Mariotti, A., Blard, P. H., Charreau, J., Toucanne, S., Jorry, S. J., Molliex, S., Bourl`es, D. L., Auma^itre, G., Keddadouche, K. Nonlinear forcing of climate on mountain denudation during glaciations (Article de journal) Dans: Nature Geoscience, vol. 14, p. 16–22, 2021. @article{Mariotti_etal2021,
title = {Nonlinear forcing of climate on mountain denudation during glaciations},
author = {A. Mariotti and P. H. Blard and J. Charreau and S. Toucanne and S. J. Jorry and S. Molliex and D. L. Bourl`es and G. Auma^itre and K. Keddadouche},
doi = {10.1038/s41561-020-00672-2},
year = {2021},
date = {2021-01-01},
journal = {Nature Geoscience},
volume = {14},
pages = {16--22},
abstract = {Denudation is one of the main processes that shapes landscapes. Because temperature, precipitation and glacial extents are key factors involved in denudation, climatic fluctuations are thought to exert a strong control on this parameter over geological timescales. However, the direct impacts of climatic variations on denudation remain controversial, particularly those involving the Quaternary glacial cycles in mountain environments. Here we measure in situ cosmogenic 10Be concentration in quartz in marine turbidites of two high-resolution cores collected in the Mediterranean Sea, providing a near-continuous (temporal resolution of 1--2thinspacekyr) reconstruction of denudation in the Southern Alps since 75thinspacekyr ago (ka). This high-resolution palaeo-denudation record can be compared with well-constrained climatic variations over the last glacial cycle. Our results indicate that total denudation rates were approximately two times higher than present during the Last Glacial Maximum (26.5--19thinspaceka), the glacial component of the denudation rates being 1.5+0.9−1.0thinspacemmthinspaceyr−1. However, during moderately glaciated times (74--29thinspaceka), denudation rates were similar to those today (0.24thinspacetextpmthinspace0.04thinspacemmthinspaceyr−1). This suggests a nonlinear forcing of climate on denudation, mainly controlled by the interplay between glacier velocity and basin topography. Hence, the onset of Quaternary glaciations, 2.6 million years ago, did not necessarily induce a synchronous global denudation pulse.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Denudation is one of the main processes that shapes landscapes. Because temperature, precipitation and glacial extents are key factors involved in denudation, climatic fluctuations are thought to exert a strong control on this parameter over geological timescales. However, the direct impacts of climatic variations on denudation remain controversial, particularly those involving the Quaternary glacial cycles in mountain environments. Here we measure in situ cosmogenic 10Be concentration in quartz in marine turbidites of two high-resolution cores collected in the Mediterranean Sea, providing a near-continuous (temporal resolution of 1--2thinspacekyr) reconstruction of denudation in the Southern Alps since 75thinspacekyr ago (ka). This high-resolution palaeo-denudation record can be compared with well-constrained climatic variations over the last glacial cycle. Our results indicate that total denudation rates were approximately two times higher than present during the Last Glacial Maximum (26.5--19thinspaceka), the glacial component of the denudation rates being 1.5+0.9−1.0thinspacemmthinspaceyr−1. However, during moderately glaciated times (74--29thinspaceka), denudation rates were similar to those today (0.24thinspacetextpmthinspace0.04thinspacemmthinspaceyr−1). This suggests a nonlinear forcing of climate on denudation, mainly controlled by the interplay between glacier velocity and basin topography. Hence, the onset of Quaternary glaciations, 2.6 million years ago, did not necessarily induce a synchronous global denudation pulse. |
Mariotti, A., Blard, P. H., Charreau, J., Petit, C., Molliex, S., Team., ASTER Denudation systematics inferred from in situ cosmogenic 10Be concentrations in fine (50--100thinspacetextmum) and medium (100--250thinspacetextmum) sediments of the Var River basin, southern French Alps (Article de journal) Dans: Earth Surface Dynamics, vol. 7, p. 1059–1074, 2019. @article{Mariotti_etal2019,
title = {Denudation systematics inferred from in situ cosmogenic 10Be concentrations in fine (50--100thinspacetextmum) and medium (100--250thinspacetextmum) sediments of the Var River basin, southern French Alps},
author = {A. Mariotti and P. H. Blard and J. Charreau and C. Petit and S. Molliex and ASTER Team.},
doi = {10.5194/esurf-7-1059-2019},
year = {2019},
date = {2019-01-01},
journal = {Earth Surface Dynamics},
volume = {7},
pages = {1059--1074},
abstract = {Marine sedimentary archives are well dated and often span several glacial cycles ; cosmogenic 10Be concentrations in their detrital quartz grains could thus offer the opportunity to reconstruct a wealth of past denudation rates. However, these archives often comprise sediments much finer (\<250thinspacetextmum) than typically analyzed in 10Be studies, and few studies have measured 10Be concentrations in quartz grains smaller than 100thinspacetextmum or assessed the impacts of mixing, grain size, and interannual variability on the 10Be concentrations of such fine-grained sediments. Here, we analyzed the in situ cosmogenic 10Be concentrations of quartz grains in the 50--100 and 100--250thinspacetextmum size fractions of sediments from the Var basin (southern French Alps) to test the reliability of denudation rates derived from 10Be analyses of fine sands. The Var basin has a short transfer zone and highly variable morphology, climate, and geology, and we test the impact of these parameters on the observed 10Be concentrations. Both analyzed size fractions returned similar 10Be concentrations in downstream locations, notably at the Vartextquoterights outlet, where concentrations ranged from (4.02textpm0.78)texttimes104 to (4.40textpm0.64)texttimes104thinspaceatomsthinspaceg−1 of quartz. By comparing expected and observed 10Be concentrations at three major river junctions, we interpret that sediment mixing is efficient throughout the Var basin. We resampled four key locations 1thinspaceyear later, and despite variable climatic parameters during that period, interannual 10Be concentrations were in agreement within uncertainties, except for one upper subbasin. The 10Be-derived denudation rates of Var subbasins range from 0.10textpm0.01 to 0.57textpm0.09thinspacemmthinspaceyr−1, and spatial variations are primarily controlled by the average subbasin slope. The integrated denudation rate of the entire Var basin is 0.24textpm0.04thinspacemmthinspaceyr−1, in agreement with other methods. Our results demonstrate that fine-grained sediments (50--250thinspacetextmum) may return accurate denudation rates and are thus potentially suitable targets for future 10Be applications, such as studies of paleo-denudation rates using offshore sediments.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Marine sedimentary archives are well dated and often span several glacial cycles ; cosmogenic 10Be concentrations in their detrital quartz grains could thus offer the opportunity to reconstruct a wealth of past denudation rates. However, these archives often comprise sediments much finer (<250thinspacetextmum) than typically analyzed in 10Be studies, and few studies have measured 10Be concentrations in quartz grains smaller than 100thinspacetextmum or assessed the impacts of mixing, grain size, and interannual variability on the 10Be concentrations of such fine-grained sediments. Here, we analyzed the in situ cosmogenic 10Be concentrations of quartz grains in the 50--100 and 100--250thinspacetextmum size fractions of sediments from the Var basin (southern French Alps) to test the reliability of denudation rates derived from 10Be analyses of fine sands. The Var basin has a short transfer zone and highly variable morphology, climate, and geology, and we test the impact of these parameters on the observed 10Be concentrations. Both analyzed size fractions returned similar 10Be concentrations in downstream locations, notably at the Vartextquoterights outlet, where concentrations ranged from (4.02textpm0.78)texttimes104 to (4.40textpm0.64)texttimes104thinspaceatomsthinspaceg−1 of quartz. By comparing expected and observed 10Be concentrations at three major river junctions, we interpret that sediment mixing is efficient throughout the Var basin. We resampled four key locations 1thinspaceyear later, and despite variable climatic parameters during that period, interannual 10Be concentrations were in agreement within uncertainties, except for one upper subbasin. The 10Be-derived denudation rates of Var subbasins range from 0.10textpm0.01 to 0.57textpm0.09thinspacemmthinspaceyr−1, and spatial variations are primarily controlled by the average subbasin slope. The integrated denudation rate of the entire Var basin is 0.24textpm0.04thinspacemmthinspaceyr−1, in agreement with other methods. Our results demonstrate that fine-grained sediments (50--250thinspacetextmum) may return accurate denudation rates and are thus potentially suitable targets for future 10Be applications, such as studies of paleo-denudation rates using offshore sediments. |
