A review of all available surface and subsurface data on Triassic and Lower Jurassic rocks in northeastern Arizona has revealed the following information. The Moenkopi Formation, the Chinle Formation, and the Glen Canyon Group of Triassic and Early Jurassic age are present throughout most of the study area. These units form a sequence of continental and transitional marine origin that shows notable vertical and lateral facies changes. The Moenkopi Formation thickening west and northwestward with a maximum thickness of 134 meters. The unit comprises sandstone and shale, and shows more shaley facies westward. The Chinle Formation shows minimum thickness to the north and thickens toward east and south with a maximum thickness toward west. This unit dominantly consists of sandy shale, but contains more sandstone westward and north westward. The unit contains some limestone in north and northern region. The Chinle Formation is overlain by the Glen Canyon Group, which in ascending order comprises the Wingate Sandstone, the Moenave Formation, the Kayenta Formation, and the Navajo Sandstone. The Wingate Sandstone shows its maximum thickness in the central and southcentral region of the study area and thins west and eastward. This unit mainly comprises sandstone, particularly in its upper part. The Moenave Formation displays its zero thickness, in the eastern region and shows its maximum thickness, 198 meters, in the west-central part. The unit mainly consist of sandstone. The Kayenta Formation attains its greatest thickness, 204 meters, in the southwestern part of the region and thins east and northward. This formation contains high percentages of sandstone. Within the area of this study, the Navajo Sandstone is the thickest formation in the Glen Canyon Group. This unit almost entirely consist of sandstone pinches out toward the south and east, and displays its maximum thickness, 300 meters, northward.