Abstract
Dolines are closed geomorphological depressions which are surface manifestations of karsticsystems. Usually developed on limestone, they also typify the morphology of the New Caledonianlandscape, particularly on the southern massif of the main island (known as Grande Terre). Thesedolines are evidence of subsidence, suffosion and collapse phenomena resulting from dissolutionweathering of peridotites. However, extensive underground drainage systems are still not yetrecognized. Semi-automatic mapping of dolines is carried out on a 148 kmC area of the Massif duSud from a high accuracy LIDAR digital elevation model. 8,601 dolines ranging from 1 mC to 2 kmCare identified and morphologically characterized with precision. The majority of them are small,shallow and round-shaped, yet more complex shapes are locally observed. Size distribution analysisallows the setting of a threshold of 20,000 mC above which surface processes rather than chemicalweathering control doline evolution. Doline density analysis reveals high concentrations on flat areaswhere ferricrete overlies the complete weathering profile, especially in the case of elevated, rainywatersheds. Dolines are aligned and elongated along a N 135 A 5° major fracture direction, which isinherited from the obduction of the Pacific Plate upper mantle in the Late Eocene. Finally, we proposea pioneering morphometric typology of dolines that provides important clues as to pseudokarsticactivity. We define collapse, bowl-shaped and flat bottom dolines. Collapse and bowl-shaped dolinesare assumed to denote active pseudokarst. They may widen and deepen, or eventually be filled bysediments. They are distinguished from flat bottom dolines that are partially to completely filled, whichsuggests that they are associated with paleo-pseudokarsts. However the groundwater flow pathsassociated with the genesis and evolution of dolines must be clarified, and collapse and bowl-shapeddolines should be hydrologically monitored.