Les canyons karstiques "Nouvelles approches de problèmes géomorphologiques classiques" (spécialement dans les domaines méditerranéens et tropicaux) [The karstic canyons, geomorphological problems and new directions (particularly in mediterranean and tropical lands).]

Abstract

In account of many studies (particularly geotechnical for dams build), these canyons are now defined in their relations with the karst hydrosystem : in their hydrological functions, and by the relations with neotectonics, change of base-level, and development of the endokarst. Exceptionally some anse from a collapse processes (breakdown in the karst passages). These news studies give data up the hydromecanical (evorsion) and hydrochemical processes and speed of the incision (maximum m proglacial canyons). The profiles of streams lead from chaotic to graded ; however in some mediterranean canyons travertines dams have blocked the incision. In most cases a turn or a sinuosity is in connection to fracturation and some incised meanders only in table like structures. The cutting of the Pont d'Arc (Ardèche) make a good model of karstic short cut. Many processes infere in the evolution of the cliffs and sides : unloading and gravity (mass-movements, collapses), cut off of the karst tubes and caves ("baumes-porches"), cryoclastism (inherited penglacial forms in North-mediterranean land, particularly frost-pockets and graded sides), weathering, calcrusts (case-hardening) and travertines deposits. On that account, the comparison between Sumidero of Grijalva (Chiapas, Mexico) and the mediterranean canyons is very useful.

Geomorphological significance of the palaeodrainage network on a karst plateau: The Una–Korana plateau, Dinaric karst, Croatia

“…Therefore, dry valleys, palaeohydrographic networks and their relations with other karst forms can be used in the reconstruction of karst evolution under various conditions and in different areas (e.g. Day, 1983a,b;Smart and Statham, 1984;Sauro, 1991;Nicod, 1997;Quinif, 1999;Phillips et al, 2004;Monod et al, 2006;Gioia et al, 2011;De Waele et al, 2012;Benac et al, 2013;Haryono, 2013). The significance of the tectonic uplifting of karstified terrain in this process has often been emphasised.…”

Geomorphology of the Jebel Qara and coastal plain of Salalah (Dhofar, southern Sultanate of Oman)

“…Occasionally, ponds can last for several months and extreme precipitations can cause huge flooding episodes ( Figure 6). The tectonic uplift of the Jebel Qara favoured the formation of deeply incised valleys, likely originated from the underground karst network and deepened by linear erosion after their collapse (see: Hill & Polyak, 2014;Nicod, 1997). The hypothesis of a karst-related evolution of the hydrographic net is confirmed by the occurrence of several large sinkholes along wadis; in a few cases, wadis drain into or are captured by sinkholes ( Figure 5).…”

Karst landscape and hydrology in Morocco: research trends and perspectives

“…As reported by Nicod (1997), ''land subsidence or collapses in relation with the active dissolution of the gypsum and other evaporites, particularly in depth, at the groundwater level may engender small lakes. They arise from a complex evolution''.…”