Micrometeorites are strongly magnetic and continuously accumulate at the Earth's surface. On the basis of previously acquired magnetic data, we investigated at which conditions micrometeorites can bias the sedimentary palaeomagnetic and rock magnetic record. We calculated the probabilities for a sediment sample (discrete samples or U-channel samples) to have its detrital remanent magnetization deviated by the presence of a micrometeorite. Our model shows that direction anomalies >5° caused by micrometeorites may be rather frequent (more than 1% of measured samples), even for sediments with typical values of sedimentation rate (up to 10 cm/kyr) and remanent magnetization (up to 5 × 10-3 A/m). Excursions >30° caused by micrometeorites have probabilities >1% in sediments with remanent magnetization <10-3 A/m and sedimentation rate <10 cm/ka. Reversals caused by micrometeorites have probabilities >1% for sediments with remanent magnetization <2 × 10-4 A/m and sedimentation rate <1 cm/ka. On the other hand, only sediments with magnetic susceptibilities <10-5 SI and sedimentation rates <1 cm/ka can be significantly affected by the presence of micrometeorites.
Micrometeorites: A possible bias on the sedimentary magnetic record
FOLCO, LUIGI
2008-01-01
Abstract
Micrometeorites are strongly magnetic and continuously accumulate at the Earth's surface. On the basis of previously acquired magnetic data, we investigated at which conditions micrometeorites can bias the sedimentary palaeomagnetic and rock magnetic record. We calculated the probabilities for a sediment sample (discrete samples or U-channel samples) to have its detrital remanent magnetization deviated by the presence of a micrometeorite. Our model shows that direction anomalies >5° caused by micrometeorites may be rather frequent (more than 1% of measured samples), even for sediments with typical values of sedimentation rate (up to 10 cm/kyr) and remanent magnetization (up to 5 × 10-3 A/m). Excursions >30° caused by micrometeorites have probabilities >1% in sediments with remanent magnetization <10-3 A/m and sedimentation rate <10 cm/ka. Reversals caused by micrometeorites have probabilities >1% for sediments with remanent magnetization <2 × 10-4 A/m and sedimentation rate <1 cm/ka. On the other hand, only sediments with magnetic susceptibilities <10-5 SI and sedimentation rates <1 cm/ka can be significantly affected by the presence of micrometeorites.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
