Charles A. Anderson Edwin H. McKee 1971 <p>During late Miocene (14.8 m.y.) to early Pliocene (10.1 m.y.) time, local latite and widespread basaltic flows accumulated with associated continental sedimentary deposits in north-central Arizona. Some of these rocks were displaced and tilted by normal faults, and new drainage, now occupied in part by basalt flows of late Pliocene age (average 5 m.y., maximum of 6 m.y.), was established at the southern margin of the Colorado Plateaus. The time of faulting and uplift of the Colorado Plateaus in this region is thus bracketed between about 10.1 and 6 m.y. ago.</p><p>Five analyzed basalts fall within the tholeiitic basalt field of the alkali-silica diagram and twenty are in the alkalic basalt field; in general, they are similar to other alkali-olivine basalts from the western United States.</p> application/pdf 10.1130/0016-7606(1971)82[2767:AACOTV]2.0.CO;2 en Geological Society of America Age and chemistry of tertiary volcanic rocks in north-central Arizona and relation of the rocks to the Colorado Plateaus article