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Towards a 3D model of the Calcari Grigi Carbonate Platform (Early Jurassic, Southern Alps, Italy)

Marco Franceschi, Matteo Massironi, Michele Zandonati, and Vincenzo Picotti

3D modeling represents a standard procedure in the characterization of large-scale buried geologic bodies. While seismics provides important information about geometries at depth, facies characterization is often less capillary. That is one of the reasons for which outcrop analogues turn out useful, although they normally do not match the scale of subsurface bodies.

We present preliminary results in the 3D modeling of the Early Jurassic Calcari Grigi carbonate platform. The platform (size ~100km x 100km, up to 400m thick) consists of several subenvironments (tidal flats, deep lagoons, oolitic shoals), now exhumed in the Southern Alps (Italy), a poorly deformed portion of the mesozoic passive margin of Adria. Despite some alpine faulting and folding, lateral relationships between Jurassic units are still preserved.

During Early Jurassic, the platform was affected by synsedimentary tectonics, testified by exposed structures, controlling sharp variations in the thickness of its units. Excellent outcrop continuity, extensive geological mapping and previous studies provide a great wealth of field data that give the opportunity to produce a 3D model of a seismicscale carbonate platform. Data were collected in a GIS database and were fed into geomodeling software.

Main stratigraphic horizons and geometries of the sedimentary prisms were modeled and lateral continuity of extensional faults estimated. This permits to have a synthesis-picture of how synsedimentary tectonics governed the depositional processes. Spatial variability of thickness values collected in various localities was studied with geostatistics. This helped to highlight main Jurassic faults and revealed an extensive orthorhombic fault-network. The 3D model can now be populated with facies and other sedimentological and petrophysical parameters to evaluate the influence of tectonics on the depositional and diagenetic environments.

The model of a carbonate platform of this size potentially represents a useful analogue for carbonate reservoirs and could help the understanding of similar buried sedimentary bodies.

AAPG Search and Discovery Article #90161©2013 AAPG European Regional Conference, Barcelona, Spain, 8-10 April 2013