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Climatic Geomorphology
to grooves, which usually collapse, but the most common feature is the presence of caves
in the contact tower-plain, with increases of phreatic or vadose water that accelerates
limestone dissolution in this zone and as a consequence slopes become steeper. This zone
of basal undermining can be emphasized by fluvial erosion. If this activity decreases then
the angle of the basal slope segment declines (Gerstenhauer, 1960) and the tower degrades.
In the Guilin karst of southern China, caves develop with greater profusion in
crystalline limestones. They normally form nearly horizontal cavities with large collapse
chambers that distribute with varying numbers at diverse heights. The first three cave
levels, located at _+ 0; 7 to 15 and 25 to 35 m over the water level, occur all along the
Guilin region, although other cavity systems develop at 50, 90, and even 300 m. Lower
caves are recent, while the ones located at higher altitudes are older. This indicates that
towers have been growing at the same time the plain lowered, mainly by karstic corrosion.
It is believed that their evolution started in the upper Pliocene period. They present middle
Pleistocene hominoid remains in the 90 m cave (Gigantopithecus). Many data exist on
absolute dating, basically made by U/Th and C-14 techniques. Palaeomagnetic studies
indicate that sediments from one cave are at least 900,000 years of age (Sweeting, 1995).
Plains originate by limestone dissolution planation under alluvial sediments, ponds, or
lacustrine zones. Planation surfaces are controlled by phreatic level oscillations (Ford and
Williams, 1989). They are equivalent to the marginal or border plains of polje bottoms in
temperate regions. Following Thomas (1994), their evolution is quite similar to the one of
etchplains, where surface plain lowering is accompanied by tower growth.
Climatic Geomorphology
to grooves, which usually collapse, but the most common feature is the presence of caves
in the contact tower-plain, with increases of phreatic or vadose water that accelerates
limestone dissolution in this zone and as a consequence slopes become steeper. This zone
of basal undermining can be emphasized by fluvial erosion. If this activity decreases then
the angle of the basal slope segment declines (Gerstenhauer, 1960) and the tower degrades.
In the Guilin karst of southern China, caves develop with greater profusion in
crystalline limestones. They normally form nearly horizontal cavities with large collapse
chambers that distribute with varying numbers at diverse heights. The first three cave
levels, located at _+ 0; 7 to 15 and 25 to 35 m over the water level, occur all along the
Guilin region, although other cavity systems develop at 50, 90, and even 300 m. Lower
caves are recent, while the ones located at higher altitudes are older. This indicates that
towers have been growing at the same time the plain lowered, mainly by karstic corrosion.
It is believed that their evolution started in the upper Pliocene period. They present middle
Pleistocene hominoid remains in the 90 m cave (Gigantopithecus). Many data exist on
absolute dating, basically made by U/Th and C-14 techniques. Palaeomagnetic studies
indicate that sediments from one cave are at least 900,000 years of age (Sweeting, 1995).
Plains originate by limestone dissolution planation under alluvial sediments, ponds, or
lacustrine zones. Planation surfaces are controlled by phreatic level oscillations (Ford and
Williams, 1989). They are equivalent to the marginal or border plains of polje bottoms in
temperate regions. Following Thomas (1994), their evolution is quite similar to the one of
etchplains, where surface plain lowering is accompanied by tower growth.