Calcareous nannofossils from the Paleogene equatorial Pacific (IODP Expedition 320 Sites U1331-1334).

Bown, PR; T, Dunkley Jones

doi:10.58998/jnr2023

Cited by 42 publications

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“…D. bisectus (<10 μm) and D. bisectus (>10 μm), with mean values of 4.2% and 1.8%, respectively. All these taxonomic entities have been differentiated due to the distinct behavior documented in the literature (e.g., Bown & Dunkley Jones, 2012; Wei & Wise, 1990). Cyclicargolithus shows a distinct up‐core abundance increase from ∼2% in the lower part of the sections (below 217.36 m) to 8.4% in the overlying part of the section (Figure 2).…”

Section: Resultsmentioning

confidence: 99%

“…Relative abundance patterns (%) of the total assemblage were obtained counting at least 300 specimens per sample. The taxonomy follows that presented by Aubry (1984, 1988, 1989), Perch‐Nielsen (1985), Bown (2005), Bown and Dunkley Jones (2012), and Newsam et al. (2017), except for Dictyococcites and Reticulofenestra for which we use the taxonomy expressed by Agnini et al.…”

Section: Methodsmentioning

confidence: 99%

“…Relative abundance patterns (%) of the total assemblage were obtained counting at least 300 specimens per sample. The taxonomy follows that presented by Aubry (1984Aubry ( , 1988Aubry ( , 1989, Perch-Nielsen (1985), Bown (2005), Dunkley Jones (2012), andNewsam et al (2017), except for Dictyococcites and Reticulofenestra for which we use the taxonomy expressed by Agnini et al (2014). Key calcareous nannofossil datums can be placed into the biostratigraphic frame using three different Cenozoic zonation schemes, NP (Martini, 1971), CP (Okada & Bukry, 1980), and CN of Agnini et al (2014).…”

Section: Calcareous Nannofossils Datamentioning

confidence: 99%

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Calcareous Nannofossils and Paleoclimatic Evolution Across the Eocene‐Oligocene Transition at IODP Site U1509, Tasman Sea, Southwest Pacific Ocean

Viganò,

Dallanave,

Alegret

et al. 2024

Paleoceanog and Paleoclimatol

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The Eocene‐Oligocene transition (EOT; ∼34 Ma) was one of the most prominent global cooling events of the Cenozoic, coincident with the emergence of continental‐scale ice‐sheets on Antarctica. Calcareous nannoplankton experienced significant assemblage turnover at a time of long‐term surface ocean cooling and trophic conditions, suggesting cause‐effect relationships between Antarctic glaciation, broader climate changes, and the response of phytoplankton communities. To better evaluate the timing and nature of these relationships, we generated calcareous nannofossil and geochemical data sets (δ18O, δ13C and %CaCO3) over a ∼5 Myr stratigraphic interval recovered across the EOT from IODP Site U1509 in the Tasman Sea, South Pacific Ocean. Based on trends observed in the calcareous nannofossil assemblages, there was an overall decline of warm‐oligotrophic communities, with a shift toward taxa better adapted to cooler more eutrophic conditions. Assemblage changes indicate four distinct phases caused by temperature decrease and variations in paleocurrents: late Eocene warm‐oligotrophic phase, precursor diversity‐decrease phase, early Oligocene cold‐eutrophic phase, and a steady‐state cosmopolitan phase. The most prominent shift in the assemblages occurred during the ∼550 kyr‐long precursor diversity‐decrease phase, which has relatively high bulk δ18O and %CaCO3 values, and predates the phase of maximum glacial expansion (Earliest Oligocene Glacial Maximum–EOGM).

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Calcareous Nannofossils Datamentioning

confidence: 99%

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Calcareous Nannofossils and Paleoclimatic Evolution Across the Eocene‐Oligocene Transition at IODP Site U1509, Tasman Sea, Southwest Pacific Ocean

Viganò,

Dallanave,

Alegret

et al. 2024

Paleoceanog and Paleoclimatol

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Calcareous nannofossil biostratigraphy of the External Dinarides flysch (Vrčić‐Staravasa Pag Island, Croatia): A key to an Eocene tectono‐stratigraphic and paleoenvironmental interpretation

et al. 2019

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It is largely accepted that in the Dinaric shallow foredeep basin, the onset of Cenozoic synorogenic sedimentation is diachronous along strike and shows orogenparallel southward younging, creating a large uncertainty in the age of the Dalmatian flysch. Calcareous nannofossil biostratigraphy was studied to investigate a turbiditic succession exposed in Pag Island (Croatia) with the main purpose of constraining its age, which is still a matter of debate. The age assignment for the turbiditic deposition bears important implications for better understanding of the geodynamic and paleoenvironmental evolution of the External Dinarides.We logged a well-exposed sedimentary section in the south-western limb of the Pag anticline and performed calcareous nannofossil quantitative analyses revealing a high species diversity and abundant assemblage. The age diagnostic species indicate CNE14-CNE15 biozones, suggesting that flysch deposition occurred in the Lutetian-Bartonian. This age can be further restricted to the CNE14 (42.37-40.51 Ma) by means of the lowest occurrence of Reticulofenestra reticulata and the highest occurrence of Sphenolithus furcatolithoides. Vertical facies variation and paleoecological indications suggest an increase in paleobathymetric depth during deposition. Our data support a post-Lutetian age of folding and thrusting for the Pag Island region and suggest a relatively short time span during the middle-late Eocene period for the main contractional stage in this sector of the External Dinarides. This result has important implications for the evolution of the Dinaride foreland basin system in Cenozoic times. K E Y W O R D S calcareous nannofossils, Dalmatian flysch, Eocene, External Dinarides, Pag anticline

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Erosion and reworking of Pacific sediments near the Eocene‐Oligocene boundary

Moore

2013

Paleoceanography

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[1] The Eocene-Oligocene (E/O) boundary interval marks one of the largest and most rapid changes in climate during the last 50 Myr. Because of a very shallow calcium carbonate compensation depth in the Eocene, as well as the reworking of sediments and hiatuses in the boundary zone, it has also been one of the most difficult stratigraphic boundaries to study in deep water marine sections, especially in the Pacific Ocean. Recently, three drill sites have recovered complete sections of the E/O boundary interval in the tropical Pacific. A detailed study of these sections shows a series of pulses of reworked older radiolarians in the upper Eocene and lowermost Oligocene. The two largest pulses are coincident with the two sharp steps in carbon and oxygen isotope values that bracket the E/O boundary. Several smaller peaks in reworked material precede these two maxima. It is proposed that immixing of the older radiolarian species results from erosion and redeposition, possibly linked to pulses of new bottom water formation and the formation of a deep pycnocline.

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Calcareous nannofossils from the Paleogene equatorial Pacific (IODP Expedition 320 Sites U1331-1334).

Cited by 42 publications

References 0 publications

Calcareous Nannofossils and Paleoclimatic Evolution Across the Eocene‐Oligocene Transition at IODP Site U1509, Tasman Sea, Southwest Pacific Ocean

Calcareous Nannofossils and Paleoclimatic Evolution Across the Eocene‐Oligocene Transition at IODP Site U1509, Tasman Sea, Southwest Pacific Ocean

Calcareous nannofossil biostratigraphy of the External Dinarides flysch (Vrčić‐Staravasa Pag Island, Croatia): A key to an Eocene tectono‐stratigraphic and paleoenvironmental interpretation

Erosion and reworking of Pacific sediments near the Eocene‐Oligocene boundary

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