Article
Geosciences, Multidisciplinary
Vittoria Lauretano, Alan T. Kennedy-Asser, Vera A. Korasidis, Malcolm W. Wallace, Paul J. Valdes, Daniel J. Lunt, Richard D. Pancost, B. David A. Naafs
Summary: The study presents a semi-continuous terrestrial temperature record spanning from the middle Eocene to the early Oligocene, using bacterial molecular fossils preserved in lignites from southeast Australia. Results show a gradual decline in mean annual temperatures in southeast Australia, with a step cooling across the Eocene/Oligocene boundary, likely driven by changes in pCO2. Climate model simulations support these findings, indicating the importance of pCO2 decline in influencing temperatures in southeast Australia during this time period.
Article
Geosciences, Multidisciplinary
Weiwei Xue, Xiumian Hu, Anlin Ma, Eduardo Garzanti, Wendong Liang, Lulu Hao, Qiang Wang
Summary: The controversial history of Indian subduction beneath Asia is crucial to understand the Himalayan orogeny and the geodynamic process of continental subduction in general. This study presents new information from the Oligocene-Pliocene Shiquanhe Basin in the Tibetan Plateau, indicating the development of an orogen-parallel rift in southern Tibet during the Oligocene Epoch. The subsidence of twin basins in this area may have been caused by the steepening subducting Indian continental slab or by the passage of a wave of dynamic topography during continued subduction.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Geochemistry & Geophysics
Weiqi Yao, Stefan Markovic, Adina Paytan, Andrea M. Erhardt, Ulrich G. Wortmann
Summary: The study explores the role of biogeochemical sulfur cycling during the Eocene-Oligocene transition, reporting a decline in seawater sulfate isotope values. Quantitative modeling suggests a significant reoxidation of sulfide from shelf sediments, affecting marine pH and alkalinity. The numbers are similar in magnitude to those observed during Pleistocene glaciations.
EARTH AND PLANETARY SCIENCE LETTERS
(2021)
Article
Geosciences, Multidisciplinary
Luca Giacomo Costamagna
Summary: This study presents the field investigations on the sedimentary evolution of the Mulargia-Escalaplano late- to post-Variscan basin in Sardinia, which provides detailed information on the relationships between sedimentary cycles from Late Pennsylvanian to Middle Triassic. The findings reveal the interplay between tectonics and sedimentation, and suggest that the sedimentary response in the basin matches the evolution of the southern Variscan chain branch. The basin preserves continental deposits organized in cycles, with weak unconformities and influenced by drying climates, indicating a progressive widening of the basin and migration of the depocentre to the southeast.
GEOLOGICAL MAGAZINE
(2022)
Article
Environmental Sciences
Gabriele Uenzelmann-Neben, Karsten Gohl, Katharina Hochmuth, Ulrich Salzmann, Robert D. Larter, Claus-Dieter Hillenbrand, Johann P. Klages
Summary: Seismic imaging of a sediment drift on the Amundsen Sea Embayment shelf suggests that the growth of the West Antarctic Ice Sheet was hindered by the incursion of relatively warm circumpolar deep water as early as the Eocene-Oligocene transition. The study also concludes that the West Antarctic Ice Sheet has likely experienced a strong oceanic influence on its dynamics since its formation.
COMMUNICATIONS EARTH & ENVIRONMENT
(2022)
Article
Geosciences, Multidisciplinary
Agathe Toumoulin, Delphine Tardif, Yannick Donnadieu, Alexis Licht, Jean-Baptiste Ladant, Lutz Kunzmann, Guillaume Dupont-Nivet
Summary: The Eocene-Oligocene Transition (EOT) is a key moment in Cenozoic climate history, associated with changes in seasonality. Records suggest that the EOT is associated with winter cooling and increased seasonality. Simulations show that pCO(2) decrease, Antarctic ice-sheet formation, and increased continentality play important roles in explaining the changes in seasonality.
CLIMATE OF THE PAST
(2022)
Article
Geosciences, Multidisciplinary
Emily J. Tibbett, Natalie J. Burls, David K. Hutchinson, Sarah J. Feakins
Summary: This study reevaluates the proxy temperature records and model simulations in the southern high latitudes during the Eocene-Oligocene transition (EOT). It finds that the cooling during the EOT was primarily driven by a decrease in pCO(2). The multi-model ensemble suggests a 30% to 33% decrease in pCO(2) is needed to best fit the temperature proxies.
PALEOCEANOGRAPHY AND PALEOCLIMATOLOGY
(2023)
Article
Geology
Erica Rubino, Andrew Leier, Elizabeth J. Cassel, S. Bruce Archibald, Zachary Foster-Baril, David L. Barbeau
Summary: The Lower Eocene strata in the southern Canadian Cordillera hinterland were deposited in multiple compartmentalized basins in alluvial fan, fluvial, lacustrine, and paludal environments. Detrital zircons with ages around 50 Ma are interpreted to be derived from volcanic activity, while another population with ages between 145 and 200 Ma indicates different sediment sources and paleodrainages within the southern Canadian Cordillera.
SEDIMENTARY GEOLOGY
(2021)
Article
Geosciences, Multidisciplinary
Qianjiang Xing, David Munday, Andreas Klocker, Isabel Sauermilch, Joanne Whittaker
Summary: This study investigates the sensitivity of the Southern Ocean to paleo-latitudinal migrations and strengthening of the wind stress using an ocean model. The results show that changes in latitudinal position and wind stress can impact the Southern Ocean circulation, leading to dominance of subtropical waters in high latitudes, further warming of the Antarctic coast, shrinking of the subpolar gyres, and cooling of surface waters.
CLIMATE OF THE PAST
(2022)
Article
Geosciences, Multidisciplinary
J. A. Adeoye, V. O. Jolayemi, S. O. Akande
Summary: Sedimentological and foraminiferal paleoecological studies of the Ogwashi-Asaba Formation in the Issele-Uku area of the Anambra Basin, southern Nigeria, indicate the presence of a fluvio-deltaic setting during the formation of lignites and clastic rocks. Benthic foraminiferal species dominate the shale units, with low population and diversity likely due to harsh conditions. The benthic foraminifera habitat suggests a middle-to-inner neritic marine environment for the shales, while the granulometric results indicate a fluvial environment for the sandstone and a deltaic environment for the lignite.
JOURNAL OF PALAEOGEOGRAPHY-ENGLISH
(2022)
Article
Geochemistry & Geophysics
Erika Tanaka, Kazutaka Yasukawa, Junichiro Ohta, Yasuhiro Kato
Summary: Multiple short-term global warming events occurred in the early Eocene, and chemical weathering of continental silicate rocks may have played a key role in mitigating these events. However, the effectiveness of chemical weathering during other transient hyperthermals remains poorly understood.
GEOCHIMICA ET COSMOCHIMICA ACTA
(2022)
Article
Geology
Heiko Hueneke, F. Javier Hernandez-Molina, Francisco J. Rodriguez-Tovar, Estefania Llave, Domenico Chiarella, Anxo Mena, Dorrik A. V. Stow
Summary: The detailed study of calcareous contourites in a sedimentary succession on Cyprus provides valuable insights for distinguishing between different facies, including bi-gradational contourite sequences and normally-graded sequences in turbidite beds. Sediment provenance, depositional texture, and preservation of traction structures are key factors in differentiating these facies.
Article
Geosciences, Multidisciplinary
Funda Akgun, Mine Sezgul Kayseri-Ozer, Erdogan Tekin, Baki Varol, Sevket Sen, Erdal Herece, Ibrahim Gundogan, Koray Sozeri, Muhammed Sami Us
Summary: The Eregli-Ulukisla Basin in the southeastern Central Anatolian Cenozoic basins is divided into two sub-basins with different palaeotopographic conditions, showcasing changes in flora and climate during the Late Miocene. The study reveals a transition from archaic to advanced angiosperm morphology in pollen assemblages along with recurrent arid phases during sediment deposition.
GEOLOGICAL JOURNAL
(2021)
Article
Geosciences, Multidisciplinary
Xuxuan Ma, Zhiqin Xu, Joseph G. Meert, Zuolin Tian, Haibing Li
Summary: This study investigates the timing and mechanisms of Indo-Asian collisional events by examining the geological features and petrological data of the Gangdese belt in southern Tibet, revealing a high-flux magmatic event around 50-47 Ma that triggered high-temperature metamorphism. The synchronous occurrence of high-flux magmatism and high-temperature metamorphism in the Himalayan-Tibetan orogen during the early Eocene coinciding with the Indo-Asian collision process suggests the closure of the Neotethys Ocean along the southern margin of the Lhasa terrane in the same period.
GEOLOGICAL SOCIETY OF AMERICA BULLETIN
(2021)
Article
Paleontology
Alexandre Lourenco Souza, Valesca Maria Portilla Eilert, Thays Souza Lima Fidalgo, Isabelle Penha Reis, Claudia Gutterres Vilela, Joao Graciano Mendonca Filho
Summary: The study analyzed late middle Eocene to early Oligocene radiolarian assemblages in sediments from ODP Site 1090 in the Atlantic Sector of the Southern Ocean. Three new subzones were proposed, improving biostratigraphic resolution in the region. The synchronous first occurrences of Axoprunum irregularis and Eucyrtidium antiquum in the Southern Ocean can be used to estimate the Eocene/Oligocene boundary. Other radiolarian events show diachronous patterns among different sites in the region.
MARINE MICROPALEONTOLOGY
(2021)