TY  - GEN
A1  - Tofelde, Stefanie
A1  - Bufe, Aaron
A1  - Turowski, Jens M.
T1  - Hillslope Sediment Supply Limits Alluvial Valley Width
T2  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - River-valley morphology preserves information on tectonic and climatic conditions that shape landscapes. Observations suggest that river discharge and valley-wall lithology are the main controls on valley width. Yet, current models based on these observations fail to explain the full range of cross-sectional valley shapes in nature, suggesting hitherto unquantified controls on valley width. In particular, current models cannot explain the existence of paired terrace sequences that form under cyclic climate forcing. Paired river terraces are staircases of abandoned floodplains on both valley sides, and hence preserve past valley widths. Their formation requires alternating phases of predominantly river incision and predominantly lateral planation, plus progressive valley narrowing. While cyclic Quaternary climate changes can explain shifts between incision and lateral erosion, the driving mechanism of valley narrowing is unknown. Here, we extract valley geometries from climatically formed, alluvial river-terrace sequences and show that across our dataset, the total cumulative terrace height (here: total valley height) explains 90%–99% of the variance in valley width at the terrace sites. This finding suggests that valley height, or a parameter that scales linearly with valley height, controls valley width in addition to river discharge and lithology. To explain this valley-width-height relationship, we reformulate existing valley-width models and suggest that, when adjusting to new boundary conditions, alluvial valleys evolve to a width at which sediment removal from valley walls matches lateral sediment supply from hillslope erosion. Such a hillslope-channel coupling is not captured in current valley-evolution models. Our model can explain the existence of paired terrace sequences under cyclic climate forcing and relates valley width to measurable field parameters. Therefore, it facilitates the reconstruction of past climatic and tectonic conditions from valley topography.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1289 
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-572879
SN  - 1866-8372
IS  - 1289
ER  - 
TY  - JOUR
A1  - Tofelde, Stefanie
A1  - Bufe, Aaron
A1  - Turowski, Jens M.
T1  - Hillslope Sediment Supply Limits Alluvial Valley Width
JF  - AGU Advances
N2  - River-valley morphology preserves information on tectonic and climatic conditions that shape landscapes. Observations suggest that river discharge and valley-wall lithology are the main controls on valley width. Yet, current models based on these observations fail to explain the full range of cross-sectional valley shapes in nature, suggesting hitherto unquantified controls on valley width. In particular, current models cannot explain the existence of paired terrace sequences that form under cyclic climate forcing. Paired river terraces are staircases of abandoned floodplains on both valley sides, and hence preserve past valley widths. Their formation requires alternating phases of predominantly river incision and predominantly lateral planation, plus progressive valley narrowing. While cyclic Quaternary climate changes can explain shifts between incision and lateral erosion, the driving mechanism of valley narrowing is unknown. Here, we extract valley geometries from climatically formed, alluvial river-terrace sequences and show that across our dataset, the total cumulative terrace height (here: total valley height) explains 90%–99% of the variance in valley width at the terrace sites. This finding suggests that valley height, or a parameter that scales linearly with valley height, controls valley width in addition to river discharge and lithology. To explain this valley-width-height relationship, we reformulate existing valley-width models and suggest that, when adjusting to new boundary conditions, alluvial valleys evolve to a width at which sediment removal from valley walls matches lateral sediment supply from hillslope erosion. Such a hillslope-channel coupling is not captured in current valley-evolution models. Our model can explain the existence of paired terrace sequences under cyclic climate forcing and relates valley width to measurable field parameters. Therefore, it facilitates the reconstruction of past climatic and tectonic conditions from valley topography.
Y1  - 2022
U6  - https://doi.org/10.1029/2021AV000641
SN  - 2576-604X
PB  - American Geophysical Union (AGU); Wiley
CY  - Hoboken, New Jersey, USA
ER  - 
TY  - GEN
A1  - Tofelde, Stefanie
A1  - Bernhardt, Anne
A1  - Guerit, Laure
A1  - Romans, Brian W.
T1  - Times Associated With Source-to-Sink Propagation of Environmental Signals During Landscape Transience
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Sediment archives in the terrestrial and marine realm are regularly analyzed to infer changes in climate, tectonic, or anthropogenic boundary conditions of the past. However, contradictory observations have been made regarding whether short period events are faithfully preserved in stratigraphic archives; for instance, in marine sediments offshore large river systems. On the one hand, short period events are hypothesized to be non-detectable in the signature of terrestrially derived sediments due to buffering during sediment transport along large river systems. On the other hand, several studies have detected signals of short period events in marine records offshore large river systems. We propose that this apparent discrepancy is related to the lack of a differentiation between different types of signals and the lack of distinction between river response times and signal propagation times. In this review, we (1) expand the definition of the term ‘signal’ and group signals in sub-categories related to hydraulic grain size characteristics, (2) clarify the different types of ‘times’ and suggest a precise and consistent terminology for future use, and (3) compile and discuss factors influencing the times of signal transfer along sediment routing systems and how those times vary with hydraulic grain size characteristics. Unraveling different types of signals and distinctive time periods related to signal propagation addresses the discrepancies mentioned above and allows a more comprehensive exploration of event preservation in stratigraphy – a prerequisite for reliable environmental reconstructions from terrestrially derived sedimentary records.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1230 
KW  - signal propagation
KW  - landscape transience
KW  - source-to-sink
KW  - stratigraphy
KW  - response time
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-544431
SN  - 1866-8372
SP  - 1
EP  - 26
PB  - Universitätsverlag Potsdam
CY  - Potsdam
ER  - 
TY  - JOUR
A1  - Tofelde, Stefanie
A1  - Bernhardt, Anne
A1  - Guerit, Laure
A1  - Romans, Brian W.
T1  - Times Associated With Source-to-Sink Propagation of Environmental Signals During Landscape Transience
JF  - Frontiers in Earth Science
N2  - Sediment archives in the terrestrial and marine realm are regularly analyzed to infer changes in climate, tectonic, or anthropogenic boundary conditions of the past. However, contradictory observations have been made regarding whether short period events are faithfully preserved in stratigraphic archives; for instance, in marine sediments offshore large river systems. On the one hand, short period events are hypothesized to be non-detectable in the signature of terrestrially derived sediments due to buffering during sediment transport along large river systems. On the other hand, several studies have detected signals of short period events in marine records offshore large river systems. We propose that this apparent discrepancy is related to the lack of a differentiation between different types of signals and the lack of distinction between river response times and signal propagation times. In this review, we (1) expand the definition of the term ‘signal’ and group signals in sub-categories related to hydraulic grain size characteristics, (2) clarify the different types of ‘times’ and suggest a precise and consistent terminology for future use, and (3) compile and discuss factors influencing the times of signal transfer along sediment routing systems and how those times vary with hydraulic grain size characteristics. Unraveling different types of signals and distinctive time periods related to signal propagation addresses the discrepancies mentioned above and allows a more comprehensive exploration of event preservation in stratigraphy – a prerequisite for reliable environmental reconstructions from terrestrially derived sedimentary records.
KW  - signal propagation
KW  - landscape transience
KW  - source-to-sink
KW  - stratigraphy
KW  - response time
Y1  - 2021
U6  - https://doi.org/10.3389/feart.2021.628315
SN  - 2296-6463
VL  - 9
SP  - 1
EP  - 26
PB  - Frontiers Media
CY  - Lausanne, Schweiz
ER  - 
TY  - JOUR
A1  - Tofelde, Stefanie
A1  - Duesing, Walter
A1  - Schildgen, Taylor F.
A1  - Wickert, Andrew D.
A1  - Wittmann, Hella
A1  - Alonso, Ricardo N.
A1  - Strecker, Manfred
T1  - Effects of deep-seated versus shallow hillslope processes on cosmogenic Be-10 concentrations in fluvial sand and gravel
JF  - Earth surface processes and landforms : the journal of the British Geomorphological Research Group
N2  - Terrestrial cosmogenic nuclide (TCN) concentrations in fluvial sediment, from which denudation rates are commonly inferred, can be affected by hillslope processes. TCN concentrations in gravel and sand may differ if localized, deep-excavation processes (e.g. landslides, debris flows) affect the contributing catchment, whereas the TCN concentrations of sand and gravel tend to be more similar when diffusional processes like soil creep and sheetwash are dominant. To date, however, no study has systematically compared TCN concentrations in different detrital grain-size fractions with a detailed inventory of hillslope processes from the entire catchment. Here we compare concentrations of the TCN Be-10 in 20 detrital sand samples from the Quebrada del Toro (southern Central Andes, Argentina) to a hillslope-process inventory from each contributing catchment. Our comparison reveals a shift from low-slope gullying and scree production in slowly denuding, low-slope areas to steep-slope gullying and landsliding in fast-denuding, steep areas. To investigate whether the nature of hillslope processes (locally excavating or more uniformly denuding) may be reflected in a comparison of the Be-10 concentrations of sand and gravel, we define the normalized sand-gravel index (NSGI) as the Be-10-concentration difference between sand and gravel divided by their summed concentrations. We find a positive, linear relationship between the NSGI and median slope, such that our NSGI values broadly reflect the shift in hillslope processes from low-slope gullying and scree production to steep-slope gullying and landsliding. Higher NSGI values characterize regions affected by steep-slope gullying or landsliding. We relate the large scatter in the relationship, which is exhibited particularly in low-slope areas, to reduced hillslope-channel connectivity and associated transient sediment storage within those catchments. While high NSGI values in well-connected catchments are a reliable signal of deep-excavation processes, hillslope excavation processes may not be reliably recorded by NSGI values where sediment experiences transient storage. (c) 2018 John Wiley & Sons, Ltd.
Y1  - 2018
U6  - https://doi.org/10.1002/esp.4471
SN  - 0197-9337
SN  - 1096-9837
VL  - 43
IS  - 15
SP  - 3086
EP  - 3098
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Bufe, Aaron
A1  - Turowski, Jens M.
A1  - Burbank, Douglas W.
A1  - Paola, Chris
A1  - Wickert, Andrew D.
A1  - Tofelde, Stefanie
T1  - Controls on the lateral channel-migration rate of braided channel systems in coarse non-cohesive sediment
JF  - Earth surface processes and landforms : the journal of the British Geomorphological Research Group
N2  - Lateral movements of alluvial river channels control the extent and reworking rates of alluvial fans, floodplains, deltas, and alluvial sections of bedrock rivers. These lateral movements can occur by gradual channel migration or by sudden changes in channel position (avulsions). Whereas models exist for rates of river avulsion, we lack a detailed understanding of the rates of lateral channel migration on the scale of a channel belt. In a two-step process, we develop here an expression for the lateral migration rate of braided channel systems in coarse, non-cohesive sediment. On the basis of photographic and topographic data from laboratory experiments of braided channels performed under constant external boundary conditions, we first explore the impact of autogenic variations of the channel-system geometry (i.e. channel-bank heights, water depths, channel-system width, and channel slope) on channel-migration rates. In agreement with theoretical expectations, we find that, under such constant boundary conditions, the laterally reworked volume of sediment is constant and lateral channel-migration rates scale inversely with the channel-bank height. Furthermore, when channel-bank heights are accounted for, lateral migration rates are independent of the remaining channel geometry parameters. These constraints allow us, in a second step, to derive two alternative expressions for lateral channel-migration rates under different boundary conditions using dimensional analysis. Fits of a compilation of laboratory experiments to these expressions suggest that, for a given channel bank-height, migration rates are strongly sensitive to water discharges and more weakly sensitive to sediment discharges. In addition, external perturbations, such as changes in sediment and water discharges or base level fall, can indirectly affect lateral channel-migration rates by modulating channel-bank heights.
KW  - braided alluvial rivers
KW  - physical experiments
KW  - channel migration
Y1  - 2019
U6  - https://doi.org/10.1002/esp.4710
SN  - 0197-9337
SN  - 1096-9837
VL  - 44
IS  - 14
SP  - 2823
EP  - 2836
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Tofelde, Stefanie
A1  - Schildgen, Taylor F.
A1  - Savi, Sara
A1  - Pingel, Heiko
A1  - Wickert, Andrew D.
A1  - Bookhagen, Bodo
A1  - Wittmann, Hella
A1  - Alonso, Ricardo N.
A1  - Cottle, John
A1  - Strecker, Manfred
T1  - 100 kyr fluvial cut-and-fill terrace cycles since the Middle Pleistocene in the southern Central Andes, NW Argentina
JF  - Earth & planetary science letters
N2  - Fluvial fill terraces in intermontane basins are valuable geomorphic archives that can record tectonically and/or climatically driven changes of the Earth-surface process system. However, often the preservation of fill terrace sequences is incomplete and/or they may form far away from their source areas, complicating the identification of causal links between forcing mechanisms and landscape response, especially over multi-millennial timescales. The intermontane Toro Basin in the southern Central Andes exhibits at least five generations of fluvial terraces that have been sculpted into several-hundred-meter-thick Quaternary valley-fill conglomerates. New surface-exposure dating using nine cosmogenic Be-10 depth profiles reveals the successive abandonment of these terraces with a 100 kyr cyclicity between 75 +/- 7 and 487 +/- 34 ka. Depositional ages of the conglomerates, determined by four Al-26/Be-10 burial samples and U-Pb zircon ages of three intercalated volcanic ash beds, range from 18 +/- 141 to 936 +/- 170 ka, indicating that there were multiple cut-and-fill episodes. Although the initial onset of aggradation at similar to 1 Ma and the overall net incision since ca. 500 ka can be linked to tectonic processes at the narrow basin outlet, the superimposed 100 kyr cycles of aggradation and incision are best explained by eccentricity-driven climate change. Within these cycles, the onset of river incision can be correlated with global cold periods and enhanced humid phases recorded in paleoclimate archives on the adjacent Bolivian Altiplano, whereas deposition occurred mainly during more arid phases on the Altiplano and global interglacial periods. We suggest that enhanced runoff during global cold phases - due to increased regional precipitation rates, reduced evapotranspiration, or both - resulted in an increased sediment-transport capacity in the Toro Basin, which outweighed any possible increases in upstream sediment supply and thus triggered incision. Compared with two nearby basins that record precessional (21-kyr) and long-eccentricity (400-kyr) forcing within sedimentary and geomorphic archives, the recorded cyclicity scales with the square of the drainage basin length. (C) 2017 Elsevier B.V. All rights reserved.
KW  - Be-10 depth-profiles
KW  - surface inflation
KW  - aggradation-incision cycles
KW  - glacial-interglacial cycles
KW  - landscape response to climate change
KW  - Eastern Cordillera
Y1  - 2017
U6  - https://doi.org/10.1016/j.epsl.2017.06.001
SN  - 0012-821X
SN  - 1385-013X
VL  - 473
SP  - 141
EP  - 153
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Schwanghart, Wolfgang
A1  - Bernhardt, Anne
A1  - Stolle, Amelie
A1  - Hoelzmann, Philipp
A1  - Adhikari, Basanta R.
A1  - Andermann, Christoff
A1  - Tofelde, Stefanie
A1  - Merchel, Silke
A1  - Rugel, Georg
A1  - Fort, Monique
A1  - Korup, Oliver
T1  - Repeated catastrophic valley infill following medieval earthquakes in the Nepal Himalaya
JF  - Science
N2  - Geomorphic footprints of past large Himalayan earthquakes are elusive, although they are urgently needed for gauging and predicting recovery times of seismically perturbed mountain landscapes. We present evidence of catastrophic valley infill following at least three medieval earthquakes in the Nepal Himalaya. Radiocarbon dates from peat beds, plant macrofossils, and humic silts in fine-grained tributary sediments near Pokhara, Nepal’s second-largest city, match the timing of nearby M > 8 earthquakes in ~1100, 1255, and 1344 C.E. The upstream dip of tributary valley fills and x-ray fluorescence spectrometry of their provenance rule out local sources. Instead, geomorphic and sedimentary evidence is consistent with catastrophic fluvial aggradation and debris flows that had plugged several tributaries with tens of meters of calcareous sediment from a Higher Himalayan source >60 kilometers away.
Y1  - 2016
U6  - https://doi.org/10.1126/science.aac9865
SN  - 0036-8075
SN  - 1095-9203
VL  - 351
SP  - 147
EP  - 150
PB  - American Assoc. for the Advancement of Science
CY  - Washington
ER  - 
TY  - JOUR
A1  - Schildgen, Taylor F.
A1  - Robinson, Ruth A. J.
A1  - Savi, Sara
A1  - Phillips, William M.
A1  - Spencer, Joel Q. G.
A1  - Bookhagen, Bodo
A1  - Scherler, Dirk
A1  - Tofelde, Stefanie
A1  - Alonso, Ricardo N.
A1  - Kubik, Peter W.
A1  - Binnie, Steven A.
A1  - Strecker, Manfred
T1  - Landscape response to late Pleistocene climate change in NW Argentina: Sediment flux modulated by basin geometry and connectivity
JF  - Journal of geophysical research : Earth surface
N2  - Fluvial fill terraces preserve sedimentary archives of landscape responses to climate change, typically over millennial timescales. In the Humahuaca Basin of NW Argentina (Eastern Cordillera, southern Central Andes), our 29 new optically stimulated luminescence ages of late Pleistocene fill terrace sediments demonstrate that the timing of past river aggradation occurred over different intervals on the western and eastern sides of the valley, despite their similar bedrock lithology, mean slopes, and precipitation. In the west, aggradation coincided with periods of increasing precipitation, while in the east, aggradation coincided with decreasing precipitation or more variable conditions. Erosion rates and grain size dependencies in our cosmogenic Be-10 analyses of modern and fill terrace sediments reveal an increased importance of landsliding compared to today on the west side during aggradation, but of similar importance during aggradation on the east side. Differences in the timing of aggradation and the Be-10 data likely result from differences in valley geometry, which causes sediment to be temporarily stored in perched basins on the east side. It appears as if periods of increasing precipitation triggered landslides throughout the region, which induced aggradation in the west, but blockage of the narrow bedrock gorges downstream from the perched basins in the east. As such, basin geometry and fluvial connectivity appear to strongly influence the timing of sediment movement through the system. For larger basins that integrate subbasins with differing geometries or degrees of connectivity (like Humahuaca), sedimentary responses to climate forcing are likely attenuated.
KW  - berylium-10
KW  - optically stimulated luminescence
KW  - Humahuaca Basin
KW  - South American Monsoon System
KW  - fluvial terraces
KW  - landscape connectivity
Y1  - 2016
U6  - https://doi.org/10.1002/2015JF003607
SN  - 2169-9003
SN  - 2169-9011
VL  - 121
SP  - 392
EP  - 414
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Rohrmann, Alexander
A1  - Sachse, Dirk
A1  - Mulch, Andreas
A1  - Pingel, Heiko
A1  - Tofelde, Stefanie
A1  - Alonso, Ricardo N.
A1  - Strecker, Manfred
T1  - Miocene orographic uplift forces rapid hydrological change in the southern central Andes
JF  - Scientific reports
N2  - Rainfall in the central Andes associated with the South American Monsoon and the South American Low-Level Jet results from orographic effects on atmospheric circulation exerted by the Andean Plateau and the Eastern Cordillera. However, despite its importance for South American climate, no reliable records exist that allow decoding the evolution of thresholds and interactions between Andean topography and atmospheric circulation, especially regarding the onset of humid conditions in the inherently dry southern central Andes. Here, we employ multi-proxy isotope data of lipid biomarkers, pedogenic carbonates and volcanic glass from the Eastern Cordillera of NW Argentina and present the first long-term evapotranspiration record. We find that regional eco-hydrology and vegetation changes are associated with initiation of moisture transport via the South American Low-Level Jet at 7.6 Ma, and subsequent lateral growth of the orogen at 6.5 Ma. Our results highlight that topographically induced changes in atmospheric circulation patterns, not global climate change, were responsible for late Miocene environmental change in this part of the southern hemisphere. This suggests that mountain building over time fundamentally controlled habitat evolution along the central Andes.
Y1  - 2016
U6  - https://doi.org/10.1038/srep35678
SN  - 2045-2322
VL  - 6
SP  - 4283
EP  - 4306
PB  - Nature Publ. Group
CY  - London
ER  -