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The AAPG/Datapages Combined Publications Database
GCAGS Transactions
Abstract
ABSTRACT: Biogeographic Comparisons of Neogene Benthic Foraminifera
of Venezuela, Panama, and Ecuador
Carly J. Smith1, Laurel S. Collins2, Carlos Jaramillo3,
and Luis I. Quiroz4
1Department of Earth Sciences, Florida International University, 11200 SW 8th St., Miami, Florida 33199
2Department of Earth Sciences and Department of Biological Sciences, Florida International University, 11200 SW 8th St., Miami, Florida 33199
3Center for Tropical
Paleoecology and Archeology, Smithsonian
Tropical
Research
Institute,
410 Tupper Bldg., Roosevelt Ave., Balboa, Ancon, 0843-03092, Panama
4Department of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, Saskatchewan, S7N 5E2, Canada
Upper Miocene to Pliocene shallow-water benthic foraminiferal assemblages
from
Venezuela, Panama, and Ecuador are compared to assess the effects of the constricting
Central American Seaway on Caribbean and tropical
Eastern Pacific biotas. Before
the
completion of the Panama land bridge, shallow-water marine environments and
their
faunas on either side of the Isthmus were more similar than they are today.
The prediction
is that the gradual separation of Caribbean and
tropical
Eastern Pacific waters
resulted
in the progressive differentiation of the two faunas. While uplift from the
collision
of the Panama arc with South America began to affect deep-sea circulation by
the
late Middle Miocene, and complete deepwater cutoff is generally dated to ~8
Ma, the
timing of surface-water changes and the resulting divergence of Pacific and
Caribbean
neritic faunas remains unclear. The present study uses Upper Miocene and middle
Pliocene
benthic foraminifera from inner to outer neritic (<200m) deposits of northwestern
Venezuela, Caribbean and Pacific Panama, and coastal Ecuador. The relationships
between
the assemblages are measured using similarity indices such as Simpson's and
Jaccard's.
As an additional characteristic of assemblages, the diversity of each sample
is
measured using Fisher's alpha. Assemblages deposited shortly before and after
the ~8
Ma deepwater cutoff are compared, as well as those deposited during seaway
closure, at
~3.5 Ma.