Early Eocene palaeoceanography and palaeoclimatology of the eastern North Atlantic: stable isotope results for DSDP Hole 550

Abstract

High-resolution oxygen and carbon isotope records for benthonic and planktonic foraminifera have been established through the early Eocene at DSDP Site 550, Goban Spur in the North Atlantic. Benthonic stable isotopic records from Site 550 (estimated palaeodepth c. 4000 m) represent the first documentation of actual deep water properties during the early Eocene.At Site 550 in the earliest Eocene (end of NP10 Zone), a 0.5%o vertical 5180 (i.e. thermal) gradient between subsurface and bottom water was eliminated, probably reflecting upward displacement of subsurface water by intermediate and deep water. Thereafter vertical isothermal conditions prevailed for the rest of the early Eocene. This is consistent with earlier findings suggesting unusually low vertical and latitudinal temperature gradients in the early Eocene ocean. A comparison of the isotopic records from Site 550 and nearby DSDP Site 401 (palaeodepth 1800 m), reflecting intermediate water properties, confirms the isothermal nature of the water column in the eastern North Atlantic. This is in contrast to earlier findings for the Antarctic region (ODP Sites 689 and 690) in the early Eocene, where supposedly warm bottom waters originating in low latitudes were overlain by cooler intermediate waters originating in high latitudes. Both the oxygen and the carbon isotopic records for Sites 550 and 401 indicate that the eastern North Atlantic region was influenced by a single source of intermediate-to-deep water through most of the early Eocene. The benthonic 5180 and 813C values for Site 550 are generally low compared with coeval sections worldwide, indicating that during most of the early Eocene the North Atlantic was dominated by warm and nutrient-enriched deep water formed in a low latitude region.The earliest stages of the long-term cooling trend, which characterizes the second part of the Paleogene, can be traced by a 2~ decrease in bottom water temperatures across the NPI3-NP14 transition at both Sites 550 and 401.

Early Eocene environmental development in the northern Peri-Tethys (Aktulagay, Kazakhstan) based on benthic foraminiferal assemblages and stable isotopes (O, C)

“…This time period can be correlated to unit B2. With the limits of our low resolution, isotopic correlation to the isotopic deep-sea record of Charisi and Schmitz (1996) appears to confirm this interpretation (Fig. 4).…”

A transient deep‐sea circulation switch during Eocene Thermal Maximum 2

“…Our case is supported by diverse global records: As in Site 550, Site 1209 (Shatsky Rise, central equatorial Pacific) displays a collapse of the vertical δ 18 O gradient between Subbotina (thermocline dwelling) and benthic foraminifera, initiated at the ETM2 and lasting throughout the early Eocene climatic optimum (EECO) [ Charisi and Schmitz , ; Dutton et al ., ]. This shift has been linked to a change in ocean circulation [ Dutton et al ., ].…”

“…Additional N . truempyi data for Site 550 (green dots) from Charisi and Schmitz []. Carbonate content from Zachos et al .…”

Could changing ocean circulation have destabilized methane hydrate at the Paleocene/Eocene boundary?

“…However, because we compare all isotopic temperatures to those predicted by the model, we make an indirect comparison across species. Published estimates of the isotopic offset between Cibicidoides and Nuttallides vary within a relatively narrow range of <0.2‰ [ Shackleton et al , 1984; Katz and Miller , 1991; Pak and Miller , 1992], but estimated offsets between Oridorsalis and Nuttallides vary by at least 1.2‰ [ Shackleton et al , 1984; Charisi and Schmitz , 1996]. Work by M. E. Katz et al (Paleocene‐Eocene benthic foraminiferal isotopes: Species reliability and interspecies correction factors, submitted to Paleoceanography , 2001) should produce a consistent set of correction factors for all species used in this study.…”

“…However, because we compare all isotopic temperatures to those predicted by the model, we make an indirect comparison across species. Published estimates of the isotopic offset between Cibicidoides and Nuttallides vary within a relatively narrow range of <0.2% [Shackleton et al, 1984;Katz and Miller, 1991;Pak an'd Miller, 1992], but estimated offsets between Oridorsalis and Nuttallides vary by at least 1.2% [Shackleton et al, 1984;Charisi and Schmitz, 1996]. Work by [20] As noted in section 2.1, a reasonable fit between model high-latitude sea surface temperatures and those estimated from latest Paleocene planktonic data was achieved by tuning the AGCM greenhouse gas concentrations and slab ocean heat transport coefficient in the atmospheric model from which ocean model forcings were derived.…”