Reassessing Depositional Conditions of the Pre-Apulian Zone Based on Synsedimentary Deformation Structures during Upper Paleocene to Lower Miocene Carbonate Sedimentation, from Paxoi and Anti-Paxoi Islands, Northwestern End of Greece

Round 1

Reviewer 1 Report

This paper examines soft sediment deformation (SSD) structures from upper palaeocene and lower Miocene carbonates in the Paxoi and Anti-paxoi islands of Greece. Although SSDs are frequently described from clastic sequences, they are also (to a lesser extent) observed in carbonates. My primary expertise is on SSD and I have therefore concentrated on these sections rather then those dealing with more regional geology that I have little experience of. I highlight a few major points below:

1) The text concerning field photographs requires more description of the actual SSD features - rather than a brief note and interpretation.

2) The paper shows some excellent examples of SSD in carbonates – but the reader may be left wondering which exact features are being referred to in the text without; a) more labelling directly on the phots, and b) in some cases an annotated line drawing to highlight the features under consideration.

3) The quality of the English language is reasonable – but could be improved as there are a number of typographical errors. These need to be ‘cleaned -up’.

 

Minor points

Line 50 – Details of seismically generated SSDS in carbonate outcrops is provided by:

Jablonska, D., Di Celma, C., Korneva, I., Tondi, E., Alsop, I. 2016. Mass-transport deposits within basinal carbonates from southern Italy'. Italian Journal of Geosciences, 135, pp. 30-40.

This can be used as a possible guide for some interpretations in this paper

 

Figure 5, 6 – It is important for the reader to identify the erosional contacts adjacent to SSD - so these should be directly labelled on the photographs (there is space without obscuring important geology).

Figure  7- I cant clearly see the two deformed horizons – these must be annotated on the photograph – or produce a line drawing so that the reader can see what is being referred to.

Figure  9- If there are no erosional; contacts with overlying and underlying beds then detachments must have formed to separate the shortened units from undeformed beds. If deformed units are bound by detachments then they could form deeper in the sediment pile after a small amount of burial. This is important for the style and timing of deformation and has been highlighted in a recent paper.

Alsop, G.I., Marco, S., Levi, T. 2022. Recognising surface versus sub-surface deformation of soft-sediments: Consequences and considerations for palaeoseismic studies. Journal of Structural Geology, 154, 104493. https://doi.org/10.1016/j.jsg.2021.104493

It would be interesting to know if any of the features described in this paper are indeed present in the carbonate examples?

 

Figure 11 – This shows a highly irregular upper contact to the SSD that supports the authors statement of an erosional upper surface. This should perhaps be highlighted more (on the photo) as it demonstrates surficial deformation (in this case!).

Line 246 – You refer to synthetic and antithetic normal faults – but nowhere define what you mean. Synthetic normal faults have previously been defined as dipping in the slope (movement) direction whereas antithetic faults dip upslope.

 

Line 254 – “Synthetic and antithetic normal faults pre-exist the deformation, produced the necessary unstability conditions for the slumping triggering.” I think you need to explain more clearly the evidence that is being used to support the timing of events – why are the normal faults earlier rather than synchronous??

 

Figure 13c – The folds close in opposing directions – but that does not necessarily mean that deformation propagates in opposing directions (yellow arrows). Recumbent synclines and anticlines closing in opposing directions can form during the same sense of movement.

 

Figure 14 – The substrate to slumps and MTDs can be deformed as the overlying MTD moves over it. You note this and this may be the most likely explanation.

In general you need a more detailed description of the observations from each field photograph (Figs 5-16) rather than an interpretation. I suspect there is a lot more detail that could be gained from these excellent coastal exposures.

 

Figure 16 – An alternative explanation could be that the normal fault is later and cuts across the SSD horizons?

Author Response

Comment 1: The text concerning field photographs requires more description of the actual SSD features - rather than a brief note and interpretation.

Comment 2: The paper shows some excellent examples of SSD in carbonates – but the reader may be left wondering which exact features are being referred to in the text without; a) more labelling directly on the phots, and b) in some cases an annotated line drawing to highlight the features under consideration.

More details added on the figures, as suggested, highlighting some special features like erosional surfaces, and some more descriptions on the text, as suggested.

I would like to thank reviewer for his/her comments but I would like to inform reviewer that the aim/ target of this work is not the classification of the SSD structures but to use them as indicators for basin evolution, tectonic regime e.t.c.

In a previous work we have done this classification (see our paper Bourli, N.; Maravelis, A.G.; Zelilidis, A. Classification of soft‑sediment deformation in carbonates based on the Lower Cretaceous Vigla Formation, Kastos, Greece. International Journal of Earth Sciences 2020, 109, 2599–2614, that was reviewed by Prof. Alsop) and we will continue working on this, probably using the pre-existing models.

 

Comment 3: The quality of the English language is reasonable – but could be improved as there are a number of typographical errors. These need to be ‘cleaned -up’.

We worked on this, and I think that ms now is improved.

 

In detail for the Minor points:

Comment 1

Line 50 – Details of seismically generated SSDS in carbonate outcrops is provided by:

Jablonska, D., Di Celma, C., Korneva, I., Tondi, E., Alsop, I. 2016. Mass-transport deposits within basinal carbonates from southern Italy'. Italian Journal of Geosciences, 135, pp. 30-40.

This can be used as a possible guide for some interpretations in this paper.

 

The suggested paper added in the text (see also my comment 2 above)

 

Comments 2-5

 Figure 5, 6 – It is important for the reader to identify the erosional contacts adjacent to SSD - so these should be directly labelled on the photographs (there is space without obscuring important geology).

Figure  7- I cant clearly see the two deformed horizons – these must be annotated on the photograph – or produce a line drawing so that the reader can see what is being referred to.

Figure  9- If there are no erosional; contacts with overlying and underlying beds then detachments must have formed to separate the shortened units from undeformed beds. If deformed units are bound by detachments then they could form deeper in the sediment pile after a small amount of burial. This is important for the style and timing of deformation and has been highlighted in a recent paper.

Alsop, G.I., Marco, S., Levi, T. 2022. Recognizing surface versus sub-surface deformation of soft-sediments: Consequences and considerations for palaeoseismic studies. Journal of Structural Geology, 154, 104493. https://doi.org/10.1016/j.jsg.2021.104493

It would be interesting to know if any of the features described in this paper are indeed present in the carbonate examples?

 Figure 11 – This shows a highly irregular upper contact to the SSD that supports the authors statement of an erosional upper surface. This should perhaps be highlighted more (on the photo) as it demonstrates surficial deformation (in this case!).

 

Suggestions have been accepted and figures 5-16 improved. We know the work of Prof. Alsop but the aim of the present work focuses in different target.

 

Comments 6-7

Line 246 – You refer to synthetic and antithetic normal faults – but nowhere define what you mean. Synthetic normal faults have previously been defined as dipping in the slope (movement) direction whereas antithetic faults dip upslope.

Yes we agree and the text now explain clearly the status: Normal faults are responsible for the instability of basin floor and the SSD structures development whereas the antithetic faults act as the barge where the movement sopped.

 

 Line 254 – “Synthetic and antithetic normal faults pre-exist the deformation, produced the necessary unstability conditions for the slumping triggering.” I think you need to explain more clearly the evidence that is being used to support the timing of events – why are the normal faults earlier rather than synchronous??

Yes, we agree and the text now explain clearly the status: Synthetic and antithetic normal acting synchronously with the deformation produced the necessary instability conditions for the slumping triggering.

 

Comments 8-10

 

Figure 13c – The folds close in opposing directions – but that does not necessarily mean that deformation propagates in opposing directions (yellow arrows). Recumbent synclines and anticlines closing in opposing directions can form during the same sense of movement.

 Figure 14 – The substrate to slumps and MTDs can be deformed as the overlying MTD moves over it. You note this and this may be the most likely explanation.

In general you need a more detailed description of the observations from each field photograph (Figs 5-16) rather than an interpretation. I suspect there is a lot more detail that could be gained from these excellent coastal exposures.

Figure 16 – An alternative explanation could be that the normal fault is later and cuts across the SSD horizons?

 

We agree with the first comment and an explanation was wrote in the ms.

We agree with the reviewer about point 2 (figure 14), and a clear explanation we gave for the fault activity, regarding the comment for figure 16.

Author Response File: Author Response.pdf

Reviewer 2 Report

Reassessing Depositional Conditions of the Pre-Apulian Zone Based on Synsedimentary Deformation Structures During Upper Paleocene to Lower Miocene Carbonate Sedimentation, From Paxoi and Anti-Paxoi islands, Northwestern end of Greece

By Nicolina Bourli, George Iliopoulos, and Avraam Zelilidis

This study was based on the microfacies and soft sediment deformation (SSD) structures to study the depositional environment conditions of the carbonate sequence in Paxoi and Anti-Paxoi islands. The SSD is most developed toward the subsided fault planes. The development of SSD indicates the tectonic activities getting more intense from Eocene to Miocene. The presentation is well settled in this manuscript.

A few points needs extra clarify:

 Line 143, “There is a transition … Miocene (as we moved northwards or southwards).” Which direction should see Miocene? Should be north? (in Line 141, north side is younger: “It seems that the younger deposits are restricted both in the northern part of the Paxoi Island”).

Table 1. (SMF/FZ) “Standard microfacies and Facies Zones?” need notes and reference.

Table 1, Row 1, fossil column, typo, “rotaliidae”.

Table 1. Row 24, “Late Eocene”. This is the only row used “late”, not the “upper”.

Table 1. Can the “characteristic fossils assemblages” of different ages (Eocene to Miocene) be highlighted in the table?

Figure 4. Brown color of Paxio Island makes all labels not distinguishable, may need to change to lighter color. And increase all the font of “figure #”.

Line 153 “ … is of late Eocene age (Figure 4).” Since Table 1 redefined the ages of the “geological map age”. A paragraph to explain how the new ages are defined seems necessary here.

Line 160, “…mostly the regional tectonic influence than the total change of the basin configuration.” Basin development is usually corresponding to the tectonic evolution. It needs more specify what the relationship was between the basin configuration and tectonic feature in the region during Cenozoic.

Line 162, “…idea of the regional tectonic influence but…” what kind of tectonic influence?

Figure 5 to Figure 10 presented SSD horizons in Paxoi Island. If the age information can be added, or there is a link between Figures with Table 1. It will be more helpful to the readers.

Line 290, 5.3. General Results Based on the SSD Structures. If this section presents the links to Figures 5 to 16, it will be helpful. Such as line 298-299, which SSD structures are referred in this sentence?

Line 363-365, “…the thickness … between them.” Is there any presented figure can be referred here?

Author Response

Concerning the reviewer 2 comments:

 Line 143, “There is a transition … Miocene (as we moved northwards or southwards).” Which direction should see Miocene? Should be north? (in Line 141, north side is younger: “It seems that the younger deposits are restricted both in the northern part of the Paxoi Island”).

 

We accept the comment and the ms now includes the explanation

 

Table 1. (SMF/FZ) “Standard microfacies and Facies Zones?” need notes and reference.

 

We agree with the comment and now in figure caption the used literature is mentioned.

 

Table 1, Row 1, fossil column, typo, “rotaliidae”.

Table 1. Row 24, “Late Eocene”. This is the only row used “late”, not the “upper”.

 

We accept the comments and the table now is improved

 

Table 1. Can the “characteristic fossils assemblages” of different ages (Eocene to Miocene) be highlighted in the table?

We accept the comment and in the new table this is highlighted.

 

Figure 4. Brown color of Paxio Island makes all labels not distinguishable, may need to change to lighter color. And increase all the font of “figure #”.

 

We accept the comment and the new figure 4 is according the suggestions.

 

Line 153 “ … is of late Eocene age (Figure 4).” Since Table 1 redefined the ages of the “geological map age”. A paragraph to explain how the new ages are defined seems necessary here.

 

Line 160, “…mostly the regional tectonic influence than the total change of the basin configuration.” Basin development is usually corresponding to the tectonic evolution. It needs more specify what the relationship was between the basin configuration and tectonic feature in the region during Cenozoic.

Line 162, “…idea of the regional tectonic influence but…” what kind of tectonic influence?

 

We accept the comments and new details were added in order to show and explain the questions.

 

Figure 5 to Figure 10 presented SSD horizons in Paxoi Island. If the age information can be added, or there is a link between Figures with Table 1. It will be more helpful to the readers.

 

We accept the comment and details were added to the figure captions.

 

Line 290, 5.3. General Results Based on the SSD Structures. If this section presents the links to Figures 5 to 16, it will be helpful. Such as line 298-299, which SSD structures are referred in this sentence?

Line 363-365, “…the thickness … between them.” Is there any presented figure can be referred here?

 

We accept the comments and we improved the ms in order to show and explain the questions.

Author Response File: Author Response.pdf