Call to Participate: Expedition 505S: ENIGMA: ExploratioN Into a Global early Miocene Anomaly

IODP³ Expedition 505S is a SPARC (Scientific Projects using ocean drilling ARChives) expedition involving sampling and analysis of early Miocene sediments from legacy IODP, ODP and DSDP cores recovered from the Atlantic Ocean and Caribbean Sea and held in the Bremen Core Repository (BCR) in Germany and the Gulf Coast Repository (GCR) in Texas. We invite applications from scientists with interest and expertise relevant to the objectives of the expedition to apply for membership of the IODP³ Expedition 505S Science Team. This call is open to applicants based in nations currently participating in IODP³ or in any nation currently or previously a member of a scientific ocean drilling programme.

The Miocene Epoch (23.03–5.33 Ma) was a pivotal period of climate and biosphere evolution, yet the early Miocene (23–17 Ma) remains poorly understood due to a scarcity of high-resolution records. Recent studies suggest that around 19 Ma, a major but enigmatic biotic and environmental shift occurred, marked by significant declines in shark diversity, restructuring of marine vertebrate communities, and widespread planktonic and benthic ecosystem changes across trophic levels. These shifts coincided with geochemical anomalies, including a contraction of tropical oxygen-deficient zones, disruptions in primary productivity, and isotopic signals indicative of climate perturbations. The underlying mechanisms driving these changes remain unclear, as do their broader implications for oceanic ecosystem evolution as a whole.

The ENIGMA expedition aims to resolve the causes and consequences of this early Miocene anomaly by analyzing comprehensive marine sediment records. By integrating micropaleontological, geochemical, and sedimentological data from legacy scientific ocean drilling cores, we will assess how paleoceanographic changes influenced primary productivity, nutrient cycling, and marine biodiversity. A focus on complete early Miocene sequences, particularly in the Atlantic sector, will provide a basin-wide perspective on these transformations. Our findings will enhance understanding of the early Miocene's role in shaping the modern ocean system and contribute critical insights into ecosystem resilience and climate change dynamics over geological timescales.

While we welcome applicants from all relevant scientific backgrounds, we are particularly interested in recruiting expertise in the following areas: taxonomy/assemblage/biostratigraphy of diatoms, planktonic and benthic foraminifera, calcareous nannoplankton, radiolaria, ichthyoliths, ostracods, and marine/terrestrial palynology; XRF analyses; organic and inorganic geochemistry, including boron, litihium, and neodymium isotopic analysis, among other isotopic systems; sedimentology; age model development using magnetostratigraphy, cyclostratigraphy and astrochronology; Earth system modelling; stratigraphic correlation; tectonics, structural geology and/or geophysics; and science communication.

We invite applications by scientists with expertise in each of these fields, both for “Repository and Laboratory” and “Laboratory-only roles” (see below). We also welcome applications from researchers proposing complementary research projects that go beyond the stated research objectives or wishing to apply additional or novel techniques not listed above.

For more information please read the full call in the PDF below. The Scientific Prospectus can also be found via the link below, and on the Expedition 505S Expedition Page

Applications must be submitted by 23:59 GMT on Friday 23 January 2026 using the IODP³ Gateway system. The Gateway can be accessed via Apply to Participate on the IODP³ webpage, and more information on the content required for applications to this call is also available in the IODP³ Guide for Applicants.

A webinar will be held on Thursday 4 December 2025 at 11am (GMT) to enable the community to find out more about Expedition 505S. A recording of this webinar will be posted online below soon after the webinar takes place.

Any questions about the application process please contact applications@iodp3.org