Geology Reference
In-Depth Information
(a)
(b)
(c)
Figure 10.14.
(a) Different parts of the speleothem with examples of its different facies. (Drawing of A.
Grandal d'Anglade). (b) Detail of porous matrix of clastic or oolitic opal-A grains. (c) Surficial
prismatic cluster of gypsum crystals.
appearing as a radial association of crystals with planar development giving rise to a typical cauli-
flower morphology. The first known mention of speleothems in granites corresponds to
Caldcleugh (1829) who reported silica speleothems from an overhang in a granite-gneiss dome
in the Rio de Janeiro area, Brazil, but speleothems are reasonably commonplace having been
reported from granite outcrops in Spain and Portugal, in the Black Forest of southern Germany, in
Brittany, in Madagascar, in U.S.A. and Córdoba and Anillaco (República Argentina); in quartzites
and sandstones having been reported in the Hoggar Mountains of the central Sahara, in Roraima
Plateau of Venezuela, in the Sydney Basin, New South Wales and in Litchfield National Park, near
Darwin, Northern Territory.
