EGU23-10010, updated on 24 Apr 2023
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Alkenones confirmed in sediments from high southern latitudes during the Cretaceous and Paleocene: results from the Transkei Basin (IODP Site U1581)

Kelsey Doiron1, Simon Brassell1, Peter Bijl2, Thomas Wager3, Jens Herrle4, Gabriele Uenzelmann-Neben5, Steven Bohaty6, Laurel Childress7, and the Expedition 392 Science Party*
Kelsey Doiron et al.
  • 1Earth & Atmospheric Sciences, Indiana University, Bloomington, IN, USA
  • 2Department of Earth Sciences, Utrecht University, Utrecht, NL
  • 3Lyell Centre, Heriot-Watt University, Edinburgh, UK
  • 4Institute of Geosciences, Goethe-University, Frankfurt, DEU
  • 5Alfred Wegener Institute, Bremerhaven, DEU
  • 6Institute of Earth Sciences, Heidelberg University, Heidelberg, DEU
  • 7International Ocean Discovery Program, Texas A&M University, College Station, TX, USA
  • *A full list of authors appears at the end of the abstract

Preliminary examination of the biomarker composition of Paleocene to Campanian (~63-74 Ma) organic-rich sediments recovered from the Transkei Basin (Hole U1581B; 35° 41’S, 29° 39’E), offshore South Africa, during IODP Expedition 392 reveals suites of alkenones and alkyl alkenoates derived from haptophyte algae. This discovery augments evidence for the temporal continuity of their occurrence since the early Aptian and expands their paleogeographic range to high southern latitudes (~60°S) during the Cretaceous and Paleocene. In addition, the similarity of alkenone distributions between Maastrichtian and Danian samples suggests a conformity in the biosynthetic pathways for their production across the K/Pg boundary likely attesting to the survival of their source haptophytes and recovery after the extinction event. Alkenone distributions in the Transkei Basin sediments are dominated by series of C37 to C40 diunsaturated components and remain broadly consistent throughout the Cretaceous to Paleocene stratigraphic  succession. The presence of both the C38 alkadien-2-one and C39 alkadien-3-one represents the earliest recognition of these compounds thereby extending the advent for biosynthesis of both methyl and ethyl alkenones to the Campanian (~74 Ma). These sediments also contain C37 methyl and both C38 and C40 ethyl alkadienoates. No C37, C38 or C39 triunsaturated alkenones were detected in the Paleocene through Campanian succession but minor amounts of a C40 alkatrien-3-one were confirmed in Cretaceous samples based on its elution time and diagnostic mass spectrum. This finding raises the question why only the C40 triunsaturated component is observed, coupled with pervasive evidence that C37 to C39 triunsaturated alkenones emerge after the Early Eocene Climatic Optimum (EECO). Among extant haptophytes, C40 alkenones occur in species within phylogenic Group II, notably Isochrysis, but are absent in extant marine species comprising phylogenic Group III. These observed distributions of alkenones in the marine realm can be best explained as evidence for contributions from both Isochrysidaceae and Noelaerhabdaceae following their divergence in the early Cretaceous.  

Expedition 392 Science Party:

Scientific Participants in IODP Expedition 392

How to cite: Doiron, K., Brassell, S., Bijl, P., Wager, T., Herrle, J., Uenzelmann-Neben, G., Bohaty, S., and Childress, L. and the Expedition 392 Science Party: Alkenones confirmed in sediments from high southern latitudes during the Cretaceous and Paleocene: results from the Transkei Basin (IODP Site U1581), EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-10010,, 2023.