Early Evolution of the Adelaide Superbasin

Round 1

Reviewer 1 Report

A few comments and corrections for the authors to consider:

Line 153: Materials and Methods: More details of sample location? While grid references are provided in the supplemental data, it would be good to have more details of where the samples are from in the actual paper as well as a reference back to Fig 2.

Line 159: some missing text

Line 213: You could comment here that apart from the 892 ± 13 Ma youngest date, there are a couple of other zircons within error of this age - see my later comments.

Line 264-268: A lot is being made of one zircon, which is always risky because it could be from lab contamination or suffering from some undetected alteration affecting the age. What is significant in this case is that there is a small group of several zircons of around 900 Ma, including this one, with dates within error. This makes the result seem more robust, and a justification for focusing on the youngest as a maximum depositional age. I’d like to see a bit more emphasis on this small group, i.e. are they all euhedral or do they have other physical or chemical characteristics in common?  These other young zircons are mentioned a bit later, but I think they need to be mentioned here to give strength to the maximum depositional age.

Line 274: Comment: The date of 893 ± 9 Ma is within error of the date of 896 ± 24 Ma (Kositcin et al 2015: NTGS Record 2015/001) for the youngest zircon from a sample near the base of the Gillen Formation in the Amadeus Basin. While this sample is not from right at the base of the Amadeus Basin succession, the unit could still be an Arkaroola Sub-group correlate.

Line 285: move second comma

Line 290-296: While these young zircons could have a local source, as you suggest, I will comment that detrital zircons of 1000-800 Ma are not uncommon in WA parts of the Centralian Superbasin – occasionally even the dominant age population, e.g. GSWA samples 181871 & 181872 from an upper Tonian unit in the Officer Basin (refs below are just FYI can be obtained online). While the source of these zircons remains enigmatic their abundance in detrital populations to the west could point to a source of such aged zircons in that direction. However, zircons of this age also reappear in the upper Tonian of the Adelaide Rift Complex, so by then they are being spread far and wide.

WINGATE, M. T. D., and BODORKOS, S., 2007, 181871: quartz sandstone, Lancer 1; Geochronology dataset 683: Western Australia Geological Survey. WINGATE, M. T. D., and BODORKOS, S., 2007, 181872: quartz sandstone, Lancer 1; Geochronology dataset 684: Western Australia Geological Survey.

Line 336: zircons

Line 365: This lends …

Line 459-462: Is this statement back to front?

Line 486-489: Quite agree! So much has been based on the Rook Tuff date for which no details, including accurate location have been published.

Line 497: ‘following’ rather than ‘during’ ?

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Dear editor

I have reviewed the manuscript in “title Early Evolution of the Adelaide Superbasin” authors Lloyd et al. Authors interpretation about propagating continental rifts and triple junction rift in the Adelaide area is clear and I think it would be interesting to understand the late Neoproterozoic crustal evolution and also the development of the extensional basin in that time. I have some comments below and based on that I suggest some more revisions.

1. In the introduction, the authors need to add more information about the crustal evolution in the Neoproterozoic with some paleogeographic maps. In addition, need to talk more about some recent classical triple junction and their rifts arms.
2.    The authors have focused on a few areas. It is not clear that areas are related to single or multi rifts. In this case, I recommend the authors make a clear stratigraphic correlation among these areas.
3.  Most sequences of geology units in Figure 3 are sedimentary rocks that have probably precipitated in a shallow basin. These sequences can be generated in most of the sedimentary basins and they are not indicators for the general and or propagating rifts. sinsediments structures and bimodal magmatism need to be outstanding in this work.
4. The schematic model is necessary and it should be added to show which arm of the triple junction was aulacogen and what is the rocks of the same age in the rest arms.
5. Abstract need some more information on your model and finding unclear in the abstract, please highlight your findings
6. Log-log diagram which was used in figure 8 it is ok, So, please delete the log and the mas number for Yb and Y.

Best wishes

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

data from three samples of sediments to investigate their provenance as well as the earliest tectonic evolution of the Adelaide Superbasin in Australia, a large and well preserved rift system associated with the Neoproterozoic breakup of Rodinia. This is a good paper, which brings high-quality analytical data and uses these data to constrain the evolution of the basin. The paper is well written and relatively easy to follow. I have only a few comments;

1.The manuscript contains an excessive amount of unnecessary references. They should be reduced to about 70 without any detriment.

2. Figure 5 although is correct would be confusing for readers,
3. The same is for Figure7. It is not reader friendly.
4. The spelling of “Slama” versus “Sláma” should be the same throughout the paper. References e.g., 60, 64, line 168.
5. Line 159 should read “ the provenance of earliest sedimentary rocks”

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The manuscript is now much improved and it is ready to publish in the Geosciences at present form.

Best wishes