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Solana Beach Coastal Preservation Association
August 20, 1998
Project No. 1831
Page 6
the Rose Canyon fault zone running approximately parallel to the coast, two to three miles
offshore. Movement along the fault appears to have caused gentle folding on the coastal
side of the fault. The gentle folding has caused a small southeast dip in the Eocene-age
formations, thus exposing progressively older formations northerly along the coast. In
more recent times, the 120,000-year-old wave-cut abrasion platform has been tilted to the
northwest at about 0.1 degree.
Tectonic forces are also evident in the localized folding and faulting of the Eocene-age
sediments. The episodes of faulting and long-continued tectonic stresses have resulted in
hundreds of visible joints, fractures and shear zones having both micro- and large-scale
variations in erosion potential. Several of the sea caves, most notably northerly of Tide
Park, formed along these Pleistocene age faults where fractures and shear zones allow
differential erosion and the propagation of a sea cave along the axis of the fault. Fault-
induced sea caves southerly of Tide Park are limited to those below Las Brisas and 231
Pacific Avenue; however, most of the sea caves northerly of Tide Park are fault-controlled.
Faulting has also juxtaposed the Delmar Formation against the Torrey Sandstone below
633 Pacific Avenue with the Delmar Formation upthrust against the Torrey Sandstone and
likely contributing to the presence of Tabletop Reef just to the north.
2.3
Coastal Bluff Geomorphology
2.3.1 Terminology for the Bluff and Adjacent Shore
The geomorphology of a typical coastal-bluff profile is shown in Figure 2. The
Figure shows the shore platform, a lower near-vertical cliffed surface called the
seacliff, and an upper bluff slope generally ranging in inclination between 35 and 65
degrees (measured from the horizontal). The bluff top is the boundary between the
upper bluff and the flat to gently sloping coastal terrace.
Offshore from the seacliff is an area of indefinite extent called the nearshore zone
(see Figure 2). The bedrock surface in the nearshore zone, which extends out to
sea from the base of the seacliff, is the shore platform. Worldwide, the shore
platform may vary in inclination from horizontal, to a gradient of three horizontal to
one vertical, or 33- percent (Trenhaile, 1987). Offshore from Solana Beach, the






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