Drilling Overdeepened Alpine Valleys (ICDP-DOVE): quantifying the age, extent, and environmental impact of Alpine glaciations

Abstract

Abstract. The sedimentary infill of glacially overdeepened valleys (i.e., structures eroded below the fluvial base level) is an excellent but yet underexplored archive with regard to the age, extent, and nature of past glaciations. The ICDP project DOVE (Drilling Overdeepened Alpine Valleys) Phase 1 investigates a series of drill cores from glacially overdeepened troughs at several locations along the northern front of the Alps. All sites will be investigated with regard to several aspects of environmental dynamics during the Quaternary, with focus on the glaciation, vegetation, and landscape history. Geophysical methods (e.g., seismic surveys), for example, will explore the geometry of overdeepened structures to better understand the process of overdeepening. Sedimentological analyses combined with downhole logging, analysis of biological remains, and state-of-the-art geochronological methods, will enable us to reconstruct the erosion and sedimentation history of the overdeepened troughs. This approach is expected to yield significant novel data quantifying the extent and timing of Middle and Late Pleistocene glaciations of the Alps. In a first phase, two sites were drilled in late 2021 into filled overdeepenings below the paleolobe of the Rhine Glacier, and both recovered a trough filling composed of multiphase glacial sequences. Fully cored Hole 5068_1_C reached a depth of 165 m and recovered 10 m molasse bedrock at the base. This hole will be used together with two flush holes (5068_1_A, 5068_1_B) for further geophysical cross-well experiments. Site 5068_2 reached a depth of 255 m and bottomed out near the soft rock–bedrock contact. These two sites are complemented by three legacy drill sites that previously recovered filled overdeepenings below the more eastern Alpine Isar-Loisach, Salzach, and Traun paleoglacier lobes (5068_3, 5068_4, 5068_5). All analysis and interpretations of this DOVE Phase 1 will eventually lay the ground for an upcoming Phase 2 that will complete the pan-Alpine approach. This follow-up phase will investigate overdeepenings formerly occupied by paleoglacier lobes from the western and southern Alpine margins through drilling sites in France, Italy, and Slovenia. Available geological information and infrastructure make the Alps an ideal area to study overdeepened structures; however, the expected results of this study will not be restricted to the Alps. Such features are also known from other formerly glaciated mountain ranges, which are less studied than the Alps and more problematic with regards to drilling logistics. The results of this study will serve as textbook concepts to understand a full range of geological processes relevant to formerly glaciated areas all over our planet.

Comparison of overdeepened structures in formerly glaciated areas of the northern Alpine foreland and northern central Europe

“…by process-oriented investigations of the basal "tills"). This is the central objective of the current International Scientific Continental Drilling Program project Drilling Overdeepened Alpine Valleys (DOVE; Anselmetti et al, 2022). Similar drilling projects targeting tunnel valleys are in dire need in order to better understand the overdeepening erosion and glaciation history of northern central Europe.…”

“…In the Lake Constance area, Ellwanger et al (2011) distinguish three major generations of overdeepenings, with the drilling in the Tannwald basin being the best documented for the time being (LGRB, 2015;Burschil et al, 2018;Anselmetti et al, 2022). This basin belongs to the oldest generation recognised so far.…”

Drilling into a deep buried valley (ICDP DOVE): a 252 m long sediment succession from a glacial overdeepening in northwestern Switzerland

“…In the frame of the International Continental Scientific Drilling Program (ICDP) project Drilling Overdeepened Alpine Valleys (DOVE), the sedimentary infill of several overdeepened troughs are targeted with the overarching goal of quantifying the proposed asymmetry in the extent and timing of the Alpine glaciations in the pan-Alpine area and their implications for the paleoclimate, paleolandscape, and paleoenvironmental evolution back to the Middle Pleistocene. A detailed overview of the DOVE project is provided in Anselmetti et al (2022). The project seeks to achieve these goals by combining the following: (i) a series of new drill cores, (ii) analyzing existing drill cores, and (iii) geophysical surveys across overdeepened troughs.…”

Poor Man's Line Scan – a simple tool for the acquisition of high-resolution, undistorted drill core photos

“…The photos presented in the following were taken from selected cores of the International Continental Scientific Drilling Program (ICDP) borehole 5068_1_C in Tannwald, southern Germany (Anselmetti et al, 2022). Line scan photos were recorded with a Geotek Core Imaging System (Geotek Limited, 2017) in the laboratory of the University of Bern.…”