Michelle Stoklosa¹, J.A. Toni Simo²
(1) Univ. Wisconsin, Madison, WI
(2) University of Wisconsin, Madison, WI

Abstract: Paleoclimatic and eustatic controls on Oligocene shallow-water environments, SE Spain

The Oligocene was a time of major global climatic and eustatic changes, as revealed by both land and deep-ocean studies. Little work, however, has demonstrated the effect of these changes in shallow-water settings. Carbonate deposition was occurring on the rapidly subsiding southern margin of Iberia at this time, before the advance of Miocene thrust sheets caused drowning of the platform. The result was a thick (~300 m) accumulation of shallow-water carbonates exposed in the Costa Blanca region of SE Spain, providing a nearly complete record of Oligocene climatic and eustatic changes. Two sequences have been recognized. The lower sequence contains emergent (bearing intraclasts and blackened grains) cycles (3-10 m thick) of shallow, semi-restricted, often well-sorted facies (miliolid-dominated). Time equivalent basinal strata contain fine and coarse-grained turbidite beds. The upper sequence is composed of thicker (10-15 m), non-exposure cycles of open marine poorly-sorted facies composed of red algae and large benthic foraminifera. This upper sequence exhibits overall deepening and a lack of coarse-grained resedimentation in the basin. Preliminary paleontological data suggest that the two sequences correspond to the Lower and Upper Oligocene. The temporal facies and faunal reorganization recognized from this succession, such as the decrease in cyclicity and platform shedding, and the change from semi-restricted fauna to open marine fauna more tolerant of cooler water, agree with the widely-held view that the world changed from a greenhouse climate in the Eocene to a cooler, drier climate in the Oligocene, with the characteristic longer-term sedimentation cycles of an icehouse climate.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana