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During Integrated Ocean Drilling Program Expedition 339, five sites were drilled in
the Gulf of Cádiz and two sites were drilled off the West Iberian margin. The Gulf
of Cádiz was targeted for drilling as a key location for the investigation of Mediterranean
Outflow Water (MOW) through the Strait of Gibraltar (Gibraltar Gateway) and its influence
on global circulation and climate. The gulf is also a prime area for understanding
the effects of tectonic activity on evolution of the Gibraltar Gateway and margin
sedimentation. There is significant climatic and tectonic control on the evolution
of MOW and bottom-current activity. The Gulf of Cádiz is the world’s premier contourite
laboratory and thus presents an ideal testing ground for the contourite paradigm.
Following recovery of more than 4.5 km of contourite cores from six of the sites under
direct MOW influence, existing models for contourite deposition are found to be sound.
Further study of these models will undoubtedly allow us to resolve outstanding issues
of depositional processes, drift budgets, and recognition of fossil contourites in
the ancient record onshore. The expedition also verified the presence of contourite
sands that are clean and well sorted in a number of settings, including those created
by local diapiric activity. These sands represent a completely new and important deepwater
sand type that, where found deeper in the subsurface, could provide a significant
exploration target for potential oil and gas reservoirs. At the deeper water site
off southwest Portugal (the Shackleton site), we drilled five separate holes and recovered
two complete splice sets of Quaternary hemipelagic sedimentation over the past 1.4
m.y. These will form the basis of detailed shore-based collaboration to establish
a high-precision marine reference section of Quaternary climate change for comparison
with other marine sections and with established ice-core and terrestrial records.