A COMPREHENSIVE ICHNOTAXONOMIC TREATMENT OF THE DAKOTA GROUP, FRONT RANGE, COLORADO

The purpose of this ichnotaxonomic treatment is to create a comprehensive understanding of the trace fossils known from the Dakota Group found in Colorado, to interpret sedimentary environments and depositional history. The Dakota Group is found in Colorado, Kansas, Iowa, Nebraska, New Mexico, and Utah, and was deposited during the Albian–Cenomanian. Strata within the Dakota Group contain oil and gas reservoirs whose geometries and distributions are aided by trace fossil analysis, which particularly strengthens the reconstruction of paleoenvironments and paleoecology of these dinosaur-bearing sedimentary successions. The objective is to produce a systemic, reappraisal into the ichnotaxonomic treatment of the Dakota Group along the Colorado Front Range to provide revisions to the established paleoenvironments and paleoecology. The Dakota Group in Colorado is subdivided into, the Lytle, Plainview, Glencairn (Cañon City), Skull Creek Shale (Morrison, Fort Collins) and Muddy formations. The Lytle Formation (Fm) represents fluvial environments and contains a few trace fossils, such as Naktodemasis along with poorly preserved dinosaur tracks. The Plainview Fm was deposited in a nearshore environment and contains Archaneonassa, Asthenopodichnium, Chondrites, Cochlichnus, Crossopodia, Lockeia, Nereites, Planolites, Provirgularia, Scolicia, Skolithos, and Taenidium, along with Teredolites borings in wood fragments. Tracks of ankylosaurid, theropod dinosaurs, and swimming reptiles are also present. The Glencairn Fm was deposited in deltaic or estuary environments and contains Cylindrichnus, Margarictichnus, Ophiomorpha, Skolithos, Teichichnus, Thalassinoides, and Zoophycos. The Skull Creek Shale was deposited in a deltaic environment and contains Arenicolites, Asterosoma, Diplocraterion, Macronichnus, Palaeophycus, Rhizocorallium, Rosselia, Schaubcylindrichnus, Skolithos, Taenidium, Teichichnus, and Zoophycos. The Muddy Fm was deposited along a shoreface and deltaic environment and contains Arenicolites, Asthenopodichnium, Aulichnites, Dendrothichnium, Diplocraterion, Macronichnus, Ophiomorpha, Pholeus, Planolites, Rhizocorallium, Rosselia, Teichichnus, and Thalassinoides. Also present are crocodylian, ornithopod, and theropod tracks.