Karst Frontiers Gary 141 Karst WatersInstitute SpecialPublication 7 UNDERSTANDING ZACATON: EXPLORATION AND INITIAL INTERPRET A TION OF THE WORLDS DEEPEST KNOWN PHREATIC SINKHOLE AND RELATED KARST FEA TURES SOUTHERN T AMA ULIP AS, MEXICO Marcus Gary The University of Texasat Austin/ United StatesGeological Survey 8027 ExchangeDrive Austin, TX 78754
[email protected] A system of water-filled sinkholes (known as cenotes) this extreme karst system have taken place, and it has only exists in southern Tamaulipas, Mexico (Figure 1), and is been limited work within the past two years that theories the result of a unique combination of speleogenetic factors. relating to the speleogenesishave been formed. Microbial This system is composed of 18 different karst features that interaction seems likely to affect karstification processes, are on or near a large cattle ranch known as Rancho La and significant travertine structures appear to have a direct Azufrosa. Zacat6n, the deepest cenote in this system has influence on the hydraulic connectivity between the bodies been measured to over 350 meters deep, (Figure 1) and is of water. Years of future research are being planned to the site of the world-record SCUBA dive (284 meters) by document the extent of karstification in this deep Jim Bowden in 1994 (Gilliam, 1994). This makes it the hydrothermal system and interpret the geological history deepest known water-filled pit that has been explored by that has develope~ such an impressive example of humans in the world. No previous scientific studies of hypogenetic karst. Figure 1: Generalized cross section of the cenotes of Rancho La Azufrosa.