Coherent pattern and timing of the carbon isotope excursion and warming during Eocene Thermal Maximum 2 as recorded in planktic and benthic foraminifera

Abstract

[1] Eocene Thermal Maximum 2 (ETM2; ∼53.7 Ma) occurred approximately 2 Myr after the PaleoceneEocene Thermal Maximum (∼55.5 Ma) and was characterized by a deep-sea warming of >3°C, associated with massive release of carbon into the ocean-atmosphere system. We performed single-specimen stable isotope analyses of the planktic foraminiferal genera Acarinina (surface dweller) and Subbotina (thermocline dweller) from Ocean Drilling Program Sites 1265, 1267, and 1263 (Walvis Ridge, SE Atlantic Ocean) and compared high-resolution planktic and benthic stable isotope records to constrain the surface warming and the bathymetric pathway of the carbon isotope excursion during ETM2. Tests of the thermocline dweller Subbotina are absent from sediment deposited during the peak of ETM2. The Acarinina carbon and oxygen isotope records of Sites 1263, 1265, and 1267 are strikingly similar, despite some test recrystallization and large differences in burial depths. Sea surface temperature (SST) estimates based on d18 O isotope values of Acarinina indicate a SST increase of ∼2°C, significantly less than the >3°C estimated for bottom water warming. The maximum negative carbon isotope excursion for Acarinina was ∼1.7‰, slightly more than in the deep sea (∼1.4‰). The planktic and benthic isotope records do not show time lags, indicating that during ETM2 the isotopically depleted carbon injected into the ocean-atmosphere system was rapidly mixed within all oceanic carbon reservoirs.

Productivity response of calcareous nannoplankton to Eocene Thermal Maximum 2 (ETM2)

“…The effect of temperature variations on placolith Sr/Ca values is minor during ETM2. The δ 18 O in benthic and planktonic foraminifera during ETM2 (Site 1265) shows a ∼2-4 • C increase (Stap et al, 2010a). This implies that at Walvis Ridge, 4-8 % of the 13 to 21 % Sr/Ca increase in Coccolithus and Toweius, respectively, could be attributed to temperature.…”

Down the Rabbit Hole: toward appropriate discussion of methane release from gas hydrate systems during the Paleocene-Eocene thermal maximum and other past hyperthermal events

“…There is also a growing appreciation that the PETM is only the most prominent of a series of "hyperthermal" events that occurred during long-term deep-ocean warming of the early Paleogene Nicolo et al, 2007;Agnini et al, 2009;Stap et al, 2009Stap et al, , 2010Leon-Rodriguez and Dickens, 2010;Zachos et al, 2010). At least five other events, presently called ETM2/H1, H2, I1, I2, and K/X (following Cramer et al, 2003), have been identified in multiple records and follow the PETM at approximately 53.7, 53.6, 53.3, 53.2, and 52.5 Ma.…”

Surviving rapid climate change in the deep sea during the Paleogene hyperthermals

“…Benthic foraminiferal assemblages declined in diversity with postexcursion assemblages similar to the low-diversity post-PETM ones (13)(14)(15), but without significant extinction. Carbonate dissolution occurred and the lysocline rose, but the CCD did not shoal to (or beyond) the depth of the sites in the southeast Atlantic where dissolution was complete during the PETM (16).…”

“…Eocene Thermal Maximum 2 (ETM-2, ∼53.2 Ma) occurred about 2 million years after the PETM and provides the opportunity for a comparative study, because it is qualitatively similar to the PETM, with only about half its magnitude (13). Benthic foraminiferal assemblages declined in diversity with postexcursion assemblages similar to the low-diversity post-PETM ones (13)(14)(15), but without significant extinction.…”