Precision in Biostratigraphy: Evidence For a Temporary Flow Reversal in the Central American Seaway During Or After the Oligocene-miocene Transition

Abstract

The Oligocene-Miocene Transition (OMT) was a time of significant oceanic, climatic, and biotic change, but there is still a great deal we do not understand about its effects, particularly in terms of ocean circulation. The Central American Seaway (CAS) was an important ocean gateway at this time; recent fully coupled modeling results have suggested a possible temporary reversal of surface flow, from westward to eastward, during the OMT. Such a flow reversal would have altered numerous oceanographic properties and the dispersal of marine taxa. Here, we find a mismatch in the timing of the Atlantic vs. Pacific first appearances of the tropical mixed layer planktic foraminifer Paragloborotalia kugleri, a key zonal marker for the OMT. The first appearance ages for P. kugleri from fourteen ocean drilling sites vary from ∼23.2–23.05 Ma in the Pacific to ∼23.05–22.7 Ma in the Atlantic. Key requirements for including a site in this compilation are: 1) sampling resolution; 2) independent non-biostratigraphic chronology, such as magnetostratigraphy or orbital tuning; and 3) a preference for shore-based biostratigraphic analyses rather than shipboard estimates. Although we explore alternative explanations, we conclude that, given the restricted nature of the CAS gateway, timing of dispersal, and results from previous modeling efforts, CAS flow reversal is the most parsimonious explanation for the delayed first appearance of P. kugleri in the Atlantic relative to the Pacific. We suggest that after originating in the tropical Pacific, P. kugleri was initially blocked from dispersal into the Atlantic by westward surface circulation through the CAS during the latest Oligocene. During the OMT, circulation reversed and Pacific surface water flowed through the CAS into the Atlantic, allowing P. kugleri to disperse into the Atlantic. Previously published ocean-climate simulations suggest that the cause of this reversed flow may be related to the progressive constriction of Tethys and opening of the Drake Passage at the time of the OMT, compounded by a short-lived glaciation event in Antarctica and possible change in meridional temperature gradient and prevailing wind patterns in the tropics.

Biogeography of Greater Antillean freshwater fishes, with a review of competing hypotheses

“…7), Nandopsis is nested within South American cichlids, suggesting direct immigration to Hispaniola or Cuba from South America. The present Nandopsis divergence estimate precedes a period of current reversal in the Central American Seaway that temporarily allowed Pacific inflow into the Caribbean, ∼23 Ma (Fraass et al, 2019). This could have facilitated northward transport of rafts from the subandean river and aligns in time with the Mi1 sea-level fall (Miller et al, 2020a), which could have shortened distances from South America to Hispaniola and Cuba.…”

“…If the MRCA inhabited the subandean river, rafts of vegetation discharged into the Central American Seaway may have been carried, perhaps within a plume of brackish water (Tagliacollo et al, 2017), into the Central American Seaway. In the Oligocene, the seaway current flowed westward (Fraass et al, 2019). This would have transported the subandean-river plume toward the Pacific Ocean, but Late Eocene narrowing of the seaway as the Panamá Arc collided with South America (Montes et al, 2012; McGirr et al, 2021) could have increased potential for landfall en route.…”

Pliocene to Earliest Pleistocene (5–2.5 Ma) Reconstruction of the Kuroshio Current Extension Reveals a Dynamic Current

“…Complete closure of the CAS likely occurred between 4.2 and 2.4 Ma (Chaisson, 2003; Groeneveld et al., 2014; Haug et al., 2001; Kameo & Sato, 2000; Keigwin, 1982; Keller et al., 1989; Osborne et al., 2014; Figure 6f). Closure dates are corroborated by differentiation of planktic foraminiferal assemblages in the Caribbean and eastern Pacific Ocean basins (Chaisson & Ravelo, 2000; Keller et al., 1989) throughout this time, with CAS constriction and closure having a large effect on plankton evolution (e.g., Chaisson, 2003; Fraass et al., 2019; Lam & Leckie, 2020a)…”

“…Complete closure of the CAS likely occurred between 4.2 and 2.4 Ma (Chaisson, 2003;Groeneveld et al, 2014;Haug et al, 2001;Kameo & Sato, 2000;Keigwin, 1982;Keller et al, 1989;Osborne et al, 2014; Figure 6f). Closure dates are corroborated by differentiation of planktic foraminiferal assemblages in the Caribbean and eastern Pacific Ocean basins (Chaisson & Ravelo, 2000;Keller et al, 1989) throughout this time, with CAS constriction and closure having a large effect on plankton evolution (e.g., Chaisson, 2003;Fraass et al, 2019;Lam & Leckie, 2020a) In concert with the closure of the CAS on the eastern side of the Pacific, the Western Pacific Warm Pool (WPWP) expanded to the north (Sato et al, 2008; Figure 6c). The WPWP is maintained by easterly trade winds that pile up warm waters in the western equatorial Pacific and eastern Indian oceans, with an annual average SST of 28°C (Webster & Palmer, 1997;Yan et al, 1992).…”

Evidence of a South Asian Proto‐Monsoon During the Oligocene‐Miocene Transition

“…An average southward shift of the ITCZ during the Oligocene to Miocene glaciation has also been suggested to occur on the basis of data from the equatorial Pacific and Atlantic Oceans: a transient change in surface water flow direction is thought to have allowed the migration of planktic foraminifera Paragloborotalia kugleri from the Pacific into the Atlantic via the Central American Seaway (Fraass et al., 2019), and a temporary alteration in wind direction drove dust provenance changes in the equatorial Pacific (Hyeong et al., 2014). Due to the low‐resolution nature of both of these datasets, exact timings for these changes are not well‐constrained, however both are associated with the early OMT glaciation event (“Mi‐1” event; Miller et al., 1991).…”