Edwin D. McKee
1954
<p><span>The </span>Moenkopi<span> </span>formation<span> of </span>Triassic<span> </span>age<span> is composed of a series of deposits that form a wedge thinning eastward from a maximum of about 2000 feet in western Utah and southern Nevada to the vanishing point along an irregular margin in western Colorado, northeastern Arizona, and western New Mexico. Partly marine and partly continental in the thick western sections, it is entirely continental in the east. Invertebrate faunas indicate that deposition began either during or preceding the middle of the Early </span>Triassic<span> (Meekoceras zone) and continued into late Early </span>Triassic<span> (Tirolites zone) and probably into Medial </span>Triassic<span> time. Vertebrate faunas also indicate an Early </span>Triassic<span> and probably, in part, a Medial </span>Triassic<span> </span>age<span>. Studies of the deposits indicate three major transgressions and three regressions across southern Utah and northern Arizona. Analysis of sedimentary rock types and original structures in them suggests a complex mixture of environments involved in the development of the </span>formation<span>: stream beds, lagoons, playas, flood plains or tidal flats, shallow sea floors, and others. Some types are clear cut and readily demonstrated; others are open to question. Evidence from flora, fauna, and sediments indicates a semiarid to arid climate. Except for uplift in the Uncompahgre region of Colorado indicated by conglomeratic beds in the </span>Moenkopi<span> near by, the entire region probably remained very low and flat during </span>Moenkopi<span> deposition.</span></p>
application/pdf
10.1130/MEM61-p1
en
Geological Society of America
Stratigraphy and history of the Moenkopi formation of Triassic age
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