Sea levels of minus 20 feet (20 centuries X 1 ft./Century) would have
produced a negligible difference compared to present coastlines with
respect to movement in the Caribbean Basin. In the Real World,
coastlines have been relatively stable in the present configurations
during that period. Sea level changes would need to be in the range of
minus 20-60 Meters (in other words, at least three times the assumed
change) to make any significant alterations in coastlines sufficient
to facilitate land travel between continental NA and Cuba. During and
immediately following the last Ice Age (12-8 thousand years ago) was
the most recent time for such lowered sea levels. (That should not be
read to mean that a difference in 20 ft. would not have had cultural
impact on the coastal inhabitants. Some coastal archaeological sites
have been submerged by the smaller rise during the last 2500 years.)
Caribbean Prehistory, SEAC
Prehistory of the Caribbean Culture Area
http://www.cr.nps.gov/seac/caribpre.htm
"Although the Lesser and Greater Antilles were home to various types
of extinct Pleistocene megafauna, such as the giant ground sloth
(Megaelocsus), no actual cultural artifacts have been identified for
this time period (ca. 10,000 - 6,000 B.C.) for the Caribbean Islands.
Some authors have treated the occurrence of Pleistocene megafauna and
an acknowledged lower sea level of nearly 20-meters that could
facilitate travel between the northern coast of South American and the
Antilles during the Paleoindian period as positive conditions for
Paleoindian occupation (Veloz Maggiolo and Ortega 1976)."
You will note in the following the graphed curves for sea level, as
well as the photographs of coastline features with Pleistocene
coastlines superimposed.
Middle Holocene Sea-Level and Evolution of The Gulf of Mexico Coast
(USA)
Michael D. Blum, Amy E. Carter, Tracy Zayac, and Ron Goble
http://www.science.ulst.ac.uk/ics2002/blum_md%20et%20al.pdf
"During the OIS 4-2 glacial period (ca. 70-15 ka.), large coastal
plain rivers cut distinct valleys across OIS 5 Beaumont
alluvial-deltaic plains and the Ingleside shoreline, and extended
their courses to mid-shelf or farther basin-ward positions (BLUM et
al., 1995; BLUM and STRAFFIN, 2001; ANDERSON et al., 1996).
Development of the present shoreline is directly coupled to the
sea-level rise that accompanied deglaciation. A number of late
Pleistocene to Holocene sea-level curves have been published for the
western Gulf of Mexico (CURRAY, 1960; S H E PARD, 1963; COLEMAN and
SMITH, 1964; NELSON and BRAY, 1970; FRAZIER, 1974; THOMAS, 1990), with
each showing continual submergence until ca. 4-3 ka or later (Figure
2A). Most sea-level curves from the eastern Gulf of Mexico and the
Atlantic coast of Florida also interpret continual submergence until
ca. 3-2 ka or later (e.g. SCHOLL et al., 1969; PARKINSON, 1989;
TOSCANO and LUNDBERG, 1998; GOODBRED et al., 1998). ANDERSON and
THOMAS (1991) note that most curves, FRAZIER’s (1974) in particular,
show discontinuous rates of rise similar to the "eustatic" curve
published by FAIRBANKS (1989) using data from Barbados."
[...]
"and present bay outlines were not reached until ca. 4000 yrs BP. Work
by PAINE (1991) in Copano Bay, as well as ANDERSON and THOMAS (1991),
ANDERSON et al. (1991; 1992), SIRINGIN and ANDERSON (1993), and
RODRIGUEZ (1999) in Galveston Bay refined this general model. Most
recently, RODRIGUEZ (1999) argued that seismically-identified
"flooding surfaces" at –14 and –10 m demarcate rapid landward
translation of environments and modification of bay morphologies due
to episodic sea-level rise. RODRIGUEZ (1999) further suggested the
last event of this kind occurred ca. 4 ka, and that modern sea-level
positions were not reached until ca. 3 ka."
[...]
"BLUM et al.’s (2001) interpretation of sea level history along the
northwestern Gulf of Mexico shoreline in Texas implies that sea level
reached present positions some 3-5 kyr before traditional
interpretations would suggest, and raises a number of questions
regarding coastal evolution."
MIDDLE HOLOCENE SEA-LEVEL RISE AND HIGHSTAND AT +2 M, CENTRAL TEXAS
COAST
MICHAEL D. BLUM 1 , TAMARA J. MISNER 1 , ERIC S. COLLINS 2 , DAVID B.
SCOTT 2 , ROBERT A. MORTON 3 , AND ANDRES ASLAN 4
http://www.colorado.edu/geolsci/jsedr/Abstracts/july2001/Blum.PDF
Chapter 8. NORTH PENINSULAR GULF COAST, 2500 B.P.-A.D. 1600
http://dhr.dos.state.fl.us/bar/hist_contexts/wwwnpgc.pdf
T10. Holocene Climate Change: Seasonal Variability to Centennial
Trends
http://gsa.confex.com/gsa/2001AM/finalprogram/session_638.htm
SEARCH TERMS
://www.google.com/search?hl=en&lr=&ie=ISO-8859-1&q=sea+level+change+prehistoric+Caribbean
://www.google.com/search?hl=en&lr=&ie=ISO-8859-1&q=coastline+change+prehistoric+Caribbean
://www.google.com/search?q=%22Gulf+of+Mexico%22+Holocene+coastline+change
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