4/5/2023 0 Comments Swell holbrook az![]() ![]() A 25 to 67 ft thick unit called the tawny beds, formerly mapped as part of the Moenkopi, are removed from Moenkopi and reassigned to the upper unit of the Franson Member of the Park City Formation. Triassic Moenkopi-Permian Park City contact modified on the south flank of the Uinta Mountains from Ashley Creek, Uintah Co, UT in the Uinta basin east to Red Rock Canyon, Moffat Co, CO in the Greater Green River basin. Source: US geologic names lexicon (USGS Bull. Named from Moenkopi Wash, Grand Canyon, AZ. Recognized in Arizona, southern Utah, and southeastern Nevada. ![]() 1413-1448, 1929.) This is present approved definition of Moenkopi formation. At places in Arizona (Grand Canyon, Lees Ferry, Red Canyon, Little Colorado River, etc.) and Utah (Circle Cliffs, San Rafael Swell, etc.) the Moenkopi rests on Kaibab limestone. ![]() At Fort Defiance, Arizona, some red beds of the Cutler separate the light-colored De Chelly sandstone from the unconformably overlying Moenkopi, which is, in turn, unconformably overlain by Shinarump conglomerate. ![]() At De Chelly Canyon, Arizona, it is top member of Cutler formation (Permian), and is unconformably overlain by Moenkopi formation (Triassic). But true De Chelly sandstone is now known to be of Permian age, to be = uppermost part of Coconino sandstone, and to belong to Cutler formation. In other reports De Chelly sandstone was placed in lower part of Moenkopi. In some subsequent reports Moenkopi formation was defined as underlying De Chelly sandstone. ![]()
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