The Paleocene–Eocene Thermal Maximum at DSDP Site 277, Campbell Plateau, southern Pacific Ocean

Hollis, C. J.; Hines, B. R.; Littler, K.; Villasante-Marcos, V.; Kulhanek, D. K.; Strong, C. P.; Zachos, J. C.; Eggins, S. M.; Northcote, L.; Phillips, A.

doi:https://doi.org/10.5194/cp-11-1009-2015

Articles | Volume 11, issue 7

https://doi.org/10.5194/cp-11-1009-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/cp-11-1009-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 11, issue 7

Research article

|

31 Jul 2015

Research article |

| 31 Jul 2015

The Paleocene–Eocene Thermal Maximum at DSDP Site 277, Campbell Plateau, southern Pacific Ocean

C. J. Hollis, B. R. Hines, K. Littler, V. Villasante-Marcos, D. K. Kulhanek, C. P. Strong, J. C. Zachos, S. M. Eggins, L. Northcote, and A. Phillips

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Final revised paper (published on 31 Jul 2015)
Supplement to the final revised paper
Preprint (discussion started on 12 Feb 2015)
Supplement to the preprint

Interactive discussion

Status: closed

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

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- Supplement

RC C21: 'Review: Hollis et al., PETM at DSDP 277', Paul Pearson, 16 Feb 2015
RC C230: 'Review Hollis et al. 2015', Reinhard Kozdon, 14 Apr 2015
EC C296: 'reply to comments', Appy Sluijs, 30 Apr 2015
AC C323: 'Response to Referees: “Onset of the Paleocene-Eocene Thermal Maximum in the southern Pacific Ocean”', Chris Hollis, 07 May 2015
EC C499: 'invitation revised manuscript', Appy Sluijs, 02 Jun 2015

Peer-review completion

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

AR by Chris Hollis on behalf of the Authors (05 Jun 2015) Author's response Manuscript

ED: Referee Nomination & Report Request started (05 Jun 2015) by Appy Sluijs

RR by Paul Pearson (08 Jun 2015)

RR by Reinhard Kozdon (04 Jul 2015)

Suggestions for revision or reasons for rejection

This is my second review of the manuscript “The Paleocene-Eocene Thermal Maximum at DSDP Site 277, Campbell Plateau, southern Pacific Ocean” submitted by Hollis et al. In summary, I think that the authors addressed most of my concerns and comments, and I see no major “show-stopper” in publishing the current version.

However, the largely uncoupled d18O and d13C records presented in this study are complex and difficult to interpret, and, as I mentioned in my first revision, I wish the authors would have taken more care in assessing the different stages of foraminiferal diagenesis within this core. The authors argue that foraminiferal shells from the PETM appear to be better preserved than samples from the latest Paleocene, presumably due to the higher clay content reported by the authors. The screening of laser ablation profiles for high Al/Ca ratios as well as high and low Sr/Ca ratios to assess silicate contamination and diagenesis, respectively, is a suitable approach to estimate foraminiferal preservation. However, the mechanisms of foraminiferal diagenesis are very complex, and the degree and type of diagenesis may change on cm-scales within the sediment core. Furthermore, the PETM was characterized by ocean acidification, causing potentially alternating events of partial dissolution (‘burn-down”) and reprecipitation. Detailed visual investigation by SEM, in concert with the geochemical data, could have provided a better understanding of the largely uncoupled d18O and d13C records, in particular the massive decrease in d18O after the PETM onset that cannot be solely explained by a temperature increase.

Therefore, I am still surprised that the authors did not acquire high-mag SEM images of the chamber walls and shell textures (e.g. similar to those shown in various studies by Pearson et al. or Sexton et al.) especially as the Paleocene-Eocene Section of DSDP Site 277 was already known to be significantly affected by diagenesis.

However, some of these concerns are now addressed by new figures and images in the supplementary material, showing at least some (low-mag) SEM images of whole-shells in various states of preservation as well as the corresponding laser ablation profiles (supplementary file, Fig. S1), and I fully understand that a more thorough investigation is beyond the scope of this study.

Some minor comments:

Line 159: It is very challenging to find information about the foraminiferal species “S. roesnasensis”. Therefore, the authors may consider to include a reference describing/characterizing this foraminiferal species.
line 152: it shall read praemundulus.
line 186 ArF laser
line 199-203: the two sentences are almost identical in their content. The authors may consider to merge them into a single sentence
line 352: if this is a primary feature
line 415: I think it shall read ‘whole-shell’, not wholesale
line 421: it think it shall read ‘studied’, not ‘studies’. The whole sentence is somehow redundant (diagenetic impact was already mentioned in the previous paragraph).
line 479: here; P/E boundary, P-E boundary at other locations within the text
line 496: I am not sure if a manuscript ‘under revision’ is a suitable reference. ‘under revision’ does not guarantee that the manuscript will be published.
spelling: be consistent in capitalization (Paleocene-Eocene thermal maximum or Paleocene-Eocene Thermal Maximum).

Supplementary Material:

Figure S1: Please mention the core depths were the samples showing different degrees of diagenesis were taken.
File “Hollis&_Supplement.doc”, caption S2: The scale on horizontal axes also changed for Ba/Ca

Referee Report: PDF

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ED: Publish subject to technical corrections (08 Jul 2015) by Appy Sluijs

AR by Chris Hollis on behalf of the Authors (16 Jul 2015) Author's response Manuscript

Short summary

Re-examination of a Deep Sea Drilling Project sediment core (DSDP Site 277) from the western Campbell Plateau has identified the initial phase of the Paleocene-Eocene Thermal Maximum (PETM) within nannofossil chalk, the first record of the PETM in an oceanic setting in the southern Pacific Ocean (paleolatitude of ~65°S). Geochemical proxies indicate that intermediate and surface waters warmed by ~6° at the onset of the PETM prior to the full development of the negative δ13C excursion.