--> ABSTRACT: Sedimentation Versus Submarine Erosion: The Upper Cretaceous Carbonate Slope of Gran Sasso d'Italia, Central Apennines, Italy, by Jan-Henk Van Konijnenburg, Maria Mutti, Daniel Bernoulli; #91020 (1995).

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Sedimentation Versus Submarine Erosion: The Upper Cretaceous Carbonate Slope of Gran Sasso d'Italia, Central Apennines, Italy

Jan-Henk Van Konijnenburg, Maria Mutti, Daniel Bernoulli

Carbonate slopes are key areas in correlating shelf and basinal sediments, and the processes controlling their facies distribution in space and time need to be better understood. The carbonate deposits of the Gran Sasso d'Italia represent an ancient base of slope sequence that separates the Maiella and Lazio Abruzzo platforms to the South from the Marche basin to the North. Integration of sedimentologic, litho- and biostratigraphic data from the upper Aptian to lower Campanian carbonate deposits reveals how sedimentation competes with submarine erosion.

Facies types on the slope include: (1) breccias and mega-breccias, with a large variety in platform- and slope-derived clasts as well as skeletal fragments; (2) turbidite beds, with mainly skeletal fragments and minor amounts of small clasts; and (3) pelagic sediments, formed by foraminiferal lime mudstones and wackestones, and small (>= 1 cm) contourite layers. The contour currents rework previously deposited planktonic foraminifera and turbidites.

The depositional geometries of (mega)breccia and turbidite beds are exposed in kilometer scale outcrops and show dominantly channelized bedforms and erosion of underlying strata. Mega-breccia beds have a limited areal extent and can not be correlated between sections. Facies changes occur not only downslope, but also along strike. This base of slope section has many internal gaps, as identified by biostratigraphic data, and has a reduced thickness even compared to the pelagic succession of the Marche basin.

The Gran Sasso area illustrates how repeated submarine erosion on a carbonate slope results in lateral and vertical variations in thickness and distribution of depositional facies. Since slope deposits represent a superimposed series of erosional and depositional processes, understanding the timing of events recorded in slope deposits within a sequence stratigraphic framework remains difficult, and requires careful consideration of different parameters.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995