Three-Dimensional Modeling of Dramatic Changes in Depositional Geometries of the Late Triassic Carbonate Platforms of the Southern Alps (Italy).

Giovanni Gattolin, Marco Franceschi, Nereo Preto, and Anna Breda

Depositional geometries can be decisive in understanding the genesis of geological bodies because they are tightly linked with the processes in play during sedimentation.

Vertical and hardly accessible walls of mountain environments make the field tracing of depositional geometries particularly challenging, but provide spectacular outcrop conditions. Line-drawing on high resolution pictures can help (e.g. for clinoforms), but its use for quantification is hampered by perspective deformation.

3D modeling allows to retrieve the true spatial characters of sedimentary bodies on outcrops.

We considered three upper Triassic outcrops from North-Eastern Italy where dramatic modifications in depositional geometries appear to follow sharp changes in carbonate production style: a switch from steep clinoforms of high-relief carbonate platforms to low-angle ramps and then back to high-angle slope clinoforms is observed.

A first example (Tofana di Rozes, Dolomites) exposes a platform-to-basin transect where a turnover to low-angle ramp geometries is observable. The second example (Dibona hut, Dolomites) consists of a clinostratified carbonate body within the carbonate ramp system. In the third outcrop (Portella, Julian Alps) the coming back to high-relief platform geometry is testified.

The geometry of the carbonate body at Dibona (~15000 sqm) was acquired with terrestrial LiDAR, while for Tofana (~250000 sqm) and Portella (~500000 sqm) photogrammetric techniques were applied.

At the onset of the low-angle ramp system, a phase of complex intermediate sedimentation in which carbonate mounds and loose skeletal carbonates coexisted and interacted, implying a progressive but non-abrupt change of carbonate production style. The skeletal ramp depositional system was transient, as demonstrated by the subsequent onset of a new high-relief carbonate platform (Portella).

The presented examples may represent a field analogue for upper Triassic oil reservoirs of the Mediterranean region, and the succession of depositional geometries developed during this time represents a playground to refine 3D modeling methods for sedimentary bodies.

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