Major shifts in calcareous phytoplankton assemblages through the Eocene‐Oligocene transition of Tanzania and their implications for low‐latitude primary production

Jones, Tom Dunkley; Bown, Paul R.; Pearson, Paul Nicholas; Wade, Bridget S.; Coxall, Helen K.; Lear, C. H.

doi:10.1029/2008pa001640

Cited by 79 publications

(83 citation statements)

References 91 publications

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“…[], and Raffi et al . []; nevertheless, caution should be used as this genus is considered to be adaptable to mesotrophic conditions (e.g., in the Messinian in the Mediterranean [ Wade and Bown , ] and in Tanzania [ Dunkley Jones et al ., ]). However, sphenolith counts in our oligotrophic curve are so low that their removal would not alter the overall trend of the oligotrophic taxa curve.…”

Section: Methodsmentioning

confidence: 99%

Middle Eocene to Late Oligocene Antarctic glaciation/deglaciation and Southern Ocean productivity

et al. 2014

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During the Eocene-Oligocene transition, Earth cooled significantly from a greenhouse to an icehouse climate. Nannofossil assemblages from Southern Ocean sites enable evaluation of paleoceanographic changes and, hence, of the oceanic response to Antarctic ice sheet evolution during the Eocene and Oligocene. A combination of environmental factors such as sea surface temperature and nutrient availability is recorded by the nannofossil assemblages of and can be interpreted as responses to the following changes. A cooling trend, started in the Middle Eocene, was interrupted by warming during the Middle Eocene Climatic optimum and by short cooling episodes. The cooling episode at 39.6 Ma preceded a shift toward an interval that was dominated by oligotrophic nannofossil assemblages from~39.1 to~36.2 Ma. We suggest that oligotrophic conditions were associated with increased water mass stratification, low nutrient contents, and high efficiency of the oceanic biological pump that, in turn, promoted sequestration of carbon from surface waters, which favored cooling. After 36.2 Ma, we document a large synchronous surface water productivity turnover with a dominant eutrophic nannofossil assemblage that was accompanied by a pronounced increase in magnetotactic bacterial abundance. This turnover reflects a response of coccolithophorids to changed nutrient inputs that was likely related to partial deglaciation of a transient Antarctic ice sheet and/or to iron delivery to the sea surface. Eutrophic conditions were maintained throughout the Oligocene, which was characterized by a nannofossil assemblage shift toward cool conditions at the Eocene-Oligocene transition. Finally, a warm nannofossil assemblage in the Late Oligocene indicates a warming phase.

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Section: Methodsmentioning

confidence: 99%

Middle Eocene to Late Oligocene Antarctic glaciation/deglaciation and Southern Ocean productivity

et al. 2014

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“…Sediment records from the Ceara Rise (Site 925) reveal a shift in the relative abundance in siliceous versus carbonate productivity and preservation across the EOT in western equatorial Atlantic [ Nilsen et al ., ] and are accompanied by evidence for an increase in the nutrient availability at low latitudes [ Dunkley Jones et al ., ]. Globally, the EOT is associated with changes in global phytoplankton production resulting from the advent of glaciation and intensification of bottom water circulation leading to an increase in diatom diversity and abundance [ Suto et al ., ] and a decline in coccolithophorids and dinoflagellates [ Falkowski et al ., ].…”

Section: Timing Of Innovation In Alkenone Biosynthesis and Climate Chmentioning

confidence: 99%

Climatic influences on the Paleogene evolution of alkenones

Brassell

2014

Paleoceanography

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Application of the alkenone paleotemperature proxy (U K' 37 ) for marine sediments is typically constrained by three factors: (i) an absence of alkatrienones in sediments deposited where ocean temperatures exceed~28°C, (ii) loss of alkenones in thermally altered sediments, and (iii) poor preservation of alkenone signals due to oxidative degradation. In addition, there appears to be a temporal limit on the occurrence of alkatrienones, which are conspicuously absent in all alkenone-containing sediments from the early Aptian to the immediate aftermath of the Early Eocene Climatic Optimum (EECO) when they first appeared in Arctic Ocean sediments. Compilation of reported and previously unpublished alkenone distributions for the Paleogene coupled with assessment of co-occurring calcareous nannoplankton genera within the Noelaerhabdaceae provide evidence that evolutionary developments in alkenone occurrences include biosynthetic responses likely triggered by climate change. The timing of emergence of alkatrienones post-EECO and their subsequent appearance at all latitudes during the middle Eocene accompanies expansion of the calcareous nannoplankton genus Reticulofenestra coincident with significant climate-driven changes in oceanic conditions, including (i) modification of trophic structure associated with weakened thermal stratification, (ii) higher productivity facilitated by enhanced nutrient influx, and (iii) changes in seasonality, initially at high latitudes, related to greater latitudinal temperature gradients. Collectively, these changes would serve to favor eurythermal/eurytrophic algae, like Reticulofenestra, with a biomechanism to store energy through production of lipid bodies rich in alkenones during episodes of higher nutrient availability. This ability likely enhanced the viability of this marine haptophyte when nutrients were limiting, ultimately ensuring its evolutionary success.

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“…Work on these three sites has revealed the multifaceted problems in resolving the E/O boundary, even when using paleomagnetic stratigraphy, as well as the more highly resolved biostratigraphies now available. First, the paleomagnetic stratigraphy indicates that the E/O boundary lies just below the base of Chron C13n, which coincides with the base of the second (youngest) step in lithologic and isotopic changes [ Dunkley Jones et al ., ; Coxall and Wilson , ]. The boundary itself is contained within the uppermost part of Chron C13r [ Coxall et al ., ].…”

Section: Introductionmentioning

confidence: 99%

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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Major shifts in calcareous phytoplankton assemblages through the Eocene‐Oligocene transition of Tanzania and their implications for low‐latitude primary production

Cited by 79 publications

References 91 publications

Middle Eocene to Late Oligocene Antarctic glaciation/deglaciation and Southern Ocean productivity

Middle Eocene to Late Oligocene Antarctic glaciation/deglaciation and Southern Ocean productivity

Climatic influences on the Paleogene evolution of alkenones

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

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