A Caltech Library Service

Extraterrestrial Helium in Seafloor Sediments: Identification, Characteristics, and Accretion Rate Over Geologic Time

Farley, Kenneth A. (2001) Extraterrestrial Helium in Seafloor Sediments: Identification, Characteristics, and Accretion Rate Over Geologic Time. In: Accretion of Extraterrestrial Matter Throughout Earth’s History. Kluwer Academic/Plenum Publishers , New York, pp. 179-204. ISBN 9780306466892.

Full text is not posted in this repository.

Use this Persistent URL to link to this item:


Almost 40 years after the discovery of extraterrestrial helium in seafloor sediments, renewed attention is being focused on using helium as a proxy for the sedimentary abundance of extraterrestrial debris. Extraterrestrial He is carried to the seafloor by the finest fraction of interplanetary dust and is retained in at least some sediments for hundreds of millions of years. Helium isotope systematics uniquely identity the extraterrestrial component, which is apparently hosted within magnetite and silicate grains. In some sediments ^3He is completely derived from this source, in others the extraterrestrial fraction can be computed from the measured ^3He/^4He ratio. Variations in the sedimentary concentration of extraterrestrial ^3He must reflect both changes in sedimentation rate and fluctuations in the accretion rate of ^3He from space. When changes in sedimentation rate can be controlled for, variations in extraterrestrial ^3He can be related to changes in the accretion rate of IDPs arising from major solar system events including asteroid collisions and enhanced cometary activity. A ^3He record in sediments spanning the last 70 Myr provides insights to such events, including the first compelling evidence for the occurrence of a shower of long-period comets, 35 Ma.

Item Type:Book Section
Farley, Kenneth A.0000-0002-7846-7546
Additional Information:© 2001 Kluwer Academic/Plenum Publishers. I thank Sujoy Mukhopadhyay for thoughtful discussions, and for sample analyses and data preparation for the Gubbio section. Careful reviews by Franco Marcantonio and Steve Kortenkamp improved the manuscript. D. Lal provided the Chinese loess samples. This work was supported by NASA and a fellowship from the David and Lucille Packard Foundation.
Funding AgencyGrant Number
David and Lucille Packard FoundationUNSPECIFIED
Record Number:CaltechAUTHORS:20121115-103034876
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35485
Deposited By: Tony Diaz
Deposited On:20 Nov 2012 17:55
Last Modified:03 Mar 2020 13:01

Repository Staff Only: item control page