Quaternary Science Journal GEOzOn SCiEnCE MEDiA Volume 60 / number 2–3 / 2011 / 282–305 / DOi 10.3285/eg.60.2-3.06 iSSn 0424-7116 E&G www.quaternary-science.net Quaternary glaciation history of northern switzerland Frank Preusser, Hans Rudolf Graf, Oskar keller, Edgar krayss, Christian Schlüchter Abstract: A revised glaciation history of the northern foreland of the Swiss Alps is presented by summarising field evidence and chronologi- cal data for different key sites and regions. The oldest Quaternary sediments of Switzerland are multiphase gravels intercalated by till and overbank deposits (‘Deckenschotter’). Important differences in the base level within the gravel deposits allows the distin- guishing of two complex units (‘Höhere Deckenschotter’, ‘Tiefere Deckenschotter’), separated by a period of substantial incision. Mammal remains place the older unit (‘Höhere Deckenschotter’) into zone MN 17 (2.6–1.8 Ma). Each of the complexes contains evidence for at least two, but probably up-to four, individual glaciations. In summary, up-to eight Early Pleistocene glaciations of the Swiss alpine foreland are proposed. The Early Pleistocene ‘Deckenschotter’ are separated from Middle Pleistocene deposition by a time of important erosion, likely related to tectonic movements and/or re-direction of the Alpine Rhine (Middle Pleistocene Reorganisation – MPR). The Middle-Late Pleistocene comprises four or five glaciations, named Möhlin, Habsburg, Hagenholz (uncertain, inadequately documented), Beringen, and Birrfeld after their key regions. The Möhlin Glaciation represents the most extensive glaciation of the Swiss alpine foreland while the Beringen Glaciation had a slightly lesser extent. The last glacial cycle (Birrfeld Glaciation) probably comprises three independent glacial advances dated to ca. 105 ka, 65 ka, and 25 ka. For the last glacial advance, a detailed radiocarbon chronology for ice build-up and meltdown is presented. [Quartäre vergletscherungsgeschichte der nördlichen schweiz] Kurzfassung: Eine revidierte Vergletscherungsgeschichte des nördlichen Vorlandes der Schweizer Alpen wird vorgestellt, basierend auf Feldbe- funden und chronologischen Daten von verschiedenen Schlüssellokalitäten und Regionen. Die ältesten quartären Sedimente der Schweiz sind mehrphasige Kiese, in die Till und Hochflutsedimente eingeschaltet sind (’Deckenschotter’). Bedeutende Unterschiede im Basisniveau der Schotterablagerungen erlauben die Unterscheidung zweier komplex augebauter Einheiten (’Höhere Decken- schotter’, ’Tiefere Deckenschotter’), die durch eine Phase bedeutender Einschneidung getrennt sind. Säugetierreste stellen die äl- tere Einheit (‘Höhere Deckenschotter’) in die Zone MN 17 (2.6–1.8 Ma). Jeder der Komplexe enthält Belege für zumindest zwei, möglicherweise sogar bis zu vier eigenständige Eiszeiten, woraus sich in Summe bis zu acht frühpleistozäne Vergletscherungen des Schweizer Alpenvorlands ergeben. Die frühpleistozänen Deckenschotter sind von mittelpleistozänen Ablagerungen durch eine Zeit bedeutender Erosion getrennt, die wahrscheinlich durch tektonische Bewegungen und/oder eine Umleitung des Alpenrheins verursacht wurde (Mittelpleistozäne Reorganisation – MPR). Das Mittel-/Spätpleistozän beinhaltet vier oder fünf Eiszeiten, die nach ihren Schlüsselregionen als Möhlin-, Habsburg-, Hagenholz- (unsicher, unzureichend belegt), Beringen- und Birrfeld-Eiszeit benannt sind. Die Möhlin-Eiszeit repräsentiert die grösste Vergletscherung des Schweizer Alpenvorlandes, während die Beringen- Eiszeit von nur wenig geringerer Ausdehnung war. Der letzte Glazialzyklus (Birrfeld-Eiszeit) umfasst wahrscheinlich drei eigen- ständige Gletschervorstösse, die auf ca. 105 ka, 65 ka und 25 ka datiert wurden. Für den letzten Eisvorstoss wird eine detaillierte Radiokohlenstoffchronologie für den Eisaufbau und das Abschmelzen präsentiert. Keywords: Alps, glaciation, stratigraphy, chronology, glacial deposits Addresses of authors: F. Preusser *, Institut für Geologie, Universität Bern, Baltzerstrasse 1+3, 3012 Bern, Switzerland. Present address: Department of Physical Geography and Quaternary Geology, Stockholm University, 10691 Stockholm, Sweden. E-Mail: frank.preusser@ natgeo.su.se; H. R. Graf, Dorfstrasse 40, 8014 Gächlingen, Switzerland; O. Keller, Brühlstrasse 90, 9320 Arbon, Switzerland; E. Krayss, Myrtenstrasse 9, 9010 St. Gallen, Switzerland; C. Schlüchter, Institut für Geologie, Universität Bern, Baltzerstrasse 1+3, 3012 Bern, Switzerland. *corresponding author 1 introduction younger three units to glacial series, i.e. terminal moraine ridges and glacial basins. The four glaciations deduced from The Swiss Alps are the area where the theory of past gla- this evidence have been named after small rivers in Bavaria ciations of the lowlands was originally developed by (from old to young: Günz, Mindel, Riss, and Würm), and Perraudin and published by Venetz (1833). The glaciation this stratigraphical scheme has been adopted at least for theory was later further elaborated and promoted by, for some time in many parts of the world. It is important to example, Agassiz (1837) and de Charpentier (1841), but it note that the original Penck & Brückner (1901/09) scheme was again Venetz (1861) who brought up the idea that gla- was later modified and extended by three further glacial ciers may have reached the lowlands several times in the complexes (Donau: Eberl 1930; Biber: Schaefer 1957; past. The tetra-partition of the ice age was later interna- Haslach: Schreiner & Ebel 1981). However, until now tionally established by Penck & Brückner (1901/09) who these stratigraphical units have not been recognised out- observed four different levels of former out-wash plains side southern Germany. in the Iller Valley, Bavaria, each of which is expected to In Switzerland, the four-fold Penck & Brückner represent a discrete glaciation. Proof of the glacial charac- (1901/09) concept was widely accepted for a long time. It ter of the gravel deposits is given by the connection of the has been assumed that the four glaciations found in Bavaria 282 E&G / Vol. 60 / no. 2–3 / 2011 / 282–305 / DOi 10.3285/eg.60.2-3.06 / © authors / Creative Commons attribution license Fig. 1: Overview map of the study in northern Switzerland, with the location of ice domes and ice flow directions (after Florineth 1998; Florineth & Schlüchter 1998; Kelly et al. 2004), and the location of key regions and sites mentioned in the text (G = Greifensee; P = Pfäffikersse; LG = Maximum extent of the Last Glaciation; MEG = Extent of the Most Extensive Glaciation). Abb. 1: Übersichtskarte des Untersuchungsgebietes in der Nordschweiz mit der Lage von Eisdomen und Eisflussrichtungen (nach Florineth 1998; Flori- neth & Schlüchter 1998; Kelly et al. 2004), sowie der Lage von Schlüsselregionen und Örtlichkeiten, die im Text vermerkt sind (G = Greifensee; P = Pfäffikersse; LG = Maximale Ausdehnung der letzten Vergletscherung; MEG = Ausdehnung der Grössten Vergletscherung). are represented by the morphological features of Low Ter- Penck & Brückner (1901/09) are not yet reliably estab- race (Würm), High Terrace (Riss), ‘Tiefere Deckenschotter’ lished, this article will desist from using nomenclature es- (Mindel), and ‘Höhere Deckenschotter’ (Günz). An alterna- tablished for Bavaria. Detailed reviews of the Late Quater- tive view of the glaciation history of the Swiss lowlands nary environmental history of the region and glacial dy- was introduced by Schlüchter (1988), who combined geo- namics are not given here, as these have already been pro- morphological observations with detailed logging of sec- vided by Preusser (2004) and Ivy-Ochs et al. (2008, 2009). tions and establishing lithostratigraphical models. Accord- ing to this scheme, glaciers reached the lowlands of Swit- 2 Geological, topographic and palaeo-glaciological zerland at least 15 times during the Quaternary, which is setting much more often than previously assumed. This contribution aims at providing a comprehensive The area considered here comprises the northern foreland overview of the present knowledge of the Quaternary his- of the Swiss Alps from the eastern edge of Lake Neuchâtel tory of the northern foreland of the Swiss Alps, based on in the west to the western banks of Lake Constance in the evidence for different key areas and sites (locations are east (Fig. 1). The Alps that form the southern border of the given in Fig. 1). The oldest Quaternary deposits are the study area consist mainly of limestone and other sediments so-called ‘Deckenschotter’ of northern Switzerland, which in their outer parts, and a variety of different magmatic and probably comprise the largest part of the Early Pleistocene metamorphic rocks in their inner parts. The petrography of development. The new terminology introduced by Graf pebbles and boulders found in glacial deposits in the fore- (2009a) comprises five Middle to Late Pleistocene glacia- land has been used to reconstruct past ice flow patterns. To tions (from old to young): Möhlin, Habsburg, Hagenholz, the north, the region of interest is bounded by the chain of Beringen, and Birrfeld. Evidences for this new stratigraphi- the Jura Mountains, with peaks reaching altitudes of up to cal scheme will be summarised and are mainly based on 1700 m a.s.l. and consisting mainly of limestone. The Jura previous studies by Graf (2009a) and Keller & Krayss mountain range has acted as a barrier with a major impact (2010). As correlations with the stratigraphic scheme of on ice flow in the western part of the region. To the