Authigenic Gypsum Precipitation in the ARAON Mounds, East Siberian Sea
Round 1
Reviewer 1 Report
I've read this parer with pleasure.
I've appreciated the clear presentation of the data and the description of the methods used for analyses.
I just would like to suggest to say something about the organic content of these sediments; their different colors could maybe indicate different organic content. Your lithological description is adeguate but in such geological setting some indications on TOC could be appropriate. You also write about bioturbation signs (line 223).
Talking about MDAC I would suggest to perform some Stable Isotope analyses (C and O) on these carbonates to verify if they are detrital or authigenic.
I appreciate the schematic organization of the conclusion of the paper.
Just one modification in lines 43-46: I prefer to use , instead of ; between the different phenomena reported in marginal Arctic Seas:
Methane-related phenomena such as bottom-simulating reflections, gas seepage, high concentrations of methane in sediments, seawater and at the sea surface, presence of gas hydrates or methane-derived authigenic carbonates (MDAC) have been reported in marginal Arctic seas.
I hope you will appreciate my suggestions.
Author Response
We would like to thank for constructive reports with helpful comments and suggestions. Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 2 Report
Authigenic gypsum has been commonly discovered in marine methane-rich environments. Previous studies have suggested that gypsum formation in seepage environments is generally located near the sulfate-methane transition zone (SMTZ). In this manuscript, the authors investigated the mineral compositions of gravity cores from the Arctic methane hydrate zone. They have firstly observed authigenic gypsum in the Arctic Ocean methane seepage systems and proposed that gypsum precipitation can be a suitable proxy for identifying methane hydrate zone in study area. Although I think it will be a useful reference for future studies in this area and publishable on Minerals, several comments need to be addressed before publication.
Q1: Since pyrite is absent in studied cores, how to determine whether the sulfate sources for gypsum precipitation is associated with the oxidation of sulfide? I would like to suggest the authors to consider the contents and sulfur isotopic compositions of chromium reducible sulfur (CRS) in bulk samples.
Q2: It is suggested the accumulation of H2S in pore water can lead to widespread carbonate dissolution, providing primary Ca sources for gypsum formation. However, more detailed evidence should be presented to clarify the patterns of such carbonate corrosion (Figure 6).
Q3: The authors proposed that precipitation of gypsum is closely associated with the absence of dolomite. However, gypsum and dolomite are both present at ~240 cm in AM 01 (Figure 3). How to explain these patterns?
Author Response
We would like to thank for constructive reports with helpful comments and suggestions. Please see the attachment.
Author Response File: Author Response.pdf