New biostratigraphic, magnetostratigraphic and isotopic insights into the Middle Eocene Climatic Optimum in low latitudes

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doi: 10.1016/j.palaeo.2010.09.016
Author(s): Edgar, K. M.; Wilson, P. A.; Sexton, P. F.; Gibbs, S. J.; Roberts, A. P.; Norris, R. D.
Author Affiliation(s): Primary:
University of Southampton, School of Ocean and Earth Science, Southampton, United Kingdom
Scripps Institution of Oceanography, United States
Volume Title: Palaeogeography, Palaeoclimatology, Palaeoecology
Source: Palaeogeography, Palaeoclimatology, Palaeoecology, 297(3-4), p.670-682. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0031-0182 CODEN: PPPYAB
Note: In English. 54 refs.; illus., incl. 2 plates, 2 tables, sketch map
Summary: The Middle Eocene Climatic Optimum (MECO) was a warming event that interrupted the long-term Eocene cooling trend. While this event is well documented at high southern and mid-latitudes, it is poorly known from low latitudes and its timing and duration are not well constrained because of problems of hiati, microfossil preservation and weak magnetic polarity in key sedimentary sections. Here, we report the results of a study designed to improve the bio-, magneto- and chemostratigraphy of the MECO interval using high-resolution records from two low-latitude sections in the Atlantic Ocean, Ocean Drilling Program (ODP) Sites 1051 and 1260. We present the first detailed benthic foraminiferal stable isotope records of the MECO from the low latitudes as well as the biostratigraphic counts of Orbulinoides beckmanni and new magnetostratigraphic results. Our data demonstrate a ∼750 kyr-long duration for the MECO characterized by increasing δ13C and decreasing δ18O, with minimum δ18O values lasting ∼40 kyr at 40.1 Ma coincident with a short-lived negative δ13C excursion. Thereafter, δ18O and δ13C values recover rapidly. The shift to minimum δ18O values at 40.1 Ma is coincident with a marked increase in the abundance of the planktonic foraminifera O. beckmanni, consistent with its inferred warm-water preference. O. beckmanni is an important Eocene biostratigraphic marker, defining planktonic foraminiferal Zone E12 with its lowest and highest occurrences (LO and HOs). Our new records reveal that the LO of O. beckmanni is distinctly diachronous, appearing ∼500 kyr earlier in the equatorial Atlantic than in the subtropics (40.5 versus 41.0 Ma). We also show that, at both sites, the HO of O. beckmanni at 39.5 Ma is younger than the published calibrations, increasing the duration of Zone E12 by at least 400 kyr. In accordance with the tropical origins of O. beckmanni, this range expansion to higher latitudes may have occurred in response to sea surface warming during the MECO and subsequently disappeared with cooling of surface waters. Abstract Copyright (2010) Elsevier, B.V.
Year of Publication: 2010
Research Program: ODP Ocean Drilling Program
Key Words: 10 Paleontology, Invertebrate; 12 Stratigraphy, Historical Geology and Paleoecology; Atlantic Ocean; Biochemistry; Biogeography; Biostratigraphy; Blake Nose; Blake Plateau; C-13/C-12; Carbon; Cenozoic; Chronostratigraphy; Cores; Demerara Rise; Diachronism; Eocene; Equatorial Atlantic; Experimental studies; Foraminifera; Geochemistry; High-resolution methods; Invertebrata; Isotope ratios; Isotopes; Leg 171B; Leg 207; Magnetostratigraphy; Marine environment; Marine sediments; Microfossils; Middle Eocene; Middle Eocene Climatic Optimum; North Atlantic; Northwest Atlantic; O-18/O-16; ODP Site 1051; ODP Site 1260; Ocean Drilling Program; Orbulinoides beckmanni; Oxygen; Paleo-oceanography; Paleoclimatology; Paleogene; Paleogeography; Paleolatitude; Paleomagnetism; Planktonic taxa; Protista; SEM data; Sediments; Stable isotopes; Tertiary; West Atlantic
Coordinates: N300311 N300311 W0762128 W0762128
N091600 N091600 W0543300 W0543300
Record ID: 2011015649
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands