Uniform grain-size distribution in the active layer of a shallow, gravel-bedded, braided river (the Urumqi River, China) and implications for paleo-hydrology
<p>The grain-size distribution of ancient alluvial systems is commonly determined from surface samples of vertically exposed sections of gravel deposits. This method relies on the hypothesis that the grain-size distribution obtained from a vertical cross section is equivalent to that of th...
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Copernicus Publications
2018-11-01
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| Series: | Earth Surface Dynamics |
| Online Access: | https://www.earth-surf-dynam.net/6/1011/2018/esurf-6-1011-2018.pdf |
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doaj-38b3a003b68e481e8ff6ef319bb7c9b32020-11-25T01:31:18ZengCopernicus PublicationsEarth Surface Dynamics2196-63112196-632X2018-11-0161011102110.5194/esurf-6-1011-2018Uniform grain-size distribution in the active layer of a shallow, gravel-bedded, braided river (the Urumqi River, China) and implications for paleo-hydrologyL. Guerit0L. Barrier1Y. Liu2C. Narteau3E. Lajeunesse4E. Gayer5F. Métivier6GET, Université de Toulouse, CNRS, IRD, UPS, Toulouse, FranceInstitut de Physique du Globe de Paris – Sorbonne Paris Cité, Université Paris Diderot, CNRS, UMR 7154, Paris, FranceSchool of Resources and Environmental Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, ChinaInstitut de Physique du Globe de Paris – Sorbonne Paris Cité, Université Paris Diderot, CNRS, UMR 7154, Paris, FranceInstitut de Physique du Globe de Paris – Sorbonne Paris Cité, Université Paris Diderot, CNRS, UMR 7154, Paris, FranceInstitut de Physique du Globe de Paris – Sorbonne Paris Cité, Université Paris Diderot, CNRS, UMR 7154, Paris, FranceInstitut de Physique du Globe de Paris – Sorbonne Paris Cité, Université Paris Diderot, CNRS, UMR 7154, Paris, France<p>The grain-size distribution of ancient alluvial systems is commonly determined from surface samples of vertically exposed sections of gravel deposits. This method relies on the hypothesis that the grain-size distribution obtained from a vertical cross section is equivalent to that of the riverbed. Such an hypothesis implies first that the sediments are uniform in size in the river bed, and second that the sampling method implemented on a vertical section leads to a grain-size distribution equivalent to the bulk one. Here, we report a field test of this hypothesis on granulometric samples collected in an active, gravel-bedded, braided stream: the Urumqi River in China. We compare data from volumetric samples of a trench excavated in an active thread and from surface counts performed on the trench vertical faces. Based on this data set, we show that the grain-size distributions obtained from all the samples are similar and that the deposit is uniform at the scale of the river active layer, a layer extending from the surface to a depth of approximately 10 times the size of the largest clasts. As a consequence, the grid-by-number method implemented vertically leads to a grain-size distribution equivalent to the one obtained by a bulk volumetric sampling. This study thus brings support to the hypothesis that vertical surface counts provide an accurate characterization of the grain-size distribution of paleo-braided rivers.</p>https://www.earth-surf-dynam.net/6/1011/2018/esurf-6-1011-2018.pdf |
| collection |
DOAJ |
| language |
English |
| format |
Article |
| sources |
DOAJ |
| author |
L. Guerit L. Barrier Y. Liu C. Narteau E. Lajeunesse E. Gayer F. Métivier |
| spellingShingle |
L. Guerit L. Barrier Y. Liu C. Narteau E. Lajeunesse E. Gayer F. Métivier Uniform grain-size distribution in the active layer of a shallow, gravel-bedded, braided river (the Urumqi River, China) and implications for paleo-hydrology Earth Surface Dynamics |
| author_facet |
L. Guerit L. Barrier Y. Liu C. Narteau E. Lajeunesse E. Gayer F. Métivier |
| author_sort |
L. Guerit |
| title |
Uniform grain-size distribution in the active layer of a shallow, gravel-bedded, braided river (the Urumqi River, China) and implications for paleo-hydrology |
| title_short |
Uniform grain-size distribution in the active layer of a shallow, gravel-bedded, braided river (the Urumqi River, China) and implications for paleo-hydrology |
| title_full |
Uniform grain-size distribution in the active layer of a shallow, gravel-bedded, braided river (the Urumqi River, China) and implications for paleo-hydrology |
| title_fullStr |
Uniform grain-size distribution in the active layer of a shallow, gravel-bedded, braided river (the Urumqi River, China) and implications for paleo-hydrology |
| title_full_unstemmed |
Uniform grain-size distribution in the active layer of a shallow, gravel-bedded, braided river (the Urumqi River, China) and implications for paleo-hydrology |
| title_sort |
uniform grain-size distribution in the active layer of a shallow, gravel-bedded, braided river (the urumqi river, china) and implications for paleo-hydrology |
| publisher |
Copernicus Publications |
| series |
Earth Surface Dynamics |
| issn |
2196-6311 2196-632X |
| publishDate |
2018-11-01 |
| description |
<p>The
grain-size distribution of ancient alluvial systems is commonly determined
from surface samples of vertically exposed sections of gravel deposits. This
method relies on the hypothesis that the grain-size distribution obtained
from a vertical cross section is equivalent to that of the riverbed. Such an
hypothesis implies first that the sediments are uniform in size in the river
bed, and second that the sampling method implemented on a vertical section
leads to a grain-size distribution equivalent to the bulk one. Here, we
report a field test of this hypothesis on granulometric samples collected in
an active, gravel-bedded, braided stream: the Urumqi River in China. We
compare data from volumetric samples of a trench excavated in an active
thread and from surface counts performed on the trench vertical faces. Based
on this data set, we show that the grain-size distributions obtained from all
the samples are similar and that the deposit is uniform at the scale of the
river active layer, a layer extending from the surface to a depth of
approximately 10 times the size of the largest clasts. As a consequence, the
grid-by-number method implemented vertically leads to a grain-size
distribution equivalent to the one obtained by a bulk volumetric sampling.
This study thus brings support to the hypothesis that vertical surface counts
provide an accurate characterization of the grain-size distribution of
paleo-braided rivers.</p> |
| url |
https://www.earth-surf-dynam.net/6/1011/2018/esurf-6-1011-2018.pdf |
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