the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 05 Feb 2024
New age constraints reveal moraine stabilization thousands of years after deposition during the last deglaciation of western New York, USA
Abstract. The timing of the last deglaciation of the Laurentide Ice Sheet in western New York is poorly constrained. The lack of direct chronology in the region has led to a provocative hypothesis that the Laurentide Ice Sheet re-advanced to near its Last Glacial Maximum terminal position in western New York at ~13 ka, which challenges long-standing datasets. To address this hypothesis, we obtained new chronology from the Kent (terminal) and Lake Escarpment (first major recessional) moraines using radiocarbon ages in basal sediments from moraine kettles supplemented with two optically stimulated luminescence ages. The two optically stimulated luminescence ages date the Kent (terminal) position to 19.8 ± 2.6 and 20.6 ± 2.9 ka. Within the sediment cores from both moraines, the lowest reliable radiocarbon ages range from 15,000–15,400 to 13,600–14,000 cal yr BP. Below these dated levels is sedimentologic evidence of an unstable landscape during basin formation; radiocarbon ages from these lowest sediments are not in stratigraphic order and date from 19,350–19,600 to 14,050–14,850 cal yr BP. The oldest radiocarbon age of 19,350–19,600 cal yr BP – from a rip-up clast – suggests ice-free conditions at that time. We interpret that the 5 kyr lag between the optically stimulated luminescence ages and the lowest reliable radiocarbon ages is the result of persistent buried ice in ice-cored moraines until ~15 to 14 ka. The cold conditions associated with Heinrich Stadial 1 may have enabled the survival of ice-cored moraines in permafrost until after 15 ka, and in turn, climate amelioration during the Bølling Period (14.7– 14.1 ka) may have initiated landscape stabilization. This model potentially reconciles the sedimentological and chronological evidence underpinning the provocative re-advance hypothesis, which instead could be the result of moraine instability during the Bølling-Allerød periods (14.7–13 ka). Age control for future work should focus on features that are not dependent on local climate.
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RC1: 'Comment on egusphere-2023-2655', Anonymous Referee #1, 03 Mar 2024
The manuscript by Prince et al provides a new chronological dataset that sheds light on a controversial hypothesis on the possible Allerød readvance of the LIS in western New York. It tests the hypothesis by using 41 radiocarbon ages from basal sediments collected in kettle holes in strategic places on the moraine. Overall the manuscript is well-written, and data support the conclusions. Besides some general comments, I have only a few minor comments that all are provided to improve the quality of the manuscript.
General comments:
1) The radiocarbon ages a given as ranges (min-max) throughout the text. Although this is the most correct way of reporting radiocarbon ages it makes the text less readable. I suggest that the min-max ranges are provided in the table and calibrated ages (in kiloyears) are used in the manuscript.
2) The "controversial" hypothesis should be presented in more detail in the introduction or geological setting. Now it is only briefly mentioned in the introduction and again in the discussion. It is very relevant to describe in detail how Young et al concluded that a readvance took place at 13 ka.
3) It would be worthwhile to consider making age-depth models for the records where there are many radiocarbon ages. This would allow a better assessment of the potential outliers mentioned in the text and also plot the proxy data on an age scale.
Minor comments:
Line 15: consider using another word than "provocative" - it gives the wrong impression. Maybe use an alternative instead of provocative
Line 19: ..luminescence ages..."of what?
Line 29: see the first comment about "provocative"
Line 50: More information is needed about how Young interpreted the radiocarbon ages (see general comment)
Line 69 (Fig. 1): Nice figure. Maybe add the existing chronological constraints mentioned in the text.
Line 173 (Fig 3): Nice figure but consider changing the yellow colour or increasing the line thickness.
Line 214 (Fig. 4): Overall good figure but panel A could be improved. The dimensions seem off and I wonder what the light brown colour below (a) represents.
Line 224: Ok descriptions, but it would be good to include the proxy data more in the description of the 3 units. In particular, MS, CaCO3 and water content could be better incorporated in the text.
Line 249 (Fig. 5): Good summary figure with proxy data from the sediment cores. In 15ABB7 MS is 0 - is that a mistake? Also, some LOI and water content data are missing in 20VIN4.
Line 317-321: Consider starting with summarizing new data before stating it supports the existing data.
Citation: https://doi.org/10.5194/egusphere-2023-2655-RC1 -
RC2: 'Comment on egusphere-2023-2655', Aaron M. Barth, 13 Mar 2024
Prince et al. (2024) – Peer review
GeochronologyThe submitted manuscript by Prince et al. presents new geochronologic data in the form of basal radiocarbon ages from kettle lakes and optically-stimulated luminescence (OSL) ages from glacial deltaic deposits to constrain the timing of the Kent and Lake Escarpment moraines – a Last Glacial Maximum (LGM) and recessional moraine, respectively. Results from these data are used to refine the timing of Laurentide Ice Sheet (LIS) deglaciation in western New York (NY) and address the proposed Allerød re-advance hypothesis (Young et al., 2020) which proposes re-advance of the LIS ~13 ka beyond the Lake Escarpment moraine.
The authors proposed a landscape evolution of kettle formation thousands of years after retreat of the LIS from the respective margins leading to a lag response in radiocarbon ages relative to the onset of deglaciation. The mechanism for the observed lag is attributed to the persistence of ice-cored moraines and permafrost across the Heinrich Stadial 1 cold interval followed by melting of the ice features during the abrupt Bølling warming leading to kettle lake formation. Interbedded coarse sediments amongst silt-dominated lake deposits are interpreted as periodic slumps of till during moraine stabilization.
The authors find no evidence to support re-advance of the LIS across the Lake Escarpment moraine and propose their new interpretation of landscape/kettle stabilization to explain the alternating coarse-fine sediments within the cores.
Overall, Prince et al. present compelling evidence to support their interpretations and conclusions. The results of this manuscript will advance the community’s understanding of western NY deglaciation and the mechanisms driving ice-sheet deglaciation. There is room for improvement within the manuscript itself including some organizational changes and clarification of certain arguments related to radiocarbon interpretation. However, should these issues be addressed by the authors it is my opinion that the submitted manuscript should be accepted for publication.
My comments for improvement are listed below as broad, sections-specific, and finer, line-specific comments.
Section-specific comments:
Section 3. There are no issues with the content of this section. However, many of the sentences start with the word “we” (e.g., “We collected…”, “We determined…”, “We returned…”, etc.) often in sequential sentences. I recognize that there is debate within the scientific community about the use of active or passive voice in writing, but for now the Methods section would read more fluidly if many of these sentences were changed to “Samples collected were analyzed for…” or “OSL analysis was conducted at…”.
Section 4.1. It's easy to get lost in the stratigraphic descriptions for each core in Section 4.1. It could be helpful for the reader to explicitly discuss each core based on the associated moraine, so it becomes easier to follow when the stratigraphy of a Lake Escarpment moraine core is being described versus a Kent moraine core.
Section 4.2. It could be helpful to declare the stratigraphic unit in which each basal age is found since that is not consistent across all cores. As an example, starting on line 264 the basal ages for the Kent moraine are described, yet the 15,050-15,550 cal yr BP ages from 20VIN1 are in Unit 2 just above the boundary with Unit 1, whereas the 13,00-14,050 cal yr BP ages from 15ABB7 are found in Unit 3. Clarifying this for all radiocarbon data in Section 4.2 will strengthen your argument and allow the reader to immediately associate the ages with their stratigraphic unit, at the same time setting up the stratigraphic discordance with older ages higher up the core.
Section 5.2. The second paragraph of Section 5.2 discusses the basal radiocarbon ages in relation to the timing of LIS retreat from the Kent moraine. It would be helpful to clarify you are referring to the ages from 20VIN1 located in Unit 2 just above Unit 1 which is interpreted as the glacial till. The description of “shortly before ~15 ka” needs to be changed to “prior to ~15 ka” as these are minimum-limiting ages on deglaciation and the duration between deglacial onset, as indicated as the stratigraphic change from Unit 1 to Unit 2, and the radiocarbon ages cannot be determined from these data alone. As such, there is not necessarily a contradiction between the young basal radiocarbon ages and regional correlations with the Lake Escarpment moraine ~17 ka. These results simply state that abandonment of the Kent moraine happened prior to ~15 ka and must have occurred prior to deposition of the Lake Escarpment moraine ~17 ka. Additionally, this interpretation of the basal radiocarbon age lends support to the eventual age-lag conclusion due to persistent ice and permafrost within the moraine.
Line specific comments:
Line 36: Consider revising. “Well constrained ice sheet chronologies…constrain”. Refine?
Line 93: Consider revising. “…dated to…by radiocarbon dating” is redundant.
Line 116: Define “significant” if you plan to describe the re-advance in this way.
Line 154: Was sediment bulk density only measured on the Little Protection cores? If so, why not on the others?
Line 283: Missing an end parenthesis after Olley et al. (1999).
Line 290: Consider using consistent terminology when discussing cores. Here you describe Vincent-1 when previously these cores were described as “20VIN1”. You could also include the associated cores in parentheses after “Vincent-1” for clarity.
Line 300: Careful with the word “probably”. This is an interpretation based on stratigraphy alone. A safer word to use here is “potentially”.
Line 301: Reiterate that core 21LPB1 is associated with the Lake Escarpment moraine.
Line 330: Clarify that “These samples…” refers to the macrofossils.
Line 336: Greater description is needed for how samples were assumed to be terrestrial origin. What visual cues were looked for to identify terrestrial vs. aquatic samples.
Line 348: Consider revising. The basal radiocarbon ages are trustworthy, but the up-core ages exhibit stratigraphic discordance and therefore do not reflect an accurate age of sediment deposition.
Line 364: The radiocarbon ages are from sediments stratigraphically above the glacial deposits therefore would not reflect moraine deposition. Do you mean “do not record deglacial onset”? A more accurate conclusion is reached on Line 425 “…radiocarbon dates can be extreme minimum age constraints on deglaciation.”
Line 366: Consider revising. “Ice cored moraines remained as such…” or “Moraines can remain ice cored for…”
References
Young, R. A., Gordon, L. M., Owen, L. A., Huot, S., and Zerfas, T. D.: Evidence for a late glacial advance near the beginning of the Younger Dryas in western New York State: An event postdating the record for local Laurentide ice sheet recession, Geosphere, https://doi.org/10.1130/GES02257.1 , 2020.
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RC3: 'Comment on egusphere-2023-2655', Anonymous Referee #3, 03 Apr 2024
Dear Editor,
Please find my comments for the paper entitled “New age constraints reveal moraine stabilization thousand of years after deposition during the last deglaciation of western New York, USA” by Karlee K. Prince et al.
This paper presents new geochronologic results using radiocarbon and OSL methods from kettle lakes and glacial deltaic. The main objective of this paper is to refine the timing of Laurentide Ice Sheet (LIS) deglaciation in western New York (NY) and re-evaluate a re-advance hypothesis around 13 ka proposed by Young et al. (2020).
The authors present a new series of chronological ages from cores taken from the basal sediments of moraine kettles, also supplemented by 2 OSL ages. The authors interpret the new chronological ages as recording a 5,000-year lag correlated with persistent buried ice in ice-cored moraines. This alternative model can reconcile previous chronological data with the re-advance hypothesis.
Major comments :
- The stratigraphy and sediment core chronology sections need some deep reworking. Indeed, I found these sections poorly organized, making it difficult to read and understand the results. The different cores are mixed in the text and the different units are not well defined. A better presentation of the data is important, as the position of the samples within the units is subsequently used extensively to correlate ages. Suggestions for improvement are included in my comments line by line in the “specific comments”.
- Radiocarbon ages should be placed in a chronological framework using chronostratigraphic models (in figure 5 or in the appendix) instead of just reported ages in a stratigraphic column as discussed in the main text. This should be easily done with Oxcal for example (using sequence or phase command…). Then we may have access to probability spectra, for individually calibrated and modelled ages. This would make it possible to better justify/approve the choices made by the authors to conclude that the ages are not those expected. This also allows them to better constrain the ages between the bottom and the top of the different cores. Maybe the radiocarbon ages will perhaps also be less rejected by the authors…
Specific comments
Line 99/100 : the 13,750-15,250 cal yr BP is from wood sample. This is an important point that may be more discussed later in the discussion section. Is the age calibrated against IntCal20 as your dataset? If not, it should be recalibrated and compared. This is also a general comment for all radiocarbon ages presented in the paper.
Line 204 : Please justify here why you applied a MAM age (bleaching problem) and also which model was used (MAM-3 or MAM-4 ?). What is the σb value used to calculate your MAM model? Also, even with a MAM age you may always over-estimate the depositional ages.
Line 224 from 247: I recommend presenting the data by units but also by separating Kent moraine and Lake escarpment moraine sites. They are far away from each other… In my opinion, correlating data and units separated by more than 50 km is risky.
To avoid any confusions, you should write a paragraph for the Kent moraine sites and the different cores and then another one for the Lake escarpment site.
# Chronology section should be organised as in figure 5 :
- Kent moraine with ages from VIN1 to VIN4, SONG1, 15ABB7
- Lake escarpment ages with 13DFK1 and 21LPB1
Line 265 : “For 20VIN3, 20VIN4, and 21SONG1, the basal ages cluster around 14,700 cal yr BP”. This sentence should be placed at the end of the section after a detailed review of the ages.
How do you calculate the mean age of 14,700 yrs? Did you use an oxcal model to determine a pdf age?
Line 265 : SONG1-age is taken from Unit 3 whereas VIN-4 and VIN-3 ages are from unit 2. Why are you mixing ages from different units? Your ages are maybe “basal” but are in different stratigraphic units. Please justify.
Line 266: “The basal ages from the Lake Escarpment Moraine are 15,000-15,400 and 16,650-17,350 cal yr BP.” Again, I strongly recommend not mixing here the two sites. This sentence and all data from Lake escarpment should be placed together, in another paragraph.
Line 267 : “The basal ages are not the oldest ages, however”. Please delete this sentence or rephrase it.
Line 270 : “Combined macrofossils …” : this is an important information that is not highlighted in the text and in figure 5. You should draw a different symbol for combined-fossils ages in figure 5, not only use stars. How many fossils are combined? Are they terrestrial or lacustrine?
Line 271 : “In 20VIN3, the basal age is 14,350-15,150 cal yr BP, yet combined macrofossils higher in the core, at the Unit 2/3 boundary, produce an age of 15,350-15,650 cal yr BP.” Again, these ages should go with the kent moraine.
Your basal age is from unit 2 and not from unit 3.
Again, you have a combined macrofossils sample, should be drawn with a different symbol.
Line 280 : the radial plots placed in Appendix may be placed on figure 4 on D and the field photo may be placed on Appendix.
Line 283 : Same comment made on line 204
Line 301 to 305 : I don't understand how you came to that conclusion. Please rephrase this part.
Line 306 to 314 : again this paragraph is hard to read. Maybe some rewording may be good there.
Line 317 : “The OSL ages support our estimated age of 25 – 20 ka for the Kent Moraine from prior literature and affirms our confidence in the age assignments using correlations of dated features elsewhere”. The sentence should be placed at the end of the paragraph.
Line 317 : “our estimated ages” : Why our? Please replace by the.
Line 317 : Also cite references for the “prior literature”
Line 321 : You should remember that they are MAM ages.
Line 322 : “The basal ages, taken at face value, indicate the deposition of the Kent Moraine occurred shortly before ~15 ka; this does not agree with our OSL age or the regional correlations”. Why? Please develop in the main text this conclusion. It is not a problem for me that lacustrine conditions occurred after the deposition of the sediments dated with OSL. Again, your OSL ages may overestimate the true age.
Line 324 : “contradicts the 17 ka age …”. Please cite the references here for this age. Based on which dating method? OSL, 14C or cosmogenic?
Line 338 : “We derived”: why derive? Use another word.
Line 339 : “fish bone”: again a missing information in figure 5 : Another symbol should be used for this sample!
Line 334 : “The macrofossil-rich rip-up clast in 20VIN1 holds evidence for two important interpretations: 1) the landscape was ice-free and at least sparsely vegetated as early as 19,350-19,600 cal yr BP (consistent with our OSL ages suggesting ice sheet retreat by 19.8 ± 2.6 – 20.6 ± 2.9 ka), and 2) the landscape stored this long-dead vegetation for thousands of years before it was redeposited.” This sentence is not in a good position in the text. I recommend placing the sentence on line 338 after “trustworthy age of 14,350-15,150 cal yr BP”
Line 415 : “The tundra zone is overlain by an interval with high spruce and pine pollen; this is the lowest unit found in the other five records (Miller, 1973; Calkin and McAndrews, 1980). This is likely reflecting the new forest biome associated with warmer temperatures”. Not well placed, I recommend moving it at line 411 after “complicates their interpretation.”
Line 428 : In 10Be dating you have potentially inheritance problems that may over-estimate the ages of moraines. The age gap needs to be looked at more carefully and is under-discussed in your paper.
Line 444: “The stratigraphically lowest radiocarbon ages from Unit 3 in the Lake Escarpment Moraine kettle basins, which are 15,000-15,400 and 13,600-14,000 cal yr BP, pre-date the ~13.1 ka re-advance suggested by Young et al. (2020) ».
And if all your radiocarbon ages were all reworked or contained some reservoir effects?
For the age of Young et al. : please remember on which kind of sample is based the age, piece of wood? You must discuss more here the data in my point of view.
Also, on line 99 an age of 13 750 – 15 250 yr BP is based on a piece of wood. How do you reconcile your data with these ages? On figure 2 this age is found really close to your site E , and looking your LPB1 section the ages look mostly in agreement, right? Your basal ages are close to those published ages. This may help…
Line 460 : Again the 5 kyr offset could be due to some unbleached sediments, you can not totally delete this option.
Figures :
Figure 3: Please indicate the core’s names in the insets close to the colored dots. It is hard to follow the position of the cores and the descriptions in figure 5 when you are not familiar with the area.
Figure 5:
Please use different symbols according to the samples (terrestrial, lacustrine, combined macrofossils, fish bone…)
A chronostratigraphic model with spectra may be much better than just calibrated ages.
Citation: https://doi.org/10.5194/egusphere-2023-2655-RC3 -
EC1: 'Comment on egusphere-2023-2655', Christine Hatté, 19 Apr 2024
dear authors,
The interactive discussion is now over. You have been informed that your responses to the reviewers' comments are due by May 9.
Three reviewers, experts in the fields you are investigating as part of the research you wish to publish here, have made comments and suggested areas for improvement. I strongly recommend that you follow their lead. Should this not be the case, I would be grateful if you could justify them point by point. I would like to draw your attention to the fact that it is all the easier to review your replies if they refer to the line numbers of the original manuscript and clearly state the changes you intend to make (or have made, if you enclose your replies directly with a corrected manuscript).
all the very best
Christine Hatté
Citation: https://doi.org/10.5194/egusphere-2023-2655-EC1
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