@article{burgener_hyland_reich_scotese_2023, title={Cretaceous climates: Mapping paleo-Koppen climatic zones using a Bayesian statistical analysis of lithologic, paleontologic, and geochemical proxies}, volume={613}, ISSN={["1872-616X"]}, DOI={10.1016/j.palaeo.2022.111373}, abstractNote={The Cretaceous Period (145 to 66 Ma) was a prolonged warmhouse to hothouse period characterized by high atmospheric CO2 conditions, elevated surface temperatures, and an enhanced global hydrologic cycle. It provides a case study for understanding how a hothouse climate system operates, and is an analog for future anthropogenic climate change scenarios. This study presents new quantitative temperature and precipitation proxy datasets for nine key Cretaceous time slices (Berriasian/Valanginian, Hauterivian/Barremian, Aptian, Albian, Cenomanian, Turonian, Coniacian/Santonian, Campanian, Maastrichtian), and a new geostatistical analysis technique that utilizes Markov Chain Monte Carlo algorithm and Bayesian hierarchical models to generate high resolution, quantitative global paleoclimate reconstructions from these proxy datasets, with associated uncertainties. Using these paleoclimate reconstructions, paleo-Köppen (-Geiger) climate zone maps are produced that provide new insights into the changing spatial and temporal climate patterns during the Cretaceous. These new paleoclimate reconstructions and paleo-Köppen climate maps provide new insight into the timing of the initiation of the Early Cretaceous equatorial humid belt over Gondwana and reveal temporal shifts in the width of the subtropical arid belts from the Early to mid- to Late Cretaceous. A comparison of these proxy-based reconstructions and model simulations of Cretaceous climate reveal continued proxy/model differences. In addition, the methodology developed for this study can be applied to other time periods, providing a framework for better understanding ancient climate, environments, and ecosystems.}, journal={PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY}, author={Burgener, Landon and Hyland, Ethan and Reich, Brian J. and Scotese, Christopher}, year={2023}, month={Mar} }
 @article{padgett_hyland_west_burgener_greenwood_basinger_2023, title={Paleogene Paleohydrology of Ellesmere and Axel Heiberg Islands (Arctic Canada) From Palustrine Carbonates}, volume={38}, ISSN={["2572-4525"]}, DOI={10.1029/2023PA004609}, abstractNote={AbstractAncient greenhouse periods are useful analogs for predicting effects of anthropogenic climate change on regional and global temperature and precipitation patterns. A paucity of terrestrial data from polar regions during warm episodes challenges our understanding of polar climate responses to natural/anthropogenic change and therefore our ability to predict future changes in precipitation. Ellesmere and Axel Heiberg Islands in the Canadian Arctic preserve terrestrial deposits spanning the late Paleocene to middle Eocene (59–45 Ma). Here we expand on existing regional sedimentology and paleontology through the addition of stable (δ13C, δ18O) and clumped (Δ47) isotope analyses on palustrine carbonates. δ13C isotope values range from −4.6 to +12.3‰ (VPDB), and δ18O isotope values range from −23.1 to −15.2‰ (VPDB). Both carbon and oxygen isotope averages decrease with increasing diagenetic alteration. Unusually enriched carbon isotope (δ13C) values suggest that analyzed carbonates experienced repeated dissolution‐precipitation enrichment cycles, potentially caused by seasonal fluctuations in water availability resulting in summer carbonate dissolution followed by winter carbonate re‐precipitation. Stable isotopes suggest some degree of precipitation seasonality or reduction in winter water availability in the Canadian Arctic during the Paleogene. Clumped (Δ47) temperature estimates range from 52 to 121°C and indicate low temperature solid‐state reordering of micritic samples and diagenetic recrystallization in sparry samples. Average temperatures agree with vitrinite reflectance data for Eureka Sound Group and underlying sediments, highlighting structural complexity across the region. Broadly, combined stable and clumped isotope data from carbonates in complex systems are effective for describing both paleoclimatic and post‐burial conditions.}, number={10}, journal={PALEOCEANOGRAPHY AND PALEOCLIMATOLOGY}, author={Padgett, Ashly B. and Hyland, Ethan G. and West, Christopher K. and Burgener, Landon K. and Greenwood, David R. and Basinger, James F.}, year={2023}, month={Oct} }
 @article{burgener_hyland_griffith_mitasova_zanno_gates_2021, title={An extreme climate gradient-induced ecological regionalization in the Upper Cretaceous Western Interior Basin of North America}, volume={133}, ISSN={["1943-2674"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85111073513&partnerID=MN8TOARS}, DOI={10.1130/B35904.1}, abstractNote={Abstract
               The Upper Cretaceous Western Interior Basin of North America provides a unique laboratory for constraining the effects of spatial climate patterns on the macroevolution and spatiotemporal distribution of biological communities across geologic timescales. Previous studies suggested that Western Interior Basin terrestrial ecosystems were divided into distinct southern and northern communities, and that this provincialism was maintained by a putative climate barrier at ∼50°N paleolatitude; however, this climate barrier hypothesis has yet to be tested. We present mean annual temperature (MAT) spatial interpolations for the Western Interior Basin that confirm the presence of a distinct terrestrial climate barrier in the form of a MAT transition zone between 48°N and 58°N paleolatitude during the final 15 m.y. of the Cretaceous. This transition zone was characterized by steep latitudinal temperature gradients and divided the Western Interior Basin into warm southern and cool northern biomes. Similarity analyses of new compilations of fossil pollen and leaf records from the Western Interior Basin suggest that the biogeographical distribution of primary producers in the Western Interior Basin was heavily influenced by the presence of this temperature transition zone, which in turn may have impacted the distribution of the entire trophic system across western North America.}, number={9-10}, journal={GEOLOGICAL SOCIETY OF AMERICA BULLETIN}, author={Burgener, Landon and Hyland, Ethan and Griffith, Emily and Mitasova, Helena and Zanno, Lindsay E. and Gates, Terry A.}, year={2021}, pages={2125–2136} }
 @article{bernasconi_daeron_bergmann_bonifacie_meckler_affek_anderson_bajnai_barkan_beverly_et al._2021, title={InterCarb: A Community Effort to Improve Interlaboratory Standardization of the Carbonate Clumped Isotope Thermometer Using Carbonate Standards}, volume={22}, ISSN={["1525-2027"]}, DOI={10.1029/2020GC009588}, abstractNote={AbstractIncreased use and improved methodology of carbonate clumped isotope thermometry has greatly enhanced our ability to interrogate a suite of Earth‐system processes. However, interlaboratory discrepancies in quantifying carbonate clumped isotope (Δ47) measurements persist, and their specific sources remain unclear. To address interlaboratory differences, we first provide consensus values from the clumped isotope community for four carbonate standards relative to heated and equilibrated gases with 1,819 individual analyses from 10 laboratories. Then we analyzed the four carbonate standards along with three additional standards, spanning a broad range of δ47 and Δ47 values, for a total of 5,329 analyses on 25 individual mass spectrometers from 22 different laboratories. Treating three of the materials as known standards and the other four as unknowns, we find that the use of carbonate reference materials is a robust method for standardization that yields interlaboratory discrepancies entirely consistent with intralaboratory analytical uncertainties. Carbonate reference materials, along with measurement and data processing practices described herein, provide the carbonate clumped isotope community with a robust approach to achieve interlaboratory agreement as we continue to use and improve this powerful geochemical tool. We propose that carbonate clumped isotope data normalized to the carbonate reference materials described in this publication should be reported as Δ47 (I‐CDES) values for Intercarb‐Carbon Dioxide Equilibrium Scale.}, number={5}, journal={GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS}, author={Bernasconi, S. M. and Daeron, M. and Bergmann, K. D. and Bonifacie, M. and Meckler, A. N. and Affek, H. P. and Anderson, N. and Bajnai, D. and Barkan, E. and Beverly, E. and et al.}, year={2021}, month={May} }
 @article{burgener_hyland_huntington_kelson_sewall_2019, title={Revisiting the equable climate problem during the Late Cretaceous greenhouse using paleosol carbonate clumped isotope temperatures from the Campanian of the Western Interior Basin, USA}, volume={516}, ISSN={["1872-616X"]}, DOI={10.1016/j.palaeo.2018.12.004}, abstractNote={Greenhouse climates such as the Late Cretaceous period provide important reference frames for understanding modern anthropogenic climate change. Upper Cretaceous terrestrial climate proxies have been interpreted as evidence for “equable” climates with reduced seasonal variations in temperature. However, climate models have largely failed to reproduce these reconstructions unless parameters such as atmospheric CO2 concentrations are set to unreasonable values. To help resolve such model-proxy disagreements, we reconstruct mean annual range in temperature (MART) for the Campanian (~75 Ma) Kaiparowits (south-central Utah) and Two Medicine (northwest Montana) Formations using warmest mean monthly temperature reconstructions from the clumped isotope composition of paleosol carbonate nodules, and reconstructions of local mean annual air temperatures from other methods. An evaluation of the applicability of bulk elemental soil geochemistry temperature proxies in these deposits supports the use of previous leaf physiognomy-based estimates of mean annual temperature for our MART reconstructions. We test the validity of several common assumptions made in reconstructing MART in two novel ways. First, MART is commonly calculated as twice the difference between local mean annual air temperature and warmest mean monthly temperature, and we validate this method by estimating modern MART for a range of environments using climate reanalysis data. Second, we constrain the effect of radiative soil heating on our soil carbonate temperature estimates by showing that for most environments likely to be preserved in the geologic record, summer soil temperatures are <3 °C higher than air temperatures. Our findings suggest that warmest mean monthly temperatures were 30 to 35 ± 4 °C at the two study sites, and that MART was 21 to 29 °C for the Kaiparowits Formation, and 21 to 27 °C for the Two Medicine Formation. Mid-latitude Late Cretaceous MARTs were similar to modern ranges in mid-latitude seasonal temperature, and much (>9 °C) larger than previous proxy reconstructions of Late Cretaceous MART. These results add to a growing body of literature showing that terrestrial MART during ancient greenhouse periods was not significantly different from modern seasonal temperature variations. Finally, the similarity in MART between the Kaiparowits and Two Medicine formations suggests that latitudinal changes in MART did not contribute to the faunal provincialism that has been proposed by some paleontologists.}, journal={PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY}, author={Burgener, Landon and Hyland, Ethan and Huntington, Katharine W. and Kelson, Julia R. and Sewall, Jacob O.}, year={2019}, month={Feb}, pages={244–267} }