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| Aspen grove in autumn color and boulders of Baldhills Tuff of the Isom Formation (deposited as part of the Markagunt Megabreccia of Miocene age) near the Alpine Pond parking area in Cedar Breaks National Monument. The Markagunt Megabreccia includes both sedimentary and volcanic deposits, such as these sheeted lava rocks that locally forms a caprock along the top of the Cedar Breaks. The volcanic rock formed in Late Miocene time, about 11 to 9 million years ago as part of a greater trend of regional volcanism that began in the Great Basin region of southern Nevada starting about 15 million years ago, and follow a trend to the northeast ending in volcanism in central Utah about 5 million years ago (Nelson and Tingey, 1997; Fillmore, 2000). |
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