Rhythmic Bedding and Shell Bed Formation in the Upper Jurassic of East Greenland

Abstract

In the Middle Volgian of Milne Land, shelf sediments deposited well below wave base exhibit rhythmic alternations of shelly sandstones and largely unfossiliferous, uncemented sandy shales. They reflect a primary distribution pattern of the fauna which was only slightly distorted by diagenetic processes.

This primary distribution pattern is due largely to differences in the sedimentation rate, shell beds forming during periods of reduced sedimentation or omission. Shell beds are either autochthonous accumulations or else parautochthonous. The latter type were built up by repeated in-situ reworking and winnowing, caused by events such as storms which periodically disturbed the sea floor.