Caractérisation des profils de formations superficielles par pénétrométrie dynamique à énergie variable : application aux marnes noires de Draix (Alpes-de-Haute-Provence, France)

Abstract

Characterisation of alteration profiles using dynamic penetrometry with variable energy. Application to weathered black marls, Draix (Alpes-de-Haute-Provence, France). A dynamic penetrometer with variable energy has been tested in a gullied catchment of Callovo-Oxfordian black marls (Draix, Alpes-de-Haute-Provence, France). After calibration and validation, simple convenient geotechnical criteria allow to interpret penetrograms in terms of type and thickness of layers in the weathered marl profile, with a centimetric precision: (1) the loose detrital cover, (2) the more or less compact regolith laying on (3) the marl bedrock. Once calibrated for a specific environment, this new prospecting method appears very useful, rapid and efficient to characterise shallow superficial formations and estimate their volume. To cite this article: O.

Technical note: In situ measurement of flux and isotopic composition of CO<sub>2</sub> released during oxidative weathering of sedimentary rocks

“…Bare rock outcrops are characterized by the development of weathered marls and regolith. Regolith typically extends to at least ∼ 20 cm with the following characteristics: (i) the upper ∼ 3 cm is loose detrital cover composed of millimetre-to-centimetre-sized fragments of marls, (ii) from ∼ 3 to ∼ 10 cm is the loosened upper regolith which is somewhat fragmented, (iii) from ∼ 10 to 20 cm is the compact lower regolith which retains the marl structure but not its cohesion, and (iv) at depths more than ∼ 20 cm is the marl bedrock (unweathered marl) (Maquaire et al, 2002;Mathys and Klotz, 2008;Oostwoud Wijdenes and Ergenzinger, 1998). Lateral variation in the regolith thickness exists with larger thicknesses on crests, intermediate in gullies and minimal in talwegs (Maquaire et al, 2002).…”

Erosion processes in black marl soils at the millimetre scale: preliminary insights from an analogous model

“…Below the regolith is a layer of plate-like unstructured rock. Finally, compacted regolith 10-20 cm thick lies in contact with the bedrock (Maquaire et al, 2002). The clay size fraction of the black marls located in this region has been found to be 35 ± 5 % (Caris and Van Asch, 1991), but the clay mineral content is approximately 10% and is primarily illite with traces of smectite and interstratified clay minerals (Antoine et al, 1995).…”

“…The black marl formation is more than 2000 m thick in certain places (Antoine et al, 1995). The study site has no vegetal cover, and the regolith is usually approximately 40 cm to 1 m thick (Maquaire et al, 2002;Antoine et al, 1995). The upper approximately 10 cm of the regolith is loose detrital material composed of local clasts and platelets (Maquaire et al, 2002).…”

“…The study site has no vegetal cover, and the regolith is usually approximately 40 cm to 1 m thick (Maquaire et al, 2002;Antoine et al, 1995). The upper approximately 10 cm of the regolith is loose detrital material composed of local clasts and platelets (Maquaire et al, 2002). This regolith corresponds to a sandy loam when it has been exposed for long enough to be disaggregated by weathering (Antoine et al, 1995).…”

Conditions climatiques hivernales et processus d’érosion périglaciaires dans les bad-lands marneux de Draix (800 m, Alpes du Sud, France)

“…Vis-à-vis de la structure verticale du substrat, ces trois niveaux correspondent assez bien aux transitions entre le régolite fin supérieur et inférieur (-15 cm), entre le régolite fin et le régolite grossier (-30 cm), entre le régolite grossier et la marne saine (-50 cm). Fait inté-ressant, les deux dernières discontinuités ont également été mises en évidence par des mesures pénétrométriques effectuées à Draix par une autre équipe de recherche (Macaire et al, 2002). Nous pensons que ces niveaux correspondent à trois fronts d'action différentielle du gel.…”