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Miocene Transitional Carbonates: Facies, Stratigraphic Architecture, and Early
Diagenesis of a Fault-Block Carbonate Platform in Sardinia (Central
Christian Betzler1, Maria Mutti2, Merle-Friederike Benisek1,
Gabriela Marcano2, and Sebastian Lindhorst1
Search and Discovery Article #50085 (2008)
July 10, 2008
*Adapted from oral presentation at AAPG Annual Convention, San Antonio, Texas,
of Geology and Paleontology, University Hamburg, Hamburg, Germany ([email protected])
of Geosciences, University Potsdam,
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 27Â°. 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.
A. Transitional carbonates with a turnover from a ramp to
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.
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,
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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