Late Pliocene Mega Debris Flow Deposit and Related Fluid Escapes Identified on the Antarctic Peninsula Continental Margin by Seismic Reflection Data Analysis |
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Authors: | P Diviacco M Rebesco A Camerlenghi |
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Institution: | (1) Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS), Borgo Grotta Gigante 42/C, I-34010, Sgonico, TS, Italy;(2) Departament d’Estratigrafia, P. i Geociències Marines, Universitat de Barcelona, C/ Martí i Franquès, s/n, E-08028, Barcelona, Spain |
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Abstract: | We have obtained improved images of a debris flow deposit through the reprocessing of multichannel seismic reflection data
between Drifts 6 and 7 of the continental rise of the Pacific margin of the Antarctic Peninsula. The reprocessing, primarily
aimed at the reduction of noise, relative to amplitude preservation, deconvolution, also included accurate velocity analyses.
The deposit is dated as upper Pliocene (nearly 3.0 Ma) via correlation to Sites 1095 and 1096 of the Ocean Drilling Program
(ODP) Leg 178. The estimated volume is about 1800 km3 and the inferred provenance from the continental slope implies a run out distance exceeding 250 km. The dramatic mass-wasting
event that produced this deposit, unique in the sedimentary history of this margin, is related to widespread late Pliocene
margin erosion. This was associated with a catastrophic continental margin collapse, following the Antarctic ice sheet expansion
in response to global cooling. The seismic data analysis also allowed us to identify diffractions and amplitude anomalies
interpreted as expressions of sedimentary mounds at the seafloor overlying narrow high-velocity zones that we interpret as
conduits of fluid expulsion hosting either methane hydrates or authigenic carbonates. Fluid expulsion was triggered by loading
of underlying sediments by the debris flow deposits and may have continued until today by input of fluids from sediment compaction
following the deep diagenesis of biogenic silica. |
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Keywords: | Antarctic Peninsula polar margins debris flow margin instability sediment drift late Pliocene |
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