Inland aeolian deposits of south‐west France: facies, stratigraphy and chronology

Bertrán, Pascal; Bateman, Mark D.; Hernandez, Marion; Mercier, Norbert; Millet, Dominique; Sitzia, Luca; Tastet, Jean-Pierre

doi:10.1002/jqs.1461

Cited by 55 publications

(77 citation statements)

References 70 publications

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“…However, the spatial distribution of superficial carbonated sand does not explain the increase in TA in 3rd-order streams. This suggests that the increase of TA is due to deeper groundwater inputs that are in contact with carbonated sand layers (Legigan, 1979;Bertran et al, 2009, Bertran et al, 2011, consistent with the increase in TA and d 13 C-DIC during the base flow period (Fig. 2a and c).…”

supporting

confidence: 61%

“…The Leyre catchment is a very flat, coastal plain with a mean slope lower than 1.25‰ and a mean altitude lower than 50 m (Jolivet et al, 2007). The lithology is relatively homogeneous and composed of different sandy permeable surface layers dating from the Plio-Quaternary Epoch (Legigan, 1979;Bertran et al, 2009, Bertran et al, 2011 (Fig. 1).…”

Section: Study Sitementioning

confidence: 99%

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Carbon dioxide degassing at the groundwater-stream-atmosphere interface: isotopic equilibration and hydrological mass balance in a sandy watershed

Deirmendjian

Abril

2018

Journal of Hydrology

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a b s t r a c tStreams and rivers emit significant amounts of CO 2 and constitute a preferential pathway of carbon transport from terrestrial ecosystems to the atmosphere. However, the estimation of CO 2 degassing based on the water-air CO 2 gradient, gas transfer velocity and stream surface area is subject to large uncertainties. Furthermore, the stable isotope signature of dissolved inorganic carbon (d 13 C-DIC) in streams is strongly impacted by gas exchange, which makes it a useful tracer of CO 2 degassing under specific conditions. For this study, we characterized the annual transfers of dissolved inorganic carbon (DIC) along the groundwater-stream-river continuum based on DIC concentrations, stable isotope composition and measurements of stream discharges. We selected a homogeneous, forested and sandy lowland watershed as a study site, where the hydrology occurs almost exclusively through drainage of shallow groundwater (no surface runoff). We observed the first general spatial pattern of decreases in pCO 2 and DIC and an increase in d 13 C-DIC from groundwater to stream orders 1 and 2, which was due to the experimentally verified faster degassing of groundwater 12 C-DIC compared to 13 C-DIC. This downstream enrichment in 13 C-DIC could be modelled by simply considering the isotopic equilibration of groundwater-derived DIC with the atmosphere during CO 2 degassing. A second spatial pattern occurred between stream orders 2 and 4, consisting of an increase in the proportion of carbonate alkalinity to the DIC accompanied by the enrichment of 13 C in the stream DIC, which was due to the occurrence of carbonate rock weathering downstream. We could separate the contribution of these two processes (gas exchange and carbonate weathering) in the stable isotope budget of the river network. Thereafter, we built a hydrological mass balance based on drainages and the relative contribution of groundwater in streams of increasing order. After combining with the dissolved CO 2 concentrations, we quantified CO 2 degassing for each stream order for the whole watershed. Approximately 75% of the total CO 2 degassing from the watershed occurred in first-and second-order streams. Furthermore, from stream order 2-4, our CO 2 degassing fluxes compared well with those based on stream hydraulic geometry, water pCO 2 , gas transfer velocity, and stream surface area. In first-order streams, however, our approach showed CO 2 fluxes that were twice as large, suggesting that a fraction of degassing occurred as hotspots in the vicinity of groundwater resurgence and was missed by conventional stream sampling.

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supporting

confidence: 61%

Section: Study Sitementioning

confidence: 99%

Carbon dioxide degassing at the groundwater-stream-atmosphere interface: isotopic equilibration and hydrological mass balance in a sandy watershed

Deirmendjian

Abril

2018

Journal of Hydrology

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“…These sedimentary characteristics overlap with those found in modern aeolian sands from Mingsha Mountain ( Fig. 4c) and suffice to discriminate them from lakeshore facies (Goudie 1987;Hu et al 2001;Russell 2004, 2009;Zhang et al 2011;Bertran et al 2011Bertran et al , 2016. Aeolian horizons of the Qigequan Formation also contain some clay and mica particles apparently transported by the wind and deposited under lacustrine conditions.…”

Section: Grain Size Distributionsmentioning

confidence: 62%

“…3b). Core sandstones at 866.6 m (Qijia 1 Well) resembled (Bertran et al 2011), and outcrop around Mingsha Mountain (Fig. 3c).…”

Section: Sedimentary Characteristicsmentioning

confidence: 99%

Discovery and significance of Quaternary aqueously deposited aeolian sandstones in the Sanhu area, Qaidam Basin, China

Mao

Guo

2018

Pet. Sci.

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Influenced by neo-tectonic movement, the Sanhu area of China's Qaidam Basin formed in the Quaternary in response to migration of its depocentre. A study of core material from the Qijia 1 Well reveals novel Quaternary aqueously deposited aeolian sandstones in the Qigequan Formation of the Sanhu area. Here we report the sedimentary petrology and geochemistry data of these deposits that constrain their depositional history. Evidence for aeolian influence during deposition includes: sorting and roundness, pure quartz sand with single mode grain size distribution and few suspension materials, very fine sand grain size distribution indicating sorting by saltation and suspension transport, dish-shaped and crescentshaped pits in grain surfaces indicating aeolian transport and chemical composition similar to that observed in active or recent dune deposits, namely enrichment in SiO 2 , Na 2 O, and MgO relative to the sand dam sediment in the lakeshore. Identification of these aqueously deposited aeolian sandstones expands the range of sedimentary deposit types found in the Sanhu area and improves understanding of its paleoclimatic history.

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“…1) (Jolivet et al, 2007). The lithology is relatively homogeneous and composed of sandy permeable surface layers dating from the PlioceneQuaternary period (Bertran et al, 2009(Bertran et al, , 2011Legigan, 1979).…”

Section: Study Sitementioning

confidence: 99%

Hydro-ecological controls on dissolved carbon dynamics in groundwater and export to streams in a temperate pine forest

et al. 2018

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Abstract. We studied the export of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) from forested shallow groundwater to first-order streams, based on groundwater and surface water sampling and hydrological data. The selected watershed was particularly convenient for such study, with a very low slope, with pine forest growing on sandy permeable podzol and with hydrology occurring exclusively through drainage of shallow groundwater (no surface runoff). A forest plot was instrumented for continuous eddy covariance measurements of precipitation, evapotranspiration, and net ecosystem exchanges of sensible and latent heat fluxes as well as CO 2 fluxes. Shallow groundwater was sampled with three piezometers located in different plots, and surface waters were sampled in six first-order streams; river discharge and drainage were modeled based on four gauging stations. On a monthly basis and on the plot scale, we found a good consistency between precipitation on the one hand and the sum of evapotranspiration, shallow groundwater storage and drainage on the other hand. DOC and DIC stocks in groundwater and exports to first-order streams varied drastically during the hydrological cycle, in relation with water table depth and amplitude. In the groundwater, DOC concentrations were maximal in winter when the water table reached the superficial organic-rich layer of the soil. In contrast, DIC (in majority excess CO 2 ) in groundwater showed maximum concentrations at low water table during late summer, concomitant with heterotrophic conditions of the forest plot. Our data also suggest that a large part of the DOC mobilized at high water table was mineralized to DIC during the following months within the groundwater itself. In firstorder streams, DOC and DIC followed an opposed seasonal trend similar to groundwater but with lower concentrations. On an annual basis, leaching of carbon to streams occurred as DIC and DOC in similar proportion, but DOC export occurred in majority during short periods of the highest water table, whereas DIC export was more constant throughout the year. Leaching of forest carbon to first-order streams represented a small portion (approximately 2 %) of the net land CO 2 sink at the plot. In addition, approximately 75 % of the DIC exported from groundwater was not found in streams, as it returned very fast to the atmosphere through CO 2 degassing.

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Inland aeolian deposits of south‐west France: facies, stratigraphy and chronology

Cited by 55 publications

References 70 publications

Carbon dioxide degassing at the groundwater-stream-atmosphere interface: isotopic equilibration and hydrological mass balance in a sandy watershed

Carbon dioxide degassing at the groundwater-stream-atmosphere interface: isotopic equilibration and hydrological mass balance in a sandy watershed

Discovery and significance of Quaternary aqueously deposited aeolian sandstones in the Sanhu area, Qaidam Basin, China

Hydro-ecological controls on dissolved carbon dynamics in groundwater and export to streams in a temperate pine forest

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