GRAHAM, ALAN. Department of Biological Sciences, Kent State University, Kent, OH 44242. - Geohistory models and paleovegetation of the Caribbean region.
The Caribbean region is tectonically one of the most complicated on
Earth, as evidenced by some 13 'mobilist' models that have been
proposed to explain its geohistory. Some consensus is developing
around one recent model that places a Cretaceous volcanic arc of
islands in the eastern Pacific that moved 1000 km between the portal
formed as North and South America moved apart. The principal
difference between this version and older models is that the land
forming the proto-Antilles originated as islands and was never a
continuous or near-continuous land bridge connecting or nearly
connecting the continents. There is also uncertainty about the
emergent-submergent history of the individual land fragments. The arc
began colliding with the Bahamas Platform in about the middle Eocene
(49 Ma), and that probably began the principal period of emergence for
the Greater Antilles. The collision was at an angle (transpression)
toward the east with Puerto Rico emerging last in the middle Oliogcene
(29 Ma). The Lesser Antilles are middle to late Eocene in age. Among
recent contributions to Caribbean biohistory are a study of the middle
Eocene Saramaguacan flora of Cuba, proposal of a connection (a
'landspan') between North and South America via the Antilles 35-32 Ma
involving an emergent Aves Ridge, and continuing assessment of
vicariance and dispersal as means of distribution of plants and
animals in the Caribbean region.
Key words: Caribbean, geology, paleobotany