The extant shore platform stromatolite (SPS) facies association: a glimpse into the Archean?

Smith, Alan; Cooper, Andrew; Misra, Saumitra; Bharuth, Vishal; Guastella, Lisa; Botes, Riaan

doi:https://doi.org/10.5194/bg-15-2189-2018

Articles | Volume 15, issue 7

https://doi.org/10.5194/bg-15-2189-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/bg-15-2189-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 15, issue 7

Research article

|

13 Apr 2018

Research article |

| 13 Apr 2018

The extant shore platform stromatolite (SPS) facies association: a glimpse into the Archean?

Alan Smith, Andrew Cooper, Saumitra Misra, Vishal Bharuth, Lisa Guastella, and Riaan Botes

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Final revised paper (published on 13 Apr 2018)
Preprint (discussion started on 27 Jun 2017)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Interactive comment on "Extant shore-platform stromatolite (SPS) assemble" by Alan Smith et al.', Anonymous Referee #1, 08 Aug 2017
- AC1: 'Reply to referee 1', Alan Smith, 22 Aug 2017
RC2: 'referee comment', Anonymous Referee #2, 19 Aug 2017
- AC2: 'Reply to referee 2', Alan Smith, 09 Oct 2017

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Reconsider after major revisions (21 Oct 2017) by Tina Treude

AR by Alan Smith on behalf of the Authors (30 Nov 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (08 Dec 2017) by Tina Treude

RR by Anonymous Referee #2 (23 Dec 2017)

RR by Anonymous Referee #3 (18 Jan 2018)

Suggestions for revision or reasons for rejection

This report is very interesting and may become important for people interested in stromatolites since it offers new modern analogues which sound closer in terms of textures (although we do not see this at all in the present version of the manuscript) with Archean stromatolites. However, be careful about remaining mistakes in the manuscript. The point about tufas in the Archean seems overstated to me. I do not see why they should exist for sure in the Archean. Just present this as a possibility instead of a certainty. The implications for Mars seem also very speculative and I think you should be clearer about this and better explain the connections between the sites you refer to and the ones you explored on the Earth. I detail my comments thereafter:

- L10 : Metazoan
- « stromatolite-building organisms … thrive in extreme environments… and salt lakes » : This should be toned down regarding the extreme character of the environments. You forget lakes which are not particularly salty/hypersaline or at least that are not called salt lakes and which are not so extreme, i.e. alkaline lakes such as those found in Mexican volcanic craters (e.g., Saghaï et al., 2015 Frontiers in Microbiology)

- L17: Stromatolites are not only formed by the metabolic activity of Cyanobacteria. Anoxygenic phototrophs (Bosak et al., 2007 Geobiology) and in general microorganisms feeding the alkaline engine can play as wall (e.g., Dupraz et al 2009 Earth science review)

- Caption of Table 1: explain the meaning of Min Ptn

- How do you practically affiliate a stromatolite to trapped and bound vs mineral precipitation? Could you mention the criteria?

- P7, L9: replace X by B I guess?

- L11: there is no Fig 3D

- L11: how do you know that runoff is strong there? This is not really obvious from your picture

- P8, L 6: replace ???

- P8 L10: I do not understand this thermocline. Warm water should be lighter and therefore above! I guess this is instead a chemocline here with saltier, hence denser water (and at the same time warmer) beneath.

- P8, L13: where can I see the peat bog?

- Fig 5B: what am I supposed to see except big boulders? Where is tufa? Can you show a close-up

- P12, L11: do not capitalize recent; What is tofu? You mean tufa?

- P13, L1: you refer to Fig 5 for Tinley Manor, Ballito and Cape Morgan but none of tehse sites is shown in Fig 5. Do you mean Fig 6?

- Port Edward: picture of the site? Richards Bay?

- Table 4: explain meaning of abbreviations: SLR, SST

- Discussion: what do you call tripartite stromatolite morphology?

- What do you mean by climax lamination?

- “The presence of tufa within the SPS facies association and its similarity to that of the 3.4 Ga Strelley Pool stromatolites strongly hints that microbial life existed in Archean terrestrial settings”: I do not understand why the presence of tufa within the SPS facies hints that microbial life existed inArchean terrestrial settings. Could you elaborate? Do you mean that anytime we see stromatolites we can infer that there were tufas and hence terrestrial microbial communities? How do we know? What makes the tufas necessary to the formation of stromatolites? Moreover, are not there “abiotic” tufas?

- Could you comment about the size of the extant stromatolites you observe and the size of Archean stromatolites?

- P21; l26: I do not understand at all the connection between phosphorous and the presence of stromatolites on Mars. Could you elaborate? If stromatolites form by the precipitation of CaCO3, you would not expect a higher P concentration to favor CaCO3 precipitation.

- P21-22: I do not understand the connection between the marine SPS described here and possible hydrothermal deposits and/or possible lacustrine deposits. This is a bit of a stretch which is not necessary here.

- Could you show more pictures of handsized samples and document laminations characteristic of stromatolties? I understand that such pictures may be in other papers but it would be good for the reader of the present manuscript to have some idea about how the samples look like

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ED: Publish subject to minor revisions (review by editor) (31 Jan 2018) by Tina Treude

AR by Alan Smith on behalf of the Authors (12 Feb 2018) Author's response Manuscript

ED: Publish as is (23 Feb 2018) by Tina Treude

AR by Alan Smith on behalf of the Authors (02 Mar 2018) Manuscript

Short summary

Growing shore-platform stromatolites are increasingly found on modern rocky coasts. Stromatolites are very similar to Archean and Proterozoic stromatolites. A study of modern stromatolites may shed light on the conditions that existed on the early Earth and other planets and possibly provide information on how life began.