The Early Late Miocene Cessation of Deep and Intermediate Water Circulation through the Central American Seaway

• Main Author: Kwiatkowski, Benjamin Stanley
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: CUNY Academic Works 2024
• Subjects: 100 kyr Cycles; Caribbean Carbonate Crash; Central American Seaway; Great American Biotic Interchange; Negative Carbon Isotope Excursion; North Atlantic Deep Water; Environmental Sciences; Pacific; North Atlantic
• Online Access: https://academicworks.cuny.edu/gc_etds/5832; https://academicworks.cuny.edu/context/gc_etds/article/6812/viewcontent/Dissertation___4924b.pdf

The state of the middle late Miocene global ocean circulations which regulated climate and affected deep ocean chemical environments were impacted by geographic changes. During the Miocene, cirum-equatorial circulations slowly decreased, which included through the seaway between the Americas called the Central American Seaway (CAS). Its shoaling and ultimate closing led to the onset of modern day oceanic circulation as characterized by the global thermohaline circulation. However, this seaway has a long hotly debated history concerning the timing of its restriction and shallowing owing in part to the shifting of tectonic plates. The goal of this research focuses on investigating the shoaling history of the CAS between 12.1 and 9.3 Ma, a critical time of this seaway as new studies suggests that major changes occurred in the CAS that permanently altered global oceanic circulation closer to the modern state that exists today. In addition, carbonate crashes observed in various ocean basins, including the Caribbean, a newly discovered negative carbon isotope excursion, carbon isotope maxima events, and δ18O Mi events that occurred during this time are also investigated and are shown to have common causal mechanisms. This was accomplished by developing high v resolution (~4 ky) integrated data sets (eg., δ18O, δ13C, CaCO3 wt %, benthic planktic foraminiferal ratios, and percent sand size fraction) at ODP Site 1000 located in the western Caribbean in 916 m water depth. From these new data sets a new picture of the middle late Miocene transition emerges. The first important conclusion was to identify a new shoaling event for the CAS at 11.6 – 11.4 Ma. As the CAS shoaled and constricted, less Pacific sourced waters entered the Atlantic as reductions in Atlantic sourced waters entered the Pacific. The result was the occurrences of increased Northern Component Waters (i.e., Proto-North Atlantic Deep Water). After this event, the first significant basin to basin fractionation occurred as observed in the δ13C records ...