the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 14 Jan 2025
Climate change drove Late Miocene to Pliocene rise and fall of C4 vegetation at the crossroads of Africa and Eurasia (Anatolia, Türkiye)
Abstract. Life on Earth has been capitalizing on the C3 photosynthetic pathway for 2.8 billion years. However, in the world’s grasslands that emerged since the Paleogene, C4 vegetation expanded dramatically between 8 and 3 Ma in response to climatic changes. Here we present the first comprehensive Late Miocene to Holocene δ13C soil carbonate record from the Eastern Mediterranean region (Anatolia) to reconstruct long-term geographic distributions of C3 and C4 plants, a region with patchy records compared to parts of Africa and Asia. Our results show a colonization of Anatolian floodplains by C4 biomass by 9.9 Ma, similar to regions in NW and E Africa, followed by a transition from this mixed C3-C4vegetation to C4 dominance between ca. 7.1 Ma and 4.9 Ma. The transition coincides with a similar shift from C3 to C4 vegetation in southern Asia and is generally attributed to the Late Miocene Cooling in response to decreasing atmospheric pCO2. However, the Anatolian paleoecosystem patterns are unique due to a rapid and permanent return to C3 dominance in the Early Pliocene, which is not observed elsewhere and occurs simultaneously with the disappearance of the open environment-adapted large mammal Pikermian chronofauna. We propose that this return to C3 vegetation was caused by paleoclimatic processes that regionally shifted precipitation from the warm to the cool season, resembling the modern Mediterranean climate. In conclusion, changes in rainfall seasonality under subhumid climate, rather than increased aridity, drove the demise of C4-dominated floodplains and the open-environment adapted Pikermian chronofauna at the Eurasian-African crossroads.
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Status: final response (author comments only)
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RC1: 'Comment on cp-2024-80', Funda Akgün, 04 Feb 2025
Dear Editor,
I have read entitled “Climate change drove Late Miocene to Pliocene rise and fall of C4 vegetation at the crossroads of Africa and Eurasia (Anatolia, Türkiye)” detailed in all my good intentions for the study. This study was focused on using duraylı isotope data, mammal and palaeobotany/paleoclimate based on previous studies. It includes major corrections noted on the manuscript (given below). The main problem is that approaches have been made on the Anatolian and Aegean scale based on data from narrow areas with sedimentological characteristics, which are not specified in the results and abstract. The need for narrowing and simplification of these approaches has been tried to be pointed out in the manuscript. In conclusion, this manuscript is suitable for publication in your journal after the major corrections and edits indicated.
Major Corrections:
- Table S2 should be updated as Karacaören- early Pliocene, Bingol-Halifan-late Pliocene, Erzurum-Horosan-late Pliocene (Original Time Slice) as stated in the related manuscript. In the related references, the ages of the samples from these locations are given as listed. Comments and figures related to this correction should be revised.
- It is not clear how the concepts of Plateau and Coastal given in Table S2 are evaluated within the interpretations of the manuscript.
- The locations marked in the Figure 1 are all in Central Anatolia, Rhodes, Ermenek, Adana are in the Mediterranean and Pikermi, and Samos is in the Aegean and Mediterranean belt. Aegean is used for Western and GB Anatolia. For this reason, the term Anatolian-Aegean region should be replaced by another term to include all locations. Otherwise, it is understood that the data used in the manuscript belong to the Aegean region of Anatolia. Also, it is useful to evaluate it later in the manuscript.
- In the Miocene and Pliocene, as in the present day, different microclimatic conditions (such as topography, elevation, distance to the sea, etc.) were effective from region to region within Anatolia. For this reason, the interpretations made in the Aegean region throughout the manucript are confusing due to the inadequacy in the definition of Anatolia-Aegean region.
- The multilayered presence of Central Anatolian volcanic activity must have had a more localized impact on the vegetation in CAP region than the general climatic conditions. The notion that this influence was such that C4 vegetation dominated the whole of Anatolia should be used with caution.
Best regards
Funda AKGÜN
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RC2: 'Comment on cp-2024-80', Anonymous Referee #2, 19 Mar 2025
In this manuscript, the authors present a new record of pedogenic carbonate δ13C data from the Anatolian floodplains. This paper fills in a critical regional gap in the geologic record and provides contrast with African and Asian records of C3/C4 turnover. My largest concern with this manuscript is that the way the information on samples and data are currently published make it challenging to evaluate the quality of the δ13C data. There is useful data in the supplemental tables that should be moved to the main text to make the manuscript easier to evaluate.
Largest concerns:
- The amount of data published in the supplement does not make it possible to evaluate the quality of the δ13C data published.
- In the methods section the authors should describe what kinds of corrections were done on the data (i.e. linearity, drift, scale corrections). I suggest creating a new supplementary table where the authors publish at least the raw measured values of both samples and standards, as well as the corrected values. Best practice would be to keep a record in that spreadsheet of each correction step. That way, if standard values are updated in the future, it is possible to bring this data into a new reference frame. If there is an associated R or Python script for these corrections, this should be published as well.
- Were the data all collected in one session? Multiple sessions? Please be clear about how that influenced data correction.
- More detail is need about the nodules themselves is needed. What drove sampling choices? Why did the authors run more nodules from some samples and not others? More info on diagenetic evaluation is needed – are there any microscopy or CL images? Please include any images of nodules in the supplement. What diagenetic signs were you looking for? (line 168). How did that influence drilling choices? Given burial depth (line 170), I think the authors are probably right on diagenesis, but just a little more detail would put readers at ease.
- The authors should also strongly consider putting the δ18O data in the supplement, even if it’s not discussed in the manuscript so those data are freely available to future users. Improvements in pedogenic carbonate modern calibrations (using Δ17O and Δ47) are showing that those data might be more useful than previously thought. Make sure that it is clear how those data were corrected as well.
Line by line comments:
Line 23-24: This sentence is confusing, please clarify
Figure 1: The hexagon is hard to differentiate, consider adding color (maybe something in a cool color spectrum?) or changing the shape so it stands out.
Lines 64 – 75: I recognize that this is a stylistic choice, but I find it jarring to put the conclusions into the introduction of a paper in this format. I think it makes sense for shorter format papers, but here it feels like putting the cart before the horse. Consider removing or reframing
Line 88: did you measure any rhizoliths? If so, need to clearly differentiate that data.
Line 88: It would be more appropriate to use Munsell soil colors here
Line 109: Because so much of the manuscript relies on the geochronology being right, it is worth it to describe in a little greater detail in the manuscript. I know its published, but make it easier for the readers to evaluate the quality of the geochron data. What kind of radiometric dating? What kind of age model?
Line 123: Stronger justification of the exclusion of this data is needed since so much of the final conclusion is based on hydrologic change in the region.
Results section (lines 131 – 159):
- I would suggest that the authors consider significantly shortening the results, and instead translate much of the text into a table. There is a lot of useful information hidden in table S1 that should be moved to the main text (for example, moving some of the geochron details would help alleviate the line 109 comment).
- It may be more useful to describe the salient trends that we can see in the data rather than the range of isotope values.
- The authors present sample means for each of their samples, but the underlying data structure is clearly not a normal distribution (some samples are surely biased by outliers), and so the authors should report median values as well as mean values. The authors should strongly consider calculating and reporting the 2 standard error value for their samples. This is becoming the more common-place error statistic to report in the stable isotope community.
- Be clearer as results are presented if you continue to just report 1 SD (again, this would be easier in a table)
- Reference figure 2 earlier in the results
Line 170: please also edit this sentence to reflect the burial depth for Mustafapaşa (400 m).
Line 176: are there any paleosol characteristics that support or refute this? Color, texture, morphology, etc.
Figure 2:
- In A: please add a better minor grid and make the average values solid to make them easier to see and differentiate?
- In B & C – please make the data points a size or two larger to make it easier to read and see.
Line 194: include citations here
Lines 214 – 232: The way this paragraph is written (juxtaposing the contradicting data) is a little confusing, and needs a little reorganization and refining.
Line 244: is this a decrease of up to 10°C?
Line 264: indent new paragraph
Figure 3: please make it clearer what AMOC + and MSC in c) are in the caption. Strongly consider swapping the x axis direction, with 0 Ma on the right side. This ultimately is stylistic, but it is quite standard in paleoclimate (e.g. Westerhold et al., 2020). It would make your plot easier for other scientists to use.
Line 314: This mechanism has been shown in modern experimental grasslands. The authors should make reference to Knapp et al., 2020 (https://doi.org/10.1073/pnas.1922030117)
Table S1:
- Please make the headings for latitude and longitude clearer (rather than N / E), please also include the reference frame (e.g. WGS84)
- Please justify the merging of the Bakali sites more clearly. It is also unclear where the age for this sample came from. Please clarify.
- Are there any estimates of paleoelevation? If so, please include
- Chronologies: If there are samples where adjustments for sedimentation rate were made, please make that clear
Citation: https://doi.org/10.5194/cp-2024-80-RC2 - The amount of data published in the supplement does not make it possible to evaluate the quality of the δ13C data published.
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