Episodic fresh surface waters in the Eocene Arctic Ocean

Brinkhuis, Henk; Schouten, Stefan; Collinson, Margaret E.; Sluijs, Appy; Damsté, Jaap S Sinninghe; Dickens, Gerald R.; Huber, Matthew; Cronin, Thomas M.; Onodera, Jonaotaro; Takahashi, Kozo; Bujak, J P; Stein, Rüdiger; Burgh, J. van der; Eldrett, James S; Harding, Ian C.; Lotter, André F.; Sangiorgi, Francesca; Cittert, Han van Konijnenburg-van; Leeuw, J.W. de; Matthießen, Jens; Backman, Jan; Moran, Kathryn; Scientists, Expedition

doi:10.1038/nature04692

Cited by 293 publications

(325 citation statements)

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“…Early/Middle Eocene sediments from the central Arctic Ocean were found to contain abundant remains of Azolla megaspores and microspore massulae as well as Azolla-specific biomarkers (27,28). The fact that the free floating aquatic fern Azolla grew and reproduced in the Eocene Arctic (27,29) is strong evidence that the surface waters of the Arctic Basin freshened considerably as Azolla cannot thrive at high salinities (>3‰; 29). At the same time, bottom waters appear to have remained saline, facilitating deep-water anoxia and salinity stratification (27,29,30).…”

Section: Discussionmentioning

confidence: 91%

Fossilized glycolipids reveal past oceanic N ₂ fixation by heterocystous cyanobacteria

Bauersachs

Speelman

Hopmans

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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N 2 -fixing cyanobacteria play an essential role in sustaining primary productivity in contemporary oceans and freshwater systems. However, the significance of N 2 -fixing cyanobacteria in past nitrogen cycling is difficult to establish as their preservation potential is relatively poor and specific biological markers are presently lacking. Heterocystous N 2 -fixing cyanobacteria synthesize unique long-chain glycolipids in the cell envelope covering the heterocyst cell to protect the oxygen-sensitive nitrogenase enzyme. We found that these heterocyst glycolipids are remarkably well preserved in (ancient) lacustrine and marine sediments, unambiguously indicating the (past) presence of N 2 -fixing heterocystous cyanobacteria. Analysis of Pleistocene sediments of the eastern Mediterranean Sea showed that heterocystous cyanobacteria, likely as epiphytes in symbiosis with planktonic diatoms, were particularly abundant during deposition of sapropels. Eocene Arctic Ocean sediments deposited at a time of large Azolla blooms contained glycolipids typical for heterocystous cyanobacteria presently living in symbiosis with the freshwater fern Azolla, indicating that this symbiosis already existed in that time. Our study thus suggests that heterocystous cyanobacteria played a major role in adding "new" fixed nitrogen to surface waters in past stratified oceans.nitrogen fixation | intact polar lipids | cyanobacterial biomarkers | symbiosis | saproprel

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Section: Discussionmentioning

confidence: 91%

Fossilized glycolipids reveal past oceanic N ₂ fixation by heterocystous cyanobacteria

Bauersachs

Speelman

Hopmans

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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“…According to Brinkhuis et al [2006, p. 607], the Arctic sediments show cyclic oscillations that ''may reflect orbital forcing of the 100-ka eccentricity cycle, suggesting that the periodical freshening of the Arctic Ocean was astronomically modulated.'' The abundance of Azolla, and its occurrence together with the remains of other brackish/marine organisms, suggested that the salinity of surface seawater in the Azolla Ocean was low as a result of high precipitation and restricted exchange with surrounding seas [Brinkhuis et al, 2006]. The demonstration of freshening has relevance for similar suggestions applied to the Toarcian.…”

Section: Impact Of Restriction On Re-os Datingmentioning

confidence: 88%

“…[63] The Azolla sediments show alternating laminations composed of dark, organic-rich, and lighter, siliceous, microlayers that are interpreted to reflect annual, seasonal, influences [Brinkhuis et al, 2006]. Similar laminations occur in the Toarcian black shales of Yorkshire, United Kingdom, and were taken to be annual varves [Hallam, 1997].…”

Section: Impact Of Restriction On Re-os Datingmentioning

confidence: 99%

“…Younger analogs of the restricted Early Toarcian sea might be the eastern Mediterranean, where sapropels formed in response to surface freshening and nutrient supply [Rohling, 1994], or the Arctic, high-latitude, Azolla Ocean of middle Eocene time. Examining the latter, the freshwater/ brackish water fern Azolla flourished in the Arctic Ocean in a low-salinity surface layer that extended over an 800,000 year period, depositing sediments that reach up to 5% TOC [Brinkhuis et al, 2006]. According to Brinkhuis et al [2006, p. 607], the Arctic sediments show cyclic oscillations that ''may reflect orbital forcing of the 100-ka eccentricity cycle, suggesting that the periodical freshening of the Arctic Ocean was astronomically modulated.''…”

Section: Impact Of Restriction On Re-os Datingmentioning

confidence: 99%

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Basinal restriction, black shales, Re‐Os dating, and the Early Toarcian (Jurassic) oceanic anoxic event

et al. 2008

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[1] Profiles of Mo/total organic carbon (TOC) through the Lower Toarcian black shales of the Cleveland Basin, Yorkshire, United Kingdom, and the Posidonia shale of Germany and Switzerland reveal water mass restriction during the interval from late tenuicostatum Zone times to early bifrons Zone times, times which include that of the putative Early Toarcian oceanic anoxic event. The degree of restriction is revealed by crossplots of Mo and TOC concentrations for the Cleveland Basin, which define two linear arrays with regression slopes (ppm/%) of 0.5 and 17. The slope of 0.5 applies to sediment from the upper semicelatum and exaratum Subzones. This value, which is one tenth of that for modern sediments from the Black Sea (Mo/TOC regression slope 4.5), reveals that water mass restriction during this interval was around 10 times more severe than in the modern Black Sea; the renewal frequency of the water mass was between 4 and 40 ka. The Mo/TOC regression slope of 17 applies to the overlying falciferum and commune subzones: the value shows that restriction in this interval was less severe and that the renewal frequency of the water mass was between 10 and 130 years. The more restricted of the two intervals has been termed the Early Toarcian oceanic anoxic event but is shown to be an event caused by basin restriction local to NW Europe. Crossplots of Re, Os, and Mo against TOC show similar trends of increasing element concentration with increase in TOC but with differing slopes. Together with modeling of 187 Os/ 188 Os and d 98 Mo, the element/TOC trends show that drawdown of Re, Os, and Mo was essentially complete during upper semicelatum and exaratum Subzone times (Mo/TOC regression slope of 0.5). Drawdown sensitized the restricted water mass to isotopic change forced by freshwater mixing so that continental inputs of Re, Os, and Mo, via a low-salinity surface layer, created isotopic excursions of up to 1.3% in d 98 Mo and up to 0.6% for 187 Os/ 188 Os. Restriction thereby compromises attempts to date Toarcian black shales, and possibly all black shales, using Re-Os chronology and introduces a confounding influence in the attempts to use d 98 Mo and initial 187 Os/ 188 Os for palaeo-oceanographic interpretation.

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“…A shift to an 'icehouse' Arctic Later in the record, at ,49 Myr ago, a massive occurrence of glochidia (hair-like projections) and massulae of the fresh-water hydropterid fern Azolla confirms the presence of fresh surface water conditions 16 with cooler TEX 86 temperatures of ,10 8C (ref. 17). A concomitant occurrence of ebridian and silicoflagellate and diatom assemblages, requiring marine to brackish salinities, points to seasonally changing stratification regimes (Fig.…”

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confidence: 99%

The Cenozoic palaeoenvironment of the Arctic Ocean

Moran¹,

Backman²,

Brinkhuis³

et al. 2006

Nature

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The history of the Arctic Ocean during the Cenozoic era (0-65 million years ago) is largely unknown from direct evidence. Here we present a Cenozoic palaeoceanographic record constructed from >400 m of sediment core from a recent drilling expedition to the Lomonosov ridge in the Arctic Ocean. Our record shows a palaeoenvironmental transition from a warm 'greenhouse' world, during the late Palaeocene and early Eocene epochs, to a colder 'icehouse' world influenced by sea ice and icebergs from the middle Eocene epoch to the present. For the most recent ∼14 Myr, we find sedimentation rates of 1-2 cm per thousand years, in stark contrast to the substantially lower rates proposed in earlier studies; this record of the Neogene reveals cooling of the Arctic that was synchronous with the expansion of Greenland ice (∼3.2 Myr ago) and East Antarctic ice (∼14 Myr ago). We find evidence for the first occurrence of ice-rafted debris in the middle Eocene epoch (∼45 Myr ago), some 35 Myr earlier than previously thought; fresh surface waters were present at ∼49 Myr ago, before the onset of ice-rafted debris. Also, the temperatures of surface waters during the Palaeocene/Eocene thermal maximum (∼55 Myr ago) appear to have been substantially warmer than previously estimated. The revised timing of the earliest Arctic cooling events coincides with those from Antarctica, supporting arguments for bipolar symmetry in climate change. © 2006 Nature Publishing Group

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Episodic fresh surface waters in the Eocene Arctic Ocean

Cited by 293 publications

References 28 publications

Fossilized glycolipids reveal past oceanic N ₂ fixation by heterocystous cyanobacteria

Fossilized glycolipids reveal past oceanic N ₂ fixation by heterocystous cyanobacteria

Basinal restriction, black shales, Re‐Os dating, and the Early Toarcian (Jurassic) oceanic anoxic event

The Cenozoic palaeoenvironment of the Arctic Ocean

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Episodic fresh surface waters in the Eocene Arctic Ocean

Cited by 293 publications

References 28 publications

Fossilized glycolipids reveal past oceanic N 2 fixation by heterocystous cyanobacteria

Fossilized glycolipids reveal past oceanic N 2 fixation by heterocystous cyanobacteria

Basinal restriction, black shales, Re‐Os dating, and the Early Toarcian (Jurassic) oceanic anoxic event

The Cenozoic palaeoenvironment of the Arctic Ocean

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Product

Resources

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Fossilized glycolipids reveal past oceanic N ₂ fixation by heterocystous cyanobacteria

Fossilized glycolipids reveal past oceanic N ₂ fixation by heterocystous cyanobacteria