Carbonate Platform Accretion by Cementation of Ribbons of Dune Ridge Sediments, Yucatan, Mexico: ABSTRACT

Abstract

The north coast of the Yucatan Peninsula, Mexico, consists of an almost continuous dune ridge backed by a swamp/estuary system. Conditions peculiar to a platform of almost pure carbonate rock result in delivery to the dune ridge of large quantities of fresh to brackish ground water saturated with respect to calcium carbonate. This ground water, which passes beneath the swamp/estuary system, arrives at the dune ridge charged with CO/sub 2/ and with a head higher than mean sea level. The result, over practically the entire north coast of the peninsula, is that CO/sub 2/ is released from ground water as it arrives at the dune ridge. Concomitantly, CaCO/sub 3/ becomes supersaturated and precipitates in pore spaces in the beach sand to produce a 300-km ribbon of impermeable rock between layers of unconsolidated carbonate sand of unstable mineralogy. This rock layer separates a surface lens of salt water about 3 m thick from the deeper lens of fresh water. Regional conditions require that, deeper still, lies a classic salt water intrusion. They submit that the system they report here may be a common, hitherto unrecognized feature important in the stabilization of large carbonate platforms. One interesting characteristic of this system ismore » that it should result in protected lenses of carbonate sand of unstable mineralogy, which can become lithified at a later time and in a different chemical and physical environment. They welcome suggestions of possible analogs in the geologic record.« less