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G. Shanmugam1, R.B. Bloch2, R.J. Moiola2
(1) Mobil Technology Company, P.O. Box 650232, Dallas, TX
(2) Mobil Technology Company, P.O. Box 650232, Dallas, Texas 75265, TX

Abstract: Complex deep-water origin of the Annot Sandstone (Eocene-Oligocene), Peira Cava, Southeastern France

The Annot Sandstone is composed of alternating sandstone and mudstone units. Although many of the sandstone units are amalgamated and can be compared with the Bouma Sequence and its divisions, detailed sedimentologic logging of these units reveals a much more complex internal organization, suggesting possible different origin. Observations and related preliminary interpretations are the following: (1) inverse grading (5 cm to 2 m thick) (flow strength, hindered settling, and buoyancy) at the base of normally graded sandstone, (2) simple normal grading (Newtonian flows), (3) complicated "normal grading" with floating quartz granules, floating mudstone clasts (e.g., 90 cm long and 55 cm wide), and floating mudstone balls armoured with quartz granules of 3-4 mm in diameter (flow strength, hindered settling, and buoyancy), (4) complicated "normal grading" with a pocket of gravels (plug flow or scour and fill), (5) random, imbricated, and planar clast fabric (plug flow, laminar flow, and water escape), (6) lenticular layers with coarser grains (flow strength?, turbulent flow?, laminar flow?), (7) sudden drop in grain size (sudden decrease in flow velocity), (8) parallel and ripple lamination (traction deposition), (9) alternating parallel-ripple-parallel-ripple lamination (pulsating flows), and (10) double mud layers, mica or mud-draped ripples, and sigmoidal cross bedding (steady and uniform bottom currents? deep tidal currents?).

In spite of this variability, we recognize an idealized fining-upward vertical succession. We suggest that the succession represents a single pulsating, waning event that reflects flow transformation between plastic and Newtonian flow.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana