(Table 1) Spacing of diatom abundance index and opal index at ODP Site 175-1084
An important discovery during Ocean Drilling Program Leg 175, when investigating the record of upwelling off Namibia, was the finding of a distinct Late Pliocene diatom maximum spanning the lower half of the Matuyama reversed polarity chron (MDM, Matuyama Diatom Maximum) and centered around 2.6-2.0...
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ftdatacite:10.1594/pangaea.744076 2023-05-15T13:46:40+02:00 (Table 1) Spacing of diatom abundance index and opal index at ODP Site 175-1084 Berger, Wolfgang H Lange, Carina Beatriz Pérez, M E 2010 text/tab-separated-values https://dx.doi.org/10.1594/pangaea.744076 https://doi.pangaea.de/10.1594/PANGAEA.744076 en eng PANGAEA - Data Publisher for Earth & Environmental Science https://dx.doi.org/10.1016/s0025-3227(01)00208-0 Creative Commons Attribution 3.0 Unported https://creativecommons.org/licenses/by/3.0/legalcode cc-by-3.0 CC-BY AGE Age, minimum/young Age, maximum/old Diatom abundance index Index Composite Core Abundance estimate Calculated, see references Leg175 Joides Resolution Ocean Drilling Program ODP dataset Dataset 2010 ftdatacite https://doi.org/10.1594/pangaea.744076 https://doi.org/10.1016/s0025-3227(01)00208-0 2022-02-08T16:24:46Z An important discovery during Ocean Drilling Program Leg 175, when investigating the record of upwelling off Namibia, was the finding of a distinct Late Pliocene diatom maximum spanning the lower half of the Matuyama reversed polarity chron (MDM, Matuyama Diatom Maximum) and centered around 2.6-2.0 Ma. This maximum was observed at all sites off southwestern Africa between 20°S and 30°S, and is most strongly represented in sediments of Site 1084, off Lüderitz, Namibia. The MDM is characterized by high biogenic opal content, high numbers of diatom valves, and a diatom flora rich in Southern Ocean representatives (with Thalassiothrix antarctica forming diatom mats) as well as coastal upwelling components. Before MDM time, diatoms are rare until ca. 3.6 Ma. After the MDM, in the Pleistocene, the composition of the diatom flora points to increased importance of coastal upwelling toward the present, but is accompanied by a general decrease in opal and diatom deposition. Here we present a simple conceptual model as a first step in formalizing a possible forcing mechanism responsible for the record of opal deposition in the upwelling system off Namibia. The model takes into account Southern Ocean oceanography, and a link with deepwater circulation and deepwater nutrient chemistry which, in turn, are coupled to the evolution of North Atlantic Deep Water (NADW). The model proposes that between the MDM and the Mid-Pleistocene climate revolution, opal deposition off Namibia is not directly tied to glacial-interglacial fluctuations (as seen in the global d18O record), but that, instead, a strong deepwater link exists with increased NADW production (as seen in the deepwater d13C record) accounting for higher supply of silicate to the thermocline waters that feed the upwelling process. The opal record of Site 1084 shows affinity to eccentricity on the 400-kyr scale but not for the 100-kyr scale. This points toward long-term geologic processes for delivery of silica to the ocean. Dataset Antarc* Antarctica NADW North Atlantic Deep Water North Atlantic Southern Ocean DataCite Metadata Store (German National Library of Science and Technology) Southern Ocean |
institution |
Open Polar |
collection |
DataCite Metadata Store (German National Library of Science and Technology) |
op_collection_id |
ftdatacite |
language |
English |
topic |
AGE Age, minimum/young Age, maximum/old Diatom abundance index Index Composite Core Abundance estimate Calculated, see references Leg175 Joides Resolution Ocean Drilling Program ODP |
spellingShingle |
AGE Age, minimum/young Age, maximum/old Diatom abundance index Index Composite Core Abundance estimate Calculated, see references Leg175 Joides Resolution Ocean Drilling Program ODP Berger, Wolfgang H Lange, Carina Beatriz Pérez, M E (Table 1) Spacing of diatom abundance index and opal index at ODP Site 175-1084 |
topic_facet |
AGE Age, minimum/young Age, maximum/old Diatom abundance index Index Composite Core Abundance estimate Calculated, see references Leg175 Joides Resolution Ocean Drilling Program ODP |
description |
An important discovery during Ocean Drilling Program Leg 175, when investigating the record of upwelling off Namibia, was the finding of a distinct Late Pliocene diatom maximum spanning the lower half of the Matuyama reversed polarity chron (MDM, Matuyama Diatom Maximum) and centered around 2.6-2.0 Ma. This maximum was observed at all sites off southwestern Africa between 20°S and 30°S, and is most strongly represented in sediments of Site 1084, off Lüderitz, Namibia. The MDM is characterized by high biogenic opal content, high numbers of diatom valves, and a diatom flora rich in Southern Ocean representatives (with Thalassiothrix antarctica forming diatom mats) as well as coastal upwelling components. Before MDM time, diatoms are rare until ca. 3.6 Ma. After the MDM, in the Pleistocene, the composition of the diatom flora points to increased importance of coastal upwelling toward the present, but is accompanied by a general decrease in opal and diatom deposition. Here we present a simple conceptual model as a first step in formalizing a possible forcing mechanism responsible for the record of opal deposition in the upwelling system off Namibia. The model takes into account Southern Ocean oceanography, and a link with deepwater circulation and deepwater nutrient chemistry which, in turn, are coupled to the evolution of North Atlantic Deep Water (NADW). The model proposes that between the MDM and the Mid-Pleistocene climate revolution, opal deposition off Namibia is not directly tied to glacial-interglacial fluctuations (as seen in the global d18O record), but that, instead, a strong deepwater link exists with increased NADW production (as seen in the deepwater d13C record) accounting for higher supply of silicate to the thermocline waters that feed the upwelling process. The opal record of Site 1084 shows affinity to eccentricity on the 400-kyr scale but not for the 100-kyr scale. This points toward long-term geologic processes for delivery of silica to the ocean. |
format |
Dataset |
author |
Berger, Wolfgang H Lange, Carina Beatriz Pérez, M E |
author_facet |
Berger, Wolfgang H Lange, Carina Beatriz Pérez, M E |
author_sort |
Berger, Wolfgang H |
title |
(Table 1) Spacing of diatom abundance index and opal index at ODP Site 175-1084 |
title_short |
(Table 1) Spacing of diatom abundance index and opal index at ODP Site 175-1084 |
title_full |
(Table 1) Spacing of diatom abundance index and opal index at ODP Site 175-1084 |
title_fullStr |
(Table 1) Spacing of diatom abundance index and opal index at ODP Site 175-1084 |
title_full_unstemmed |
(Table 1) Spacing of diatom abundance index and opal index at ODP Site 175-1084 |
title_sort |
(table 1) spacing of diatom abundance index and opal index at odp site 175-1084 |
publisher |
PANGAEA - Data Publisher for Earth & Environmental Science |
publishDate |
2010 |
url |
https://dx.doi.org/10.1594/pangaea.744076 https://doi.pangaea.de/10.1594/PANGAEA.744076 |
geographic |
Southern Ocean |
geographic_facet |
Southern Ocean |
genre |
Antarc* Antarctica NADW North Atlantic Deep Water North Atlantic Southern Ocean |
genre_facet |
Antarc* Antarctica NADW North Atlantic Deep Water North Atlantic Southern Ocean |
op_relation |
https://dx.doi.org/10.1016/s0025-3227(01)00208-0 |
op_rights |
Creative Commons Attribution 3.0 Unported https://creativecommons.org/licenses/by/3.0/legalcode cc-by-3.0 |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.1594/pangaea.744076 https://doi.org/10.1016/s0025-3227(01)00208-0 |
_version_ |
1766245041408311296 |