The International Ocean Discovery Program (IODP) is now accepting applications for scientific participants on Expedition 401: Mediterranean-Atlantic Gateway Exchange, aboard the JOIDES Resolution, 10 December 2023–9 February 2024.

Amphibious drilling proposal: Investigating Miocene Mediterranean-Atlantic Gateway Exchange (IMMAGE)

Marine gateways play a critical role in the exchange of water, heat, salt and nutrients between oceans and seas. The advection of dense waters helps drive global thermohaline circulation and, since the ocean is the largest of the rapidly exchanging CO₂ reservoirs, this advection also affects atmospheric carbon concentration. Changes in gateway geometry can therefore significantly alter both the pattern of global ocean circulation and associated heat transport and climate, as well as having a profound local impact. Today, the volume of dense water supplied by Atlantic-Mediterranean exchange through the Gibraltar Strait is amongst the largest in the global ocean. For the past five million years this overflow has generated a saline plume at intermediate depths in the Atlantic that deposits distinctive contouritic sediments in the Gulf of Cádiz and contributes to the formation of North Atlantic Deep Water. This single gateway configuration only developed in the early Pliocene. During the Miocene, a wide, open seaway linking the Mediterranean and Atlantic evolved into two narrow corridors: one in northern Morocco; the other in southern Spain. Formation of these corridors permitted Mediterranean salinity to rise and a new, distinct, dense water mass to form and overspill into the Atlantic for the first time. Further restriction and closure of these connections resulted in extreme salinity fluctuations in the Mediterranean, leading to the formation of the Messinian Salinity Crisis salt giant.

IODP Expedition 401 is one part of an amphibious drilling proposal that also includes coring on land as part of the International Continental Drilling Program (ICDP). The Investigating Miocene Mediterranean-Atlantic Gateway Exchange (IMMAGE) drilling proposal is designed to recover a complete record of Atlantic-Mediterranean exchange from its Late Miocene inception to its current configuration. This will be achieved by coring Miocene offshore sediments and borehole logging at three sites on either side of the Gibraltar Strait during IODP Expedition 401 and from the two precursor connections now exposed on land in southern Spain and northern Morocco with ICDP.

IMMAGE has three primary scientific objectives which will be met through drilling the three IODP holes during Expedition 401 and the two ICDP holes:

1. To document the time at which the Atlantic first started to receive a distinct overflow from the Mediterranean and to evaluate quantitatively its role in Late Miocene global climate and regional environmental change.
2. To recover a complete record of Atlantic-Mediterranean exchange before, during and after the Messinian Salinity Crisis and to evaluate the causes and consequences of this extreme oceanographic event, locally, regionally and globally.
3. To test our quantitative understanding of the behavior of ocean plumes during the most extreme exchange in Earth’s history.

For more information on the expedition science objectives and the JOIDES Resolution expedition schedule, see http://iodp.tamu.edu/scienceops/. This site includes links to individual expedition web pages with the original IODP proposals and expedition planning information.

Original proposals: 895-Full3 & 895-Add2 PDF

The International Ocean Discovery Program (IODP) is now accepting applications for scientific participants on Expedition 402: Tyrrhenian Continent-Ocean Transition, aboard the JOIDES Resolution, 9 February–8 April 2024.

Expedition 402 will investigate the temporal and spatial evolution of a continent-ocean transition (COT), from breakup to robust magmatism and subsequent mantle exhumation with closely time-related magmatism. The Tyrrhenian basin is the youngest basin of the Western Mediterranean, forming in the late Miocene to recent by continental extension related to rollback of the ESE-SE migrating Apennine subduction system. The basement of the Tyrrhenian basin has been dredged along bathymetric highs and the stratigraphy is reasonably well known from three prior drilling expeditions (DSDP Legs 13 and 42 and ODP Leg 107). Recent geophysical and seismic data support the presence of magmatic rocks formed during the early COT phase, and of subsequently exhumed mantle. The youth of the basin results in a modest sediment cover which facilitates sampling of the peridotitic and magmatic basement across the conjugated COT of the basin with unprecedented spatial resolution. Six sites are selected to core into the basement of the basin, followed by downhole logging. The recovered material and data will address the cruise objectives, which include the kinematics of the opening, the crust and mantle deformation mechanisms, and the relationship of melting products to the exhumed mantle.

The drilling program of Expedition 402 is designed to target six sites along a west-east and north-south transect. Drill cores will recover peridotitic basement at each site, followed by downhole logging. The recovered material and data will address the five primary scientific objectives:

1. Determine the kinematics and geometry in space and time of the extensional deformation in the basin.
2. Establish the timing and origin of the associated magmatism.
3. Establish the rheology, deformation patterns and timing of mantle exhumation.
4. Determine the compositional evolution and heterogeneity of the mantle source.
5. Test current models of continental lithosphere rifting and of COT formation.

For more information on the expedition science objectives and the JOIDES Resolution expedition schedule, see http://iodp.tamu.edu/scienceops/. This site includes links to individual expedition web pages with the original IODP proposals and expedition planning information.

Original proposals: 927-Full2 & 927-Add3 PDF