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Northwest African Continental Margin: history of sediment accumulation, landslide deposits, and hiatuses as revealed by drilling the Madeira Abyssal Plain

Northwest African Continental Margin: history of sediment accumulation, landslide deposits, and hiatuses as revealed by drilling the Madeira Abyssal Plain
Northwest African Continental Margin: history of sediment accumulation, landslide deposits, and hiatuses as revealed by drilling the Madeira Abyssal Plain
ODP drill sites in the Madeira Abyssal Plain reveal sequences of organic-rich turbidites derived from the northwest African margin, in which each turbidite has a volume of tens to hundreds of cubic kilometers. The frequency of turbidite emplacement has been combined with core and seismic data to show the volume of redeposited sediment. The basin began to fill about 22 Ma with numerous small turbidites, up to 100 per million years, each with volumes of a few cubic kilometers. The total volume of turbidites deposited increased between 16 and 11 Ma, as did their individual volumes, and then declined to 7 Ma. At 7 Ma, there was a dramatic increase in the amount of turbidite input to 768 km3/Myr and a rise in the average volume of each unit to 59 km3. These high values have been maintained to the present day. The variations in the amount of redeposited sediment most likely reflect the rates of sedimentation on the northwest African margin since high sedimentation leads to oversteepening of the slopes and eventual mass wasting. The dramatic changes at about 7 Ma may be due to a large increase in upwelling off northwest Africa caused by circulation changes associated with increased glaciation of the poles. Up to 20% of sediment may be remobilized by landslides, with each event leaving a hiatus. Each of these hiatuses extends over an average area of ?4800 km2 and represents removal of sediment layers several tens of meters thick and of several hundred thousand years duration.
atlneazo, madeira abyssal plain, turbitites, northwest africa, submarine landslides, odp site 950, odp site 951, odp site 952, odp leg 157, cores, geology, hiatus, continental margin, landslide, turbidite
0883-8305
1009-[13pp]
Weaver, P.P.E.
1ab10035-6132-46aa-8a5c-6fb23a1b8ab4
Weaver, P.P.E.
1ab10035-6132-46aa-8a5c-6fb23a1b8ab4

Weaver, P.P.E. (2003) Northwest African Continental Margin: history of sediment accumulation, landslide deposits, and hiatuses as revealed by drilling the Madeira Abyssal Plain. Paleoceanography, 18 (1), 1009-[13pp]. (doi:10.1029/2002PA000758).

Record type: Article

Abstract

ODP drill sites in the Madeira Abyssal Plain reveal sequences of organic-rich turbidites derived from the northwest African margin, in which each turbidite has a volume of tens to hundreds of cubic kilometers. The frequency of turbidite emplacement has been combined with core and seismic data to show the volume of redeposited sediment. The basin began to fill about 22 Ma with numerous small turbidites, up to 100 per million years, each with volumes of a few cubic kilometers. The total volume of turbidites deposited increased between 16 and 11 Ma, as did their individual volumes, and then declined to 7 Ma. At 7 Ma, there was a dramatic increase in the amount of turbidite input to 768 km3/Myr and a rise in the average volume of each unit to 59 km3. These high values have been maintained to the present day. The variations in the amount of redeposited sediment most likely reflect the rates of sedimentation on the northwest African margin since high sedimentation leads to oversteepening of the slopes and eventual mass wasting. The dramatic changes at about 7 Ma may be due to a large increase in upwelling off northwest Africa caused by circulation changes associated with increased glaciation of the poles. Up to 20% of sediment may be remobilized by landslides, with each event leaving a hiatus. Each of these hiatuses extends over an average area of ?4800 km2 and represents removal of sediment layers several tens of meters thick and of several hundred thousand years duration.

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More information

Published date: February 2003
Keywords: atlneazo, madeira abyssal plain, turbitites, northwest africa, submarine landslides, odp site 950, odp site 951, odp site 952, odp leg 157, cores, geology, hiatus, continental margin, landslide, turbidite

Identifiers

Local EPrints ID: 2133
URI: http://eprints.soton.ac.uk/id/eprint/2133
ISSN: 0883-8305
PURE UUID: fa714271-99e1-4d69-bfca-20c36c015768

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Date deposited: 12 May 2004
Last modified: 15 Mar 2024 04:44

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Author: P.P.E. Weaver

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