Accumulation rates of sediments and main sedimentary components in ODP Leg 121 holes on Broken Ridge
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| Natura: | Dataset Open Access |
| Lingua: | en |
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PANGAEA
1990
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| _version_ | 1867169499145306112 |
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| author | Rea, David K Dehn, Jonathan Driscoll, Neal W Farrell, John W Janecek, Thomas R Owen, Robert M Pospichal, James J Resiwati, Purtyasti |
| author_facet | Rea, David K Dehn, Jonathan Driscoll, Neal W Farrell, John W Janecek, Thomas R Owen, Robert M Pospichal, James J Resiwati, Purtyasti |
| collection | Datos científicos de ciencias marinas y ambientales |
| contents | Broken Ridge, in the eastern Indian Ocean,is overlain by about 1600 m of middle Cretaceous to Pleistocene tuffaceous and carbonate sediments that record the oceanographic history of southern hemisphere mid-to high-latitude regions. Prior to about 42 Ma, Broken Ridge formed the northern part of the broad Kerguelen-Broken Ridge Plateau. During the middle Eocene, this feature was split by the newly forming Southeast Indian Ocean Ridge; since then, Broken Ridge has drifted north from about 55° to 31°S. The lower part of the sedimentary section is characterized by Turonian to Santonian tuffs that contain abundant glauconite and some carbonate. The tuffs record a large but apparently local volcanic input that characterized the central part of Broken Ridge into the early Tertiary. Maestrichtian shallow-water(several hundred to 1000 m depth) limestones and cherts accumulated at some of the highest rates ever documented from the open ocean, 4 to 5 g/cm**2/kyr. A complete (with all biostratigraphic zones) Cretaceous-Tertiary boundary section was recovered from site 752. The first 1.5 m.y. of the Tertiary is characterized by an order-of-magnitude reduction in the flux of biogenic sediments, indicating a period of sharply reduced biological productivity at 55°S, following which the carbonate and silica sedimentation rates almost reach the previous high values of the latest Cretaceous. We recovered a complete section through the Paleocene that contains all major fossil groups and is more than 300 m thick, perhaps the best pelagic Paleocene section encountered in ocean drilling. About 42 Ma, Broken Ridge was uplifted 2500 m in response to the intra-plateau rifting event; subsequent erosion and deposition has resulted in a prominent Eocene angular unconformity atop the ridge. An Oligocene disconformity characterized by a widespread pebble layer probably represents the 30 Ma sea-level fall. The Neogene pelagic ooze on Broken Ridge has been winnowed, and thus its grain size provides a direct physical record of the energy of the southern hemisphere drift current in the Indian Ocean for the past 30 m.y. |
| format | Dataset Open Access |
| id | pangaea_https___doi_org_10_1594_PANGAEA_720962 |
| institution | PANGAEA |
| language | en |
| publishDate | 1990 |
| publisher | PANGAEA |
| record_format | pangaea |
| spellingShingle | Accumulation rates of sediments and main sedimentary components in ODP Leg 121 holes on Broken Ridge Rea, David K Dehn, Jonathan Driscoll, Neal W Farrell, John W Janecek, Thomas R Owen, Robert M Pospichal, James J Resiwati, Purtyasti 121-752A; 121-752B; 121-753A; 121-754A; 121-754B; 121-755A; DRILL; Drilling/drill rig; Joides Resolution; Leg121; Ocean Drilling Program; ODP; South Indian Ridge, South Indian Ocean Broken Ridge, in the eastern Indian Ocean,is overlain by about 1600 m of middle Cretaceous to Pleistocene tuffaceous and carbonate sediments that record the oceanographic history of southern hemisphere mid-to high-latitude regions. Prior to about 42 Ma, Broken Ridge formed the northern part of the broad Kerguelen-Broken Ridge Plateau. During the middle Eocene, this feature was split by the newly forming Southeast Indian Ocean Ridge; since then, Broken Ridge has drifted north from about 55° to 31°S. The lower part of the sedimentary section is characterized by Turonian to Santonian tuffs that contain abundant glauconite and some carbonate. The tuffs record a large but apparently local volcanic input that characterized the central part of Broken Ridge into the early Tertiary. Maestrichtian shallow-water(several hundred to 1000 m depth) limestones and cherts accumulated at some of the highest rates ever documented from the open ocean, 4 to 5 g/cm**2/kyr. A complete (with all biostratigraphic zones) Cretaceous-Tertiary boundary section was recovered from site 752. The first 1.5 m.y. of the Tertiary is characterized by an order-of-magnitude reduction in the flux of biogenic sediments, indicating a period of sharply reduced biological productivity at 55°S, following which the carbonate and silica sedimentation rates almost reach the previous high values of the latest Cretaceous. We recovered a complete section through the Paleocene that contains all major fossil groups and is more than 300 m thick, perhaps the best pelagic Paleocene section encountered in ocean drilling. About 42 Ma, Broken Ridge was uplifted 2500 m in response to the intra-plateau rifting event; subsequent erosion and deposition has resulted in a prominent Eocene angular unconformity atop the ridge. An Oligocene disconformity characterized by a widespread pebble layer probably represents the 30 Ma sea-level fall. The Neogene pelagic ooze on Broken Ridge has been winnowed, and thus its grain size provides a direct physical record of the energy of the southern hemisphere drift current in the Indian Ocean for the past 30 m.y. |
| title | Accumulation rates of sediments and main sedimentary components in ODP Leg 121 holes on Broken Ridge |
| topic | 121-752A; 121-752B; 121-753A; 121-754A; 121-754B; 121-755A; DRILL; Drilling/drill rig; Joides Resolution; Leg121; Ocean Drilling Program; ODP; South Indian Ridge, South Indian Ocean |
| url | https://doi.org/10.1594/PANGAEA.720962 |