Tectonic processes, variations in sediment flux, and eustatic sea level recorded by the 20&thinsp;Myr old Burdigalian transgression in the Swiss Molasse basin

Garefalakis, Philippos; Schlunegger, Fritz

doi:https://doi.org/10.5194/se-10-2045-2019

Articles | Volume 10, issue 6

https://doi.org/10.5194/se-10-2045-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/se-10-2045-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 10, issue 6

Research article

|

19 Nov 2019

Research article |

| 19 Nov 2019

Tectonic processes, variations in sediment flux, and eustatic sea level recorded by the 20 Myr old Burdigalian transgression in the Swiss Molasse basin

Philippos Garefalakis and Fritz Schlunegger

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Final revised paper (published on 19 Nov 2019)
Supplement to the final revised paper
Preprint (discussion started on 01 Mar 2019)
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Interactive discussion

Status: closed

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

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RC1: 'major revision', Kei Ogata, 14 Mar 2019
- AC1: 'Reply on the comment by reviewer K. Ogata', Philippos Garefalakis, 15 Mar 2019
RC2: 'Discussion comments', Kenneth Eriksson, 12 Jul 2019
- AC2: 'Reply on the comment by reviewer K. Eriksson', Philippos Garefalakis, 05 Aug 2019
RC3: 'Review of paper by Garefalakis and Schlunegger entitled Deciphering tectonic,eustatic and surface controls...', Anonymous Referee #3, 16 Jul 2019
- AC3: 'Reply on the comment by reviewer #3', Philippos Garefalakis, 05 Aug 2019

Peer-review completion

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

AR by Philippos Garefalakis on behalf of the Authors (09 Aug 2019)

ED: Referee Nomination & Report Request started (20 Aug 2019) by Elias Samankassou

RR by Anonymous Referee #3 (12 Sep 2019)

Suggestions for revision or reasons for rejection

Review of the paper by Garefalakis and Schlunegger entitled Deciphering tectonic,eustatic and surface controls on the Burdigalian transgression recorded in the Upper Marine Molasse in Switzerland

General comments
The manuscript has been significantly improved, however there are still some items that need to be improved prior to publication. Detailed examples of problematic areas in the text are given below and in the attached pdf.
Manuscript text needs to be improved. Text often includes long and complicated sentences. Furthermore, the writing style in the manuscript is not balanced. Some chapters such as methods and results are written much better than others. There are still some repetitions in the text.
Discussion needs to be clearer and supported by data and references. 1) Hypothesis stated in the text are often not clarified and adequately explain/supported; 2) Titles do not correlated with the text in subchapters (e.g., Controls on the establishment of a wave-dominated coast in the east and tidal records in the west, page 20); 3) Mixing of poorly or non-related features in the subchapters.
The predominance of tectonics over eustatic sea level effects on marine transgression is poorly explained. In the text, the effect of sea level rise was not discussed, only sea level drop. Fig. 8 shows correlation between sea level rise and OMMI and OMMII. How does tectonics explain westward progression of marine transgression at the base of OMM? How does exhumation of Aar affect lateral variations in wave - vs tide - dominated deposition, but does not affect along-strike coeval appearance of MFS (Fig. 5a)?

Specific comments
Abstract
Very difficult to follow. Goal of the study is missing. Explanation of main finding is vague and confusing. Suggestion > explain the main findings in the same order as listed in the line 17.
Geological settings
The chapter 2.1 seems to be more informative compared to previous manuscript version, however it is difficult to follow. The description of orogen architecture and evolution are mixed. The authors often jump from description of crustal features to lithospheric features and suddenly back again to crust. Process of delamination was described in very confusing way.
Discussion: 6.2. Evolution of the Molasse Basin
It seems that this study mainly confirmed results derived from previous studies e.g. Pfiffner et al., 2002; Kuhlemann and Kempf, 2002 and references therein. If so, than it should be clearly stated at the beginning and this chapter should be shortened. Otherwise, new findings and potential contradictions resulted by this research should be highlighted.
6.3. Controls on the marine transgression of the OMM
This chapter should start with discussion on factors that control transgression i.e. processes that leads to creation of accommodation space more rapidly than it is consumed by sediment supply. For example sea level or processes that control sediment supply. Reversal of the drainage direction might be just a consequence of the process that has not much to do with transgression.
Avoid explaining processes that are not related in the same chapter or explain how they relate (e.g., How are the drainage reversal and basin widening related?, form the text below seems that are not related).
6.3.1 (perhaps) Possible controls on the reversal …
In this subchapter should be listed other hypothesis related to the controls on the reversal (for example rise of Amstetten Swell) and reasons why author prefers Pfiffner’s hypothesis over others. However, It is not clear the link between text that follows and Pfiffner’s hypothesis.
The hypothesis that slab break off/delamination in the Eastern Alps controls drainage reversal is very interesting and novel (although it is vaguely proposed by Handy et al., 2015). Thereby, this should be clearly stated as author’s hypothesis (new contribution to the current knowledge on Molasse basin evolution) and argued why it is favored over other hypothesis. Very important: explanation of independent geological evidences that support this hypothesis are missing. Potential triggering mechanisms of lateral variations in the slab load are poorly explained. For example what would be the wavelength of this process (whole basin and hinterland, part of the basin?)?Suggestion > please avoid citing papers that are not related to the subject, for example Mey et al., 2016, better try with Waschbusch and Royden, 1992 and others.
Controls on the establishment of a wave-dominated coast in the east and tidal records in the west
How is this related to transgression? It is hard to understand how lithospheric-scale processes (slab-roll back mechanism leading to delamination of upper continental crust) are linked to and potentially triggering wave- vs. tide-dominated deposition without taking into account (discussing) other effects (such as wave vs tide energy, tidal waves from Mediterranean and Paratethys, local climate, river discharge).
Regarding the location of the thrust related signal in the basin (page 20, line 20). The Te calculated for the Swiss Alpine foreland varies from 5 to 50 km (Pfiffner et al., 2002 and references therein). Thereby, the location of the expected signal would vary. This might not provide substantial resolution to explain link the location of the bulge and transition from tide- to wave-dominated depositional environment.
Controls on sediment supply and sea levels variations are poorly defined. For example the subchapter on sea level variations gives impression that transgression (with MFS between OMMIa and OMMIb) is controlled by eustatic sea level rise. Sea level rise can induce widening of the basin.
Summary and Conclusions
It is necessary to clearly highlight main conclusion of this study and avoid repetition. Explanation how did tectonic triggered marine ingression into Molasse Basin.

Referee Report: PDF

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ED: Publish subject to minor revisions (review by editor) (19 Sep 2019) by Elias Samankassou

AR by Philippos Garefalakis on behalf of the Authors (26 Sep 2019) Author's response Manuscript

ED: Publish as is (03 Oct 2019) by Elias Samankassou

ED: Publish as is (03 Oct 2019) by Elias Samankassou (Executive editor)

AR by Philippos Garefalakis on behalf of the Authors (08 Oct 2019) Author's response Manuscript

Post-review adjustments

AA: Author's adjustment | EA: Editor approval

AA by Philippos Garefalakis on behalf of the Authors (13 Nov 2019) Author's adjustment Manuscript

EA: Adjustments approved (14 Nov 2019) by Elias Samankassou

Short summary

The controls on the 20 Myr old Burdigalian transgression in the Swiss Molasse basin have been related to a reduction in sediment flux, a rise in global sea level, or tectonic processes in the adjacent Alps. Here, we readdress this problem and extract stratigraphic signals from the Upper Marine Molasse deposits in Switzerland. In conclusion, we consider rollback tectonics to be the main driving force controlling the transgression, which is related to a deepening and widening of the basin.