Migration history of a ¢ne-grained abyssal sediment wave on the Bahama Outer Ridge
Abyssal mud waves (or fine-grained sediment waves) are often cited as evidence for deep current activity because subbottom profiles show that the wave form has migrated with time. The migration history of a fine-grained sediment wave on the Blake-Bahama Outer Ridge (ODP Site 1062) has been studied t...
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| Format: | Text |
| Language: | English |
| Published: |
2002
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.517.3840 http://www.whoi.edu/cms/files/Flood%26Giosan_45601.pdf |
| Summary: | Abyssal mud waves (or fine-grained sediment waves) are often cited as evidence for deep current activity because subbottom profiles show that the wave form has migrated with time. The migration history of a fine-grained sediment wave on the Blake-Bahama Outer Ridge (ODP Site 1062) has been studied through the analysis of multiple ODP holes spaced across the wave. Additional information about wave migration patterns comes from 3.5-kHz records and watergun seismic profiles. These data suggest that wave migration has varied during the lastV10 Myr, although the only sediments sampled are younger than 4.8 Ma. Seismic profiles suggest wave migration was initiated about 8^10 Ma, and wave migration was pronounced from about 5 Ma to about 1 Ma (with an episode of wave reorganization about 4.5 Ma). Analysis of ODP cores suggests that migration rates have been somewhat lower and more variable during the last 1 Myr. Intervals of no wave migration are observed for several time intervals and appear to characterize deglaciations, especially during the last 500 kyr. Comparisons between seismic profiles and the core record show that most of the seismic horizons correlate closely with time horizons, and thus that the seismic profiles give a reasonable representation of sediment wave migration. Models suggest that wave migration is more pronounced during periods of higher bottom current flow and less pronounced during periods of lower current flow. Thus the migration record is consistent with generally higher bottom flow speeds at this site prior to 1 Ma and lower |
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