I think prior fossil hunters and the Orange
County Museum of Natural History already picked up the best
examples. The museum has recovered a dolphin and psudo walrus.
I am not sure if they still have them on display, and don’t
expect much of the museum as it is housed in a couple of
mobile home trailers located just south of Alicia Parkway and
Aliso Creek Road.
At this location I was able to find a number of poorly preserved
fragments in some of the larger boulders and only one good specimen
(N 33 35.186 W117 42.730). The good specimen is off the trail along
a rock outcrop. I expect the better specimens are still buried and
have been found during construction.
Pecten reef is a localized limestone deposit within the Monterey
formation. Tropical marine and terrestrial fossils from
approximately 15 million years ago have been found throughout it.
Outcrops of Pecten Reef can be found approximately 6 miles north in
Lake Forest, through Wood Canyon in Laguna Hills, and near the
Santa Ana Freeway at Alica Parkway. In some places Pecten Reef is 2
miles wide and about 600 feet thick.
The easiest fossils to identify at this location are of pecten
shells, a type of mollusk that is found in warm ocean waters.
Pecten shells look like the Shell Oil symbol. Other fossils that
have been found include tube worms, other shell fish, and other
marine species. Elsewhere fossils of whales, dolphins,
hippopotamuses, crocodiles, and horses have been found.
The types of fossils provide a clue about the environment of the
area when the fossils were deposited. About 7 million years ago,
tectonic forces began thrusting up the Santa Ana Mountains, turning
the area first into a shallow sea, then a swamp then dry land. The
species found are typically found in warm water and tropical
environments. This suggest at the surrounding area was once a warm
and wetter area between 7 and 15 million years ago.
Logging requirements:
Send me a note with :
- The text "GCPAFB Pecten Reef - Aliso Viejo" on the first
line
- The number of people in your group.
- Post a picture of the best fossil you
can safely find. Measure the diameter of the fossil and include it
in your post. If it is at location different than the above
coordinates include it with the picture and/or log.
Please begin your e-mail with the name of the earthcache and be
sure your log indicates how many people were in your group.
The following sources were used to generate this
cache.
- Secrets of Past Here for the Digging County Is
One of World's Richest Hunting Grounds for Fossils; [Orange County
Edition] GORDON GRANT. Los Angeles Times (pre-1997 Fulltext). Los
Angeles, Calif.: Jun 30, 1986. p. 1
- Orange County
Archaeology and Paleontology Guidelines, Procedures, and
Policies
More Technical Information
A more detailed study of Pecten Reef was completed by Carol Stadum
in her unpublished master theses. I have not had a chance to get a
copy of it. CSULB Geological Sciences Department has offered to let
me review it when I get a chance to get to the university. Carol
Stadum was instrumental in helping preserve the area from becoming
another housing tract. Stadum, Carol J., 1982, The Development and
Analysis of a Paleontological Park in the Pecten Reef of the
Monterey Formation, Orange County, California, Master's Theses
Completed in the CSULB Geological Sciences Department