The structure of the upper sediment cover in the central atlantic based on high-resolution seismoacoustic data

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Resumo

The study is dedicated to the geological interpretation of high-resolution seismoacoustic data acquired in the Central Atlantic during the 60th cruise of the RV Akademik Ioffe. Seismic facies of abyssal plane deposits, contourites, gravitites, and sediment waves have been identified based on specific characteristics of the seismic structure of the upper sediment cover. Geological interpretation was conducted considering the results of lithological studies of sediment cores collected during research cruises of the Shirshov Institute of Oceanology, Russian Academy of Sciences, as well as deep-sea drilling data. The role of gravity-driven processes in the formation of near-surface deposits is most significant in the region adjacent to the continental margin of South America. In the entire study area, bottom currents are considered as one of the main agents of sediment cover formation. They are responsible both for the deposition of contourite drifts and stratified hemipelagic sediments.

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Sobre autores

A. Roslyakov

Shirshov Institute of Oceanology, Russian Academy of Sciences; Lomonosov Moscow State University

Autor responsável pela correspondência
Email: arosl60@mail.ru
Rússia, Moscow; Moscow

N. Dmitrevsky

Shirshov Institute of Oceanology, Russian Academy of Sciences

Email: arosl60@mail.ru
Rússia, Moscow

R. Ananyev

Shirshov Institute of Oceanology, Russian Academy of Sciences

Email: arosl60@mail.ru
Rússia, Moscow

Bibliografia

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2. Fig. 1. Research area. Black line – expedition route. Yellow circles – location of sections with profile fragments shown in Figs. 2–6. White circles – ODP/DSDP wells and their numbers.

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3. Fig. 2. Deposits of a hilly contourite drift. 1 and 2 are different generations of contourites, occurring with angular unconformity. Area 2 (the position of the fragment is shown in Fig. 1).

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4. Fig. 3. Gravity deposits. a) Landslide body (arrow). Features – chaotic record, uneven roof convex upward, pronounced sliding surface. Section 1 in Fig. 1. b) Density flow deposits (blue arrow). Features – acoustically transparent record, erosional nature of the base. Red arrows – landslide blocks on the adjacent slope of the underwater ridge. Section 4 in Fig. 1.

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5. Fig. 4. Sedimentary waves in the outer zone of the Amazon alluvial fan. The red arrow indicates the direction of material removal by density currents, the black dotted lines connect the wave tops; their slope illustrates the displacement of the tops upstream of the flow (reverse migration). Fragment 3 in Fig. 1.

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6. Fig. 5. Negative form in the bottom relief (arrow) associated with the bottom current. The oval is presumably an accumulative alluvial ridge. Section 5 in Fig. 1.

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7. Fig. 6. Low-amplitude faults in the upper part of the section (red dotted line), associated with an uplift in the bottom relief. Above – without interpretation, below – with interpretation. Fragment 6 in Fig. 1.

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