Benthic foraminifera abundance in ODP Leg 155 holes
Citation
Maslin M A, Vilela N, Mikkelsen N, Grootes P M (2005). Benthic foraminifera abundance in ODP Leg 155 holes. PANGAEA - Publishing Network for Geoscientific and Environmental Data. Occurrence dataset https://doi.org/10.1594/pangaea.742948 accessed via GBIF.org on 2020-02-18.Description
The general Pleistocene architecture of the Amazon Fan has been reconstructed using sediment recovered by Ocean Drilling Program Leg 155. Huge regional mass-transport deposits (MTDs) make up a significant component of the Amazon Fan. These deposits each cover an area over 15,000 km**2 (approximately the size of Jamaica), reach a maximum thickness of 200 m, and consist of ~5000 Gt of sediment. Benthic foraminiferal fauna analysis and sedimentology indicate that the MTDs originated on the continental slope, which is at least 200 km laterally and 1500 m above their present position. Each mass-failure event was formed by the catastrophic failure of the continental slope and has been dated and correlated with climate-induced changes in sea level. Studies of the benthic foraminiferal assemblages in the Amazon Fan has been essential to our reconstruction of the origin and cause of these failures. The MTDs contain rare shelf (Quinqueloculina cf. stalkeri, Brizalina aenariensis, Q. lamarckiana, and Pseudononion atlanticum) and dominant upper-middle bathyal species (cassidulinids and buliminids). We conclude that the MTD originated between 200 and 600 m water depth, approximately the same zone in which gas hydrates occur. We suggest that the glacial MTDs referred to as Deep Eastern MTD (35–37 ka) and Unit R MTD (41–45 ka) correlate with rapid drops in sea level which destabilized continental slope gas-hydrate reservoirs causing catastrophic slope failure. An alternative explanation is required for the deglacial MTDs referred to as Western and Eastern Debris Flows (13–14 ka) which occurred as sea level rose rapidly during the Bølling-Allerød period. We suggest that the deglaciation of the Andes and the consequent enhanced sediment supply coupled with a shift of the depo-centre to the continental shelf, caused over-burdening and thus slope failure. Evidence for a 2 per mil negative d13C shift in both planktonic foraminifera and organic matter coeval with these failures suggest that whatever the cause, there was a large release of methane hydrate associated with each failure.Taxonomic Coverages
Geographic Coverages
Bibliographic Citations
Contacts
Mark A Maslinoriginator
Naja Vilela
originator
Naja Mikkelsen
originator
Pieter Meiert Grootes
originator
metadata author
PANGAEA - Data Publisher for Earth & Environmental Science
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administrative point of contact
PANGAEA - Data Publisher for Earth & Environmental Science
email: info@pangaea.de
homepage: http://www.pangaea.de