Diagenetic effects on the distribution of uranium in live and Holocene corals from the Gulf of Aqaba

Lazar, Boáz; Enmar, Rivka; Schossberger, Michelle; Bar‐Matthews, M.; Halicz, Ludwik; Stein, Mordechai

doi:10.1016/j.gca.2004.03.029

Cited by 61 publications

(42 citation statements)

References 34 publications

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“…Enmar et al [2000] found the colony's interstitial pore water Sr concentration and Sr/Ca was lower than open reef water. Similarly, Lazar et al [2004] measured low U concentrations and U/Ca in pore waters. As reported by Enmar et al [2000] and Lazar et al [2004], secondary aragonite overgrowth could not be the only cause of the Sr and U deficits because the amount deposited was constrained by the observed alkalinity and enriched pore water Ca concentrations.…”

Section: Geochemical Impact On Coral Climate Tracersmentioning

confidence: 89%

“…Similarly, Lazar et al [2004] measured low U concentrations and U/Ca in pore waters. As reported by Enmar et al [2000] and Lazar et al [2004], secondary aragonite overgrowth could not be the only cause of the Sr and U deficits because the amount deposited was constrained by the observed alkalinity and enriched pore water Ca concentrations. Lazar et al [2004] concluded that the living coral polyps had to be taking up U in order to deplete pore waters within the colony skeleton.…”

Section: Geochemical Impact On Coral Climate Tracersmentioning

confidence: 89%

“…[19] The process of incongruent dissolution also provides an explanation for the porewater chemistry results reported by Enmar et al [2000] and Lazar et al [2004] from a Porites colony in the Red Sea containing obvious marine [Gagan et al, 1998], À0.062 mmol/mol Sr/Ca per°C [Alibert and McCulloch, 1997], À0.0465 mmol/mol U/Ca per°C [Min et al, 1995], and 0.16 mmol/mol Mg/Ca per°C [Sinclair et al, 1998]. C, Sr/Ca, U/Ca, Mg/Ca, and density.…”

Section: Geochemical Impact On Coral Climate Tracersmentioning

confidence: 98%

“…[3] Previous research has shown that early marine diagenesis influences coral skeletal geochemistry [e.g., Bar-Matthews et al, 1993;Enmar et al, 2000;Lazar et al, 2004;Müller et al, 2001Müller et al, , 2004Quinn and Taylor, 2006]. Positive anomalies were identified in diagenetically altered Porites sp.…”

Section: Introductionmentioning

confidence: 99%

“…Positive anomalies were identified in diagenetically altered Porites sp. skeletons containing secondary aragonite overgrowth for Sr/Ca [Castellaro et al, 1999;Enmar et al, 2000;Müller et al, 2001;Quinn and Taylor, 2006], U/Ca [Castellaro et al, 1999;Lazar et al, 2004], d…”

Section: Introductionmentioning

confidence: 99%

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Impact of skeletal dissolution and secondary aragonite on trace element and isotopic climate proxies in Porites corals

et al. 2007

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[1] Restricted zones of recent dissolution and secondary aragonite infilling were identified in a coral core collected in 1986 from a living massive Porites colony from the central Great Barrier Reef, Australia. Secondary aragonite needles, !20 mm long, cover skeletal surfaces deposited from 1972 to late 1974 and increase bulk density by 10%. Dissolution is observed above this zone, whereas older skeleton is pristine. We investigate the impact of both types of early marine diagenesis on skeletal geochemistry and coral paleoclimate reconstructions by comparison with similar records from eight contemporary Porites colonies collected at nearby reefs. Secondary aragonite overgrowth causes anomalies in skeletal density, Mg/Ca, Sr/Ca, U/Ca, d Dissolution, through incongruent leaching, also causes cool SST artifacts but only for trace element ratios (Mg/Ca-SST À1.2°C; Sr/Ca-SST À1.2°C; U/Ca-SST À2.1°C). The sequence of preference with respect to dissolution of coral skeleton in seawater is Mg > Ca > Sr > U. Rigorous screening of coral material for paleoclimate reconstructions is therefore necessary to detect both dissolution and the presence of secondary minerals. The excellent agreement between apparent SST anomalies generated by different modes of diagenesis means that replication of tracers within a single coral cannot be used to validate climate-proxy interpretations. Poor replication of records between different coral colonies, however, provides a strong indication of nonclimatic artifacts such as dissolution and secondary aragonite.

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Section: Geochemical Impact On Coral Climate Tracersmentioning

confidence: 89%

Section: Geochemical Impact On Coral Climate Tracersmentioning

confidence: 89%

Section: Geochemical Impact On Coral Climate Tracersmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Impact of skeletal dissolution and secondary aragonite on trace element and isotopic climate proxies in Porites corals

et al. 2007

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A comparison of U/Th and rapid‐screen ¹⁴C dates from Line Island fossil corals

Grothe

Cobb

Bush

et al. 2016

Geochem Geophys Geosyst

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Time‐consuming and expensive radiometric dating techniques limit the number of dates available to construct absolute chronologies for high‐resolution paleoclimate reconstructions. A recently developed rapid‐screen 14C dating technique reduces sample preparation time and per sample costs by 90%, but its accuracy has not yet been tested on shallow‐water corals. In this study, we test the rapid‐screen 14C dating technique on shallow‐water corals by comparing 44 rapid‐screen 14C dates to both high‐precision 14C dates and U/Th dates from mid‐ to late‐Holocene fossil corals collected from the central tropical Pacific (2–4°N, 157–160°W). Our results show that 42 rapid‐screen 14C and U/Th dates agree within uncertainties, confirming closed‐system behavior and ensuring chronological accuracy. However, two samples that grew ∼6500 years ago have calibrated 14C ages ∼1000 years younger than the corresponding U/Th ages, consistent with diagenetic alteration as indicated by the presence of 15–23% calcite. Mass balance calculations confirm that the observed dating discrepancies are consistent with 14C addition and U removal, both of which occur during diagenetic calcite recrystallization. Under the assumption that aragonite‐to‐calcite replacement is linear through time, we estimate the samples' true ages using the measured 14C and U/Th dates and percent calcite values. Results illustrate that the rapid‐screen 14C dates of Holocene‐aged fossil corals are accurate for samples with less than 2% calcite. Application of this rapid‐screen 14C method to the fossil coral rubble fields from Kiritimati Island reveal significant chronological clustering of fossil coral across the landscape, with older ages farther from the water's edge.

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Significance of fluid chemistry throughout diagenesis of aragonitic Porites corals – An experimental approach

Pederson

Weiss

Mavromatis

et al. 2019

The Depositional Record

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Marine carbonates are among the most important archives of environmental information in both modern and past environments. Widely used but particularly sensitive archives are the aragonitic skeletons of scleractinian corals. However, due to the metastable nature of aragonite, a multitude of chemical, mineralogical, and (micro)biological processes can lead to diagenetic alteration of these archives and their proxy information can be altered or lost. Here, hydrothermal alteration experiments were performed to create a better understanding of the diagenesis of an often‐utilized genus, Porites. Same‐specimen subsamples were heated in two fluid types and at two temperatures and durations, and their resulting alteration features were assessed to allow insight to the mechanisms and drivers of diagenetic modification. Experiments with fluid temperatures of 130°C induced remobilization and darkening of organic matrices, with no other evidence for alteration observed. In contrast, specimens exposed to a temperature of 160°C underwent significant diagenetic alteration dependent on fluid type. Fluid chemistry, particularly Mg/Ca ratios, was found to regulate the type of alteration (e.g. neomorphism or reprecipitation). Reaction with meteoric water resulted in almost complete neomorphism of the aragonite skeleton to blocky calcite, as well as significant exchange with the experimental fluid. In comparison, samples altered in the experimental burial fluids record no mineralogic or significant isotopic change, but instead, small‐scale dissolution–reprecipitation of the primary skeleton, along with the precipitation of pore‐filling aragonitic needle cements was observed. The δ18Ocarbonate data indicate transformation via dissolution–reprecipitation mechanisms depending on the degree and mechanism of diagenesis, and are strongly dependent on fluid chemistry. The main outcome of this work is that a multi‐proxy approach has the best potential to shed light on the interpretation of processes and pathways of aragonitic coral alteration. This study has implications for early alteration of carbonate archives within varying diagenetic fluids, with results aiding in the identification of past burial conditions.

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Diagenetic effects on the distribution of uranium in live and Holocene corals from the Gulf of Aqaba

Cited by 61 publications

References 34 publications

Impact of skeletal dissolution and secondary aragonite on trace element and isotopic climate proxies in Porites corals

Impact of skeletal dissolution and secondary aragonite on trace element and isotopic climate proxies in Porites corals

A comparison of U/Th and rapid‐screen ¹⁴C dates from Line Island fossil corals

Significance of fluid chemistry throughout diagenesis of aragonitic Porites corals – An experimental approach

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Diagenetic effects on the distribution of uranium in live and Holocene corals from the Gulf of Aqaba

Cited by 61 publications

References 34 publications

Impact of skeletal dissolution and secondary aragonite on trace element and isotopic climate proxies in Porites corals

Impact of skeletal dissolution and secondary aragonite on trace element and isotopic climate proxies in Porites corals

A comparison of U/Th and rapid‐screen 14C dates from Line Island fossil corals

Significance of fluid chemistry throughout diagenesis of aragonitic Porites corals – An experimental approach

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A comparison of U/Th and rapid‐screen ¹⁴C dates from Line Island fossil corals