In:
Karstologia : revue de karstologie et de spéléologie physique, PERSEE Program, Vol. 56, No. 1 ( 2010), p. 9-16
Abstract:
The combe de Crousette Area (Mercantour National Park, Mount Mounier, Alpes-Maritimes, France) : Landscape asset of a juvenile postglacial karst. The Combe de Crousette is a plateau at about 2300 m a.s.l., located in the Southern French Alps, in the core area of the Mercantour National Park, at the foot of Mount Mounier. The landscape displays a mosaic of karren fields and alpine meadows. The plateau is split by a depression named Laces, covered with peat bogs, where a small creek is meandering. The Sallevieille cliff borders the plateau to the north. It corresponds to a 100 m-thick Tithonian limestone sandwiched between marly strata of Kimmeridgian and Cretaceous age, respectively. The tabular structure is cut by numerous horsts and basins, the Laces being the largest. Due to the high elevation and to the northward exposure, glacial tongues remained in cirques until the Preboreal (= 7 ka). Glacial and periglacial processes produced scree and moraines that cover the surrounding slopes. These surficial deposits contain water bodies that feed perennial or temporary runoff, which sink into the underground when reaching the limestones. The many sinkholes are plugged with clay and blocks. The Ubac de Mounier area is drained towards a sinkhole in moraines, which probably feeds the Laces springs. The resulting creek sinks in mechanical joints in the vicinity of the Sallevieille cliff. Additional sinkholes, together with diffuse recharge on the limestone, feed the springs located at the foot of the Sallevieille cliff. A few small shafts have developed by sinking runoff originating from the small basins covered with meadows. They are enlarged to a shallow depth by melting of snow plugs. These juvenile shafts as well as the surface features are recent. Apart from the Laces polje, the glacial features such as glacio-karstic structural banks, roches moutonnees and glacial scars, the other features developed after the glacial retreat. The sides of the Schichttreppenkarst are etched by diverse type of karren (meanders, grikes, sharpened edges...) and corrosional notches under soil are exhumed after the retreat of the meadows. The insoluble chert banks act as small pedestals and allow to measure the depth of the postglacial karst denudation, which is only 5 cm. After the erosion of the marly cover by wurmian or tardiglacial glaciers, this juvenile karst began to develop mainly due to snowmelt. The still unknown underground flow paths seem to be already well-organized, but caves and surface features are still under development. Additional studies would provide important issues : peat may have recorded the timing of the glacial retreat and consequently the evolution of the landscape ; dye tracing should highlight the dynamics of underground flow in such a juvenile karst. Finally, the karst landscape offers a unique potential of patrimonial valorization within the frame of the core area of the Mercantour National Park, which does not harbor much high-altitude karst landscapes.
Type of Medium:
Online Resource
ISSN:
0751-7688
DOI:
10.3406/karst.2010.2678
Language:
French
Publisher:
PERSEE Program
Publication Date:
2010
SSG:
13
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