Higher interglacial dust fluxes relative to glacial periods in southwestern North American deserts

Domain: earth_science
Published: 2025-11-28
Editorial outcome: major_revision

Abstract
Lengthy and continuous dust flux records from the deserts of southwestern North America are needed to understand the long-term impacts of climate on dust emissions and the relative influence of regional versus intercontinental dust sources. Here, we perform a particle size end-member analysis of a ~230,000-year sediment record from Stoneman Lake, Arizona, USA, revealing the area directly downwind of this important dust source region is 1.2–10 times dustier during peak interglacial periods compared to glacial maxima. This contrasts with other global dust records and aligns with the region’s distinctive dry interglacial and pluvial glacial climates. Our analyses indicate minimal deposition of intercontinental dust and suggest the primary driver of dustiness is regional fine sediments supply, governed by desert alluvial and fluvial system responses to climate change. On the other hand, changes in atmospheric circulation and factors affecting wet and dry fallout appear to exert little control on regional dust flux variability.

Introduction
The Basin and Range province of southwestern North America (SWNA) is a large desert region and a major source of atmospheric mineral dust1. Situated between the Cascade-Sierra Nevada-Transverse mountain system and the Colorado Plateau (Fig. 1a, b), this region has emitted considerable amounts of dust since at least the mid-Pleistocene2. Yet, continuous records of dust deposition downwind scarcely extend beyond the Holocene (e.g., refs. 3, 4). This lack of long-term data hinders efforts to contextualize recent dust increases, many of which are attributed to anthropogenic disturbance5–7. Because atmospheric dust reflects upwind geomorphic and land-surface processes, dust deposition records offer a powerful proxy for reconstructing how landscapes respond to climate over long timescales—insights that are often inaccessible through instrumental or historical observation alone8.

This data gap also limits insight into how dust fluxes in SWNA respond to glacial-interglacial climate change—an important concern given that pluvial conditions and limited glaciogenic dust sources during glacial periods potentially drive regional eolian dynamics to differ from broader global trends. Because dust is both a product and a driver of Earth system processes, long-term records inform a wide range of environmental inquiry. Dust plays a crucial role in Earth’s climate, impacting radiative balance, cloud formation, precipitation, and nutrient cycles9–11. Reconstructing dust fluxes from SWNA can help quantify the region’s role in broader Earth system feedbacks, including its influence on North American ecosystems relative to dust from intercontinental sources12 and its contribution to dust deposition in Greenland and surrounding oceans13. Such records also support improved calibration of soil chronosequences14, refinement of soil production and transport models15, and validation of climate models that simulate dust–climate feedbacks16,17.

This study presents evidence that dust emissions from SWNA are out of phase with global patterns over the last two glacial-interglacial cycles. We reconstruct regional dust flux by calculating the mass accumulation rates of particle size end members in a 230 kyr-long lacustrine sediment core record from Stoneman Lake, Arizona (2050 m elevation, 34.779 N, 111.518 W). Situated on the southwestern margin of the Colorado Plateau, this enclosed, small (3.5-km2; ~5.5 catchment-to-lake area ratio) and steep (~12.6° average) alluvial basin with a basaltic catchment serves as an ideal natural dust trap, strategically located directly downwind of the Basin and Range province (Fig. 1). We compare these data to records of regional climate and landscape change to evaluate key drivers of dust flux across SWNA.

Results
Laser granulometric analyses of the upper ~13 m of core STL14 (n=205) indicate that sediments in Stoneman Lake predominantly consist of silt, with smaller fractions of clay and sand, similar to the particle size distributions of soils in the local catchment (n=6) (Fig. 2a). While most lake sediments samples exhibit modes within the clay and fine silt ranges, occasional modes appear in the coarse silt, fine sand, and coarse sand ranges. Detailed descriptions of sampling procedures and particle size analyses are provided in the “Methods” section.

Previous mineralogic studies have established that atmospheric dust comprises a large portion of sediments in Stoneman Lake18. X-ray diffraction analysis reveals an average mineral composition of 51% illite, 28% quartz, 9% kaolinite, 8% albite, 2% montmorillonite, 2% zircon, and 1% ilmenite. In contrast, local alkali basalt bedrock is composed of 40% pyroxene, 39% albite+anorthite, 17% olivine, 3% nepheline, and 1% ilmenite. The presence of illite, quartz, and zircon—not derived from local bedrock—indicates substantial inputs from external dust sources.

Anon-parametric end-member (EM) analysis using five end members optimally captures the variance within the lake sediment particle size distribution dataset (r2=0.9891) while minimizing intercorrelations between end-member abundances (Supplementary Figs. 2a, b and 4). Detailed descriptions of modeling approaches and comparisons are provided in the “Methods” section. EM1 is polymodal, consisting mostly of clay to silt-sized grains with modes at 0.18, 3.0, 27, and 600 µm (Fig. 2b). EM2 is unimodal, composed of clay to fine silt-sized grains with a mode of 5.3 µm. EM3, also unimodal, consists mostly of silt-sized grains with a mode of 13 µm. EM4 comprises silt to very fine sand with a mode of 38 µm. EM5 is polymodal, containing mostly sand-sized grains with modes at 0.18, 17, and 169 µm. Mass accumulation rates for each end member are calculated based on their fractional abundance (Fig. 3a), density, and sedimentation rate (see “Methods” section).

We attribute these end members to either local alluvial or external dust sources using sedimentological analysis, transport dynamics, comparisons with previous studies, and correlations with geochemical tracers. EM1, EM2, and EM5 collectively represent locally derived clastic sediments, accounting for 54% of the total clastic sediment volume. EM1 and EM5 exhibit polymodal distributions indicative of poor sorting, consistent with local origins. Although EM2 could be interpreted as intercontinental dust, its modal grain size (5.3 µm), accumulation rate, and variability are inconsistent with it coming from a transoceanic source. Observational data indicate that most intercontinental dust reaching western North America is likely to be in the range of 0.5–3 µm19–21. Furthermore, EM2 accumulation rates (Supplementary Fig. 3c) both exceed and are out of phase with measurements downwind of potential intercontinental dust sources, which peak during glacial periods (Fig. 4a). Instead, EM2 accumulates most rapidly as local lake levels fall during early interglacial periods making it more consistent with lake margin sediment redeposited into the center of the basin (e.g., ref. 3).

EM3 (mode: 13 µm) and EM4 (mode: 38 µm) are interpreted as dust, comprising 46% of the total clastic sediment volume (Fig. 2c). Their particle size distributions are too large to be interpreted as intercontinental dust and instead closely resemble other modern and paleo-dust deposits on the Colorado Plateau3,4,22 (Fig. 2b). A nearby study of Holocene sediments from Montezuma Well, Arizona, identified two dust end members with nearly identical modes to EM3 and EM44 (Fig. 2b). Montezuma Well is in a small sinkhole in carbonate bedrock located only 25 km WSW of Stoneman Lake and is likely downwind of the same dust sources (Fig. 1c).

Mineralogical and geochemical analyses offer further support for source attributions. Previous measurements of conservative elements Rb, Zr, and Ti serve as tracers for eolian and local sedimentary inputs18. Rb, substituting for K as an interlayer cation in illite clay ((K,H2O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)]) and Zr, controlled by zircon (ZrSiO4) abundance, together represent dust input. Because zircon grains are larger and heavier than illite clay particles, the Zr to Rb ratio is an indicator of the relative grain size of dust inputs. Local inputs are indicated by Ti, here mainly associated with ilmenite (FeTiO3)18. (Zr + Rb)/Ti correlates positively with the abundance of EM3 and EM4 relative to EM1, EM2, and EM5 (Fig. 3c, d), reinforcing the interpretation that EM3 and EM4 are dust and EM1, EM2, and EM5 collectively represent local alluvial sediment. Additionally, the EM4/(EM3+EM4) ratio positively correlates with Zr/(Rb+Zr) (Fig. 3e, f), supporting the distinction of EM4 as coarse dust and EM3 as fine dust.

Local sediment accumulation rate (EM1+EM2+EM5), or erosional flux, rises sharply after glacial terminations and remain elevated until the next glacial maxima (Fig. 5d). Median erosional flux is 4.72 g·cm-2·kyr-1 during interglacials and 2.45 g·cm-2·kyr-1 during glacials (Fig. 5d and 6h). The median denudation rate over the last 230 kyr is 0.35 cm/kyr (derived directly from erosional flux, see “Methods” section), consistent with other regional basalt flows (Fig. 5f).

Median total dust accumulation rate (EM3+EM4), or dust flux, over the last 230 kyr is 0.46 g·cm-2·kyr-1, similar to measurements of long-term dust accretion in regional soils14 (Fig. 5a, e). Interglacial (Holocene, MIS 5, and MIS 7) dust flux is 0.61 g·cm-2·kyr-1, higher and more variable than glacial dust flux (MIS 2, 3, 4, and 6), which has a median value of 0.38 g·cm-2·kyr-1 (Fig. 5a). Peak interglacial conditions directly follow glacial-to-interglacial transitions and exhibit the highest dust fluxes, with median values of 0.89 g·cm-2·kyr-1 during MIS 5e and 1.78 g·cm-2·kyr-1 during the Holocene (Figs. 4b and 5a). Holocene dust flux values align with observations from the San Juan Mountains of Colorado3,23,24 and modern measurements throughout the region25–28 (Fig. 5e). These peak interglacial episodes are 1.2 to 10 times dustier than MIS 2 and 6 glacial maxima.

Fine dust (EM3) constitutes 64% of the total dust signal and drives total dust accumulation trends. It exhibits its highest fluxes and variability during peak interglacials (Holocene and MIS 5e) (Fig. 5b). Coarse dust (EM4) comprises the remaining 36% of the total dust signal. Its flux rate is higher overall and less variable during glacial periods but exhibits higher peak values and variability during peak interglacials (Fig. 5c). Notably, both dust populations contribute to higher total dust fluxes during the MIS 4 glacial (0.7 g·cm-2·kyr-1) compared to the MIS 2 (0.24 g·cm-2·kyr-1) and MIS 6 glacials (0.35 g·cm-2·kyr-1) (Fig. 5a, b, c).

Methods
Core STL14, recovered in 2014, preserves a sediment archive of the last ~1.3 million years45. The core’s current age model18 (Supplementary Fig. 1 and Supplementary Data) integrates radiocarbon dating45,66, tephrochronology45, and climostratigraphy18,45. The climostratigraphic approach is supported by correspondence of various stratigraphic datasets18,45,63 to global climate changes at Marine Isotope Stage (MIS) and MIS substage scales as well as changes observed in other regional records with independent age control (e.g., refs. 46,47,67). The age model was constructed using R-based Bayesian age modeling software, Bacon v.2.368. We use the median age model for our analyses and visualizations.

Volumetric sampling of core STL14 was conducted at Northern Arizona University’s Laboratory of Paleoecology, where the working half of the core is stored (the archive half is stored at CDSCO at the U. of Minnesota). The median sample resolution by climate stage is as follows: Holocene: 0.4-kyr; Last Glacial: 0.7-kyr; MIS 5: 1.0-kyr; MIS 6: 1.6-kyr; MIS 7: 1.5-kyr. The clastic fraction of each sample was isolated through successive chemical washes of 30% H2O2, 1N HCl, and 1N NaOH to remove organic matter, carbonate, and biogenic silica, respectively. Previous quantitative X-ray Diffraction (qXRD) and sedimentological analyses indicate negligible carbonate content in sediments younger than 160 ka, with diagenetic concentrations in older sediments18 that were avoided during sampling. Processed samples were then sent to the Paleoclimatology Laboratory at the California State University, Fullerton, for laser granulometry using a Malvern Mastersizer 2000 coupled to a Hydro 2000G dispersion unit. Silica carbide standards were analyzed twice at the start of each run, once every ten samples thereafter, and once at the end of each day of analyses to assess equipment stability, reproducibility, and analytical error. Since 2017, a total of 4129 standards have been analyzed, averaging 13.11 microns (µm) with a standard deviation of 0.10 µm.

Particle size distributions (PSDs) from all 205 core sediment samples were processed using AnalySize software69, an end-member analysis MATLAB GUI package designed for unmixing PSDs into constituent end-member (EM) populations. We employed a non-parametric approach to identify multimodal populations, as expected for locally sourced sediments. AnalySize runs multiple scenarios that fit 1–10 end members to the measured grain size dataset, returning model performance statistics alongside PSDs and percent composition for each modeled end member (Supplementary Fig. 2). Scenarios with 3, 4, and 5 end members (3EM, 4EM, and 5EM) were selected for further consideration based on their fit to the measured data, with total model fit (r2) values of 96%, 98%, and 99%, respectively. These scenarios also exhibited minor intercorrelation among constituent end members, suggesting avoidance of model overfitting (Supplementary Fig. 2a, b).

Similarities in modeling results for EM1 across each scenario (3EM, 4EM, and 5EM) suggest a robust model result for EM1 (Supplementary Fig. 2c–e). Each scenario’s EM1 has a primary mode at 0.18 μm and one to two secondary modes in the clay to silt range, indicating poorly sorted, i.e., locally sourced, sediments. Each model scenario produced similar stratigraphic abundances of EM1 (Supplementary Fig. 3).

End members 3EM3, 4EM4, and 5EM4 show similar unimodal distributions (31, 42, and 38 μm) and stratigraphic variation (Supplementary Figs. 2c–e and 3), consistent with short-range-transport dust (sourced from <100 km away) and coarse dust particle size distributions identified in other regional studies3,4,22. Here again, similarities between each scenario suggest a robust model result.

The primary distinction between the scenarios lies in the modeling of sediment populations in the very fine to fine silt range. In the 3EM scenario, 3EM2 exhibits a unimodal peak at 9.5 μm (Supplementary Fig. 2c), characteristic of medium-range-transport dust (sourced from 100s of km away). If both 3EM2 and 3EM3 are interpreted as dust, this scenario suggests no input of local alluvium during interglacials MIS 7 or MIS 5e (Supplementary Fig. 2c), contradicting geochemical and palynological evidence indicating vigorous sediment transport during these periods18,63. The 4EM scenario appears to divide 3EM2 into finer (4EM2: 6 μm) and coarser (4EM3: 13 μm) end members (Supplementary Figs. 2d and 3). We interpret 4EM2 as resuspended fine sediment from the lake margin (e.g., ref. 3). This process occurs during early interglacials when lake levels drop, exposing lake bottom sediments to erosion, and accounts for high accumulation rates of 4EM2 during MIS 7, 5e, and the Holocene (Supplementary Fig. 3).

Ultimately, we selected the 5EM scenario, as it retains the EMs of the 4EM scenario while introducing a fifth end member (primary mode at 169 μm; secondary modes at 0.18 and 19 μm) that enhances model fit during specific time periods around 31 and 12 ka (Supplementary Fig. 2e) when coarser material intercalated the lake stratigraphy. 5EM5 appears to be another locally sourced sediment population, given its coarse and multimodal PSD. In summary, the 5EM scenario maximizes the variance accounted for by the end-member model (Supplementary Fig. 2a, b), reduces end-member intercorrelation (Supplementary Figs. 2a, b and 4), and yields end members whose PSDs align with those from other regional dust studies. Furthermore, accumulation trends and source interpretations of end members in the 5EM scenario are consistent with geochemical measurements by Staley et al.18 (see Text).

The mass accumulation rate (MAR) of a sediment population is calculated by multiplying the sedimentation rate by the fraction of that population in the bulk sediment (determined by the end-member model) and its density17. Because this study focuses on clastic sediment MARs, the fractional volume of non-clastic material, including organic matter, biosilica (bSi), and authigenic minerals, and its effect on dry bulk density (DBD) must be determined.

Non-clastic material was determined during previous studies (Supplementary Fig. 5). Total organic carbon (TOC) was measured at a median sample resolution of 0.74-kyr45. Modal percentage estimates of bSi (diatoms and sponge spicules) were derived from smear slides at a median sample resolution of 2.8-kyr45. Authigenic carbonate content was quantified from smear slide observations45 and qXRD18.

Using DBD as a proxy for clastic dry density (DD clastics) is complicated by the presence of low-density organics and bSi. To address this challenge, we applied linear regression to DBD below 9.05 meters composite below lake floor (mcblf)—where TOC and bSi are negligible, resulting in DBD ≈ DD clastics —to adjust DBD values in the upper portion of the core (0–9.05 mcblf) where TOC and bSi are non-negligible. We first normalized the DBD values above 9.05 mcblf to the linear regression line of the DBD measurements below 9.05 mcblf (Supplementary Fig. 6). Next, we constrained the normalized curve to maintain (1) continuity with the DBD curve at 9.05 mcblf and (2) consistency with the original linear regression, ensuring that both curves share the same linear best-fit equation. The adjusted curve, DD clastics, lies primarily within 1 standard deviation (σ) of the linear best-fit line. Notably, below 9.05 mcblf, −1σ excursions of DBD are coincident with brief increases in bSi (Supplementary Fig. 6). We assume that the dry densities of each modeled EM are equivalent to DD clastics.

Due to uneven sample spacing of all factors involved in MAR calculations, each dataset is linearly interpolated to the resolution of the particle size dataset. The MAR of clastic end member x (MAR EMx) is calculated as:

MAR EMx = SR * f EMx * DD clastics (1)

where SR is the sedimentation rate derived from the median age model, f EMx is the bulk fractional composition of EM x relative to other clastic end members and non-clastic content (TOC, bSi, and TIC), and DD clastics is the clastic dry density (Supplementary Fig. 5). MAR calculations for dust end members (EM3 and EM4) are multiplied by a lake-to-catchment area scaling factor (0.63/3.54) to account for catchment focusing effects24. Total dust mass accumulation rate (DMAR) is the sum of MAR EM3 and MAR EM4, while MAR of local clastics (MAR LC) is the sum of MAR EM1, MAR EM2, and MAR EM5.

Denudation rate of catchment basalt (DR) is derived directly from MAR LC by dividing by the density of basalt and multiplying by a catchment area scaling factor that assumes no erosion from the lake floor:

DR = (MAR LC / ρ basalt) * (Catchment area / Lake area) (2)

This calculation relies on the assumptions that (1) material is detached from bedrock and transported into the lake immediately, which may not hold true during periods of geomorphic stability (e.g., MIS 2 and MIS 6a) and (2) no mass is lost to solution in through-flowing groundwater. To address these issues, we report DR as an integrated value representing average denudation of the catchment since ~230 ka and treat it as a minimum value.

Analytical error for each calculation is assessed using a percent error propagation method that incorporates errors in bulk composition, density, and catchment area scaling factors. Inputs for our uncertainty calculations include a 3% error for density to account for potential water retention after drying the samples70, and a 4% error for TOC, as reported by UNM’s Center for Stable Isotopes. Given the inherent uncertainties in estimating modal abundances of sediment constituents from smear slides, we apply a conservative 20% error for the sum of authigenic carbonate and bSi. The most significant source of error arises from estimating the area of lake floor deposition. The current lake floor covers approximately 0.63 km2. We establish an upper limit of 0.86 km2 that corresponds to the area enclosed by the bedrock slope-to-fan apron transition—a distinct topographic break surrounding the lake (Fig. 1d). This slope transition represents a definitive boundary above which sediment accumulation is unlikely. Conversely, we define a lower limit of 0.38 km2 based on the low-stand lake area of the most recent megadrought, which roughly corresponds to the area currently occupied by reeds, the darker area in the middle of the lake. This range of uncertainty corresponds to a 40% error in the lake-to-catchment area adjustment factors. It is worth noting that changes in lake depth likely influenced the size of the depositional area on the lake floor, increasing during glacial periods and decreasing during interglacials. Therefore, glacial MAR values may fall within the upper uncertainty envelope, while interglacial MAR values may reside within the lower envelope. Therefore, we report the factor by which DMAR changes between glacial maxima and peak interglacial conditions as a range that incorporates all the above uncertainties.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "Dear Editor,\nHerewith my review of Staley et al. submitted to your journal.\nThe authors report on a very comprehensive of an interesting lacustrine record across the last 200 kyr of time. They focus on\ndust accummulation over time and whether or not changes occurred during glacial-interglacial cyclicity. Such a study could\nbe of interest for Nature Communications searching for studies with a broader geoscientific audience and impact. Here, are\nmy main thoughts and concerns with the study. Below, you find Line-by-line thoughts:\n• the study has not been uniquely sent to your journal. The dataset seems to be completely sent to Geology also, where\nanother part of the study is being discussed. This makes the current work less attractive, as the work is split into two, but also\nless holistic. Why would one discuss the local dust transport separate from the regional dust transport? In the end, it is the\nsame region and one cannot be seen separate from the other? The authors wish to publish in two of the better journals in\ntheir fields, why not combine that into one great study rather than two intermediate studies?\n• There is not a proper uncertainty propagation when the differences are calculated (standard errors) of dust fluxes between\nclimatic stages. The 1.6 times change in flux should be going along with a standard error to know what is its significance. This nor any of the other ‘differences’ nor standard errors are quantified in the submitted paper. The key figure providing\nfluxes per stage is rather small and not sufficiently explanatory (see below minor comments)\n• The Results section jumps into interpretations from the second line, while many results are not described and only come in\nthe Discussion section. The Discussion section has a too high degree of certainty given in words to interpretations. As most\ninterpretations come back in the Discussion anyway, it is needed to clean the Results section from interpretations and\nappropriately describe interpretations as possibilities in the Discussion section.\n• The Discussion section dwells upon details of functioning how it all may have happened, the model, while I miss a much\nmore straightforward line of reasoning from data to simple interpretations. Some claims further in the Discussion section are\nmore ‘review paper’ like than that these relate directly to data in the current paper, also because the ‘other half’ of the data\nare not discussed here. The authors may have gone much further in their reasoning and describe that, while forgetting that\nthe reader has to do it with what is currently provided. A more direct and concised Discussion chapter will help the paper.\n• For a wider audience, it is needed to write with much less abbreviations and with less assumptions as if the reader would\nknow things, see minor comments. The reader for Nature Communications should be regarded as an interested geoscientist,\nnothing less and nothing more. Different writing is needed for that.\nBased upon the above thoughts, I recommend to ask the authors to combine this study with that submitted to Geology into\none, very solid study with high impact. Besides, the current work needs a major writing revision, while the science seems\nappropriate.\nMinor Comments / Ideas / Suggestions:\nLine 16: it is needed to add the standard error of the difference to this number, such to see the relevance of this quantification\nwithin the total uncertainty of the data.\nLine 73: The second sentence of the Results section brings an interpretation. It would be better to first describe the results.\nLine 71 Results: please start the results section with a basic description of the main results, namely Laser Granulometric\nresults of the samples.\nLines 81-85: EM-2 would be perfectly in line with long-range dust source, the reasoning here seems a bit weak?\nLine 104-105 Ruling far distance dust transport is a bit dangerous, I would think. First, what about relating EM-2 to long\ndistance transport?\nLine 111: The authors should use less abbreviations in the running test: DMAR, MRT, SRT, etc. and in particular not without\nexplanation in each paragraph. The journal is aimed at a wider audience than specialists. This whole paragraphs reads\ngreat for those involved in the study, but is impossible to read for a (relative) outsider. This could also include finding other\nwords for these items, MRT does not even include the ‘dust’.\nLines 122-125: here it is needed to present all results: Figure 4 is only partially presented and the key number from the\nabstract including its uncertainty does not figure in the Results.\nLine 127: The phrasing is not scientific. EM-3 is an end-member peak in a end-member modelling scenario reprenting the 13\nmicron grain size mode. EM-3 could relate to Medium-range transport dust, that, if that would be the case, is likely of North-\nAmerican origin. It is an interpretation, not a fact. The authors have to rewrite the text making clear distinction between facts\n(a measurement, 13 micron mode) and an interpretation (MRT, North American source).\nLine 132: write in full STL\nLines 143-145: please explain “cannot be controlled by intervening processes of transport and deposition”. Who controls\nwhat? What is intervening what? Is the MRT interpretation impossible to validate?\nLine 155: it would help if the authors write more to a general audience also by more explicit explanations. Here it is assumed\nthat people know what is ‘wet removal’, that the glacials have the highest effective moisture.\nLines 154-156: isn’t this partially a circular reasoning? First, it is assumed that a certain grain size class is purely dust, and\nthen, because there is higher dust flux, there is not much wet removal?\nLine 159 SWNA?\nLines 159-160: If MRT is renamed to desert dust, why not initially starting with that name, in my view, better than MRT as\nmore explanatory, and better than using two names in the running text.\nLine 159: Evidence ‘dictates’, not sure if that is really the appropriate academic wording.\nLine 162: I propose to include the grainsize mode also in between brackets, SRT, EM-4, 38 micron). Particularly the\ngrainsize is what helps the reader to memomize the data and grains, EM-4 is different for every study, as is SRT.\nLines 163-164: this should be in the Results. And, looking at Figure 4, there is no mention of SRT, so where should I look?\nLines 166-167 Please explain “whose published depositional ages correlate to MARsrt increases”.\nLines 172-173: meaning the same record is being published elsewhere? One comprehensive study would have been nicer\nas SRT and MRT are not that different?\nLine 177: SWNA in the title is not very explanatory to a wider audience\nLines 208-209: I do not see this in Figure 3: the transition from MIS 6 to 5 is rapid in the Desert Dust curve given, where is\nthe 20kyr lag?\nLine 232-233: Provide the reader means to find this in the figure, you mean to look at c, d, and e? Relating the tiny spike at\n7>6 transition seems too far, the overall agreement in trends between b and c/d/e is, however, worthwhile more reference.\nLine 258: The lack of a sustained vegetation cover in glacial times is a primary reason for increased dust fluxes, or do the\nauthors include that in the ‘dust production’?\nLines 260-263: that seems a very straightforward conclusion that one may derive from the data, why was it not brought\nforward earlier? In the relatively complex discussion before this part, there was very little discussion about vegetation.\nLines 260-263: there must vegetation records for comparison to corroborate this claim?\nLines 266-267: Figure 5 gives a clear lower STL MARsrt for the mid-Holocene compared to Early Holocene and Late\nHolocene, that is not suffice?\nLines 269-274: higher effective moisture means more vegetation cover and less exposure and so lower dust transport. I do\nnot see why the current data are adding to the specific discussion of climatic perturbations other than that reasoning. It\nseems the discussion is rather complex for a not such a difficult case?\nFigure 2: why are the real data hidden behind the end-member analyses? Choices for line thickness are such that the real\ndata are not easy to trace in the figure.\nFigure 4: I find this figure / table hard to read, it could be my age, but it all seem rather small, particularly because the red\noutliers need so much space that the averages and 2.7sigma intervals are somewhere near the bottom of each panel. Would\nit be an option to leave the outliers for a figure in the appendix and blow up this panel focussing on the main box and\nwhisker plots?\nFigure 4: I cannot find the paper nor Methods section what intervals are included in ‘Glacial’ and what in ‘Interglacial’. Same\nfor Early, Middle, Late, add a description in the text / caption. It would help to indicate early, middle, late also to Figure 3 on\nthe time axis. While dividing into glacial / interglacial seems evident, it may not necessarily be. One could argue to only\ncompare Stage 1 and 5e with Stages 2,3, and 6. Or more indendant, a ‘cutoff’ could be used on the LR04 isotope curve to\ndecide which data point bins in what stage, glacial or interglacial. It may make the results more significant and definitely\nmore independent.\nFigure 4: labels ‘e’, ‘abcd’ are unclear, these all belong to MIS5? It seems there is space on the image to show that.", "reviewer_2": "This is a solid study of the dust flux in North America southwest, adding to a growing body of knowledge of the relationship\nbetween dust production and climate. The noteworthy results include 1) identifying dust in lake deposits; 2) displaying high\ndust flux in interglacials than glacials; 3) trying to clarifying the relationship between dust production and climate. The study\nis valuable, but I think the discovery is incremental and the evidence of some interpretations (particularly the basis of 5 end\nmembers and why they have different sources and transported by different wind) is vague. See detailed comments below\nIntroduction: I do not see the tight connection of the research topic and justification of scientific importance in introduction. Ice\ncores and deep sea are great proxies for global dust budget. The importance of American southwest to the global picture is\nquite vague here, and there is no critical knowledge gap or debates described to clarify the contribution of this study. The\nhuman impact on dust generation also seems not relevant given the study extends back to the late Pleistocene. I see the\nimportance at the end of the discussion, but here it is not appropriately sold.\nBackground: the text lacks key description of the background (description of figure 1), particularly the climate and\natmospheric circulation patterns.\nResults: 1) why choose five end members? Is this based on observation and sound geologic interpretation or just math\ntechnique? I think it is the latter, which, in my opinion, does not have geologic significance. I understand there is knowledge\nof modern dust source (like Tau et al., geology) that this study is based on, but the reasoning is not well clarified. 2) The\nexplanation of each end member seems very casual. For example, how physical and chemical weathering affect the\nminerals ton have EM1and EM5? I know the reference is cited, but such interpretation is the core of the study and should be\nclarified here. 3) if EM 1 coalesces with EM2, what is the basis to separate them?\nHow does the geochemical data support? It needs some clarification.\nDiscussion:\nSection 1: 1) the evidence to rule out “processes of transport and deposition” is not clear; 2) Westerlies may be stronger\nduring glacier maximum, what about monsoon? The evidence ruling out wind intensity change is also not compelling. 3) cite\nreference and evidence for that the highest effective moisture was during glaciers. 4) evidence for the different source of\nSRT and MRT?\n5) Anderson et al say that “fluvial aggradation beginning during full-glacial times and continuing into subsequent\ninterglacial”, is this consistent with the observation of SRT?\nSection 2: line 177-179, this observation is limited to mid-latitude, right? How about desert, why that is not included given\ndesert to the north and northwest of China loess plateau has been suggested to be a source. Line 181, the transition from\nalluvial source to desert is very confusing. Line 182, if I understand right, this is for MRT, why not replace “fine” with the grain\nsize for clarity. Any evidence of production of this grain size range at desert hillslopes? line 194 and 197,it is not clear what\nare the climate-driven surface processes, and how they were controlled by climate and ecological changes. Line 209, I\nthought with the stage set up earlier in this paragraph, here you want to talk about the slope instability during the interglacial,\nnot sure why you change to talk fluvial adjustment to sediment load increase?\nLine 261-263, this seems different from what has been said earlier. Is this a comparison of glacier maxima to the rest of the\nglacier periods? I think the information provided so far is that glacier is less dustier than interglacial.\nI think the rest of the discussion is good and interesting, but they are based on discussion in the first two sections. The lack\nof evidence and clarity in the first two sections undermines the extended discussion.", "reviewer_3": "This is an interesting paper turning the heads on peak dust flux during an interglacial, rather than the wet glacial in the SW\nUSA. The basis of this inference is the sediment record from Stoneman Lake, a small lake in central Arizona. This lake has\nbeen well studied and dated with a high-quality paper in GSAB. This is a new and important record to sort out hydrologic\nsystem response to late Quaternary climate variability.\nThe central inconsistency of this paper is the lack of granulometry data from the surrounding small catchments to identify\nlocal water-transported flux of particles versus aeolian dust flux. There needs to be a detailed study of the source to sink flux\nof particles from numerous sources around the lake including catchments, overland flow, and aeolian proximal and distal\nsources. What is the geomorphology and soils around the lake? Vesicular A horizons, a common desert soil morphology,\nare loaded with aeolian particles, ripe for erosion and reflect storage of aeolian particles on the landscape, not a primary\naeolian flux.\nIt would be informative to contact PI-SWERL person, in tuned with aeolian particulate sources in the SW to provide a fuller\nassessment of the conditions of aeolian flux, related to source, sediment availability and threshold wind speed. The far-travel\ndust sources should have a different mineralogic signature than local sources. There needs to be more data to support the\naeolian flux premise of this paper; it is not overly convincing, at least to me.\nAlso, the sedimentation rates and dust flux are low to very low particularly from 30 to 12 ka, which indicates that this system\nhas low sensitivity to aeolian flux? I question what the low variability in aeolian flux from nearly zero to ~1.5 g/cm/ka at ca.\n130 ka actual reflects and is this low variability significant? It would be helpful to assess the current aeolian flux around\nStoneman Lake; is this area sensitive to current dust sources? Why are the early Holocene rates (11-9 ka) of dust flux, when\nmany pluvial lakes existed, though at declining levels, so much higher than 5e and stage 7. Something is missing in\nexplaining these state differences in aeolian flux between Stage 1, 5 and 7, suggesting non-analogous aeolian sources\nand sinks.\nLastly, a recent detailed climate model of the last interglacial in the SW USA demonstrated a dichotomy in precipitation\nbetween Arizona and New Mexico/TX with Arizona much drier than to the east (Insel and Berkelhammer, 2021 in J. Quat\nScience), with a warmer Gulf of Mexico, potentially energizing the NA Monsoon. In this analysis there would be a dynamic\nboundary between moisture sources from NA Monsoon and Equitorial Pacific, particularly in the summer and how aeolian\nflux would be governed in the SW USA remains an open question. More data and climate modeling is surely needed."}, "author_response": ""}, {"round": 2, "reviewer_comments": {"reviewer_1": "Dear editor,\nHerewith my review of Staley and colleagues sent to your journal for consideration.\nI have seen this article before in another review round and I see now that the authors have considerably improved their work,\nalso in response to my comments.\nA main comment I had was that the regional and local dust records were discussed separately in two different papers sent to\ndifferent journals. The authors have now merged these two papers considerably improving the work.\nI still think the work can be very interesting to be published in your journal. Scientifically, I have no doubt about the\nruggedness in which the authors have performed their data gathering, data analysis and interpretations set into the frame of\nscientific knowledge and data. I have worked myself in stratigraphy, paleoclimatology and including with long-term dust\nrecords, while I am not totally familiar with the Quaternary and geomorphological aspects of the study nor with the region.\nFor a further detailed critical review on these matters, you will depend on other reviewers, which, as it seems from the\nprevious round, is secured already.\nMy current opinion is that I do not think the paper writing has matured yet. My advice is to ask the authors to considerably\nimprove the clarity of writing by focussing on the key message of each section and paragraph in simple words and by that\nmaking the article much shorter with less figures. All sections and the figures of the paper are not highlighting the key\nfindings and key message and lack easy overview of important messages from explanation of these. Regularly, the paper\nreads like a review paper more than a Nature Communications paper. You may consider my opinion as to be mostly\nimportant from the scientific point, I still bring a bit more detail here to the writing style and presentation, as that is also an\nimportant aspect to the science communication which an article is. The title is too general, the abstract not bringing the key\npoints in a direct manner, the introduction is not specific enough, the discussion is often too much written like a review and\nthe figures bring a lot of points and data, some of which are hardly used and others could be better merged. Two model\nfigures are brought that should be merged and simplified, as it seems, and the same seems valid for some of the data\nfigures. This may become a key paper on the topic if the key message is brought readily and straightforwardly from the\nbeginning (title and abstract).\nBelow my more detailed suggestions to the paper:\nLine 1-2 It seems the \"Hillslopes to dust\" part of the title is a bit confusing as hillslopes can be dusty themselves, and the\ntotal title does not hold the key finding of the paper, which would make it attractive, now the title is a more a sort of review\nwithout big excitement.\nLine 11 rivers are part of alluvial systems and so fluvial systems are part of alluvial systems while not all alluvial systems are\nfluvial. Find better wording or explain?\nLine 10-32 It is needed to read the Nature Bold Paragraph guidelines to improve the abstract. There is no key research\nquestion explained rather than 'Understand the geomorphic impacts of climate change' which is too general, what exactly do\nwe still need to know? The methodology (end-member, STL-14, sediment core) nor abbreviations (SWNA, STL) make it less\nattractive. Writing should be more direct and concise, rather than first explain the interpretation (line18-19) first come with the\nfinding (line 19-20) and then find out time is up to explain it (delete line 18-19 from the abstract) and explain the main text.\nLine 25-27 this is the key finding, right? Why is it only there, not in the title, not early in the abstract? To make it attractive and\nclear to the reader what has been found new compared to earlier studies, bring this directly and then explain this key finding\nin the remainder of the paper.\nLine 28-30 is there immediate and direct evidence for this in this work? Then it is also a second (subordinate?) key finding,\nright?\nLine 30-32 could be very important, third, subordinate, key finding? Not being exactly expert in the field of the authors, while\nhaving worked quite a bit with long-term dust records, still, this is rather specialized knowledge, that could be in the abstract,\nbut importantly then it needs more explanation or different, simpler wording. It is a general journal this is sent to, not a\nspecialistic one.\nLine 61 One could also start the introduction with line 61 and leave the first two paragraphs for a review paper, it gives space\nin the article for more direct text, such as, in particular also for specific missing knowledge to the general statements given in\nLines 67-71. What exactly is missing due to these long-term records are 'largely' absent? What means largely absent? There\nare no references given with the statement, why not? There are records it suggest, what do these show?\nLines 72 - 123 these are a mix between rationale, introduction and methods. I would not write it the way it is done now, as it\ncombines the study sites and methods with explanation of what these sites mean in terms of environment and how these\nrecords may be interpreted. But because the records are not yet there, the reader has to remember a lot of things, while the\nexact same reasoning will come back in the article when the data are interpreted. So, most text is duplicate. I would skip this\nreasoning here, refer to the methods for the study site specifics, and use the space here to provide a longer introduction to\nthe work setting the research questions in the frame of the state-of-the-art knowledge with only a minor 'approach' paragraph.\nLines 124 Results: Most of the results are followable and logically written in order. An outsider has, however, to push all gas\nand release the breaks to keep up with the matter. This could still be improved by starting paragraphs with more easy\nphrasing of the main finding presented in that paragraph without abbreviations. As example, lines 138-140, have an\nexplanation to something the outsider does not yet comprehend and they are thinking 'why do I read this?'. Next lines, bring\nthe key finding of this paragraph: \"46% of the total clastic sediment volume is interpreted as being eolian dust\". If the latter\nwould be the first line, the reader would know why to read the explanation of this finding in the line after that one. Another\nway, in general, to write more clear is to shorten paragraphs to one message per paragraph (the first line) and two-three\n(max. four?) lines explanation and then start a new paragraph with a new, next message, etc.\nLines 197 onwards Discussion: the Discussion suffers from the same needed improvement in writing clarity as the Results.\nAs example, line 224-225 bring the key results of a long section of reasoning. I would turn this completely around to let the\nreader know directly what comes out and then explain this, particularly if this is done in the 'short-paragraph' style explained\nabove, it will considerably help readability. It could be in steps to go through a certain reasoning, but I would not wait for the\nvery end to come with the finding. And, turning it around likely also results in less 'review-style' writing and more to-the-point\nreasoning resulting in less text.\nLine 228-230 is typically Introduction content and here I would come immediately with the finding: \"we find higher dust\naccumulation during peak interglacial conditions\". \"This is in contrast with…\". Or, \"the higher dust accumulation during peak\ninterglacial conditions in … is in strong contrast to…\" to make it ever more short and to-the-point.\nLine 271 explain why it does not capture this\nFigure 1 why is the well site not indicated in 1C?\nFigure 3 I would think the global records can all go to Figure 5? And, instead better here to combine with data in Figure 7?\nAll data new in the paper in one figure?\nFigure 6 and 8 to be combined? These schematics are very important to such papers, but the complexity is a bit too high it\nseems? And the need for two is not clear to me, apart from that a lot of text is added into them, which could be done more\nschematically with T up (arrow) and P down (arrow). Clouds could be schematized into one cloud darker with thick rain or\nlighter with thin rain, to save space", "reviewer_2": "This manuscript offers an interesting dataset and insights that could make a significant contribution. The authors have\nsignificantly revised the previous version by adding grain-size data and details of end member analysis and have expanded\nthe discussion to include how climate change affected source terranes and dust production. The exploration of various dust\nsources and their changes in response to glacial and interglacial climates is intriguing. However, while the work presents\nsome compelling ideas, it requires reorganization to clarify the reasoning process and ideally the inclusion of new data to\nsupport key interpretations in the discussion. As currently interpreted, the dataset may not justify publication in Nature\nCommunications. After reorganization and strengthening the reasoning with evidence, the work could make a substantial\ncontribution to a discipline-specific journal.\nHere are some specific comments:\n1. The introduction and background information are currently combined in a way that causes confusion. The interpretation of\nsediment sources for each dust grain-size fraction is crucial to this study, yet the manuscript treats this information as\nbackground without citing any references or repeats data interpretation. This leaves readers wondering about the basis of\nthis knowledge. I suggest adding a section titled 'Geologic Background,' where the authors can introduce the study site,\ndescribe the wind patterns, detail the bedrock compositions, potenital sources, and nearby drainage systems.\n2. Results seem like Results and Interpretation; it should be better streamlined.\n3. The discussion that dust abundance only reflects sediment supply in source terrane is not well supported.\n4. The discussion about aridity and precipitation vs. moisture in glacial vs. interglacial period is confusing.\nLine 44-45, autogenic vs. allogenic processes, not clear what is specifically referred to in this paper. It will be helpful for\nreaders if the terms in the subsequent sentences are linked directly to these two terms.\nLine 64-67, this sentence is correct but does not fit in here well for the writing does not extend to explain why studying past\ndust record is relevant to changes induced by human activities.\nLine 73, rapid climate change only refers to glacial/interglacial cycles here, be specific.\nLine 133, the 5 end members are not described.\nLine 138, It is confusing to lump quartz with a clay mineral and a heavy mineral zircon together. Rephrase to something as\nquartz accounts XX% (what is the link between quartz and basalt?), illite is the dominant clay mineral and it can not\nproduced from weathering basalt, and abundant zircon grains can not be from basalt.\nLine 140, the connection between the two sentences is not clear. How do quartz, zircon and illite link to EM3 ad Em5, are\nthey mostly in this two end members? No evidence is provided.\nLine 142-143, how about flow velocity? Strong vs. weaker wind.\nLine181-190, why EM2 can not be dust with sources between those of EM3 and EM4? What is the relationship between\nEM5 and Ti/(zr+rb)? EM2 peak is high, what about the element ratio is mainly driven by EM2? Also can EM2 by the\nweathering product of EM3 and EM4 (thus ultimately dust) given that catchment soils have high EM3-5? Can EM5 be from\nepisodic sandstorms?\nFigure 3 has lots of information not mentioned in the text.\nLine 207, Tau et al say that “Particle-size distributions reveal fine dust transported during winter from the northwestern\nSonoran Desert and the Mojave Desert and coarse dust transported during summer from the southwestern Sonoran Desert,\nsimilar to current climate systems and dust pathways.” Different from the argument that is cited for.\nLine 220, Even the westerlies are stronger during glacier period, how about monsoon? McGee et al. say “We demonstrate\nthat a wide range of data supports wind gustiness as a primary driver of global dust levels”, which is exactly opposite to what\nthe paper is cited to support.\nLine 221, do we know roughness should be higher or lower during glacial period?\nLine 233, appear to be influenced by global climate changes, is it specifically glacier-interglacial cycles? The reasoning flow\nis confusing here.\nLine 245, “wetter”, you said monsoon and tropical cyclones were suppressed, how come it became wetter or have increased\neffective moisture (what is that)?\nLine 295,” Verde Valley dust” is there any geochemical evidence to support the interpretation? This is an important\ncomponent of the dust generation mechanism."}, "author_response": "Below we respond to the comments made by each referee and the Associate Editor. Comments\nare italicized and our responses are in regular font.\nReviewer #1’s comments (italicized) and our responses:\nThe study has not been uniquely sent to your journal. The dataset seems to be completely sent to\nGeology also, where another part of the study is being discussed. This makes the current work less\nattractive, as the work is split into two, but also less holistic. Why would one discuss the local dust\ntransport separate from the regional dust transport? In the end, it is the same region and one\ncannot be seen separate from the other? The authors wish to publish in two of the better journals in\ntheir fields, why not combine that into one great study rather than two intermediate studies?\nAnd\nLines 172-173: meaning the same record is being published elsewhere? One comprehensive study\nwould have been nicer as SRT and MRT are not that different?\nWe agree. We have incorporated the two studies; the other manuscript is no longer being\nconsidered by Geology. Our revised manuscript now discusses regional heterogeneity in dust\nemission caused by diverging responses between alluvial and fluvial dust sources to climate\nchange. We demonstrate this by comparing our regional desert dust and local fluvial dust\naccumulation records side by side.\n____________________________________________________________________________________________\nThere is not a proper uncertainty propagation when the differences are calculated (standard errors)\nof dust fluxes between climatic stages. The 1.6 times change in flux should be going along with a\nstandard error to know what is its significance. This nor any of the other ‘differences’ nor standard\nerrors are quantified in the submitted paper. The key figure providing fluxes per stage is rather small\nand not sufficiently explanatory (see below minor comments).\nAnd\nLine 16: it is needed to add the standard error of the difference to this number, such to see the\nrelevance of this quantification within the total uncertainty of the data.\nLine 172-173: We have calculated a range for the change in total dust flux between glacial\nmaximum (MIS 6 and 2) and interglacial maximum (MIS 5e and Holocene). The range is based on\nthe calculated error envelope: minimum of range = [median of minimum values during interglacial\nmaximum]/[median of the maximum values during glacial maximum]. Maximum of range = [median\nof maximum values during interglacial maximum]/[median of the minimum values during glacial\nmaximum]. Figure 4 is improved and presents the notched box and whisker of median values in\neach timeseries. Notches that do not overlap indicate medians differ with 95% confidence.\n____________________________________________________________________________________________\nThe Results section jumps into interpretations from the second line, while many results are not\ndescribed and only come in the Discussion section. The Discussion section has a too high degree\nof certainty given in words to interpretations. As most interpretations come back in the Discussion\nanyway, it is needed to clean the Results section from interpretations and appropriately describe\ninterpretations as possibilities in the Discussion section.\nAnd\nLine 73: The second sentence of the Results section brings an interpretation. It would be better to\nfirst describe the results.\nAnd\nLine 71: please start the results section with a basic description of the main results, namely Laser\nGranulometric results of the samples.\nAnd\nLines 122-125: here it is needed to present all results: Figure 4 is only partially presented and the\nkey number from the abstract including its uncertainty does not figure in the Results.\nAnd\nLine 127: The phrasing is not scientific. EM-3 is an end-member peak in a end-member modelling\nscenario reprenting the 13 micron grain size mode. EM-3 could relate to Medium-range transport\ndust, that, if that would be the case, is likely of North-American origin. It is an interpretation, not a\nfact. The authors have to rewrite the text making clear distinction between facts (a measurement,\n13 micron mode) and an interpretation (MRT, North American source).\nOur results are now more thoroughly described. We also clarify our reasoning for interpreting\nsources for each end member and are more careful about distinguishing facts and interpretations.\nWe have also included more context in the form of previous mineralogical and geochemical results\n(Lines 148-154) that support our end-member interpretations. Within this context, we believe these\ninitial interpretations of source are robust enough to be included in the results and allow our\ndiscussion to be more process oriented.\n____________________________________________________________________________________________\nThe Discussion section dwells upon details of functioning how it all may have happened, the\nmodel, while I miss a much more straightforward line of reasoning from data to simple\ninterpretations. Some claims further in the Discussion section are more ‘review paper’ like than\nthat these relate directly to data in the current paper, also because the ‘other half’ of the data\nare not discussed here. The authors may have gone much further in their reasoning and describe that,\nwhile forgetting that the reader has to do it with what is currently provided. A more direct and\nconcise Discussion chapter will help the paper.\nAnd\nLines 260-263: that seems a very straightforward conclusion that one may derive from the data,\nwhy was it not brought forward earlier? In the relatively complex discussion before this part, there\nwas very little discussion about vegetation.\nAnd\nLines 269-274: higher effective moisture means more vegetation cover and less exposure and so\nlower dust transport. I do not see why the current data are adding to the specific discussion of\nclimatic perturbations other than that reasoning. It seems the discussion is rather complex for a not\nsuch a difficult case?\nThe discussion has been simplified and streamlined.\n____________________________________________________________________________________________\nFor a wider audience, it is needed to write with much less abbreviations and with less assumptions\nas if the reader would know things, see minor comments. The reader for Nature Communications\nshould be regarded as an interested geoscientist, nothing less and nothing more. Different writing is\nneeded for that.\nAnd\nLine 111: The authors should use less abbreviations in the running test: DMAR, MRT, SRT, etc. and\nin particular not without explanation in each paragraph. The journal is aimed at a wider audience\nthan specialists. This whole paragraphs reads great for those involved in the study, but is\nimpossible to read for a (relative) outsider. This could also include finding other words for these\nitems, MRT does not even include the ‘dust’.\nAnd\nLines 159-160: If MRT is renamed to desert dust, why not initially starting with that name, in my\nview, better than MRT as more explanatory, and better than using two names in the running text.\nWe appreciate the comment about broad reader accessibility. We believe we have addressed this\nand have replaced most abbreviations with full text.\n____________________________________________________________________________________________\nLines 81-85: EM-2 would be perfectly in line with long-range dust source, the reasoning here seems\na bit weak?\nAnd\nLine 104-105 Ruling far distance dust transport is a bit dangerous, I would think. First, what about\nrelating EM-2 to long distance transport?\nYes, the EM-2 mode (5 um) is consistent with LRT, but its accumulation trends and absolute rates\nare not. Asian dust is the most likely source of LRT for North America. If we compare flux trends of\nAsian dust to those of EM-2 in Fig 3d and Methods Fig. S3c, EM-2 is only high during early\ninterglacials and ranges from ~ 1-10 g/cm2/kyr. Conversely Asian dust is lower during interglacials\nand flux to the NW Pacific (still 1000’s of km upwind of Stoneman Lake) never gets higher that 1\ng/cm2/kyr. Long-range transport of dust from Asia and Africa certainly occurs, we see it in the\nmodern, however, it occurs in quantities that would be barely perceptible here compared to influx\nof medium- and short-range dust and local alluvium. We explain this reasoning in lines 181-190.\n____________________________________________________________________________________________\nLine 132: write in full STL\nStoneman Lake is now written out in full where it appears.\n____________________________________________________________________________________________\nLines 143-145: please explain “cannot be controlled by intervening processes of transport and\ndeposition”. Who controls what? What is intervening what? Is the MRT interpretation impossible to\nvalidate?\nClarified in lines 210-226.\n____________________________________________________________________________________________\nLine 155: it would help if the authors write more to a general audience also by more explicit\nexplanations. Here it is assumed that people know what is ‘wet removal’, that the glacials have the\nhighest effective moisture.\nClarified in lines 212-213. We cite lake depth in Fig. 3f to support that glacials have highest\neffective moisture (lines 221-224).\n____________________________________________________________________________________________\nLines 154-156: isn’t this partially a circular reasoning? First, it is assumed that a certain grain size\nclass is purely dust, and then, because there is higher dust flux, there is not much wet removal?\nLines 138-159: We believe our interpretation that EM 3 and 4 are dust is strong enough that the\nreasoning here isn’t circular. Geomorphology and geochemistry/mineralogy of soils in the lake\ncatchment has been done in a previous study (Staley et al., 2023). We showed that both soils and\nlake sediments are a mixture of locally sourced minerals (dominated by albite, smectite and\nkaolinite, and ilmenite) and dust (quartz, illite, and zircons). We have tracked local inputs using Ti\n(from ilmenite), fine dust using Rb (from illite), and coarse dust using Zr (from zircons). The\ngeochemical ratio tracing the relative contribution of local derived material to dust (Ti/Zr+Rb)\nparallels that of EM 1&2&5 to EM 3&4 (Fig. S5). Likewise, the geochemical ratio tracing the relative\ncontribution of coarse to fine dust (Zr/Rb) parallels that of EM 4 to EM 3. Our interpretation is\nfurther supported by EM 3 (13 um) and EM 4 (38 um) being nearly exact matches of end members\n(13 and 34 um) in a nearby study (Tau et al., 2021) interpreted as fine and coarse dust.\n____________________________________________________________________________________________\nLine 159 SWNA?\nSWNA is defined in the introduction. We can write it out in full, or as SW North America (like the\ntitle) word count permitting.\n____________________________________________________________________________________________\nLine 159: Evidence ‘dictates’, not sure if that is really the appropriate academic wording.\nCorrected to suggests. Line 224\n____________________________________________________________________________________________\nLine 162: I propose to include the grainsize mode also in between brackets, SRT, EM-4, 38 micron).\nParticularly the grainsize is what helps the reader to memomize the data and grains, EM-4 is\ndifferent for every study, as is SRT.\nWe have incorporated this suggestion where appropriate.\n____________________________________________________________________________________________\nLines 163-164: this should be in the Results. And, looking at Figure 4, there is no mention of SRT, so\nwhere should I look?\nMoved to results (line 160-177). EM 4 (SRT/Verde Valley dust) is a significant part of this revised\nmanuscript and discussed in lines 284-341.\n____________________________________________________________________________________________\nLines 166-167 Please explain “whose published depositional ages correlate to MARsrt increases”.\nClarified. Lines 298-300 and Fig. 7b\n____________________________________________________________________________________________\nLine 177: SWNA in the title is not very explanatory to a wider audience\nChanged to SW North America (line 221)\n____________________________________________________________________________________________\nLines 208-209: I do not see this in Figure 3: the transition from MIS 6 to 5 is rapid in the Desert Dust\ncurve given, where is the 20kyr lag?\nClarified. Lines 258-261 and Fig. 5a\n____________________________________________________________________________________________\nLines 232-233: Provide the reader means to find this in the figure, you mean to look at c, d, and e?\nRelating the tiny spike at 7>6 transition seems too far, the overall agreement in trends between b\nand c/d/e is, however, worthwhile more reference.\nPart about brief spike removed. Substage a, b, c, d trends are discussed in lines 262-274 and their\nboundaries are now indicated in Fig. 5.\n____________________________________________________________________________________________\nLine 258: The lack of a sustained vegetation cover in glacial times is a primary reason for increased\ndust fluxes, or do the authors include that in the ‘dust production’?\nThank you for the comment – in fact this is the opposite and we need to clarify this in the\ndiscussion. Glacials = more veg/less runoff = less dust (Lines 228-247).\n____________________________________________________________________________________________\nLines 260-263: there must vegetation records for comparison to corroborate this claim?\nThere are. We have included a included reference to Betancourt (1990) in Line 246.\n____________________________________________________________________________________________\nLines 266-267: Figure 5 gives a clear lower STL MARsrt for the mid-Holocene compared to Early\nHolocene and Late Holocene, that is not suffice?\nSee Lines 275-283 and Fig. 5a\n____________________________________________________________________________________________\nFigure 2: why are the real data hidden behind the end-member analyses? Choices for line thickness\nare such that the real data are not easy to trace in the figure.\nWe have addressed this in Fig. 2 with an a panel showing raw data and b panel showing end\nmembers.\n____________________________________________________________________________________________\nFigure 4: I find this figure / table hard to read, it could be my age, but it all seem rather small,\nparticularly because the red outliers need so much space that the averages and 2.7sigma intervals\nare somewhere near the bottom of each panel. Would it be an option to leave the outliers for a\nfigure in the appendix and blow up this panel focussing on the main box and whisker plots?\nWe have incorporated your suggestions and focused Fig. 4. Thank you.\n____________________________________________________________________________________________\nFigure 4: I cannot find the paper nor Methods section what intervals are included in ‘Glacial’ and\nwhat in ‘Interglacial’. Same for Early, Middle, Late, add a description in the text / caption. It would\nhelp to indicate early, middle, late also to Figure 3 on the time axis. While dividing into glacial /\ninterglacial seems evident, it may not necessarily be. One could argue to only compare Stage 1 and\n5e with Stages 2,3, and 6. Or more indendant, a ‘cutoff’ could be used on the LR04 isotope curve to\ndecide which data point bins in what stage, glacial or interglacial. It may make the results more\nsignificant and definitely more independent.\nClarified in the Figure 4 caption. Figure 4 has also been streamlined to highlight the most important\nintervals. Glacials and interglacials are defined in Lines 164-169. Early, middle, and late Holocene\nboundaries are indicated in Figs. 3, 7, and 9.\n____________________________________________________________________________________________\nFigure 4: labels ‘e’, ‘abcd’ are unclear, these all belong to MIS5? It seems there is space on the\nimage to show that.\nFigure 4 has been streamlined so data on MIS 5abcd is no longer presented.\n____________________________________________________________________________________________\nReviewer #2’s comments (italicized) and our responses:\nIntroduction: I do not see the tight connection of the research topic and justification of scientific\nimportance in introduction. Ice cores and deep sea are great proxies for global dust budget. The\nimportance of American southwest to the global picture is quite vague here, and there is no critical\nknowledge gap or debates described to clarify the contribution of this study. The human impact on\ndust generation also seems not relevant given the study extends back to the late Pleistocene. I see\nthe importance at the end of the discussion, but here it is not appropriately sold.\nThank you for this perspective. We have revamped the introduction considering we now have\nincluded the full dataset in this revised manuscript (we have incorporated the manuscript that was\nsent to Geology. Now only this manuscript is under consideration). In a nutshell, SWNA lacks\ncontinuous and long-term dust and geomorphic activity records that may shed light on potential\noutcomes of rapid climate change. To the best of our knowledge, this study is the first of its kind in\nNorth America to continuously quantify both dust accumulation and hillslope sediment transport\nrates over glacial-interglacial timescales.\n____________________________________________________________________________________________\nBackground: the text lacks key description of the background (description of figure 1), particularly\nthe climate and atmospheric circulation patterns.\nWe have added this. See Lines 72-109.\n____________________________________________________________________________________________\nResults: 1) why choose five end members? Is this based on observation and sound geologic\ninterpretation or just math technique? I think it is the latter, which, in my opinion, does not have\ngeologic significance. I understand there is knowledge of modern dust source (like Tau et al.,\ngeology) that this study is based on, but the reasoning is not well clarified. 2) The explanation of\neach end member seems very casual. For example, how physical and chemical weathering affect\nthe minerals ton have EM1and EM5? I know the reference is cited, but such interpretation is the\ncore of the study and should be clarified here. 3) if EM 1 coalesces with EM2, what is the basis to\nseparate them?\nAnd\nHow does the geochemical data support? It needs some clarification.\nWe have clarified our model choice in Results (Lines 125-137) and in Methods (Lines 629-669). This\nchoice is based both on how the mathematical model fits the observed data and geologic\ninterpretation. We clarify the geochemical/mineralogical support for our chosen model in Lines\n138-159; 178-190. Below is a summary of our reasons to choose the 5 end-member model\nscenario and which sediment populations they represent.\nAnalySize, our end member modeling software of choice, automatically runs multiple scenarios\nthat fit 1 to 10 end members to the measured grain size dataset. It returns model performance\nstatistics along with PSD and percent composition in each sample for each modeled end member\n(Fig. S2). The best end member model scenarios for further examination were those that prescribed\n3, 4, and 5 end members (3EM, 4EM, and 5EM) because they have a total model fit r2 of ~96, 98, and\n99%, respectively, and exhibit little intercorrelation between constituent end members that would\nindicate model overfitting (Fig. S2ab). The first end member of the 3, 4, and 5 end member\nscenarios (3EM-1, 4EM-1, and 5EM-1) has a primary mode at 0.18 μm and one to two other\nsecondary modes in the clay to silt range (Fig. S2cde). 3EM-1, 4EM-1, and 5EM-1 also exhibit nearly\nidentical percent composition by depth (Fig. S2cde). The poly-modality of 3EM-1, 4EM-1, and 5EM-\n1 is consistent with locally sourced sediments (they are poorly sorted) and consistent results\nbetween scenarios indicates robust modeling. Moving on, 3EM-3, 4EM-4, and 5EM-4 are also\nsimilar in grain size distribution (single modes of 31, 42, and 38 μm) and stratigraphic variation (Fig.\nS2cde). These modes are consistent with short-range-transport dust (dust from <100 km away) and\na coarse dust end member (mode: 34 um) identified in sediments of Montezuma Well, AZ (25 km to\nthe SSW of STL), a lake that is downwind of the same dust sources (Tau et al., 2021). The main\ndifference between the 3EM, 4EM, and 5EM scenarios is how they model sediment populations in\nthe very fine to fine silt range. Unimodal endmembers in the fine silt range are consistent with\nmedium-range-transport dust (dust from 100’s of km away). 3EM-2 has a unimode centered at 9.5\nμm (Fig. S2c). If we interpret 3EM-2 and 3EM-3 as dust then there is no input of local alluvium\nduring interglacials MIS 7 or MIS 5e (Fig. S2c) which is contrary to geochemical and palynological\nevidence indicating quite vigorous sediment transport during these times (Jiménez-Moreno et al.,\n2023; Staley et al., 2023). In the 4EM scenario, particles in the very fine to fine silt range are split\ninto finer (4EM-2: 6 μm) and coarser (4EM-3: 13 μm) end members (Fig. S2d). 4EM-2 is interpreted\nas resuspended fine sediment from the lake margin (e.g., Arcusa et al., 2020), likely very abundant\nafter lake levels fall during early interglacials, explaining high abundances rates following glacial to\ninterglacial transitions during MIS 7, 5e, and the Holocene (Fig. S3). 4EM-3 is an exact match of the\nfine dust end member (13 um) from Tau et al. (2021). We ultimately chose the 5EM scenario\nbecause it is nearly identical to the 4EM scenario while adding a fifth (primary mode at 169 μm;\nsecondary mode at 19 μm) that improves model fit during a few time periods around 31 and 12 ka\n(Fig. S2e) when coarser material intercalates the lake stratigraphy. 5EM-5 is another locally\nsourced sediment population given its coarse and poly-modal PSD. In sum, the 5EM scenario\nmaximizes the variance accounted for in the model (Fig. S2ab and S4) and produces end members\nwhose particle size distributions compare favorably to those of other regional dust studies and\nwhose accumulation trends stand up to geologic interpretation.\nFurther support for the 5EM model and interpretations of end members is provided by comparison\nto mineralogical and geochemical analyses by Staley et al. (2023) of soils in the Stoneman Lake\ncatchment the very same lake sediment stratigraphy studied here (Fig. S5). We showed that both\nsoils and lake sediments are roughly a 50-50 mixture of locally sourced minerals (dominated by\nalbite, smectite and kaolinite, and ilmenite) and dust (quartz, illite, and zircons). We tracked local\ninputs using Ti (from ilmenite), fine dust using Rb (from illite), and coarse dust using Zr (from\nzircons). The geochemical ratio tracing the relative contribution of locally derived material to dust\n(Ti/Zr+Rb) parallels that of EM 1&2&5/EM 3&4 (Fig. S5). Likewise, the geochemical ratio tracing the\nrelative contribution of coarse to fine dust (Zr/Rb) parallels that of EM 4/EM 3.\n____________________________________________________________________________________________\nDiscussion: Section 1: 1) the evidence to rule out “processes of transport and deposition” is not\nclear; 2) Westerlies may be stronger during glacier maximum, what about monsoon? The evidence\nruling out wind intensity change is also not compelling. 3) cite reference and evidence for that the\nhighest effective moisture was during glaciers.\n1) We do not see increases in dust accumulation during periods we would expect to see transport\n(wind speed) and deposition (surface roughness and precipitation scavenging) processes positively\naffect accumulation rates (glacials). See Lines 210-226 for clarification.\n2) The monsoon question is interesting because strong convective cells likely play a role in\ndislodging and exposing fine sediment to wind erosion. However, according to Metcalfe et al.\n(2015) the NAM appears to strengthen during the mid-Holocene and this is not associated with an\nincrease in dust accumulation in our record.\n3) Line 219- Highest effective moisture indicated by lake depth (Fig. 3f).\n____________________________________________________________________________________________\n4) evidence for the different source of SRT and MRT?\nWe interpret different sources for SRT (EM 4, now called Verde Valley dust) and MRT (EM 3, called\ndesert dust) based on their different grain size modes and accumulation trends. See earlier\nresponse.\n____________________________________________________________________________________________\n5) Anderson et al say that “fluvial aggradation beginning during full-glacial times and continuing into\nsubsequent interglacial”, is this consistent with the observation of SRT?\nYes, see Lines 322-331.\n____________________________________________________________________________________________\nSection 2: line 177-179, this observation is limited to mid-latitude, right? How about desert, why\nthat is not included given desert to the north and northwest of China loess plateau has been\nsuggested to be a source.\nThis observation is for SW North American deserts and we have ruled out Asian sources. Clarified\nLines 252-254.\n____________________________________________________________________________________________\nLine 181, the transition from alluvial source to desert is very confusing.\nAlluvial sources are found in the desert. This is clarified in Lines 248-261.\n____________________________________________________________________________________________\nLine 182, if I understand right, this is for MRT, why not replace “fine” with the grain size for clarity.\nThis part of the manuscript was removed, and efforts were made to clarify the different modes of\neach EM where appropriate.\n____________________________________________________________________________________________\nAny evidence of production of this grain size range at desert hillslopes?\nFrost weathering, fluvial and alluvial comminution, and erosion of siltstones are all capable of\nproducing silt sized grains from desert hillslopes (Smith et al., 2002; Muhs, 2013). MRT (“desert\ndust”/EM-3: 13 um) is consistent with regional dust in both modern and paleo records (Reynolds et\nal., 2016; Routson et al., 2016; Arcusa et al., 2020; Tau et al., 2021).\n____________________________________________________________________________________________\nline 194 and 197,it is not clear what are the climate-driven surface processes, and how they were\ncontrolled by climate and ecological changes.\nThis discussion has been completely rewritten. See Lines 228-283.\n____________________________________________________________________________________________\nLine 209, I thought with the stage set up earlier in this paragraph, here you want to talk about the\nslope instability during the interglacial, not sure why you change to talk fluvial adjustment to\nsediment load increase?\nThis discussion has been completely rewritten. See Lines 228-283.\n____________________________________________________________________________________________\nLine 261-263, this seems different from what has been said earlier. Is this a comparison of glacier\nmaxima to the rest of the glacier periods? I think the information provided so far is that glacier is\nless dustier than interglacial.\nClarified in Lines 237-247. We discuss glacials as a whole, not variability within glacials.\n____________________________________________________________________________________________\nI think the rest of the discussion is good and interesting, but they are based on discussion in the\nfirst two sections. The lack of evidence and clarity in the first two sections undermines the\nextended discussion.\nWe hope to have added enough clarity and justification of our interpretation of end members to\nallow this discussion, which has itself undergone significant revision.\n____________________________________________________________________________________________\nReviewer #3’s comments (italicized) and our responses:\nKey points:\nThe central inconsistency of this paper is the lack of granulometry data from the surrounding small\ncatchments to identify local water-transported flux of particles versus aeolian dust flux. There\nneeds to be a detailed study of the source to sink flux of particles from numerous sources around\nthe lake including catchments, overland flow, and aeolian proximal and distal sources. What is the\ngeomorphology and soils around the lake? Vesicular A horizons, a common desert soil morphology,\nare loaded with aeolian particles, ripe for erosion and reflect storage of aeolian particles on the\nlandscape, not a primary aeolian flux.\nGeomorphology and geochemistry/mineralogy of soils in the Stoneman Lake catchment was\naccomplished in a previous study (Staley et al., 2023). Soil storage is limited to glacial maxima (Fig.\n7d) as the catchment is small, steep, and dominated by alluvial/colluvial soils categorized as\nargiustolls (no Av horizons). Furthermore, the lake surface itself accounts for ~20-25% of the\nbasin’s total area suggesting that even during glacial maxima, a primary dust signal is still present.\nLines 138-159. Both soils and lake sediments are an even mixture of locally sourced minerals\n(dominated by albite, smectite and kaolinite, and ilmenite) and dust (quartz, illite, and zircons). We\nhave tracked local inputs using Ti (from ilmenite), fine dust using Rb (from illite), and coarse dust\nusing Zr (from zircons). The geochemical ratio tracing the relative contribution of locally derived\nmaterial to dust (Ti/Zr+Rb) parallels that of EM 1&2&5 / EM 3&4 (Fig. S5). Likewise, the geochemical\nratio tracing the relative contribution of coarse to fine dust (Zr/Rb) parallels that of EM 4 / EM 3.\nWe have included granulometry of soil samples from a fairly flat and small surface just north of the\ncatchment (Fig. 2a). It has a similar particle size distribution as lake sediment and therefore seems\nto be a mix of similar end members (local weathering products and dust).\n____________________________________________________________________________________________\nIt would be informative to contact PI-SWERL person, in tuned with aeolian particulate sources in\nthe SW to provide a fuller assessment of the conditions of aeolian flux, related to source, sediment\navailability and threshold wind speed.\nNumerous studies indicate that active alluvial fans and river floodplains are the primary sources of\neolian sediment in the southwest (Sweeney et al., 2013; Bullard and Livingstone, 2002 and\nreferences therein). Threshold windspeeds are very likely met over the longer (decadal-centennial\nto millennial) timescales that concern this study (Reheis, 2006).\n____________________________________________________________________________________________\nThe far-travel dust sources should have a different mineralogic signature than local sources.\nThere is a distinct mineralogical difference. Dust is dominated by quartz and illite. Local sediments\nare dominated by albite and ilmenite. See Staley et al. (2023) and Lines 138-159.\n____________________________________________________________________________________________\nThere needs to be more data to support the aeolian flux premise of this paper; it is not overly\nconvincing, at least to me.\nSee lines 138-196\n1) Mineralogy of lake sediments indicates the clastic fraction of lake sediments is ~50%\nquartz, illite, and zircon and ~50% ilmenite and albite (Staley et al., 2023). Quartz, illite, and\nzircon must be allochthonous given the catchment’s alkali basalt bedrock. End member\nmodeling reflects this even split with dust end members (EM 3 and 4) accounting for 46% of\nthe total clastic sediment column analyzed and locally sourced end members accounting\nfor 54%. Lines 138-154; 178-190.\n2) We have tracked local inputs using Ti (from ilmenite), fine dust using Rb (from illite), and\ncoarse dust using Zr (from zircons). The geochemical ratio tracing the relative contribution\nof locally derived material to dust (Ti/Zr+Rb) parallels that of EM 1&2&5 / EM 3&4 (Fig. S5).\nLikewise, the geochemical ratio tracing the relative contribution of coarse to fine dust\n(Zr/Rb) parallels that of EM 4 / EM 3. Lines 152-154; 187-190.\n3) EM 3’s13-um mode and unimodal particle size distribution is consistent with dust that has\nbeen transported 100’s of km. A similar study done 25 km SSW has a 13-um mode end\nmember interpreted as regional dust (Tau et al., 2021). Presumably these two basins are\ndownwind of the same sources. EM 3’s accumulation rate correlates with climatic/ecologic\ndestabilization and movement of hillslope sediment stores onto downslope alluvial\nsystems across the SW North American deserts. Active alluvial systems are recognized as a\nmajor source of dust.\n4) The 38-um mode and unimodal particle size distribution of EM-4, which we interpret as the\ncoarse dust component, is consistent with dust that has been transported < 100 km. Its\naccumulation rate correlates to aggradational episodes of the Verde River and its axial\nalluvial fans. Both recognized as major sources of dust.\n____________________________________________________________________________________________\nAlso, the sedimentation rates and dust flux are low to very low particularly from 30 to 12 ka, which\nindicates that this system has low sensitivity to aeolian flux?\nI think this suggests that flux is low, not that the system is insensitive. The lake surface accounts for\n~20-25% of the basin’s total area suggesting a primary dust signal is always present.\n____________________________________________________________________________________________\nI question what the low variability in aeolian flux from nearly zero to ~1.5 g/cm/ka at ca. 130 ka\nactual reflects and is this low variability significant?\nThere is actually high variability in eolian flux starting at this climate transition ca. 130 ka and it\nprobably relates to activation of regional sources each with slightly different thresholds for change.\nWe interpret the lower flux and variability prior to that to reflect stable land surfaces during the\nprevious glacial (high vegetation coverage and low runoff) (Lines 237-261).\n____________________________________________________________________________________________\nIt would be helpful to assess the current aeolian flux around Stoneman Lake; is this area sensitive\nto current dust sources?\nThere is broad similarity between modern and paleo dust accumulation rates observed here and at\nother sites throughout the region (Fig 4ae).\n____________________________________________________________________________________________\nWhy are the early Holocene rates (11-9 ka) of dust flux, when many pluvial lakes existed, though at\ndeclining levels, so much higher than 5e and stage 7. Something is missing in explaining these state\ndifferences in aeolian flux between Stage 1, 5 and 7, suggesting non-analogous aeolian sources\nand sinks.\nWe do not believe that the dust fluxes are substantially different amongst these interglacials as\nthey are the same order of magnitude. Given the larger number of age tie-points in the Holocene\nrelative to MIS 5 or MIS 7, the Holocene will appear to have greater variability in flux rates. With a\nnecessarily smoothed age model for MIS 5 and 7, the dust fluxes will appear steadier being\naveraged over longer time periods.\n____________________________________________________________________________________________\nLastly, a recent detailed climate model of the last interglacial in the SW USA demonstrated a\ndichotomy in precipitation between Arizona and New Mexico/TX with Arizona much drier than to the\neast (Insel and Berkelhammer, 2021 in J. Quat Science), with a warmer Gulf of Mexico, potentially\nenergizing the NA Monsoon. In this analysis there would be a dynamic boundary between moisture\nsources from NA Monsoon and Equitorial Pacific, particularly in the summer and how aeolian\nflux would be governed in the SW USA remains an open question. More data and climate modeling is\nsurely needed.\nThat is an interesting point. Unfortunately, our data does not resolve specific atmospheric vectors\nresponsible for dust transport. All we can say with confidence is that dust is reaching the SW edge\nof the Colorado Plateau from points south and west following prevailing zonal (winter-spring)\nand/or meridional (summer-fall) wind directions.\n____________________________________________________________________________________________\nAuthor’s Response - NCOMMS-24-02264B\nComments are italicized and our responses are in regular font.\nComments from the Editor:\n“…the writing needs improvement and more information about the geologic background and the\nsource to sink flux of the particles is needed.”\nThe manuscript has been nearly completely restructured and rewritten with a focus on clarity\nincluding important aspects of the geologic background. For instance, Figure 1 now includes a\nschematic of Northern Hemisphere dust transport to provide a global context for the study and a\nmap of regional Quaternary deposits illustrating the broad distribution of potential dust sources in\nsouthwestern North America. Key features of the Stoneman Lake catchment that make it an ideal\ndust trap are retained at the end of the Introduction (lines 52-55) and previous mineralogic\nevidence for significant dust in the record is clarified early in the Results section (lines 68-74). Our\nreasoning for which source-to-sink processes are primarily responsible for flux rate variability, i.e.,\nemission vs. transport vs. deposition, has been clarified in the Discussion (lines 291-316).\n____________________________________________________________________________________________\nComments from Reviewer #1:\nMy current opinion is that I do not think the paper writing has matured yet. My advice is to ask the\nauthors to considerably improve the clarity of writing by focussing on the key message of each\nsection and paragraph in simple words and by that making the article much shorter with less\nfigures. All sections and the figures of the paper are not highlighting the key findings and key\nmessage and lack easy overview of important messages from explanation of these. Regularly, the\npaper reads like a review paper more than a Nature Communications paper. You may consider my\nopinion as to be mostly important from the scientific point, I still bring a bit more detail here to the\nwriting style and presentation, as that is also an important aspect to the science communication\nwhich an article is. The title is too general, the abstract not bringing the key points in a direct\nmanner, the introduction is not specific enough, the discussion is often too much written like a\nreview and the figures bring a lot of points and data, some of which are hardly used and others\ncould be better merged. Two model figures are brought that should be merged and simplified, as it\nseems, and the same seems valid for some of the data figures. This may become a key paper on the\ntopic if the key message is brought readily and straightforwardly from the beginning (title and\nabstract).\nWe very much appreciate the comments and suggestions provided by Reviewer #1, especially with\nregard to improving the writing and narrative flow of the manuscript. Following their suggestions,\nthe manuscript has been nearly completely restructured and rewritten with a focus on clarity. This\nincludes revising the Title and Abstract to focus on the key finding(s) of the study and streamlining\nthe Introduction. In addition, we have made the Results and Discussion sections more distinct. The\nDiscussion now maintains focus on interpreting the results, only providing the context, rather than\nreview, of previous research.\nReviewer #1’s comments on the figures led to great improvements. Figures were significantly\nupdated with multiple mergers and restructurings meant to make the figures more concise and\nhighlight key findings. For instance, the two model figures were merged into one, as have the\nfigures presenting the accumulation rates for fine dust, coarse dust, and local alluvium, see below.\n____________________________________________________________________________________________\nLine 1-2 It seems the \"Hillslopes to dust\" part of the title is a bit confusing as hillslopes can be dusty\nthemselves, and the total title does not hold the key finding of the paper, which would make it\nattractive, now the title is a more a sort of review without big excitement.\nTitle has been changed to refer to the key finding of the paper.\n____________________________________________________________________________________________\nLine 11 rivers are part of alluvial systems and so fluvial systems are part of alluvial systems while\nnot all alluvial systems are fluvial. Find better wording or explain?\nThis sentence was removed.\n____________________________________________________________________________________________\nLine 10-32 It is needed to read the Nature Bold Paragraph guidelines to improve the abstract. There\nis no key research question explained rather than 'Understand the geomorphic impacts of climate\nchange' which is too general, what exactly do we still need to know? The methodology (end-\nmember, STL-14, sediment core) nor abbreviations (SWNA, STL) make it less attractive. Writing\nshould be more direct and concise, rather than first explain the interpretation (line18-19) first come\nwith the finding (line 19-20) and then find out time is up to explain it (delete line 18-19 from the\nabstract) and explain the main text.\nand\nLine 25-27 this is the key finding, right? Why is it only there, not in the title, not early in the abstract?\nTo make it attractive and clear to the reader what has been found new compared to earlier studies,\nbring this directly and then explain this key finding in the remainder of the paper.\nand\nLine 28-30 is there immediate and direct evidence for this in this work? Then it is also a second\n(subordinate?) key finding, right?\nand\nLine 30-32 could be very important, third, subordinate, key finding? Not being exactly expert in the\nfield of the authors, while having worked quite a bit with long-term dust records, still, this is rather\nspecialized knowledge, that could be in the abstract, but importantly then it needs more\nexplanation or different, simpler wording. It is a general journal this is sent to, not a specialistic one.\nFollowing these suggestions, the abstract has been rewritten more concisely and highlights the key\nfindings of the paper.\n____________________________________________________________________________________________\nLine 61 One could also start the introduction with line 61 and leave the first two paragraphs for a\nreview paper, it gives space in the article for more direct text, such as, in particular also for specific\nmissing knowledge to the general statements given in Lines 67-71. What exactly is missing due to\nthese long-term records are 'largely' absent? What means largely absent? There are no references\ngiven with the statement, why not? There are records it suggest, what do these show?\nThank you for this comment. The introduction has been streamlined considerably with specific\nreferences to important knowledge gaps and how this research helps to fill them.\n____________________________________________________________________________________________\nLines 72 - 123 these are a mix between rationale, introduction and methods. I would not write it the\nway it is done now, as it combines the study sites and methods with explanation of what these sites\nmean in terms of environment and how these records may be interpreted. But because the records\nare not yet there, the reader has to remember a lot of things, while the exact same reasoning will\ncome back in the article when the data are interpreted. So, most text is duplicate. I would skip this\nreasoning here, refer to the methods for the study site specifics, and use the space here to provide\na longer introduction to the work setting the research questions in the frame of the state-of-the-art\nknowledge with only a minor 'approach' paragraph.\nAs mentioned above, the Introduction was streamlined considerably based on these comments.\nMuch of the information provided does indeed come back later in the manuscript after our data is\npresented. We eliminated this unnecessary repetition.\n____________________________________________________________________________________________\nLines 124 Results: Most of the results are followable and logically written in order. An outsider has,\nhowever, to push all gas and release the breaks to keep up with the matter. This could still be\nimproved by starting paragraphs with more easy phrasing of the main finding presented in that\nparagraph without abbreviations. As example, lines 138-140, have an explanation to something the\noutsider does not yet comprehend and they are thinking 'why do I read this?'. Next lines, bring the\nkey finding of this paragraph: \"46% of the total clastic sediment volume is interpreted as being\neolian dust\". If the latter would be the first line, the reader would know why to read the explanation\nof this finding in the line after that one. Another way, in general, to write more clear is to shorten\nparagraphs to one message per paragraph (the first line) and two-three (max. four?) lines\nexplanation and then start a new paragraph with a new, next message, etc.\nThis is a great point. We now include simple topic sentences before each paragraph in Results\naimed at enhancing the clarity and flow of the section.\n____________________________________________________________________________________________\nLines 197 onwards Discussion: the Discussion suffers from the same needed improvement in\nwriting clarity as the Results. As example, line 224-225 bring the key results of a long section of\nreasoning. I would turn this completely around to let the reader know directly what comes out and\nthen explain this, particularly if this is done in the 'short-paragraph' style explained above, it will\nconsiderably help readability. It could be in steps to go through a certain reasoning, but I would not\nwait for the very end to come with the finding. And, turning it around likely also results in less\n‘review-style’ writing and more to-the-point reasoning resulting in less text.\nSimilar to the Results section, we now include topic sentences at the outset of each paragraph of\nthe Discussion. We believe the narrative flow of the Discussion has benefitted greatly.\n____________________________________________________________________________________________\nLine 228-230 is typically Introduction content and here I would come immediately with the finding:\n\"we find higher dust accumulation during peak interglacial conditions\". \"This is in contrast with…\".\nOr, \"the higher dust accumulation during peak interglacial conditions in … is in strong contrast to…\"\nto make it ever more short and to-the-point.\nUpon revisions, this point is now within a topic sentence of a paragraph found earlier on in the\nDiscussion (lines 144-145).\n____________________________________________________________________________________________\nLine 271 explain why it does not capture this\nThis is now clarified (lines 208 -209).\n____________________________________________________________________________________________\nFigure 1 why is the well site not indicated in 1C?\nFigure 1d now includes the core recovery site.\n____________________________________________________________________________________________\nFigure 3 I would think the global records can all go to Figure 5? And, instead better here to combine\nwith data in Figure 7? All data new in the paper in one figure?\nAll global records and the total dust accumulation rate time series from Stoneman Lake are\nincluded in a much neater and more concise Figure 4. Accumulation rates of fine dust, coarse\ndust, and local alluvium are combined into a single figure, Figure 6.\n____________________________________________________________________________________________\nFigure 6 and 8 to be combined? These schematics are very important to such papers, but the\ncomplexity is a bit too high it seems? And the need for two is not clear to me, apart from that a lot of\ntext is added into them, which could be done more schematically with T up (arrow) and P down\n(arrow). Clouds could be schematized into one cloud darker with thick rain or lighter with thin rain,\nto save space\nThe two schematics have now been combined into Figure 7 and schematized with less text overall.\nWe think this made the figure more accessible and impactful.\n____________________________________________________________________________________________\nComments from Reviewer #2:\nThis manuscript offers an interesting dataset and insights that could make a significant\ncontribution. The authors have significantly revised the previous version by adding grain-size data\nand details of end member analysis and have expanded the discussion to include how climate\nchange affected source terranes and dust production. The exploration of various dust sources and\ntheir changes in response to glacial and interglacial climates is intriguing. However, while the work\npresents some compelling ideas, it requires reorganization to clarify the reasoning process and\nideally the inclusion of new data to support key interpretations in the discussion. As currently\ninterpreted, the dataset may not justify publication in Nature Communications. After reorganization\nand strengthening the reasoning with evidence, the work could make a substantial contribution to a\ndiscipline-specific journal.\nThank you to Reviewer #2 for the helpful comments and suggestions, especially regarding\nincreasing the clarity of certain sections of the manuscript. We hope that improvements to the\nnarrative structure, reasoning, and additional focus on the global context have enhanced the\nimpact of this study.\n____________________________________________________________________________________________\nThe introduction and background information are currently combined in a way that causes\nconfusion. The interpretation of sediment sources for each dust grain-size fraction is crucial to this\nstudy, yet the manuscript treats this information as background without citing any references or\nrepeats data interpretation. This leaves readers wondering about the basis of this knowledge. I\nsuggest adding a section titled 'Geologic Background,' where the authors can introduce the study\nsite, describe the wind patterns, detail the bedrock compositions, potenital sources, and nearby\ndrainage systems.\nThis comment was key in our improvement of the manuscript. Per requests from both reviewers,\nwe have significantly streamlined the Introduction and Results sections. Much of the study site’s\ngeologic background in the previous version of this manuscript has been removed from the\nIntroduction. In the revised manuscript, we only include the most important aspects of the\ncatchment that make it an ideal dust trap in the final introductory paragraph. In the Results\nsection, the local bedrock is discussed within the context of previous mineralogical data that\nindicates the significant presence of dust and justifies our use of parallel geochemical data to\nassign sources for each sediment end-member. Remaining information about the regional setting,\nlike dust sources and transport pathways, are presented in the Discussion alongside associated\ndata interpretations. We believe this has resulted in large improvements and limited repetition of\ncertain pieces of information.\n____________________________________________________________________________________________\nResults seem like Results and Interpretation; it should be better streamlined.\nIn our revision, most interpretations that were made in the Results section have been moved to the\nDiscussion. Our attributions of end member populations to fine dust, coarse dust, and local\nalluvium remain because we believe it is well justified in the context of previous dust/erosion\nstudies and mineralogical/geochemical relationships.\n____________________________________________________________________________________________\nThe discussion that dust abundance only reflects sediment supply in source terrane is not well\nsupported.\nThis section (lines 292-318) has been restructured to better justify and clarify. It is important to\nnote that we are not making the argument that wind strength and wet vs dry fallout processes play\nno role in dust accumulation downwind, just that we find little evidence that they are the primary\ndriver of variability in the two dust end members. To better support our argument that wind strength\nor particular atmospheric phenomena are not controlling factors, we now propose and discuss the\nsupport for an alternative interpretation. In this scenario, fine dust (EM3) originates from the west\nwhere sources are slightly more distant and coarse dust (EM4) originates from the south where\nsources are slightly closer, a scenario that mirrors the interpretation of Tau et al. 2021 (see below\nfor further discussion on our differences of interpretation with this study). The westerly and\nsoutherly dust pathways would then be controlled by strengths of their associated synoptic\natmospheric circulation, westerlies and monsoons, respectively. Westerly circulation displaces\nthe monsoon during glacials (Bhattacharya et al., 2017), so we would expect westerly dust (fine:\nEM3) to increase relative to southerly dust (coarse EM4). We do not see support for this\ninterpretation in our dataset as the opposite pattern is observed.\n____________________________________________________________________________________________\nThe discussion about aridity and precipitation vs. moisture in glacial vs. interglacial period is\nconfusing.\nWe have made appropriate clarifications throughout the manuscript. Glacial periods are wetter\nthan interglacial periods in southwestern North America, it’s what makes this region distinct when\nit comes to glacial-interglacial dustiness trends! Perhaps there was some confusion about our\ndiscussion of strengthened monsoon during interglacials. The North American Monsoon does not\ndrive first order glacial-interglacial moisture variability; it is not strong enough to create long-lived\npluvial conditions like those experienced during glacials. Instead, we argue its main effect with\nrespect to dust appears to be its association with convective storms that produce intense runoff\nevents that can erode/re-expose sediments and cold outflow events that generate intense dust\nstorms (haboobs).\n____________________________________________________________________________________________\nLine 44-45, autogenic vs. allogenic processes, not clear what is specifically referred to in this\npaper. It will be helpful for readers if the terms in the subsequent sentences are linked directly to\nthese two terms.\nThis wording has been removed.\n____________________________________________________________________________________________\nLine 64-67, this sentence is correct but does not fit in here well for the writing does not extend to\nexplain why studying past dust record is relevant to changes induced by human activities.\nWe have added clarification on how long records are relevant context to human driven changes\n(lines 29-30)\n____________________________________________________________________________________________\nLine 73, rapid climate change only refers to glacial/interglacial cycles here, be specific.\nThis has been removed.\n____________________________________________________________________________________________\nLine 133, the 5 end members are not described.\nThe five end members are now described in detail in the Results (lines 79-84)\n____________________________________________________________________________________________\nLine 138, It is confusing to lump quartz with a clay mineral and a heavy mineral zircon together.\nRephrase to something as quartz accounts XX% (what is the link between quartz and basalt?), illite\nis the dominant clay mineral and it can not produced from weathering basalt, and abundant zircon\ngrains can not be from basalt.\nThis section has been rewritten for clarity (lines 68-74).\n____________________________________________________________________________________________\nLine 140, the connection between the two sentences is not clear. How do quartz, zircon and illite\nlink to EM3 ad Em5, are they mostly in this two end members? No evidence is provided.\nWe have clarified the mineralogical differences between lake sediments and local bedrock earlier\non in the Results section (lines 68-74). We then use geochemical stratigraphy (contextualized by its\nrelationship to mineralogical observations) to correlate with stratigraphic trends in end member\nabundance: Rb representing illite (fine dust – EM3), Zr representing zircon (coarse dust - EM4), and\nTi representing ilmenite (local alluvium - EM1+EM2+EM5). These geochemical indicators are used\nrather than direct mineralogical stratigraphy because our mineralogical analyses do not have\nsufficient resolution to compare directly to end member abundances. Geochemical plots\npreviously in the supplemental has been moved into Figure 3 to make these arguments clearer.\n____________________________________________________________________________________________\nLine 142-143, how about flow velocity? Strong vs. weaker wind.\nThe discussion on what the two grain size populations of dust represent, either a difference in\nsource distance or difference in mode/strength of transport has been moved, appropriately, to the\ndiscussion. According to the physics of settling dust particles discussed in Tsoar and Pye (1987),\nparticles larger than 20 μm are unlikely to travel more than tens of kilometers, consistent with our\ninterpretation that EM4 (38 μm) represents a nearby source. While an intense storm such as a\nhaboob may pick up greater numbers of large particles, these events are relatively short-lived\n(minutes to hours) and dust grains >20 μm quickly settle out. Particles <20 μm, however, are\ncapable of traveling 100’s of kilometers, consistent with the interpretation that fine dust (EM3) is\nregionally sourced.\n____________________________________________________________________________________________\nLine 181-190, why EM2 can not be dust with sources between those of EM3 and EM4? What is the\nrelationship between EM5 and Ti/(zr+rb)? EM2 peak is high, what about the element ratio is mainly\ndriven by EM2? Also can EM2 by the weathering product of EM3 and EM4 (thus ultimately dust)\ngiven that catchment soils have high EM3-5? Can EM5 be from episodic sandstorms?\nEM2 (5 μm) is smaller than EM3 (13 μm) and EM4 (38 μm), so it doesn’t make sense as an\nintermediate source.\nAll local clastic sediments likely contain ilmenite as it is the most resistant mineral present within\nthe local bedrock. Because most Ti in this system is likely derived from ilmenite (Staley et al.,\n2023), Ti is representative of EM1+EM2+EM5.\nEM2’s existence as an end member implies that its deposition trends are distinct. For instance, if\nEM2 were a weathering product of EM3 or EM4, it would be deposited contemporaneously and\nexhibit the same stratigraphic variability of those end members. Therefore, the end member model\nwould not identify it as a distinct grain size population and instead lump it in with one of those end\nmembers that would then either have a broader particle size distribution or exhibit two distinct\nmodes, the dust and the weathering product. Case in point, EM4 has a left shoulder in the clay to\nfine silt range (Fig. 2). The model inherently lumps the main modal peak and this shoulder because\nthey covary in the stratigraphy, suggesting that their deposition is controlled by the same process.\nTherefore, the shoulder is interpreted as former particle aggregates that were disaggregated post-\ndeposition, either from weathering, shallow diagenesis, or sample processing.\nEM5 is highly unlikely to be related to dust storms. EM5 has a main modal peak of 169 μm, fine\nsand. While fine and even medium sand has been documented as suspended load in intense dust\nstorms, these grain sizes represent the maximum and are unlikely to define the sandstorm’s modal\ngrain size distribution.\n____________________________________________________________________________________________\nFigure 3 has lots of information not mentioned in the text.\nWe undertook a major reorganization of figures to narrow their focus. Some elements of this figure\nhave been either removed (LR04) or moved to another figure (erosion rates). Figure 4 maintains the\nstraightforward comparison between the Stoneman Lake total dust record and other dust records\nfrom the Northern Hemisphere.\n____________________________________________________________________________________________\nLine 207, Tau et al say that “Particle-size distributions reveal fine dust transported during winter\nfrom the northwestern Sonoran Desert and the Mojave Desert and coarse dust transported during\nsummer from the southwestern Sonoran Desert, similar to current climate systems and dust\npathways.” Different from the argument that is cited for.\nThis has been corrected. While we agree with Tau et al.’s particle size results and interpretation\nthat there are two distinct dust populations in their record, we disagree that dust end member size\ndistributions can be directly linked to particle size distributions of dust sources and therefore\natmospheric circulation modes (Tau et al. 2021 Fig 2). All particle size distributions of their\npotential sources contain significant amounts of particles that could fit into either of their dust end\nmembers. Source particle size distributions only define what can be contributed to initial\nemissions, not what gets deposited after 100’s of kilometers of transport and gravitational sorting.\nFurthermore, the distances between their proposed winter and summer sources are small; it is\nunlikely that this small difference results in such distinct dust end member sizes.\n____________________________________________________________________________________________\nLine 220, Even the westerlies are stronger during glacier period, how about monsoon? McGee et al.\nsay “We demonstrate that a wide range of data supports wind gustiness as a primary driver of\nglobal dust levels”, which is exactly opposite to what the paper is cited to support.\nThis has been corrected and the reference has been removed. We note that McGee et al. does not\nconsider or incorporate data from North America in their study. As we show in this paper, the dust\nsystem in western North America differs clearly from the rest of the globe. We also clarify the\nglacial-interglacial variability in monsoon strength (lines 299-301).\n____________________________________________________________________________________________\nLine 221, do we know roughness should be higher or lower during glacial period?\nBased on the paleoecological study of Stoneman Lake by Jiménez-Moreno et al. (2023), we know\nthere was a denser forest canopy around the lake during glacials (lines 311-313).\n____________________________________________________________________________________________\nLine 233, appear to be influenced by global climate changes, is it specifically glacier-interglacial\ncycles? The reasoning flow is confusing here.\nThis specific statement has been removed and the discussion of global glacial-interglacial climate\nchange and how it impacts dust variability in southwestern North America versus elsewhere has\nbeen completely rewritten for clarity.\n____________________________________________________________________________________________\nLine 245, “wetter”, you said monsoon and tropical cyclones were suppressed, how come it\nbecame wetter or have increased effective moisture (what is that)?\nThis has now been clarified (lines 174-177). Compared to classic monsoonal regimes, the North\nAmerican Monsoon is relatively weak and not the primary driver of long-term effective moisture\n(Precipitation – Evaporation) variability in southwestern North America. Here, the main drivers of\nlong-term trends are temperature and precipitation changes resulting from glacial cycles. Cooler\ntemperatures and the steering of westerly-derived moisture by the Laurentide Ice Sheet increase\neffective moisture causing pluvial conditions during glacials. When the ice sheet retreats during\ninterglacials, this steering effect is removed, and temperatures increase leading to drier conditions\noverall, despite increased incidence of monsoons and cyclones.\n____________________________________________________________________________________________\nLine 295,” Verde Valley dust” is there any geochemical evidence to support the interpretation? This\nis an important component of the dust generation mechanism.\nUnfortunately not, although we have discussed some projects to examine this. In the place of\ngeochemical correlation of source and sink, we support the interpretation of EM4 as proximally\nderived dust using particle size dependence on transport distance, i.e., the majority of particles\n>20μm are unlikely to travel more than 10’s of kilometers, and temporal correlation between\ndepositional periods in the Verde Valley and increased coarse dust accumulation (lines 220-231,\nFig. 6)."}, {"round": 3, "reviewer_comments": {"reviewer_2": "This manuscript has undergone a significant transformation. My perception of the work and its significance has completely\nchanged after reading this version.\nThe work presents a long and high-resolution dust record from southwestern North America, providing valuable insights into\nthe complex interactions between dust generation, climate, vegetation, and erosion processes. This research is important\nnot only for the last 200,000 years but also has implications for the study of older loess, given that loess records extend\nfurther back into geological history. The manuscript is well-written, exhibiting a logical flow of reasoning. The figures are\nwell-crafted and enhance the reader's understanding. The methods section is sufficiently detailed, allowing readers to\nevaluate the uncertainty associated with the end-member analysis. Furthermore, the conclusions and interpretations are\nwell-supported by the data.\nI am very impressed with the scientific narrative and the authors’ ability to convey the story. I thoroughly enjoyed reading this\nwork and do not have any major comments, just a few minor suggestions to enhance clarity. While I hold a very positive view\nof this study, I would like to note that I am not a Quaternary geologist and may lack the expertise to fully evaluate the\nspecifics of Quaternary regional climate.\n1. In Figure 4, MIS 3 is indicated in light blue, please add a note in the figure caption to explain this distinction. Additionally,\nthe three proxies from the Chinese Loess Plateau, Japan, and the Northwest Pacific appear to be primarily influenced by\ndust production in Central Asia, raising questions about why this is considered a global flux. The dust curve from the East\nAtlantic shows significant differences compared to the other three proxies. It may be worthwhile to adjust the text in the\nrelated area, replacing \"global\" with \"other areas around the world,\" as the main point is that Southwest North America\ndiffers from these other regions concerning the causal relationship between climate and dustiness.\n2. In Figure 6, there are several climate proxies included. Given that the text may not have enough space to explain how\neach proxy indicates different climate conditions to support the interpretation, it would be helpful to annotate the figure to\nindicate warmer/cooler and drier/wetter conditions, particularly for δ18O. Additionally, since the text discusses 20 kyr cycles,\nmarking these cycles in the figure would enhance clarity.", "reviewer_4": "The Stoneman Lake core has an impressive ~230 kyr record of dust that has allowed Staley et al. to consider controls on\nglacial-interglacial timescales of dust flux. The conclusion that interglacials are dustier than glacials is an interesting one,\nand they link the dynamics of the eolian system back to climatic-driven changes in sediment supply. Tau et al. (2021) made\na similar conclusion for Holocene dust at nearby Montezuma Well, and so it is nice to see some broad agreement, although\nthe two papers differ on atmospheric controls and where the dust may have come from. I also think that geomorphologists\nwould expect that in some places, regional controls may counter global trends in dust emissions, and there is a strong case\nfor that here. Their end member modelling identified two distinct dust modes (EM3 and EM4). They found that the EM3 and\nEM4 modes are not always synced, suggesting a heterogeneous landscape response to climate change and dust\nemissions. I like this because regional dust sources are not controlled by an on-off switch, as is assumed in some dust\nemission models. The long geological record of dust as well as results that counter global trends in dust are significant\ncontributions and worthy of publication in Nature Communications.\nI think the paper reads well – it gets to the point and provides the key data to support their conclusion. This is my first review\nand having seen the author responses to the previous reviewer comments, I sense there have been a lot of improvements in\nboth the writing and figures. I can follow the figures that support their interpretations.\nI think the models and reasoning they present to explain the different grain size populations as identified though end\nmember modeling make sense, although I think some clarification is needed for EM4 coarse dust sources. The authors\nsuggest that the primary source of EM4 is the Verde Valley. They have identified the location of deposits on Fig. 1. They\ninclude several citations of maps and reports documenting these deposits (citations 54-60). However, they make an\nassumption that the Verde River deposits were a source of dust. Reviewer 2 posed a similar concern, and the authors\nreplied that no geochemical provenance analysis has been done to prove the linkage. Their assumption, and their model,\ncould falter if the river was gravel dominated in this location because they present no alternative source.\nSignificant fine grained deposits are required to warrant wind erosion and dust production. Do citations 54-60 identify fine grained fluvial\ndeposits? If so, this is not stated directly. The authors seem to assume the river would “periodically exposing fresh fine\nsediments to the atmosphere” without providing evidence of the fine sediment. If 54-60 document such fine deposits, say so\ndirectly. If not, or in addition to, consider checking the soil survey for this area. I was able to see the area highlighted in\nyellow on Fig 1 in soilweb-apps, where some of the area is dominated by sandy loams and other fine soils at the surface.\nConfirming the existence of fine grained (sandy) deposits makes their model seem plausible."}, "author_response": "Comments are italicized and our responses are in regular font.\nComments from Reviewer #2:\n1. In Figure 4, MIS 3 is indicated in light blue, please add a note in the figure caption to explain this\ndistinction. Additionally, the three proxies from the Chinese Loess Plateau, Japan, and the\nNorthwest Pacific appear to be primarily influenced by dust production in Central Asia, raising\nquestions about why this is considered a global flux. The dust curve from the East Atlantic shows\nsignificant differences compared to the other three proxies. It may be worthwhile to adjust the text\nin the related area, replacing \"global\" with \"other areas around the world,\" as the main point is that\nSouthwest North America differs from these other regions concerning the causal relationship\nbetween climate and dustiness.\nTo simplify, we have removed the light blue indicator for MIS 3 in Figures 3, 4, and 6 and instead\nonly indicate the strongest glacial periods in darker blue (MIS 2, 4, 6). To clarify, “Global DMARs”\nhas been changed to “Other Northern Hemisphere records of DMAR” within Figure 4.\n____________________________________________________________________________________________\n2. In Figure 6, there are several climate proxies included. Given that the text may not have enough\nspace to explain how each proxy indicates different climate conditions to support the\ninterpretation, it would be helpful to annotate the figure to indicate warmer/cooler and drier/wetter\nconditions, particularly for δ18O. Additionally, since the text discusses 20 kyr cycles,\nmarking these cycles in the figure would enhance clarity.\nArrows have been added to δ18O curves (b, c) to indicate wetter vs drier conditions. I have also\nadded arrows to i, the charcoal record, and k, the relative lake depth record. Within the figure\ncaption I have noted that MIS 5 and 7 substage boundaries generally align with 20-kyr precession\ncycles.\n____________________________________________________________________________________________\nComments from Reviewer #4:\nI think the models and reasoning they present to explain the different grain size populations as\nidentified though end member modeling make sense, although I think some clarification is needed\nfor EM4 coarse dust sources. The authors suggest that the primary source of EM4 is the Verde\nValley. They have identified the location of deposits on Fig. 1. They include several citations of\nmaps and reports documenting these deposits (citations 54-60). However, they make an\nassumption that the Verde River deposits were a source of dust. Reviewer 2 posed a similar\nconcern, and the authors replied that no geochemical provenance analysis has been done to prove\nthe linkage. Their assumption, and their model, could falter if the river was gravel dominated in this\nlocation because they present no alternative source. Significant fine grained deposits are required\nto warrant wind erosion and dust production. Do citations 54-60 identify fine grained fluvial\ndeposits? If so, this is not stated directly. The authors seem to assume the river would “periodically\nexposing fresh fine sediments to the atmosphere” without providing evidence of the fine sediment.\nIf 54-60 document such fine deposits, say so directly. If not, or in addition to, consider checking the\nsoil survey for this area. I was able to see the area highlighted in yellow on Fig 1 in soilweb-apps,\nwhere some of the area is dominated by sandy loams and other fine soils at the surface.\nConfirming the existence of fine grained (sandy) deposits makes their model seem plausible.\nThis is an important aspect to clarify. After reviewing the contained references (#’s 54-60) and\navailable soil survey data (AZ639, AZ641, and AZ643 surveys), we have confirmed that nearly every\nfluvial and alluvial deposit in the Verde Valley contains at least some fine-grained sediment (line\n229). We have also noted the Chemehuevi Formation’s fine-grained nature (line 244)."}]

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