Arctic late Paleocene–early Eocene paleoenvironments with special emphasis on the Paleocene‐Eocene thermal maximum (Lomonosov Ridge, Integrated Ocean Drilling Program Expedition 302)

Abstract

[1] We reconstruct the latest Paleocene and early Eocene ($57-50 Ma) environmental trends in the Arctic Ocean and focus on the Paleocene-Eocene thermal maximum (PETM) ($55 Ma), using strata recovered from the Lomonosov Ridge by the Integrated Ocean Drilling Program Expedition 302. The Lomonosov Ridge was still partially subaerial during the latest Paleocene and earliest Eocene and gradually subsided during the early Eocene. Organic dinoflagellate cyst (dinocyst) assemblages point to brackish and productive surface waters throughout the latest Paleocene and early Eocene. Dinocyst assemblages are cosmopolitan during this time interval, suggesting warm conditions, which is corroborated by TEX 86 0 -reconstructed temperatures of 15°-18°C. Inorganic geochemistry generally reflects reducing conditions within the sediment and euxinic conditions during the upper lower Eocene. Spectral analysis reveals that the cyclicity, recorded in X-ray fluorescence scanning Fe data from close to Eocene thermal maximum 2 ($53 Ma, presence confirmed by dinocyst stratigraphy), is related to precession. Within the lower part of the PETM, proxy records indicate enhanced weathering, runoff, anoxia, and productivity along with sea level rise. On the basis of total organic carbon content and variations in sediment accumulation rates, excess organic carbon burial in the Arctic Ocean appears to have contributed significantly to the sequestration of injected carbon during the PETM.

Eustatic variations during the Paleocene‐Eocene greenhouse world

“…Obliquity related cycles, however, are either relatively weak (compared to precession) or absent in upper Paleocene and lower Eocene marine records [e.g., Röhl et al, 2003;Lourens et al, 2005;Westerhold et al, 2007;Sluijs et al, 2008], questioning the existence of the hypothesized ice sheets and their contribution to sea level changes.…”

“…[37] Uppermost Paleocene-lowermost Eocene sediments on Lomonosov Ridge were deposited on the shelf close to land, as indicated by high abundances of terrestrial components, including plant remains and large spores [Backman et al, 2006;Sluijs et al, 2006Sluijs et al, , 2008. Cenozoic marine sedimentation at this site commenced at least 1 Ma prior to the PETM [Backman et al, 2006].…”

“…In particular, some authors Schmitz and Pujalte, 2003;Schmitz et al, 2004] have argued that lithological changes across the PETM support a major sea level fall, whereas in other cases microfossil and geochemical data has been used to suggest the opposite trend . One recently acknowledged problem is that sediment supply to continental margins varied significantly during the early Paleogene, especially across the hyperthermals [e.g., Nicolo et al, 2007;Sluijs et al, 2008] (Figure 2), and this could influence stratigraphic interpretations Steckler et al, 1988].…”

Expanding the Cenozoic paleoceanographic record in the Central Arctic Ocean: IODP Expedition 302 Synthesis

“…Biostratigraphic resolution in these middle Miocene to Recent sediments is, therefore, at a minimum, especially when the lack of calcarous plankton below 20 mbsf and the total absence of biosilica are considered (Figure 4). [58] the presence of the dinoflagellate cyst species Cerodinium wardenense. In the ACEX record, the ETM2 event was first proposed by [47] based on a carbon isotope study on bulk organic material.…”

Modeling the influence of a reduced equator-to-pole sea surface temperature gradient on the distribution of water isotopes in the Early/Middle Eocene

“…While earlier in the Eocene (from 55 to 50 Ma) temperature gradients may have been even lower (e.g. Pearson et al, 2007;Sluijs et al, 2008), data coverage in the Azolla interval centered near 49 Ma is more complete and we thus focus on that interval.…”