Paleoecological Significance of Cretaceous Bivalve Borings from Israel

Vertical, flask-shaped, densely packed bivalve borings occur on upper surfaces of Cretaceous limestone and dolostone beds. The lithified bedding surface was abraded during the process of boring, probably within the intertidal zone. These paleoenvironmental conclusions are supported by nearby conglomerates or mud-cracks at each of the bored surfaces. The occurrence of similar borings in Campanian chert may indicate the existence of a lithified, most probably calcareous surface prior to its being bored and partly abraded in the shallow marine environment, as well as its later silicification. Natural casts of borings of bivalves from the top of a Turonian limestone at an unconformity overlain by Santonian chalk are described and compared to the borings in the rock-surfaces.