Geoscience Reference
In-Depth Information
representing mangrove, swamp, woodland, and dry tropical forest vegetation types.
Both the uppermost Culebra and Cucaracha formations contain fossil land mammals
that are Hemingfordian to Barstovian in age (19.5-14 Ma).
The earliest evidence for a terrestrial connection between Panama and North
America is 19 Ma, based on fossil land mammals with only North American affi nities
and Sr analyses of fossil corals and bivalves. Our revised stratigraphy for the Gaillard
Cut demonstrates that the Central American Peninsula was not short-lived in the early
Miocene. We instead fi nd no evidence for the disruption of this peninsula until 6 Ma,
when there is evidence for a short-lived strait across the Panama Canal Basin. The
existence of a peninsula for much of the Miocene has profound implications for our
understanding of the tectonic, climatic, oceanographic, and biogeographic history re-
lated to the formation of the Isthmus of Panama.
KEYWORDS
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Claystone
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Culebra Formation
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Gaillard Cut
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Gatun Formation
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Panama Canal Authority
AUTHOR' CONTRIBUTIONS
Conceived and designed the experiments: Michael Xavier Kirby, Douglas S. Jones,
and Bruce J. MacFadden. Performed the experiments: Douglas S. Jones. Analyzed
the data: Michael Xavier Kirby, Douglas S. Jones, and Bruce J. MacFadden. Contrib-
uted reagents/materials/analysis tools: Douglas S. Jones. Wrote the chapter: Michael
Xavier Kirby.
ACKNOWLEDGMENTS
Michael Xavier Kirby is grateful to A. Coates and J. Jackson for supporting the early
part of this research when Michael Xavier Kirby was a postdoctoral fellow at the
Smithsonian Tropical Research Institute between 2003 and 2004. We thank the ACP
for granting access to localities, F. C. de Sierra and J. Villa of the General de Recursos
Minerales, Republic of Panama, for granting the necessary permits, and P. Franceschi,
D. Irving, and J. Arrocha for providing subsurface data and help in the field. We also
thank R. Cooke, A. Crawford, K. Johnson, E. G. Leigh, Jr., A. O'Dea, J. Ramesch, G.
Retallack, F. Rodriguez, N. Smith, and S. Stanley for assistance and/or useful discus-
sions. We thank K. Campbell, E. G. Leigh, Jr., and G. J. Vermeij for improving the
presentation of our ideas.
