Luminescence Dating Reveals Multiple Late Quaternary Eruptions at the Soda Lake Volcanic Center, Nevada

Rodrigues, Kathleen; Ruprecht, Philipp P.; de Polo, Craig M.

doi:10.5194/egusphere-2026-4195

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https://doi.org/10.5194/egusphere-2026-4195

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17 Aug 2026

| 17 Aug 2026

Luminescence Dating Reveals Multiple Late Quaternary Eruptions at the Soda Lake Volcanic Center, Nevada

Kathleen Rodrigues, Philipp P. Ruprecht, and Craig M. de Polo

Abstract. The Soda Lake volcanic center in western Nevada is the youngest known volcanic system in the state, yet its eruptive history remains poorly constrained because of conflicting stratigraphic interpretations and the limitations of conventional radiometric dating in young mafic volcanic terrains. Here we apply post-infrared infrared stimulated luminescence (post-IRIR) dating to potassium-rich feldspar separates extracted from volcaniclastic sediments and plagioclase phenocrysts extracted from juvenile basalt bombs to directly constrain the timing of eruptive activity using two distinct luminescence resetting pathways: complex eruption- and transport-related resetting of volcaniclastic grains (including variable thermal, optical, and mechanical resetting) and thermal resetting of feldspar phenocrysts within basalt bombs. Single-grain post-IRIR measurements of surge and reworked volcaniclastic deposits indicate eruptions at ~5.5 ka and ~12.5 ka. The ~5.5 ka eruption is further corroborated by plagioclase phenocrysts extracted from basalt bombs associated with the youngest eruptive phase, which yielded statistically indistinguishable ages. Despite contrasting depositional histories and luminescence resetting mechanisms, ages derived from sedimentary and bomb-derived materials are internally consistent, demonstrating that reliable eruption chronologies can be established from multiple components of a volcanic system. More broadly, the results demonstrate that eruption-related luminescence resetting may be preserved in juvenile phenocrysts, volcaniclastic sediments, and potentially xenocrystic materials, substantially expanding the range of datable components available in young mafic volcanic systems. These results resolve long-standing uncertainties regarding the eruptive history of the Soda Lake volcanic center and demonstrate the broader potential of luminescence dating for directly constraining young basaltic volcanism in settings where conventional geochronologic methods are ineffective.

Received: 13 Jul 2026 – Discussion started: 17 Aug 2026

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Kathleen Rodrigues, Philipp P. Ruprecht, and Craig M. de Polo

Status: final response (author comments only)

RC1:
'Comment on egusphere-2026-4195', Joseph Colgan, 09 Sep 2026

Overall I found this manuscript to be generally well written and illustrated. Not being an expert in luminescence dating, I was more interested in the new ages and their regional context, and have a couple minor suggestions for improving that aspect of the paper.
The manuscript alludes to “a broader province of late Quaternary basaltic volcanism” and “numerous small basaltic volcanic centers… throughout western Nevada” (lines 98-100) but doesn’t say much about them or where they are. Instead of the small location map inset into Figure 1, I suggest making a new regional map figure large enough to show the outline of the Basin and Range, the Walker Lane, the major Quaternary basaltic volcanic centers (perhaps colored by age?), and other geographic features mentioned in the text. Then make the current Figure 1 into Figure 2.
Along with the map figure, you could add a paragraph describing how the Soda Lake system relates (or doesn’t) to these other volcanic centers. Quaternary is a broad age range – where are the other very young centers? How do these compare to older things like Buffalo Valley or Lunar Craters, or to young centers in the eastern Sierra? Are there time-space progressions evident? What gaps do these new ages fill in? This wouldn’t add much to the length, while making the paper more appealing to readers interested mainly in the new age data rather than the methodology.

There is some discussion of this in section 6.4, but it seems to come out of nowhere without any prior context---where are Upsal Hogback and similar centers on a map? Where is this study area relative to the Walker Lane? What is the Isabella anomaly and where is it? And so forth.
Few other minor things:

Line 25: The paper opens with the line “The Soda Lake volcanic center in western Nevada provides an ideal setting in which to evaluate these approaches.” This reads like the opening of a second paragraph, with the first one missing. Whatever needs to be done to fix this.

Line 183: What “potassium-rich feldspars” did you isolate from the sediments, and what was their source? Basalt seems an unlikely source for K-feldspar - are these from some other detrital or volcanic source?

Figure 1: Could this be made an actual geologic map with units instead of notes on a lidar base? That would make it more informative, but if the mapping hasn’t been done there’s not much to add.

Figure 2: Suggest using simpler numbers on the Y axis, like every 0 and 5 instead of 2 and 7, would make it easier to see the relative thickness of the different units. Could also note on Figure 1 where photos A and B were taken?

Citation: https://doi.org/10.5194/egusphere-2026-4195-RC1
- AC1: 'Reply on RC1', Kathleen Rodrigues, 22 Oct 2026
  
  We thank the reviewer for their thoughtful and constructive comments. We agree that additional regional context would strengthen the manuscript, particularly for readers interested in the implications of the new eruption ages rather than the luminescence methodology itself. We have made several revisions to address these suggestions, as detailed below.
  Regional volcanic context and mapping:
  We agree that the original manuscript did not adequately establish the regional volcanic context of the Soda Lake volcanic center. To address this, we have added a new regional map showing the location of Soda Lake relative to the Walker Lane, the Basin and Range Province, and other Quaternary volcanic fields in western Nevada and the eastern Sierra Nevada. The original Figure 1 has been renumbered accordingly.
  We have also expanded the regional geological background and discussion to better contextualize the new eruption ages. In particular, we now discuss the spatial distribution and eruptive histories of nearby volcanic fields, including the Lahontan Valley, Western Nevada, Lunar Crater, and other relevant volcanic fields. These additions provide a clearer framework for comparing Soda Lake with other Quaternary volcanic centers and evaluating the significance of its late Pleistocene and Holocene activity.
  We have also revised Section 6.4 to better connect the discussion of regional volcanism to the geological background presented earlier in the manuscript.
  Opening sentence in the Introduction:
  We agree that the original opening was somewhat abrupt and did not sufficiently introduce the broader motivation for the study. We have revised the opening of the manuscript to better establish the importance of constraining the timing of young volcanic activity and the role of luminescence dating in addressing this problem before introducing Soda Lake as a case study.
  Source of potassium-rich feldspars:
  We agree that basalt is not a likely source of K-feldspar. The potassium-rich feldspars analyzed in this study were isolated from the sedimentary deposits rather than the basaltic eruptive material. Their mineralogical composition was confirmed using scanning electron microscopy with energy-dispersive X-ray spectroscopy. We have clarified this distinction in the revised methods section. Although we cannot definitively establish their provenance, they likely reflect detrital contributions from surrounding lithologies rather than the basaltic volcanic products themselves.
  Figure 1 (now Figure 2) - LiDAR map:
  We appreciate this suggestion and agree that a detailed geologic map would provide additional context. However, a sufficiently detailed geologic map distinguishing the relevant eruptive units is not currently available. We have therefore retained the LiDAR-based map, which allows the volcanic landforms and sampling locations to be clearly identified without implying a level of geological mapping detail that is not presently supported.
  Figure 2 (now Figure 3) - Elevation scale and photograph locations:
  We have revised the vertical-axis labeling to use more intuitive increments, making the relative thicknesses of the stratigraphic units easier to interpret. We have also included information about the approximate locations of the photographs to the figure caption.
  
  Citation: https://doi.org/10.5194/egusphere-2026-4195-AC1
RC2:
'Comment on egusphere-2026-4195', Christoph Schmidt, 10 Sep 2026
Rodrigues et al. present new luminescence ages for Big Soda Lake (USA), derived from different materials (volcaniclastic sediments and phenocrysts in basaltic bombs) associated with different signal-resetting mechanisms. As chronometric data for this volcanic field are scarce, these new results are a welcome contribution both to understanding the volcanic setting and associated hazards and to advancing luminescence dating of young (Late Pleistocene) volcanic eruptions that are otherwise difficult to constrain using other chronometric methods.
The manuscript is well written and easy to follow, and the methodology and results appear robust. In particular, the agreement between sediment and bomb ages is encouraging and supports the chosen approach. The findings are presented clearly, and the conclusions are well supported by the data.
I therefore support publication of this study in GChron following the minor revisions outlined below.
Equivalent dose measurement: I was wondering why the pIRIR225 signal was used for the plagioclase phenocrysts from the basaltic bombs instead of the pIRIR290 signal which is supposed to be more stable (less fading), especially since the generally limiting factor of poor optical resetting for using this signal do not apply here. It would be good if a sentence was added explaining the rational for the choice of this luminescence signal. Another point concerns the determination of the sigma_b value that is crucial in the application of the Minimum Age Model (MAM). The manuscript does currently not contain any information on how the values chosen (0.15) was obtained or from which previous study it was adopted. A related issue is the general validity of single grain data using the MAM in the potential presence of beta dose rate non-uniformity, which adds overdispersion to the De data. As it is not straightforward to test the sampled materials for beta hotspots, it would be sufficient to briefly discuss this topic and potential impacts on dose rate and age calculations.

Dose rate assessment: The manuscript would benefit from a more detailed explanation of dose rate assessment. For instance, how was the shape of the bombs taken into account for gamma dose rate scaling? How exactly was the size of K-feldspar grains in the matrix determined and what were the results (could be presented in the supplement)? A close-up of the analysed rock surface (or thin section) would be helpful to assess the microdosimetric situation.

Age calculation: Was a specific program used for age calculation? If yes, which one? How were uncertainties propagated?

Raw data: For the raw data upon which this study is based I would encourage the authors to provide the De values obtained for each sample in another format than xlsx that is more universally reabable (e.g. csv) and to provide enough metadata to understand the data. Currently, no units are given for the De values. Ideally, they would add the .seq and .bin files in the Zenodo repository so that everyone can have a look at the decay curves and repeat the analysis, thus supporting reproducibility.

Specific comments
Abstract
Please add in the abstract how many samples of each context (volcaniclastic, bomb) you dated.
Bibliography
I detected some slight inconsistencies in the bibliography (for example, the journal is missing for the reference Madeira et al. 1995); please check.
l. 87
Can you provide a reference (or some) for this statement (“uncertainties on the order of the eruption ages themselves“)?
l. 164
Please use metric units.
l. 183
A word seems to be missing at the end of the sentence (I guess “fraction”).
l. 197
Please check if the given power density of the IR laser is correct; it sounds pretty low, as the maximum power density is supposed to be in the order of 500 W/cm2.
l. 198
I would prefer the term “resetting” here over “bleaching” as you are looking at a variety of signal resetting mechanisms for the sediment samples.
l. 209
See comment above, replace “bleaching” by “resetting”. See also lines 224
l. 225
Which sigma_b values was used and how was it determined? Table 1 lists a sigma_b value of 0.15 but without further reference and information how it was derived.
l. 227
For complete signal resetting and scatter deriving only from dose rate heterogeneities, it has been shown that the Average Dose Model (ADM; Guérin et al., 2017) provides more accurate results. It would be interesting here to compare the CAM and ADM results.
l. 238
Maybe the wrong citation is included here. Guérin et al. (2011), as cited in the bibliography, contains the updated conversion factors, while Guérin et al. (2012) presents grain-size attenuation factors. Please also correct in the supplement.
l. 249
Does it make sense to assume a negative water content (within uncertainties)? Consider using asymmetric uncertainty ranges, e.g. 1 - 1, + 5 % or adjust calculations accordingly.
l. 250
Was erosion considered in the cosmic dose rate calculations?
l. 255
Which doses were administered for the DRT? Was any residual subtracted (does probably not make a difference but should be mentioned).
l. 256
A light exposure of 24 h to determine residual signals somehow became the standard but it may not reflect the actual exposure conditions of the volcaniclastic sediments dated here. Do you have an estimate on how long sunlight exposure lasted for these sediments? Would a residual dose measurement with a shorter bleaching duration – potentially yielding higher residual doses – inform on whether the signal in the grains was reset rather thermally or by stress instead of by light exposure?
l. 320
The agreement between sediment and bomb ages is highly encouraging and you mention here that the bomb sample produced very narrow De distributions. The latter has to be seen in the light of aliquot size, i.e. single grains (sediment) vs. small aliquots (bomb). The averaging effect for small aliquots might not be massive but could have nonetheless contributed to the observed shape of the De distribution. I think this is worth mentioning in the discussion.
l. 358
I would slightly rephrase “are comparatively insensitive to incomplete bleaching effects”, as bleaching (light exposure) should not play a role for the samples extracted from the interior of the bombs (as long as no post-depositional bleaching has occurred).
l. 364
As this paragraph is about the role of stress in resetting luminescence signals, it might be worth discussing the findings by Preusser et al. (2011) already here. Consider also including Rufer et al. (2014) here or later as they also obtained ages on phreatomagmatic deposits.
l. 456
Why “interpretation”?
Caption to Fig. 2
The description of panel (B) is a bit ambiguous concerning the depth information given (6 m vs. 7 m). Please clarify and rephrase.
Fig. 3
Please add the natural signal in the dose response plots to assess how non-linear dose response is at the natural dose.
Fig. 4
It is very conservative here to indicate the age bounds of the younger eruption as the envelope of uncertainties of all four ages for this eruption. You might consider testing whether these four ages derive from a common statistical distribution, in which case calculating the weighted average would be justified, reducing the overall age uncertainty.
Fig. 5
There is a typo in this figure (“colision”).

References
Guérin, G., Mercier, N., Nathan, R., Adamiec, G., Lefrais, Y., 2012. On the use of the infinite matrix assumption and associated concepts: A critical review. Radiation Measurements 47, 778-785.
Guérin, G., Christophe, C., Philippe, A., Murray, A.S., Thomsen, K.J., Tribolo, C., Urbanova, P., Jain, M., Guibert, P., Mercier, N., Kreutzer, S., Lahaye, C., 2017. Absorbed dose, equivalent dose, measured dose rates, and implications for OSL age estimates: Introducing the Average Dose Model. Quaternary Geochronology 41, 163-173.
Rufer, D., Preusser, F., Schreurs, G., Gnos, E., Berger, A., 2014. Late Quaternary history of the Vakinankaratra volcanic field (central Madagascar): insights from luminescence dating of phreatomagmatic eruption deposits. Bulletin of Volcanology 76, 817.
Citation: https://doi.org/10.5194/egusphere-2026-4195-RC2
- AC2: 'Reply on RC2', Kathleen Rodrigues, 22 Oct 2026
  
  We thank the reviewer for their thoughtful and constructive assessment of our manuscript and for recognizing the significance of the new luminescence ages for constraining the eruptive history of the Soda Lake volcanic center. We appreciate the detailed methodological suggestions, which have helped us identify several areas where additional clarification and discussion will improve the manuscript. We have addressed the comments individually below.
  Comment: Why was pIRIR225 used instead of pIRIR290 for the plagioclase phenocrysts?
  Response: We thank the reviewer for raising this question. We initially investigated the suitability of a pIRIR290 protocol for the plagioclase phenocrysts extracted from the basaltic bombs. However, preliminary measurements showed that the luminescence signal measured at 290 °C was nearly absent, preventing reliable equivalent-dose determination. In contrast, the pIRIR225 protocol produced measurable signals suitable for constructing dose-response curves and determining equivalent doses. Although higher temperature post-IR IRSL measurements are generally associated with improved signal stability and reduced anomalous fading in K-feldspar, these advantages do not necessarily extend to the calcic plagioclase investigated here. In particular, the increase in IRSL signal intensity sometimes observed at elevated stimulation temperatures in K-feldspar was not apparent in our plagioclase separates. We have added an explanation of the preliminary pIRIR290 measurements and the rationale for selecting pIRIR225 to the revised methods section.
  Comment: How was σb = 0.15 determined, and how sensitive are the MAM results to this parameter?
  Response: We agree that the selection of σb warrants additional explanation, particularly because it influences the equivalent doses obtained using the Minimum Age Model. To evaluate the sensitivity of our results to this parameter, we conducted an additional analysis in which σb was systematically varied between 0.10 and 0.20 for each of the three single-grain sediment samples (SLG001-SLG003). As expected, increasing σb resulted in systematically higher MAM-3 equivalent-dose estimates. Across the tested range, the equivalent doses increased from 18.5 to 19.6 Gy (+6%) for SLG001, from 17.8 to 20.4 Gy (+15%) for SLG002, and from 36.1 to 40.4 Gy (+12%) for SLG003. Importantly, the changes in equivalent dose over this range are comparable to the associated analytical uncertainties, and the 1σ uncertainty intervals overlap substantially. This indicates that, although the absolute equivalent dose estimates are sensitive to the assumed σb, moderate variations in this parameter do not produce clearly distinguishable estimates at the precision of the current measurements. We have added this sensitivity analysis to the supplementary material and expanded the methods section to explicitly discuss the choice of σb = 0.15 and its influence on the resulting equivalent doses.
  Comment: Potential effects of beta dose-rate heterogeneity on single-grain De distributions and MAM ages.
  Response: We agree that beta dose-rate heterogeneity represents an important consideration when interpreting single-grain equivalent dose distributions, particularly in volcaniclastic sediments containing mineral grains with differing radionuclide concentrations. Spatial variability in beta dose rates may introduce additional dispersion into the observed D_e distributions, even when luminescence signals have been completely reset before deposition. Consequently, some of the observed dispersion may reflect microdosimetric variability rather than incomplete signal resetting alone. This distinction is particularly relevant to the application of the MAM, which assumes that the lowest-dose population provides the most appropriate estimate of the burial dose. If some grains have experienced systematically lower beta dose rates than the bulk average, the MAM could preferentially select these grains, potentially leading to an underestimation of the burial age. We have expanded the discussion to acknowledge this potential source of dispersion and its implications for age determination. Although the available measurements do not permit a direct reconstruction of the beta dose rate distribution experienced by individual grains, we recognize that beta heterogeneity may contribute to the observed overdispersion and should be considered when interpreting the MAM-derived ages.
  Comment: How was the shape of the bombs taken into account for gamma dose-rate scaling?
  Response: The geometry of the basalt bombs was accounted for in the gamma dose rate calculations by approximating each bomb as a sphere, with the bomb interior and surrounding volcaniclastic sediments treated as separate materials characterized by their respective radionuclide concentrations and densities. This approach allowed us to account for gamma radiation originating within the bomb itself as well as contributions from the surrounding sediments, taking into consideration the finite dimensions of the bomb and the attenuation of gamma radiation with distance. The bombs selected for analysis were approximately 20 cm in diameter and exhibited relatively symmetrical shapes, making a spherical approximation reasonable. Furthermore, luminescence samples were extracted from the central portions of the bombs to minimize variability associated with irregularities in bomb shape and proximity to the bomb-sediment interface. We have clarified this approach in the revised manuscript.
  Comment: How was the size of K-feldspar grains in the matrix determined, and what were the results? Could a close-up or thin-section image be provided?
  Response: The K-feldspar grains used for luminescence dating were isolated from the volcaniclastic sediment matrix through wet sieving to obtain the 180-220 µm grain size fraction, followed by density separation to concentrate K-rich feldspar. The 180-220 µm range represents the grain-size fraction selected for luminescence analysis, rather than a quantitative characterization of the full grain size distribution of K-feldspar within the original volcaniclastic matrix. No systematic petrographic grain size measurements were undertaken on the intact matrix. If the comment instead refers to the plagioclase phenocrysts within the juvenile basalt bombs, their sizes were estimated through visual examination of the bomb material under an optical microscope, rather than from thin-section measurements. Although a close-up or thin-section image could provide additional petrographic context, we do not currently have a representative thin-section image documenting the plagioclase grain-sizes.
  Comment: Was a specific program used for age calculation? How were uncertainties propagated?
  Response: Luminescence ages and associated uncertainties were calculated using the Dose Rate and Age Calculator (DRAC; Durcan et al., 2015). Equivalent dose estimates and their associated uncertainties were combined with the calculated environmental dose rates to obtain uncorrected luminescence ages. We have clarified the age calculation procedures in the revised manuscript.
  Comment: Provide equivalent dose data in a more universally readable format, with units and metadata, and ideally include the original measurement files.
  Response: We have made the equivalent dose data available through a Zenodo repository. The dataset now includes equivalent dose measurements in CSV format, with clearly identified units and sample identifiers.
  Comment: Please specify the number of samples analyzed from each context.
  Response: We have revised the abstract to explicitly state that three volcaniclastic sediment samples and two basaltic bomb samples were analyzed.
  Comment: Minor inconsistencies in the references, including Madeira et al. (1995).
  Response: We have corrected the Madeira et al. (1995) reference and reviewed the bibliography for consistency and completeness.
  Comment: Provide references supporting the statement that chronological uncertainties can be on the order of the eruption ages themselves.
  Response: We have added citations to support this statement in the revised manuscript.
  Comment: Please use metric units.
  Response: Corrected as suggested.
  Comment: A word appears to be missing at the end of the sentence.
  Response: Thank you for identifying this typographical error. We have added the missing word ("fraction")
  Comment: Please verify the reported IR laser power density.
  Response: We have confirmed that the reported laser power is accurate.
  Comment: Use "resetting" rather than "bleaching" when discussing different signal resetting mechanisms.
  Response: We have replaced all instances of the word "bleaching" with the word "resetting" as requested.
  Comment: Consider comparing CAM and Average Dose Model (ADM; Guérin et al., 2017) results.
  
  Response: We have now evaluated equivalent dose distributions for the juvenile basalt bomb samples (SL004 and SL005) using both the Central Age Model (CAM; Galbraith et al., 1999) and the Average Dose Model (ADM; Guérin et al., 2017). Both models yielded statistically indistinguishable Dₑ estimates, however, the ADM produced smaller associated uncertainties and was therefore adopted for the final age calculations. We have updated the revised manuscript to describe this comparison and clarify our rationale for selecting the ADM. The reported Dₑ values and their uncertainties in Table 1 reflect the ADM results for both basalt bomb samples.
  Comment: Correct the references for conversion factors and grain size attenuation factors.
  Response: The references have been corrected throughout the manuscript.
  Comment: Reconsider the use of water content uncertainties that extend below zero.
  Response: We agree that moisture content uncertainties extending below 0% are not physically meaningful. The nominal moisture content of 1 ± 5% was selected to reflect the generally dry conditions of the volcaniclastic deposits while allowing for uncertainty in long-term burial conditions. Because the Dose Rate and Age Calculator (DRAC; Durcan et al., 2015) accommodates symmetric rather than asymmetric moisture content uncertainties, we evaluated the sensitivity of the calculated ages to a physically meaningful moisture content range of 0-6%, corresponding to the upper and lower bounds of our original estimate. This assessment indicated that accounting for the asymmetric moisture content range had a negligible influence on the resulting age uncertainties. We have therefore retained the original symmetric uncertainty in the DRAC calculations for consistency.
  Comment: Was erosion considered in the cosmic dose-rate calculations?
  
  Response: Erosion was not explicitly incorporated into the cosmic dose rate calculations because there is no geomorphic or stratigraphic evidence for significant erosion at the sampling locations since deposition. Cosmic dose rates were calculated using the present day sampling depths following Prescott and Hutton (1994), assuming that these depths reasonably approximate the average burial conditions over the depositional period. Although changes in overburden thickness could influence the time-averaged cosmic dose rate, cosmic radiation accounts for only approximately 3-6% of the total environmental dose rate for the investigated samples. Consequently, even moderate changes in burial depth would be expected to have a relatively limited influence on the calculated luminescence ages.
  
  Comment: What doses were administered during dose recovery testing, and were residual doses subtracted?
  
  Response: Dose recovery tests were conducted using an administered laboratory dose of 20 Gy, selected to approximate the natural Dₑ of the samples. The residual doses were relatively low, ranging from 0.3 to 0.6 Gy, and were not subtracted from the recovered doses. We have clarified this in the revised manuscript.
  
  Comment: Does the 24 hour sunlight exposure adequately represent natural resetting conditions? Could shorter duration experiments help distinguish resetting mechanisms?
  Response: We agree that 24 hours of exposure to a solar simulator does not necessarily reproduce the natural resetting conditions experienced by mineral grains during phreatomagmatic eruptions. The purpose of these experiments was to evaluate the residual dose remaining after prolonged light exposure and assess the potential for effective optical resetting of the post-IRIR150 signal, rather than to directly simulate conditions during eruption and deposition. In natural phreatomagmatic settings, grains may experience relatively brief and highly variable exposure to sunlight during eruption, transport, and deposition. Furthermore, dense pyroclastic surges and tephra clouds may substantially limit light penetration, while transient heating and mechanical processes may also contribute to signal resetting. Consequently, the 24 hour bleaching experiments should be considered an assessment of residual signal behavior under prolonged illumination rather than evidence that complete optical resetting occurred during the eruption. We agree that shorter duration bleaching experiments could provide valuable additional information about the optical resetting characteristics of these grains. However, such experiments alone would not necessarily allow us to distinguish optical resetting from thermally or mechanically induced resetting during an eruption. This would require additional controlled experiments that independently evaluate these processes.
  We have clarified the limitations of the laboratory bleaching experiments in the revised manuscript and acknowledge that further experimental work would be valuable for better understanding luminescence resetting mechanisms in phreatomagmatic environments.
  
  Comment: Narrower De distributions for bomb samples may partly reflect the averaging effects of small aliquot measurements relative to single grain analyses.
  
  Response: We agree with the reviewer. The relatively narrow equivalent dose distributions observed for the basaltic bomb samples are consistent with effective thermal resetting during eruption. However, because these measurements were performed on small aliquots rather than individual grains, averaging across multiple grains may also have contributed to the reduced dispersion. We have added this qualification to the discussion and have avoided interpreting the difference in dispersion between sediment and bomb samples as being attributable exclusively to differences in resetting efficiency.
  
  Comment: Rephrase the statement that bomb samples are insensitive to incomplete bleaching.
  Response: We agree that "bleaching" is not the appropriate terminology in this context. Because the analyzed phenocrysts were extracted from bomb interiors, their luminescence signals are expected to have been reset thermally during eruption rather than through exposure to sunlight.
  Comment: Discuss Preusser et al. (2011) and Rufer et al. (2014) in the context of mechanical resetting and luminescence dating of phreatomagmatic deposits.
  Response: We have incorporated the findings of Preusser et al. (2011) into the discussion of mechanical and stress-induced signal resetting and have added Rufer et al. (2014) to provide further context for the application of luminescence dating to phreatomagmatic eruption deposits.
  Comment: Why "interpretation"?
  Response: We agree that the wording was imprecise and have revised the sentence to distinguish more clearly between the measured chronological results and the geological conclusions drawn from them.
  Comment: Clarify the apparent discrepancy between the 6 m and 7 m depth information.
  Response: We have revised the figure caption to clarify the depth references and ensure that the stated measurements are consistent with the illustrated stratigraphic section.
  Comment: Add the natural luminescence signal to the dose response curves.
  Response: We have revised the figure to indicate the natural signal on the dose response curves.
  Comment: Consider testing whether the four ages associated with the younger eruption are statistically consistent and, if so, calculate a weighted mean age.
  Response: We have now evaluated the statistical consistency of the four fading-corrected luminescence ages associated with the youngest eruption (SL001, SL002, SL004, and SL005) using a chi-square test. The results indicate that the ages are statistically consistent with a common eruption age (χ² = 0.68, df = 3, p = 0.88). Given this agreement, we calculated an inverse-variance weighted mean, with individual ages weighted by the inverse square of their associated 1σ uncertainties. This yielded a weighted mean eruption age of 5.54 ± 0.23 ka (1σ). The reported uncertainty represents the formal standard error of the weighted mean, assuming independent age uncertainties. We have incorporated this statistical analysis into the revised manuscript and updated the Abstract, Discussion, and Conclusions to report the weighted mean eruption age.
  Comment: Correct the typo "colision."
  Response: Corrected.
  
  Citation: https://doi.org/10.5194/egusphere-2026-4195-AC2

Kathleen Rodrigues, Philipp P. Ruprecht, and Craig M. de Polo

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Short summary

Young volcanic eruptions can be difficult to date using conventional methods. We used light emitted by minerals to determine when eruptions occurred at Soda Lake in western Nevada. Our results identify two eruptions, about 12 500 and 5500 years ago, showing that volcanic activity continued much more recently than previously recognized. The study shows how this approach can complement existing dating methods, helping scientists better reconstruct the history of young volcanoes.


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