The early Matuyama Diatom Maximum off SW Africa, Benguela Current System (ODP Leg 175)

Citation
Cb. Lange et al., The early Matuyama Diatom Maximum off SW Africa, Benguela Current System (ODP Leg 175), MARINE GEOL, 161(2-4), 1999, pp. 93-114
Citations number
39
Categorie Soggetti
Earth Sciences
Journal title
MARINE GEOLOGY
ISSN journal
00253227 → ACNP
Volume
161
Issue
2-4
Year of publication
1999
Pages
93 - 114
Database
ISI
SICI code
0025-3227(199910)161:2-4<93:TEMDMO>2.0.ZU;2-3
Abstract
Several sites Of Ocean Drilling Program Leg 175 between 20 degrees and 30 d egrees S (1081, 1082, 1083, 1084 and 1085) in the Benguela Current system s how a distinct opal (and diatom) maximum within the late Pliocene and early Quaternary, spanning the lower half of the Matuyama reversed polarity Chro n (MDM, Matuyama Diatom Maximum). This maximum is centered around 2.0-2.6 M a, and follows a rapid increase of diatom deposition near 3.1 Ma. Within th e MDM, we recognized intervals dominated by the antarctic/subantarctic spec ies Thalassiothrix antarctica which have the aspect of diatom mats, The MDM (and the mats) developed during a time of sustained Southern Ocean influen ce (3.2-1.6 Ma), probably reflecting a period of seasonally-pulsed continuo us advection of subantarctic waters into the Benguela Oceanic Current, The onset and cessation of the MDM raises questions about modes in the operatio n of the silica cycle and the relation of these to major oceanographic even ts. A depositional model for the late Pliocene is proposed which involves p ositional changes in a longshore system of fronts, substantial equatorward excursions of subantarctic waters during MDM time, and subsurface waters gr eatly enriched in silicate. (C) 1999 Elsevier Science B.V. All rights reser ved.