Analogue experiments on releasing and restraining bends and their application to the study of the Barents Shear Margin

Gabrielsen, Roy Helge; Giennenas, Panagiotis Athanasios; Sokoutis, Dimitrios; Willingshofer, Ernst; Hassaan, Muhammad; Faleide, Jan Inge

doi:https://doi.org/10.5194/egusphere-2023-10

Preprints

https://doi.org/10.5194/egusphere-2023-10

Preprints

13 Jan 2023

| 13 Jan 2023

Analogue experiments on releasing and restraining bends and their application to the study of the Barents Shear Margin

Roy Helge Gabrielsen, Panagiotis Athanasios Giennenas, Dimitrios Sokoutis, Ernst Willingshofer, Muhammad Hassaan, and Jan Inge Faleide

Abstract. The Barents Shear Margin separates the Svalbard and Barents Sea from the North Atlantic. It includes one northern (Hornsund Fault Zone) and a southern (Senja Fracture Zone) margin segment in which structuring was dominated by dextral shear. These segments are separated by the Vestbakken Volcanic Province that rests in a releasing bend position between the two. During the break-up of the North Atlantic the plate tectonic configuration was characterized by sequential dextral shear, extension, contraction and inversion. This generated a complex zone of deformation that contain several structural families of over-lapping and reactivated structures Although the convolute structural pattern associated with the Barents Shear Margin has been noted, it has not yet been explained in this framework.

A series of crustal-scale analogue experiments, utilizing a scaled stratified sand-silicon polymer sequence, serve to study the structural evolution of the shear margin in response to shear deformation along a pre-defined boundary representing the geometry of the Barents Shear Margin and variations in kinematic boundary conditions of subsequent deformation events, i.e. direction of extension and inversion. The observations that are of particular significance for interpretating the structural configuration of the Barents Shear Margin are:

1) The experiments reproduced the geometry and positions of the major basins and relations between structural elements (fault and fold systems) as observed along and adjacent to the Barents Shear Margin. This supports the present structural model for the shear margin.

2) Several of the structural features that were initiated during the early (dextral shear) stage became overprinted and obliterated in the subsequent stages.

3) Prominent early-stage positive structural elements (e.g. folds, push-ups) interacted with younger (e.g. inversion) structures and contributed to a complex final structural pattern.

4) All master faults, pull-part basins and extensional shear duplexes initiated during the shear stage quickly became linked in the extension stage, generating a connected basin system along the entire shear margin at the stage of maximum extension.

5) The fold pattern generated during the terminal stage (contraction/inversion became dominant in the basinal areas and was characterized by fold axes with traces striking parallel to the basin margins. These folds, however, most strongly affected the shallow intra-basinal layers. This is in general agreement with observations in previous and new reflection seismic data from the Barents Shear Margin.

Received: 03 Jan 2023 – Discussion started: 13 Jan 2023

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Journal article(s) based on this preprint

31 Aug 2023

Analogue experiments on releasing and restraining bends and their application to the study of the Barents Shear Margin

Roy Helge Gabrielsen, Panagiotis Athanasios Giannenas, Dimitrios Sokoutis, Ernst Willingshofer, Muhammad Hassaan, and Jan Inge Faleide

Solid Earth, 14, 961–983, https://doi.org/10.5194/se-14-961-2023,https://doi.org/10.5194/se-14-961-2023, 2023

Short summary

Roy Helge Gabrielsen, Panagiotis Athanasios Giennenas, Dimitrios Sokoutis, Ernst Willingshofer, Muhammad Hassaan, and Jan Inge Faleide

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2023-10', Anonymous Referee #1, 20 Feb 2023

Please see attached file.

Citation: https://doi.org/10.5194/egusphere-2023-10-RC1
- AC1: 'Reply on RC1', Roy H. Gabrielsen, 27 Mar 2023
  
  Both reviewers find the regional information to be too extensive and repetitive. Several changes have been done to avoid this (see detailed comments related to comments from Reviewer 2) below. Reviewer 1 found the sequence of presentations of structural elements to be non-intuitive. We have restructured this section so that regional structural elements are presented in sequence from north to south.
  Details about the experimental set-up and dimensions are given in the introduction to the Experiments and in Figure 3B (perhaps overlooked by reviewer?). An addendum D to Figure 3 (photograph) has been produced to highlight the varying width of the silicone putty as described in the text. Expanding the modelling setup description as requested by the reviewer is at variance with the opinion of reviewer 2, who wants us to shorten the modelling setup section.
  We agree that using PIV methods would allow for a quantitative analysis of the modelling results. Such analysis has previously been performed by us (Leever et al., 2011) in context of strain partitioning in a shear margin environment. Besides that, the reasons why we refrained adding this method are as follows: 1. As PIV software relies on pattern recognition algorithms applied to successive top-view photographs, adding syn-tectonic sedimentation during the model runs, significantly alters the pattern and adds a big deal of uncertainty to the areas where sedimentation has been applied. As such we feel that a qualitative analysis of the models based on top-view and cross-section images allows for a more detailed and accurate description of the models. 2. focusing on the regional aspects of the Barents Shear Margin in this paper, we found that a full PIV-analysis would take much space and attention, and that this would fit better into an article that would be dedicated to the experimental methods and analysis. For the reasons above we prefer to stick to the model analysis as presented, which in our view is sufficiently well aligned with the available kinematic and geometric data from the natural laboratory.
  We have tried to focus the discussion on the application of the modelling results on the Barents Sea problems. The discussion and conclusions have been clarified and sharpened on the points requested by reviewer.
  Figures/figure captions 1, 2, 3, 5, 6, 7, 9 and 10 have been revised according to comments by the reviewer (specified below).
  Grammar and spelling. The manuscript has been run through word spell- and grammar checks. Misprints and unclear phrasings identified by the reviewer have been corrected. The reviewer has identified some sections with long/complex phrasings. These have been rewritten/simplified.
  Specific comments
  Lines 148-151 (R1): This section has been expanded and specified when it comes to specification of general problems related to the analyzed area.
  Line 165 (R1): The relation between the Barents shear margin and the de Geer zone has been specified.
  Lines 167ff (R1): “Structuring” has been changed to “structural development” throughout the manuscript.
  Line 175 (R1): Moved to Senja shear margin as suggested.
  Line180 (R1): Basin name has been included
  Line 208ff: (R1) Presentation/description of the Vestbakken Volcanic Province to be moved? We have restructured this section so that regional structural elements are presented in sequence from north to south.
  Line 232 (R1): The reference given concerns the two last sentences in the section.
  Line 250 (R1): Changed to “linked”
  Lines 294ff (R1): Reformulation as suggested.
  Lines 330ff (R1): Introduction to this section rewritten.
  Line 331 (R1): Reference to Fold family 3 taken out. (Not used in the following).
  Line 389 (R1): Process for determining taper angle included.
  
  Lines 405-413 (R1): Not sure we understand this remark. This describes the experimental set-up and are not results.
  Lines 425ff (R1): As described above/below, the angles were chosen according to the analysis of the opening and plate movements by Gaina et al. (2009), see above, the introductory remarks to Descriptions and Discussion. We have added a sentence to underline that here.
  Line 429 (R1): Sieve was applied to obtain a smooth surface. Explanation added.
  Lines 443-447 (R1): The shape of the silicone putty lid followed the geometry determined from seismic mapping, as described in the following sentence: “Additionally, an 8 mm thick and of variable width corresponding to the mapped transition zone”. A parantheses has been added to state this even more clearly.
  Lines 467-447 (R1): We have used PIV-methods in previous studies (e.g. Leever et al. 2011a,b). Although favourable for a dedicated experimental work, we feel that the present work mainly addresses regional issues and that the use of PIV-method would seriously expand the text. We still acknowledge this remark and consider writing a pure geometrical version of these results (with some added examples/complexities) to be published separately.
  Lines 499-501 (R1: The Reviewer is correct that this may seem obvious. We still feel the need to stress that the positive structures include elements of different types that are not easily distinguished when first detected and monitored thereafter (Figure 7), and that a classification must await the cutting of the experiments. We have therefore chosen to keep this sentence as it is.
  Line 504 (R1): A section has been added here to introduce the reader to the different structure types. We have not used the term “SPSE” as referred to by the Reviewer, but the Reviewer is correct that “EPS” occurs a couple of places in the text. These are misprints for PSE (Positive Structural Element) and have been corrected.
  Line 534 (R1): The continuation of the sentence says what kind of structures which was requested by the Reviewer, namely: «a system of en échelon separate N-S to NNE-SSE- striking normal and shear fault segments». We feel that the requested information is given and have therefore kept the sentence as it is.
  Lines 536-538 (R1): The full terms and short explanations have been added in parentheses.
  Lines 592-594 (R1): The description has been rewritten and expanded.
  Lines 650ff (R1): Y-shears have been identified in Figure 8.
  Lines 652-654 (R1): This is concluded from the present experiments and documented in Figures 5,6 and 10 as referred in the text.
  Lines 657-659 (R1): See explanations to line 443-447 above.
  Line 694 (R1): This is just an observation done during the present experiments. We are not aware of other experiments that describes the temporal aspects of fault linkage. We have however determined the process to have taken place between .25 an .50 cm of displacement, and since the velocity of the experiment is known, the timing can be calculated. We did not have any ambition of representing this part of the development in a scaled timeframe, and doubt that this would be scientifically meaningful. We have therefore not changed the text on this point.
  Line 713 (R1): The opening velocity is known for the NE-Atlantic (e.g., Gaina et al. 2009). Furthermore, we know that the bulk extension vector was greater than the extension factor by adding up extension and shortening (Vågnes et al. 1997). These references that are referred to elsewhere in the text, have been added here.
  Line 744 (R1): Changed to “stress configuration”.
  Lines 745-763 (R1): The regional summary has been taken out to avoid repetition.
  Lines 762-763 (R1): “Structural development” has been substituted for “complexities”.
  Lines 777-782 (R1): Section expanded and re-written.
  Lines 785-786 (R1): Redundant statement obliterated.
  Lines 790-792 (R1): The basin linking situation has been specified.
  Lines 798-800 (R1): The segments are identified and labelled in Figure 4, so a reference to that figure has been included.
  Line 827 (R1): Statement has been reformulated to focus on the influence of mechanically stratified sequences on fold configurations.
  Line 844 (R1): This is a misprint. Should read “PSE-structure”. Misprint corrected.
  Lines 884-887 (R1): Sentence has been simplified.
  Lines 972-973 (R1): The section has been re-written and the conclusions have been substantiated.
  Line 990 (R1): Statement clarified.
  
  Additional technical comments (Reviewer 1):
  All technical errors (misprints) pointed to have been corrected
  Line 480: Sentence reformulated
  Lines 773-774: Section re-written
  Line 777: Rephrased
  Lines 814-819: Section rewritten
  Lines 927-927: Section rephrased.
  
  Figures (additions requested by reviewers)
  Figure 1. Missing names (abbreviations) in Figure 1B in map and figure caption have been added/harmonized. We have changed the sequence of abbreviations in the figure captions so that structural elements are presented in sequence from north to south to enhance readability.
  Figure 2: Seismic examples has been added and abbreviations of structural types (PSE’s) have been added. Figure caption has been expanded accordingly.
  Figure 3: Picture has been added (Figure 3D) and cartoon (Fig. 3A) to display the true geometry of the silicone putty layer.
  Figure 5: Magnified scale bar has been added.
  Figure 6: Information has been added for each frame to emphasize key structural elements and configuration/deformation stage. Magnified scale bar has been added.
  Figure 7: Y-shears and scale (previously given I caption) have been emphasized.
  Table 1: Table has been added more clearly to identify and explain positive structural element types (PSEs). References to figures that illustrate the different PSE-types have been added.
  Figure captions have been revised in harmony with revisions of figures.
  
  Citation: https://doi.org/10.5194/egusphere-2023-10-AC1
RC2:
'Comment on egusphere-2023-10', Anonymous Referee #2, 25 Feb 2023

This manuscript presents seismic profiles and analog modeling to discuss the formation of the Barents Shear Margin. Reviewing such a long manuscript really tasks me, especially that the poor preparation of figures. I cannot find geological units, such as Senja shear margin, Hornsund fault zone, and many other names referred in the text. Even the structures in figure and captions are not matched. Another issue is that too much and redundant description of results prevents me understanding the key evidence and motivation of this work. The text can be shortened by half if they want to have a clearly written paper. I therefore suggest returning this manuscript to authors for a major revision by deleting and combining unnecessary parts, and highlighting the finding or importance of this work. See details in the attached file.

Citation: https://doi.org/10.5194/egusphere-2023-10-RC2
- AC2: 'Reply on RC2', Roy H. Gabrielsen, 27 Mar 2023
  
  Abstract has been shortened, omitting general regional information that can be read from the general introduction. Main conclusions have been high-lighted.
  Regional descriptions have been modified and simplified to ease discussions of regional structures. Some parts that refer to previous descriptions (like fold families) have been omitted to avoid confusion between present (PSE) and previous nomenclature.
  Reference to both seismic interpretations and experimental results have been strengthened and Figure 2 has been expanded to strengthen the relation between observations in reflection seismic data and experiments.
  Figures and related text in manuscript have been revised/harmonized to enhance clarity.
  Discussion of regional aspects have been simplified on several points.
  Reviewer 2 expresses concern about how the geometry of the shear margin (e.g. area of crustal thinning) was constrained. This is fully based on seismic mapping and an additional figure (Figure 3D) has been prepared to display the configuration (see comments to figures below).
  We have found that taking out lines 449-458 as suggested by Reviewer 2 is at variance with the opinion of Reviewer 1 who wants us to expand on the model setup and scaling section. As these lines contain among others critical information on the length-scale ratio, we did not find it logic to remove this information from the text.
  Specific comments Reviewers 2
  Line 170 (R2): Further description of these segments follows in lines 175.
  Line 188 (R2): Sedimentary thickness specified.
  Line 212 (R2): The relative positions of the Sørvestsnaget Basin and the Senja Ridge have been emphasized.
  Line 225 (R2): Rephrased
  Line 246 (R2): The square in the pdf-file is l in the word document. The l was transformed by the building of the pdf-document.
  Line 271 (R2): Misprint. Figure-reference taken out.
  Line 273 (R2): Sentence has been removed.
  NB: Line 442 (R2): The unit is mm (as seen in word-file). Comes out as square in the pdf-file that was generated in the editorial procedure.
  Lines 449-458 (R2): Information on scaling: See comment under “General comments from Reviewer 2” above.
  Figures (additions requested by reviewers)
  Figure 1. Missing names (abbreviations) in Figure 1B in map and figure caption have been added/harmonized. We have changed the sequence of abbreviations in the figure captions so that structural elements are presented in sequence from north to south to enhance readability.
  Figure 2: Seismic examples has been added and abbreviations of structural types (PSE’s) have been added. Figure caption has been expanded accordingly.
  Figure 3: Picture has been added (Figure 3D) and cartoon (Fig. 3A) to display the true geometry of the silicone putty layer.
  Figure 5: Magnified scale bar has been added.
  Figure 6: Information has been added for each frame to emphasize key structural elements and configuration/deformation stage. Magnified scale bar has been added.
  Figure 7: Y-shears and scale (previously given I caption) have been emphasized.
  Table 1: Table has been added more clearly to identify and explain positive structural element types (PSEs). References to figures that illustrate the different PSE-types have been added.
  Figure captions have been revised in harmony with revisions of figures.
  
  Citation: https://doi.org/10.5194/egusphere-2023-10-AC2

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2023-10', Anonymous Referee #1, 20 Feb 2023

Please see attached file.

Citation: https://doi.org/10.5194/egusphere-2023-10-RC1
- AC1: 'Reply on RC1', Roy H. Gabrielsen, 27 Mar 2023
  
  Both reviewers find the regional information to be too extensive and repetitive. Several changes have been done to avoid this (see detailed comments related to comments from Reviewer 2) below. Reviewer 1 found the sequence of presentations of structural elements to be non-intuitive. We have restructured this section so that regional structural elements are presented in sequence from north to south.
  Details about the experimental set-up and dimensions are given in the introduction to the Experiments and in Figure 3B (perhaps overlooked by reviewer?). An addendum D to Figure 3 (photograph) has been produced to highlight the varying width of the silicone putty as described in the text. Expanding the modelling setup description as requested by the reviewer is at variance with the opinion of reviewer 2, who wants us to shorten the modelling setup section.
  We agree that using PIV methods would allow for a quantitative analysis of the modelling results. Such analysis has previously been performed by us (Leever et al., 2011) in context of strain partitioning in a shear margin environment. Besides that, the reasons why we refrained adding this method are as follows: 1. As PIV software relies on pattern recognition algorithms applied to successive top-view photographs, adding syn-tectonic sedimentation during the model runs, significantly alters the pattern and adds a big deal of uncertainty to the areas where sedimentation has been applied. As such we feel that a qualitative analysis of the models based on top-view and cross-section images allows for a more detailed and accurate description of the models. 2. focusing on the regional aspects of the Barents Shear Margin in this paper, we found that a full PIV-analysis would take much space and attention, and that this would fit better into an article that would be dedicated to the experimental methods and analysis. For the reasons above we prefer to stick to the model analysis as presented, which in our view is sufficiently well aligned with the available kinematic and geometric data from the natural laboratory.
  We have tried to focus the discussion on the application of the modelling results on the Barents Sea problems. The discussion and conclusions have been clarified and sharpened on the points requested by reviewer.
  Figures/figure captions 1, 2, 3, 5, 6, 7, 9 and 10 have been revised according to comments by the reviewer (specified below).
  Grammar and spelling. The manuscript has been run through word spell- and grammar checks. Misprints and unclear phrasings identified by the reviewer have been corrected. The reviewer has identified some sections with long/complex phrasings. These have been rewritten/simplified.
  Specific comments
  Lines 148-151 (R1): This section has been expanded and specified when it comes to specification of general problems related to the analyzed area.
  Line 165 (R1): The relation between the Barents shear margin and the de Geer zone has been specified.
  Lines 167ff (R1): “Structuring” has been changed to “structural development” throughout the manuscript.
  Line 175 (R1): Moved to Senja shear margin as suggested.
  Line180 (R1): Basin name has been included
  Line 208ff: (R1) Presentation/description of the Vestbakken Volcanic Province to be moved? We have restructured this section so that regional structural elements are presented in sequence from north to south.
  Line 232 (R1): The reference given concerns the two last sentences in the section.
  Line 250 (R1): Changed to “linked”
  Lines 294ff (R1): Reformulation as suggested.
  Lines 330ff (R1): Introduction to this section rewritten.
  Line 331 (R1): Reference to Fold family 3 taken out. (Not used in the following).
  Line 389 (R1): Process for determining taper angle included.
  
  Lines 405-413 (R1): Not sure we understand this remark. This describes the experimental set-up and are not results.
  Lines 425ff (R1): As described above/below, the angles were chosen according to the analysis of the opening and plate movements by Gaina et al. (2009), see above, the introductory remarks to Descriptions and Discussion. We have added a sentence to underline that here.
  Line 429 (R1): Sieve was applied to obtain a smooth surface. Explanation added.
  Lines 443-447 (R1): The shape of the silicone putty lid followed the geometry determined from seismic mapping, as described in the following sentence: “Additionally, an 8 mm thick and of variable width corresponding to the mapped transition zone”. A parantheses has been added to state this even more clearly.
  Lines 467-447 (R1): We have used PIV-methods in previous studies (e.g. Leever et al. 2011a,b). Although favourable for a dedicated experimental work, we feel that the present work mainly addresses regional issues and that the use of PIV-method would seriously expand the text. We still acknowledge this remark and consider writing a pure geometrical version of these results (with some added examples/complexities) to be published separately.
  Lines 499-501 (R1: The Reviewer is correct that this may seem obvious. We still feel the need to stress that the positive structures include elements of different types that are not easily distinguished when first detected and monitored thereafter (Figure 7), and that a classification must await the cutting of the experiments. We have therefore chosen to keep this sentence as it is.
  Line 504 (R1): A section has been added here to introduce the reader to the different structure types. We have not used the term “SPSE” as referred to by the Reviewer, but the Reviewer is correct that “EPS” occurs a couple of places in the text. These are misprints for PSE (Positive Structural Element) and have been corrected.
  Line 534 (R1): The continuation of the sentence says what kind of structures which was requested by the Reviewer, namely: «a system of en échelon separate N-S to NNE-SSE- striking normal and shear fault segments». We feel that the requested information is given and have therefore kept the sentence as it is.
  Lines 536-538 (R1): The full terms and short explanations have been added in parentheses.
  Lines 592-594 (R1): The description has been rewritten and expanded.
  Lines 650ff (R1): Y-shears have been identified in Figure 8.
  Lines 652-654 (R1): This is concluded from the present experiments and documented in Figures 5,6 and 10 as referred in the text.
  Lines 657-659 (R1): See explanations to line 443-447 above.
  Line 694 (R1): This is just an observation done during the present experiments. We are not aware of other experiments that describes the temporal aspects of fault linkage. We have however determined the process to have taken place between .25 an .50 cm of displacement, and since the velocity of the experiment is known, the timing can be calculated. We did not have any ambition of representing this part of the development in a scaled timeframe, and doubt that this would be scientifically meaningful. We have therefore not changed the text on this point.
  Line 713 (R1): The opening velocity is known for the NE-Atlantic (e.g., Gaina et al. 2009). Furthermore, we know that the bulk extension vector was greater than the extension factor by adding up extension and shortening (Vågnes et al. 1997). These references that are referred to elsewhere in the text, have been added here.
  Line 744 (R1): Changed to “stress configuration”.
  Lines 745-763 (R1): The regional summary has been taken out to avoid repetition.
  Lines 762-763 (R1): “Structural development” has been substituted for “complexities”.
  Lines 777-782 (R1): Section expanded and re-written.
  Lines 785-786 (R1): Redundant statement obliterated.
  Lines 790-792 (R1): The basin linking situation has been specified.
  Lines 798-800 (R1): The segments are identified and labelled in Figure 4, so a reference to that figure has been included.
  Line 827 (R1): Statement has been reformulated to focus on the influence of mechanically stratified sequences on fold configurations.
  Line 844 (R1): This is a misprint. Should read “PSE-structure”. Misprint corrected.
  Lines 884-887 (R1): Sentence has been simplified.
  Lines 972-973 (R1): The section has been re-written and the conclusions have been substantiated.
  Line 990 (R1): Statement clarified.
  
  Additional technical comments (Reviewer 1):
  All technical errors (misprints) pointed to have been corrected
  Line 480: Sentence reformulated
  Lines 773-774: Section re-written
  Line 777: Rephrased
  Lines 814-819: Section rewritten
  Lines 927-927: Section rephrased.
  
  Figures (additions requested by reviewers)
  Figure 1. Missing names (abbreviations) in Figure 1B in map and figure caption have been added/harmonized. We have changed the sequence of abbreviations in the figure captions so that structural elements are presented in sequence from north to south to enhance readability.
  Figure 2: Seismic examples has been added and abbreviations of structural types (PSE’s) have been added. Figure caption has been expanded accordingly.
  Figure 3: Picture has been added (Figure 3D) and cartoon (Fig. 3A) to display the true geometry of the silicone putty layer.
  Figure 5: Magnified scale bar has been added.
  Figure 6: Information has been added for each frame to emphasize key structural elements and configuration/deformation stage. Magnified scale bar has been added.
  Figure 7: Y-shears and scale (previously given I caption) have been emphasized.
  Table 1: Table has been added more clearly to identify and explain positive structural element types (PSEs). References to figures that illustrate the different PSE-types have been added.
  Figure captions have been revised in harmony with revisions of figures.
  
  Citation: https://doi.org/10.5194/egusphere-2023-10-AC1
RC2:
'Comment on egusphere-2023-10', Anonymous Referee #2, 25 Feb 2023

This manuscript presents seismic profiles and analog modeling to discuss the formation of the Barents Shear Margin. Reviewing such a long manuscript really tasks me, especially that the poor preparation of figures. I cannot find geological units, such as Senja shear margin, Hornsund fault zone, and many other names referred in the text. Even the structures in figure and captions are not matched. Another issue is that too much and redundant description of results prevents me understanding the key evidence and motivation of this work. The text can be shortened by half if they want to have a clearly written paper. I therefore suggest returning this manuscript to authors for a major revision by deleting and combining unnecessary parts, and highlighting the finding or importance of this work. See details in the attached file.

Citation: https://doi.org/10.5194/egusphere-2023-10-RC2
- AC2: 'Reply on RC2', Roy H. Gabrielsen, 27 Mar 2023
  
  Abstract has been shortened, omitting general regional information that can be read from the general introduction. Main conclusions have been high-lighted.
  Regional descriptions have been modified and simplified to ease discussions of regional structures. Some parts that refer to previous descriptions (like fold families) have been omitted to avoid confusion between present (PSE) and previous nomenclature.
  Reference to both seismic interpretations and experimental results have been strengthened and Figure 2 has been expanded to strengthen the relation between observations in reflection seismic data and experiments.
  Figures and related text in manuscript have been revised/harmonized to enhance clarity.
  Discussion of regional aspects have been simplified on several points.
  Reviewer 2 expresses concern about how the geometry of the shear margin (e.g. area of crustal thinning) was constrained. This is fully based on seismic mapping and an additional figure (Figure 3D) has been prepared to display the configuration (see comments to figures below).
  We have found that taking out lines 449-458 as suggested by Reviewer 2 is at variance with the opinion of Reviewer 1 who wants us to expand on the model setup and scaling section. As these lines contain among others critical information on the length-scale ratio, we did not find it logic to remove this information from the text.
  Specific comments Reviewers 2
  Line 170 (R2): Further description of these segments follows in lines 175.
  Line 188 (R2): Sedimentary thickness specified.
  Line 212 (R2): The relative positions of the Sørvestsnaget Basin and the Senja Ridge have been emphasized.
  Line 225 (R2): Rephrased
  Line 246 (R2): The square in the pdf-file is l in the word document. The l was transformed by the building of the pdf-document.
  Line 271 (R2): Misprint. Figure-reference taken out.
  Line 273 (R2): Sentence has been removed.
  NB: Line 442 (R2): The unit is mm (as seen in word-file). Comes out as square in the pdf-file that was generated in the editorial procedure.
  Lines 449-458 (R2): Information on scaling: See comment under “General comments from Reviewer 2” above.
  Figures (additions requested by reviewers)
  Figure 1. Missing names (abbreviations) in Figure 1B in map and figure caption have been added/harmonized. We have changed the sequence of abbreviations in the figure captions so that structural elements are presented in sequence from north to south to enhance readability.
  Figure 2: Seismic examples has been added and abbreviations of structural types (PSE’s) have been added. Figure caption has been expanded accordingly.
  Figure 3: Picture has been added (Figure 3D) and cartoon (Fig. 3A) to display the true geometry of the silicone putty layer.
  Figure 5: Magnified scale bar has been added.
  Figure 6: Information has been added for each frame to emphasize key structural elements and configuration/deformation stage. Magnified scale bar has been added.
  Figure 7: Y-shears and scale (previously given I caption) have been emphasized.
  Table 1: Table has been added more clearly to identify and explain positive structural element types (PSEs). References to figures that illustrate the different PSE-types have been added.
  Figure captions have been revised in harmony with revisions of figures.
  
  Citation: https://doi.org/10.5194/egusphere-2023-10-AC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

AR by Roy H. Gabrielsen on behalf of the Authors (27 Mar 2023) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (31 Mar 2023) by Michael Rudolf

RR by Anonymous Referee #1 (01 May 2023)

RR by Anonymous Referee #2 (05 May 2023)

Suggestions for revision or reasons for rejection

I have spent a long time to carefully evaluate this manuscript. The text really bothers me with mixed feelings. Based on my reading, results are reliable and interesting, and this manuscript has been improved from the previous version, but it is still not enough to be published. Therefore, I have to give them another major revision to fix all the problems existing in the current version.

Firstly, I have never seen such a simple response letter before. I do not know which comments are answered and which are not, and how to locate the revision in the text. A point-to-point response letter is an essential part for reviewers to assess whether the revision is appropriate. The revised manuscript should include one response letter with all comments and replies, and the line numbers for each revision in replies to locate the change.

Second, as I suggested in my last review, the text is too lengthy, while some parts repeat the structures generated by experiments with over hundreds of lines. I strongly recommend reducing the result and discussion sections. The first section of results has more than 200 lines to depict the structures during the strike-slip period, while the latter two stages, extension and contraction, are described in a more concise way. In fact, the latter two stages have two different settings with orthogonal and oblique stress to the shear margin which needs separate description and discussion. However, only oblique extension is chosen and the reason for such choice remains unclear.

Third, the motivation of the manuscript is not clear. I understand that the experiment has perfectly replicated the formation of the Barents Shear Margin, including the restraining and releasing bends and basin-thrust-normal fault complexes, but clarifying the purpose or implications of this analog modeling will be much helpful to highlight the importance of the result. This problem also exists in the discussion. In the discussion, details of developed structures reappears and the sentences are somewhat repeated. I checked the first several paragraphs and then went through this part quickly. In this section, I can only recommend discussing the modeling with tectonic evolution, and removing some sentences on the structures that have already been described.

Fourth, I cannot get the point on dividing 6 types of structures from PSE-1 to PSE-6. It is really difficult for readers to remember the structures classified in those types. I have to return to previous sections to find the definition for PSE.

Fifth, the description of modeling results often lacks corresponding figure numbers, thus confusing me so much. In lines 549-554, I need figure number for these structures. Besides, structures are sometimes missing in figures. I cannot find structures in lines 509-510 in any figure, and corresponding structures (fold or fault) in figure 8.

Lastly, there are a lot of references in result section. I am baffling on them, e.g. in lines 568-573. Has the work been already presented in the papers? If they are only interpreting the faults with similar mechanisms, move them to the discussion part. Similar problems exist here and elsewhere, please revise them altogether.

Each problem I listed above is not alone (in one place), but appear over and over again. I made a lot of suggestion on the pdf and uploaded it as supplementary files. Please check this file and make necessary changes.

Referee Report: PDF

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ED: Reconsider after major revisions (08 May 2023) by Michael Rudolf

AR by Roy H. Gabrielsen on behalf of the Authors (28 May 2023) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (12 Jun 2023) by Michael Rudolf

RR by Anonymous Referee #1 (10 Jul 2023)

ED: Publish subject to minor revisions (review by editor) (11 Jul 2023) by Michael Rudolf

AR by Roy H. Gabrielsen on behalf of the Authors (15 Jul 2023) Author's response Author's tracked changes Manuscript

ED: Publish subject to technical corrections (18 Jul 2023) by Michael Rudolf

ED: Publish subject to minor revisions (review by editor) (20 Jul 2023) by Federico Rossetti (Executive editor)

AR by Roy H. Gabrielsen on behalf of the Authors (23 Jul 2023) Author's response Author's tracked changes Manuscript

ED: Publish as is (25 Jul 2023) by Federico Rossetti

ED: Publish as is (25 Jul 2023) by Federico Rossetti (Executive editor)

AR by Roy H. Gabrielsen on behalf of the Authors (29 Jul 2023)

Journal article(s) based on this preprint

31 Aug 2023

Analogue experiments on releasing and restraining bends and their application to the study of the Barents Shear Margin

Roy Helge Gabrielsen, Panagiotis Athanasios Giannenas, Dimitrios Sokoutis, Ernst Willingshofer, Muhammad Hassaan, and Jan Inge Faleide

Solid Earth, 14, 961–983, https://doi.org/10.5194/se-14-961-2023,https://doi.org/10.5194/se-14-961-2023, 2023

Short summary

Roy Helge Gabrielsen, Panagiotis Athanasios Giennenas, Dimitrios Sokoutis, Ernst Willingshofer, Muhammad Hassaan, and Jan Inge Faleide

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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

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Short summary

The Barents Shear Margin defines the border between the relatively shallow Barents Sea that is situated on a continental plate, and the deep ocean. This margin evolution history was probably influenced by plate tectonic reorganizations. From scaled experiments, we deducted several types of structures (faults, folds and sedimentary basins) that helps us to improve the understanding of the history of the opening of the North Atlantic.


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