Ground-Penetrating Radar Study of Progradational Units in Holocene Coastal Plains: Carchuna Beach (SE Spain)

Round 1

Reviewer 1 Report

Review Geosciences 842053

This is an interesting but fairly localized case study that provides a good example of the utility of GPR in coastal settings. The authors use GPR profiles from 250 MHz shielded antenna provide that give a good penetration depth and resolution balance. The GPR images successfully differentiate a sequence of sedimentary bodies including planar low-angle cross-bedding and both foreset and topset reactivation surfaces.

The authors correctly note that the sedimentary structures are typical  of prograding beach face deposits in a regressive context. A perpendicular profile identifies parallel laminations dipping towards the sea and a water table level is identified.

The authors use the GPR to identify the presence of saltwater in sediments by attenuation showing that GPR detects both water tables and saltwater intrusions in shallow aquifers as well as strong erosional processes correlated to an event 2,400 years BP.

The whole sequence in the coastal plain is then attributed to small regressive periods resulting from small sea-level falls that the authors loosely correlate with the periods of increased aridity in SE Spain.

The authors also describe several erosional surfaces that they speculate may be associated with increases in storm intensity combined with small sea level rises.

The paper is OK in its current form but the arguments and links to past storms and climate need to be expanded and supported with more literature.

To be improved before publication I believe the paper needs the following

1. The introduction needs an expanded paragraph of international context. See recent paper by Gouramanis et al., in Geomorphology for an open access example of a better review and contextual set up. https://www.sciencedirect.com/science/article/pii/S0169555X20302452
2. Since your figures are all in colour why not make a colour panel of the interpretation at the bottom of each GPR figure. See the paper above as an example.
3. The links to past aridity and storminess needs to be expanded and improved. At this stage they seem very speculative. If they are speculative it needs to be stated as such.
4. A key study on overwash and erosion is missing from the discussion. Please read and refer to this highly cited paper. https://www.sciencedirect.com/science/article/abs/pii/S0037073805003155

Author Response

First, allow us to express our heartfelt thanks for all suggestions. We have prepared a new revised version of the paper considering all comments. The modifications are highlighted with red colour: eliminated sentences/paragraphs are crossed out in red and added words/sentences are written in red Font. Please find below our answers to the comments and requests and a description of the modifications made to the paper.

1.- A new paragraph has been included in the introduction to highlight the international context. A new reference has been included

2.-The links to past aridity and storminess have been expanded and improved.

3.- We have been included in the discussion a key study on overwash and erosion. A new reference has been included

Reviewer 2 Report

Ground penetrating radar study of progradational units in Holocene coastal plains: Carchuna Beach (SE Spain)

By: Javier Rey, Julián Martínez, M^a Carmen Hidalgo, Rosendo Mendoza, M^a José Campos.

Submitted for publication on GEOSCIENCES

This paper needs a revision taking into consideration the following comments:

1. As Geophysicist, I am concentrating in my review here only on the geophysical (GPR) parts of this paper, i.e., I have not reviewed the coastal geology and sedimentation parts.
2. A specialist should edit the English.
3. The novel idea of characterizing saltwater and freshwater by GPR data needs more justifications from data interpretation
4. A specific proof based on quantitative data interpretation is missing, e.g., by analysing reflections (coefficients) at saltwater and seawater contacts, respectively, and comparing them with each other (see e.g., al Hagrey, Müller 2000, Geophysical Prospecting 48, 63-85)
5. Is this goal of mapping coastal deposits and their internal structure original? If yes explain why.
6. Line 87: “… an indirect research methods” what do you mean?, Better, delete it,.
7. Line 142: “… the pelitic matrix, which enhances electromagnetic wave transmission”, better change to “… the pelitic matrix, which allows electromagnetic wave transmission with low attenuation.”
8. Line 212-213: “… considerable attenuation and disturbance that could be associated with an increase in the pelitic fraction ….“. This needs more explanations since it is in conflict with the result of p. 4 “pelitic matrix show low attenuation”.
9. Line 242-243: “Thus, the GPR is also a good tool to detect both water tables and saltwater intrusions in shallow aquifers”. This conclusion needs justifications of quantitative data interpretation and discussion with published work (see comments before).

Line 326-327, Reference [23], is not a reference but a program manual; you may cite it in the text only

Author Response

First, allow us to express our heartfelt thanks for all suggestions. We have prepared a new revised version of the paper considering all comments. The modifications are highlighted with red colour: eliminated sentences/paragraphs are crossed out in red and added words/sentences are written in red Font. Please find below our answers to the comments and requests and a description of the modifications made to the paper.

1. The English has been reviewed by a native speaker.
2. More detail has been included on the justification and usefulness of the GPR to detect the contact of fresh and salt water. New reference has been included.
3. The text has been modified to avoid the contradiction between pelitic fraction and signal attenuation.
4. The program manual has been eliminated to the References