Tectonic development, sedimentation and paleoceanography of the Scan Basin (southern Scotia Sea, Antarctica)

• Published in: Global and planetary change 2014-12, Vol.123, p.344-358
• Main Authors: Pérez, Lara F., Lodolo, Emanuele, Maldonado, Andrés, Hernández-Molina, F. Javier, Bohoyo, Fernando, Galindo-Zaldívar, Jesús, Lobo, F. José, Burca, Mihai
• Format: Article
• Language: English
• Subjects: Antarctica; Basin analysis; Basins; Bottom currents; Deep water; Exchange; Joints; Marine; Reconstruction; Reflection seismic and gravity; Scotia Sea; Sedimentation; Seismic phenomena; Weddell Sea
• ISSN: 0921-8181; 1872-6364
• DOI: 10.1016/j.gloplacha.2014.06.007

The N–S trending Scan Basin is the easternmost deep basin north of the South Scotia Ridge, which is a geologically complex structural elevation that hosts the strike-slip boundary between the Scotia and Antarctic plates. We characterized the main morpho-structural features of the basin by analyzing the available multichannel seismic reflection profiles. The reconstruction of the seismo-stratigraphy reveals the growth patterns of the Scan Basin. Seismic data and gravity modeling support the interpretation that the basin is mainly floored by oceanic crust, however its northern and southern provinces exhibit different seismic attributes. Stratigraphic calibrations with adjacent regions together with the distribution of sedimentary units indicate that this basin was formed by rifting processes and subsequent spreading accretion from the Oligocene to the Miocene. This age attribution suggests that the Scan Basin might be one of the oldest oceanic basins of the southern Scotia Sea—possibly coeval with the Eocene–Oligocene opening of the Drake Passage. The basin is the most direct connection between the Weddell Sea and the Scotia Sea, whereas the stratigraphic features reveal the occurrence of major paleoceanographic changes. The initial phases of the evolution were influenced by mass-transport and turbidite processes of sediment supply from the nearby continental margins of the eastern tip of the Antarctic Peninsula. From the Middle Miocene to the Present-day, the eastward motion of the basin due to plate tectonic and the connection with the Weddell Sea through gateways enabled instauration of the overflow of Weddell Sea Deep Water (WSDW) into the Scan Basin. The WSDW forced the northward migration of the Circumpolar Deep Water (CDW) and became progressively dominant, controlling depositional patterns. The results that we report here should prove essential for understanding the formation of the Scotia Sea, the beginning of the Scotia Arc fragmentation, and the increasing role played by Weddell Sea/Scotia Sea water-mass exchange. [Display omitted] •Two steps of opening: Oligocene in the south and Miocene in the north•Particular initial growth patterns due to older age and continental proximity•Middle Miocene new sedimentary stacking pattern: dominant along-slope processes•Reconstruction of the connections between the Weddell Sea and the Scotia Sea•Onset of a huge contourite fan via overflow of the WSDW across the Bruce Passage