Geologic and hydrologic controls on karst and cave development in Belize

0.1`Nearly 3000 km2 of Belize display well-developed karst that occurs dominantly on Cretaceous lime-stones distributed on the periphery of the Maya Mountains. Other exposed carbonates in Belize, sharing the same tropical climate and heavy rainfall, are not karsted. The Mayas represent a horst structure raised by movement of the Caribbean-North American plate boundary. In excess of 150 km of large cave passage has been mapped, often exhibiting multi-level development likely related to this regional tecton-ic motion. Passages are dominantly trunk conduits solutionally bored through the lower-lying limestones by integrated allogenic streams from the Mayas. Other large, independent caves and collapse chambers are also known. Limited U-series dating of speleothem gives minimum ages of 176 KaBP for cave devel-opment. The karst surfaces are dominated by disaggregated remnants of previous fluvial networks, but also contain spectacular collapse dolines. The karst aquifers appear to be solutionally “open ” systems of relatively high porosity (>1%). Boosting of carbon dioxide levels above surface soil CO2 occurs with-in aquifers, perhaps due to decay of washed-in vegetation. Mean solutional erosion is estimated at 0.10-0.13 m/Ka for these karsts. Belize consists of the ancient, escarpment-bounded Maya Mountains, which rise to 1,100 m and are encircled by lowe