First Half of Field Trip
The 24th Annual Fall Field Frolic
August 30 - September 3, 2006
Field Trip Leaders:
Doug Yule, Jorge Vazquez, Elena Miranda, Dave Liggett,
Photos and text by Dave Liggett
After a long drive from CSUN we camped in the Virgin River Gorge. The next morning Dr. Yule presented a trip overview and described some of the boundary features between the Colorado Plateau and the Basin and Range physiographic provinces.
Our first stop was at Evanelle Pass on the Hurricane Valley Road. Dr. Yule spoke about the range front fault system, seismicity belts along the margins of the Great Basin, and the active north-south-trending normal faults of northwestern Arizona. Dr. Vazquez described the volcanic rocks of this region, cosmogenic age dating concepts, and noted the linear alignment of volcanic centers along the faults.
Our next stop was the Hurricane fault. It is one of the longest and most active late Cenozoic west-dipping normal faults in the structural transition zone between the Colorado Plateau and the Basin and Range.
We drove through the southeast corner of Zion National Park where we saw imposing cliffs and spectacular cross-bedding in the Jurassic Navajo Sandstone.
At Le Fevre Overlook we had a panoramic view of the Grand Staircase (Vermillion, White,
and Pink Cliffs), which represents a slice of geological time of approximately 200 Ma.
We camped at the North Rim of the Grand Canyon. In the morning we hiked to Bright Angle Point where the
views were spectacular. Dr. Yule and Dr. Vazquez described some of the important geological features found in the Canyon.
We crossed the Colorado River near Lee's Ferry and walked out on the Navajo Bridge.
The steep, ledgy, cliffs of Marble Canyon are composed of the Permian Kaibab and Toroweap Formations.
At Sunset Crater Michael Ort of N.A.U. described the local geology as well as a Hopi mythological account for the cause of the
eruption of Sunset Crater and how the Native Americans adapted to the eruption.
Sunset Crater is the youngest crater in the San Francisco volcanic field. It is an alkali-basalt cinder cone constructed from a series of ash falls that originated along a fissure eruption. Sunset Crater also produced lava flows. At the Bonita lava flow we looked at inflation features.
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