Integration of a large tropical cave network in brecciated limestone: Caves Branch, Belize
Published:January 01, 2006
Thomas E. Miller, 2006. "Integration of a large tropical cave network in brecciated limestone: Caves Branch, Belize", Perspectives on Karst Geomorphology, Hydrology, and Geochemistry - A Tribute Volume to Derek C. Ford and William B. White, Russell S. Harmon, Carol M. Wicks
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The Caves Branch Cave System is unusual because it developed in highly brecciated, nonbedded Cretaceous limestone, it is one of the largest cave complexes in the tropics, and it has a hydrologic architecture that mimics constant hydrochemical “flushing events.” Its complex growth has assembled a multilevel 31 km network, which is the largest of 45 km of caves in the Caves Branch Valley of Belize that have been surveyed following exploration and cave diving since the late 1960s.
The valley is a polje entrenched into a mature cockpit holokarst of 200 m relief. After initiation of high, small, isolated phreatic caves, perhaps 200,000 yr of development progressed vertically downward from massive phreatic chambers (one exceeds 300 m in length) to the present active conduit, which has both deep phreatic loops and low water-table gradients. The primary conduit of the Caves Branch Cave System exceeds 15 km in length and parallels the polje on the east. A series of hydraulically restricted cave channels pirate allogenic river water from the polje into the conduit, to mix with high-solute calcite-saturated discharge from the overlying karst. The discharge of sequential wet season storms overwhelms the river waters in the conduit, producing a rise in solute concentration, which then declines with each karst storm flow recession. The pirate river channels and holokarst inputs join from opposite sides of the same conduit at similar elevations, yet have distinctive morphologies. In the absence of bedding, these may be best explained by differences in clastic sediment load, which are more pronounced than differences in chemistry.