Quantcast Pleistocene-Age Bluff-Forming Units

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Solana Beach Coastal Preservation Association
August 20, 1998
Project No. 1831
Page 4
2.1.2 Pleistocene-Age Bluff-Forming Units
Bluff-forming units overlie a wave-cut abrasion platform formed on the Eocene
bedrock approximately 120,000 years ago when sea level was 20 feet higher (Lajoie
and others, 1992). At the time, the sea was at a high eustatic level due to
substantial melting of the ice caps during an interglacial period. Today, the
abrasion platform ranges in elevation from approximately 18 feet near San Elijo
Lagoon, to approximately 26 feet at Las Brisas. The difference in elevation is a
result of variable regional uplift associated with gentle tectonic folding during the
last 120,000 years.
Terrace Deposits: The sloping, upper portion of the Solana Beach bluffs is
comprised of predominantly late Pleistocene, moderately-consolidated, poorly-
indurated, light reddish-brown, silty fine sands that include both nearshore marine
and beach sands lithologically similar to the Bay Point Formation (approximately
120,000 years old).
ABeach Ridge@ Type Deposits
The terrace deposits are typically capped by an iron oxide-cemented Abeach ridge@
type residual clayey sand deposit. This erosion-resistant cap material, formed by
the concentration of clayey weathering products, secondary oxides of iron and
aluminum, and leached and reprecipitated salts, is the result of long exposure to the
elements during a period of tropical to temperate climate.
Pleistocene-Age Canyon Fill
Fletcher Cove is bounded on the north and south by the walls of an ancient stream
valley filled by Quaternary-age alluvium, talus and marine estuary sediments. This
infilled stream valley pre-dates the deposition of the overlying Bay Point Formation
(approximately 120,000 years old). As a cliff-forming geologic unit, this material is
more erodible than the adjacent Torrey Sandstone and, hence, has allowed
approximately 80 feet of differential erosion beyond that of the more linear coastal
bluff forming what is today Fletcher Cove.



 


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