GEOLOGIA E ESPELEOCLIMA DE UMA GRUTA EM GRANITO NA SERRA DOS COCAIS, VALINHOS (SP)

Geology and climate speleology of a granite cave in Cocais Ridge, Valinhos (São Paulo, Brazil)

Abstract

Caves in igneous rocks represent about 2% of caves recorded in Brazil by 2020, a low value that also reflects the production of scientific knowledge around this topic. The Cordas Cave is a granitic cave located at the western escarpment of the Cocais Ridge in the city of Valinhos, São Paulo State, Brazil. It extends for approximately 400 meters, with a depth of 22 meters. The cave morphology is the result of accumulation of boulders in a drainage and include, in its eastern portion, a morphology of open fractures. Despite the small horizontal development, unevenness and volume, when compared to other types of caves, the Cordas Cave has its own speleoclimate, distinct from the external one. The temperature and humidity inside the cave show a cycle of diurnal variation, with reflections of regional climate variation. The origin of this cave is correlated with the geomorphological and climatic evolution of the Cocais Ridge. After the exposure of the ridge to percolation of water, which occurs mainly within the weakness planes, the formation of regolith and individualization of the blocks began. As the erosion rate increased, the fresh blocks were exposed and were accumulated along the slopes and valleys by accommodation and rolling.