First Half of Field Trip
The 22nd Annual Fall Field Frolic
August 18 - 21, 2004
Field Trip Leaders:
George Dunne, Dave Liggett, Doug Yule
Photos and text by Dave Liggett
Our first stop was at the entrance to the Academy Quarry northeast of Fresno. Dave Liggett spoke about the geology of the Academy pluton, the significance of the hornblende-bearing mafic rocks at the western margin of the Sierra Nevada batholith, and their intrusion along a boundary between the ophiolitic rocks to the west and the continental rocks to the east. He also gave a brief history of the Academy Quarry.
Day two started with a presentation by George Dunne on everything you wanted to know about the batholith (geography, glaciation, chemical trends across the batholith and within intrusive suites, pluton age progression across the batholith, structural trends, shear zones and their significance, uplift and tilting of the batholith, and the location and significance of the prebatholithic wall rocks).
We drove to Big Creek, then up a steep, narrow, winding road (with a "WATCH
FOR LOGGING TRUCKS" sign) where we stopped at an 8 Ma xenolith-bearing volcanic
Here we discuss how the volcanic pipe and others like it in this region have been used to
construct a model of the structure and composition of the lower crust and mantle
beneath the central Sierra. Xenoliths from younger volcanic pipes and
flows contain a different suite of rocks which suggests that the lower crust had
been removed during the intervening time. Keith Putirka (back row third
from left) CSUN alumnus and professor at CSU, Fresno joined us for the trip.
We drove past Huntington Lake to the Portal Power Station where Dave Liggett
presented a history of the development of hydroelectric power in the San Joaquin
River drainage. Through a series of lakes, dams, tunnels, and power
houses, the same water is used nine times to generate electricity and is said to
be the "hardest working water in the world"!
Some of the group enjoying the view at White Bark Vista on our lunch stop.
Go to the second half of the field trip
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