Map showing paleocurrent and clast-size data from the Devonian-Mississippian Endicott Group, northern Alaska

The Devonian-Mississippian Endicott Group (Tailleur and others, 1967) is an important geologic unit in the Brooks Range of northern Alaska. It reflects a major tectonic event in the middle and late Paleozoic history of the North American Cordillera. Tailleur and Brosge (1970) interpreted the Endicott as a clastic wedge derived from land to the north during the Late Devonian and from land to the northeast during Early Mississippian, when a shallow sea transgressed the area. In the north-central and eastern parts of the range, the Endicott is composed of three formations, in ascending order, the Upper Devonian Hunt Fork Shale and Kanayut Conglomerate and the Lower Mississippian Kayak Shale; in the western part of the range, the stratigraphic relations of these formations with formations in the Endicott is uncertain. Donovan systematically collected paleocurrent and clast-size data from the Endicott Group along the Brooks Range for Mobil Oil Corporation in 1967 and 1968. In recognition of the general interest in the information, Mobil has permitted its release. I.L Tailleur summarized the regional geologic information.