Stable isotope evidence for declining freshwater input tied to Plio-Pleistocene faunal overturn in the Caribbean

Author(s): Grossman, Ethan L.; Robbins, John A.; Tao, Kai; Rachello-Dolmen, Paola G.; Saxena, Divya; O'Dea, Aaron
Author Affiliation(s): Primary:
Texas A&M University, Department of Geology and Geophysics, College Station, TX, United States
Smithsonian Tropical Research Institute, Panama
Volume Title: Geological Society of America, 2015 annual meeting & exposition
Source: Abstracts with Programs - Geological Society of America, 47(7), p.634; Geological Society of America, 2015 annual meeting & exposition, Baltimore, MD, Nov. 1-4, 2015. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0016-7592 CODEN: GAAPBC
Note: In English
Summary: Faunal overturn in the Southwest Caribbean (SWC) during the Plio-Pleistocene has been primarily attributed to either decreased upwelling and productivity collapse associated with uplift of the Central American Isthmus (CAI; ∼3.5 Ma), or decline in marine temperatures associated with Northern Hemisphere glaciation (NHG) beginning ∼3.3 Ma. Extinction preferentially selected against taxa adapted to nutrient-rich environments uncommon in the SWC today, but the turnover acme occurred 1-2 myr after the final closure of the CAI, which is coincident with the onset of severe NHG. We use ∼3000 new stable isotope measurements of ∼60 serially-sampled gastropods (Conus and Strombus) from Costa Rica and Panama to examine nutrient delivery by upwelling and freshwater input during and after the final closure of the Central American Isthmus ∼3.5 Ma. Gastropod δ18O profiles were referenced to an open-ocean baseline using δ18O values for planktonic foraminifera that lived near the same depth. Foraminiferal δ18O data for the Plio-Pleistocene were derived from sediment cores ODP 999A, DSDP 502B, and MD03-2628 in the Caribbean, and ODP 1242 in the Pacific. Deviation of δ18O profiles from baseline values allows quantification of seasonal upwelling and freshening in the nearshore environments. δ18O profiles of fossil shells do not show the strong upwelling and freshening signals found in modern Pacific Conus profiles. However, SWC specimens older than ∼2.5 Ma show δ18O ranges greater than those of modern specimens, suggesting potential refugia where seasonal upwelling and/or freshening enhanced productivity. The baseline approach points to significantly greater freshening from 2.5-3.6 Ma and no upwelling after 3.5 Ma. The freshening signal in SWC shells declines after 2.5 Ma, signaling a decline in nutrient delivery and providing a causal mechanism for delayed extinction in the SWC.
Year of Publication: 2015
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Atlantic Ocean; Caribbean Sea; Cenozoic; Central America; Colombian Basin; Conus; Costa Rica; DSDP Site 502; Deep Sea Drilling Project; East Pacific; Equatorial Pacific; Foraminifera; Gastropoda; IPOD; Invertebrata; Isotope ratios; Isotopes; Leg 165; Leg 202; Leg 68; Marine environment; Microfossils; Mollusca; Neogene; North Atlantic; North Pacific; Northeast Pacific; O-18/O-16; ODP Site 1242; ODP Site 999; Ocean Drilling Program; Oxygen; Pacific Ocean; Paleo-oceanography; Paleoenvironment; Panama; Pleistocene; Pliocene; Protista; Quaternary; Stable isotopes; Strombus; Tertiary
Coordinates: N124437 N124437 W0784422 W0784422
N112925 N112925 W0792247 W0792247
N075100 N075100 W0833600 W0833600
Record ID: 2016055465
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States