Electron backscatter diffraction analysis unveils foraminiferal calcite microstructure and processes of diagenetic alteration

Procter, Frances Alice; Piazolo, Sandra; John, Eleanor Heulwen; Walshaw, Richard; Pearson, Paul Nicholas; Lear, Caroline Helen; Aze, Tracy

doi:https://doi.org/10.5194/egusphere-2023-2213

Preprints

https://doi.org/10.5194/egusphere-2023-2213

Preprints

05 Oct 2023

| 05 Oct 2023

Electron backscatter diffraction analysis unveils foraminiferal calcite microstructure and processes of diagenetic alteration

Frances Alice Procter, Sandra Piazolo, Eleanor Heulwen John, Richard Walshaw, Paul Nicholas Pearson, Caroline Helen Lear, and Tracy Aze

Abstract. Electron backscatter diffraction (EBSD) analysis enables a unique perspective of the internal microstructure of foraminiferal calcite. Specifically, EBSD provides crystallographic data from within the test, highlighting the highly organised “mesocrystal” structure of crystallographically aligned domains throughout the test, formed by sequential deposits of microgranular calcite. We compared EBSD maps across the test walls of both poorly- and well-preserved specimens of the planktonic foraminifera species Globigerinoides ruber and Morozovella crater. The EBSD maps, paired with information about intra-test distributions of Mg/Ca ratios, allowed us to examine the effects of different diagenetic processes on the foraminifera test. In poorly-preserved specimens EBSD data shows extensive reorganisation of the biogenic crystal microstructure, indicating differing phases of dissolution, re-precipitation and overgrowth. The specimens with the greatest degree of microstructural reorganisation also show an absence of higher concentration magnesium bands, which are typical features of well-preserved specimens. These findings provide important insights into the extent of post-depositional changes both in microstructure and geochemical signals that must be considered when utilising foraminifera to generate proxy archive data.

Received: 27 Sep 2023 – Discussion started: 05 Oct 2023

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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

Journal article(s) based on this preprint

13 Mar 2024

Electron backscatter diffraction analysis unveils foraminiferal calcite microstructure and processes of diagenetic alteration

Frances A. Procter, Sandra Piazolo, Eleanor H. John, Richard Walshaw, Paul N. Pearson, Caroline H. Lear, and Tracy Aze

Biogeosciences, 21, 1213–1233, https://doi.org/10.5194/bg-21-1213-2024,https://doi.org/10.5194/bg-21-1213-2024, 2024

Short summary

Frances Alice Procter, Sandra Piazolo, Eleanor Heulwen John, Richard Walshaw, Paul Nicholas Pearson, Caroline Helen Lear, and Tracy Aze

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2023-2213', Chiara Consolaro, 15 Nov 2023

I reviewed the paper Egusphere-2023-2213: Electron backscatter diffraction analysis unveils foraminiferal calcite microstructure and processes of diagenetic alteration by A. Procter et al., and I think that it is a very interesting and important topic, very well presented and well written.
I have only some minor comments to the manuscript before it can be accepted.
Line 15: "data shows" it is correct but maybe it would be preferable to use it in its plural form, so data show.
Line 29: instead of "planktic" foraminifera is better to use planktonic like it has been done in the rest of the paper.
Line 63: maybe substitute ";" with ", "after the quotes in brackets.
Lines 205-206: is there a reason why 'fanning' grains are associated with a lack of porosity or is it just an observation? Maybe elaborate further?
Lines 215-216: rewrite or clarify the sentence "with greater spread in the points for the latter".
Line 217: state what does the abbreviation IPF-Y stands for when you mention it for the first time.
Figure 3 and 4: (g, h) the axes and the letters in the 3D diagram unit cells are not well visible, please make them more visible. (i,j) The plots of the selected grains on the pole plots represented in orange and yellow are difficult to see, maybe change color or make the symbols bigger?
Line 359: please explain better what do you mean with "further along this proposed diagenetic pathway".
362: maybe substitute ";" with ":" after process, or reformulate the last part of the sentence.
Lines 409-414: maybe make a reference and clear connection with the last part of Fig. 5 (d and e)?
Appendix A- Frequency of twin boundaries: it is not possible to read the text on the graphs, maybe increase the quality of the figure?
Line 698: add a space after the reference of Putnis A., 2009

Citation: https://doi.org/10.5194/egusphere-2023-2213-RC1
- AC1: 'Reply on RC1', Frances A. Procter, 19 Dec 2023
  
  I reviewed the paper Egusphere-2023-2213: Electron backscatter diffraction analysis unveils foraminiferal calcite microstructure and processes of diagenetic alteration by A. Procter et al., and I think that it is a very interesting and important topic, very well presented and well written.
  I have only some minor comments to the manuscript before it can be accepted.
  We thank the reviewer for their kind words and positive feedback on our manuscript.
  Line 15: "data shows" it is correct but maybe it would be preferable to use it in its plural form, so data show.
  This has now been changed to ‘data show’.
  Line 29: instead of "planktic" foraminifera is better to use planktonic like it has been done in the rest of the paper.
  We have replaced ‘planktic’ with ‘planktonic’.
  Line 63: maybe substitute ";" with ", "after the quotes in brackets.
  We have substituted the semi-colon for a comma here.
  Lines 205-206: is there a reason why 'fanning' grains are associated with a lack of porosity or is it just an observation? Maybe elaborate further?
  We have clarified that: “These fanning grains are observed here to be associated with a lack of porosity, growing into available space.”
  Lines 215-216: rewrite or clarify the sentence "with greater spread in the points for the latter".
  We have re-written this sentence to read: “The c-axis of crystals are most strongly clustered on the pole figures of glassy G. ruber, with strong alignment also present in frosty G. ruber, despite a greater spread in the orientation data of frosty G. ruber (Fig. 3i,j).”
  Line 217: state what does the abbreviation IPF-Y stands for when you mention it for the first time.
  We have added the explanation of the IPF-Y abbreviation into the methods section 2.4, where we describe these IPF-Y orientation maps. Lines 145-147 now read:
  "IPF-Y maps (inverse pole figure colour maps showing crystallographic orientation in the Y direction) show the crystal orientation at each analysis spot, colour coded according to the relative orientation of the crystallographic axes in relation to the sample y-direction (see colour key in Figs. 3h, 4h)."
  Figure 3 and 4: (g, h) the axes and the letters in the 3D diagram unit cells are not well visible, please make them more visible. (i,j) The plots of the selected grains on the pole plots represented in orange and yellow are difficult to see, maybe change color or make the symbols bigger?
  We have edited the 3D diagrams to make the labels clearer. We have also increased the size of the selected grains on the pole plots and changed the colour.
  Line 359: please explain better what do you mean with "further along this proposed diagenetic pathway".
  We have changed this sentence to read: “The lack of magnesium banding and generally low Mg/Ca of the frosty M. crater specimen indicates that it has experienced a greater degree of diagenetic alteration.”
  362: maybe substitute ";" with ":" after process, or reformulate the last part of the sentence.
  The semi colon has been replaced with a colon.
  Lines 409-414: maybe make a reference and clear connection with the last part of Fig. 5 (d and e)?
  We have added in references to Figs. 5d and 5e within the text lines 409-414, and also referenced earlier figures (Figs 3e,g, and 4f,h,) which highlight this point well.
  Appendix A- Frequency of twin boundaries: it is not possible to read the text on the graphs, maybe increase the quality of the figure?
  The size and quality of the figure has been increased to make sure the text on the figures is readable.
  Line 698: add a space after the reference of Putnis A., 2009
  We have added a space after this reference.
  
  Citation: https://doi.org/10.5194/egusphere-2023-2213-AC1
RC2:
'Comment on egusphere-2023-2213', Adriane Lam, 12 Dec 2023

The manuscript by Proctor et al. uses electron backscatter diffraction to investigate post-depositional processes that affect foraminiferal tests. This manuscript is extremely well-organized, well-structured, and scientifically important to everyone who use foraminiferal calcite in geochemical analyses. Below are a few comments:
Throughout, either be consistent with use of ‘planktic’ or ‘planktonic’
Line 92: Spell out ‘Globigerinoides’ at the beginning of the sentence
Line 92-93: the pforams@mikrotax site lists ruber as evolving within 10.46-11.63 Ma (Chaisson and Pearson, 1997)
In the Methods section, it would be helpful to have a short paragraph about the lithology at each site, specifically within the interval from which specimens were taken for analyses.
Table 1: Would be helpful to also include a column with the water depth
Figures 5 and 6 are awesome!

Citation: https://doi.org/10.5194/egusphere-2023-2213-RC2
- AC2: 'Reply on RC2', Frances A. Procter, 19 Dec 2023
  
  The manuscript by Proctor et al. uses electron backscatter diffraction to investigate post-depositional processes that affect foraminiferal tests. This manuscript is extremely well-organized, well-structured, and scientifically important to everyone who use foraminiferal calcite in geochemical analyses. Below are a few comments:
  We thank the reviewer for their kind words and enthusiasm for the work we have presented.
  Throughout, either be consistent with use of ‘planktic’ or ‘planktonic’
  Planktonic is now used exclusively throughout the manuscript.
  Line 92: Spell out ‘Globigerinoides’ at the beginning of the sentence
  This sentence now opens "Globigerinoides ruber".
  Line 92-93: the pforams@mikrotax site lists ruber as evolving within 10.46-11.63 Ma (Chaisson and Pearson, 1997)
  We have revised the date to 15.12 Ma to be consistent with Lamyman et al. (in prep), Phylogeny of Planktonic Foraminifera; however we note that the origin of G. ruber will be subject to revision as part of the Neogene and Quaternary planktonic foraminifera working group (https://www.mikrotax.org/pforams/pf-pages/NeogeneWorkingGroup.php)
  Lamyman et al. use Stanley, Wetmore and Kennett (1988) for the dates for G. ruber.
  Stanley, K. Wetmore, L. and Kennett, J. P., 1988. Macroevolutionary differences between two major clades of Neogene planktonic foraminifera. Paleobiology,14, 235-249.
  In the Methods section, it would be helpful to have a short paragraph about the lithology at each site, specifically within the interval from which specimens were taken for analyses.
  The lithology of core material from each site has been added to Section 2.1 Sample material and preparation.
  After the line: “Foraminifera were recovered from core material known to contain foraminifera specimens with differing degrees of preservation (Fig. 1; Table 1).” On line 95, we have added in the following:
  The sediments from both Tanzanian cores, TDP 20, and GLOW 22 are rich in clay (Kroon et al., 2009), with the principle lithology of our section from TDP 20 being soft light olive grey clays with mottled yellowish orange sandy clay (Nicholas et al., 2006). Our core samples from sites U1335A and DSDP 527 are contrarily characterised by nanofossil ooze, with ~ 60% CaCO₃wt% in our section from U1335A (Pälike et al., 2010) and our DSDP section characterised by nanofossil ooze and nanofossil chalk has a calcium carbonate content fluctuating around 90% (Moore et al., 1984).
  Table 1: Would be helpful to also include a column with the water depth
  Water depths have been added to Table 1.
  Figures 5 and 6 are awesome!
  We thank the reviewer for their very kind praise of Figures 5 and 6.
  
  Citation: https://doi.org/10.5194/egusphere-2023-2213-AC2

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2023-2213', Chiara Consolaro, 15 Nov 2023

I reviewed the paper Egusphere-2023-2213: Electron backscatter diffraction analysis unveils foraminiferal calcite microstructure and processes of diagenetic alteration by A. Procter et al., and I think that it is a very interesting and important topic, very well presented and well written.
I have only some minor comments to the manuscript before it can be accepted.
Line 15: "data shows" it is correct but maybe it would be preferable to use it in its plural form, so data show.
Line 29: instead of "planktic" foraminifera is better to use planktonic like it has been done in the rest of the paper.
Line 63: maybe substitute ";" with ", "after the quotes in brackets.
Lines 205-206: is there a reason why 'fanning' grains are associated with a lack of porosity or is it just an observation? Maybe elaborate further?
Lines 215-216: rewrite or clarify the sentence "with greater spread in the points for the latter".
Line 217: state what does the abbreviation IPF-Y stands for when you mention it for the first time.
Figure 3 and 4: (g, h) the axes and the letters in the 3D diagram unit cells are not well visible, please make them more visible. (i,j) The plots of the selected grains on the pole plots represented in orange and yellow are difficult to see, maybe change color or make the symbols bigger?
Line 359: please explain better what do you mean with "further along this proposed diagenetic pathway".
362: maybe substitute ";" with ":" after process, or reformulate the last part of the sentence.
Lines 409-414: maybe make a reference and clear connection with the last part of Fig. 5 (d and e)?
Appendix A- Frequency of twin boundaries: it is not possible to read the text on the graphs, maybe increase the quality of the figure?
Line 698: add a space after the reference of Putnis A., 2009

Citation: https://doi.org/10.5194/egusphere-2023-2213-RC1
- AC1: 'Reply on RC1', Frances A. Procter, 19 Dec 2023
  
  I reviewed the paper Egusphere-2023-2213: Electron backscatter diffraction analysis unveils foraminiferal calcite microstructure and processes of diagenetic alteration by A. Procter et al., and I think that it is a very interesting and important topic, very well presented and well written.
  I have only some minor comments to the manuscript before it can be accepted.
  We thank the reviewer for their kind words and positive feedback on our manuscript.
  Line 15: "data shows" it is correct but maybe it would be preferable to use it in its plural form, so data show.
  This has now been changed to ‘data show’.
  Line 29: instead of "planktic" foraminifera is better to use planktonic like it has been done in the rest of the paper.
  We have replaced ‘planktic’ with ‘planktonic’.
  Line 63: maybe substitute ";" with ", "after the quotes in brackets.
  We have substituted the semi-colon for a comma here.
  Lines 205-206: is there a reason why 'fanning' grains are associated with a lack of porosity or is it just an observation? Maybe elaborate further?
  We have clarified that: “These fanning grains are observed here to be associated with a lack of porosity, growing into available space.”
  Lines 215-216: rewrite or clarify the sentence "with greater spread in the points for the latter".
  We have re-written this sentence to read: “The c-axis of crystals are most strongly clustered on the pole figures of glassy G. ruber, with strong alignment also present in frosty G. ruber, despite a greater spread in the orientation data of frosty G. ruber (Fig. 3i,j).”
  Line 217: state what does the abbreviation IPF-Y stands for when you mention it for the first time.
  We have added the explanation of the IPF-Y abbreviation into the methods section 2.4, where we describe these IPF-Y orientation maps. Lines 145-147 now read:
  "IPF-Y maps (inverse pole figure colour maps showing crystallographic orientation in the Y direction) show the crystal orientation at each analysis spot, colour coded according to the relative orientation of the crystallographic axes in relation to the sample y-direction (see colour key in Figs. 3h, 4h)."
  Figure 3 and 4: (g, h) the axes and the letters in the 3D diagram unit cells are not well visible, please make them more visible. (i,j) The plots of the selected grains on the pole plots represented in orange and yellow are difficult to see, maybe change color or make the symbols bigger?
  We have edited the 3D diagrams to make the labels clearer. We have also increased the size of the selected grains on the pole plots and changed the colour.
  Line 359: please explain better what do you mean with "further along this proposed diagenetic pathway".
  We have changed this sentence to read: “The lack of magnesium banding and generally low Mg/Ca of the frosty M. crater specimen indicates that it has experienced a greater degree of diagenetic alteration.”
  362: maybe substitute ";" with ":" after process, or reformulate the last part of the sentence.
  The semi colon has been replaced with a colon.
  Lines 409-414: maybe make a reference and clear connection with the last part of Fig. 5 (d and e)?
  We have added in references to Figs. 5d and 5e within the text lines 409-414, and also referenced earlier figures (Figs 3e,g, and 4f,h,) which highlight this point well.
  Appendix A- Frequency of twin boundaries: it is not possible to read the text on the graphs, maybe increase the quality of the figure?
  The size and quality of the figure has been increased to make sure the text on the figures is readable.
  Line 698: add a space after the reference of Putnis A., 2009
  We have added a space after this reference.
  
  Citation: https://doi.org/10.5194/egusphere-2023-2213-AC1
RC2:
'Comment on egusphere-2023-2213', Adriane Lam, 12 Dec 2023

The manuscript by Proctor et al. uses electron backscatter diffraction to investigate post-depositional processes that affect foraminiferal tests. This manuscript is extremely well-organized, well-structured, and scientifically important to everyone who use foraminiferal calcite in geochemical analyses. Below are a few comments:
Throughout, either be consistent with use of ‘planktic’ or ‘planktonic’
Line 92: Spell out ‘Globigerinoides’ at the beginning of the sentence
Line 92-93: the pforams@mikrotax site lists ruber as evolving within 10.46-11.63 Ma (Chaisson and Pearson, 1997)
In the Methods section, it would be helpful to have a short paragraph about the lithology at each site, specifically within the interval from which specimens were taken for analyses.
Table 1: Would be helpful to also include a column with the water depth
Figures 5 and 6 are awesome!

Citation: https://doi.org/10.5194/egusphere-2023-2213-RC2
- AC2: 'Reply on RC2', Frances A. Procter, 19 Dec 2023
  
  The manuscript by Proctor et al. uses electron backscatter diffraction to investigate post-depositional processes that affect foraminiferal tests. This manuscript is extremely well-organized, well-structured, and scientifically important to everyone who use foraminiferal calcite in geochemical analyses. Below are a few comments:
  We thank the reviewer for their kind words and enthusiasm for the work we have presented.
  Throughout, either be consistent with use of ‘planktic’ or ‘planktonic’
  Planktonic is now used exclusively throughout the manuscript.
  Line 92: Spell out ‘Globigerinoides’ at the beginning of the sentence
  This sentence now opens "Globigerinoides ruber".
  Line 92-93: the pforams@mikrotax site lists ruber as evolving within 10.46-11.63 Ma (Chaisson and Pearson, 1997)
  We have revised the date to 15.12 Ma to be consistent with Lamyman et al. (in prep), Phylogeny of Planktonic Foraminifera; however we note that the origin of G. ruber will be subject to revision as part of the Neogene and Quaternary planktonic foraminifera working group (https://www.mikrotax.org/pforams/pf-pages/NeogeneWorkingGroup.php)
  Lamyman et al. use Stanley, Wetmore and Kennett (1988) for the dates for G. ruber.
  Stanley, K. Wetmore, L. and Kennett, J. P., 1988. Macroevolutionary differences between two major clades of Neogene planktonic foraminifera. Paleobiology,14, 235-249.
  In the Methods section, it would be helpful to have a short paragraph about the lithology at each site, specifically within the interval from which specimens were taken for analyses.
  The lithology of core material from each site has been added to Section 2.1 Sample material and preparation.
  After the line: “Foraminifera were recovered from core material known to contain foraminifera specimens with differing degrees of preservation (Fig. 1; Table 1).” On line 95, we have added in the following:
  The sediments from both Tanzanian cores, TDP 20, and GLOW 22 are rich in clay (Kroon et al., 2009), with the principle lithology of our section from TDP 20 being soft light olive grey clays with mottled yellowish orange sandy clay (Nicholas et al., 2006). Our core samples from sites U1335A and DSDP 527 are contrarily characterised by nanofossil ooze, with ~ 60% CaCO₃wt% in our section from U1335A (Pälike et al., 2010) and our DSDP section characterised by nanofossil ooze and nanofossil chalk has a calcium carbonate content fluctuating around 90% (Moore et al., 1984).
  Table 1: Would be helpful to also include a column with the water depth
  Water depths have been added to Table 1.
  Figures 5 and 6 are awesome!
  We thank the reviewer for their very kind praise of Figures 5 and 6.
  
  Citation: https://doi.org/10.5194/egusphere-2023-2213-AC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

ED: Publish subject to minor revisions (review by editor) (31 Dec 2023) by Chiara Borrelli

This manuscript presents some very interesting data regarding the diagenetic alteration of two different species of planktonic foraminifera, Globigerinoides ruber and Morozovella crater. These species are representative of different geological ages, as well as shell (test) wall type. The work has been reviewed by two experts. They both agreed that the manuscript is well-written, the results are interesting, and the manuscript deserves to be published in BG after minor revisions. I concur with the reviewers’ assessment. The manuscript is definitely well-written and easy to follow. The results are interesting and appropriate for publication in BG. However, I do have some concerns regarding the rather limited number of samples analyzed (two specimens/species; one glassy, one frosty). I appreciate that the analyses performed are quite detailed and time-consuming (although the EMPA Mg/Ca maps for M. crater come from a different study) and that it might not be feasible to analyze more specimens. However, I would like to see some additional discussion about how representative the dataset presented is in the context of the species analyzed and how applicable the findings are to other planktonic foraminiferal species. In addition, I have some minor comments as detailed below. I invite the authors to consider all the feedbacks received, to improve the discussion of the representativeness of their results, and to resubmit a revised version of their work after what I believe to be minor to moderate revisions.

Minor comments:

Line 80: SEM should be spelled at line 80 (first time the acronym is used) rather than at line 99.

Line 98: please, provide a brief explanation of why methanol was used to clean M. crater specimens.

Line 101: ‘foraminifera specimens’ should be ‘foraminiferal specimens’. This comment applies to the entire manuscript.

Lines 103-106: for the silicon carbide disks, diamond paste, and colloidal silica, please provide the name of the manufacturers.

Section 2.3 – quantitative Mg and Ca maps were done by EMPA. Did you calibrate the instrument using a standard? If you did, please specify which one. If you did not, please provide some additional details about how quantitative maps were generated.

Line 144: is ‘quantitative EBSD data’ the best way to describe these data?

Line 186: Because it is the beginning of the sentence, please spell out EBSD.

Table 2 is missing.

Hide

AR by Frances A. Procter on behalf of the Authors (11 Jan 2024) Author's response Author's tracked changes Manuscript

ED: Publish subject to technical corrections (13 Jan 2024) by Chiara Borrelli

AR by Frances A. Procter on behalf of the Authors (17 Jan 2024) Author's response Manuscript

Journal article(s) based on this preprint

13 Mar 2024

Electron backscatter diffraction analysis unveils foraminiferal calcite microstructure and processes of diagenetic alteration

Frances A. Procter, Sandra Piazolo, Eleanor H. John, Richard Walshaw, Paul N. Pearson, Caroline H. Lear, and Tracy Aze

Biogeosciences, 21, 1213–1233, https://doi.org/10.5194/bg-21-1213-2024,https://doi.org/10.5194/bg-21-1213-2024, 2024

Short summary

Frances Alice Procter, Sandra Piazolo, Eleanor Heulwen John, Richard Walshaw, Paul Nicholas Pearson, Caroline Helen Lear, and Tracy Aze

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This study looked at the microstructure of planktonic foraminifera (single celled marine organisms) fossils, to further our understanding of how they form their hard exterior shells, and how the microstructure and chemistry of the shells can change as a result of processes which occur to them after deposition on the seafloor. Understanding these processes is of critical importance for using planktonic foraminifera for robust climate and environmental reconstructions of the past.


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