Silicate Weathering in the Semi-Arid Southern Pyrenees During the PETM: Lithium Isotope Evidence

Jaimes-Gutierrez, Rocio; Prieur, Marine; Wilson, David J.; Pogge von Strandmann, Philip A. E.; Pucéat, Emmanuelle; Adatte, Thierry; Spangenberg, Jorge E.; Castelltort, Sébastien

doi:10.5194/egusphere-2025-2619

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https://doi.org/10.5194/egusphere-2025-2619

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26 Jun 2025

| 26 Jun 2025

Silicate Weathering in the Semi-Arid Southern Pyrenees During the PETM: Lithium Isotope Evidence

Rocio Jaimes-Gutierrez, Marine Prieur, David J. Wilson, Philip A. E. Pogge von Strandmann, Emmanuelle Pucéat, Thierry Adatte, Jorge E. Spangenberg, and Sébastien Castelltort

Abstract. The Palaeocene-Eocene Thermal Maximum (PETM), a hyperthermal event ~56 Ma ago, allows the Earth system response to abrupt climate change to be explored. Recent investigations link the PETM with a negative lithium isotope (δ⁷Li) excursion, interpreted as an increase in continental silicate weathering fluxes, which can regulate Earth’s surface temperature over geological timescales. However, the silicate weathering response under different climatic regimes has yet to be constrained. Here we aim to address the chemical weathering response to the PETM in the semi-arid Southern Pyrenees, and to explore how different archives (i.e., clays and carbonate nodules) record the weathering changes.

We investigated two continental sections in the southern Pyrenees. In the Esplugafreda section, we measured δ⁷Li values as a silicate weathering proxy and ε_Nd values as a provenance proxy in the clay minerals. In the Rin section, we characterised the PETM locally by analysing δ¹³C values in organic matter and examined the clay mineralogy in the paleosols, as well as measuring δ⁷Li values in clays and carbonate nodules to trace silicate weathering. In the Esplugafreda section, we observe temporally stable ε_Nd values, while the δ⁷Li_clay record shows two small positive excursions, one during the Pre-Onset Excursion (~0.7‰) and a second during the body of the PETM (~0.8‰). In the Rin section, the PETM is characterised by a negative carbon isotope excursion of 2.8‰. The clays consist mostly of illite/smectite, illite, and kaolinite, consistent with a seasonal climate in the region, and we find a positive δ⁷Li_clay excursion of ~0.8‰.

The combined δ⁷Li_clays and ε_Nd records indicate increased clay formation and increased silicate weathering fluxes in the semi-arid Pyrenees, while the sediment provenance was stable. The δ⁷Li values in the carbonate nodules indicate more variability, potentially due to clay contamination. Constrained by the bedrock type of dominantly reworked sediments and the seasonal precipitation regime, the initially low weathering rate, despite a comparatively high weathering intensity, evolved towards a higher weathering rate with enhanced erosion during the PETM.

Received: 04 Jun 2025 – Discussion started: 26 Jun 2025

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31 Mar 2026

Silicate weathering in the semi-arid Southern Pyrenees during the PETM: lithium isotope evidence

Rocio Jaimes-Gutierrez, Marine Prieur, David J. Wilson, Philip A. E. Pogge von Strandmann, Emmanuelle Pucéat, Thierry Adatte, Jorge E. Spangenberg, and Sébastien Castelltort

Clim. Past, 22, 709–727, https://doi.org/10.5194/cp-22-709-2026,https://doi.org/10.5194/cp-22-709-2026, 2026

Short summary

Rocio Jaimes-Gutierrez, Marine Prieur, David J. Wilson, Philip A. E. Pogge von Strandmann, Emmanuelle Pucéat, Thierry Adatte, Jorge E. Spangenberg, and Sébastien Castelltort

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2025-2619', Gaojun Li, 18 Jul 2025

In this manuscript, the authors analyze the lithium and neodymium isotopes of two sections from the southern Pyrenees, deposited during the PETM event (~ 56 Ma ago). They report a positive excursion of ~0.8‰ in the clay-size fraction lithium isotopic ratios during the PETM in both sections, while the neodymium isotope data indicate stable sediment provenance. They suggest the positive excursions in lithium isotopes reflect a decline in weathering intensity and congruency, potentially linked to the enhanced formation of secondary clays during continental weathering. To better understand how Earth’s climate regulates itself, it is essential to unravel the linkages among denudation, weathering and climate. I believe this paper improves our understanding of chemical weathering at hyperthermal events. The language of this manuscript is well-revised and clear enough, and the data broadly support the authors' interpretations. However, several sections of the manuscript raise important questions or require clarification, as outlined below. Overall, I recommend to accept this manuscript after minor revisions.

First of all, the authors propose increased denudation and weathering flux during the PETM, while also suggesting that weathering intensity (W/D) declined (e.g. Lines 525-533). I am wondering are there any direct geological or sedimentological evidences for increased erosion or tectonic uplift in the southern Pyrenees during the PETM? Because in the absence of uplift, one would expect weathering intensity to rise with increasing temperature and precipitation.

Second, the manuscript suggests that increased kaolinite abundance reflects enhanced secondary clay formation (Lines 547–549). However, kaolinite abundance alone may not reliably indicate the total formation flux of secondary clays, as it does not account for other clay mineral phases. I think it’s not easy to determine the total formation flux of secondary clays, but one can consider an extreme case: the observed kaolinite enrichment could also result from the dissolution of other clays.

Third, several studies (e.g., Pistiner & Henderson, 2003; Golla et al., 2021) suggest that lithium isotope fractionation is mineral-dependent. Since the authors already present clay mineralogy data, it would strengthen the paper to discuss how variations in mineral assemblages might influence the lithium isotopic fractionation factor (Δ⁷Li_water-clay) and, consequently, the observed δ⁷Li values.

Finally, the manuscript assumes that δ⁷Li variations in the clay-size fraction reflect continental weathering processes exclusively, with negligible contribution from marine authigenic alumino-silicate clays. However, an increased fraction of marine authigenic alumino-silicate clays during the PETM could also elevate the clay δ⁷Li values. Could the authors provide some additional constraints to rule out this possibility?

Below are some minor issues:

In Lines 111-112, the term “weathering efficiency” is ambiguous. I guess this refers to the CO₂ consumption flux as suggested by Bufe et al., 2024. It would be better if the authors can make this clearer.

In Lines 115-116, How can weathering rates increase with erosion under kinetically-limited regime? I suppose this is only the case for supply-limited regimes.

In Lines 493-495, the authors suggest enhanced clay formation in lowlands during the PETM. Is there evidence to support this? Could increased runoff instead dilute solute concentrations, thereby suppressing clay precipitation? Also, is it realistic to assume that enhanced clay formation in lowlands could compensate for reduced formation in uplands?

In Lines 517-522, I might be wrong, but higher temperatures during the PETM would likely reduce the lithium isotope fractionation (i.e. decrease Δ⁷Li_water-clay) during clay formation. The secondary clay formed at this warm period should have a closer δ⁷Li to the starting solution (or river water) (δ⁷Li_{secondary-clay}= δ⁷Li_water – Δ⁷Li_water-clay). Assuming a constant δ⁷Li value of river water (δ⁷Li_water) during the period of interest, the clay formed at syn-PETM should have higher δ⁷Li values, rather than lower values.

In Figure 1C, there are three different blue areas (from light to dark), but only two of them are explained in the legend. Additionally, the meaning of the white-striped area in panel B is unclear and should be clarified.

Citation: https://doi.org/10.5194/egusphere-2025-2619-RC1
- AC1:
  'Reply on RC1', Rocio Jaimes-Gutierrez, 08 Sep 2025
  We sincerely thank Reviewer 1, Gaojun Li, for his constructive feedback, support of the manuscript, and thoughtful review suggestions, which will certainly help improve the quality of the paper. Below, we address each of the points raised.
  Evidence for increased erosion and denudation in the Southern Pyrenees
  
  We agree that independent evidence for enhanced denudation during the PETM is essential. In the Southern Pyrenean foreland basin, several sedimentological records attest to rapid erosion and enhanced sediment supply during this interval. For example, the deposition of the massive conglomeratic megafan unit (Claret Conglomerate; Schmitz & Pujalte, 2003, 2007; Pujalte et al., 2015, 2016) reflects increased sedimentary fluxes that seem to be attributed to extreme precipitation events (Prieur et al., 2025). Additional indicators include enhanced channel mobility (Chen et al., 2018) and an increase in Microcodium abundance and export to the oceans (Prieur et al., 2024). Together, these records point to a marked intensification of erosion and sediment transfer, consistent with our interpretation of increased weathering fluxes. We will integrate these references explicitly in the revised text to make the connection between the isotopic evidence and sedimentological records clearer.
  
  Kaolinite abundance and secondary clay formation
  
  We acknowledge the reviewer’s point that kaolinite abundance alone cannot serve as a straightforward proxy for enhanced secondary clay formation. Kaolinite enrichment could, in principle, result from processes such as the erosion and redeposition of pre-PETM clays. While we discuss this limitation later in the manuscript, we emphasize that with the currently available mineralogical data, it is not possible to unequivocally distinguish between neoformed clays and reworked/pre-PETM clays.
  
  Nonetheless, the positive δ⁷Li excursion observed in our dataset suggests an overall increase in clay formation during the PETM. In this context, the kaolinite data remain consistent with such an interpretation, especially when viewed together with the isotopic evidence. Importantly, global mass-balance calculations indicate that the magnitude of the seawater δ⁷Li excursion during the PETM cannot be explained solely by erosion or recycling of previously formed clays; rather, it requires enhanced formation of new secondary clays (Pogge von Strandmann et al., 2021). This supports our interpretation that the observed kaolinite increase reflects intensified continental weathering and clay neoformation, even though kaolinite alone does not capture the full spectrum of clay mineral phases involved.
  
  Lithium isotope fractionation and mineral dependence
  
  We thank the reviewer for this important observation. Indeed, Li isotope fractionation could be mineral-dependent, which may affect the interpretation of δ⁷Li variations. Since we already present clay mineralogy data, we agree that explicitly discussing how variations in mineral assemblages could influence the fractionation factor between water and clays will strengthen our interpretation. In the revised manuscript, we will add a discussion of the potential role of mineralogy in influencing δ⁷Li values, while noting that the consistent trends in δ⁷Li values across sections suggest that mineral assemblage changes alone cannot fully explain the observed excursion.
  
  Marine authigenic clay contribution
  
  The reviewer raises an important question regarding the possible role of marine authigenic alumino-silicate clays. Based on the coastal but dominantly continental depositional setting of the Rin section, the formation of authigenic clays is possible but unlikely to have been significant. Authigenic clay precipitation typically occurs in deeper marine settings where prolonged water–sediment interaction facilitates diagenetic mineral growth. In contrast, the shallow-water depositional environments of our studied sections are not conducive to substantial authigenic clay formation. Additionally, even if authigenic clay formation occurred, its abundance would be minimal relative to the large detrital clay input in the near-shore environment.
  
  We thank Reviewer 1 again for the detailed and constructive feedback. We will incorporate the suggested clarifications and additional discussions into the revised manuscript, which we are confident will improve its clarity and robustness.
  
  Citation: https://doi.org/10.5194/egusphere-2025-2619-AC1
RC2:
'Comment on egusphere-2025-2619', Anonymous Referee #2, 16 Aug 2025
General comments:
This manuscript reports new geochemical (δ⁷Li, εNd, δ¹³C) and mineralogical data on two well-preserved Palaeocene-Eocene sedimentary floodplain sections in the Pyrenees. The objective is to reconstruct the regional changes in chemical weathering and physical erosion during the PETM warming event and the aftermath to characterize the response of the Earth system to warming events. The authors found a positive δ⁷Li excursion in the clay fraction of both sections during the main body of the PETM. They interpret these results as reflecting a decrease of the weathering intensity (higher chemical erosion and even higher physical erosion) during the PETM because of the intensification of the hydrological cycle and a more extensive clay formation in the floodplains.
Overall, this is a neat study and a valuable scientific contribution to the research field on the PETM. It is well written, the data are of high quality, and the interpretation and arguments are convincing. There are only a few aspects of the manuscript that should be improved, in particular the presentation of the interpretative framework and the implications, before final acceptance. My recommendation is publication after minor revisions. The main revisions I suggest are:
Clarify the interpretative framework of Li isotopes in detrital sediments (section 1.2). In my opinion, some statements in this section are not in accordance with results from published studies (see more details below).

Discuss in more details the comparison and implications with other Li isotopes PETM records. I suggest moving the paragraph lines 464-473 after discussing the results from the Pyrenees and modifying it to compare directly the results from various records and places. Why a positive excursion in the Pyrenees and a negative excursion in other settings? Is it because of the different geomorphic environment (deep regolith and transport-limited weathering in the pyrenees)? How does it compare with the other studied floodplain section, in the Bigorn basin (Ramos et al., 2022)?

Discuss in more detail the reasons for the very low δ⁷Li values in the Esplugafreda section during the recovery period. This does not appear to be a simple return to initial conditions, but rather a further increase in weathering intensity (lower δ⁷Li) associated with regolith deepening and soil shielding relative to pre-PETM conditions. If this is the case, what are the implications for CO₂ removal through silicate weathering, given that such highly weathered settings are characterized by a weak weathering response and therefore act as inefficient sinks for atmospheric CO₂ (Penman et al., 2020)? The timescale of the PETM recovery and the role of silicate weathering remain debated, and this study could provide useful new constraints.

Add a figure with the average values (δ⁷Li, εNd, δ¹³C, mineralogy) during each period (pre, POE, onset, body and recovery) for both sections (on the same figure). This would really help the reader to have a global overview of the main results and evolution through time.

In addition, the potential influence of marine clay formation (reverse weathering) on Li isotopes is not mentioned or discussed. Do you have any evidence to dismiss it for the Rin section? The study from Zhang et al., (2022) on the Ainsa paleo-delta shows that marine clay formation results in lowering of the δ⁷Li of sediments.
Specific comments:
- Line 111: define « weathering efficiency ». Note that this hypothesis of maximum weathering rate at moderate erosion rate (the “speed limit”) proposed by some authors (Dixon and von Blanckenburg, 2012; Gabet and Mudd, 2009) has been challenged by others (e.g. Larsen et al., 2014; West, 2012).
- Lines 139-145: This does not appear to be consistent with findings reported in previous studies. At high W/D both clay formation and clay dissolution processes are taking place, either in different part of the weathering profile (top regolith vs deep regolith; e.g. Chapela Lara et al., 2022; Clergue et al., 2015) or different part of the catchment (e.g. see figure 10 in Dellinger et al., 2015 ; figure 3 in Henchiri et al., 2016; Fries et al., 2019). Therefore, at high W/D, rivers do transport modern neoformed clays from weathering profiles, and hence there is NO evidence for “minimal clay neoformation” (on the contrary).
- Lines 150-154: what is the evidence for “fewer of the coarser-grained primary minerals carried in rivers are expected to be transported into offshore sites, the clay weathering signal may generally be recorded more clearly in marine sites”? I see several problems here:
First, the Dellinger et al., 2017 relationship has been observed for fine sediments (< 63 microns) not “coarse-grained primary minerals”.
Second, several studies on the Yangtze estuary (Yang et al., 2021, 2025) show the opposite sediment transport process to the one suggested is suggested by the authors, i.e. preferential transport of coarse-grained primary minerals offshore relative to clay minerals (“the offshore transport of SPM in the Changjiang Estuary may result in the preferential flocculation and deposition of clay minerals during the flooding season, while primary minerals or other fine-grained particles tend to be resuspended and carried seaward by currents” (Yang et al., 2021)).
Third, even if there are fewer primary minerals in the <2 μm fraction relative to the <63 μm fraction, primary clays and other minerals (feldspar, micas) are still present in the <2 μm fraction (e.g. Liu et al., 2025)
I suggest revision of the presented interpretation framework (Fig. 2) in accordance with existing publications.
- Section 4.1: is there any correlation between δ⁷Li and the mineralogy of clays? I think this should be discussed somewhere in the manuscript since different clays could have distinct fractionation factor during process of Li incorporation or adsorption into clays.
- Section 4.3: were the Li concentration measured on those samples? Any weathering-related changes in Li/Ti or Li/Al in both sections?
- Lines 494-495: see also all the studies that report increase dissolved Li isotope composition and clay formation in rivers when crossing large floodplains (e.g. Bagard et al., 2015; Dellinger et al., 2015; Maffre et al., 2020; Pogge von Strandmann et al., 2017; Pogge von Strandmann and Henderson, 2015). The proposed interpretation here, i.e. “the shift towards increased incongruent weathering, characterized by enhanced clay formation in the floodplain deposits” is consistent with all these studies on modern rivers with floodplains.
- Lines 497-499: see also the study from Xu et al., (2021)
- Lies 502-504: This is not clear to me, why faster runoff results in a positive δ⁷Li excursion in the clays?
- Figure 2 & 3: could be combined (panel A and Panel B)
- Figure 4: I suggest indicating the different periods (pre, POE, onset, body and recovery) on the right of the figure to help the reader not so familiar with the PETM timing and evolution.
References:
Bagard, M.-L., West, A.J., Newman, K., Basu, A.R., 2015. Lithium isotope fractionation in the Ganges–Brahmaputra floodplain and implications for groundwater impact on seawater isotopic composition. Earth and Planetary Science Letters 432, 404–414. https://doi.org/10.1016/j.epsl.2015.08.036
Chapela Lara, M., Buss, H.L., Henehan, M.J., Schuessler, J.A., McDowell, W.H., 2022. Secondary Minerals Drive Extreme Lithium Isotope Fractionation During Tropical Weathering. Journal of Geophysical Research: Earth Surface 127, e2021JF006366. https://doi.org/10.1029/2021JF006366
Clergue, C., Dellinger, M., Buss, H.L., Gaillardet, J., Benedetti, M.F., Dessert, C., 2015. Influence of atmospheric deposits and secondary minerals on Li isotopes budget in a highly weathered catchment, Guadeloupe (Lesser Antilles). Chemical Geology 414, 28–41. https://doi.org/10.1016/j.chemgeo.2015.08.015
Dellinger, M., Gaillardet, J., Bouchez, J., Calmels, D., Louvat, P., Dosseto, A., Gorge, C., Alanoca, L., Maurice, L., 2015. Riverine Li isotope fractionation in the Amazon River basin controlled by the weathering regimes. Geochimica et Cosmochimica Acta 164, 71–93. https://doi.org/10.1016/j.gca.2015.04.042
Dixon, J.L., von Blanckenburg, F., 2012. Soils as pacemakers and limiters of global silicate weathering. Comptes Rendus Geoscience 344, 597–609.
Fries, D.M., James, R.H., Dessert, C., Bouchez, J., Beaumais, A., Pearce, C.R., 2019. The response of Li and Mg isotopes to rain events in a highly-weathered catchment. Chemical Geology 519, 68–82. https://doi.org/10.1016/j.chemgeo.2019.04.023
Gabet, E.J., Mudd, S.M., 2009. A theoretical model coupling chemical weathering rates with denudation rates. Geology 37, 151–154.
Henchiri, S., Gaillardet, J., Dellinger, M., Bouchez, J., Spencer, R.G.M., 2016. Riverine dissolved lithium isotopic signatures in low-relief central Africa and their link to weathering regimes. Geophys. Res. Lett. 43, 2016GL067711. https://doi.org/10.1002/2016GL067711
Larsen, I.J., Almond, P.C., Eger, A., Stone, J.O., Montgomery, D.R., Malcolm, B., 2014. Rapid soil production and weathering in the Southern Alps, New Zealand. Science 343, 637–640.
Liu, Y., Yang, Y., Yan, Z., Jin, Z., Ye, C., Pogge von Strandmann, P.A.E., Deng, L., Liu, X., Fang, X., 2025. Lithium isotopes as a chemical weathering proxy in lacustrine sediments: Implications from multiphase leaching analyses. Global and Planetary Change 253, 104986. https://doi.org/10.1016/j.gloplacha.2025.104986
Maffre, P., Goddéris, Y., Vigier, N., Moquet, J.-S., Carretier, S., 2020. Modelling the riverine δ7Li variability throughout the Amazon Basin. Chemical Geology 532, 119336. https://doi.org/10.1016/j.chemgeo.2019.119336
Pogge von Strandmann, P.A.E., Frings, P.J., Murphy, M.J., 2017. Lithium isotope behaviour during weathering in the Ganges Alluvial Plain. Geochimica et Cosmochimica Acta 198, 17–31. https://doi.org/10.1016/j.gca.2016.11.017
Pogge von Strandmann, P.A.P., Henderson, G.M., 2015. The Li isotope response to mountain uplift. Geology 43, 67–70.
Ramos, E.J., Breecker, D.O., Barnes, J.D., Li, F., Gingerich, P.D., Loewy, S.L., Satkoski, A.M., Baczynski, A.A., Wing, S.L., Miller, N.R., Lassiter, J.C., 2022. Swift Weathering Response on Floodplains During the Paleocene-Eocene Thermal Maximum. Geophysical Research Letters 49, e2021GL097436. https://doi.org/10.1029/2021GL097436
West, A.J., 2012. Thickness of the chemical weathering zone and implications for erosional and climatic drivers of weathering and for carbon-cycle feedbacks. Geology 40, 811–814. https://doi.org/10.1130/G33041.1
Xu, Z., Li, T., Li, G., Hedding, D.W., Wang, Y., Gou, L.-F., Zhao, L., Chen, J., 2021. Lithium isotopic composition of soil pore water: Responses to evapotranspiration. Geology. https://doi.org/10.1130/G49366.1
Yang, C., Cao, F., Xu, J., Lu, Y., Bi, L., Zheng, H., Yang, S., 2025. Lithium isotopic constraints on systematic biases in reconstructing continental weathering processes from bulk sedimentary records at continental margins. Global and Planetary Change 253, 104942. https://doi.org/10.1016/j.gloplacha.2025.104942
Yang, Vigier, N., E. Lian, Z. Lai, S. Yang, 2021. Decoupling of dissolved and particulate Li isotopes during estuarine processes. Geochemical Perspectives Letters 19, 40–44. https://doi.org/10.7185/geochemlet.2133
Zhang, X. (Yvon), Gaillardet, J., Barrier, L., Bouchez, J., 2022. Li and Si isotopes reveal authigenic clay formation in a palaeo-delta. Earth and Planetary Science Letters 578, 117339. https://doi.org/10.1016/j.epsl.2021.117339
Citation: https://doi.org/10.5194/egusphere-2025-2619-RC2
- AC2:
  'Reply on RC2', Rocio Jaimes-Gutierrez, 08 Sep 2025
  We thank Reviewer 2 for the constructive and positive evaluation of our manuscript, and for the detailed comments and suggestions. We are pleased that the reviewer finds the study valuable and the dataset of high quality. Below, we provide a point-by-point response to each major comment. We will revise the manuscript accordingly in the next stage.
  
  1. Clarify the interpretative framework of Li isotopes in detrital sediments
  We thank the reviewer for highlighting the importance of clarifying the Li isotope interpretation framework. We will revise Section 1.2 to provide a clearer and more nuanced description of the Li isotope framework. Specifically, we will:
  Explicitly explain that at high W/D both clay neoformation and dissolution can occur at different depths in the profile or in different parts of the catchment (Chapela Lara et al., 2022; Clergue et al., 2015; Dellinger et al., 2015; Henchiri et al., 2016; Fries et al., 2019).
  
  Rephrase the current statement on “minimal clay neoformation” to emphasize that modern rivers can transport significant amounts of neoformed clays.
  
  2. Discuss more thoroughly the comparison and implications with other PETM Li isotope records. Why positive excursion in the Pyrenees vs. negative elsewhere?
  We agree with the reviewer and will explore the mechanisms that could have resulted in a different excursion, linking the importance of the climatic setting and the starting weathering regime to the W/D evolution during a warming event such as the PETM. We will follow the presentation of the Pyrenean results and expand it into a comparative discussion. In particular, we will contrast our positive excursion with negative excursions reported elsewhere, highlight the geomorphic and climatic context, and integrate a discussion, e.g., Pogge von Strandmann et al. (2021), Ramos et al. (2022), Chen et al. (2023), Jones et al. (2023).
  
  3. Discuss in more detail the low δ⁷Li values in Esplugafreda during recovery. Could indicate further increase in weathering intensity and inefficient CO₂ sink behavior?
  We appreciate this suggestion and will explore the recovery dynamics. We will expand the discussion on the Esplugafreda recovery values to emphasize that they likely reflect deeper regolith development and enhanced soil shielding compared to syn-PETM conditions. This perspective adds an important nuance to the PETM recovery debate, including the CO₂ budgets across the PETM.
  4. Add a figure summarizing average values (δ⁷Li, εNd, δ¹³C, mineralogy) for each period.
  We agree that such a summary figure will greatly help readers. We will add a new figure showing average values for the five intervals (pre-PETM, POE, onset, body, recovery) for both sections.
  
  5. Influence of marine clay formation (reverse weathering) is not discussed. Could this affect Rin section?
  We thank the reviewer for raising this important point, which connects to Reviewer 1’s fourth comment on the potential role of marine authigenic clays. Based on the coastal but dominantly continental depositional setting of the Rin section, the formation of authigenic clays is possible but unlikely to have been significant. We will add a statement clarifying its setting and briefly discussing why reverse weathering is unlikely here. Furthermore, even if authigenic clay formation occurred, its abundance would be minimal relative to the large detrital clay input in the near-shore environment.
  
  We thank Reviewer 2 again for the thorough and thoughtful review. We will further apply the minor corrections proposed during the review process. We are confident that addressing these points will significantly improve the clarity and impact of our manuscript.
  
  Citation: https://doi.org/10.5194/egusphere-2025-2619-AC2

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2025-2619', Gaojun Li, 18 Jul 2025

In this manuscript, the authors analyze the lithium and neodymium isotopes of two sections from the southern Pyrenees, deposited during the PETM event (~ 56 Ma ago). They report a positive excursion of ~0.8‰ in the clay-size fraction lithium isotopic ratios during the PETM in both sections, while the neodymium isotope data indicate stable sediment provenance. They suggest the positive excursions in lithium isotopes reflect a decline in weathering intensity and congruency, potentially linked to the enhanced formation of secondary clays during continental weathering. To better understand how Earth’s climate regulates itself, it is essential to unravel the linkages among denudation, weathering and climate. I believe this paper improves our understanding of chemical weathering at hyperthermal events. The language of this manuscript is well-revised and clear enough, and the data broadly support the authors' interpretations. However, several sections of the manuscript raise important questions or require clarification, as outlined below. Overall, I recommend to accept this manuscript after minor revisions.

First of all, the authors propose increased denudation and weathering flux during the PETM, while also suggesting that weathering intensity (W/D) declined (e.g. Lines 525-533). I am wondering are there any direct geological or sedimentological evidences for increased erosion or tectonic uplift in the southern Pyrenees during the PETM? Because in the absence of uplift, one would expect weathering intensity to rise with increasing temperature and precipitation.

Second, the manuscript suggests that increased kaolinite abundance reflects enhanced secondary clay formation (Lines 547–549). However, kaolinite abundance alone may not reliably indicate the total formation flux of secondary clays, as it does not account for other clay mineral phases. I think it’s not easy to determine the total formation flux of secondary clays, but one can consider an extreme case: the observed kaolinite enrichment could also result from the dissolution of other clays.

Third, several studies (e.g., Pistiner & Henderson, 2003; Golla et al., 2021) suggest that lithium isotope fractionation is mineral-dependent. Since the authors already present clay mineralogy data, it would strengthen the paper to discuss how variations in mineral assemblages might influence the lithium isotopic fractionation factor (Δ⁷Li_water-clay) and, consequently, the observed δ⁷Li values.

Finally, the manuscript assumes that δ⁷Li variations in the clay-size fraction reflect continental weathering processes exclusively, with negligible contribution from marine authigenic alumino-silicate clays. However, an increased fraction of marine authigenic alumino-silicate clays during the PETM could also elevate the clay δ⁷Li values. Could the authors provide some additional constraints to rule out this possibility?

Below are some minor issues:

In Lines 111-112, the term “weathering efficiency” is ambiguous. I guess this refers to the CO₂ consumption flux as suggested by Bufe et al., 2024. It would be better if the authors can make this clearer.

In Lines 115-116, How can weathering rates increase with erosion under kinetically-limited regime? I suppose this is only the case for supply-limited regimes.

In Lines 493-495, the authors suggest enhanced clay formation in lowlands during the PETM. Is there evidence to support this? Could increased runoff instead dilute solute concentrations, thereby suppressing clay precipitation? Also, is it realistic to assume that enhanced clay formation in lowlands could compensate for reduced formation in uplands?

In Lines 517-522, I might be wrong, but higher temperatures during the PETM would likely reduce the lithium isotope fractionation (i.e. decrease Δ⁷Li_water-clay) during clay formation. The secondary clay formed at this warm period should have a closer δ⁷Li to the starting solution (or river water) (δ⁷Li_{secondary-clay}= δ⁷Li_water – Δ⁷Li_water-clay). Assuming a constant δ⁷Li value of river water (δ⁷Li_water) during the period of interest, the clay formed at syn-PETM should have higher δ⁷Li values, rather than lower values.

In Figure 1C, there are three different blue areas (from light to dark), but only two of them are explained in the legend. Additionally, the meaning of the white-striped area in panel B is unclear and should be clarified.

Citation: https://doi.org/10.5194/egusphere-2025-2619-RC1
- AC1:
  'Reply on RC1', Rocio Jaimes-Gutierrez, 08 Sep 2025
  We sincerely thank Reviewer 1, Gaojun Li, for his constructive feedback, support of the manuscript, and thoughtful review suggestions, which will certainly help improve the quality of the paper. Below, we address each of the points raised.
  Evidence for increased erosion and denudation in the Southern Pyrenees
  
  We agree that independent evidence for enhanced denudation during the PETM is essential. In the Southern Pyrenean foreland basin, several sedimentological records attest to rapid erosion and enhanced sediment supply during this interval. For example, the deposition of the massive conglomeratic megafan unit (Claret Conglomerate; Schmitz & Pujalte, 2003, 2007; Pujalte et al., 2015, 2016) reflects increased sedimentary fluxes that seem to be attributed to extreme precipitation events (Prieur et al., 2025). Additional indicators include enhanced channel mobility (Chen et al., 2018) and an increase in Microcodium abundance and export to the oceans (Prieur et al., 2024). Together, these records point to a marked intensification of erosion and sediment transfer, consistent with our interpretation of increased weathering fluxes. We will integrate these references explicitly in the revised text to make the connection between the isotopic evidence and sedimentological records clearer.
  
  Kaolinite abundance and secondary clay formation
  
  We acknowledge the reviewer’s point that kaolinite abundance alone cannot serve as a straightforward proxy for enhanced secondary clay formation. Kaolinite enrichment could, in principle, result from processes such as the erosion and redeposition of pre-PETM clays. While we discuss this limitation later in the manuscript, we emphasize that with the currently available mineralogical data, it is not possible to unequivocally distinguish between neoformed clays and reworked/pre-PETM clays.
  
  Nonetheless, the positive δ⁷Li excursion observed in our dataset suggests an overall increase in clay formation during the PETM. In this context, the kaolinite data remain consistent with such an interpretation, especially when viewed together with the isotopic evidence. Importantly, global mass-balance calculations indicate that the magnitude of the seawater δ⁷Li excursion during the PETM cannot be explained solely by erosion or recycling of previously formed clays; rather, it requires enhanced formation of new secondary clays (Pogge von Strandmann et al., 2021). This supports our interpretation that the observed kaolinite increase reflects intensified continental weathering and clay neoformation, even though kaolinite alone does not capture the full spectrum of clay mineral phases involved.
  
  Lithium isotope fractionation and mineral dependence
  
  We thank the reviewer for this important observation. Indeed, Li isotope fractionation could be mineral-dependent, which may affect the interpretation of δ⁷Li variations. Since we already present clay mineralogy data, we agree that explicitly discussing how variations in mineral assemblages could influence the fractionation factor between water and clays will strengthen our interpretation. In the revised manuscript, we will add a discussion of the potential role of mineralogy in influencing δ⁷Li values, while noting that the consistent trends in δ⁷Li values across sections suggest that mineral assemblage changes alone cannot fully explain the observed excursion.
  
  Marine authigenic clay contribution
  
  The reviewer raises an important question regarding the possible role of marine authigenic alumino-silicate clays. Based on the coastal but dominantly continental depositional setting of the Rin section, the formation of authigenic clays is possible but unlikely to have been significant. Authigenic clay precipitation typically occurs in deeper marine settings where prolonged water–sediment interaction facilitates diagenetic mineral growth. In contrast, the shallow-water depositional environments of our studied sections are not conducive to substantial authigenic clay formation. Additionally, even if authigenic clay formation occurred, its abundance would be minimal relative to the large detrital clay input in the near-shore environment.
  
  We thank Reviewer 1 again for the detailed and constructive feedback. We will incorporate the suggested clarifications and additional discussions into the revised manuscript, which we are confident will improve its clarity and robustness.
  
  Citation: https://doi.org/10.5194/egusphere-2025-2619-AC1
RC2:
'Comment on egusphere-2025-2619', Anonymous Referee #2, 16 Aug 2025
General comments:
This manuscript reports new geochemical (δ⁷Li, εNd, δ¹³C) and mineralogical data on two well-preserved Palaeocene-Eocene sedimentary floodplain sections in the Pyrenees. The objective is to reconstruct the regional changes in chemical weathering and physical erosion during the PETM warming event and the aftermath to characterize the response of the Earth system to warming events. The authors found a positive δ⁷Li excursion in the clay fraction of both sections during the main body of the PETM. They interpret these results as reflecting a decrease of the weathering intensity (higher chemical erosion and even higher physical erosion) during the PETM because of the intensification of the hydrological cycle and a more extensive clay formation in the floodplains.
Overall, this is a neat study and a valuable scientific contribution to the research field on the PETM. It is well written, the data are of high quality, and the interpretation and arguments are convincing. There are only a few aspects of the manuscript that should be improved, in particular the presentation of the interpretative framework and the implications, before final acceptance. My recommendation is publication after minor revisions. The main revisions I suggest are:
Clarify the interpretative framework of Li isotopes in detrital sediments (section 1.2). In my opinion, some statements in this section are not in accordance with results from published studies (see more details below).

Discuss in more details the comparison and implications with other Li isotopes PETM records. I suggest moving the paragraph lines 464-473 after discussing the results from the Pyrenees and modifying it to compare directly the results from various records and places. Why a positive excursion in the Pyrenees and a negative excursion in other settings? Is it because of the different geomorphic environment (deep regolith and transport-limited weathering in the pyrenees)? How does it compare with the other studied floodplain section, in the Bigorn basin (Ramos et al., 2022)?

Discuss in more detail the reasons for the very low δ⁷Li values in the Esplugafreda section during the recovery period. This does not appear to be a simple return to initial conditions, but rather a further increase in weathering intensity (lower δ⁷Li) associated with regolith deepening and soil shielding relative to pre-PETM conditions. If this is the case, what are the implications for CO₂ removal through silicate weathering, given that such highly weathered settings are characterized by a weak weathering response and therefore act as inefficient sinks for atmospheric CO₂ (Penman et al., 2020)? The timescale of the PETM recovery and the role of silicate weathering remain debated, and this study could provide useful new constraints.

Add a figure with the average values (δ⁷Li, εNd, δ¹³C, mineralogy) during each period (pre, POE, onset, body and recovery) for both sections (on the same figure). This would really help the reader to have a global overview of the main results and evolution through time.

In addition, the potential influence of marine clay formation (reverse weathering) on Li isotopes is not mentioned or discussed. Do you have any evidence to dismiss it for the Rin section? The study from Zhang et al., (2022) on the Ainsa paleo-delta shows that marine clay formation results in lowering of the δ⁷Li of sediments.
Specific comments:
- Line 111: define « weathering efficiency ». Note that this hypothesis of maximum weathering rate at moderate erosion rate (the “speed limit”) proposed by some authors (Dixon and von Blanckenburg, 2012; Gabet and Mudd, 2009) has been challenged by others (e.g. Larsen et al., 2014; West, 2012).
- Lines 139-145: This does not appear to be consistent with findings reported in previous studies. At high W/D both clay formation and clay dissolution processes are taking place, either in different part of the weathering profile (top regolith vs deep regolith; e.g. Chapela Lara et al., 2022; Clergue et al., 2015) or different part of the catchment (e.g. see figure 10 in Dellinger et al., 2015 ; figure 3 in Henchiri et al., 2016; Fries et al., 2019). Therefore, at high W/D, rivers do transport modern neoformed clays from weathering profiles, and hence there is NO evidence for “minimal clay neoformation” (on the contrary).
- Lines 150-154: what is the evidence for “fewer of the coarser-grained primary minerals carried in rivers are expected to be transported into offshore sites, the clay weathering signal may generally be recorded more clearly in marine sites”? I see several problems here:
First, the Dellinger et al., 2017 relationship has been observed for fine sediments (< 63 microns) not “coarse-grained primary minerals”.
Second, several studies on the Yangtze estuary (Yang et al., 2021, 2025) show the opposite sediment transport process to the one suggested is suggested by the authors, i.e. preferential transport of coarse-grained primary minerals offshore relative to clay minerals (“the offshore transport of SPM in the Changjiang Estuary may result in the preferential flocculation and deposition of clay minerals during the flooding season, while primary minerals or other fine-grained particles tend to be resuspended and carried seaward by currents” (Yang et al., 2021)).
Third, even if there are fewer primary minerals in the <2 μm fraction relative to the <63 μm fraction, primary clays and other minerals (feldspar, micas) are still present in the <2 μm fraction (e.g. Liu et al., 2025)
I suggest revision of the presented interpretation framework (Fig. 2) in accordance with existing publications.
- Section 4.1: is there any correlation between δ⁷Li and the mineralogy of clays? I think this should be discussed somewhere in the manuscript since different clays could have distinct fractionation factor during process of Li incorporation or adsorption into clays.
- Section 4.3: were the Li concentration measured on those samples? Any weathering-related changes in Li/Ti or Li/Al in both sections?
- Lines 494-495: see also all the studies that report increase dissolved Li isotope composition and clay formation in rivers when crossing large floodplains (e.g. Bagard et al., 2015; Dellinger et al., 2015; Maffre et al., 2020; Pogge von Strandmann et al., 2017; Pogge von Strandmann and Henderson, 2015). The proposed interpretation here, i.e. “the shift towards increased incongruent weathering, characterized by enhanced clay formation in the floodplain deposits” is consistent with all these studies on modern rivers with floodplains.
- Lines 497-499: see also the study from Xu et al., (2021)
- Lies 502-504: This is not clear to me, why faster runoff results in a positive δ⁷Li excursion in the clays?
- Figure 2 & 3: could be combined (panel A and Panel B)
- Figure 4: I suggest indicating the different periods (pre, POE, onset, body and recovery) on the right of the figure to help the reader not so familiar with the PETM timing and evolution.
References:
Bagard, M.-L., West, A.J., Newman, K., Basu, A.R., 2015. Lithium isotope fractionation in the Ganges–Brahmaputra floodplain and implications for groundwater impact on seawater isotopic composition. Earth and Planetary Science Letters 432, 404–414. https://doi.org/10.1016/j.epsl.2015.08.036
Chapela Lara, M., Buss, H.L., Henehan, M.J., Schuessler, J.A., McDowell, W.H., 2022. Secondary Minerals Drive Extreme Lithium Isotope Fractionation During Tropical Weathering. Journal of Geophysical Research: Earth Surface 127, e2021JF006366. https://doi.org/10.1029/2021JF006366
Clergue, C., Dellinger, M., Buss, H.L., Gaillardet, J., Benedetti, M.F., Dessert, C., 2015. Influence of atmospheric deposits and secondary minerals on Li isotopes budget in a highly weathered catchment, Guadeloupe (Lesser Antilles). Chemical Geology 414, 28–41. https://doi.org/10.1016/j.chemgeo.2015.08.015
Dellinger, M., Gaillardet, J., Bouchez, J., Calmels, D., Louvat, P., Dosseto, A., Gorge, C., Alanoca, L., Maurice, L., 2015. Riverine Li isotope fractionation in the Amazon River basin controlled by the weathering regimes. Geochimica et Cosmochimica Acta 164, 71–93. https://doi.org/10.1016/j.gca.2015.04.042
Dixon, J.L., von Blanckenburg, F., 2012. Soils as pacemakers and limiters of global silicate weathering. Comptes Rendus Geoscience 344, 597–609.
Fries, D.M., James, R.H., Dessert, C., Bouchez, J., Beaumais, A., Pearce, C.R., 2019. The response of Li and Mg isotopes to rain events in a highly-weathered catchment. Chemical Geology 519, 68–82. https://doi.org/10.1016/j.chemgeo.2019.04.023
Gabet, E.J., Mudd, S.M., 2009. A theoretical model coupling chemical weathering rates with denudation rates. Geology 37, 151–154.
Henchiri, S., Gaillardet, J., Dellinger, M., Bouchez, J., Spencer, R.G.M., 2016. Riverine dissolved lithium isotopic signatures in low-relief central Africa and their link to weathering regimes. Geophys. Res. Lett. 43, 2016GL067711. https://doi.org/10.1002/2016GL067711
Larsen, I.J., Almond, P.C., Eger, A., Stone, J.O., Montgomery, D.R., Malcolm, B., 2014. Rapid soil production and weathering in the Southern Alps, New Zealand. Science 343, 637–640.
Liu, Y., Yang, Y., Yan, Z., Jin, Z., Ye, C., Pogge von Strandmann, P.A.E., Deng, L., Liu, X., Fang, X., 2025. Lithium isotopes as a chemical weathering proxy in lacustrine sediments: Implications from multiphase leaching analyses. Global and Planetary Change 253, 104986. https://doi.org/10.1016/j.gloplacha.2025.104986
Maffre, P., Goddéris, Y., Vigier, N., Moquet, J.-S., Carretier, S., 2020. Modelling the riverine δ7Li variability throughout the Amazon Basin. Chemical Geology 532, 119336. https://doi.org/10.1016/j.chemgeo.2019.119336
Pogge von Strandmann, P.A.E., Frings, P.J., Murphy, M.J., 2017. Lithium isotope behaviour during weathering in the Ganges Alluvial Plain. Geochimica et Cosmochimica Acta 198, 17–31. https://doi.org/10.1016/j.gca.2016.11.017
Pogge von Strandmann, P.A.P., Henderson, G.M., 2015. The Li isotope response to mountain uplift. Geology 43, 67–70.
Ramos, E.J., Breecker, D.O., Barnes, J.D., Li, F., Gingerich, P.D., Loewy, S.L., Satkoski, A.M., Baczynski, A.A., Wing, S.L., Miller, N.R., Lassiter, J.C., 2022. Swift Weathering Response on Floodplains During the Paleocene-Eocene Thermal Maximum. Geophysical Research Letters 49, e2021GL097436. https://doi.org/10.1029/2021GL097436
West, A.J., 2012. Thickness of the chemical weathering zone and implications for erosional and climatic drivers of weathering and for carbon-cycle feedbacks. Geology 40, 811–814. https://doi.org/10.1130/G33041.1
Xu, Z., Li, T., Li, G., Hedding, D.W., Wang, Y., Gou, L.-F., Zhao, L., Chen, J., 2021. Lithium isotopic composition of soil pore water: Responses to evapotranspiration. Geology. https://doi.org/10.1130/G49366.1
Yang, C., Cao, F., Xu, J., Lu, Y., Bi, L., Zheng, H., Yang, S., 2025. Lithium isotopic constraints on systematic biases in reconstructing continental weathering processes from bulk sedimentary records at continental margins. Global and Planetary Change 253, 104942. https://doi.org/10.1016/j.gloplacha.2025.104942
Yang, Vigier, N., E. Lian, Z. Lai, S. Yang, 2021. Decoupling of dissolved and particulate Li isotopes during estuarine processes. Geochemical Perspectives Letters 19, 40–44. https://doi.org/10.7185/geochemlet.2133
Zhang, X. (Yvon), Gaillardet, J., Barrier, L., Bouchez, J., 2022. Li and Si isotopes reveal authigenic clay formation in a palaeo-delta. Earth and Planetary Science Letters 578, 117339. https://doi.org/10.1016/j.epsl.2021.117339
Citation: https://doi.org/10.5194/egusphere-2025-2619-RC2
- AC2:
  'Reply on RC2', Rocio Jaimes-Gutierrez, 08 Sep 2025
  We thank Reviewer 2 for the constructive and positive evaluation of our manuscript, and for the detailed comments and suggestions. We are pleased that the reviewer finds the study valuable and the dataset of high quality. Below, we provide a point-by-point response to each major comment. We will revise the manuscript accordingly in the next stage.
  
  1. Clarify the interpretative framework of Li isotopes in detrital sediments
  We thank the reviewer for highlighting the importance of clarifying the Li isotope interpretation framework. We will revise Section 1.2 to provide a clearer and more nuanced description of the Li isotope framework. Specifically, we will:
  Explicitly explain that at high W/D both clay neoformation and dissolution can occur at different depths in the profile or in different parts of the catchment (Chapela Lara et al., 2022; Clergue et al., 2015; Dellinger et al., 2015; Henchiri et al., 2016; Fries et al., 2019).
  
  Rephrase the current statement on “minimal clay neoformation” to emphasize that modern rivers can transport significant amounts of neoformed clays.
  
  2. Discuss more thoroughly the comparison and implications with other PETM Li isotope records. Why positive excursion in the Pyrenees vs. negative elsewhere?
  We agree with the reviewer and will explore the mechanisms that could have resulted in a different excursion, linking the importance of the climatic setting and the starting weathering regime to the W/D evolution during a warming event such as the PETM. We will follow the presentation of the Pyrenean results and expand it into a comparative discussion. In particular, we will contrast our positive excursion with negative excursions reported elsewhere, highlight the geomorphic and climatic context, and integrate a discussion, e.g., Pogge von Strandmann et al. (2021), Ramos et al. (2022), Chen et al. (2023), Jones et al. (2023).
  
  3. Discuss in more detail the low δ⁷Li values in Esplugafreda during recovery. Could indicate further increase in weathering intensity and inefficient CO₂ sink behavior?
  We appreciate this suggestion and will explore the recovery dynamics. We will expand the discussion on the Esplugafreda recovery values to emphasize that they likely reflect deeper regolith development and enhanced soil shielding compared to syn-PETM conditions. This perspective adds an important nuance to the PETM recovery debate, including the CO₂ budgets across the PETM.
  4. Add a figure summarizing average values (δ⁷Li, εNd, δ¹³C, mineralogy) for each period.
  We agree that such a summary figure will greatly help readers. We will add a new figure showing average values for the five intervals (pre-PETM, POE, onset, body, recovery) for both sections.
  
  5. Influence of marine clay formation (reverse weathering) is not discussed. Could this affect Rin section?
  We thank the reviewer for raising this important point, which connects to Reviewer 1’s fourth comment on the potential role of marine authigenic clays. Based on the coastal but dominantly continental depositional setting of the Rin section, the formation of authigenic clays is possible but unlikely to have been significant. We will add a statement clarifying its setting and briefly discussing why reverse weathering is unlikely here. Furthermore, even if authigenic clay formation occurred, its abundance would be minimal relative to the large detrital clay input in the near-shore environment.
  
  We thank Reviewer 2 again for the thorough and thoughtful review. We will further apply the minor corrections proposed during the review process. We are confident that addressing these points will significantly improve the clarity and impact of our manuscript.
  
  Citation: https://doi.org/10.5194/egusphere-2025-2619-AC2

Peer review completion

AR – Author's response | RR – Referee report | ED – Editor decision | EF – Editorial file upload

ED: Reconsider after major revisions (18 Sep 2025) by Shiling Yang

AR by Rocio Jaimes-Gutierrez on behalf of the Authors (12 Jan 2026) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (21 Jan 2026) by Shiling Yang

RR by Anonymous Referee #1 (05 Feb 2026)

Suggestions for revision or reasons for rejection

After carefully reading the response document from the authors, which answers my previous question, I found it generally solved most of my questions. One thing that I am still not fully convinced about is the contribution from marine authigenic alumino-silicate clays (MAACs), which is declared to be negligible to the bulk sediments. The authors suggest that MAAC formation is unlikely to happen in a coastal setting. However, researches have shown that MAAC formation predominantly happens in coastal settings, where supply of terrestrial Al- and Fe-bearing detritus is sufficient (Geilert et al., 2023; Tréguer et al., 2021). In my opinion, one argument that the authors could probably make is that although MAAC formation might been intensive in coastal setting, it is often masked by the large amount of terrestrial detrital, resulting in a contribution of less than 2% (mass fraction) to the bulk sediments (Bernhardt et al., 2020; Presti and Michalopoulos, 2008). Based on this, for example, the author could also do a mass-balance estimate, assuming a range of MAAC δ7Li, and times it with 2% (or some similar values), to quantify the potential influence of MAAC on the bulk sediment δ7Li. Another line of evidence that might help is from Trapp-Müller et al. (2025), who suggested that MAAC formation is unlikely to happen in coastal settings under low continental weathering intensity, due to the delivery of cation-rich terrestrial materials, rather than cation-poor ones.

Also to mention is the observed increase in kaolinite abundance of the Rin section.
Note that two plausible explanations have been listed. If the former is the case, then it seems to contradict the interpretation of a declined weathering intensity.

Some minor issues:

Line 263 and 264, the unit of 0.02 and 0.5-1.2 should be “°” and “°/min”

Line 270, a typo in “the”

Line 276, “2” in CO2 should be a subscript.

Line 391, I think it should be dashed lines in panel A, not “grey bars”

Line 540, the citation should be in parentheses.

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ED: Publish subject to minor revisions (review by editor) (06 Feb 2026) by Shiling Yang

AR by Rocio Jaimes-Gutierrez on behalf of the Authors (16 Feb 2026) Author's response Author's tracked changes Manuscript

ED: Publish as is (25 Feb 2026) by Shiling Yang

AR by Rocio Jaimes-Gutierrez on behalf of the Authors (27 Feb 2026) Manuscript

Journal article(s) based on this preprint

31 Mar 2026

Silicate weathering in the semi-arid Southern Pyrenees during the PETM: lithium isotope evidence

Rocio Jaimes-Gutierrez, Marine Prieur, David J. Wilson, Philip A. E. Pogge von Strandmann, Emmanuelle Pucéat, Thierry Adatte, Jorge E. Spangenberg, and Sébastien Castelltort

Clim. Past, 22, 709–727, https://doi.org/10.5194/cp-22-709-2026,https://doi.org/10.5194/cp-22-709-2026, 2026

Short summary

Rocio Jaimes-Gutierrez, Marine Prieur, David J. Wilson, Philip A. E. Pogge von Strandmann, Emmanuelle Pucéat, Thierry Adatte, Jorge E. Spangenberg, and Sébastien Castelltort

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https://doi.org/10.5194/egusphere-2025-2619-supplement

Rocio Jaimes-Gutierrez, Marine Prieur, David J. Wilson, Philip A. E. Pogge von Strandmann, Emmanuelle Pucéat, Thierry Adatte, Jorge E. Spangenberg, and Sébastien Castelltort

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This study examines how weathering in the Southern Pyrenees responded to a significant global warming event that occurred 56 million years ago. We found that changes in rainfall and erosion significantly influenced how minerals break down, and that the weathering response evolved from the continental interior to the marine environment. These results highlight regional variations in Earth's surface response to climatic perturbations and the processes at play in response to global warming.


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