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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Gulf <strong>of</strong> Mexico Sea-level Record<br />
Several sea-level curves have been created for <strong>the</strong> Gulf <strong>of</strong> Mexico using a variety <strong>of</strong> sea-<br />
level indicators. These sea-level curves can be divided into two groups, those that involve dating<br />
shoreline indicators <strong>and</strong> those that are based on sedimentological studies. Curray (1960) created<br />
a curve based on samples from <strong>the</strong> Texas <strong>and</strong> Louisiana shelf. These samples were shells from<br />
organisms that lived near <strong>the</strong> shoreline <strong>and</strong> were radiocarbon dated to provide age control.<br />
Frazier (1974) created a curve for <strong>the</strong> northwest portion <strong>of</strong> <strong>the</strong> Gulf <strong>of</strong> Mexico (Texas <strong>and</strong><br />
Louisiana coasts). This curve was based on radiocarbon dates from peat, molluscs <strong>and</strong><br />
pelecypods. Scholl et al. (1969) provided sea-level data for south Florida based on radiocarbon-<br />
dated peats from <strong>the</strong> Everglades region. Stapor <strong>and</strong> Tanner (1977) presented a sea-level curve<br />
based on a plane table leveling or topographic pr<strong>of</strong>ile across <strong>the</strong> beach ridge plain on St. Vincent<br />
Isl<strong>and</strong>. Tanner (1991) produced a late Holocene sea-level curve for <strong>the</strong> Gulf <strong>of</strong> Mexico based on<br />
grain size studies. The sea-level curve was derived from topographic pr<strong>of</strong>iling <strong>and</strong><br />
granulometric parameters on St. Vincent Isl<strong>and</strong> <strong>and</strong> later confirmed at several o<strong>the</strong>r locations<br />
along <strong>the</strong> Gulf <strong>of</strong> Mexico coastline (Tanner, 1991). A sea-level history was developed for an<br />
isl<strong>and</strong> (Isla del Carmen) on <strong>the</strong> western edge <strong>of</strong> <strong>the</strong> <strong>state</strong> <strong>of</strong> Campeche in Mexico (Alvarez 1984,<br />
1985). Ano<strong>the</strong>r record comes from Mesa Del Gavilan, an isl<strong>and</strong> west <strong>of</strong> Boca Chica, Texas<br />
(Tanner et al., 1989). The isl<strong>and</strong> is made up <strong>of</strong> 30+ beach ridges. The ridges were trenched <strong>and</strong><br />
sampled <strong>and</strong> a granulometric analysis was conducted (Tanner et al., 1989). Walker et al. (1995)<br />
created a sea level curve for <strong>the</strong> Gulf <strong>of</strong> Mexico based on archaeological evidence from<br />
southwest Florida.<br />
Sea-level curves spanning from <strong>the</strong> Last Glacial Maximum (approximately 21,000 years<br />
ago) to <strong>the</strong> present are available for <strong>the</strong> Gulf <strong>of</strong> Mexico. In general <strong>the</strong> Last Glacial Maximum<br />
had a lowst<strong>and</strong> <strong>of</strong> about –120 m (Balsillie <strong>and</strong> Donoghue, 2004). Sea level <strong>the</strong>n rose in a series<br />
<strong>of</strong> spurts alternating with stillst<strong>and</strong>s. Between 5,000 <strong>and</strong> 7,000 years ago sea level reached close<br />
to modern levels <strong>and</strong> has since oscillated up <strong>and</strong> down a few meters. Walker et al. (1995)<br />
showed that between 3,000 <strong>and</strong> 2,000 years <strong>the</strong>re were two sea level highst<strong>and</strong>s between 1.5 <strong>and</strong><br />
2 m above present level. Sea level is currently rising. Despite <strong>the</strong> abundance <strong>of</strong> sea-level<br />
curves, <strong>the</strong> history <strong>of</strong> sea-level change over <strong>the</strong> past 5,000-6,000 years is still highly debated.<br />
This is, in part, a result <strong>of</strong> a lack <strong>of</strong> reliable data. There are three main schools <strong>of</strong> thought. The<br />
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