| 23 Jan 2026
Climate changes in Anatolia across the late Eocene and the Eocene-Oligocene Transition: successive warming and cooling, aridification, and implications for the westward dispersal of Asian terrestrial mammals
Abstract. The Eocene–Oligocene Transition (EOT dated at ~34 Ma) represents one of the most significant climatic shifts of the Cenozoic, marking the transition from the last warmhouse state to a coolhouse state. This global cooling had major consequences for terrestrial ecosystems and was synchronous with the dispersal of numerous Asian mammalian clades towards western Europe. However, the terrestrial expression of the EOT exhibits strong regional heterogeneity. Consequently, its role in establishing dispersal corridors associated with the Grande Coupure remains unclear.
Here, we describe, date, and document the paleoenvironments of a continental sedimentary section from Balkanatolia, a biogeographic province that most likely functioned as a critical stepping stone for the dispersal of Asian mammals toward western Europe. Our sedimentary record represents a fluvio-lacustrine system dated by magnetostratigraphy to the Priabonian and the lower Rupelian, including the Oi-1 glaciation (~33.65 Ma). Clumped isotopic analyses on pedogenic carbonates across our record show evidence for a Late Eocene Warming starting during the middle Priabonian (ca. 37 Ma), followed by a marked cooling event at the Eocene–Oligocene Glacial Maximum (EOGM). Stable isotopic data and sedimentary facies further indicate that this complete interval is associated with a long-term aridification trend, starting during the Late Eocene warming and culminating at the EOT. Our results provide the first quantitative record of late Eocene warming on land, and our temperature estimates for the earliest Oligocene cooling are consistent with other Eurasian clumped-isotope records. These temperature shifts and associated aridification steps may have acted as contributing drivers of the late Eocene decline of Balkanatolian endemic taxa and likely facilitated the westward expansion of Asia-derived mammals ultimately resulting in the colonization of western Europe.
Review of Botté et al.
Climate changes in Anatolia across the late Eocene and the Eocene-Oligocene Transition: successive warming and cooling, aridification, and implications for the westward dispersal of Asian terrestrial mammals
Submitted to EGU Climate of the Past
In the manuscript submitted by Botté et al., sedimentological observations are combined with stable isotope (δ13C, δ18O, Δ47), paleomagnetic, and x-ray diffraction results from an Anatolian basin with Eocene-Oligocene terrestrial deposits. They interpret the data in terms of paleoenvironment and paleoclimate with important implications for the understanding of climate dynamics around the Eocene-Oligocene transition (EOT), as well as large mammal dispersal between Asia and Europe.
The manuscript is well-written and the figures generally support the text and findings in an efficient way. The results are of great importance for our understanding of continental climate dynamics around the EOT and the potential relationships between climate and faunal migration between Europe and Asia. Besides a number of comments and suggestions that should be relatively easy to take care of (see line-by-line comments), I have three major concerns. However, I do believe the authors should be able to address and resolve them.
Major concerns:
1) Pedogenic carbonate samples misplaced with respect to hiatus:
As I had trouble seeing the individual clumped temperatures and the relationship of the data with hiatus 1 (Fig. 6), I plotted them from the supplementary data. When doing so, I figured that the clumped T’s are misplaced with respect to hiatus 1 (level 263 m), as it should be located between the two stratigraphically lowest clumped samples (18CIC09 at level 253 m and BTCARB5 at level 265 m) and not between clumped samples 5 & 6 (in stratigraphic order; see Fig. 8). Alternatively, there is a mistake in the level of hiatus 1 in the manuscript (263 m) or the stratigraphic levels of the reported clumped samples (see suppl tables 3 & 4). Please clarify this. I do not believe that it has major implications for the interpretation of the clumped data and one could still argue for a similar paleoclimatic interpretation, although the discussion would need to be adjusted. For instance, it would imply that the warming trajectory is captured between the two hiatuses. Also, the origin of hiatus 1 would require a different interpretation if it comes before the Late Eocene warming (see e.g., lines 558-559 and lines 576-577).
2) Data availability:
The demagnetization data and XRD patterns should be made available. Add the following information for each demagnetized sample: sample, sample volume, the X-Y-Z components and intensity for each demag step, sample orientation, bedding orientation. I would strongly suggest the authors upload the paleomagnetic data to an online database (e.g., MagIC), as should be common practice nowadays.
3) Paleomagnetic data and magnetostratigraphy:
-The files do not include stereographic projections with ChRM directions in geographic coordinates (or bedding planes for each sample that would allow to produce them). How do they relate to the present-day field at the location? The absence of the data and plots does not allow the reader to assess whether the samples may have undergone remagnetization, as the presence of normal and reverse polarities alone is not a guarantee for a primary origin of the ChRM. Please address this in the manuscript.
-The paleomagnetic methods should include details on the criteria that were used to deem samples (un)reliable and exclude or include them in the magnetostratigraphy. From the supplement, I can deduct some information about the confidence levels of the data set by the authors, but this is very qualitative. The authors will have to make sure to use more quantitative criteria, as is common in paleomagnetic studies, e.g.: 1) how many demag steps were use as a minimum for the calculation of the ChRM for each sample?, 2) what is the maximum allowed MAD? 3) how was the ‘uncertain polarity’ cutoff in Fig. 4 determined and how were samples excluded based on this?
-Reversal R2 seems to consist of three consecutive samples in Fig. 4. However, there are only two samples with reverse polarity in the supplementary table. Where does the third sample come from? And why are there four samples marked as reverse in the supplement for R2, whereas there are really only two reverse samples? Where do the inconsistencies come from? I think this partially has to do with the combination of the data in this manuscript with those from Licht et al., (2022), but it’s difficult to assess, because the Licht et al. data are not included in the supplementary table and not discernable from the newly presented data in Fig. 4. Make sure to add them to the supplement (which will make it easier for other scientists to build on these data) and give the Licht et al. data a different color/symbol in Fig. 4.
-The preferred correlation of N4 with the GPTS does not allow for the well-dated marine fossil assemblage (ca. 50 m in strat column) to be Priabonian in age (see how level 150 m is loosely correlated to the bottom of the Priabonian). Based on the dated tuffs it is solid to correlate R1 with C12r, but for the entire section below that it is difficult to provide reliable correlations, because of the very limited number of reverse samples, the sampling resolution, and (un)identified hiatuses (let alone changing sedimentation rates). I’d suggest to correlate the marine beds to the bottom of the Priabonian and then calculate a minimum sedimentation rate for the interval between the marine beds and R1 (minimum, because one can’t know how to correlate the marine beds to the Priabonian). Indeed, as the current preferred correlation suggests, hiatus 2 is likely coinciding with chron C13r. I think the authors can then reasonably build a case for the age of the high Δ47 T’s interval to be latest Eocene, i.e. older than the start of the EOT (as is the case in the current preferred correlation). It may not change that much to the discussion of the temperatures, but it makes the discussion a bit fairer.
Line-by-line comments:
Title: please try to shorten. E.g.: the part after the colon already implies that the manuscript presents paleoenvironmnetal/paleoclimatic reconstructions, so the start of the title is somewhat redundant.
Abstract (and maybe title?): indicate that Anatolia forms part of Türkiye. Same for the location of Balkananatolia in the Abstract (e.g. NE Mediterranean region?).
23: Grande Coupure needs half a sentence of introduction in the abstract.
53: Something seems missing here. Do you mean stable isotope records from carbonates? Or clumped records from carbonates?
58: Please detail ‘other’?
75: I doubt that Eronen et al. mention this correlation or constrain surface uplift of the Alps. Rather, they write: ‘…and contrasts with contemporaneous faunal response in Eurasia where tectonics and associated surface uplift played only a subordinate role.’ Importantly, Kocsis et al. interpret a decrease in δ18OPO4values of herbivore tooth enamel after 31 Ma to result from surface uplift of the Alps. However, the youngest deposits for which clumped data are provided are from ca. 33.5 Ma soil carbonates.
Please rewrite accordingly, which also implies rewriting the last sentence of the discussion.
85: Please add a some of information about the impact of orbital configurations and pCO2 changes on the dispersal routes. It would really help the reader.
86-88: Add e.g. the word ‘Collectively’ to the start of the sentence, so the reader is guided to what research is carried out in this study.
89-90: add the sedimentological observations/facies analysis to the methods used. You did a lot of good work there!
101: E.g. Tisza and the Pontides have basements of Gondwana affinity. Fix and check for the other terranes.
106: add spaces to ‘Asiaby theParatethys’
107: There are two Montheil et al., (2025) publications in the ref list. Make sure to add a and b.
115-116: Luda Kamchiya Through and Moesian Platform need to be included on the map in Fig. 2.
120: ‘anthracotheriidae, gelocidae and amphicyonidae’. For most readers, it would be nice to include that these are artiodactyla and carnivores.
128-131: There is no contradiction between the Lefebvre and Van Hinsbergen studies. Also Lefebvre et al. regard the Kirsehir Massif as a metamorphosed northern tip of the Taurides. So please remove the controversy.
135-137: see my previous comment. Remove the controversy.
137: is Licht et al., (2017) the reference that was intended to be placed here?
148: ‘(reference here)’ indeed needs a reference.
150: Only lacustrine or also fluvial?
157: ‘Brontotheriidae and Hyracodontidae’ please add that these are Perissodactyla. That increases readability for non-specialists.
163: Balakananatolia --> Balkananatolia
184: Please point out what new work was conducted in this study while building on the work of Licht et al. (2022). This seems to be explained in line 186, but it is not very clear, so please rewrite.
185: there are two Licht et al., (2022) publications in the reference list. Please add a and b.
200-214: indicate more clearly how the new samples relate to those of Licht et al. and that the data in this manuscript are combined with theirs in the results/discussion.
200-214: make sure to include methods and references to the statistical methods that were used to carry out the reversal test, to calculate confidence ellipses (see Fig. S5) and methods to exclude outliers in case those were used. I can also not find information about how the ‘uncertain polarity’ in Fig. 4 was defined and if this led to the exclusion of samples. This will need to be transparent.
200: convert inches to cm as per journal policy (SI units).
201: retrived-->retrieved
202: given the available XRD data and thin sections, can something be said about the mineralogy of the clasts?
203: remove comma
204: Natural Remanent magnetization and--> Natural remanent magnetization (NRM) and
209: using alternating field (AF) demagnetization--> using AF demagnetization
210: demagnetization. Among these, 14 --> demagnetization, of which 14
210: orthogonal diagrams--> orthogonal vector diagrams
211: projection--> projections
213: lacked a coherent directional trend, likely--> lacking a coherent directional trend, which is likely
214: how many were excluded and on the basis of what criteria? See major comment #3 above.
217: isotopic--> isotope
221: ove--> oven
221: *--> °
223: isotopes--> isotope
224: spell out V-PDB
224: frame-->materials
225: what were the criteria for selecting these particular samples?
230: stale--> stable
232: faraday--> Faraday
242: there is a statistically significant difference between the pretreated and non-treated samples for some samples (see suppl table), so this statement is incorrect. However, there is no systematic offset, is that what the authors intended to write? Please adjust.
260: 4.1 Sedimentology of the Büyükteflek section. Please include XRD in the title (and make the patterns available, see major comment 2)).
320-322: if these are NRM intensities, please name them as such.
323: up to what field strength/T’s is this viscous component typically visible?
322-326: include this type of information also for the AF demagnetized samples
326-327: this is methods, not results. Please move. But: why 120-500°C? According to what I read in the methods, the highest T was 660°C? Please clarify.
328-330: in the absence of rock magnetic measurements, the unblocking T ranges indicate the presence of mt and ht in the samples. So why the ‘sometimes’ after the comma? Please adjust the sentence.
329: can a reference be made to an example in the data?
332: remove ‘primary’ from the sentence. The argumentation as to why these directions are primary comes later.
336-337: this is methods, please move it there and include references to the statistical methods that were used.
337: add the visual and statistical results of the reversal test to the supplement and include the statistical results here (critical angle, classification etc).
344: what is considered ‘reliable’? See also major comment 3)
346: a) the lower part was not sampled at a lower resolution (as far as I can see), so this confuses me? b) are there any reasons to assume that diagenesis is more of an issue in the lower part of the section?
355-357: for the averages in these lines: add standard deviations
367: add the sample number of the one that contains dolomite.
371: remove ‘with it’
377: δ18Owater values--> δ18O values of soil water (δ18Owater)
Section 5.1 in general: see major comment 3)
392: the fact that the magnetostratigraphy of Licht et al., (2022) was correlated to the GPTS through biostratigraphy and U-Pb dating needs to be reflected in this sentence, as this is crucial information.
393-395: move this information downward. It’s always better to start with what one knows rather than what one doesn’t know.
395: refer to the Paleogene time scale chapter of Speijer et al., (2020) within the book, rather than the entire book.
439: add ‘tectonic’ in from of ‘uplift’
471: can the dolomite and its potential origin from evaporation be related to the thin sections?
498: soil carbonates only form in seasonally dry climates, so ‘alternating wet and dry climates’ can be removed in my opinion. Instead, point out why in sub-humid climates the T’s rather reflect MAT. Or did the authors mean that there are multiple annual wet and dry cycles?
502: I think it could be useful to add the numerical age for the Lutetian stage.
Sections 5.4 & 5.5: need to be rewritten once the relationship of the pedogenic carbonates to hiatus 1 is sorted.
720: year of publication missing.
Figure 2:
(B): what are these reconstructions based on?
(C): I believe this map was first published by Gülyüz et al., (2013) and based on a geological map of Ketin (1955). Please refer to it accordingly in the caption. ‘Younger Units’ are named ‘cover series’ in line 143. Use one of them throughout.
Figure 4:
- ‘VGP’ and ‘Outliers’ are indistinguishable, please give them different symbols and/or colors. Also make sure the data from Licht et al., (2022) are discernable from those presented in this manuscript.
-Given the statement in l. 343-344, the upper normal polarity interval should be colored grey.
-add the levels of the pedogenic carbonate samples with clumped data to the log (also in Fig. 7)
Figure 5:
-These diagrams are not Zijderveld diagrams, but orthogonal vector diagrams. Replacing them with Zijderveld diagrams would be great, as the link between dec and inc for each demag step is better visualized.
-Add several demag steps to the diagrams, so one can see what the first and last steps, as well as some intermediate ones, represent.
Figure 6:
-the numerical stratigraphic levels are irregularly placed
-the last column with the clumped T’s needs more space, as it is tough to discern the different points. See also major comment 1).
-in the caption, indicate whether the plot includes 1s or 2s analytical uncertainties.
Figure 7:
-Add the EOGM to the figure, as well as the pedogenic carbonate levels with clumped data.
-See also major comment 3).
-Add the interval of the Grande Coupure, so the reader can more easily relate to it.
Figure 8:
-See major comment 1): if the soil carbonate clumped T’s are indeed misplaced with respect to hiatus 1, the figure needs to be adjusted.
Supplementary materials:
Supplementary Table 1: what are the _1 and _2 samples? Add the information to the table caption.
General comments:
-The manuscript lacks coordinates. Add them for the clumped samples, the start and end of the section, as well as some intermediate points (e.g. the hiatuses, the dates tuffs, the fossil level). This is incredibly important for other scientists who would like to visit and/or study the sites.
-Pay attention to sub- and superscripts throughout the manuscript (CO2, Δ47, δ13C etc.)
-Use words for cardinal numbers less than 10 (as per journal policy)
Maud Meijers