Palaeoclimate reconstruction of the last greenhouse-icehouse transition based on geochemical and micropalaeontological records from Central Mississippi, US Gulf Coastal Plain

During the Eocene-Oligocene Transition (EOT; ~34.4-33.7 Ma), the Earth experienced a major shift in climate state, from so called “greenhouse” to “icehouse” conditions, with the first formation of the modern continental-scale ice sheet on Antarctica (Oi-1 event: ~33.7 Ma). This transition was associated with deep-sea cooling, glacioeustatic sea level fall, worldwide regressions, along with major disturbances in the global carbon cycle and ecosystems. To investigate this climatic disruption, high- resolution coccolith fraction (<20 μm) carbonate stable oxygen (δ18O) and carbon (δ13C) isotope records (~7 ka resolution), palynological and calcareous nannofossil assemblage (~26 ka resolution) records, and bulk sediment X-ray fluorescence analyses (<10 ka resolution) have been generated from a continuously cored (~137 m) and substantially expanded (~4.7 cm ka-1) succession of upper Eocene-lower Oligocene (~4 Ma) mid-shelf marine clays from the central Mississippi, US Gulf Coastal Plain – the Mossy Grove Core (MGC). Based on a refined age-depth model, this multiproxy analysis revealed that the increasing export of nutrients from the Southern Ocean to the tropical and sub-tropical oceans enhanced marine primary production in these regions, further leading to increased sequestration of atmospheric CO2 through an invigorated biological pump. We also found evidence that extraterrestrial impacts may have induced sulfate-aerosol-driven climate forcing, triggering positive feedback mechanisms, and intensifying and/or sustaining the cooling. Further analysis also demonstrated that a significant sea level fall (~34.5 Ma) preceded the Oi-1 event by ~800 ka and represents the first stage of large-scale expansion of the East Antarctica Ice Sheet. This challenges the current view that the dynamics of the EOT are dominated by global cooling during the earliest stages, which then precondition the system to continental-scale ice-sheet expansion in the later stages. We also propose that the earliest stages of the major EOT eustatic sea-level fall had a disproportionate effect on global biogeochemistry, by causing the first major incision of organic- and nutrient-rich coastal low lands that had been accreting under warm, high sea-level greenhouse conditions for tens of millions of years

Benthic foraminifera stable isotope data for the Mossy Grove sediment core

Sample preparation for benthic foraminiferal stable-isotope analyses: Sediment amples were prepared and analyzed at Kochi University. Samples were washed through a 63 μm screen with Calgon in tapwater, and the residue was dried at 50 °C. Specimens of U. jacksonensis were picked from the >150 µm fraction of the residues, and were found to be present in 38 sediment samples. The specimens are well-preserved appearing transparent to translucent in color under the light microscope (Figure S2). Using a Keyence VHX-2000 digital microscope and a JEOL JSM-6500F scanning electron microscope, the preservation of examined specimens was assessed. The light microscopic image is focus stacking. To extend this record down core, a further five samples were prepared at the University of Birmingham. These samples were dried in a low-temperature oven at 40°C for approximately one week in order to obtain a dry bulk sediment weight and then washed over a 63 µm sieve with de-ionised water. The coarse fraction (>63 µm) was dried in the oven and then dry sieved at 250-300 µm and individuals of the infaunal benthic foraminifera genus Uvigerina picked (wherever possible U. jacksonensis was selected). Any sample with more than two individuals was analyzed for stable isotopes (>10 µg). The stable carbon (δ13C) and oxygen (δ18O) isotope analysis of five benthic foraminiferal samples prepared at the University of Birmingham were performed at the British Geological Survey, Keyworth, UK on a dual inlet, gas source, isotope ratio mass spectrometer. The carbonate analysis method involves reacting the carbonate sample with anhydrous phosphoric acid to liberate CO2. All data are reported against Vienna Pee Dee Belemnite standard (VPDB). Calibration of the in-house standard with NBS-19 shows the analytical precision is < ±0.01‰ for both isotope ratios. For the 38 benthic foraminifera samples prepared at Kochi University, we used a Finnigan MAT253 mass-spectrometer system with a Kiel III carbonate device in the Center for Advanced Marine Core Research/Kochi Core Center (CMCR/KCC), Kochi University. Between 2–7 individuals were measured in each sample and were cleaned at least three times, using milli-Q and methanol in a sonic bath. NBS-19 and ANU-m2 were used as stable isotopes standards. The precisions of the measurements (1σ) were 0.18‰ and 0.08‰ for δ13C and δ18O respectively, calculated using 24 repeat measurements of the standard

Micropaleontological and geochemical dataset of shallow-marine deposits in central Mississippi, US Gulf Coastal Plain

Here we provide extensive micropaleontological and geochemical dataset of shallow-marine deposits that includes palynology and palynomorph component, carbonate fine-fraction stable-isotope, benthic foraminiferal stable-isotope, X-ray fluorescence (XRF), and glycerol dialkyl glycerol tetraether (GDGT) data. Samples were originally collected from the Mossy Grove core, nearby Jackson, central Mississippi, US Gulf Coastal Plain, between August 19, 1991 and September 5, 1991 (Dockery III et al., 1991). The dataset was generated between October 2015 and June 2019 and covers the latest Eocene and earliest Oligocene (~37.5-33.1 million years ago). These data were intended to yield unique multi-proxy records of the critical Eocene-Oligocene Transition, the most prominent climate event in the last 100 million years of Earth's history. Methods for age model, palynology and palynomorph component, carbonate fine-fraction stable-isotope, benthic foraminiferal stable-isotope, X-ray fluorescence (XRF), and glycerol dialkyl glycerol tetraether (GDGT) data follow De Lira Mota et al. (in review)

Fine fraction (<20 µm) bulk stable isotope data for the Mossy Grove sediment core

Sample preparation for carbonate fine-fraction stable-isotope data: A total of 444 bulk sediment samples, taken at ~30 cm spacing from the Mossy Grove Core (MGC), were processed at the University of Birmingham. The sediment was sieved over a 20 µm stainless steel mesh, with the fine fraction passing through the sieve captured on ultra-fine-grade filter paper and air dried. The sediment residue (>20 µm) was then transferred to 50 ml centrifuge tubes and organic matter within this fine fraction removed by overnight reaction with 5% sodium hypochlorite (NaClO) solution. The sample was then spun down at 4,500 rpm (6,800 × g) and the supernatant discarded. The sample was then washed 2-3 times with de-ionized water – each wash consisting of resuspension, agitation and then centrifuging and discarding of the solution as above - until a neutral pH was established. Samples were then weighed to provide sufficient sample mass for sample analysis. The stable carbon (δ13C) and oxygen (δ18O) isotope analysis of 444 fine-fraction sediment samples prepared at the University of Birmingham were performed at the British Geological Survey, Keyworth, UK on a dual inlet, gas source, isotope ratio mass spectrometer. The carbonate analysis method involves reacting the carbonate sample with anhydrous phosphoric acid to liberate CO2. All data are reported against Vienna Pee Dee Belemnite standard (VPDB). Calibration of the in-house standard with NBS-19 shows the analytical precision is < ±0.01‰ for both isotope ratios

Selected palynomorph-based indicators for the Mossy Grove sediment core

Palynology: Altogether, 112 samples collected at ~1.2 m intervals from the Mossy Grove borehole between ~17.0 and 152.0 m were treated with 40% HCl for 30 minutes and 60% HF for 24 hours to dissolve carbonates and disaggregate the rock matrix, and sieved over a 10 µm nylon mesh to retain the HF effluent from the material. A second HCl treatment was applied to remove any precipitate, followed by a final sieving over a 10 µm mesh. The remaining sample material (>10 µm) was subjected to oxidation (70% HNO3 for exactly two minutes) to remove pyrite, debris and any unstructured organic material from the palynomorphs, followed by another sieving over a 10 µm mesh to remove any HNO3 effluent. A final cleaning treatment was undertaken with a combination of domestic and industrial detergents. Using swirling techniques, palynomorphs in each sample were then concentrated and Bismark brown was added to make them more visible with light microscopy. Finally, the samples were sieved into two size fractions, 10-30 μm (concentrating spores and pollen) and 30 μm+ (concentrating dinocysts), and then mounted on separate 22x22 mm coverslips, which were glued to a glass slide using Norland optical adhesive. In this work, only the coarse-fraction content of each slide was analyzed. A pilot survey of these slides revealed that the acid and oxidizing technique yielded higher diversity than their non-acid and non-oxidizing counterparts61. The coarse/fine-fraction sorting follows the premise that pollen and spores size mostly ranges between 11 and 44 µm, whereas dinocysts range between 20 and 150 µm62. All slides are stored in the collection of the School of Geography, Earth and Environmental Sciences, University of Birmingham, and are available upon request from Tom Dunkley Jones. Palynomorph components: In this work, the coarse-fraction content of each slide was analyzed with a Zeiss transmitted light microscope (400x magnification). Two hundred dinocyst specimens were counted in each sample, along with any spores, pollen, algae (prasinophyceae and chlorophyceae), zoomorphs/zooclasts, phytoclasts and amorphous organic matter. Only palynomorphs that were more than 50% complete and not obscured either by air bubbles or organic debris were considered 63. Reworked acritarchs and amorphous organic matter were excluded from the final sum of palynomorphs and thereby from the percentage calculations. Palynomorph-based paleoenvironmental indicators include the peridinioid/gonyaulacoid dinocyst (P/G) ratio 64–70, and salinity reconstructions based on the relative abundance of the high-salinity favoring Homotryblium spp. 43,71–73 and in the ratio of short-to-long process of dinocyst genus Spiniferites 74–78

X-ray fluorescence data for the Mossy Grove sediment core

Elemental composition of the sediment core was determined using two XRF techniques. 2,098 samples on the original core section were directly analyzed at a resolution of ~1.2 cm across the interval 17.1-109.4 m with a hand-held XRF analyzer at the core store of the Mississippi Department of Environmental Quality, in Jackson, Mississippi. A further 179 samples were collected every 20-30 cm downcore, spanning the interval 106.8-151.6 m, and were subsequently finely ground and dried before analysis as pressed powders in wax pellets. Pellets were analyzed with a Bruker S8 TIGER XRF spectrometer with an 8 min analysis time, at the School of Chemistry, University of Birmingham. We selected the (Al+Fe+K+Ti)/Ca ratio as a paleoenvironmental indicator of terrigenous-derived versus marine planktonic carbonate sediment 79,80. The two methodologies were cross-calibrated over an interval of overlap between 106.8 and 109.4 m, with a total of ~80 samples, spanning a range of compositions, cross-correlated from both analysis methods

BIT Index, GDGT-derived OPTiMAL and BAYSPAR paleotemperatures for the Mossy Grove sediment core

Samples were processed for GDGTs at the Birmingham Molecular Climatology Laboratory, University of Birmingham. Lipids were extracted from ~10-15 g of homogenized sediment by ultrasonic extraction using dichloromethane (DCM):methanol (3:1). The total lipid extract was fractionated by silica gel chromatography using n-hexane, n-hexane:DCM (2:1), DCM, and methanol to produce four separate fractions, the last of which contained the GDGTs. Procedural blanks were also analyzed to ensure the absence of laboratory contaminants. Samples were filtered using hexane:isopropanol (99:1) through a 0.4 µm PTFE filter (Alltech part 2395), before being dried under a continuous stream of N2. Samples were then sent to the University of Bristol for analysis by LC-APCI-MS. HPLC-APCI-MS analyses were conducted at the National Environmental Isotope Facility, Organic Geochemistry Unit, School of Chemistry, University of Bristol, with a ThermoFisher Scientific Accela Quantum Access triple quadrupole MS in selected ion monitoring (SIM) mode. Normal phase separation was achieved using two ultra-high performance silica columns (Acquity UPLC BEH HILIC columns, 50 mm × ID 2.1 mm × 1.7 µm, 130 Å; Waters) were fitted with a 2.1 mm × 5 mm guard cartridge after Hopmans et al. (2016). The HPLC pump was operated at a flow rate of 200 µL min-1. GDGT determinations were based on single injections. A 15 µL aliquot was injected via an autosampler, with analyte separation performed under a gradient elution. The initial solvent hexane:iso-propanol (IPA) (98.2:1.8 v/v) eluted isocratically for 25 min, followed by an increase in solvent polarity to 3.5 % IPA in 25 min, and then by a sharp increase to 10 % IPA in 30 min (Hopmans et al., 2016). A 45 min washout period was applied between injections, whereby the column was flushed by injecting 25 µL hexane:isopropanol (99:1 v/v). GDGT peaks were integrated manually using Xcalibur software. In-house generated standard solutions were measured daily to assess system performance. One peat standard was run in a sequence for every 10 samples and integrated in the same way as the unknowns. Selected ion monitoring (SIM) was used to monitor abundance of the [M+H] + ion of the different GDGTs instead of full-scan acquisition in order to improve the signal-to-noise ratio and therefore yield higher sensitivity and reproducibility. SIM parameters were set to detect the protonated molecules of isoprenoid and branched GDGTs using the m/z (Schoon et al., 2013). The majority of sediments were found to contain a full range of both isoprenoid and branched GDGTs. Sea surface temperature (SST) estimations from GDGT assemblages are show based on two methodologies: the BAYSPAR Bayesian regression model of Tierney and Tingley (2014, 2015) using the 'analogue' version for deep-time applications; and, the OPTiMAL Gaussian process model of Dunkley Jones et al. (2020). When plotting BAYSPAR SSTs we distinguish samples with BIT indices greater than and less than 0.4, as high BIT can be associated with a small warm bias (Weijers et al., 2006). For the OPTiMAL model we apply its own internal screening criteria that quantifies the extent that fossil GDGT assemblages are non-analogue relative to the modern calibration data, using the Dnearest criteria with a cut-off value of 0.5. All but one pre-NIE GDGT assemblages have Dnearest values that exceed 0.5, whereas eight samples above this level have values less than 0.5.Only OPTiMAL SST data that pass the Dnearest screening criteria are shown

NEOTROPICAL XENARTHRANS: a data set of occurrence of xenarthran species in the Neotropics

Xenarthrans—anteaters, sloths, and armadillos—have essential functions for ecosystem maintenance, such as insect control and nutrient cycling, playing key roles as ecosystem engineers. Because of habitat loss and fragmentation, hunting pressure, and conflicts with domestic dogs, these species have been threatened locally, regionally, or even across their full distribution ranges. The Neotropics harbor 21 species of armadillos, 10 anteaters, and 6 sloths. Our data set includes the families Chlamyphoridae (13), Dasypodidae (7), Myrmecophagidae (3), Bradypodidae (4), and Megalonychidae (2). We have no occurrence data on Dasypus pilosus (Dasypodidae). Regarding Cyclopedidae, until recently, only one species was recognized, but new genetic studies have revealed that the group is represented by seven species. In this data paper, we compiled a total of 42,528 records of 31 species, represented by occurrence and quantitative data, totaling 24,847 unique georeferenced records. The geographic range is from the southern United States, Mexico, and Caribbean countries at the northern portion of the Neotropics, to the austral distribution in Argentina, Paraguay, Chile, and Uruguay. Regarding anteaters, Myrmecophaga tridactyla has the most records (n = 5,941), and Cyclopes sp. have the fewest (n = 240). The armadillo species with the most data is Dasypus novemcinctus (n = 11,588), and the fewest data are recorded for Calyptophractus retusus (n = 33). With regard to sloth species, Bradypus variegatus has the most records (n = 962), and Bradypus pygmaeus has the fewest (n = 12). Our main objective with Neotropical Xenarthrans is to make occurrence and quantitative data available to facilitate more ecological research, particularly if we integrate the xenarthran data with other data sets of Neotropical Series that will become available very soon (i.e., Neotropical Carnivores, Neotropical Invasive Mammals, and Neotropical Hunters and Dogs). Therefore, studies on trophic cascades, hunting pressure, habitat loss, fragmentation effects, species invasion, and climate change effects will be possible with the Neotropical Xenarthrans data set. Please cite this data paper when using its data in publications. We also request that researchers and teachers inform us of how they are using these data