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Solana Beach Coastal Preservation Association
August 20, 1998
Project No. 1831
Page 3
community. Given the topography of the coastal bluff top within the study area portion of
Solana Beach, natural subaerial erosion processes are less active compared to the majority
of San Diego County=s upper sloping coastal bluffs, and therefore the coastal bluffs along
Solana Beach will tend to sustain a steeper upper-bluff profile.
2.1
Geologic Site Conditions
Geologic units present in the Solana Beach area include the older Eocene Abedrock@
geologic units that form the lower cliffed portion of the bluffs and the late Pleistocene
marine terrace deposits that form the sloping, upper coastal bluffs above the sea cliffs
(Kennedy and Peterson, 1975).
2.1.1 Eocene-Age Seacliff-Forming Units
Two Eocene-age geologic units are exposed, in order of increasing age, from south
to north along the Solana Beach coastline: the Torrey Sandstone and the Delmar
Formation. The approximate areal extent of these relatively resistant, cliff-forming
geologic units is shown on the eight photographs and accompanying maps.
Torrey Sandstone: The Torrey Sandstone is a well-indurated, white-gray to light
yellow-brown, medium- to coarse-grained sandstone. The lower portions of the
Torrey Sandstone contain bioturbated beds and concretions, while the upper
portions exhibit high-angle cross-bedding (Kennedy and Peterson, 1975).
Delmar Formation: The Delmar Formation is a moderately well-indurated, yellow-
green and olive-gray, sandy claystone interbedded with medium gray, coarse-
grained sandstone exposed in the lower portion of the sea cliff northerly of 633
Pacific Avenue. This geologic unit also comprises the more erosion resistant
offshore reefs within the northerly portion of the city. Abundant well-cemented
oyster beds exist within this geologic unit, substantially contributing to its erosion
resistance and also responsible for the presence of Tabletop reef extending some
distance offshore (Kennedy and Peterson, 1975).



 


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