NOTE:
1/25/2011 - The signs for Paid parking ($5) have been removed from
the western trailhead!
Parking available at the
western trailhead or at the
eastern trailhead, which lengthens your hike by 1/2
mile.
Happy Camp Canyon Regional Park, in the eastern Ventura County
city of Moorpark, offers visitors 12.5 miles of trails in a
3,000-acre wilderness area frequented by hikers, equestrian riders,
and mountain bikers. The open grasslands and deep forests are
abundant with wildflowers and wildlife including rabbits, bobcats
and golden eagles. Sections are very sandy and dogs are not allowed
into the nature preserve.
Fused shale is formed by the burning of petroleum underground in
the geological formation in which the petroleum occurs. This rock,
the late Miocene (17.5 to 6 million years ago) Modelo Formation, is
rich in organic matter. In fact, the Modelo Formation is similar in
age and depositional environment as the Monterey Formation that is
the source of the region's rich oil fields.
Fused shale is formed in a process called combustion
metamorphism. Whether from a lightning strike, spontaneous
combustion, or some other natural ignition source, the organic
material in this area somehow began to burn and change the
surrounding rock. Exhaust and steam moved upward from the fire
altering rock far above the subsurface fire. This movement of air
sucked in oxygen from the atmosphere inward through fractures in
the rock. References estimate that the temperature exceeded 1650
deg C, enough to melt the rock.
This changed the surrounding rock into ash, slag, and glass-like
material similar to obsidian that is sometimes called fused shale.
Depending on how hot the material gets, i.e., the degree of fusion,
colors may vary from yellow, orange, red or black. Layers of black
fused shale can be seen in the road cut. Additionally, during the
recrystallization, the rock may have acquired a magnetism that is
stronger than the surrounding rocks.
Fused shale was used by the local Native American Villages to
create sharp tools and trade with other villages. Its use may have
begun as long ago as 5000 years ago. Quimisac was the Chumash
village located in Happy Camp Canyon and likely controlled these
outcrops of fused shale. Initially, the exposures in
Grimes Canyon were likely used more since larger pieces could
be obtained from that area. As bow and arrow came into use, smaller
pieces could be used, and these outcrops became more useful.
The fused shale outcrops are adjacent to the fire road and
there is no need to leave the trail.
Logging requirements:
Send me a note with :
- The text "GC1BFCG QUIMISAC – Geo-Archeology" on the first
line
- The number of people in your group.
- Find a sample of the black fused shale and compare it to
obsidian (or glass if you haven't seen obsidian). Look at the
shapes it makes when it breaks.
- If you have a magnetic compass, see if it is affected by the
rocks in the area (post that in your log)
- Examine pieces of red rock in the area and report any unusual
characteristics. What other colors can you find?
The above information was compiled from the
following sources:
- Geology and Mineral Resources Study of Southern
Ventura County, California, 1973, California Division of Mines and
Geology Preliminary Report 14
- Richard J. Behl California State University,
Long Beach, Monterey Formation,
http://seis.natsci.csulb.edu/rbehl/Mont.htm
- Santa Barbara and Ventura Basins, Tectonics,
Structure, Sedimentation, Oilfields Along an East-West Transect, A.
G. Sylvester and G.C. Brown Editors, Coast Geological Society Field
Guide No. 64
- Burnt Oil Shale Deposits of Ventura County, CA.
The Ventura Gem & Mineral Society, Inc. (VGMS) Rockhound
Rambling February 2004.
http://www.vgms.org/bt/vgms0402.htm
- Mike Kuhn, 9/11/04, QUIMISAC,
http://simitrailblazers.com/articles/QUIMISAC.html
- Research Issues in San Diego Prehistory - Fused
Shale,
http://home.earthlink.net/~researchissues/spatial.fusedshale.htm
- THE CHUMASH AND HOW THEY LIVED,
http://www.simitrailblazers.com/articles/THE%20CHUMASH%20AND%20HOW%20THEY%20LIVED.html
- ANCIENT TRAILS,
http://simitrailblazers.com/articles/Ancient_Roads.html