Phanerozoic record of plate tectonic control of seawater chemistry and carbonate sedimentation

Steuber, Thomas; Veizer, Ján

doi:10.1130/0091-7613(2002)030<1123:proptc>2.0.co;2

Cited by 177 publications

(120 citation statements)

References 36 publications

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“…The resultant mean ratio of 5·35 0·64 mmol/mol is comparable with values calculated by Steuber & Veizer (2002) for the Early Permian seas.…”

Section: Elemental Datasupporting

confidence: 71%

“…It is therefore more plausible to suggest that the pristine brachiopods analysed in this study are recording the late Sakmarian seawater signature in the region. The Sr/Ca ratios are typical of the Early Permian seas elsewhere (Steuber & Veizer 2002) and preliminary data for brachiopods from the equivalent beds in the subsurface Haushi limestone (Angiolini et al, unpublished data) indicate similar or slightly more negative Sr isotope ratios. The brachiopod assemblage in the subsurface Haushi limestone is consistent with a deeper marine environment, more distant from the source of terrigenous input.…”

Section: Interpretation and Discussionmentioning

confidence: 93%

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Lower Permian brachiopods from Oman: their potential as climatic proxies

Angiolini¹,

Darbyshire

Stephenson

et al. 2007

Earth and Environmental Science Transactions of the Royal Socie

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The Lower Permian of the Haushi basin, Interior Oman (Al Khlata Formation to Saiwan Formation/lower Gharif member) records climate change from glaciation, through marine sedimentation in the Haushi sea, to subtropical desert. To investigate the palaeoclimatic evolution of the Haushi Sea we used O, C, and Sr isotopes from 31 brachiopod shells of eight species collected bed by bed within the type-section of the Saiwan Formation. We assessed diagenesis by scanning electron microscopy of ultrastructure, cathodoluminescence, and geochemistry, and rejected fifteen shells not meeting specific preservation criteria. Spiriferids and spiriferinids show better preservation of the fibrous secondary layer than do orthotetids and productids and are therefore more suitable for isotopic analysis. 18 O of 3·7 to 3·1‰ from brachiopods at the base of the Saiwan Formation are probably related to glacial meltwater. Above this, an increase in 18 O may indicate ice accumulation elsewhere in Gondwana or more probably that the Haushi sea was an evaporating embayment of the Neotethys Ocean. 13 C varies little and is within the range of published data: its trend towards heavier values is consistent with increasing aridity and oligotrophy. Saiwan Sr isotope signatures are less radiogenic than those of the Sakmarian LOWESS seawater curve, which is based on extrapolation between few data points. In the scenario of evaporation in a restricted Haushi basin, the variation in Sr isotope composition may reflect a fluvial component.

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“…The resultant mean ratio of 5·35 0·64 mmol/mol is comparable with values calculated by Steuber & Veizer (2002) for the Early Permian seas.…”

Section: Elemental Datasupporting

confidence: 71%

Section: Interpretation and Discussionmentioning

confidence: 93%

Lower Permian brachiopods from Oman: their potential as climatic proxies

Angiolini¹,

Darbyshire

Stephenson

et al. 2007

Earth and Environmental Science Transactions of the Royal Socie

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“…Most evidence from altered ophiolite assemblages and the fossil record indicate elevated [Sr] in seawater during times of elevated [Ca] (20)(21)(22), with fairly small overall changes to the seawater Sr/Ca ratio. However, lower than modern Sr/Ca ratios for the period between 30-180 Ma have also been proposed based on analyses of carbonate veins in altered oceanic crust (23).…”

Section: Paleoseawater Chemical Variationsmentioning

confidence: 99%

“…Our model for fluid evolution in MOR systems, which is meant to describe the global average MOR hydrothermal fluid evolution, can be expressed in four steps (SI Appendix, This model allows us to make predictions about how differences in seawater composition in the geologic past will be manifest as changes in the extent of Ca, Mg, SO 4 , and Sr exchange between seawater and oceanic crust, ultimately evidenced by changes in the (20,24), but are subject to uncertainties. Lower estimates of seawater Sr/Ca (23) lead to approximately modern Sr concentrations from 30 to 180 Ma.…”

Section: Paleoseawater Chemical Variationsmentioning

confidence: 99%

“…For the purpose of evaluating our model we have constructed a notional Phanerozoic seawater [Sr] curve ( Fig. 1) based on combining the Sr/ Ca record from invertebrates (20) and benthic foraminifera (24) with the record for seawater [Ca] (adopting the assumptions of Significance Circulation of seawater through midocean ridges results in largescale chemical transfer between the solid Earth and oceans. Driven by magmatic heat, seawater undergoes hydrothermal reactions that affect the concentrations of Mg, Ca, SO 4 , and Sr in the oceans over millions of years.…”

Section: Paleoseawater Chemical Variationsmentioning

confidence: 99%

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Effect of paleoseawater composition on hydrothermal exchange in midocean ridges

Antonelli

Pester

Brown

et al. 2017

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

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Variations in the Mg, Ca, Sr, and SO 4 concentrations of paleoseawater can affect the chemical exchange between seawater and oceanic basalt in hydrothermal systems at midocean ridges (MOR). We present a model for evaluating the nature and magnitude of these previously unappreciated effects, using available estimates of paleoseawater composition over Phanerozoic time as inputs and 87 Sr/ 86 Sr of ophiolite epidosites and epidote-quartz veins as constraints. The results suggest that modern hydrothermal fluids are not typical due to low Ca and Sr relative to Mg and SO 4 in modern seawater. At other times during the last 500 million years, particularly during the Cretaceous and Ordovician, hydrothermal fluids had more seawater-derived Sr and Ca, a prediction that is supported by Sr isotope data. The predicted 87 Sr/ 86 Sr of vent fluids varies cyclically in concert with ocean chemistry, with some values much higher than the modern value of ∼0.7037. The seawater chemistry effects can be expressed in terms of the transfer efficiency of basaltic Ca and Sr to seawater in hydrothermal systems, which varies by a factor of ∼1.6 over the Phanerozoic, with minima when seawater Mg and SO 4 are low. This effect provides a modest negative feedback on seawater composition and 87 Sr/ 86 Sr changes. For the mid-Cretaceous, the low 87 Sr/ 86 Sr of seawater requires either exceptionally large amounts of lowtemperature exchange with oceanic crust or that the weathering flux of continentally derived Sr was especially small. The model also has implications for MOR hydrothermal systems in the Precambrian, when low-seawater SO 4 could help explain low seawater 87 Sr/ 86 Sr.paleoseawater | Sr isotopes | hydrothermal systems | midocean ridges M idocean ridge (MOR) hydrothermal circulation, fueled by persistent heat from shallow magma reservoirs, is a key component in the long-term regulation of global climate and ocean chemistry (1). Hydrothermal fluids that emerge from these systems, at temperatures up to ∼400°C, are chemically distinct from seawater due to reactions with newly forming oceanic crust. Relative to seawater, fluids emanating from modern MOR hydrothermal systems are enriched in Ca and transition metals, have lower pH and Eh, and have little to no Mg and SO 4 (2-5).Hydrothermal circulation at MOR is dominated by two important chemical reactions: the removal of seawater SO 4 through mineral precipitation with seawater Ca, and the removal of seawater Mg through precipitation of hydroxy-silicate minerals (3, 6, 7). Seawater SO 4 is primarily lost through the formation of anhydrite (CaSO 4 ) early during hydrothermal circulation, as anhydrite precipitation occurs by simply heating seawater >130°C (8). There can also be minor losses of SO 4 through thermochemical sulfate reduction (9, 10) and bacterial processes.Seawater Mg is lost from hydrothermal fluids at both low and high temperatures, by exchange of seawater Mg for basaltic Ca through the transformation of primary igneous minerals to alteration phases such as montmorillonite ...

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The effects of secular calcium and magnesium concentration changes on the thermodynamics of seawater acid/base chemistry: Implications for Eocene and Cretaceous ocean carbon chemistry and buffering

Hain

Sigman

Higgins

et al. 2015

Global Biogeochemical Cycles

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] enhances "ion pairing," which increases seawater buffering by increasing the concentration ratio of total to "free" (uncomplexed) carbonate ion. An increase in [Ca 2+ ], however, also causes a decline in carbonate ion to maintain a given Ω, thereby overwhelming the ion pairing effect and decreasing seawater buffering. ], a doubling of atmospheric CO 2 would require less carbon addition to the ocean/atmosphere system than under modern seawater composition. Moreover, increasing seawater buffering since the Cretaceous may have been a driver of evolution by raising energetic demands of biologically controlled calcification and CO 2 concentration mechanisms that aid photosynthesis.

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Phanerozoic record of plate tectonic control of seawater chemistry and carbonate sedimentation

Cited by 177 publications

References 36 publications

Lower Permian brachiopods from Oman: their potential as climatic proxies

Lower Permian brachiopods from Oman: their potential as climatic proxies

Effect of paleoseawater composition on hydrothermal exchange in midocean ridges

The effects of secular calcium and magnesium concentration changes on the thermodynamics of seawater acid/base chemistry: Implications for Eocene and Cretaceous ocean carbon chemistry and buffering

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