(U-Th)/He Dating of Supergene Iron (Oxyhydr-)Oxides of the Nefza-Sejnane District (Tunisia): New Insights into Mineralization and Mammalian Biostratigraphy

Round 1

Reviewer 1 Report

The reviewed paper is an outcome from multidisciplinary, but mineralogy-anchored project. It is very informative and well-written. The authors present their findings correctly and put them into a broader context demonstrating their various applications. I think the paper is perfect and needs only small improvements.

• You establish two weathering events and try to explain them. Well done. But how this new evidence is related to what is known about the Tortonian and Pleistocene evolution of the Mediterranean basin? Please, check the works by Prof. Wout Krijgsman and his group.
• A section/sub-section cannot consist of one paragraph.
• Figure 5: I suggest to make small modification to indicate that the Rupelian exists between the Priabonian and the Chattian; TRIAS -> TRIASSIC.
• As this paper discusses biostratigraphy, it must bear any figure (even very simple) showing the biostratigraphical framework and may be the discussed taxa ranges/occurrences.
• Line 429: please, avoid writing about the Pontian, if even this label was used in the original source you refer to. The Pontian is a regional stage of the Paratethys, where it can be understood differently between the Central and Easthern Paratethys.
• Do the fossil taxa you report prove your climate interpretations?
• Text polishing is necessary for two purposes: 1) slight English correction, 2) making your phrasing less wordy and more exact.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Yans et al. is an interesting paper utilizing a novel geochronometer to date the timing of supergene mineralization. The data are robust, and the interpretation is logical. I cannot comment on the paleontological aspects of this paper (last two pages) as it is far outside my expertise, but I do find this discussion a bit of a diversion from the overall narrative. If that material was left out, it would not be detrimental to the overall paper. Below I have given comments on the figures, table, and text of the manuscript, which should help clarify the authors’ message.

One general criticism is the lack of detailed sample description, from outcrop scale to thin section scale. Section 3 does contain some very basic information but lacks anything substantive. How thick were these horizons? How laterally extensive were the horizons? What rock was above/below the sampled horizons? What other distinguishing characteristics were notable about these samples? The methods state the mineralogy was determined via X-ray analyses; where are those data? I understand that this is a pretty straightforward story, but - as an experiment - could another group retrace your footsteps, and get the same results? Have you provided enough qualitative data and observations?  A few field photos would be useful. I do not think any of these details will change the interpretations, but they certainly would strengthen the conclusions.

Fig 1: needs map scale

Fig 2: why is 14MnTAM age box above the figure and white, not black? G-CS is not labelled, only CS.

Fig 3: FK is not appropriate mineral abbreviation. Need to spell out abbreviations used in figure.

Fig 4: what is the difference between black and brown circles and histogram boxes? Why is only hematite-goethite mixture labeled? Can the individual samples be highlighted?

Fig 5: Red font is not legible. What are the other dates listed in the figure? What was dated? What method used? Source of data? What is “Numidian”?

 

Table 1: Please report data with decimal point, not commas. Location needs to include UTM or Lat/Long position. Superscript “4” in 4He. Raw age error (15th column) is 1 sigma? 2 sigma? Please clarify last two columns in the text of the manuscript: the authors added 10%? It is very confusing: the data was corrected for a 10% loss because of alpha ejection, but then 10% was added back on? 

 

Line: comment

L25: Why Tunisia? An audience would be more interested to read about “the first time in southern Mediterranean” or “first time in <insert geological domain>”

L41: SEDEX, not Sedex

L47: geothermal, not geothermic

L51: In addition, not Besides

L52: delete “located”

L59: what do the authors mean “refined ages”?

L63: Again, why Tunisia?

L66: “to discuss” not discussing

L68: delete comma

L71: what do you mean “confront”?

L78: caption - I am not sure the use of the “corrected” is needed

L87, L95: age and error should have similar significant digits (6.4 ± 0.2 Ma). Fix every where.

L94: “A K-Fe alteration event…”

L99: SEDEX, not Sedex

L119: evince, not evidenced

L120: “at c. 0 Ma” not around c. 0…

L133: “their samples” not his samples

L139: consist of, not consist on

L142: I am not sure who is being referred to with “by the latter authors.”

L155-156: need to spell out abbreviations used in figure

L157: “of the samples” not of samples

L186: spell out LSCE

L196: what do the authors mean “homogenous eU”? Values of 0.5 to 7 ppm vary by an order of magnitude. How is this homogenous?

L198: what do the authors mean “similar Th/U ratios”? Values of 0.01-0.2 vary by an order of magnitude. How is this similar?

L206: us the “~” not circa.

L216-219: Please clarify preferences and message about errors.

L220: By ‘earliest episode” do the authors mean ‘latest episode’?

L221: use “ca.” not ~

L232: Why Tunisia? 

L234: what is contamining?

L240-242: Pedantic statement. Good sample description and methods are always required.

L293: ‘cropping out’ is not a word. Are exposed?

L295: significant figures on date

L295: What is the purpose of stating the reliability of the ages?

L315: minimum, not minimal

L318: metals were sourced from sedimentary rocks?

L393: and, not et

L394: Late, not late

L416: required, not requested

L417: pick two: nature/scale/role, and separate them with "and"

L419: section 5.5:  throughout this section, & is used instead of “and.” Change everywhere. I found 10 examples of this.

L424: ‘cropping out’ is not a word. 

L435: SEDEX, not Sedex

L448: what do the authors mean ‘concerned’?

L460: is “two-horned rhinocerotine rhinocerotid” correct?

L512: new ages not only on goethite, correct?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf