A global zircon U‒Th‒Pb geochronology database
Abstract. Since the start of the 21st century, the widespread application of ion probes has promoted the mass output of high-precision and high-accuracy U‒Th‒Pb geochronology data. Zircon, as a commonly used mineral for U‒Th‒Pb dating, widely exists in the continental crust and records a variety of geological activities. Due to the universality and stability of zircons and the long half-lives of U and Th isotopes, zircon U‒Th‒Pb geochronology can provide nearly continuous records for almost the entire history of Earth and is thus essential to studying the growth and evolution of the continental crust and even Earth system evolution. Here, we present a database of zircon U‒Th‒Pb geochronology that samples the global continental crust and spans nearly all of Earth's history. This database collects ~2,000,000 geochronology records from ~12,000 papers and theses and is by far the largest geochronology database to our knowledge. This paper describes the complied raw data, presents the relationship between dating error and zircon age, compares the error levels of different dating methods, and discusses the impact of sampling bias on data analysis as well as how to evaluate and weaken this impact. In addition, we provide an overview of the temporal and spatial distribution of global zircon ages and provide key insights into the potential research value of zircon ages for Earth system science, such as crustal evolution, supercontinent cycles, plate tectonics, paleoclimate changes, biological extinction, as well as commercial use in mining and energy. Overall, this collection not only provides us with a comprehensive platform with which to study zircon chronological data in deep time and space but also makes it possible to explore the underlying geodynamic mechanisms and evolution of Earth’s system and its astronomical environment.
Yujing Wu et al.
Status: open (until 06 Jun 2023)
RC1: 'Comment on essd-2023-20', Stephen Puetz, 18 Apr 2023
- AC1: 'Reply on RC1', Yujing Wu, 04 May 2023 reply
- RC2: 'Comment on essd-2023-20', Stephen Puetz, 04 May 2023 reply
RC3: 'Comment on essd-2023-20', Marthe Klöcking, 15 May 2023
- AC2: 'Reply on RC3', Yujing Wu, 26 May 2023 reply
Yujing Wu et al.
Yujing Wu et al.
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The U-Pb database discussed in this manuscript is certainly publishable, and it could provide the research community with valuable. However, at this point, I’m still unsure about its actual value for multiple reasons. Despite these concerns, I recommend publishing the database, but only after major revisions to the manuscript. The areas of concern are threefold: (a) using outdated and inaccurate methods for determining the best U-Pb age, which is more directly related to the degree of concordance than it is to the age-uncertainty, (b) concerns about the percentage of ages that have null values, these should be stated in the revised manuscript, and (c) significant grammar errors and/or poor word choices that will likely require a reliable editing service to correct. Further details related to these items follow.
Table at line 118: The database lacks key details, such as the 206Pb/238U, 207Pb/235U, and 207Pb/206Pb ratios and uncertainties, the depositional/stratigraphic ages, and many records have ages and GPS coordinates that are missing. Despite these deficiencies, the database still has considerable potential for solving outstanding geological problems, but less so than if all data items were completed. The authors should mention the percentage of records that have null values.
Lines 156-157: This sentence currently states: “Although TIMS is more precise, other methods are more efficient and widely used (Gehrels, 2014).” This is not the exact reason. Perhaps rephrase this as: “Although TIMS is more precise, methods such as LA-ICP-MS are more cost effective and thus are more widely used (Gehrels, 2014).”
Line 161-164: Using an arbitrary cutoff-age at 1000 Ma to select the best U-Pb age, as proposed in this manuscript, is flawed. Instead, Puetz et al. (2021) and Puetz & Spencer (2023) published a non-iterative probability method that (a) eliminates the artificial depression in the U-Pb age distribution at 1000 Ma caused by the arbitrary cutoff method, and (b) produces consistent age-distribution based on the degree of discordance without producing the artificial depression at 1000 Ma. It is suggested that the authors review these papers and mention these advantages, as discussed in detail in the references below:
Puetz, SJ; Spencer, CJ; Ganade, CE (2021). Analyses from a validated global U-Pb detrital zircon database: Enhanced methods for filtering discordant U-Pb zircon analyses and optimizing crystallization age estimates. Earth-Science Reviews 220, 103745. https://doi.org/10.1016/j.earscirev.2021.103745
Puetz, SJ; Spencer, CJ (2023). Evaluating U-Pb accuracy and precision by comparing zircon ages from 12 standards using TIMS and LA-ICP-MS methods. Geosystems and Geoenvironment 2, 100177. http://dx.doi.org/10.1016/j.geogeo.2022.100177
Line 183-185: Regarding the sentence: “Therefore, the amount of zircon production can be used to understand the past intensity of geological activity (Hawkesworth et al., 2010).” … Hawkesworth et al. (2010) is a poor reference to support this statement. Instead, the following reference is suggested:
Arndt, N; Davaille, A (2013). Episodic Earth evolution. Tectonophysics 609, 661-674. https://doi.org/10.1016/j.tecto.2013.07.002
Lines 185-194: These lines discuss the results in Figures 8 and 9. Importantly, the age distributions in these figures are raw age counts. The usage of raw age counts is less than optimal because it favors age peaks in heavy sampled regions while failing to show significant age peaks in sparsely sampled regions. For instance, age distributions from a database heavily populated with samples from China, as the database here has, will show strong age-peaks at 800 Ma and 2500 Ma. However, another database with minimal samples from China will tend to show a weak peak at 800 Ma, and a peak at 2700 Ma that is far stronger than the 2500 Ma peak. One way around this problem of disproportionate sampling is to weight the records inversely proportionally to the sampling densities. Then, the resulting age distributions will be remarkably consistent, despite the divergent sampling densities for each database. This suggestion is easy to test simply by first weighting the records inversely proportional to sampling densities, and then summing the age-counts by using the weights. For details about this method, refer to Puetz et al. (2017), Quantifying the evolution of the continental and oceanic crust, which is already in the reference list.
Line 212: Regarding the sentence: “At different geological times, the places where zircons grew in large quantities are also different.” This is already well known and is commonly referred to as the globally heterogeneous distribution of magmatic ages (Hawkesworth et al., 2010; Puetz et al., 2017; and many others). Suggest replacing this sentence by stating that the database here supports the globally heterogeneous distribution of magmatic U-Pb ages.
Line: 220: The authors propose a very subjective approach, with no details on how to accomplish adjustments for the different regional sampling densities. As already explained in the comments related to lines 185-194, the simple and standard approach to solving this problem is to weight the records inversely proportional to sampling densities.
Lines 252-254: The method that the authors propose here is seriously flawed, based on tests in Puetz et al. (2021) and Puetz & Spencer (2023) – which compared highly accurate and precise TIMS ages with LA-ICP-MS ages. Using 206Pb/238U ages for 0-1163 Ma; 207Pb/235U ages for 1163-2390 Ma, and 207Pb/206Pb ages when > 2390 Ma is a flawed system. Specifically, the magnitude of the uncertainty (the imprecision) is not directly related to the accuracy of the age. Read Puetz et al. (2021) and Puetz & Spencer (2023) for details about this method. Studies in those papers show that the best U-Pb age gradually transitions from the 206Pb/238U age at ~400 Ma to the 207Pb/206Pb age at ~1600 Ma. Between those points, the best age gradually transitions from ~400 Ma to ~1600 Ma based on a non-iterative probability model.
Line 290: Once again, the statement that “The zircon production peaks of the global continental crust are…” is biased by using raw age counts rather than weighting the records inversely proportional to sampling densities.
Lines 303-309: This regionally based approach is good, and in this instance, does not necessarily require weighting the records inversely proportional to sampling densities.
Lines 316-319: The age distributions (and thus the periodicities) for detrital, igneous, and metamorphic samples should be nearly identical. Again, if the authors recalculate the age distributions by weighting the records inversely proportional to sampling densities, then I suspect the periodicities will be essentially the same. Inaccurate age-distributions will produce incorrect periodicities. Another important requisite for testing periodicity is to de-trend the data. My question to the authors: Were the age-distributions de-trended prior to spectral analysis?
Lines 325-347: These are interesting studies that require more rigorous analyses to determine their reliability.
Lines 373-374: Regarding the sentences: “To solve hot data issues, Puetz et al. (2017) proposed the methods of grid-area and modern-sediment sampling using the surface area to weigh the zircon data. However, this approach is more suitable for studying the exposed crust than it is for studying the evolution of the crust.” … This statement is false and it is suggested that it be removed. Weighting records inversely proportional to sampling densities is a STANDARD approach (refer to references in Puetz et al., 2017). However, If the authors actually believe this statement is true, then the authors should present the test that they used to demonstrate this. However, I suspect this is an unsupported statement. For instance, numerous studies over the past 50 years have shown that the age distributions are remarkably similar regardless of depth or height. Parman (2015) shows similar findings – the age distributions remain remarkably similar over time (each involving samples of different depths).
Grammar related items:
Line 11: Grammar error / typo. Delete the words “and theses”
Line 14: Poor word choice. Suggest replacing the “weaken” with “minimize”
Line 17: Instead of mining and energy, is the intent to state: “mining and energy exploration”?
Line 45-46: As it is currently written, this sentence does not make sense, and in fact, is false: “However, in most cases, these zircon samples were used for independent regional studies and would probably not be used thereafter (Wu et al., 2019).” … In fact, over the past 20 years, numerous authors have re-used the data for these regional studies for further regional analyses and well as in global compilations for global analyses.
Lines 46-51: These lines should be deleted and rephrased in one sentence to state something like the following: Here, we expand upon previous global databases of U-Pb dated zircon, which could provide a means for enhanced academic and commercial geological analyses.
Line 62: Suggest deleted the unnecessary words at the end of this sentence “in which the earth is located”
Line 63-64 currently state: “However, if the amount of data is not sufficient, the resolution of zircon age series will be lower, leading to possible analysis bias. In addition, limited sampling locations will also affect the objectivity of statistics.” This sentence is too wordy and confusing. Thus, suggest making this clearer by simply stating something like the following: “Insufficient data with limited global coverage can affect results, which in turn can contribute to misleading interpretations.”
Line 67-68: Suggest deleting this sentence: “Undoubtedly, this database provides a more comprehensive and objective chronology data source on both the time and space dimensions for future earth system science research.” This interpretation is too strongly worded and even questionable. Only further independent studies (from research teams other than the current set of authors) will determine the usefulness of this global database.
Line 70: Suggest revising “other geological events and astronomical environments” to state “other geological and astronomical events”
From this point forward, I will no longer make suggestions related to grammar and interpretations. Even while the manuscript is generally understandable, it is riddled with grammar errors, poorly phrased sentences, and awkwardly phrased sentences. Therefore, it is suggested that the authors find a proficient proofreader or editing service to revise the entire manuscript to conform to standard English grammar and phrasing of words.
Line 268: Again, use the word “minimized” rather than “weakened”
I hope these suggestions help.
Stephen J. Puetz