Bulletin of the National Speleological Society - ISSN 0146-9517
Volume 30 Number 3: 75-86 - July 1968

A publication of the National Speleological Society

The Karst Features of Northern Puerto Rico
Watson H. Monroe

Abstract

Topographic features of the west-trending outcrop belt of limestone of middle Tertiary age in northern Puerto Rico are very good examples of karst development under humid tropical conditions. Specific karst features seem to correlate with lithologic characteristics; hence, they coincide approximately with the outcrop belts of stratigraphic units. Cockpit karst has formed only in areas underlain by pure massive phases of the Lares Limestone; mogote karst is restricted to the very pure massive Aymamón Limestone at places where a surficial cover of sand and sandy clay is present between isolated hills of limestone; and ramparts line the cliffs along many rivers and at the top of limestone sea cliff. Zanjones form in bedded phases of the Lares Limestone that are less pure than the massive varieties. Caverns and natural bridges are most common in formations of alternating hard and soft layers of limestone, especially in the Lares and Aguada Limestones. Deep sinkholes, some deeper than 200 feet, form only in formations characterized by alternating beds of hard and soft limestone, especially in the Aguada and the lower part of the Aymamón Limestone. Solution in depression features is augmented by the presence of a soil cover; reprecipitation of calcium carbonate from solution has indurated the surface of exposed limestone.

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