January 21, 2020

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Marlies van der Schee Coauthored a Paper on Precessional Cyclicity of Seawater Pb Isotopes in the Late Miocene Mediterranean for Journal Paleoceanography and Paleoclimatology

Marlies van der Schee, Ph.D. (UK) coauthored a paper entitled "Presessional Cyclicity of Seawater Pb Isotopes in the Late Miocene Mediterranean" for publication in the journal Paleoceanography and Paleoclimatology on December 12, 2019.

Marlies' coauthors are Sevasti Modestou, Ph.D., University of Bergen (Norway); Marcus Gutjahr, Ph.D., GEOMAR Helmholtz Centre (Germany); Rob Ellam, Ph.D., Scottish Universities Environmental Research Centre (UK); and Rachel Flecker, Ph.D., PGCertHE University of Bristol (UK).

Marlies is a Senior Staff Professional and an Environmental Consultant focused on soil and groundwater contamination. She has contributed to research that has been published in academic journals, including Terra Nova and Marine Geology.

Published by the American Geophysical Union (AGU), the journal Paleoceanography and Paleoclimatology includes original research articles dealing with all aspects of understanding and reconstructing Earth's past climate and environments from the Precambrian to modern analogs.

The AGU is an international nonprofit scientific association with 60,000 members in 137 countries. It was established in 1919 by the National Research Council and operated as an unincorporated affiliate of the National Academy of Sciences for more than 50 years.


Astronomical tuning in the Mediterranean region is primarily based on organically‐mediated proxies, such as cyclicity of organic rich layers or changes in foraminiferal assemblages. Both during and post deposition, organic proxies can be affected by complex processes not immediately related to the changes in precession (insolation) they are assumed to reflect. Here we present an isotopic proxy which exhibits precessional cyclicity yet is inorganic. Seawater lead (Pb) isotope records over four precessional cycles between 6.6 and 6.5 Ma, from bulk sediment leachates of three Messinian, circum‐Mediterranean marginal locations, show variations consistent with precessional cyclicity. During insolation minima, the Pb isotope signatures from all three sites converge to similar values, suggesting a regional process is affecting all three locations at that time. Data from the marginal sites are compared with new data from ODP Site 978 and published data from a variety of geological archives from the Mediterranean region to determine the mechanism(s) causing the observed variability. While the comparisons are not fully conclusive, the timing of events suggest that increased dust production from North Africa during insolation minima is the most likely control. This hypothesis implies that authigenic marine Pb isotope records have the potential to provide a reliable inorganic tie point for Mediterranean cyclostratigraphy where sub‐precessional resolution is required. An inorganic tie point could also provide the means to resolve long‐standing problems in Mediterranean stratigraphy on precessional and sub‐precessional timescales which have been obscured due to post‐depositional changes (e.g., sapropel burn‐down) or suboptimal ecological conditions (e.g., the Messinian Salinity Crisis).

More Information

Learn more about the article: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018PA003538
Learn more about AGU: https://connect.agu.org/home
For consultation regarding precessional cyclicity, contact Marlies at This email address is being protected from spambots. You need JavaScript enabled to view it.
Learn more about Marlies at: https://www.linkedin.com/in/marlies-van-der-schee-2090b561/?originalSubdomain=uk