Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Department

Geosciences

First Advisor's Name

Laurel Collins

First Advisor's Committee Title

Committee chair

Second Advisor's Name

Florentin Maurrasse

Second Advisor's Committee Title

Committee member

Third Advisor's Name

Rosemary Hickey-Vargas

Third Advisor's Committee Title

Committee member

Fourth Advisor's Name

James Fourqurean

Fourth Advisor's Committee Title

Committee member

Keywords

benthic foraminifera, Central American Seaway, Isthmus of Panama, diversity, paleoproductivy, paleobiogeography

Date of Defense

3-28-2016

Abstract

The Neogene history of Caribbean deep-sea benthic foraminifera was investigated by calculating changes in paleoproductivity, diversity and paleobiogeography ~26 to 2 Ma, which includes the progressive closure of the Central American Seaway. Three hypotheses were tested: (1) Paleoproductivity values prior to closure of the Central American Seaway are similar in both the Caribbean and equatorial Pacific and then diverge by the time of early shoaling events; (2) Diversity values of benthic foraminifera prior to the closure of the Central American Seaway were similar in the Caribbean and EEP, and had changed by the time of early shoaling; and (3) during the Miocene and into the Pleistocene, the progressive constriction of the CAS affected deep-sea benthic foraminiferal assemblages by increasing their dissimilarity between the Caribbean and equatorial Eastern Pacific. These hypotheses were tested with 104 samples from five Caribbean and EEP deep-sea cores by

calculating paleoproductivity with multiple proxies, determining diversity indices and calculating biogeographic similarity coefficients.

The data supported the first two hypotheses: The greatest change in paleoproductivity occurred at ~8 Ma during seaway constriction, when values diverged between the Caribbean and EEP. After complete seaway closure at ~4 Ma, the Caribbean became oligotrophic, noted by a decrease in high-organic flux species, and an increase in Nuttalides umbonifera, an indicator species. The largest changes in species-level diversity occurred with the barrier to deep-water flow at ~12 Ma, and Caribbean diversity increased at ~8 Ma with seaway constriction. However, the third hypothesis was rejected: Increases in assemblage similarity actually occurred during most major paleoceanographic events, with the only decrease in Caribbean-EEP similarity occurring at ~12 Ma, coincident with a drop in diversity and emplacement of the Panama isthmian sill.

Thus, the barrier to deep-water flow at ~12 Ma affected the composition of tropical American benthic foraminifera more than the largest change in paleoproductivity at ~8 Ma, or closure of the Central American Seaway at ~4 Ma.

Identifier

FIDC000256

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