Thermal evolution of the equatorial Pacific thermocline during Eocene Thermal Maximum 2 from foraminifera stable isotope and trace metal analysis

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Author(s): Strojie, Wayne Michael; Harper, D. T.; Zachos, J. C.
Author Affiliation(s): Primary:
University of California Santa Cruz, Santa Cruz, CA, United States
Volume Title: AGU 2017 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2017; American Geophysical Union 2017 fall meeting, New Orleans, LA, Dec. 11-15, 2017. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The late Paleocene and Early Eocene were characterized by a series of brief hyperthermal events, the largest of which is the Paleocene-Eocene Thermal Maximum (PETM, 55.5 Ma) followed by a lower magnitude Eocene Thermal Maximum 2 (ETM2, 53.7 Ma), also known as H1. These events are characterized by a global negative Carbon Isotope Excursion (CIE) coincident with a dissolution horizon in pelagic sediment cores indicative of Carbonate Compensation Depth (CCD) shoaling and significant ocean acidification. The S.E. Atlantic Walvis Ridge ETM2 CIE is a δ13CCarb ≈ 1.0 ppm - 1.5 ppm and δ13CBulk ≈ 3.5 ppm with an estimated 3°C surface and benthic warming. The record of transient hyperthermals such as ETM2 is not as extensive in the Pacific as the Atlantic. Given the size of the Pacific, this represents a critical gap in our understanding of the overall carbon cycle and oceanographic response of this event. Our research investigates the evolution of ocean thermal structure in the equatorial Pacific preceding, during, and after ETM-2. We generated new data on thermocline temperature from ODP Site 1209 Shatsky Rise using planktonic foraminifera δ18O and Mg/Ca while inferring carbon cycle dynamics from δ13C. The data shows 3 CIE's from ≈ 53.7Ma - 53.6Ma (ETM2, H2, and I1). ETM2 is preceded by ≈ 40kyr of bulk and thermocline δ13C convergence with two transient warming steps. The CIE duration ≈ 90kyr with an ≈ 50kyr recovery phase. The total magnitude of peak thermocline warming ≈ 2.0°C to 2.2°C for ETM2. No thermocline warming is observed for H2. I1 peak magnitude of thermocline warming ≈ 3.0°C. Orbital pacing of the carbon cycle is also evident from ≈100kyr separation of ETM2 and H2, an ≈300kyr separation of ETM2 and I1, and an ≈40kyr pre-CIE convergence of δ13Ccarb & δ13Cbulk with an apparent two warming steps ≈15-20kyr apart.
Year of Publication: 2017
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Cenozoic; Foraminifera; Leg 198; Microfossils; North Pacific; Northwest Pacific; ODP Site 1209; Ocean Drilling Program; Pacific Ocean; Paleo-oceanography; Paleocene-Eocene Thermal Maximum; Paleoclimatology; Paleogene; Shatsky Rise; Tertiary; West Pacific
Coordinates: N323900 N324000 E1583100 E1583000
Record ID: 2018074809
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