Diagenetic alteration in low-Mg calcite from macrofossils: a review

Ullmann, Clemens V.; Korte, Christoph

doi:10.7306/gq.1217

Cited by 59 publications

(80 citation statements)

References 104 publications

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“…Samples must therefore be assessed for diagenesis when using geochemistry for palaeoclimatic and/or palaeoecological reconstruction. Qualitative geochemical trends of alteration are well established Veizer, 1980, 1981 Korte, 2015). The elemental and isotopic data of 12 samples from the dorsal side of profile four that exceed this Mn limit were considered in the following discussion because they do not show significant offset from those data derived for the ventral side of this profile where Mn/Ca ratios are consistently lower than 0.05 mmol/mol.…”

Section: Diagenetic Alterationmentioning

confidence: 99%

Chemical and isotopic architecture of the belemnite rostrum

Ullmann

Korte

Hesselbo

2015

Geochimica et Cosmochimica Acta

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Macrofossil calcite is of great importance for quantitative reconstructions of palaeoenvironment and palaeoseasonality. The calcite rostra of belemnites, Jurassic to Cretaceous marine invertebrates, are especially suited for such investigations, because they are comparatively large and are structured by growth bands. Despite their use in chemostratigraphic and palaeoenvironmental studies, much of the internal variability of geochemical signatures in rostra is poorly understood.Here, multiple profiles through a belemnite rostrum of Passaloteuthis bisulcata (~183 Myr old) were analyzed for δ 13 C and δ 18O values as well as Mg/Ca, Sr/Ca and Mn/Ca ratios. Geochemical signatures of the central 1-2 mm of the profiles indicate diagenetic cementation along the apical zone, for which original porosity of up to 40 % can be inferred. The overall δ 13 C and δ18 O values of the other, well preserved parts of the belemnite fluctuate by > 1 per mil, but are nearly uniform within single growth bands. In contrast, Sr/Ca and Mg/Ca in the well-preserved parts show growth-rate and crystal-shape related variability. Close to the central apical zone, strongly bent calcite crystals are enriched in Mg (up to 70 %) and Sr (up to 50 %). Through the remainder of the rostrum, higher calcite precipitation rate can account for Mg depletion of ~15 % and Sr enrichment of ~15 % with respect to co-genetic calcite precipitated at a slower rate. No indication for temperature control on Mg/Ca or Sr/Ca is detected in the investigated specimen. Overall, the new findings indicate that δ 13 C and δ 18O analyses of belemnite rostra produce consistent results regardless of the sampling area within the rostrum, and that growth rate effects on element incorporation are minor with respect to the control exerted by secular changes in seawater composition through time. Additionally, the central part of the rostrum, where strong calcite crystal bending is observed, should be avoided for sampling when studying elemental composition of the calcite for palaeoenvironmental reconstructions.

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Section: Diagenetic Alterationmentioning

confidence: 99%

Chemical and isotopic architecture of the belemnite rostrum

Ullmann

Korte

Hesselbo

2015

Geochimica et Cosmochimica Acta

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“…The Oligocene-Miocene is one of this favourable time intervals during which SIS may achieve resolution in the order of a few 10 5 years. The low-Mg biotic calcite of bivalve shells is one of the most appropriate materials for SIS, because it is resistant to diagenesis and its preservation can be adequately screened by petrographical and geochemical methods (McArthur, 1994;Ullmann & Korte, 2015). Table 3.…”

Section: Sr-isotope Stratigraphymentioning

confidence: 99%

Nummulitids, lepidocyclinids and Sr-isotope data from the Oligocene of Kutch (western India) with chronostratigraphic and paleobiogeographic evaluations

et al. 2018

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“…Despite more than a century of research on carbonate diagenesis, many of the controlling processes are still only understood in a qualitative manner Veizer, 1980, 1981;Swart, 2015). One of the main problems is that diagenetically altered carbonates occur as the product of a complex alteration pathway with an unknown number of intermediate steps and controlling factors (Immenhauser et al, 2015;Swart, 2015;Ullmann and Korte, 2015). Motivated by the lack of quantitative data on rates and products of marine, meteoric, and burial diagenesis, we performed laboratorybased alteration experiments with Arctica islandica shells with the aim to obtain time series data sets.…”

Section: Introductionmentioning

confidence: 99%

Experimental diagenesis: insights into aragonite to calcite transformation of <i>Arctica islandica</i> shells by hydrothermal treatment

Casella¹,

Griesshaber²,

Yin³

et al. 2017

Biogeosciences

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Abstract. Biomineralised hard parts form the most important physical fossil record of past environmental conditions. However, living organisms are not in thermodynamic equilibrium with their environment and create local chemical compartments within their bodies where physiologic processes such as biomineralisation take place. In generating their mineralised hard parts, most marine invertebrates produce metastable aragonite rather than the stable polymorph of CaCO 3 , calcite. After death of the organism the physiological conditions, which were present during biomineralisation, are not sustained any further and the system moves toward inorganic equilibrium with the surrounding inorganic geological system. Thus, during diagenesis the original biogenic structure of aragonitic tissue disappears and is replaced by inorganic structural features.In order to understand the diagenetic replacement of biogenic aragonite to non-biogenic calcite, we subjected Arctica islandica mollusc shells to hydrothermal alteration experiments. Experimental conditions were between 100 and 175 • C, with the main focus on 100 and 175 • C, reaction durations between 1 and 84 days, and alteration fluids simulating meteoric and burial waters, respectively. Detailed microstructural and geochemical data were collected for samples altered at 100 • C (and at 0.1 MPa pressure) for 28 days and for samples altered at 175 • C (and at 0.9 MPa pressure) for 7 and 84 days. During hydrothermal alteration at 100 • C for 28 days most but not the entire biopolymer matrix was destroyed, while shell aragonite and its characteristic microstructure was largely preserved. In all experiments up to 174 • C, there are no signs of a replacement reaction of shell aragonite to calcite in X-ray diffraction bulk analysis. At 175 • C the replacement reaction started after a dormant time of 4 days, and the original shell microstructure was almost completely overprinted by the aragonite to calcite replacement reaction after 10 days. Newly formed calcite nucleated at locations which were in contact with the fluid, at the shell surface, in the open pore system, and along growth lines. In the experiments with fluids simulating meteoric water, calcite crystals reached sizes up to 200 µm, while in the experiments with Mg-containing fluids the calcite crystals reached sizes up to 1 mm after 7 days of alteration. Aragonite is metastable at all applied conditions. Only a small bulk thermodynamicPublished by Copernicus Publications on behalf of the European Geosciences Union. 1462 L. A. Casella et al.: Experimental diagenesis: insights into aragonite to calcite transformation driving force exists for the transition to calcite. We attribute the sluggish replacement reaction to the inhibition of calcite nucleation in the temperature window from ca. 50 to ca. 170 • C or, additionally, to the presence of magnesium. Correspondingly, in Mg 2+ -bearing solutions the newly formed calcite crystals are larger than in Mg 2+ -free solutions. Overall, the aragonite-calcite transition occurs via ...

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Diagenetic alteration in low-Mg calcite from macrofossils: a review

Cited by 59 publications

References 104 publications

Chemical and isotopic architecture of the belemnite rostrum

Chemical and isotopic architecture of the belemnite rostrum

Nummulitids, lepidocyclinids and Sr-isotope data from the Oligocene of Kutch (western India) with chronostratigraphic and paleobiogeographic evaluations

Experimental diagenesis: insights into aragonite to calcite transformation of <i>Arctica islandica</i> shells by hydrothermal treatment

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Diagenetic alteration in low-Mg calcite from macrofossils: a review

Cited by 59 publications

References 104 publications

Chemical and isotopic architecture of the belemnite rostrum

Chemical and isotopic architecture of the belemnite rostrum

Nummulitids, lepidocyclinids and Sr-isotope data from the Oligocene of Kutch (western India) with chronostratigraphic and paleobiogeographic evaluations

Experimental diagenesis: insights into aragonite to calcite transformation of &lt;i&gt;Arctica islandica&lt;/i&gt; shells by hydrothermal treatment

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Experimental diagenesis: insights into aragonite to calcite transformation of <i>Arctica islandica</i> shells by hydrothermal treatment