Stratigraphy and diagenesis of Pleistocene eolian deposits in the northern coast of Puerto Rico.

摘要

The petrography, mineralogy of hand samples, and the morphology and trace elemental compositions of eolianite cements were studied at three sites along the north coast of Puerto Rico: Cueva del Indio and Punta Morrillos, in Arecibo, and Breñas in Dorado. Remnants of aragonite in the eolian deposit of Cueva del Indio suggest that the area has been subjected to lesser degrees of diagenesis than the other sites studied. At Punta Morrillos the deposits identified as paleosols, located 5 meters above sea level, suggest a reactivation surface. The morphology and geochemistry of the cements studied suggest that: (1) vadose cements (first stage) are not the best criteria to recognize ancient eolianites since they were altered early in the diagenetic sequence, (2) the best time frame for the deposition of the eolianites at Breñas seems to be after the beginning of the regression 120–132 ka proposed by Taggart (1992), and (3) a later rise of the relative sea level of up to 5 meters is suggested in Cueva del Indio Eolianite during the Holocene since the cements of the second stage are from marine phreatic environments or intertidal environments.