Paleotopographic Controls from Geometries and Facies Distribution in Oolite-Microbialite-Reef Sequences, Upper Miocene, SE Spain

Christopher J. Lipinski, Robert H. Goldstein, and Evan Franseen
Geology, University of Kansas, Lawrence, KS

Four sequences in the Terminal Carbonate Complex, a distinctive upper Miocene unit, were examined at two locations in SE Spain: La Molata (Molata), at an intermediate substrate elevation (160 - 230 m); and Ricardillo-Rellana (Rellana), which reached higher elevations (150 - 270 m). At Molata, sequences typically drape and partially onlap 25-30 m of paleotopography over 0.6 km. At Rellana, more complex onlapping, progradational, and downstepping geometries span as much as 75 m of paleotopography over 2.3 km.

At Molata, sequence 1 (S1) consists of basal microbial buildups that transitions vertically and laterally through cross-bedded oolite to planar bedded oolite; whereas at Rellana, S1 exhibits massive oolite overlain by cross-bedded and planar-bedded oolite throughout. At Molata, S2 contains microbial buildups overlain by cross-bedded and planar-bedded oolite; whereas at Rellana, S2 contains microbial buildups at low elevations and cross-bedded gastropod grainstone overlain by cross-bedded and planar-bedded oolite at high elevations. At Molata, S3 consists of massive oolite overlain by cross-bedded and planar-bedded oolite; whereas at Rellana, S3 consists of massive oolite overlain by coralgal patch reefs at low elevations, and cross-bedded oolite overlain by planar-bedded oolite and cross-bedded gastropod grainstone at high elevations. At Molata, S4 contains basal microbial buildups that become interbedded with overlying cross-bedded oolite and cross-bedded gastropod grainstone; whereas at Rellana, S4 contains microbial buildups overlain by cross-bedded oolite.

These findings indicate that minor substrate paleotopography differences have a major effect on geometry and distribution of reservoir facies, such as oolite, microbialite, bioclastic facies, and coralgal reefs.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas