Search

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 TEX86′-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.

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 TEX86′-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.

The distributions of sterols and organic-walled dinoflagellate cysts (dinocysts) in five NW Adriatic Sea surface sediment samples were investigated. Samples are representative of areas differently influenced by freshwater inputs, mainly coming from the Po River. All the investigated samples exhibit the same suite of principal sterols, with cholest-5-en-3β-ol (cholesterol), 4α,23,24-trimethyl-5α-cholest-22E-en-3β-ol (dinosterol), 24-ethylcholest-5-en-3β-ol (sitosterol) and 24-methylcholesta-5,22E-dien-3β-ol (brassicasterol or epibrassicasterol) displaying the highest concentrations and relative abundances. The distribution of sterols in the samples is not related to their distance from the coast and/or with the C/N ratios and suggests a prevalent input of marine, autochthonous organic matter in the surface sediments. In particular, the high abundance of dinosterol underlines the importance of dinoflagellate productivity in this area and its contribution to the organic matter in sediments. However, absolute and relative abundances of dinosterol do not follow the trend observed for dinocyst concentrations in the investigated samples, with the exception of Spiniferites spp. cysts and cysts produced by Gonyaulax species.