Basic Role of Extrusion Processes in the Late Cenozoic Evolution of the Western and Central Mediterranean Belts

Round 1

Reviewer 1 Report

Review Report of:

Basic role of extrusion processes in the Late Cenozoic evolution of the Western and Central Mediterranean belts.

By: Viti M., Mantovani E., Babbucci D. and Tamburelli C.

Dear authors,

First of all, thank you for giving me the opportunity to review your work. I have learned a lot in the revision process, and I hope you can publish this work in Geosciences.

This manuscript describes an alternate evolution for the multiple subduction zones in the western and central Mediterranean zones. The authors propose a model where subduction was formed and evolved from the Oligocene to present day, due to the emplacement of lateral extrusion wedges, instead of a slab-retreat mechanism, as defended by the mainstream. This lateral extrusion zones within the Alpine orogen, influenced the migration of subducion zones and basin formation within the Balearic-Apeninic zone in the core of the western Mediterranean realm.

Although the manuscript is well written and organized, it needs some attention in some specific aspects. First, the definition of Arc. This is very confusing, and beyond our scientific grasp, because Arc as a term, has been used for so many different things in geology. For instance, Arc can be used for a magmatic Arc, orogenic Arc and all terms related to it such as forearc, back-arc, etc. Arc is also commonly used for bent orogens. A bent orogen can have different origins as they can be primary or secondary features triggered by internal or external factors. “Arc” in this case includes “oroclines”, “bends”, “syntaxis”, “curves”, and other terms widespread in the bibliography. If I was you, I would use Marshak’s (2004) definition of acuate structures for your study cases, avoiding the term “Arc” for the bent structures identified in the western and central Mediterranean zones. It is a simple but accurate nomenclature that helps to avoid any mistakes. Related to this, the definition of ATBA systems must be revised in my point of view. Maybe you should be more enlightening in describing what they are.

Another aspect that I did not catch was the geometry of the extrusion wedges. Are they thin or thick-skinned? Maybe you should put some general cross sections in each map (from Oligocene to present-day), showing: a) the geometry of the main shear planes that bound the tectonic units, which units are involved in the emplacement of the extrusion wedges (e.g. preferable slide layers, thrusted flysch sediments, etc…), b) the nature of each tectonic slice, c) if there is mantle exhumation in the hyperextended zones, d) the extrusion like a indentor (?), etc... (see, for instance: Jolivet et al., 2021: Jolivet L, Baudin T, Calassou S, Chevrot S, Ford M, Issautier B, Lasseur E, Masini E, Manatschal G, Mouthereau F, Thinon I, Vidal O Geodynamic evolution of a wide plate boundary in the Western Mediterranean, near-field versus far-field interactions. Bulletin de la Societe Geologique de France 192 (1). doi:10.1051/bsgf/2021043).

You can find other comments, reviews and reference suggestions in the attached PDF file.

In this way, I consider the paper fit to be published in MDPI’s Geociences journal, after moderate changes are applied. Even though you probably need to make a/some new figure/s (for me it is critical you make some cross sections for the evolution stages of the region you are describing)  I think you will rapidly solve the problems I have found, and after that the paper should be ready for publish.

Best wishes

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

The scientific problem discussed in this manuscript is important and of interest to the international community. Indeed the Late Cenozoic Mediterranean tectonics remains a fascinating issue, given the complexity of the processes involved, and still widely debated.However, the proposed manuscript is not up to standard for publication.

On formal aspects, I suggest to reduce the amount of repetitions, long sentences, run on sentences and multiple clauses sentences. It will improve the readability of the manuscript. Still on a formal aspect some names used by the authors are not rigorous and may be confusing. For example, in Figures 1 and 2, the authors call "Alpine tethys" the oceanic domain still open after the formation of the Alpine belt.  By definition, however, the "Alpine Tethys" is the ocean that disappeared completely during the Alpine subduction. At least the term "easternmost old Tethys" could be used. Similarly in Figure 1A, it seems that Corsica is not part of the Alpine chain !

From a scientific stand point,  the manuscript has many weaknesses. In the first place, the geological database on which the authors rely is incomplete and references are not up-to-date for many of the areas discussed. This is particularly the case for the Betico-Rifean belt or for Ligurian or southwestern Alps whose complexity of tectonic patterns and geodynamic evolutions remains largely ignored.

The concept of a single "Alpine Iberian Belt"(Figure 2) is an oversimplification.In these various belts, the closed oceanic domains are different, different micro-plates are involved in the convergence and the respective roles of subduction and collision processes are significantly different.

As an example in figure 3A, the opening of the Alboran basin (Lower Miocene in age) is not integrated in the tectonic picture. There are thus many possible confusions for the readers of the manuscript.

The authors claimed that mechanism of formation of the Rhine-Rhone grabben remains to be identified. Numerous publications are available with different proposals for this first order tectonic structure in central Europe !

Surprisingly the origin and characteristics of the volcanism, contemporary of the presented tectonic evolution for the Mediterranean, are not taken into account in the discussion. It is however an important marker of the mantle dynamics which deserves to be considered in the debate "slab-pull versus extrusion models".

In the end, if the idea defended by the authors is interesting, the manuscript, in it's present form, is still too immature.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The presented manuscript proposes new interpretation of the Late Cenozoic tectonic evolution of the Mediterranean area with an interesting focus on development of "Trench-Arc-Back arc" systems.  The premise of the study is commendable, and with respect with the first version of the manuscript I have no doubt that a lot of work went into improving the presentation of the available geological dataset and the quality of the discussion.

In this revised version new figures are proposed, to better illustrate the mechanisms invoked by the authors and additional references reinforce the discussion of the proposed tectonic processes acting in different areas of the studied system. Compared to the first version of this manuscript, the progress in the presentation of the data and the discussion of the different models available on this complex tectonic domain are significant. This is now a welcome contribution which deserve to be published, in particular to provoke new discussions on the evolution of the Mediterranean system, as there remain many uncertainties (contradictions?) in the geodynamic evolution proposed by the authors.