the florida state university college of arts and sciences evolution of ...
the florida state university college of arts and sciences evolution of ...
the florida state university college of arts and sciences evolution of ...
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likely initiated during times <strong>of</strong> lower sea level (Tanner, 1991). Increased wave action leads to<br />
<strong>the</strong> transport <strong>of</strong> both fine <strong>and</strong> coarse-grained sediment, which is <strong>the</strong>n deposited as a ridge at <strong>the</strong><br />
shoreline. A rise in sea level will flood <strong>the</strong> l<strong>and</strong>ward side <strong>of</strong> <strong>the</strong> ridge <strong>and</strong> isolate it, thus, turning<br />
it into a barrier isl<strong>and</strong>.<br />
There have been few studies <strong>of</strong> barrier isl<strong>and</strong> <strong>evolution</strong> along <strong>the</strong> Panh<strong>and</strong>le coast. Rizk<br />
(1991), Tanner (1987) <strong>and</strong> Forrest (2003) have studied <strong>the</strong> St. Joseph Peninsula, a barrier spit<br />
located on <strong>the</strong> Panh<strong>and</strong>le coast. Stapor (1973) <strong>and</strong> Tanner (1988, 1990) studied St. Vincent<br />
Isl<strong>and</strong>, a barrier isl<strong>and</strong> also located on <strong>the</strong> Panh<strong>and</strong>le coast.<br />
Beach Ridge Formation<br />
Many late Holocene coastal regions are progradational <strong>and</strong> are marked by beach ridge<br />
plains. Well-developed beach ridge plains can contain up to 200 individual beach ridges<br />
(Tanner, 1988). The term “beach ridge” has been defined in many different ways. Stapor<br />
(1975) defines beach ridges as linear s<strong>and</strong> bodies that parallel <strong>the</strong> modern coast. Otvos (2000)<br />
defines <strong>the</strong>m as relict, semi-parallel, multiple wave- <strong>and</strong> wind-built l<strong>and</strong>forms that originate in<br />
<strong>the</strong> intertidal <strong>and</strong> supratidal zones. Tanner (1995) identified four main categories <strong>of</strong> beach<br />
ridges. Swash built ridges <strong>and</strong> settling-lag ridges are long, low to almost invisible <strong>and</strong> more or<br />
less parallel. They usually occur in sets. The two ridge types can be distinguished from each<br />
o<strong>the</strong>r based on <strong>the</strong>ir internal structure. Swash built ridges display low-angle cross-bedding while<br />
settling-lag ridges have internal bedding that is horizontal, discontinuous <strong>and</strong> usually poorly<br />
defined. These two types can be distinguished by trenching or sample analysis. Storm surge<br />
ridges are usually single, isolated features, 5-10 m in height. They do not make up beach ridge<br />
sets or systems. The fourth type <strong>of</strong> ridge is <strong>the</strong> dune ridge. Dune ridges are distinguished from<br />
o<strong>the</strong>r ridge types on <strong>the</strong> basis <strong>of</strong> <strong>the</strong>ir internal structure, which is characterized by internal cross-<br />
bedding <strong>and</strong> hummocky cross-stratification. Dune ridges can be found within or adjacent to a<br />
system <strong>of</strong> swash or settling lag ridges.<br />
Beach ridge systems are made up <strong>of</strong> multiple parallel ridges <strong>and</strong> swales, but usually lack<br />
well-developed lagoons or marshes (Boggs, 1995). A popular idea is that beach ridges within a<br />
set are attached to eacho<strong>the</strong>r at a single point. The point <strong>of</strong> attachment facilitates a determination<br />
<strong>of</strong> <strong>the</strong> s<strong>and</strong> source (Tanner et al., 1989).<br />
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