Identification and composition of secondary meniscus calcite in fossil coral and the effect on predicted sea surface temperature

Dalbeck, Paul; Cusack, Maggie; Dobson, Phillip S.; Allison, Nicola; Fallick, Anthony E.; Tudhope, Alexander W.

doi:10.1016/j.chemgeo.2010.11.018

Cited by 22 publications

(22 citation statements)

References 65 publications

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“…Most available data concern calcite cements (in skeleton pores) that display very low Sr/Ca values, leadingto an average SST bias of 1 to 1.7°C per calcite-% (e.g., Allison et al, 2007;Griffiths et al, 2013 and Table 1 for other related studies). For a mix of cement and intra-skeletal calcite, McGregor and Gagan (2003) calculated an impact of ~1.15°C per calcite-% and, for calcite meniscus mimicking dissepiments, Dalbeck et al (2011) calculated a value of +1.2°C per calcite-%.In our case, the calculated SST using seasonal Sr/Ca ratios was, on average, 3.4°C higher than the gridded-SST for a mean of 24% of intra-skeletal calcite. This would correspond to a +0.14 ± 0.03°C per calcite-% that is confirmed at the yearly timescale with a value of +0.08 ± 0.06°C per calcite-%.…”

Section: 2intra-skeletal Calcite and Its Impact On Reconstructed Sstmentioning

confidence: 53%

“…In addition, the calcite crystals are massive with a flat and homogeneous surface. In other coral diagenesis studies (Frankowiak et al, 2013;McGregor and Gagan, 2003), these characteristics correspond to calcite crystals called calcite spar, most probably of non-biogenic origin (Dalbeck et al, 2011). Moreover, using the relationship between the Sr/Ca signature and the calcite-%,we calculated a 100% calcite Sr/Ca ratio end-member of ~7.96 ± 0.31 mmol/mol.…”

Section: Origin Of the Intra-skeletal Calcite: Biogenic Vs Early Diamentioning

confidence: 74%

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Intra-skeletal calcite in a live-collected Porites sp.: Impact on environmental proxies and potential formation process

Lazareth

Soares-Pereira

Douville

et al. 2016

Geochimica et Cosmochimica Acta

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Geochemical proxies measured in the carbonate skeleton of tropical coral Porites sp. have commonly been used to reconstruct sea surface temperature (SST) and more recently seawater pH. Nevertheless, both reconstructed SST and pH depend on the preservation state of the skeleton, here made of aragonite; i.e., diagenetic processes and its related effects should be limited. In this study, we report on the impact of the presence of intra-skeletal calcite on the skeleton geochemistry of a live-collected Porites sp..The Porites skeleton preservation state was analyzed using X-ray diffraction and scanning electron microscopy. Sr/Ca, Mg/Ca, U/Ca, Ba/Ca, Li/Mg, and B/Ca ratios were measured at a monthly and yearly resolution using solution ICP-MS and multi-collector ICP-MS. Theδ 11 B signatures and the calcite percentages were acquired at a yearly timescale. The coral colony presents two parts, one with less than 3% calcite (referred to as "no-calcite" skeleton), the other one, corresponding to the skeleton formed during the last 4 yrs. of growth,with calcite percentages varying from 13 to 32% (referred to as "with calcite" skeleton). This intra-skeletal calcite replaces partly or completely numerouscenter of calcification (COCs). All geochemical tracers investigated are significantlyimpacted by the presence of calcite. Thereconstructed SSTdecreasesby about0.1°C per calcite-percent as inferred fromthe Sr/Ca ratio. Such impact reaches up to 0.26°C per calcite-percent for temperature deduced from the Li/Mg ratio. So, less than 5% of such intra-skeletal calcite does not prevent SST reconstructions using Sr/Ca ratio, but the percentage and type of calcite have to be determined before fine SST interpretation. Seawater pH reconstruction inferredfrom boron isotopes drop by about -0.011 pH-unit per calcitepercent. Such sensitivity to calcite presence is particularly dramatic for fine paleo-pH reconstructions. Here we suggest that after being brought to shallow waters following a cyclone, the studied coral was seasonally subjected to rainfall-related water freshening that could have mimicked a vadose environment like can be encountered on raised fossil coral reefs. Nevertheless, the process of calcite precipitation remains to be determined.

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Section: 2intra-skeletal Calcite and Its Impact On Reconstructed Sstmentioning

confidence: 53%

Section: Origin Of the Intra-skeletal Calcite: Biogenic Vs Early Diamentioning

confidence: 74%

Intra-skeletal calcite in a live-collected Porites sp.: Impact on environmental proxies and potential formation process

Lazareth

Soares-Pereira

Douville

et al. 2016

Geochimica et Cosmochimica Acta

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“…A significant number of previous studies have failed to consider the effects of early marine diagenesis, which can influence the geochemistry even in live collected coral material (Ribaud-Laurenti et al, 2001;Allison et al, 2005;Hendy et al, 2007;Nothdurft and Webb, 2009;DeLong et al, 2010;Dalbeck et al, 2011). Geochemical variability associated with coral skeleton ultrastructure should also be considered when assessing the potential for new coral based palaeothermometers (e.g., Bagnato et al, 2004;Damassa et al, 2006;Giry et al, 2010).…”

Section: Discussionmentioning

confidence: 99%

“…Although some syntaxial cement becomes coarser than original coral aragonite biocrystals, and is thus identifiable based on texture, cements may mimic the original morphologies of the skeletal ultrastructure (Ribaud-Laurenti et al, 2001;Dalbeck et al, 2011) making it difficult to identify petrographically. Secondary, inorganic aragonite has an increased resistance to early diagenesis , potentially owing to its lack of associated organic matrix, and a reduced Mg/Ca ratio (Enmar et al, 2000;Sayani et al, 2011) compared to primary coral aragonite.…”

Section: Screening For Diagenesismentioning

confidence: 99%

Geochemistry-based coral palaeoclimate studies and the potential of ‘non-traditional’ (non-massive Porites) corals: Recent developments and future progression

Sadler

Webb

Nothdurft

et al. 2014

Earth-Science Reviews

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“…Dissolution is a diagenetic texture that can cause cool SST artifacts [14,16]. One percent secondary calcite is enough to cause 1°C warming artifacts in absolute Sr/Ca SST reconstruction, although seasonal variability in Sr/Ca SST may still be preserved [7,8,10,16,28,29]. For this reason, in geochemical studies it is highly recommended to scan for aragonite, calcite cement, and dissolution with petrographic and SEM analysis in any areas that are suspected to have diagenetic textures and to use only corals confirmed to be pristine.…”

Section: Petrography Analysismentioning

confidence: 99%

Diagenetic Screening in Porites Fossil Corals from South Pagai, Kendari, and Banten Bay, Indonesia

Utami

Cahyarini

2017

J. Eng. Technol. Sci.

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Abstract. Fossil corals are commonly used in paleoclimate studies to get records of climate parameters throughout the Holocene and beyond. Diagenesis is known as an important error source in paleoclimate reconstruction. The aim of this research was to provide a comprehensive diagenetic investigation involving 2D-XRD, petrographic analysis, and scanning electron microscopy (SEM) of Porites spp fossil samples from South Pagai, Kendari and Banten Bay, Indonesia as a starting point for further climate studies using coral proxies. This research focused on samples with around 1% calcite content, a level that can create misinterpretation of geochemical proxies. The results indicate that the samples from Banten Bay and South Pagai are well preserved and reliable for paleoclimate study. Only Sample BG1 is not recommended for further use in geochemical proxy analysis due to intensive diagenesis. 2D-XRD allows calcite screening without destroying the coral sample and assists in defining alternative sampling transects. Secondary aragonite and dissolution cannot be identified with 2D-XRD, therefore diagenetic screening should be combined with petrographic and SEM analysis in any areas presumed to have diagenetic textures.

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Identification and composition of secondary meniscus calcite in fossil coral and the effect on predicted sea surface temperature

Cited by 22 publications

References 65 publications

Intra-skeletal calcite in a live-collected Porites sp.: Impact on environmental proxies and potential formation process

Intra-skeletal calcite in a live-collected Porites sp.: Impact on environmental proxies and potential formation process

Geochemistry-based coral palaeoclimate studies and the potential of ‘non-traditional’ (non-massive Porites) corals: Recent developments and future progression

Diagenetic Screening in Porites Fossil Corals from South Pagai, Kendari, and Banten Bay, Indonesia

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