Abstract

More than 20 trace fossil species occur in marine facies of the Cretaceous Star Point and Blackhawk formations in the Book Cliffs and Wasatch Plateau provinces of Utah. Major genera include Ancorichnus, Arenicolites, Aulichnites, Chondrites, Conichnus, Cylindrichnus, Medousichnus, Ophiomorpha, Palaeophycus, Planolites, Rosselia, Schaubcylindrichnus, Scolicia, Skolithos, Teichichnus, Teredolites, and Thalassinoides. Newly named taxa include Ancorichnus capronus, Medousichnus loculatus, and Rosselia chonoides.Most trace fossils occur in characteristic, albeit intergradational ichnofacies correlative with major lithofacies of regressive nearshore to offshore sequences. The latter include foreshore, foreshore–shoreface transition, shoreface, and offshore facies. Landward facies are typified by clean, well sorted, well stratified, sparsely burrowed sandstones. Seaward facies, except where interrupted by hummocky bedded sandstones, exhibit successively less pure, less well sorted and stratified, more intensely bioturbated, finer grained sandstones, siltstones, and mudstones.Characteristic ichnofacies and lithofacies in the Cretaceous of east-central Utah should provide potentially useful models for reconstruction of nearshore to offshore sequences elsewhere, especially in the Western Interior Region of North America.

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