Precision in biostratigraphy; evidence for a temporary flow reversal in the Central American Seaway during or after the Oligocene-Miocene transition

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doi: 10.2113/gsjfr.49.4.357
Author(s): Fraass, Andrew J.; Leckie, R. Mark; Lowery, Christopher M.; DeConto, Robert
Author Affiliation(s): Primary:
University of Massachusetts at Amherst, Department of Geosciences, Amherst, MA, United States
University of Texas at Austin, United States
Volume Title: Journal of Foraminiferal Research
Source: Journal of Foraminiferal Research, 49(4), p.357-366. Publisher: Cushman Foundation for Foraminiferal Research, Ithaca, NY, United States. ISSN: 0096-1191 CODEN: JFARAH
Note: In English. NSF Grant AGS-1203910. 107 refs.; illus., incl. 1 table, sketch maps
Summary: 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.
Year of Publication: 2019
Research Program: DSDP Deep Sea Drilling Project
IODP Integrated Ocean Drilling Program
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Angola Basin; Atlantic Ocean; Biostratigraphy; Ceara Rise; Cenozoic; Central American Seaway; DSDP Site 366; DSDP Site 522; DSDP Site 558; DSDP Site 78; Deep Sea Drilling Project; East Pacific; Equatorial Atlantic; Equatorial Pacific; Exmouth Plateau; Expedition 342; First occurrence; Foraminifera; IODP Site U1406; IPOD; Indian Ocean; Integrated Ocean Drilling Program; Leg 108; Leg 122; Leg 130; Leg 150; Leg 154; Leg 199; Leg 202; Leg 41; Leg 73; Leg 82; Leg 9; Lower Miocene; Microfossils; Mid-Atlantic Ridge; Miocene; Nazca Ridge; Neogene; North Atlantic; North Pacific; Northeast Pacific; Northwest Atlantic; Northwest Pacific; ODP Site 1218; ODP Site 1219; ODP Site 1237; ODP Site 667; ODP Site 763; ODP Site 803; ODP Site 904; ODP Site 926; ODP Site 929; Ocean Drilling Program; Oligocene; Ontong Java Plateau; Pacific Ocean; Paleo-oceanography; Paleogene; Paragloborotalia kugleri; Precision; Sierra Leone Rise; South Atlantic; South Pacific; Southeast Pacific; Stratigraphic boundary; Tertiary; Upper Oligocene; West Pacific
Coordinates: S203512 S203511 E1121232 E1121231
N075700 N075700 W1272121 W1272121
S160000 S160000 W0762300 W0762300
N374614 N374615 W0372036 W0372037
Record ID: 2019098013
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Abstract, Copyright, Cushman Foundation for Foraminiferal Research, Reference includes data from GeoScienceWorld, Alexandria, VA, United States