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Alkenone-derived estimates of Cretaceous pCO2
Si, W.; Novak, J.; Richter, N.; Polissar, P.; Ma, R.; Santos, E.; Nirenberg, J.; Herbert, T.D.; Aubry, M.-P. (2024). Alkenone-derived estimates of Cretaceous pCO2. Geology (Boulder Colo.) 52(7): 555-559. https://dx.doi.org/10.1130/g51939.1
In: Geology. Geological Society of America: Boulder. ISSN 0091-7613; e-ISSN 1943-2682, more
Peer reviewed article  
Available in  Authors 
Author keywords
    algae; alkenones; Atlantic Ocean; C-13; carbon; carbon dioxide; Coccolithophoraceae; Cretaceous; Deep Sea Drilling Project; Demerara Rise; DSDP Site 534; Equatorial Atlantic; Galicia Bank; IPOD; isotopes; ketones; Leg 76; Leg 103; Leg 207; Mesozoic; microfossils; North Atlantic; Northeast Atlantic; Northwest Atlantic; Ocean Drilling Program; ODP Site 638; ODP Site 1257; organic compounds; paleoatmosphere; paleoclimatology; stable isotopes; West Atlantic
Authors  Top 
  • Si, W.
  • Novak, J.
  • Richter, N., more
  • Polissar, P.
  • Ma, R.
  • Santos, E.
  • Nirenberg, J.
  • Herbert, T.D.
  • Aubry, M.-P.
Abstract
    Alkenones are long-chain ketones produced by phytoplankton of the order Isochrysidales. They are widely used in reconstructing past sea surface temperatures, benefiting from their ubiquitous occurrence in the Cenozoic ocean. Carbon isotope fractionation (εp) between alkenones and dissolved inorganic carbon may also be used as a proxy for past atmospheric pCO2 and has provided continuous pCO2 estimates back to ca. 45 Ma. Here, an extended occurrence of alkenones from ca. 130 Ma is reported. We characterize the molecular structure and distribution of these Mesozoic alkenones and evaluate their potential phylogenetic relationship with Cenozoic alkenones. Using δ13C values of the C37 methyl alkenone (C37:2Me), the first alkenone-based pCO2 estimates for the Mesozoic are derived. These estimates suggest elevated pCO2 with a range of 548–4090 ppm (908 ppm median) during the super-greenhouse climate of the Early Cretaceous, in agreement with phytane-based pCO2 reconstructions. Finally, insights into the identity of the Cretaceous coccolithophores that possibly synthesized alkenones are also offered.
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