Geomorphology 122 2010 244 253 Contents lists available at ScienceDirect Geomorphology j o u r n a l h o m e p a g e w w w e l s ev i e r c o m l o c a t e g e o m o r p h Quantifying erosion over timescales of one million years A photogrammetric approach on the amount of Rhenish erosion in southwestern Germany Annette Strasser Marcel Strasser Hartmut Seyfried Institut f r Planetologie Universit t Stuttgart Herdweg 51 70174 Stuttgart Germany a r t i c l e i n f o Article history Received 6 May 2008 Received in revised form 19 December 2008 Accepted 16 June 2009 Available online 17 July 2009 Keywords Erosion rate DEM Southwestern Germany Rhine Danube Pleistocene a b s t r a c t The Lein valley in southwestern Germany possesses well preserved Pliocene to mid Pleistocene land surfaces featuring a gentle relief and sediments accumulated by former tributaries of the Danube This ancient Danubian land surface was captured and incised by mid Pleistocene to Holocene tributaries of the River Rhine In a photogrammetric approach we calculated the volume of material extracted by Rhenish erosion providing a rst quanti cation of the effects of stream piracy on timescales of about 1 Ma Using stereoscopic surface modelling software a DEM was generated with a resolution of 5 m From borehole data literature geological maps and own eld observations we determined the morphometric parameters of the ancient Danubian Ur Lein valley The gradient was imported as a 3D breakline into the model where it controls the reinterpolation of surrounding data points The result is a high resolution DEM of the valley of the Ur Lein Subtraction of the DEM of the actual landscape from the DEM of the ancient Ur Lein valley yields a model representing the rock volume eroded by the Rhenish Lein which totals 1 39 km3 and converts into a rate of erosion between 63 and 74 mm ka over a period of 700 to 600 ka respectively in accordance with gures obtained elsewhere in Central Europe through cosmogenic nuclides It re ects the dominance of frequent uctuations in climate and is considered to be mainly a product of strong changes in temperature and related processes during the transitional times between mid to late Pleistocene warm and cold states A ltering procedure applied to cold and transitional state erosion rates of the Middle and Late Pleistocene yielded peak values between 66 and 77 mm ka up to three times higher than the modern rate or the rate of warm state episodes An assessment of the contribution of Rhenish stream piracy on long term mid Pleistocene denudation under changing climate conditions resulted in a maximum 4 9 fold acceleration 2009 Elsevier B V All rights reserved 1 Introduction The present day inventory of landforms in southwestern Germany is mainly a product of two strongly discontinuous processes a late Alpine tilting of the foreland crust and subsequent post collisional isostatic uplift Strasser et al 2009 and b Neogene climate change Two large rivers competed for the extraction of material the east owing Danube and the north owing Rhine Fig 1 Wagner 1952 1953 1963 Following an episode of prolonged isostatic uplift the Danube came into existence only during the latest Miocene conquering large parts of an ancient network initially draining into the Early Miocene Sea of the Upper Marine Molasse Fig 2A or into the continental basin of the Mid to Late Miocene Upper Freshwater Molasse Fig 2B Villinger 1986 Schall 2002 Strasser et al 2009 The Rhine considerably pre dates the Danube occupying the Rhine Graben since early Miocene times 20 Ma Simon 2008 although only in the Late Miocene did it start to capture large areas of southwestern Germany Fig 2B to D Simon 1987 1988 Corresponding author Tel 49 711 68581323 fax 49 711 68581341 E mail address annette strasser geologie uni stuttgart de A Strasser 0169 555X see front matter 2009 Elsevier B V All rights reserved doi 10 1016 j geomorph 2009 06 027 Hagdorn and Simon 1988 Schall 2002 Rhenish incision strongly followed the blueprint of original Danubian valley directions and nodes of bifurcation Dongus 1977 2000 Flow reversal resulted in the formation of numerous valley drainage divides moving downstream in the Danubian sense of ow as Rhenish incision advanced Escarpments became deeply penetrated along these pre existing valleys and scarplands were ef ciently attacked through headwater erosion by groundwater sapping working mainly on the backsides of escarpments Fig 2 In most places the transition from ancient to young landforms is a sharp break Wagner 1953 Dongus 1977 2000 Strasser et al 2008 The anks of larger Rhenish valleys are often modi ed by periglacial processes and landslides The present watershed between Rhine and Danube is situated near the edge of a large escarpment of Upper Jurassic carbonate rocks corresponding to an intensively karsti cated scarpland Schw bische Alb Figs 1 3 Outside the modern Danubian catchment area remnants of Danubian surfaces are common but especially extensive and wellpreserved in our study area Figs 1 and 2 Dongus 1977 2000 The gentle relief of these surfaces is carved into a scarpland of Late Triassic Keuper sandstones and Early Liassic carbonates sandstones and claystones Fig 3 During nal slow down of Danubian erosion and A Strasser et al Geomorphology 122 2010 244 253 245 Kocher is a valley drainage divide presently situated at 507 m a s l Fig 4 Stream capture has also been effective among Rhenish tributaries resulting in hierarchically less important valley drainage divides such as the one separating the Rems and Kocher north of Essingent 470 m a s l and another separating the Lein and Wieslauf near Breitenf rst 493 m a s l Fig 4 The smooth hills of the Frickenhofer H he Figs 3 and 4 are an extraordinarily well preserved remnant of ancient Danubian erosional landforms most probably created during the early Pliocene Dongus 1977 2000 Remnants of the early and mid Pleistocene Goldsh fer Sande Fraas 1871 are still widely preserved Figs 3 and 4 Their occurrence close to the large escarpment of Upper Jurassic carbonate rocks forming the morphological backbone of the Schw bische Alb strongly suggests that this escarpment had not undergone substantial changes since their time of formation From Late Miocene until early Middle Pleistocene times the Danubian predecessors of today s Rhenish tributaries the Kocher Lein Jagst and Rems drained southward by passing the escarpment of Upper Jurassic carbonate rocks of the Schw bische Alb