Recent developments in analytical capabilities in the
field of in situ laser ablation mass spectrometry (LA-ICPMS) have expanded
the applications of U–Pb geochronometers in low-U minerals such as
carbonates or garnets. The rapid evolution of the technique relies on
well-characterized matrix-matched reference materials. In this article, we
explore the suitability of using carbonate as an “almost-matrix-matched
reference material” for in situ U–Pb dating of sulfates. For such purpose, we have used the astrochronologically dated gypsum and anhydrite samples deposited during the Messinian Salinity Crisis (5.97–5.33 Ma) and compared these dates with the U–Pb ages obtained by LA-ICPMS. Although the majority of the samples failed due to the elevated common Pb content and low 238U/204Pb ratios, five of the samples showed a higher dispersion
on U/Pb ratios. The obtained dates in four of these samples are comparable with the expected ages, while another gave an unexpected younger age, each of them with 6 %–11 % of uncertainty. The pit depth of the spots showed that the sulfates ablate similar to carbonates, so the offset due to the crater geometry mismatch or downhole fractionation can be assumed to be negligible. To sum up, the bias between the U–Pb and expected cyclostratigraphic ages, if any, is included in the uncertainty, and thus the results obtained here suggest that carbonate reference material is currently the best option for standardization of in situ U–Pb sulfate analyses.
Introduction
Recent developments in instrumentation and analytical capabilities of LA-ICPMS techniques have greatly expanded the applicability of the U–Pb
geochronometer. The high spatial resolution, low cost of analysis and high
throughput with relatively good precision (Schaltegger et al., 2015)
achievable with the new generation of laser and mass spectrometers favour
the study of minerals with low and heterogeneous U concentrations like
carbonates or garnets (e.g. Roberts et al., 2020). In fact, carbonate
geochronology has gone from scarce publications that involve tedious and
long-lasting isotope dilution techniques (e.g. Brannon et al., 1996;
Grandia et al., 2000; Woodhead et al., 2006, 2012; Rasbury and Cole, 2009) to
a bloom of dozens of publications per year (extensive review in Roberts et
al., 2020). Likewise, garnet U–Pb dating is rapidly developing in skarn and
metamorphic garnets, with U contents even below 100 ppb (e.g.
Burisch et al., 2019; Yan et al., 2020; Millonig et al., 2020). In addition,
several laboratories have started to investigate the possibility of
measuring other types of minerals: dolomites (Burisch et al., 2017),
fluorite (Piccione et al., 2019; Lenoir et al., 2021), nacrite (Piccione et
al., 2019) and anatase (Sindern et al., 2019), among others.
The rapid evolution of U–Pb dating in low-U phases is closely related to the
availability of reference materials (WC-1 carbonate, Roberts et al., 2017;
Mali garnet, Seman et al., 2017). Well-characterized matrix-matched
reference material is essential for U–Pb analyses by ion probe or laser
ablation as the sample matrix affects the ablation, transport and ionization
(Sylvester, 2008; Yang et al., 2018). Indeed, LA-ICPMS dates could only be
as good as the homogeneity of the reference materials and the accuracy and
precision to which such material is known (Schaltegger et al., 2015).
Several authors, however, have appraised the suitability of using
non-matrix-matched standardization with different levels of success. Deng
et al. (2017) and Wafforn et al. (2018) used 91 500 and GJ1 zircon,
respectively, to correct U/Pb fractionation of garnet and assumed they obtained the correct ages, whereas Yang et al. (2018) measured garnet ages 11 % too
old using zircon standardization. Similarly, Parrish et al. (2018) measured Mud Tank zircon within carbonate analyses and reported a
bias between zircon and calcite of ca. 4.7 %. Piccione et al. (2019) used
the WC-1 carbonate reference material for fluorite analysis assuming that
the bias between calcite and fluorite may likely be less than the one
between calcite and zircon.
This study aims to continue opening new possibilities in the field of
in situ U–Pb dating of low-U minerals by (i) demonstrating that sulfates
can be dated by U–Pb and (ii) examining the suitability and reliability of
using calcite as an “almost matrix-matched reference material” for sulfates.
Accurate U–Pb dating of sulfates could contribute to a better understanding of their formation and/or transformation (hydration–dehydration) with the
potential of dating diagenetic, pedogenic or tectonic processes. Gypsum
(CaSO4⋅2H2O) and anhydrite (CaSO4) are the two
most abundant sulfates of marine and non-marine evaporite deposits (e.g.
Murray, 1964; Babel and Schreiber, 2014). Sedimentary gypsum forms by direct precipitation out of water evaporation under arid climatic conditions in
hydrologically restricted environments. Under terrestrial evaporitic
conditions, gypsum is the dominant primary mineral, and anhydrite forms
through gypsum dehydration caused during diagenesis. In the presence of
water at shallower levels, the anhydrite is rapidly converted back to gypsum (e.g. Conley and Bundy, 1958; Murray, 1964; Ossorio et al., 2014; Warren,
2016). Although less frequent, non-evaporitic gypsum formation can also take place (see Van Driessche et al., 2019, and references therein).
In the absence of sulfate matrix-matched reference material, we have assumed that the bias between calcite and sulfate is smaller than with the other
available reference materials. Both minerals behave very similarly during
ablation (e.g. drill speed, U/Pb downhole fractionation) and
ionization in the plasma (Ca2+ as the main cation). For evaluating the
suitability of the calcite-based corrections, we have analysed gypsum and
anhydrite samples from the Messinian Salinity Crisis (MSC) in the
Mediterranean Sea (Roveri et al., 2014a, b; Vasiliev et al., 2017; Grothe et al., 2020; Andreetto et al., 2021) and compared them with their
astrochronological data (calibrated with astronomically tuned timescales,
such as Milankovic cycles, Laskar, 1999). Chronostratigraphy of late
Miocene to early Pliocene within the MSC is well constrained (CIESM, 2008;
Manzi et al., 2013; Roveri et al., 2014a) and thus makes those samples
ideal for comparison purposes.
Geological background
The Messinian Salinity Crisis (MSC, 5.97–5.33 Ma) successions record extreme fluctuations in the Mediterranean's palaeoceanographic and environmental conditions (e.g. Hsü et al., 1973; Krijgsman et al., 1999; Manzi et al., 2013). At the end of the Miocene, the Mediterranean's connections with the Atlantic Ocean were extremely reduced (e.g. Flecker et al., 2015; Krijgsman et al., 2018), whereas the freshwater supply from the eastern Paratethys increased (Flecker and Ellam, 2006; Krijgsman et al., 2010). Those palaeoceanographic changes led to the formation of hypersaline water bodies and the deposition of a kilometre-thick evaporite unit (Fig. 1a) (Ryan, 2009). The original definition of the MSC referred to a marked environmental change at the base of the Tripoli diatomite formation (Sicily, Italy) close to the Tortonian–Messinian boundary (Selli, 1960). Astronomical tuning of the pre-evaporitic succession showed that the MSC onset was synchronous throughout the Mediterranean (e.g. Krijgsman et al., 1999; Manzi et al., 2018; Meilijson et al., 2018). According to the shallow water–deep basin
model (Hsü et al., 1973; Roveri et al., 2014a), evaporite precipitation
was associated with a sea level drop in the range of 1500 m up to the
almost complete desiccation of the Mediterranean, culminating in halite
precipitation and marked by the incisions of deep canyons at the
Mediterranean margins. However, a non-evaporitic gypsum formation during MSC
has been also described (Hsü et al., 1978). Isotope analyses of gypsum
hydration water and the salinity of fluid inclusions in MSC gypsum indicate
large freshwater inputs during gypsum formation (Natalicchio et al., 2014;
Evans et al., 2015; Costanzo et al., 2019). Additionally, suggestions of the
important role of sulfur-oxidizing bacteria in biogeochemically meditated
gypsum formation (Grothe et al., 2020) are increasingly used to explain
low salinity yet high concentrations of Ca2+ and SO24-
(Clauer et al., 2000), during the formation of MSC evaporites.
(a) Geological sketch of the Messinian evaporite deposits
along the Mediterranean Sea (modified after Rouchy and Caruso, 2006). Note
that only the successfully dated sample locations are shown. (b) Chronostratigraphy of late Miocene to early Pliocene with MSC events in the Mediterranean (modified from Vasiliev et al., 2017).
According to previous publications (Roveri et al., 2008a, b, 2014a), the MSC can be separated into three main stages (Fig. 1b). Stage I
(5.97–5.60 Ma), the so-called Primary Lower Gypsum (PLG, Lugli et al., 2010), is defined by the deposition of primary selenite gypsum unit. During stage II (5.60–5.55 Ma), large evaporite deposits occurred (Resedimented Lower Gypsum unit, RLG), which includes halite, gypsum cumulates and brecciated limestones (Calcare di Base type 3, Manzi et al., 2011). Likewise, clastic gypsum derived from the dismantlement of the PLG unit can be found within this stage. Finally, alternating gypsum (mainly bottom grown selenite and cumulate) and fine- to coarse-grained terrigenous deposits form the Upper Gypsum unit (UG, stage III, 5.55–5.33 Ma). There is no outcrop with the complete section of the MSC, but different segments are well exposed throughout the Mediterranean.
Methodology
U–Pb data were acquired in situ in polished mounts and slabs using a
RESOLution 193 nm ArF excimer laser (CompexPro 102) equipped with a
two-volume ablation cell (Laurin Technic S155) coupled to a (i) single
collector (SC) ICPMS (ElementXR, Thermo Scientific) or (ii) multi-collector
(MC) ICPMS (Neptune Plus, Thermo Scientific) at FIERCE (Frankfurt Isotope
& Element Research Center), Goethe University Frankfurt. The method is
modified after Ring and Gerdes (2016) and Burisch et al. (2017). Samples are
pre-screened in order to identify sub-zones with a higher
238U/206Pb ratio before each analytical session.
The first sessions, between December 2019 and May 2020, were performed with
the SC-ICPMS. Prior to the measurements, signal strength was tuned for
maximum sensitivity while keeping oxide formation below ∼0.5 % (UO/U) and element fraction low (e.g. Th/U∼0.9). This
was done by ablating at 3 µms-1 with a 60 µm spot at 6 Hz and 3.5 J cm-2 fluence in the glass SRMNIST 612 (Jochum et al., 2011). The
average sensitivity obtained for the line is ca. 100 000 cps per µgg-1
for 238U. The detection limits (4× background signal) of the
instrument for 206Pb and 238U were ca. 0.3 and 0.03 ng g-1. Data were acquired in fully automated mode overnight. Each analysis consists of 18 s background acquisition followed by 18 s of sample ablation and 20 s washout. During 36 s data acquisition, the signals of 206Pb, 207Pb, 208Pb, 232Th and 238U were detected by peak jumping in simultaneous analogue and pulse-counting mode. Detailed data acquisition parameters are summarized in Table 1.
LA-SC-ICPMS U–Pb analysis procedure at Goethe University Frankfurt,
FIERCE laboratory.
Laboratory and sample preparation Laboratory nameFIERCE, Frankfurt Isotope & Element Research Center Goethe Universität, Frankfurt am MainSample type/mineralSulfateSample preparation25 mm polished resin mountsImagingPetrographic microscope and 2400 dpi digital scanLaser ablation system Make, model and typeRESOLution ArF excimer laser (COMpex Pro 102)Ablation cellTwo-volume ablation cell (Laurin Technic S155)Laser wavelength193 nmPulse width20 nsFluence2 J cm-2Repetition rate10 HzPre-ablation4 pulses (same parameters as main ablation)Ablation duration18 sAblation rate∼0.6µms-1 (in the primary RM), ∼0.9µms-1 (in carbonate and sulfate)Spot shape and sizeRound, 154 µm (diameter)Sampling modeStatic spot ablationGasesSample cell: He. Funnel: He + Ar. Tubbing: He + Ar + N2Gas flowsHe (300 mL min-1), Ar (1050 mL min-1), N2 (8 mL min-1).ICP-MS instrument Make, model and typeThermo Scientific ElementXR sector field ICP-MSSample introductionAblation aerosolRF power1300 WDetection systemSecondary electron multiplier (with conversion dynode at -8 kV). Simultaneous analogueand counting (pulse) modes of detection (conversion factors calculated per mass and appliedoffline). Magnetic field fixed. Detection by peak jumping with electrostatic analyser.Masses measured206, 207, 232, 238Dwell times206: 6.4 ms, 207: 7.5 ms, 232: 2.0 ms, 238: 4.6 msSamples per peak/integration type4 for all masses/averageTotal time per run99 msNumber of runs/total time370/36.6 sAcquisition modeTrigger from laser (20 s after pre-ablation), background: 18 s, ablation: 18 sDead time29 nsData processing Gas blank20 s on-peak zero subtracted.Calibration strategySRMNIST614 as primary RM, WC-1 as offset RM, and ASH15D as validation RM.Reference material (RM) informationSoda–lime glass SRMNIST614 (Jochum et al., 2011), WC-1 (Roberts et al., 2017),ASH15D (Nuriel et al., 2021)
Continued.
Data processing Data processing/LIEF correctionIn-house VBA spreadsheet programme (Gerdes and Zeh, 2006, 2009). Intercept method forLIEF correction, assumes Pbc-corrected WC-1 and samples behave identically.Mass discrimination207Pb/206Pb (0.2 %) and 206Pb/238U (5 %) normalized to primary standardCommon Pb correctionNo common Pb correction applied to the data.Uncertainty level and propagationUncertainties are quoted at 2σ absolute and are propagated by quadratic addition of the withinrun precision (SD of the mean of ratios in log-ratio space), counting statistics, background,common Pb correction (if applicable) and the excess of scatter (calculated from the primaryRM). In addition, an excess of variance of 1.45 % (1σ), calculated from the offset RM, wasadded quadratically to the 206Pb/238U ratios. Systematic uncertainties are reportedas an expanded uncertainty, considering long-term reproducibility (1.5 %, 2σ) anddecay constant uncertainties.Quality control/validationWC-1: 254.7±2.3/4.4 Ma (2 s, MSWD =1.00, n=28)ASH15D: 3.004±0.153/0.159 Ma (2 s, MSWD =0.85, n=28)(Ages are the 206Pb/238U lower intercept ages of the calculated isochrons with the concordiacurve in the Tera–Wasserburg space)
Due to the low precision obtained in those sessions, with only two samples
from a single session being considered acceptable (see results and
discussion), the use of the more sensitive MC-ICPMS (Craig et al., 2018,
2020) was deemed necessary for subsequent measurements. The sessions with
the MC-ICPMS were carried out between July 2020 and December 2020. As for
the single collector, signal strength was tuned for maximum sensitivity
while keeping oxide formation below ∼0.5 % (UO/U) and
element fraction low (e.g. Th/U∼0.9). In that case, it was
done with a 35 µm, 6 Hz, ca. 3.5 J cm-2 fluence and a 3 µms-1 line ablated in the glass SRMNIST 614 (Jochum et al., 2011). The average sensitivity obtained for the line is ca. 120 000 cps per µgg-1 for 238U (note the smaller spot size compare to the SC-ICPMS). The detection limits in the multi-collector ICPMS were ca. 0.3 and 0.01 ng g-1 for 206Pb and 238U, respectively. The analyses were done during 31 s (15 s background and 16 s of ablation) in static mode, measuring 206Pb and 207Pb with secondary electron multipliers (SEMs), 202Hg and 204Pb with multiple ion counters (MICs), and 232Th and 238U on Faraday cups with 1013Ω amplifiers. Faraday signals in V are
converted into counts per second (cps) by using a factor of 62 400 000. Detailed data
acquisition parameters are summarized in Table 2.
LA-MC-ICP-MS U–Pb analysis procedure at Goethe University
Frankfurt, FIERCE laboratory.
Laboratory and sample preparation Laboratory nameFIERCE, Frankfurt Isotope & Element Research Center Goethe Univesität, Frankfurt am MainSample type/mineralSulfateSample preparation25 mm polished resin mountsImagingPetrographic microscope and 2400 dpi digital scanLaser ablation system Make, model and typeRESOLution ArF excimer laser (COMpex Pro 102)Ablation cellTwo-volume ablation cell (Laurin Technic S155)Laser wavelength193 nmPulse width20 nsFluence2 J cm-2Repetition rate10 HzPre-ablation2 pulses (same parameters as main ablation)Ablation duration16 sAblation rate∼0.6µms-1 (in the primary RM), ∼0.9µms-1 (in carbonate and sulfate)Spot shape and sizeRound, 130 µm (75 µm for primary RM), except for session 1 (90 µm for all spots)Sampling modeStatic spot ablationGasesSample cell: He. Funnel: He + Ar. Tubbing: He + Ar + N2Gas flowsHe (300 mL min-1), Ar (∼950 mL min-1), N2 (5–10 mL min-1).Ar and N2 are tuned each session, so the values can be slightly differentICP-MS instrument Make, model and typeThermo Scientific Neptune Plus multi-collector ICP-MSSample introductionAblation aerosolRF power1300 WDetection systemSimultaneous multi-collection.Secondary electron multipliers (SEMs) for 206Pb and 207PbMultiple ion counters (MICs) for 202Hg and 204PbFaraday cups with 1013Ω amplifiers for 232Th and 238UMasses measured202, 204, 206, 207, 232, 238Total time per run131 msNumber of runs/total time230/30.1 sAcquisition modeTrigger from laser (14 s after pre-ablation), background: 15 s, ablation: 16 sDead time29 nsData processing Gas blank15 s on-peak zero subtracted.Calibration strategySRMNIST614 as primary RM, WC-1 as offset RM, and ASH15D, B6 andin-house calcite as validation RM.Reference material (RM) informationSoda–lime glass SRMNIST614 (Jochum et al., 2011), WC-1 (Roberts et al., 2017),ASH15D (Nuriel et al., 2021), B-6 (Pagel et al., 2018), CalBraun (in-house calcite RM)
Continued.
Data processing Data processing/LIEF correctionIn-house VBA spreadsheet programme (Gerdes and Zeh, 2006, 2009).Intercept method for LIEF correction, assumes Pbc-corrected WC-1 and samples behave identically.Mass discrimination207Pb/206Pb and 206Pb/238U normalized to primary standard (variable in each session)Common Pb correctionNo common Pb correction applied to the data.Uncertainty level and propagationUncertainties are quoted at 2σ absolute and are propagated by quadratic addition of the within-runprecision (SD of the mean of ratios in log-ratio space), counting statistics, background,common Pb correction (if applicable) and the excess of scatter (calculated from the primary RM).In addition, an excess of variance calculated for each session from the offset RM, was addedquadratically to the 206Pb/238U ratios. Systematic uncertainties are reported as an expandeduncertainty, considering long-term reproducibility (1.5 %, 2σ) and decay constant uncertainties.Quality control/validationSession 1:WC-1: 254.8±1.9/4.3 Ma (2 s, MSWD =1.0, n=12)B-6: 42.73±0.59/0.87 Ma (2 s, MSWD =0.84, n=12)CalBraun: 36.72±1.23/1.35 Ma (2 s, MSWD =0.89, n=12)Session 2:WC-1: 254.1±2.0/4.4 Ma (2 s, MSWD =1.0, n=20)B-6: 42.66±0.47/0.80 Ma (2 s, MSWD =0.50, n=22)CalBraun: 36.07±0.65/0.85 Ma (2 s, MSWD =0.61, n=22)Session 3:WC-1: 254.5±3.2/5.0 Ma (2 s, MSWD =1.0, n=10)ASH15D: 3.060±0.193/0.198 Ma (2 s, MSWD =1.0, n=10)B-6: 43.54±0.79/1.02 Ma (2 s, MSWD =1.13, n=10)Session 4:WC-1: 254.5±1.6/4.1 Ma (2 s, MSWD =1.0, n=20)ASH15D: 3.091±0.102/0.112 Ma (2 s, MSWD =0.88, n=20)B-6: 43.83±0.39/0.77 Ma (2 s, MSWD =0.56, n=20)(Ages are the 206Pb/238U lower intercept ages of the calculated isochrons with the concordiacurve in the Tera–Wasserburg space. WC-1 RM are anchored at 0.85 value of 207Pb/206Pb)
In each analytical session, soda–lime glass SRMNIST614 was used as the
primary reference material to correct for mass bias (207Pb/206Pb)
and the interelement fractionation and instrumental drift
(206Pb/238U) throughout the entire analytical session. Carbonate
reference material WC-1 (254 Ma, Roberts et al., 2017) was used to determine the difference of the Pb/U fractionation between carbonate and synthetic glass matrix. Depending on the analytical conditions (i.e. spot size, laser fluence, torch position, sample gas flows) the matrix effect can vary up to 12 % (FIERCE laboratory observation; e.g. Cruset et al., 2021), and even at similar tuning parameters, two sessions separated by some weeks could result in different Pb–U correction factors. So far, this behaviour is not very well understood, and due to its unpredictability, the matrix correction is calculated for each session (see below). Secondary reference calcite materials, ASH-15D calcite (2.965±0.011 Ma, Nuriel et al., 2021), B-6 (42.99±0.99 Ma, only LA-ICPMS data, Pagel et al., 2018)
and in-house calcite (reproducible age of ca. 36 Ma) were measured for
quality control. Not all the secondary reference materials were used in each session (see information in Tables 1 and 2).
Raw data were corrected offline using an in-house VBA spreadsheet programme
(Gerdes and Zeh, 2006, 2009). Following background and interferences
corrections, outliers (±2σ) were rejected based on the
time-resolved 207Pb/206Pb and 206Pb/238U ratios as well as the Pb and U signal. All in all, five sessions were performed, and the matrix
Pb/U correction factors (carbonate vs SRMNIST glass) applied to each of them are as follows: 4.5 % for SC-ICPMS session, 8 % for MC-ICPMS session 1 (same spot size for both carbonate and SRMNIST glass, see Table 2), 0.5 % for session 2 (different spot size, Table 2), 0 % for session 3 and 0 % for session 4. The 206Pb/238U downhole fractionation during 16 and 18 s depth profiling was estimated to be 3 % based on the common-Pb-corrected WC-1 analyses and was applied as an external correction to all sulfate analyses and secondary reference materials. Uncertainties for each isotopic ratio are the quadratic addition of the within-run precision,
counting statistic uncertainties of each isotope, and the excess of scatter
and variance (Horstwood et al., 2016) calculated from the SRMNIST 614 and
the WC-1 after drift correction. To account for the long-term
reproducibility of the method we added by quadratic addition an expanded
uncertainty of 1.5 % to the final age of all analysed samples (Montano et al., 2021). This was deducted from repeated analyses of ASH-15D in the
FIERCE laboratory between 2017 and 2019. Data were displayed in
Tera–Wasserburg plots and ages were calculated as lower concordia curve
intercepts using the same algorithms as Isoplot 4.15 (Ludwig, 2012). All
uncertainties are reported at the 2σ level. After the analysis, the
depth of the ablation pit was measured in several spots per sample,
including the WC-1 and SRMNIST 614 reference materials, using the Keyence
VHX 6000 digital microscope.
Samples and resultsU–Pb dating
U–Pb dating was applied to 32 samples from the different locations and all
available gypsum–anhydrite varieties (large selenite crystals, banded
selenite, gypsum cumulates, anhydrite, halite with gypsum and anhydrite
intercalation) across the Mediterranean Sea (Fig. 1), which display variable contents of Pb and U. Only five of them were successfully dated (15 % of
success). The undatable samples are characterized by analyses that clustered
near the common Pb intercept, disclosing a large amount of common Pb (Fig. 2). This low μ (238U/204Pb ratio) makes it impossible to
draw any regression line. No link between successful and unsuccessful samples
or their texture could be established, and both successful and
unsuccessful samples were found within the same type of gypsum. The
successfully dated samples are described below, and their results are
presented in Fig. 3 as well as in Tables S1 and S2 in the Supplement.
Diagram showing UmeancontenttoPbmeancontent vs.
maximum value on the 238U/206Pb axis. The successfully dated samples
have a distinctively higher U/Pb heterogeneity.
Tera–Wasserburg diagram (207Pb/206Pb vs. 238U/206Pb) for samples MTO 4-4, MTO 11-3, BOX 108, Pu 05 and BCR 9644. The blue ellipses and error envelope in samples MTO 4-4 and MTO
11-3 correspond to the analyses with the SC-ICPMS, while orange and
black refer to two independent sessions with the MC-ICPMS. Both
propagated within-session uncertainties and the expanded uncertainties are
±2σ.
Sample MTO 4-4
The MTO 4-4 sample was collected at the Monte Tondo gypsum quarry, located
within the Vena del Gesso basin (along the western Romagna Apennines), and
belongs to the PLG (Lugli et al., 2007, 2010; Vasiliev et al., 2017). It is
a banded selenite (type F4 of Lugli et al., 2010), and the cyclostratigraphic
age is 5.92 Ma, which is close to the onset of the MSC. The sample was measured in
three different sessions. The maximum U and Pb contents on the analysed spots
are 2.34 and 3.85 µgg-1, respectively, depicting a maximum
U/Pb ratio of 98.4 in the best case. The first of the sessions was measured with the SC-ICPMS and the analyses define a regression line with a lower intercept at 6.01±1.19 Ma (±2σ, MSWD =1.07, Fig. 3). The other two sessions were measured with the MC-ICPMS and the lower
intercepts of the regression lines are 5.55±0.61 Ma (±2σ, MSWD =1.00, Fig. 3) and 5.73±0.37 Ma (±2σ, MSWD =1.13, Fig. 3).
Sample MTO 11-3
This sample was also collected by Vasiliev et al. (2017) at the Monte Tondo
gypsum quarry. It is a massive selenite (F3 of Lugli et al., 2010) and
belongs to the younger cycles of the PLG. Its estimated cyclostratigraphic
age is 5.701 Ma. MTO 11-3 was also measured in three different sessions. The maximum U and Pb content on the analysed spots are 5.49 and
0.97 µgg-1, respectively, depicting a maximum U/Pb ratio value of 155.2 in the best case. The first of the sessions was measured with the SC-ICPMS and the analyses define a regression line with a lower intercept at 5.40±0.84 Ma (±2σ, MSWD =1.13, Fig. 3). The other
two sessions were measured with the MC-ICPMS and the lower intercepts of the
regression lines are 5.46±0.44 Ma (±2σ, MSWD =1.41, Fig. 3) and 5.55±0.32 Ma (±2σ, MSWD =1.03, Fig. 3).
Sample BOX 108
BOX 108 is a halite with anhydrite nodules. It comes from borehole EMS-4 (Cattolica Eraclea) in the Caltanissetta Basin (southwest of Sicily) and was
donated to Prof. Cita (University of Milano). The core was drilled from -82 m to -665 m below sea level, and the sample was located almost at the bottom (approximately at -610 m). Cyclostratigraphic ages point to 5.55–5.60 Ma. The analyses were made in both halite and anhydrite, but only the anhydrite was successful. It was measured twice with the MC-ICPMS. The maximum U and Pb contents on the analysed spots are 5.70 and 1.67 µgg-1, respectively, depicting a maximum U/Pb ratio value of 158.0 in the best case. The analyses define a regression line with a lower intercept at 5.55±0.35 Ma (±2σ, MSWD =1.01, Fig. 3) in the first of the sessions and 5.54±0.38 Ma (±2σ, MSWD =1.49, Fig. 3) in the second.
Sample BCR9644
Sample BCR9644 was collected from the cores of Deep Sea Drilling Program Site 42A hole 376 cored in 1975 west of Cyprus and stored at the Bremen International Ocean Drilling Program repository. BCR9644 was collected from
a gypsum breccia at 170.28 m below sea level and has a stratigraphic age of
ca. 5.55–5.60 Ma. It was measured twice with the MC-ICPMS. The maximum U
and Pb contents on the analysed spots are 2.31 and 0.61 µgg-1, respectively, although Pb rarely exceeds 0.1 µgg-1. The maximum
U/Pb ratio obtained in that sample is 577.5 in the best case. The low Pb contents imply large error ellipses, but successful regression lines have
been defined, with a lower intercept at 2.98±0.34 Ma (±2σ, MSWD =0.79, Fig. 3) in the first of the sessions and 2.98±0.32 Ma (±2σ, MSWD =1.40, Fig. 3) in the second.
Sample Pu 05
This sample was collected in the Ploutis region (Central Crete, Greece), and
it is a gypsum breccia. The stratigraphic age of these gypsum units is
disputed as being part of the PLG (Zachariasse et al., 2008), but the
texture of direct capping by Lago Mare deposits strongly suggests that Pu 05
belongs to the UG unit. Its cyclostratigraphic age is ca. 5.40 Ma. Pu 05 was
also measured twice with the MC-ICPMS. The maximum U and Pb contents on the
analysed spots are 1.44 and 0.16 µgg-1, respectively,
depicting a maximum U/Pb ratio value of 158.0 in the best case. Each session defines a regression line with a lower intercept at 5.15±0.42 Ma (±2σ, MSWD =0.68, Fig. 4) and 5.54±0.61 Ma
(±2σ, MSWD =1.02, Fig. 4), respectively.
Pit depth profile of samples MTO 11-3 (a) and BCR 9644 (b). Whereas the pit shape is roughly homogeneous in MTO 11-3, sample BCR 9644 displays deeper areas in some of the pits. The profiles are measured using a Keyence digital microscope VHX-6000.
Pit depth measurements
After the analyses, pit depths were measured in all the samples as well as
in the carbonate reference materials. The measured pit depth averages were
used for calculating the U and Pb contents (Tables S1 and S2). The shape and depth of the craters in WC-1 primary carbonate are all similar, and their average depth is 15.0 µm (SD =1.34, n=16). Few spots corresponding to the secondary reference materials were also checked, and
they are comparable to those of WC-1. The pits of the SRMNIST 614 are ca.
33 % shallower than the ones in the calcite matrix at around 10 µm
deep. Regarding the sulfate samples, the pit depth of samples MTO 4-4 and
MTO 11-3 is rather homogeneous with mean values of 29.6 µm (SD =6.2, n=44) and 18.9 µm (SD =5.9, n=37, Fig. 4a),
respectively. Samples BCR 9644 and BOX 108 display zones with different
heights in some of the ablation holes (Fig. 4b). Although they are
exceptional, two ca. 90 µm and two ca. 60 µm pits were measured in BOX 108. Considering them, the average depth is 28.2 µm (SD =16.4, n=64), whereas excluding those four heights the standard deviation improves substantially (25.0 µm, SD =8.8, n=60). The average depth for sample BCR 9644 is 16.2 µm (SD =6.7, n=32) excluding two ca. 60 µm spots. On the other hand, sample PU 05 shows higher variability and larger standard deviation, since the pit depth varies from 29 to 107 µm. The calculated average is 62.6 µm (SD =23.0, n=48).
DiscussionLow success rateHigh common Pb content and potential applicability
The majority of the analysed samples, 27 out of 32, were unsuccessful due to
the high common Pb content and hence low or non-existent spread in the
238U/206Pb axis. Recent studies in the field of environmental
hazards have shown that Pb tends to incorporate both gypsum
and anhydrite into sulfates (Astilleros et al., 2010; Morales et al., 2014; Kameda et al., 2017). In fact, in the presence of high-Pb fluids, anglesite (PbSO4) is
simultaneously intergrown with those sulfates. The behaviour of U remains
unknown, although experiments carried out on phosphogypsum, a waste
by-product generated from apatite in the production process of phosphoric
acid and phosphate fertilizers, suggest that U uptake by gypsum is pH-controlled (Lin et al., 2018). Thus, the more alkaline the environment is,
the higher the U concentration that could be expected in gypsum. However, the pH of
evaporating seawater rarely reaches those values and tends to drop as the
evaporation process goes on (Babel and Schreiber, 2014). Considering low
salinity but high concentrations of Ca2+ and SO24- (Clauer
et al., 2000) during the formation of MSC evaporites, the alkalinity of the
depositional environment might have increased. In any case, even the gypsum
precipitated in U-rich environments like uranium mine tailings contains a
high amount of Pb among other metals (Liu and Hendry, 2011).
The amount of common Pb is a challenge for dating young rocks, as their success strongly depends on the spread in the x axis (238U/206Pb). In turn, given the same initial 238U/206Pb ratio, older samples would have produced sufficient radiogenic Pb and thus a certain spread in the y axis (207Pb/206Pb) as to be projected in a more precise
regression line. Indeed, older samples are more influenced by the
207Pb/206Pb ratio, and therefore it is highly likely that the
success rate increases with the age of the sample.
SC-ICPMS vs. MC-ICPMS
The first set of samples was measured with the SC-ICPMS. The U and Pb
contents in the samples were rather low and produce large error ellipses in
every single spot. This issue, together with low μ ratios (i.e.
spread on 238U/206Pb), produces substantial uncertainties in the
final ages (Fig. 3) and a comparison with the depositional ages is poor. In
order to achieve better results, we decided to accomplish subsequent
measurements with the MC-ICPMS, which provides about 3 times better
sensitivity and simultaneous isotope detection (Craig et al., 2018, 2020).
The higher sensitivity implies smaller uncertainties in each spot, and hence more accurate and precise regression lines (i.e. ages) can be depicted.
Indeed, the improvement in age precision is clearly illustrated in Fig. 3.
Although the results can be biased because fewer data were acquired during
SC-ICPMS analyses, given a similar spread in the 238U/206Pb axis, the uncertainties of ca. 15 % (MTO 11-3) and 20 % (MTO 4-4) obtained with the SC-ICPMS were reduced to 8 % (MTO 11-3, seq 2) and 11 % (MTO 4-4, seq 2) by using the MC-ICPMS (Fig. 3). Furthermore, the re-measurement of these two samples in another independent session in which higher 238U/206Pb ratios were found reduced the uncertainties even more down to ca. 6 %.
U–Pb ages vs. cyclostratigraphic ages
Well-characterized matrix-matched reference material is essential for U–Pb
analytical techniques using laser probes as matrix differences between the
sample and reference standard can cause a significant offset in the obtained ages (Yang et al., 2018; Guillong et al., 2020). However, in the absence of
sulfate reference materials, an attempt to use calcite reference materials
was carried out, expecting that the offset between the two materials was going
to be low or negligible. The light absorption observed in calcite and gypsum is similar, and they are easily ablated even at low fluence (less than 2 J cm-2). As a comparison, Piccione et al. (2019) obtained analogous ages for contemporary fluorite and nacrite, both corrected to the same calcite
reference material, even when the fluorite has different light absorption
and higher energy is needed for its ablation (5–6 cm-2). For those
reasons, we expected a significantly lower matrix-induced offset than the
one observed between calcite and zircon (4.7 %, Parrish et al., 2018).
The cyclostratigraphic ages of the MSC samples are well known (e.g. Vasiliev et al., 2017) and we have used them for testing the suitability of the
corrections with respect to carbonate matrix. As pointed out above, the
majority of the samples contain a significant amount of common Pb, and only
five ages were obtained. Although the μ values of those samples were
only moderate, the individual uncertainties range between 6 % and 11 %, and the ages obtained for samples MTO 4-4, MTO 11-3, Pu 05 and BOX 108 are in accordance with the cyclostratigraphic ages (e.g. Lugli et al., 2007; Vasiliev et al., 2017). A direct comparison of the U–Pb and
cyclostratigraphic ages (Fig. 5), however, points to a slight bias toward
younger ages, suggesting a systematic offset between the two. Taken singly,
each U–Pb date overlaps the cyclostratigraphic age, but a more precise
measure is the inverse-variance-weighted mean of all 10 discrepancies
between the two ages. The calculated weighted average, i.e. the mean
discrepancy, is -0.14±0.14 Ma (±2σ, MSWD =0.77).
This can now have both an analytical and a geological significance; it can
be interpreted as (i) matrix mismatch between carbonate and sulfate or (ii) dating of a subsequent event instead of sedimentation. In fact, the
mobilization of U and Pb during sediment compaction causes some U/Pb
heterogeneity, which improves or enables the possibility of dating these
sediments by the U–Pb method. The small mean age discrepancy obtained on the sulfate samples is in line with that reported from Montano et al. (2022) on
lacustrine carbonates. In this study, although overlapping within
uncertainties, a systematic offset was found between U–Pb ages of carbonate
cement and that of zircon from ash layers. Thus, U–Pb ages of carbonate and
sulfate cement likely date early diagenesis and not the sediment
deposition. This supports our hypothesis that there is no difference in U–Pb
fractionation between sulfate and carbonate matrix, although it is not
direct evidence.
Comparison of the obtained U–Pb ages and the expected cyclostratigraphic ages. The weighted mean of the offsets between the two ages is -0.14±0.14 Ma (±2σ). The dashed line represents the U–Pb age with the cyclostratigraphic age correlation.
On the other hand, sample BCR 9644 resulted in an unexpected younger age
of ca. 3 Ma. The brecciated nature of the sample, together with its
extremely low Pb content (0.03 µgg-1 on average) in comparison with surrounding samples, suggests a subsequent (re)crystallization and
remobilization of U and Pb that could be related to the breccia formation.
Warthmann et al. (2000) proposed important bacterial activity after the
evaporite formation. For the equivalent-in-time Site 374, located southeast of
Sicily, an approximately 3 m thick dolomitization front in Pliocene hemipelagic succession overlying the UG was identified. Here, a hypothesized role of the deep biosphere, sulfate-reducing bacteria thriving on the dissolution of sulfate-bearing minerals (Warthmann et al., 2000; Petrash et
al., 2017) was suggested. Montano et al. (2019, 2021) showed that biological
activity may control the U–Pb partitioning on carbonates, so the connection between the bacterial activity and the 3 Ma age could not be discarded.
Although gypsum to anhydrite to gypsum (two-step) transformation can be
considered another possible scenario, there is no observation in
the literature that supports this hypothesis.
Pit depth profiles
Guillong et al. (2020) showed that different ablation parameters produce
distinctive pit profiles (the so-called “aspect ratio” or depth to diameter
ratio), and it could result in a noticeable bias in the data. The carbonate
reference materials analysed here with a 130 µm spot size resulted
in a depth of ca. 15 µm (aspect ratio of 0.12), whereas the sulfates vary between 16 and 63 µm (aspect ratio between 0.12 and
0.48, Fig. 4). The ablation on NIST glass resulted in shallower ca. 10 µm deep holes and an aspect ratio of 0.13, similar to the carbonates. This divergence between the sulfates could be attributed to various
non-excluding features such as different textures, particle size, porosity
or compaction (Elisha et al., 2021). However, in the cases with an aspect
ratio mismatch relative to the primary standard of less than 2, a deviation
lower than 5 % is anticipated (Guillong et al., 2020), which lies in the
final result uncertainty of the majority of the samples analysed here. The
larger discrepancy observed in sample Pu 05 (relative mismatch of 4)
could result in age offsets up to 10 % (Guillong et al., 2020, their
Fig. 4). However, Fig. 4b reveals an important heterogeneity in the pit
profile in some samples, with a silhouette that resembles pores. Whether
they correspond to porosity or chunks released due to a badly coupled laser
beam, the signal remained stable.
These pit depth issues are also related to the downhole fractionation
corrections. Mangenot et al. (2018) claimed that shallow pit depth compared
to the spot size could minimize the downhole fractionation. That argument
could apply to our reference materials and sulfates with shallower pit
depth, but how it affects depths beyond 50–60 µm can be arguable.
Lenoir et al. (2021) obtained coherent regression lines in fluorites even
with pit depths (up to 50 % variable) larger than spot sizes.
Notwithstanding, the lack of bias between our U–Pb ages and
cyclostratigraphic ages suggests that the different downhole fractionation
is not noticeable or remains within the uncertainties.
Conclusions
In this contribution, we have evaluated the applicability of carbonates as “almost-matrix-matched reference materials” for U–Pb dating of sulfates,
and for that purpose, gypsum and anhydrite samples from the Messinian
Salinity Crisis were analysed. The known cyclostratigraphic ages of these
evaporites were compared with the in situ U–Pb ages obtained. The samples
showed a high amount of common Pb and low spread in the U/Pb axis, and therefore only 15 % of the samples were successful. In fact, due to the
large uncertainties obtained at the beginning, we were forced to switch from the SC-ICPMS to MC-ICPMS in order to improve the precision of the
measurements. Four of the five successfully dated samples were
indistinguishable within error from the expected ages, while the other was
considerably younger. We assume that all the factors that could produce a
bias in the final age, if any, are contained in the uncertainty, and
therefore the use of carbonate reference materials could be a trustworthy
approach for in situ U–Pb dating of sulfates. We acknowledge that the
availability of sulfate reference material in the future will result in an
improvement in both reliability and precision.
Code and data availability
The data have been processed with an in-house VBA spreadsheet programme (Gerdes and Zeh, 2006, 10.1016/j.epsl.2006.06.039 and 2009, 10.1016/j.chemgeo.2008.03.005), which is available upon request.
All the raw data produced during this study are available in the Supplement.
The supplement related to this article is available online at: https://doi.org/10.5194/gchron-4-601-2022-supplement.
Author contributions
AB and AG were involved in the LA-ICPMS analysis and pit depth measurements. IV accomplished the fieldwork and sample collection. All the authors collaborated in preparing the paper.
Competing interests
The contact author has declared that none of the authors has any competing interests.
Disclaimer
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Acknowledgements
This study has benefited greatly from insightful reviews by Andrew R.
Kylander-Clark, Catherine Mottram and the associated editor Noah McLean, as
well as the handling editor Klaus Mezger. This is FIERCE contribution no. 110. FIERCE is financially supported by the Wilhelm and Else Heraeus
Foundation and by the Deutsche Forschungsgemeinschaft, which is gratefully
acknowledged. Cores from borehole EMS-4 (Cattolica Eraclea) in the
Caltanissetta Basin (Sicily) are stored in the core repository of the
University of Milano, Department of Earth Science “Ardito Desio” after
core restoration performed within COST Action CA15103 MEDSALT.
Financial support
This research has been supported by the postdoctoral fellowship programme, granted to the first author, of the Basque Government (grant no. POS_2018_1_0018).
Review statement
This paper was edited by Noah M. McLean and reviewed by Andrew R. Kylander-Clark and Catherine Mottram.
ReferencesAndreetto, F., Matsubara, K., Beets, C. J., Fortuin, A. R., Flecker, R., and
Krijgsman, W.: High Mediterranean water-level during the Lago-Mare
phase of the Messinian Salinity Crisis: insights from the Sr isotope records
of Spanish marginal basins (SE Spain), Paleogeogr. Paleocl., 562, 110139, 10.1016/j.palaeo.2020.110139, 2021.Astilleros, J. M., Godelitsas, A., Rodríguez-Blanco, J. D.,
Fernández-Díaz, L., Prieto, M., Lagoyannis, A., and Harissopulos, S.: Interaction of gypsum with Pb – bearing aqueous solutions, Appl. Geochem., 25, 1008–1016, 10.1016/j.apgeochem.2010.04.007, 2010.Babel, M. and Schreiber, B. C.: Geochemistry of evaporites and evolution of
seawater, in: Treatise on Geochemistry, 2nd edn., edited by: Turekian,
K. and Holland, H., Elsevier, Oxford, UK, 483–560, 10.1016/B978-0-08-095975-7.00718-X, 2014.Brannon, J. C., Cole, S. C., Podosek, F. A., Ragan, V. M., Coveney, R. M.,
Wallace, M. W., and Bradley, A. J.: Th-Pb and U–Pb dating of ore-stage
calcite and Paleozoic fluid flow, Science, 271, 491–493,
10.1126/science.271.5248.491, 1996.Burisch, M., Walter, B. F., and Markl, G.: Silicification of Hydrothermal
Gangue Minerals in Pb-Zn-Cu-Fluorite-Quartz-595 Baryte Veins, Can. Mineral., 55, 501–514, 10.3749/canmin.1700005, 2017.Burisch, M., Gerdes, A., Meinert, L., Albert, R., Seifert, T., and Gutzmer,
J.: The essence of time – fertile skarn formation in the Variscan Orogenic
Belt, Earth Planet. Sc. Lett., 519, 165–170, 10.1016/j.epsl.2019.05.015, 2019.
CIESM: The Messinian salinity crisis from mega-deposits to microbiology, in:
A consensus report. 33ème CIESM Workshop Monographs 33, edited by:
Briand, F., CIESM Publisher, Monaco, 91–96, 2008.Clauer, N., Chaudhuri, S., Toulkeridis, T., and Blanc, G.: Fluctuations of
Caspian Sea level: beyond climatic variations?, Geology, 28, 1015–1018,
10.1130/0091-7613(2000)28<1015:FOCSLB>2.0.CO;2, 2000.Conley, R. F. and Bundy, W. M.: Mechanism of gypsification, Geochim.
Cosmochim. Ac., 15, 57–72, 10.1016/0016-7037(58)90010-3, 1958.Costanzo, A., Cipriani, M., Feely, M., Cianfione, G., and Dominici, R.:
Messinian twinned selenite from the Catanzaro Trough, Calabria, Southern
Italy: field, petrographic and fluid inclusion perspectives, Carbonate.
Evaporite., 34, 743–756, 10.1007/s13146-019-00516-0, 2019.Craig, G., Managh A. J., Stremtan, C., Lloyd, N. S., and Horstwood, M. S. A.:
Doubling Sensitivity in Multicollector ICPMS Using High-Efficiency, Rapid
Response Laser Ablation Technology, Anal. Chem., 90, 11564–11571,
10.1021/acs.analchem.8b02896, 2018.
Craig, G., Bracciali, L., and Lloyd, N.: LA-ICP-MS for U-(Th)-Pb
geochronology: Which analytical capability is right for my laboratory?,
Thermo Fisher Scientific, Smart. Note 30581, 2020.Cruset, D., Verges, J., Rodrigues, N., Belenguer, J., Pascual-Cebrian, E.,
Almar, Y., Perez-Caceres, I., Macchiavelli, C., Trave, A., Beranoaguirre,
A., Albert, R., Gerdes, A., and Messager, G.: U–Pb dating of carbonate
veins constraining timing of beef growth and oil generation within Vaca
Muerta Formation and compression history in the Neuquen Basin along the
Andean fold and thrust belt, Mar. Petrol. Geol., 132, 10520,
10.1016/j.marpetgeo.2021.105204, 2021.Deng, X. D., Li, J. W., Luo, T., and Wang, H. Q.: Dating magmatic and
hydrothermal processes using andradite-rich garnet U–Pb geochronometry,
Contrib. Mineral. Petr., 172, 71, 10.1007/s00410-017-1389-2, 2017.Elisha, B., Nuriel, P., Kylander-Clark, A., and Weinberger, R.: Towards in situ U–Pb dating of dolomite, Geochronology, 3, 337–349, 10.5194/gchron-3-337-2021, 2021.Evans, N. P., Turchyn, A. V., Gázquez, F., Bontognali, R. R., Chapman,
H. J., and Hodell, D. A.: Coupled measurements of δ18O and
δD of hydration water and salinity of fluid inclusions in gypsum
from the Messinian Yesares Member, Sorbas Basin (SE Spain), Earth Planet.
Sc. Lett., 430, 499–510, 10.1016/j.epsl.2015.07.071, 2015.Flecker, R. and Ellam, R. M.: Identifying Late Miocene episodes of
connection and isolation in the Mediterranean–Paratethyan realm using Sr
isotopes, Sediment. Geol., 188–189, 189–203, 10.1016/j.sedgeo.2006.03.005, 2006.Flecker, R., Krijgsman, W., Capella, W., de Castro Martíns, C.,
Dmitrieva, E., Mayser, J. P., Marzocchi, A., Modestu, S., Lozano, D. O.,
Simon, D., Tulbure, M., van den Berg, B., van der Schee, M., de Lange, G.,
Ellam, R., Govers, R., Gutjahr, M., Hilgen, F., Kouwenhoven, T., Lofi, J.,
Meijer, P., Sierro, F. J., Bachiri, N., Barhoun, N., Alami, A. C., Chacon, B., Flores, Jose A., Gregory, J., Howard, J., Lunt, D., Ochoa, M., Pancost, R., Vincent, S., and Yousfi, M. Z.: Evolution of the Late Miocene Mediterranean Atlantic gateways and their impact on regional and global environmental change, Earth-Sci. Rev., 150, 365–392, 10.1016/j.earscirev.2015.08.007, 2015.Gerdes, A. and Zeh, A.: Combined U–Pb and Hf isotope LA-(MC-)ICP-MS
analyses of detrital zircons: comparison with SHRIMP and new constraints for
the provenance and age of an Armorican metasediment in Central Germany,
Earth Planet. Sc. Lett., 249, 47–61, 10.1016/j.epsl.2006.06.039, 2006.Gerdes, A. and Zeh, A.: Zircon formation versus zircon alteration – new
insights from combined U–Pb and Lu-Hf in-situ LA-ICP-MS analyses, and
consequences for the interpretation of Archean zircon from the Central Zone
of the Limpopo Belt, Chem. Geol., 261, 230–243, 10.1016/j.chemgeo.2008.03.005, 2009.Grandia, F., Asmerom, Y., Getty, S., Cardellach, E., and Canals, A.: U–Pb
dating of MVT ore-stage calcite: implications for fluid flow in a Mesozoic
extensional basin from Iberian Peninsula, J. Geochem. Explor., 69, 377–380, 10.1016/S0375-6742(00)00030-3, 2000.Grothe, A., Andreetto, F., Reichart, G. J., Wolthers, M., Van Baak, C. G.,
Vasiliev, I., Stoica, M., Sangiorgi, F., Middelburg, J. J., Davies, G. R., and Krijgsman, W.: Paratethys pacing of the Messinian Salinity Crisis: low
salinity waters contributing to gypsum precipitation?, Earth Planet. Sc.
Lett., 532, 116029, 10.1016/j.epsl.2019.116029,
2020.Guillong, M., Wotzlaw, J.-F., Looser, N., and Laurent, O.: Evaluating the reliability of U–Pb laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) carbonate geochronology: matrix issues and a potential calcite validation reference material, Geochronology, 2, 155–167, 10.5194/gchron-2-155-2020, 2020.Horstwood, M. S. A., Košler, J., Gehrels, G., Jackson, S. E., McLean, N.
M., Paton, C., Pearson, N. J., Sircombe, K., Sylvester, P., Vermeesch, P.,
and Bowring, J. F.: Community-derived standards for LA-ICP-MS U-(Th-)Pb
geochronology-Uncertainty propagation, age interpretation and data
reporting, Geostand. Geoanal. Res., 40, 311–332, 10.1111/j.1751-908X.2016.00379.x, 2016.Hsü, K. J., Ryan, W. B. F., and Cita, M. B.: Late Miocene desiccation of the
Mediterranean, Nature, 242, 240–244, 10.1038/242240a0, 1973.Hsü, K. J., Montadert, L., Ross, D. A., and Neprochnov, Y. P.: Annotated
record of the detailed examination of Mn deposits from DSDP Leg 42 (Holes
372 and 379A), Pangaea [data set], 10.1594/PANGAEA.871889, 1978.Jochum, K. P., Weis, U., Stoll, B., Kuzmin, D., Yang, Q., Raczek, I., Jacob,
D. E., Stracke, A., Birbaum, K., Frick, D. A., Günther, D., and Enzweiler, J.: Determination of reference values for NIST SRM 610–617 glasses following ISO guidelines, Geostand. Geoanal. Res., 35, 97–429, 10.1111/j.1751-908X.2011.00120.x, 2011.Kameda, K., Hashimoto, Y., Wang., S.-L., Hirai, Y., and Miyahara, H.:
Simultaneous and continuous stabilization of As and Pb in contaminated
solution and soil by a ferrihydrite-gypsum sorbent, J. Hazard. Mater., 327,
171–179, 10.1016/j.jhazmat.2016.12.039, 2017.Krijgsman, W., Hilgen, F. J., Raffi, I., Sierro, F. J., and Wilson, D. S.:
Chronology, causes and progression of the Messinian Salinity Crisis, Nature,
400, 652–655, 10.1038/23231, 1999.Krijgsman, W., Stoica, M., Vasiliev, I., and Popov, V. V.: Rise and fall of
the Paratethys Sea during the Messinian Salinity Crisis, Earth Planet. Sc.
Lett., 290, 183–191, 10.1016/j.epsl.2009.12.020, 2010.Krijgsman, W., Capella, W., Simon, D., Hilgen, F. J., Kouwenhoven, T. J.,
Meijer, P. T., Sierro, F. J., Tulbure, M. A., van den Berg, B. C. J., van der
Schee, M., and Flecker, R.: The Gibraltar Corridor: watergate of the
Messinian Salinity Crisis, Mar. Geol., 403, 238–246, 10.1016/j.margeo.2018.06.008, 2018.Laskar, J.: The limits of Earth orbital calculations for geological
time-scale use, in: Astronomical (Milankovitch) Calibration of the
Geological Time-Scale, edited by: Shackleton, N. J., McCave, I. N., and
Graham, P. W., Philos. T. Roy. Soc. A., 357, 1735–1759, 10.1098/rsta.1999.0399, 1999.Lenoir, L., Blaise, T., Somogyi, A., Brigaud, B., Barbarand, J., Boukari, C., Nouet, J., Brézard-Oudot, A., and Pagel, M.: Uranium incorporation in fluorite and exploration of U–Pb dating, Geochronology, 3, 199–227, 10.5194/gchron-3-199-2021, 2021.Lin, J., Sun, W., Desmarais, J., Chen, N., Feng, R., Zhang, P., Li, D.,
Lieu, A., Tse, J. S., and Pan, Y.: Uptake and speciation of uranium in
synthetic gypsum (CaSO4⋅ 2H2O): applications to
radioactive mine tailings, J. Environ. Radioactiv., 181, 8–17, 10.1016/j.jenvrad.2017.10.010, 2018.Liu, D. J. and Hendry, M. J.: Controls on 226Ra during raffinate
neutralization at the Key Lake uranium mill, Saskatchewan, Canada, Appl.
Geochem., 26, 2113–2120, 10.1016/j.apgeochem.2011.07.009, 2011.
Ludwig, K. R.: User's Manual for Isoplot Version 3.75-4.15: a
Geochronological Toolkit for Microsoft Excel, Berkeley Geochronological
Center Special Publication, no. 5, 2012.Lugli, S., Bassetti, M. A., Manzi, V., Barbieri, M., Longinelli, A., and
Roveri, M.: The Messinian “Vena del Gesso” evaporites revisited:
characterization of isotopic composition and organic matter, J. Geol. Soc.
Lond., 285, 179–190, 10.1144/SP285.11, 2007.Lugli, S., Manzi, V., Roveri, M., and Schreiber, B. C.: The primary Lower
Gypsum in the Mediterranean: a new facies interpretation for the first stage
of the Messinian salinity crisis, Palaeogeogr. Palaeocl., 297, 83–99, 10.1016/j.palaeo.2010.07.017, 2010.Mangenot, X., Gasparrini, M., Rouchon, V., and Bonifacie, M.: Basin-scale
thermal and fluid flow histories revealed by carbonate clumped isotopes
(Δ47) – Middle Jurassic carbonates of the Paris Basin depocentre,
Sedimentology, 65, 123–150, 10.1111/sed.12427, 2018.Manzi, V., Gennari, R., Lugli, S., Roveri, M., and Schreiber, B. C.: The
Messinian “Calcare di Base” (Sicily, Italy) revisited, Geol. Soc. Am. Bull., 123, 347–370, 10.1130/B30262.1, 2011.Manzi, V., Gennari, R., Hilgen, F., Krijgsman, W., Lugli, S., Roveri, M.,
and Sierro, F. J.: Age refinement of the Messinian salinity crisis onset in
the Mediterranean, Terra Nova, 25, 315–322, 10.1111/ter.12038, 2013.Manzi, V., Gennari, R., Lugli, S., Persico, D., Reghizzi, M., Roveri, M.,
Schreiber, B. C., Calvo, R., Gavrieli, I., and Gvirtzman, Z.: The onset of
the Messinian salinity crisis in the deep Eastern Mediterranean basin, Terra
Nova, 30, 189–198, 10.1111/ter.12325, 2018.Meilijson, A., Hilgen, F., Sepúlveda, J., Steinberg, J., Fairbank, V.,
Flecker, R., Waldmann, N. D., Spaulding, S. A., Bialik, O. M., and Boudinot,
F. G.: Chronology with a pinch of salt: integrated stratigraphy of Messinian
evaporites in the deep Eastern Mediterranean reveals long-lasting halite
deposition during Atlantic connectivity, Earth-Sci. Rev., 194, 374–398, 10.1016/j.earscirev.2019.05.011, 2019Millonig, L. J., Albert, R., Gerdes, A., Avigad, D., and Dietsch, C.:
Exploring laser ablation U–Pb dating of regional metamorphic garnet – The
Straits Schist, Connecticut, USA, Earth Planet. Sc. Lett., 552, 116589,
10.1016/j.epsl.2020.116589, 2020.
Montano, D., Gasparrini, M., Gerdes, A., Albert, R., Rohais, S., and Della
Porta, G.: In-situ carbonate U–Pb analysis by LA-ICP-MS: From absolute
dating to understanding the U–Pb partitioning in lacustrine systems,
Goldschmidt 2019 Abstracts, Abstract no, 2323, 2019.Montano, D., Gasparrini, M., Gerdes, A., Della Porta, G., and Albert, R.:
In-situ U–Pb dating of Ries Crater lacustrine carbonates (Miocene,
South-West Germany): implications for continental carbonate
chronostratigraphy, Earth Planet. Sc. Lett., 568, 117011, 10.1016/j.epsl.2021.117011, 2021.Montano, D., Gasparrini, M., Rohais, S., Albert, R., and Gerdes, A.:
Depositional age models in lacustrine systems from zircon and carbonate U–Pb
geochronology, Sedimentology, in press,
10.1111/sed.13000, 2022.Morales, J., Astilleros, J. M., Jiménez, A., Göttlicher, J.,
Steininger, R., and Fernández-Díaz, L.: Uptake of dissolved lead by
anhydrite surfaces, Appl. Geochem., 40, 89–96,
10.1016/j.apgeochem.2013.11.002, 2014.Murray, R. C.: Origin and diagenesis of gypsum and anhydrite, SEPM Journal of Sedimentary Research, 34, 512–523,
10.1306/74D710D2-2B21-11D7-8648000102C1865D, 1964.Natalicchio, M., Dela Pierre, F., Lugli, S., Lowenstein, T. K., Feiner, S. J., Ferrando, S., Manzi, V., Roveri, M., and Clari, P.: Did Late Miocene
(Messinian) gypsum precipitate from evaporated marine brines? Insights from
the Piedmont Basin (Italy), Geology, 42, 179–182, 10.1130/G34986.1, 2014.Nuriel, P., Wotzlaw, J.-F., Ovtcharova, M., Vaks, A., Stremtan, C., Šala, M., Roberts, N. M. W., and Kylander-Clark, A. R. C.: The use of ASH-15 flowstone as a matrix-matched reference material for laser-ablation U–Pb geochronology of calcite, Geochronology, 3, 35–47, 10.5194/gchron-3-35-2021, 2021.Ossorio, M., Van Driessche, A. E. S., Pérez, P., and García-Ruiz,
J. M.: The gypsum-anhydrite paradox revisited, Chem. Geol., 386, 16–21, 10.1016/j.chemgeo.2014.07.026, 2014.Pagel, M., Bonifacie, M., Schneider, D. A., Gautheron, C., Brigaud, B.,
Calmels, D., Cros, A., Saint-Bezar, B., Landrein, P., Sutcliffe, C., and
Davis, D.: Improving paleohydrological and diagenetic reconstructions in
calcite veins and breccia of a sedimentary basin by combining Δ47
temperature, δ18O water and U-Pb age, Chem. Geol., 481, 1–17, 10.1016/j.chemgeo.2017.12.026, 2018.Parrish, R. R., Parrish, C. M., and Lasalle, S.: Vein calcite dating reveals
Pyrenean orogen as cause of Paleogene deformation in southern England, J.
Geol. Soc., 175, 425–442, 10.1144/jgs2017-107, 2018.Petrash, D. A., Bialik, O. M., Bontognali, T. R. R., Vasconcelos, C., Roberts, J. A., McKenzie, J. A., and Konhauser, K. O.: Microbially catalyzed dolomite formation: From near-surface to burial, Earth-Sci. Rev., 171, 558–582, 10.1016/j.earscirev.2017.06.015, 2017.Piccione, G., Rasbury, E. T., Elliott, B. A., Kyle, J. R., Jaret, S. J., Acerbo, A. S., Lanzirotti, A., Northrup, P., Wooton, K., and Parrish, R. R.: Vein fluorite U-Pb dating demonstrates post-6.2 Ma rare-earth element
mobilization associated with Rio Grande rifting, Geosphere, 15, 1958–1972, 10.1130/GES02139.1, 2019.Rasbury, E. T. and Cole, J. M.: Directly dating geologic events: U-Pb
dating of carbonates, Reviews of Geophysics, 47, RG3001, 10.1029/2007RG000246, 2009.Ring, U. and Gerdes, A.: Kinematics of the Alpenrhein-Bodensee graben system
in the Central Alps: Oligocene/Miocene transtension due to formation of the
Western Alps arc, Tectonics, 35, 1367–1391, 10.1002/2015TC004085, 2016.Roberts, N. M. W., Rasbury, E. T., Parrish, R. R., Smith, C. J., Horstwood,
M. S. A., and Condon, D. J.: A calcite reference material for LA-ICP-MS U–Pb
geochronology, Geochem. Geophy. Geosy., 18, 2807–2814, 10.1002/2016GC006784, 2017.Roberts, N. M. W., Drost, K., Horstwood, M. S. A., Condon, D. J., Chew, D., Drake, H., Milodowski, A. E., McLean, N. M., Smye, A. J., Walker, R. J., Haslam, R., Hodson, K., Imber, J., Beaudoin, N., and Lee, J. K.: Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb carbonate geochronology: strategies, progress, and limitations, Geochronology, 2, 33–61, 10.5194/gchron-2-33-2020, 2020.Rouchy, J. M. and Caruso, A.: The Messinian salinity crisis in the
Mediterranean basin: a reassessment of the data and an integrated scenario,
Sediment. Geol., 188–189, 35–67, 10.1016/j.sedgeo.2006.02.005, 2006.Roveri, M., Lugli, S., Manzi, V., and Schreiber, B. C.: The Messinian
Sicilian stratigraphy revisited: toward a new scenario for the Messinian
salinity crisis, Terra Nova, 20, 483–488, 10.1111/j.1365-3121.2008.00842.x, 2008a.
Roveri, M., Bertini, A., Cosentino, D., Di Stefano, A., Gennari, R.,
Gliozzi, E., Grossi, F., Iaccarino, S. M., Lugli, S., Manzi, V., and Taviani,
M.: A high-resolution stratigraphic framework for the latest Messinian
events in the Mediterranean area, Stratigraphy, 5, 323–342, 2008b.Roveri, M., Flecker, R., Krijgsman, W., Lofi, J., Lugli, S., Manzi, V.,
Sierro, F. J., Bertini, A., Camerlenghi, A., De Lange, G., Govers, R.,
Hilgen, F. J., Hübscher, C., Meijer, P. T., and Stoica, M.: The Messinian
Salinity Crisis: past and future of a great challenge for marine sciences,
Mar. Geol., 352, 25–58, 10.1016/j.margeo.2014.02.002, 2014a.Roveri, M., Lugli, S., Manzi, V., Gennari, R., and Schreiber, B. C.: High-resolution strontium isotope stratigraphy of the Messinian deep
Mediterranean basins: implications for marginal to central basins
correlation, Mar. Geol., 349, 113–125, 10.1016/j.margeo.2014.01.002, 2014b.Ryan, W. B.: Decoding the Mediterranean salinity crisis, Sedimentology, 56, 95–136, 10.1111/j.1365-3091.2008.01031.x, 2009.Schaltegger, U., Schmitt, A. K., and Horstwood, M. S. A.: U–Th–Pb zircon
geochronology by ID-TIMS, SIMS, and laser ablation ICP-MS: Recipes,
interpretations, and opportunities, Chem. Geol., 402, 89–110, 10.1016/j.chemgeo.2015.02.028, 2015.
Selli, R.: Il Messiniano Mayer-Eymar 1867. Proposta di un neostratotipo,
Giornale di Geologia, 28, 1–33, 1960.Seman, S., Stockli, D. F., and McLean, N. M.: U-Pb geochronology of
grossular-andradite garnet, Chem. Geol., 460, 106–116,
10.1016/j.chemgeo.2017.04.020, 2017.Sindern, S., Havenith, V., Gerdes, A., Meyer, F. M., Adelmann, D., and
Hellmann, A.: Dating of anatase-forming diagenetic reactions in Rotliegend
sandstones of the North German Basin, Int. J. Earth Sci., 108, 1275–1292, 10.1007/s00531-019-01705-x, 2019.
Sylvester, P. (Ed.): Matrix effects in Laser ablation-ICP-MS, in: Laser
Ablation-ICP-MS in the Earth Sciences: Current Practices and Outstanding
Issues, Mineralogical association of Canada, 67–78, 2008.Van Driessche, A. E. S., Stawski, T., and Kellermeier, M.: Calcium sulfate
precipitation pathways in natural and engineering environments, Chem. Geol.,
530, 119274, 10.1016/j.chemgeo.2019.119274, 2019.Vasiliev, I., Mezger, E. M., Lugli, S., Reichart, G. J., Manzi, V., and
Roveri, M.: How dry was the Mediterranean during the Messinian salinity
crisis?, Paleogeogr. Paleocl., 471, 120–133,
10.1016/j.palaeo.2017.01.032, 2017.Wafforn, S., Seman, S., Kyle, J. R., Stockli, D., Leys, C., Sonbait, D., and
Cloos, M.: Andradite garnet U–Pb geochronology of the big Gossan skarn,
Ertsberg-Grasberg mining district, Indonesia, Econ. Geol., 113, 769–778, 10.5382/econgeo.2018.4569, 2018.Warren, J. K.: Evaporites: A Geological Compendium, Springer, Berlin, 10.1007/978-3-319-13512-0, 2016.Warthmann, R., van Lith, Y., Vasconcelos, C., McKenzie, J. A., and Karpoff,
A. M.: Bacterially induced dolomite precipitation in anoxic culture
experiments, Geology, 28, 1091–1094, 10.1130/0091-7613(2000)28<1091:BIDPIA>2.0.CO;2, 2000.Woodhead, J., Hellstrom, J., Maas, R., Drysdale, R., Zanchetta, G., Devine,
P., and Taylor, E.: U–Pb geochronology of speleothems by MC-ICPMS, Quat.
Geochronol., 1, 208–221, 10.1016/j.quageo.2006.08.002, 2006.Woodhead, J., Hellstrom, J., Pickering, R., Drysdale, R., Paul, B., and
Bajo, P.: U and Pb variability in older speleothems and strategies for their
chronology, Quat. Geochronol., 14, 105–113, 10.1016/j.quageo.2012.02.028, 2012.Yan, S., Zhou, R. J., Niu, H. C., Feng, Y. X., Nguyen, A. D., Zhao, Z. H., Yang, W. B., Qian, D., and Zhao, J. X.: LA-MC-ICP-MS U–Pb dating of low-U garnets reveals multiple episodes of skarn formation in the volcanic-hosted iron mineralization system, Awulale belt, Central Asia, Geol. Soc. Am. Bull., 132, 1031–1045, 10.1130/B35214.1, 2020.Yang, Y. H., Wu, F. Y., Yang, J. H., Mitchell, R. H., Zhao, Z. F., Xie, L. W., Huang, C., Ma, Q., Yang, M., and Zhao, H.: U–Pb age determination of
schorlomite garnet by laser ablation inductively coupled plasma mass
spectrometry, J. Anal. Atom. Spectrom., 33, 231–239, 10.1039/c7ja00315c, 2018.Zachariasse, W. J., van Hinsbergen, D. J. J., and Fortuin, A. R.: Mass wasting and uplift on Crete and Karpathos during the early Pliocene related to initiation of south Aegean left-lateral, strike-slip tectonics, Geol. Soc.
Am. Bull., 120, 976–993, 10.1130/B26175.1, 2008.