Composition of bentonite-, smectite-rich- and ash beds from DSDP Leg 19 holes
Late Cenozoic ash deposits cored in Deep Sea Drilling Project Leg 19 in the far northwest Pacific and in the Bering Sea have altered to bentonite beds. Some bentonite layers were subsequently replaced by carbonate beds. A significant part of the Neogene volcanic history of land areas adjacent to the...
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PANGAEA - Data Publisher for Earth & Environmental Science
1978
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ftdatacite:10.1594/pangaea.718128 2023-05-15T15:43:45+02:00 Composition of bentonite-, smectite-rich- and ash beds from DSDP Leg 19 holes Hein, James R Scholl, David W 1978 application/zip https://dx.doi.org/10.1594/pangaea.718128 https://doi.pangaea.de/10.1594/PANGAEA.718128 en eng PANGAEA - Data Publisher for Earth & Environmental Science https://dx.doi.org/10.1130/0016-7606(1978)89<197:dadolc>2.0.co;2 Creative Commons Attribution 3.0 Unported https://creativecommons.org/licenses/by/3.0/legalcode cc-by-3.0 CC-BY Drilling/drill rig Leg19 Glomar Challenger Deep Sea Drilling Project DSDP Collection article Collection of Datasets 1978 ftdatacite https://doi.org/10.1594/pangaea.718128 https://doi.org/10.1130/0016-7606(1978)89<197:dadolc>2.0.co;2 2021-11-05T12:55:41Z Late Cenozoic ash deposits cored in Deep Sea Drilling Project Leg 19 in the far northwest Pacific and in the Bering Sea have altered to bentonite beds. Some bentonite layers were subsequently replaced by carbonate beds. A significant part of the Neogene volcanic history of land areas adjacent to the far north Pacific is represented by these diagenetic deposits. Bentonite beds are composed of authigenic smectite and minor amounts of clinoptilolite. Authigenic smectite has fewer illite layers than detrital smectite. Opal-A and opal-CT, abundant in Bering Sea sediment, are not found in ash or bentonite layers. The percentage of smectite in the total clay-mineral assemblage of ash beds is greater than that for adjacent terrigenous sediment, but the total amount of clay minerals in ash sequences is less than in surrounding deposits. Morphology of the 17-Å peak of smectite found in ash may represent newly formed, poorly crystalline smectite. Smectite becomes better crystallized as bentonite layers form. The percentage of smectite of the total clay-mineral assemblage in bentonite beds is greater than that in surrounding sediment, and, in contrast to ash beds, the total amount of clay minerals (mostly smectite) in bentonite layers is greater than in adjacent terrigenous sediment. Apparently, silica is not mobilized when volcanic ash layers transform to bentonite beds. Saponite-nontronite varieties of smectite and high Fe/Al and Ti/Al ratios distinguish bentonite beds derived from basaltic parent material from those beds formed from more silicic volcanic ash. These silicic ash beds produce bentonite composed mostly of montmorillonite. The basal sediment section at site 192 is rich with bentonite beds. Smectite in the upper part of this section (Eocene) was formed by low-temperature diagenesis of volcanic debris of intermediate or more silicic composition derived from arc or Pacific volcanoes. In contrast, smectite from the lowest 10 to 20 m of the sedimentary section (Cretaceous) is formed from either low-temperature or hydrothermal alteration of the underlying basaltic basement and associated pyroclastic debris. This near-basement smectite contains Mg and K acquired from sea water and Si, Al, Fe, Ti, and Mn released from the volcanic material. Article in Journal/Newspaper Bering Sea DataCite Metadata Store (German National Library of Science and Technology) Bering Sea Pacific |
institution |
Open Polar |
collection |
DataCite Metadata Store (German National Library of Science and Technology) |
op_collection_id |
ftdatacite |
language |
English |
topic |
Drilling/drill rig Leg19 Glomar Challenger Deep Sea Drilling Project DSDP |
spellingShingle |
Drilling/drill rig Leg19 Glomar Challenger Deep Sea Drilling Project DSDP Hein, James R Scholl, David W Composition of bentonite-, smectite-rich- and ash beds from DSDP Leg 19 holes |
topic_facet |
Drilling/drill rig Leg19 Glomar Challenger Deep Sea Drilling Project DSDP |
description |
Late Cenozoic ash deposits cored in Deep Sea Drilling Project Leg 19 in the far northwest Pacific and in the Bering Sea have altered to bentonite beds. Some bentonite layers were subsequently replaced by carbonate beds. A significant part of the Neogene volcanic history of land areas adjacent to the far north Pacific is represented by these diagenetic deposits. Bentonite beds are composed of authigenic smectite and minor amounts of clinoptilolite. Authigenic smectite has fewer illite layers than detrital smectite. Opal-A and opal-CT, abundant in Bering Sea sediment, are not found in ash or bentonite layers. The percentage of smectite in the total clay-mineral assemblage of ash beds is greater than that for adjacent terrigenous sediment, but the total amount of clay minerals in ash sequences is less than in surrounding deposits. Morphology of the 17-Å peak of smectite found in ash may represent newly formed, poorly crystalline smectite. Smectite becomes better crystallized as bentonite layers form. The percentage of smectite of the total clay-mineral assemblage in bentonite beds is greater than that in surrounding sediment, and, in contrast to ash beds, the total amount of clay minerals (mostly smectite) in bentonite layers is greater than in adjacent terrigenous sediment. Apparently, silica is not mobilized when volcanic ash layers transform to bentonite beds. Saponite-nontronite varieties of smectite and high Fe/Al and Ti/Al ratios distinguish bentonite beds derived from basaltic parent material from those beds formed from more silicic volcanic ash. These silicic ash beds produce bentonite composed mostly of montmorillonite. The basal sediment section at site 192 is rich with bentonite beds. Smectite in the upper part of this section (Eocene) was formed by low-temperature diagenesis of volcanic debris of intermediate or more silicic composition derived from arc or Pacific volcanoes. In contrast, smectite from the lowest 10 to 20 m of the sedimentary section (Cretaceous) is formed from either low-temperature or hydrothermal alteration of the underlying basaltic basement and associated pyroclastic debris. This near-basement smectite contains Mg and K acquired from sea water and Si, Al, Fe, Ti, and Mn released from the volcanic material. |
format |
Article in Journal/Newspaper |
author |
Hein, James R Scholl, David W |
author_facet |
Hein, James R Scholl, David W |
author_sort |
Hein, James R |
title |
Composition of bentonite-, smectite-rich- and ash beds from DSDP Leg 19 holes |
title_short |
Composition of bentonite-, smectite-rich- and ash beds from DSDP Leg 19 holes |
title_full |
Composition of bentonite-, smectite-rich- and ash beds from DSDP Leg 19 holes |
title_fullStr |
Composition of bentonite-, smectite-rich- and ash beds from DSDP Leg 19 holes |
title_full_unstemmed |
Composition of bentonite-, smectite-rich- and ash beds from DSDP Leg 19 holes |
title_sort |
composition of bentonite-, smectite-rich- and ash beds from dsdp leg 19 holes |
publisher |
PANGAEA - Data Publisher for Earth & Environmental Science |
publishDate |
1978 |
url |
https://dx.doi.org/10.1594/pangaea.718128 https://doi.pangaea.de/10.1594/PANGAEA.718128 |
geographic |
Bering Sea Pacific |
geographic_facet |
Bering Sea Pacific |
genre |
Bering Sea |
genre_facet |
Bering Sea |
op_relation |
https://dx.doi.org/10.1130/0016-7606(1978)89<197:dadolc>2.0.co;2 |
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.718128 https://doi.org/10.1130/0016-7606(1978)89<197:dadolc>2.0.co;2 |
_version_ |
1766377955815063552 |