--> Deepwater Channel Bypass and Backfilling Processes from the Eocene Ainsa Basin, South-Central Pyrenees, Spain, by Christian Betzler, Maria Mutti, Merle-Friederike Benisek, Gabriela Marcano, and Sebastian Lindhorst, #50085 (2008)

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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

 

Abstract

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.

 

 

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Selected Figures

 
Figure 1 Transitional characteristics between rimmed platform and ramp



Figure 2 Geological setting: central Mediterranean Sea
Figure 3 Geologic map of study area


Figure 4

Platform geometry and stratigraphy of platform slope, platform margin, and inner platform  

Figure 5

Platform geometry, with details of sequences.

 

Figure 5

Paragenetic sequence.

Conclusions

A. Transitional carbonates with a turnover from a ramp to steep-flanked platform.

B. Turnover goes along with a change of the carbonate factories from warm-temperate to tropical.

C. Platform edge lies not at sea level, but in a water depth of around 40 m; platform-interior reefs occur at 20 m.

D. 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.

E. Further example for the close relation between carbonate factory and depositional geometries.

References

Bosellini, F.R., and C. Perrin, 2008, Estimating sea-surface paleotemperatures from shallow-water carbonates: the example of Mediterranean Oligocene-Miocene corals: Geophysical Research Abstracts, v. 10, EGU2008-A-03328.

 Schlager, W., 2005, Carbonate sedimentology and sequence stratigraphy: SEPM Concepts in Sedimentology and Paleontology, No. 8, p. 200.

Thomas, B., and M. Gennesseaux, 1986, A two stage rifting in the basins of the Corsica-Sardinia Straits: Marine Geology, v. 72/3-4, p. 255-239.

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