Plio-Pleistocene folding in the southern Rhinegraben recorded by the evolution of the drainage network (Sundgau area; northwestern Switzerland and France)

Abstract

The southern Rhinegraben represents a key area to unravel the Neogene paleohydrographic history of the northern Alpine foreland. At least, three successive main drainage systems are documented by the youngest sediments of the graben fill. They are respectively pre-, syn-and post-dating the folding of the Jura Mountains (about 10-5 Ma ago).Pliocene to recent uplift and shortening of the Pliocene fluvial gravel ("Sundgauschotter"), which accumulated on a nearly plain surface, and the progressive deflection and capture of rivers resulted from reactivation of preexisting Paleogene faults. The alluvial terraces along the major rivers of the Sundgau area show upward warping near the uplift areas. Furthermore, river beds responded to uplift by lateral shift.During the Pliocene-Pleistocene, fluvial drainage diverted stepwise from the initial, westwards directed course (towards the Bressegraben) to the N (into the Rhinegraben): Firstly, uplift in the south at the boundary between the Rhinegraben and the Jura Mountains induced a northwards directed migration of the middle Pliocene, E-W flowing paleo-drainage system. Successively, a late Pliocene/early Pleistocene lowering of the base level in the Rhinegraben north of Mulhouse resulted in the capture by southwards directed backward erosion of this system into the Rhinegraben, as likewise documented by the reconstitution of the paleo-drainage patterns in the Sundgau area. In addition, a gradually capture moving from NE to SW has been identified for the Sundgau catchment area. ZUSAMMENFASSUNGDie Morphogenese des südlichen Rheingrabens hängt stark mit der hydrographischen Entwicklung des zentralen Alpinen Vorlandes zusammen. In den jüngsten Ablagerungen der Grabenfüllung sind nämlich mindestens drei Hauptentwässerungssysteme dokumentiert. Die fluviatilen Sedimente vom mittleren Miozän bis zum Quartär wurden vor, während und nach der Hauptphase der Jurafaltung abgelagert (ca. 10-5 Ma).Eine Reaktivierung von paläogenen Brüchen während des Plio-Pleistozäns ist sowohl durch die Auffaltung der pliozänen Sundgauschotter als auch durch die fortschreitende Ablenkung und Anzapfung von Flüssen im süd-lichen Elsass (Sundgau) belegt. Alluviale Terrassen entlang der Hauptflüsse im Sundgau wurden in der Nähe von Antiklinalen gehoben und verstellt. Das weist darauf hin, dass die tektonische Aktivität zumindest bis in das Pleistozän anhielt.Die Rekonstruktion des Paläoentwässerungssystems zeigt, dass die Umlenkung des gesamten Flussnetzes im Sundgau, das während des Pliozäns nach Westen in den Bressegraben gerichtet war und sich dann nach Norden in den Rheingraben reorientierte, schrittweise stattfand: Infolge von Hebungen im Süden entlang der Rheingraben/Jura-Grenze migrierte der mittelpliozäne Hauptfluss nordwärts und die Absenkung im Rheingraben nördlich von Mulhouse während des Spätpliozäns und des Pleistozäns führte dann zur allmäh-lichen Anzapfung des Entwässerungssystems von Norden. fluenced the evolution of the adjoining Jura Mountains, when these were folded and thrusted since the Mi...

Latest Pliocene to recent thick-skinned tectonics at the Upper Rhine Graben – Jura Mountains junction

“…Vertical uplift rates may also be estimated along the Florimont and Réchésy anticlines, where the fold amplitude is in the order of 150 m. Within the given time frame, this yields a minimum uplift rate that is also in the order of 0.05 mm/a. This estimate is in agreement with uplift rates that were deduced from the amount of uplift of Pleistocene alluvial terraces along the Largue, Ill and Thalbach Rhine tributaries, where they traverse anticline crests traceable in the Sundgau gravels (Giamboni et al 2004b). …”

“…The eastern end of the Sundgau gravel sheet W of Basel is clearly erosional. Previous authors attributed the southward shift of the water divide either to a slow-down (or end) of upwarping of the Vosges-Black Forest arch , or alternatively, to accelerated subsidence in the northern URG and a concomitant drop of the local base level, causing subsequent regressive erosion in the southern URG (Doebl 1970;Schumacher 2002;Giamboni et al 2004b). Our own data (Ustaszewski & Schmid 2006 and this work) hint towards a third possible explanation, namely that both abandonment of the Sundgau riverbed and subsequent reorganisation of the drainage system were triggered by shortening-induced neotectonic uplift.…”

Feedback between erosion and active deformation: geomorphic constraints from the frontal Jura fold-and-thrust belt (eastern France)

“…The gravels rest with an erosional unconformity on Mesozoic and/or Tertiary strata (Liniger 1967). In the Sundgau area the SFC gravel sheet reaches a thickness of 30 m (Giamboni et al 2004b), while in the Forêt de Chaux thicknesses of up to 65 m are reported (Chauve et al 1979). Sedimentological features of the SFC Gravels imply that they were deposited by a low-gradient braided river system characterised by low sinuosity shifting channels (Giamboni et al 2004b).…”

“…The fault-related folds along the Chailluz Thrust, the Avant-Monts Fault and along the Lomont, Bisontin and Quingey Faisceaux form distinct ridges. The modern drainage pattern of the region is roughly parallel to the ENE-WSW striking structural trend and has undergone a complex Neogene evolution that was controlled by tectonic and climatic events (Liniger 1966;Petit et al 1996;Giamboni et al 2004b;Berger et al 2005;Ziegler and Fraefel 2009). …”

“…Despite this, there are indications for recent deformation within the area provided by pioneering studies in tectonic geomorphology (Dreyfuss and Glangeaud 1950;Liniger 1967;Théobald et al 1977;Campy 1984). More recent studies applying modern techniques based on digital elevation models are so far restricted to areas in the southern and northern parts of the Upper Rhine Graben area (Nivière and Marquis 2000;Giamboni et al 2004b;Peters and van Balen 2007), but are still lacking in the Rhine-Bresse Transfer Zone proper. This study aims at a better understanding of the Pliocene to recent tectonic evolution of this region by investigating two different geomorphic markers.…”