Cementation and blackening of Holocene sands by peat-derived humates: A case study from the Great Dune of Pilat, Landes des Gascogne, Southwestern France

0425586 - ÚSMH 2014 RIV NL eng J - Journal Article
Suchý, V. - Sýkorová, Ivana - Havelcová, Martina - Machovič, Vladimír - Zeman, Antonín - Trejtnarová, Hana
Cementation and blackening of Holocene sands by peat-derived humates: A case study from the Great Dune of Pilat, Landes des Gascogne, Southwestern France.
International Journal of Coal Geology. Roč. 114, JUL (2013), s. 19-32. ISSN 0166-5162. E-ISSN 1872-7840
R&D Projects: GA ČR GA205/09/1162; GA ČR(CZ) GA13-18482S
Institutional support: RVO:67985891 ; RVO:68378297
Keywords : humate * peat * cementation * aeolian sand
Subject RIV: DB - Geology ; Mineralogy
Impact factor: 3.313, year: 2013

The base sand layers of the aeolian Great Dune of Pilat, which stretches along the coast of Arcachon Bay, have been locally impregnated with a dark brown to black amorphous organic substance of humate composition. The humate-cemented sand forms a well-indurated horizon 40-50 cm in thickness that developed immediately beneath the Holocene peaty layer (P1 "paleosoil"). The humate, identified by means of FT-IR and Raman micro-spectroscopy, acted both as a cementing agent and as a coloring agent; it formed thin coats and meniscus cements between individual sandstone grains which, in turn, caused the dark, asphaltic-like appearance of the sandstone. Field observations, combined with geochemical analyses, and the presence of identical geochemical compounds recognized in the peat and sandstone humate cement, suggest that the peat-containing low-coalified (R-r = 0.2%) fragments of higher, submerged and floating plants and marine algae deposited in a saline and reducing environment served as an obvious source rock for the humate. The humate derived from decaying organic remains that descended from the peat into the permeable sand, where it indurated irreversibly over a period shorter than 3500 years.
Permanent Link: http://hdl.handle.net/11104/0231416