Dear Lena and co-authors,

You revised your manuscript following most of the criticism expressed by the two reviewers but there are still some important points (the reliability and precision of the biostratigraphic data, the continuity and the completeness of the studied sections, the integration with magnetostratigraphic data, etc.,) that need to be thoroughly discussed before a definitive acceptance of the paper. These points, which are essentials if you want to establish a sound correlation of the Jurassic/Cretaceous boundary, are well highlighted by the third reviewer and I thus I ask you to carefully take into consideration and to adjust the manuscript according to his comments.

You might also want to consider my personal remarks which are reported below:

Abbreviations such as J/K JKB etc… Please, as far as it is possible, be extremely careful and follow the recommandations of the ICS for standard, common terminology. If you create a new abbreviation make it clearly understandable (and not conflicting) since the beginning of the manuscript.

FAD’s and LAD’s and their use for dating and correlating. I personally recommend to use FAD and LAD when it is sure that we are closest to the very first, evolutive appearance /disappearance of a taxon or species (FAD’s and LAD’s age can be extrapolated). In a more specific contest such as in Mazatepec section it is preferable to use FO (first occurrence) or LO (last occurrence) because these bio-horizons are highly affected by taphonomic processes (preservation, facies change and unfavourable lithologies…), sample density, and also different analytical methods which can alter their « true » apparition/disparition level. You should consider a larger confidence interval for the bio-horizons, especially when they result from a poor data set.

Calcareous nannofossil biostratigraphy. The calcareous nanofossil data set of Mazatepec is, unfortunately, very poor so I’would’t « force » such poor data to fit in a stratigraphic framework. The Umbria granulosa specimen reported in figure 3 (fig 3-K) which should illustrate calcareous nannofossils from the Mazatepec section in Mexico, is exactly the same specimen reported by Vennari et al (2014) from Las Loicas section in Argentina ! Surprisingly, Umbria granulosa is not reported in the range chart of Mazatepec (supplementary material)… I hope that this unfortunate « copy and paste » is just accidental… Also, from the illustration the diagnosis of this species is wrong. Please, fix this issues.

Once these modifications are made the paper will surely have a better impact and deserve publication.

I remain available for any further clarification and help you might need

Your sincerely

Silvia Gardin

Dear authors,
I am happy to announce that your manuscript is accepted for publication. Thank you for having carefully revised your manuscript, the changes you have made have significantly improved the scientific impact of your manuscript.

Dear Authors,

based on the TE's report and overall assessment of the review process, I am pleased to accept your revised manuscript for publication in Solid Earth.

Many thanks for choosing Solid Earth.

Sincerely,
Federico Rossetti