3.5 Cultural Resources
wreckage washed ashore at Cardiff State Beach in 1991. Another probable wreck site was reported in
the August 1955 San Diego Union.
SO-5
The water depth varies from 50 feet along the eastern edge of the grid to 100 feet along the western portion
of the grid. At SO-5, five seismic survey lines were conducted approximately perpendicular to the beach
direction, and seven survey lines were conducted parallel to the beach direction. A total of ten vibracores
were collected, primarily in the central portion of the grid. The deepest core penetration was 12 feet, on
the eastern portion of the grid.
Geoarchaeological Results
Two offshore archaeological artifact sites are recorded near SO-5, along the southern margin of the San
Dieguito River valley, in the intertidal zone and at 10 feet water depth (Masters 1983, Sites 23 and 33).
At each of these sites a single artifact has been recovered.
Borrow site SO-5 spans the offshore paleochannel of the San Dieguito River. The side scan sonar data
suggest a featureless seafloor, except for a small region of rippled bedforms in the southeast and in the
northeast corner of the grid. The sub-bottom profiles revealed a clear bedrock layer beneath sedimentary
sequences that thicken seaward. In the beach parallel profiles, the outline of a paleochannel is preserved,
with its axis directed east-west. Based on the survey and core data, a geological cross-section was
developed for SO-5. The interpretation shows the paleochannel at depth beneath SO-5, filled with a
succession of sediments. It should be noted that at the intertidal/fluvial interface in one of the cores, a
fractured piece of quartzite (a stone material known to be used for tool manufacture) was observed. While
possibly suggestive of humanly produced flaked stone material, it was not definitive.
The potentialfor occurrence and preservation of archaeological sites within SO-5 is moderate to high. This
is due to the presence of a paleochannel which might have been an attractive feature for prehistoric
habitation, and also the presence of a contact between fluvial (pre-transgression) and intertidal
(transgression) deposits. Also, there are two already recorded offshore artifact sites along the southern
margin ofthis paleochannel. The highest potential to encounter buried archaeological sites within SO-5 may
be along the margins of the paleochannel, although an object suggestive of flaked lithic materials was found
within a core in the interior of the paleochannel.
Regional Beach Sand Project EIR/EA
Page 3.5-11
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