ABSTRACT

The glauconitic and sandy limestone sequence, which in most places represents the Upper Cretaceous transgression throughout the High Calcareous Alps of the High Savoy, gives way in the Roc-de-Chere region to a 3- to 4-feet bed of conglomerate containing curiously shaped pebbles of fine-grained limestone scattered in a glauconitic matrix.

Three distinct limestone types may be distinguished in the conglomerate on the basis of shape, dimension, and induced flow structures (from base to top): (1) contorted streaks, (2) larger irregular pebbles with highly deformed matrix inclusions, and (3) still larger subrectangular chunks with slightly deformed matrix inclusions.

Well-developed flow structures are shown by the orientation of quartz grains and by the arrangement of deformed Globotruncana tests in both the pebbles and the matrix.

A tentative explanation might suggest a mixed sedimentation in which beds of plastic calcareous muds and glauconitic sands were alternately deposited. Reworking phenomena intensively stretched and mixed the freshly deposited beds. However, intensity of deformation decreases upward as depth of water increased during transgression.

Such a sediment may be classified as a special type of intraformational conglomerate formed under wave action when beds were still plastic.