the florida state university college of arts and sciences evolution of ...

Recent studies of barriers using Ground Penetrating Radar (GPR) have revealed that
beach ridges can be traced in the subsurface as seaward dipping reflectors with dips of 1-4
degrees that decrease in a seaward direction (Jol et al., 1998; Bristow et al., 2000; Neal et al.,
2002; Moore et al., 2004; Bristow and Pucillo, 2006). Washover-type, landward-dipping beds
are rare. Ridge crests have elevations that are usually above mean high water and adjacent
swales and troughs that are typically below mean low water (Stapor, 1973). Beach ridges are
primarily composed of quartz sand (Doeglas, 1946; Eichenholtz et al., 1989; Otvos, 2000;
Tanner, 1993; Tanner, 1994). It is rare to find shell in older ridges because any shell that was
originally present is usually destroyed by in-situ leaching by rainwater (Stapor, 1973). Beach
ridges that make up beach ridge plains are usually organized into distinct patterns or groups
based on their topographic expression and geographic pattern (Stapor, 1973). These patterns
reflect the energy, direction of sand transport and the mechanisms by which sand was delivered
to the beach face during ridge construction (Stapor, 1973).
The dominant processes controlling the formation of beach ridges are poorly understood.
Several theories have been proposed to attempt to explain the origin of beach ridges. Johnson
(1919) suggested that beach ridges are constructed by wave action along successive shoreline
positions. Shepard (1950) suggested that beach ridges form as a result of aggradation. Psuty
(1966) suggested that beach ridges form during periods of increased water levels resulting from
large, offshore storms. Curray et al. (1969) suggested that ridges form when a longshore bar is
built upwards and emerges above sea level during low wave conditions. The bar enlarges and
becomes a beach ridge. Dunes can then form on the top of the newly formed ridge and stabilize
it. This model is similar to the model of barrier island formation that was proposed by de
Beaumont (1845). Reineck and Singh (1978) proposed that beach ridges form at high tide levels
and are related to storms or high-water stages. Other researchers (e.g., Carter, 1986; Davis et al.,
1972; Fraser and Hester, 1977) believed that the landward shifting of offshore bars forms ridges.
Many researchers support this idea. Tanner (1995) proposed that beach ridge formation is
influenced by small changes in sea level. They are formed by sea-level rise and fall couplets
with magnitudes on the order of 5-30 cm and periodicities of 30-60 years. Under slightly lower
sea level conditions waves are low and run-up doesn’t extend far up the beach profile. A swale
will build under these conditions. When sea level rises, the sea deepens at a fixed distance from
the shore, causing breakers to become higher. As a result, run-up extends further up the beach
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