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ABSTRACT

In the French Southern Alps, alternating pelagic limestones and marls of Hauterivian age contain a dense network of burrows. Differences between the original and preserved forms of the burrows provide evidence of sediment deformation. (a) Total compaction, from early dewatering of sediment to deep burial compression, caused flattening of burrows parallel to bedding. Its relation to carbonate is measured, and a tentative mathematical relation is proposed, (b) Synsedimentary slumping is shown by total disordering of the bioturbation network in the displaced layers. (c) A more characterized deformation is occasionally visible only on the upper part of some limestone beds. The sliding is indicated by the dip of burrows in the same direction as the flow. (d) Similar embryonic flows occur in the middle of rare limestone beds. It is thus suggested that this can account for some of the double beds that occur in pelagic alternations of calcareous and marly beds.