17. HIGH RESOLUTION RECORDS OF BENTHIC FORAMINIFERS IN THE LATE NEOGENE OF THE NORTHEASTERN ATLANTIC1
Sediment composition and color, as well as faunal content of hydraulic piston cores of late Pliocene and Quaternary age from Deep Sea Drilling Project (DSDP) Hole 552A (Northeast Atlantic), show large and fairly regular variations. Based on paleontologically and paleomagnetically determined sediment...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.512.8407 http://www.deepseadrilling.org/81/volume/dsdp81_17.pdf |
| Summary: | Sediment composition and color, as well as faunal content of hydraulic piston cores of late Pliocene and Quaternary age from Deep Sea Drilling Project (DSDP) Hole 552A (Northeast Atlantic), show large and fairly regular variations. Based on paleontologically and paleomagnetically determined sedimentation rates, these variations occurred at about 100,000-yr. intervals during the past 700,000 yr, and at approximately 40,000-yr. intervals between 700,000 yr. and 2.5 m.y. ago, the date of the first appearance of "glacial " (ice-rafted) sediments. These changes affected both surface and bottom waters of the area, as indicated by planktonic and benthic foraminifers. However, sediments older than 2.5 m.y. do not exhibit any obvious fluctuations in composition, nor does the fauna of planktonic foraminifers, which indicates that surface climate and oceanographic conditions were stable. On the other hand, the deep-water environment, as evidenced by the composition of benthic foraminiferal faunas, did not experience the sharp break at 2.5 m.y. Faunal fluctuations of about 20,000-yr. periodicity extend continuously into the early Plio-cene and late Miocene. Formation of North Atlantic Deep Water occurs primarily in the Norwegian-Greenland Sea and its properties and rate of formation there are modulated during "glacial " time by surface climate, determined by eccentricity and obli-quity orbital parameters. In "preglacial " times the midlatitude effect of the precession orbital parameter assumes greater significance. |
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