3.5 Cultural Resources
Historical Results
The project area lies within a medium sensitivity zone for the occurrence of historic shipwrecks. No side-
scan sonar targets suggestive of cultural materials were identified within this survey grid. Historic coastal
and marine features that once functioned near the SO-5 project area includes a large natatorium and a pier
at the foot of 10th Street in Del Mar. A barge swamped and sank near the pier and a large steam crane
was knocked into the water when the pier broke up.
MB-1
At MB-1, the water depth varies from 60 feet along the eastern edge of the grid to 110 feet along the
western edge of the grid. At MB-1, five seismic survey lines were conducted approximately perpendicular
to the shoreline, and ten survey lines were conducted parallel to the shoreline. A total of ten vibracores
were collected, primarily in the eastern portion of the grid. The deepest core penetration was 19.3 feet,
on the eastern portion of the grid.
Geoarchaeological Results
No offshore archaeological artifact sites are recorded at dredge area MB-1, although several offshore
artifact sites are located 1.7 miles or more south offshore from Point Loma, in 39- to 59-foot deep water.
MB-1 spans the offshore paleochannel of the San Diego River. Sub-bottom profiles of the MB-1 site
reveal a stair-stepped series of reflectors, suggestive of a series of stable sea level stands at this location.
Since the MB-1 site is adjacent to the Mount Soledad region, it may be undergoing tectonic uplift at a rate
faster than the previously discussed borrow sites; if the sea level rise and local tectonic uplift were
correspondent during some extended time interval, then a series of stable sea level stands would result.
The beach parallelsub-bottom profiles at MB-1 suggest a well defined paleochannel whose axis is directed
east-west, present in the eastern portion of the grid. To the west, the paleochannel intersects what may
be a beach cliff profile, described earlier as representative of a stable sea level stand. The fill of the
paleochannel is characterized by strong but discontinuous seismic reflectors suggestive of a high-energy
depositional environments, such as would be present for fluvial or intertidal deposition.
Based on the sub-bottom and core data, a geologicalcross-sectionfor MB-1 shows the paleochannel with
a fill of layered fluvial/marsh/lagoonal sediments at the north and purely intertidal sediments at the south.
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