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ABSTRACT: Gravity-Driven Processes: Control on Margin Architecture and Slope Evolution in a Cretaceous Carbonate Platform (Montagna della Maiella, Italy)

Morsilli, Michele1, Giovanni Rusciadelli2, Giada Vichi2, and Alfonso Bosellini1
(1) Università di Ferrara, 44100 Ferrara, Italy 
(2) Università di Chieti, 66013 Chieti Scalo, Italy

Large-scale gravity-driven structures (convex-bankward embayments or slope truncations) have been largely recognized along discrete portions of many modern carbonate platform margins, whereas few examples have been reported in ancient counterparts. Triggering mechanisms, are mainly seen as tectonic activity, sea-level changes, sediment overload, etc.

Spectacular seismic-scale outcrops in the Maiella Mt. allow to observe directly an average 1000 m high Cretaceous escarpment, abruptly separating shallow-water facies from slope to basin ones. In plain view, three main km-scale indentations have been recognized. They are similar in shape and size to those observed in modern scalloped platform margins. In section view, along the large indentations, the geometry of escarpment have an exponential profile which changes downslope from high angle (~60°) to sub-horizontal. Along ridges, between different scallops, the escarpment profile is more regular, with average angles of 35° and locally steeper (> 45°).

The escarpment is the result of different gravity-driven processes occurred during different stages. The larger indentations formed as the result of the Albian platform margin collapses, exposing Lower Cretaceous inner platform facies directly to open marine conditions and exporting related products (megabreccias) many kilometres basinward. The inherited physiography controlled the spatial distribution of Upper Cretaceous marginal facies and influenced the stratal stacking patterns in both platform and slope-basin settings. A by-pass margin, defined by an overall aggrading stacking pattern and re-shaped by smaller scale collapses, developed up to the Campanian. At this time, the basin was almost completely filled and the platform started to prograde.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia