loading page

Evidence for multiple middle Eocene warming events in the Lutetian-Bartonian chemostratigraphic record from the southwest Pacific
  • +4
  • Joyeeta Bhattacharya,
  • Laia Alegret,
  • Edoardo Dallanave,
  • Gerald Dickens,
  • Thomas Westerhold,
  • Laurence Yeung,
  • Claudia Agnini
Joyeeta Bhattacharya
University of Oklahoma Norman Campus

Corresponding Author:[email protected]

Author Profile
Laia Alegret
Universidad de Zaragoza
Author Profile
Edoardo Dallanave
University of Bremen
Author Profile
Gerald Dickens
Trinity College Dublin
Author Profile
Thomas Westerhold
MARUM - University Bremen
Author Profile
Laurence Yeung
Rice University
Author Profile
Claudia Agnini
University of Padua
Author Profile


Climate and carbon cycling during the Eocene were complex, as inferred from records of stable isotopes and carbonate accumulation in marine sediment sections. Following a now well-documented early Eocene interval characterized by extreme global warmth and numerous short-term C-cycle perturbations documented in many sediment sections across the world, the ‘warmhouse’ climate state of the middle-late Eocene remains far less studied. In particular, the middle Eocene was punctuated by an event of significant global warming and seafloor carbonate dissolution (Middle Eocene Climate Optimum or MECO, ca. ~40.5 Ma). Over the last decade, studies from multiple sites in the Atlantic have suggested another abrupt and transient (and potentially a hyperthermal) warming event seemingly associated with a C-cycle perturbation at ~41.5 Ma, referred to as the Late Lutetian Thermal Maximum (LLTM). While both MECO and LLTM punctuate the post-EECO long-term cooling, their isotopic expression and duration are fundamentally different. At present, a dearth of continuous middle Eocene chemostratigraphic records limits our understanding of warming events like MECO and especially, the global extent of the LLTM. In this study, we develop an isotope stratigraphy of Lutetian-Bartonian age sediments from three different sites in the southwest Pacific region, two of which were drilled during IODP Expedition 371 in the Tasman Sea and a third that derives from field work in New Caledonia. We identify long-term changes in carbon and oxygen isotope records, possibly related to 405 Ky eccentricity cycles, and identify the stratigraphic expression of the LLTM and MECO. These new middle Eocene chemostratigraphic records from the southwest Pacific help to establish the global nature and relevance of multiple warming events that occurred during the ‘warmhouse’ climatic conditions of middle Eocene and highlight the utility of sedimentary carbon isotopes as a tool for chemostratigraphy and deciphering causes of past global changes.