Chronology with a pinch of salt:Integrated stratigraphy of Messinian evaporites in the deep Eastern Mediterranean reveals long-lasting halite deposition during Atlantic connectivity

The Messinian Salinity Crisis (MSC; 5.97–5.33 Ma) is considered an extreme environmental event driven by changes in climate and tectonics, which affected global ocean salinity and shaped the biogeochemical composition of the Mediterranean Sea. Yet, after more than 50 years of research, MSC stratigraphy remains controversial. Recent studies agree that the transition from the underlying pre-evaporite sediments to thick halite deposits is conformal in the deep Eastern Mediterranean Basin. However, the age of the base and the duration of halite deposition are still unclear. Also disputed is the nature of the intermediate and upper MSC units, which are characterized as periods of increased clastic deposition into the Eastern Mediterranean based on marginal outcrops and seismic data. We provide a multidisciplinary study of sedimentary, geochemical, and geophysical data from industrial offshore wells in the Levant Basin, which recovered a sedimentary record of deep-basin Mediterranean evaporites deposited during the MSC. In combination with previous observations of the MSC throughout the Mediterranean Basin, our results promote the need for a new chronological model. Remarkably, the one-kilometer-thick lower part of the evaporitic unit is composed of essentially pure halite, except for a thin transitional anhydrite layer at its base. The halite is undisturbed and homogeneous, lacking diverse features apparent in more proximal sections, indicating a deep-sea depositional environment. We find that distinct, meters-thick non-evaporitic intervals interbedded with the halite, previously thought to be clastic layers, are diatomites. While XRD analysis confirms an increase in clastic components in these sediments, they are composed primarily of well-preserved marine and freshwater planktonic diatoms. The occurrence of marine planktonic diatoms in these intervals indicates the input of Atlantic waters into the Mediterranean Basin during the deposition of the massive halite unit. Seismic stratigraphy and well-log cyclostratigraphy further support deep basin halite deposition, which started about 300 kyr earlier than widely assumed (~5.97 Ma). We propose that halite deposition in the deep Mediterranean took place during stage 1 of the MSC, rather than being limited to the short 50 kyr MSC acme when sea level was presumably at its lowest. Thus, brine formation, salt precipitation, and faunal extinction occurred at least in part in a deep, non-desiccated basin, with a restricted yet open Mediterranean-Atlantic connection that allowed inflow of oceanic water. We observe an increase in heavy minerals and reworked fauna within the clastic-evaporitic, Interbedded Evaporites of the basinal MSC section, and argue that these settings correspond in the deep basins with a significant sea-level drawdown during stage 2 of the MSC, as observed in the marginal sections. This correlation is corroborated by astrochronology and chemostratigraphic markers, such as the distribution of n-alkanes and biomarker-based thermal maturity indices. The Levant deposits indicate that high sea level and partial connectivity with global oceans promoted the deposition of deep-basin deep-water halite, while sea-level drawdown promoted deposition of reworked and transported material from the margins into deep Mediterranean basins. This study modifies the current understanding of the mechanisms governing salt deposition throughout the MSC with implications for other evaporitic events in the geologic record

Organic geochemistry for SH#1 core pertaining to OAE2 forest fires

This data set was used to trace changes in forest fire frequency, plant ecology, and climate in the Western US and Western Interior Seaway (WIS) through Oceanic Anoxic Event 2 (OAE2; ~94 Ma). Samples were present in the SH#1 core, which was recovered in the summer of 2014 near Big Water, Utah (37.158466°N, 111.531947°W). Biomarker data was produced using gas chromatography-mass spectrometry between February 2016 and April 2019, and is presented either in concentrations normalized to total organic carbon (ug/g TOC), or as a ratio of biomarker/s to other biomarker/s. Combustion-derived polycyclic aromatic hydrocarbons (PAHs) were used to trace forest fires, land plant-derived long chain n-alkanes (LCAs) were used to trace changes in the input of terrestrial organic matter to the WIS, and the average chain length (ACL) of LCAs helped to deduce changes in plant community and precipitation in the Western US. The R markdown contains the processing of raw biomarker data and calculations for ratios, as well as the code for carbon mass balance equations that assess the significance of fires during OAE2

Compound-specific carbon isotope results from the SH#1 core analyzed and processed at University of Colorado Boulder

This data set was used to trace changes in carbon cycling and productivity in the Western Interior Seaway (WIS) through Oceanic Anoxic Event 2 (OAE2; 94 Ma). Samples were present in the SH#1 core, which was recovered in the summer of 2014 near Big Water, Utah (37.158466°N, 111.531947°W). Compound-specific carbon isotope data was produced using gas chromatography-isotope ratio mass spectrometry (GCIRMS) between February 2017 and November 2018. Raw data were used in calculations described in Boudinot et al., (in review) to estimate changes in the carbon isotopic composition of marine DIC and atmospheric CO2, as well as changes in pCO2, throughout OAE2, all of which are outlined in the data file. Assumptions and estimates of environmental conditions impacting these estimated carbon-cycle relevant metrics are presented. These data demonstrate both the methods and outputs of using compound-specific carbon isotope analyses to estimate local and global carbon cycle dynamics during an interval of global change during Earth history. Specifically, the data file includes (A) core depth in meters of the SH#1 core, (B) the name of the compound identified using GC-MS (in Boudinot et al., 2020, Neritic ecosystem response to Oceanic Anoxic Event 2 in the Cretaceous Western Interior Seaway, USA. Palaeogeography, Palaeoclimatology, Palaeoecology, 546, 109673), (C) the calibrated mean carbon isotopic composition of the compound in per mil relative to VPDB, (D) the preparation undertaken prior to analysis on GC-IRMS (i.e., either having undergone urea adduction or not), (E) the carbon isotopic composition of carbonate from the same depth as presented in Jones et al. (2019, Astronomical pacing of relative sea level during Oceanic Anoxic Event 2: Preliminary studies of the expanded SH#1 core, Utah, USA. GSA Bulletin, 131 (9-10): 1702–1722) or as analyzed in Boudinot et al. (in review) (described in methods, indicated in figures), (F) the analytical standard deviation of the carbon isotopic composition of compounds based on either duplicate analysis, or on the predicted standard error based on the calibration ("true_d13c_pred_se" in isoprocessor), (G) the number of duplicate compound-specific analyses, with NA indicating that only one analysis was performed and thus the predicted standard error based on the calibration was used to estimate the standard deviation, (H-I) the minimum and maximum net carbon isotope fractionation during carbon fixation and biosynthesis for the autotroph responsible for each lipid synthesis, in per mil, (J-L) the minimum, maximum, and average fixed inorganic carbon pool carbon isotopic composition estimated using the equations presented in Boudinot et al. (in review), (M) temperature estimate in degrees kelvin, (N) the calculated temperature-dependent carbon isotope fractionation of CO2 with respect to bicarbonate in per mil, (O) the carbon isotopic composition of marine DIC based on the carbon isotopic composition of carbonate for that depth in per mil, (P-R) the minimum, maximum, and average carbon isotopic composition of primary photosynthate calculated using the equation described in Boudinot et al. (in review) in per mil, (S) the carbon isotopic fractionation associated with photosynthesis in per mil, (T) the solubility constant of CO2 based on salinity and temperature estimates relevant to the SH#1 core, (U-V) the high and low b-value estimates used as constants to represent the role of productivity in modulating carbon isotope fractionation during photosynthesis, (W) the carbon isotopic composition of aqueous CO2 estimated using the carbon isotopic composition of carbonate, (X) the carbon isotopic composition of aqueous CO2 estimated using the carbon isotopic composition of biomarkers, (Y) epsilon p estimated using b values, the calculated carbon isotopic composition of primary photosynthate, and the calculated carbon isotopic composition of aqueous CO2 estimated using carbonate, (Z-AA) the high and low estimates of the aqueous concentration of CO2 in seawater at the SH#1 core location using epsilon p estimates from the carbon isotopic composition of carbonate, in micromol CO2/kg, (AB-AC) the high and low estimates of pCO2 using the estimate of aqueous CO2 derived from the carbon isotopic composition of carbonate, in ppmv, (AD) epsilon p estimated using b values, the calculated carbon isotopic composition of primary photosynthate, and the calculated carbon isotopic composition of aqueous CO2 estimated using biomarkers, (AE-AF) the high and low estimates of the aqueous concentration of CO2 in seawater at the SH#1 core location using epsilon p estimates from the carbon isotopic composition of biomarkers, in micromol CO2/kg, and (AG-AH) the high and low estimates of pCO2 using the estimate of aqueous CO2 derived from the carbon isotopic composition of biomarkers, in ppmv

Trace element and calcareous nannofossil assemblage of the Smoky Hollow (SH#1) core in south central Utah

Trace element data from the Smoky Hollow #1 core drilled across the Cenomanian-Turonian boundary near Big Water, south-central Utah in 2014. Ground bulk samples were analyzed via Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) in the Laboratory for Isotopes and Metals in the Environment (LIME) at The Pennsylvania State University. Results are given with both raw (bulk) and normalized to Zr to correct for detrital input. The data include nannofossil assemblages from the Cenomanian-Turonian boundary of the Smoky Hollow (SH#1) core in south central Utah. For assemblage studies, slides were made from more dilute solutions so that counts could be conducted. Nannofossil specimens were observed under a Carl Zeiss Axioskop 2 Plus light microscope at a magnification of 1000x and identified using standard taxonomy as described by Perch-Nielsen et al. (1985). Specimens one-half the size of a coccolith or larger were identified and a total of over 31,000 specimens were counted

Calcareous nannofossil assemblage of the Smoky Hollow (SH#1) core in south central Utah

The data include nannofossil assemblages from the Cenomanian-Turonian boundary of the Smoky Hollow (SH#1) core in south central Utah. For assemblage studies, slides were made from more dilute solutions so that counts could be conducted. Nannofossil specimens were observed under a Carl Zeiss Axioskop 2 Plus light microscope at a magnification of 1000x and identified using standard taxonomy as described by Perch-Nielsen et al. (1985). Specimens one-half the size of a coccolith or larger were identified and a total of over 31,000 specimens were counted

Raw trace element data of the Smoky Hollow (SH#1) core in south central Utah

Trace element data from the Smoky Hollow #1 core drilled across the Cenomanian-Turonian boundary near Big Water, south-central Utah in 2014. Ground bulk samples were analyzed via Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) in the Laboratory for Isotopes and Metals in the Environment (LIME) at The Pennsylvania State University. Results are given with both raw (bulk) and normalized to Zr to correct for detrital input

Zirconium normalized trace element data of the Smoky Hollow (SH#1) core in south central Utah

Trace element data from the Smoky Hollow #1 core drilled across the Cenomanian-Turonian boundary near Big Water, south-central Utah in 2014. Ground bulk samples were analyzed via Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) in the Laboratory for Isotopes and Metals in the Environment (LIME) at The Pennsylvania State University. Results are given with both raw (bulk) and normalized to Zr to correct for detrital input

Chronology with a pinch of salt : Integrated stratigraphy of Messinian evaporites in the deep Eastern Mediterranean reveals long-lasting halite deposition during Atlantic connectivity

The Messinian Salinity Crisis (MSC; 5.97–5.33 Ma) is considered an extreme environmental event driven by changes in climate and tectonics, which affected global ocean salinity and shaped the biogeochemical composition of the Mediterranean Sea. Yet, after more than 50 years of research, MSC stratigraphy remains controversial. Recent studies agree that the transition from the underlying pre-evaporite sediments to thick halite deposits is conformal in the deep Eastern Mediterranean Basin. However, the age of the base and the duration of halite deposition are still unclear. Also disputed is the nature of the intermediate and upper MSC units, which are characterized as periods of increased clastic deposition into the Eastern Mediterranean based on marginal outcrops and seismic data. We provide a multidisciplinary study of sedimentary, geochemical, and geophysical data from industrial offshore wells in the Levant Basin, which recovered a sedimentary record of deep-basin Mediterranean evaporites deposited during the MSC. In combination with previous observations of the MSC throughout the Mediterranean Basin, our results promote the need for a new chronological model. Remarkably, the one-kilometer-thick lower part of the evaporitic unit is composed of essentially pure halite, except for a thin transitional anhydrite layer at its base. The halite is undisturbed and homogeneous, lacking diverse features apparent in more proximal sections, indicating a deep-sea depositional environment. We find that distinct, meters-thick non-evaporitic intervals interbedded with the halite, previously thought to be clastic layers, are diatomites. While XRD analysis confirms an increase in clastic components in these sediments, they are composed primarily of well-preserved marine and freshwater planktonic diatoms. The occurrence of marine planktonic diatoms in these intervals indicates the input of Atlantic waters into the Mediterranean Basin during the deposition of the massive halite unit. Seismic stratigraphy and well-log cyclostratigraphy further support deep basin halite deposition, which started about 300 kyr earlier than widely assumed (~5.97 Ma). We propose that halite deposition in the deep Mediterranean took place during stage 1 of the MSC, rather than being limited to the short 50 kyr MSC acme when sea level was presumably at its lowest. Thus, brine formation, salt precipitation, and faunal extinction occurred at least in part in a deep, non-desiccated basin, with a restricted yet open Mediterranean-Atlantic connection that allowed inflow of oceanic water. We observe an increase in heavy minerals and reworked fauna within the clastic-evaporitic, Interbedded Evaporites of the basinal MSC section, and argue that these settings correspond in the deep basins with a significant sea-level drawdown during stage 2 of the MSC, as observed in the marginal sections. This correlation is corroborated by astrochronology and chemostratigraphic markers, such as the distribution of n-alkanes and biomarker-based thermal maturity indices. The Levant deposits indicate that high sea level and partial connectivity with global oceans promoted the deposition of deep-basin deep-water halite, while sea-level drawdown promoted deposition of reworked and transported material from the margins into deep Mediterranean basins. This study modifies the current understanding of the mechanisms governing salt deposition throughout the MSC with implications for other evaporitic events in the geologic record