Limited influence of climatic gradients on the denudation of a Mediterranean carbonate landscape

Thomas, Franck; Godard, Vincent; Bellier, Olivier; Benedetti, Lucilla; Ollivier, Vincent; Rizza, Magali; Guillou, Valéry; Hollender, Fabrice; Aumaître, Georges; Bourlès, Didier; Keddadouche, Karim

doi:10.1016/j.geomorph.2018.04.014

Cited by 25 publications

(11 citation statements)

References 91 publications

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“…These lithological and climate characteristics are roughly similar to those in the Classical Karst area, where the mean limestone bedrock lowering rate of 18 mm ka -1 was measured within a period of up to 26 years using micro-erosion meter (Furlani et al, 2009). Even higher denudation rates (30-60 mm ka -1 ) were measured on the exposed carbonate bedrock in SE France (Thomas et al, 2018) and elsewhere in the Mediterranean (Levenson et al, 2017 and references therein). Denudation rates determined on…”

Section: Uncertainties and Assumptions Of The Cosmogenic 36 CL Exposusupporting

confidence: 70%

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Paraglacial adjustment of alluvial fans to the last deglaciation in the Snežnik Mountain, Dinaric karst (Slovenia)

et al. 2019

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Glaciokarst depressions are major glacigenic depocenters in the Dinaric mountain karst areas and often store important information about the timing and nature of glacial processes and paraglacial sediment reworking. This study focuses on Praprotna draga, which is one of the largest glaciokarst depressions in the Snežnik Mountain (Dinaric karst), with an area of ~3.4 km 2 and a maximum depth of 140 m. The western slopes of the depression are characterized by undulated moraine morphology and alluvial fans are filling its entire floor. We present the results on the thickness, origin and age of the sediment infill using a complementary geomorphological, sedimentological, geophysical and dating approach. Distribution of moraines point to two glacial advances that were associated with two main alluvial fan aggradation phases recognised using the electrical resistivity tomography measurements. The youngest alluvial deposits were sampled for cosmogenic 36 Cl analysis using amalgamated carbonate pebbles. The depth profile of 36 Cl concentrations suggests an age of 12.3 ± 1.7 ka when assuming a likely denudation rate of 20 mm ka-1. Since the existence of the Younger Dryas glaciers in the study area is climatically difficult to explain, we tentatively propose that the youngest alluvial deposition in Praprotna draga took place after the glacier retreat during the paraglacial period. Our findings suggest that the time window of paraglacial adjustment in the Snežnik Mountain was brief and likely conditioned by quick recolonization with vegetation and inefficient surface runoff on deglaciated karst terrain.

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Section: Uncertainties and Assumptions Of The Cosmogenic 36 CL Exposusupporting

confidence: 70%

“…The influence of different denudation rates on the age calculations of alluvial deposit was tested by using rates between 0 mm ka -1 and mm ka -1 in steps of mm ka -1 (Table 4). These cover a range of the northern Mediterranean limestone lowering rates (e.g., Cucchi et al, 1995;Plan, 2005;Furlani et al, 2009;Levenson et al, 2017;Thomas et al, 2018).…”

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confidence: 99%

Paraglacial adjustment of alluvial fans to the last deglaciation in the Snežnik Mountain, Dinaric karst (Slovenia)

et al. 2019

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“…The interquartile ranges of the bins are largely overlapping, but a systematic increase can still be observed, consistently with the underlying variation in C HT . The estimated median denudation values are ∼30 and ∼50 mm/ka in the southern and northern part, respectively, which is comparable to denudation rates reported on surrounding landscapes (Siame et al, 2004;Thomas et al, 2017Thomas et al, , 2018. Considering a dip angle of 60 o ( figure 10E) for the hypothetical fault responsible for this differential uplift rate, and assuming topographic steady state, this would imply a ∼20 mm/ka slip rate on this blind thrust.…”

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confidence: 61%

Hillslope denudation and morphologic response across a rock uplift gradient

Godard¹,

Hippolyte²,

Cushing³

et al. 2019

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Documenting the spatial variability of tectonic processes from topography is routinely undertaken through the analysis of river profiles, as a direct relationship between fluvial gradient and rock uplift has been identified by incision models.Similarly, theoretical formulations of hillslope profiles predict a strong dependence on uplift rates. However, the reduced sensitivity of near-threshold hillslopes and the limited availability of high resolution topographic data, has often been a major limitation for their use to investigate tectonic gradients. Here we combined high resolution analysis of hillslope morphology 5 and cosmogenic nuclides derived denudation rates to unravel the distribution of rock uplift across a blind thrust system at the Southwestern Alpine front in France. Our study is located in the Valensole Mio-Pliocene molassic basin, where a series of fold and thrust has deformed a plateau surface. We focused on a series of catchments aligned perpendicular to the main structures.Using a 1-m LiDAR Digital Terrain Model, we extracted hillslopes topographic properties such as hilltop curvature C HT or non-dimensional erosion rates E * . We observed a systematic variation of these metrics coincident with the location of a major 10 underlying thrust system identified by seismic surveys. Using a simple deformation model, the inversion of the E * pattern allows to propose a location and dip for a blind thrust, which are consistent with available geological and geophysical data.We also sampled clasts from eroding conglomerate at several hilltops locations for 10 Be and 26 Al concentration measurement.Calculated hilltops denudation rates range from 40 to 120 mm/ka. These denudation rates appear to be correlated with E * and C HT extracted from the morphological analysis, and are used to derive absolute estimates for the fault slip rate. This 15 high resolution hillslope analysis allows to resolve short wavelength variations in rock uplift, that would not be possible to unravel using commonly used channel profiles based methods. Our joint analysis of topography and geochronological data supports active thrusting at the Southwestern alpine front, and such approaches may bring crucial complementary constraints to morphotectonic analysis for slip rates on slow active faults.Similarly to river profiles, theoretical formulations of hillslope denudation predict a strong dependence of morphological parameters, such as slope or relief, on uplift rates. However, key elements of hillslope behavior such as the threshold stability angle for hillslope material and the non-linear relationship between sediment fluxes and topographic gradient (Roering et al., 1999(Roering et al., , 2001(Roering et al., , 2007, implies that for fixed valley spacing, hillslope morphology can be insensitive to changes in erosion or rock uplift rates over large range values (Burbank et al., 1996;Ouimet et al., 2009). This behavior is a major limitation for the use 50 of hillslope morphology to retrieve information about tectonic gradients. Furth...

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“…Stone et al () first established the use of the 36 Cl cosmogenic nuclide to determine bedrock denudation rates in limestones. Previous studies of 36 Cl denudation rates have focused on exposed bedrock denudation rates, where dissolution is the dominant lowering process (Godard et al, ; Schaller et al, ; Thomas et al, ; Xu et al, ). However, quantification of carbonate denudation at the catchment scale is needed to integrate the effects of mechanical denudation processes along hillslopes and channels and to understand its impact on relief generation.…”

Section: Introductionmentioning

confidence: 99%

Chemical Versus Mechanical Denudation in Meta‐Clastic and Carbonate Bedrock Catchments on Crete, Greece, and Mechanisms for Steep and High Carbonate Topography

et al. 2019

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On Crete—as is common elsewhere in the Mediterranean—carbonate massifs form high mountain ranges whereas topography is lower in areas with meta‐clastic rocks. This observation suggests that differences in denudational processes between carbonate‐rich rocks and quartzofeldspathic units impart a fundamental control on landscape evolution. Here we present new cosmogenic basin‐average denudation rate measurements from both 10Be and 36Cl in meta‐clastic and carbonate bedrock catchments, respectively, to assess relationships between denudation rates, processes, and topographic form. We compare total denudation rates to dissolution rates calculated from 49 new and previously published water samples. Basin‐average denudation rates of meta‐clastic and carbonate catchments are similar, with mean values of ~0.10 mm/a and ~0.13 mm/a, respectively. The contribution of dissolution to total denudation rate was <10% in the one measured meta‐clastic catchment, and ~40% for carbonate catchments (~0.05 mm/a), suggesting the dominance of physical over chemical weathering at the catchment scale in both rock types. Water mass‐balance calculations for three carbonate catchments suggests 40–90% of surface runoff is lost to groundwater. To explore the impact of dissolution and infiltration to groundwater on relief, we develop a numerical model for carbonate denudation. We find that dissolution modifies the river profile channel steepness, and infiltration changes the fluvial response time to external forcing. Furthermore, we show that infiltration of surface runoff to groundwater in karst regions is an efficient way to steepen topography and generate the dramatic relief in carbonates observed throughout Crete and the Mediterranean.

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Limited influence of climatic gradients on the denudation of a Mediterranean carbonate landscape

Cited by 25 publications

References 91 publications

Paraglacial adjustment of alluvial fans to the last deglaciation in the Snežnik Mountain, Dinaric karst (Slovenia)

Paraglacial adjustment of alluvial fans to the last deglaciation in the Snežnik Mountain, Dinaric karst (Slovenia)

Hillslope denudation and morphologic response across a rock uplift gradient

Chemical Versus Mechanical Denudation in Meta‐Clastic and Carbonate Bedrock Catchments on Crete, Greece, and Mechanisms for Steep and High Carbonate Topography

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