Geological and Geophysical Investigation of Contourite Systems from the Central and Southern Atlantic during Cruise 52 of the R/V Akademik Ioffe

Abstract

The geological and geophysical expedition duringcruise 52 of the R/V Akademik Ioffe was organized bythe Shirshov Institute of Oceanology, Russian Academyof Sciences, according to the expeditionary programof FASO Russia; it was combined with transit ofthe vessel after the end of the Arctic tourist season,from September 29 to November 8, 2016 (port of exit:Gdansk, Poland; port of entry: Ushuaia, Argentina).The objectives of the expedition were formulatedby scientific supervisor I.O. Murdmaa. The scientificparty included 12 persons. The expedition was led byE.V. Ivanova and her deputy D.G. Borisov. The tasksof the expedition were carried out by the geologicalteam (head E.A. Ovsepyan) and seismic profiling andmeteorology team (head N.V. Libina).The expedition was aimed at high-resolution seismicprofiling along the ship?s track and in the centralpart of the Ioffe Drift, with collection of sedimentcores and grab samples in order to investigate theimpact of bottom circulation on sedimentation.Geological works included sediment sampling tostudy contourites (sediments formed by contour currents)and other lateral sedimentation products (turbidites,gravitites). The studies were carried out intransform valleys of the Mid-Atlantic Ridge (MAR),on the Ioffe contourite drift in the southern BrazilBasin, and on contourite terraces of the southernArgentine continental slope. The stations of sedimentsampling by gravity corers (127 mm in diameter) andan Okean 0.25 grab sampler were selected on seismicprofiles with a high-resolution SES-2000 deep subbottomecho sounder (4?7 kHz). Positioning of thevessel at the scheduled sites was assisted by GPS. Themethods of preliminary onboard analyses during theexpedition, including 5487 NM of seismic profiling,were performed along the vessel track starting from theexit to the Atlantic, except for the economic zones ofEuropean countries and Argentina, and including194 miles in a survey area in the central Ioffe Drift.Twenty-seven geological sampling stations were made(Fig. 1) with the collection of 3 sediment cores and17 grab samples or minicores.