Pockmark asymmetry and seafloor currents in the Santos Basin offshore Brazil

Abstract:

Pockmarks form by gas/fluid expulsion into theocean and are preserved under conditions of negligible sedi-mentation. Ideally, they are circular at the seafloor and sym-metrical in profile. Elliptical pockmarks are more enigmatic.They are associated with seafloor currents while asymmetry isconnected to sedimentation patterns. This study examinesthese associations through morphological analysis of newmultibeam data collected across the Santos continental slopeoffshore Brazil in 2011 (353–865 mbsl). Of 984 pockmarks,78% are both elliptical and asymmetric. Geometric criteriadivide the pockmarks into three depth ranges that correlatewith a transition between two currents: the Brazil Currenttransfers Tropical Water and South Atlantic Central Watersouthwestwards while the Intermediate Western BoundaryCurrent transfers Antarctic Intermediate Water northeast-wards. It is suggested that the velocity of seafloor currentsand their persistence dictate pockmark ellipticity, orientationand profile asymmetry. Fast currents (>20cm/s) are capable ofmaintaining pockmark flank steepness close to the angle ofrepose. These morphological expressions present direct evi-dence for an edge effect of the South Atlantic Subtropical.


Reference:
SCHATTNER, U.; LAZAR, M.; SOUZA, Luiz Antonio Pereira de; BRINK, U. ten.; MAHIQUES, M.M. Pockmark asymmetry and seafloor currents in the Santos Basin offshore Brazil. Geo-Marine Letters: An International Journal of Marine Geology, p.1-8, Sept., 2016. DOI 10.1007/s00367-016-0468-0.


Access article in the journal website:
www.researchgate.net/publication/308080822_Pockmark_asymmetry_and_seafloor_currents_in_the_Santos_Basin_offshore_Brazil

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