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Miocene Transitional Carbonates: Facies, Stratigraphic Architecture, and Early Diagenesis of a Fault-Block Carbonate Platform in Sardinia (Central Mediterranean Sea)*

By

Christian Betzler¹, Maria Mutti², Merle-Friederike Benisek¹, Gabriela Marcano², and Sebastian Lindhorst¹

Search and Discovery Article #50085 (2008)

Posted July 10, 2008

*Adapted from oral presentation at AAPG Annual Convention, San Antonio, Texas, April 20-23

¹Institute of Geology and Paleontology, University Hamburg, Hamburg, Germany ([email protected])

²Institut of Geosciences, University Potsdam, Potsdam, Germany

Transitional carbonates present characteristics in between classic photozoan and heterozoan carbonates. Models that represent these systems are poorly developed. A sedimentological, stratigraphical, and early diagenetic model for a Miocene (Burdigalian) carbonate platform located on a fault-bound topographic high in Sardinia is presented. The setting offers outstanding exposures that allow LIDAR and 3D geometrical reconstructions. The platform contains two depositional sequences separated by a major erosional unconformity and several high frequency sequences reflecting the occurrence of higher-order base-level fluctuations. The platform evolves from a ramp to a steep-flanked platform. The geometrical turnover goes along with a change of the carbonate factories from warm-temperate to tropical. The warm-temperate ramp of the lower sequence contains small patch reefs and beaches, longshore bars and outer ramp bioclastic, and red algal packstones to rudstones. In the lower part of the second sequence, a belt of submarine dunes separated platform-interior from deeper water bioclastic deposits. Dunes were locally stabilized by coralline algal bindstones. In the upper part of this sequence, the depositional system consisted of an extensive reef flat with a marked slope break formed by coralline algal bindstones and rhodolithic clinoforms beds dipping up to 27°. Steepening of the depositional relief of the carbonate platform is gradual and linked to (1) the inception of coralline algal bindstones and (2) increasing amounts of early diagenetic cementation. This study presents a further example for the close relation between carbonate factory and depositional geometries.