STORAGE ANALYSIS 40 3.1 GEOMORPHOLOGICAL SYSTEM AND LAND SURFACE PATTERN ANALYSIS 40 3.2 LANDFORM CLASSIFICATION 42 3.2.1 Derivation of primary attributes 42 3.2.2 Derivation of secondary attributes 43 3.3 TOPOGRAPHICAL , DIGITAL IMAGERY AND GEOMORPHOLOGICAL BASE DATA 45 3.4 METHODS FOR SEDIMENT STORAGE QUANTIFICATION 46 3.4.1 Shallow subsurface geophysical investigations 46 3.4.1.1 Seismic refraction (SR) 47 3.4.1.2 2D- electrical resistivity tomography (ERT) 52 3.4.1.3 Ground penetrating radar (GPR) 54 3.4.1.4 Acquisition of geophysical data 56 3.4.2 Volume quantification using DTM analysis 59 3.4.2.1 Sediment thickness interpolation in the Hungerlitaelli 59 3.4.2.2 Volume quantification of the Turtmann Valley 61 3.4.3 Calculation of denudation rates and mass transfer 67 3.4.4 Uncertainties and error estimation of bedrock detection and volume estimation 68 I 3.4.4.1 Uncertainties of bedrock detection using geophysical methods 68 3.4.4.2 Error estimation in volume calculation 69 4 STUDY AREA 72 4.1 GEOMORPHOLOGY 73 4.2 GEOLOGY 75 4.3 CLIMATE 75 4.4 GLACIAL HISTORY AND PALEOCLIMATE 78 4.5 PREVIOUS WORK IN THE TURTMANN VALLEY 81 5 RESULTS 82 5.1 CHARACTERISTICS AND SPATIAL DISTRIBUTION OF SEDIMENT STORAGE LANDFORMS 82 5.1.1 Landform distribution within hanging valleys 88 5.2 GEOPHYSICAL SURVEYS 91 5.2.1 Detection of the regolith-bedrock boundary with seismic refraction surveying (SR) 91 5.2.2 Detection of the regolith-bedrock boundary using Electric Resistivity Tomography (2D-ER) 97 5.2.3 Detection of the regolith-bedrock boundary with ground penetrating radar (GPR) 101 5.3 SEDIMENT VOLUME QUANTIFICATION 105 5.3.1 Sediment volume of the Hungerlitaelli 105 5.3.2 Sediment volume of the Turtmann Valley 111 5.3.2.1 Subsystem hanging valleys 111 5.3.2.2 Subsystem main valley floor 114 5.3.2.3 Subsystem glacier forefield 116 5.3.2.4 Subsystem trough slopes and remaining areas 119 5.3.2.5 Total Sediment volume of the Turtmann Valley 120 5.4 MASS TRANSFER AND DENUDATION RATES 121 6 DISCUSSION 128 6.1 PARAGLACIAL LANDFORM EVOLUTION OF THE TURTMANN VALLEY 128 6.2 SEDIMENT STORAGE IN THE SEDIMENT FLUX SYSTEM OF THE TURTMANN VALLEY 132 6.2.1 Storage volumes and mass transfer 133 6.2.2 Denudation rates 135 7 CONCLUSION 138 8 SUMMARY 141 9 REFERENCES 144 10 APPENDIX A A. SEISMIC REFRACTION MODELLING RESULTS A B. 2D-RESISTIVITY INVERSION RESULTS P C. GROUND PENETRATING RADAR IMAGES V II LIST OF FIGURES Figure 2.1 Caine’s alpine sediment cascade model (Caine 1974) 5 Figure 2.2 Meso scale sediment flux model of the Turtmann Valley (Otto and Dikau 2004) 6 Figure 2.3 Mountain Zones by Fookes et al. (1985). Zone: 1 – High altitude glacial and periglacial, 2 – Free rock faces and associated slopes, 3 – Degraded middle slopes and ancient valleys floors, 4 – Active lower slopes, and 5 – Valley floors. 8 Figure 2.4 Time and space scales in geomorphology (Brunsden 1996) 9 Figure 2.5 Qualitative sediment flux model of the Brändjitaelli hanging valley (Otto and Dikau 2004) 15 Figure 2.6 Cross profile through the Rhone Valley derived from seismic reflection surveying at Turtmann (Finckh and Frei 1990) 20 Figure 2.7 The paraglacial model by Church and Ryder (1978) 24 Figure 2.8 The paraglacial exhaustion model (Ballantyne 2002). Rate of sediment release ( λ) is related to λ = − the proportion of sediment ‘available’ ( St) at time ( t) since deglaciation as ln( S t /) t . 25 Figure 2.9 The paraglacial sedimentation cycle modified by Church and Slaymaker (1989). The time scale spans approximately 10 ka. 26 Figure 2.10 Changing volume of sediment storage (Ballantyne 2003) 28 Figure 2.11 Episodic impacts on the sediment input within the paraglacial cycle of the Lillooet River, Canada (Jordan and Slaymaker 1991) 28 Figure 2.12 Model of paraglacial sediment yield for catchments of different size (Harbour and Warburton 1993) 29 Figure 2.13 Coalescing talus slopes at the entry to the Bortertaelli. 31 Figure 2.14 Different talus slope types (Ballantyne and Harris 1994). 32 Figure 2.15 A block slope exposed to the south in the Hungerlitaelli. 34 Figure 2.16 Active rock glacier in the Hungerlitaelli. 35 Figure 2.17 Lateral moraine deposits in the Pipjitaelli 37 Figure 2.18 Rock fall deposit in the Niggelingtaelli 38 Figure 2.19 Alluvial deposit have almost filled up a small lake the Niggelingtaelli 39 Figure 3.1 Toposequence for arctic-alpine environments, Greenland (from Huggett and Cheesmann 2002, originally by Stäblein 1984) 44 Figure 3.2 A – Principle of seismic wave refraction and reflection. B – Travel-time–distance plot ( ic – angle of incidence, V1 – velocity layer 1, V2 – velocity layer 2, ti – intercept time, Xcross – crossover point). 51 Figure 3.3 Configuration of the Wenner Array: A current is passed from electrode A to B. By measuring the potential between electrodes M and N the apparent resistivity ρ in layers 1 and 2 is determined. The distance a between the electrodes always remains constant, while the configuration is shifted along the spread. 53 Figure 3.4 Principle of GPR measurement. T – Transmitter of radar waves; R – Receiver; a – Offset between T and R. 55 Figure 3.5 Procedure steps of seismic refraction data analysis 57 Figure 3.6 Locations of geophysically derived (yellow) and modelled (blue) thickness locations used for the sediment thickness interpolation in the Hungerlitaelli. 60 III Figure 3.7 Principle of the SLBL method indicating intermediate steps of the procedure. At each step a point is replaced by the mean of its two neighbours minus the tolerance ∆∆∆z. ( from Jaboeydoff and Derron 2005) 64 Figure 3.8 The glacier forefield of the Turtmann Valley. 66 Figure 4.1 Location of the Turtmann Valley, Swiss Alps 72 Figure 4.2 The southern end of the Turtmann Valley terminated by the Turtmann glacier to the right and Brunegg glacier to the left. The peaks in the left background are Bishorn (4135 m) and Weisshorn (4504 m) 74 Figure 4.3 View from the Hungerlitaelli across the main trough into some western hanging valleys. The peak towards the left is Les Diablons (3609 m). 74 Figure 4.4 Geological cross section through the penninic nappes around the Turtmann Valley. The nappes are: 1–Houillère-Pontis, 2–Siviez-Mischabel, 3–Mont Fort, 4–Monte Rosa, 5–Zermatt-Sass Fee, 6– Tsaté, 7–Dent Blanche (from Laphart 2001) 75 Figure 4.5 Mean annual air temperature and monthly precipitation figure from the climate station in the Hungerlitaelli (Altitude 2770 m). 77 Figure 4.6 Younger Dryas extent in the Valais, Switzerland. (modified after Burri 1990, from: Schweizerische Gesellschaft für Ur- und Frühgeschichte 1993) 80 Figure 5.1 Land surface classification of the hanging valleys 83 Figure 5.2 A - Altitudinal distribution of classified storage land surface. B – Hypsometric curve of the hanging valley area. 84 Figure 5.3 Directional frequency distribution of mean aspect values for sediment storage landforms. (Colours correspond to Figure 5.2) 86 Figure 5.4 Different toposequences found in the Grüobtaelli. The roman numbers indicate the toposequence type (cf. Table 5.4) 88 Figure 5.5 Relative landform storage type area (%) per hanging valley. 90 Figure 5.6 Location of seismic profiles (SR) and sediment storage landforms in the Hungerlitaelli. (For a description of landform colours please refer to Figure 5.1). 92 Figure 5.7 Sounding SR04_2: Model of refractor locations and velocity distribution (A), travel-times (B) and cross-section of refractor layers (C). The seismic modelling includes the location of the refractor surfaces calculated with the network raytracing method and of the velocity distribution derived from the tomography modelling. The numbers give the velocities (in m s -1) of the modelled layers using the network raytracing method. Diagram B shows the observed (black lines) and modelled (coloured lines) travel-times of this sounding. The colour scale on the right refers to the modelled velocity distribution derived from the tomography modelling. The lower diagram (C) depicts a cross-section through the talus slope indicating the location of the two observed refractor surfaces. 96 Figure 5.8 Location of the electric resistivity profile (2D-ER) and sediment storage landforms in the Hungerlitaelli.