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Late Eocene and late Miocene cosmic dust events: Comet showers, asteroid collisions, or lunar impacts?

Farley, K. A. (2009) Late Eocene and late Miocene cosmic dust events: Comet showers, asteroid collisions, or lunar impacts? In: The late Eocene Earth: hothouse, icehouse, and impacts. Special papers (Geological Society of America). No.452. Geological Society of America , Boulder, CO, pp. 27-35. ISBN 978-0-8137-2452-2.

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Two long-lived peaks in extraterrestrial ^3He flux have been identified in the sedimentary record of the Cenozoic Era: at 8.2 Ma (late Miocene) and 35.8 Ma (late Eocene). These peaks document the occurrence of important events in the recent history of the solar system. The timing and temporal evolution of the dust event in the late Miocene as well as the absence of major terrestrial impact craters are consistent with an origin in the catastrophic collision that produced the Veritas asteroid family at this time. In contrast, there is no known asteroid collision corresponding to the late Eocene peak. Instead, the late Eocene event has elements consistent with a comet shower produced by a close stellar encounter. Both the rise time and the fall time of the enhanced dust flux and the occurrence of two major terrestrial impacts at the peak of the event are predicted by considerations of comet shower dynamics. However, debris from one of these impacts has a Cr isotope ratio that appears to exclude a carbonaceous chondrite impactor. If the presumption that comets have a carbonaceous chondrite–like composition is accurate, then an alternative mechanism for the late Eocene event may be required. The recent suggestion of an asteroid shower, where the ^3He-bearing dust resulted from lunar impacts, is one such possibility, but it too fails to account fully for existing observations. The cause of the late Eocene event thus remains uncertain.

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Farley, K. A.0000-0002-7846-7546
Additional Information:© 2009 Geological Society of America. Accepted 16 September 2008. I would like to thank the conveners of the 2007 Penrose Conference at which this work was presented: Alessandro Montanari, Christian Koeberl, Fritz Hilgen, and Rodolfo Coccioni. I appreciate the helpful reviews of this manuscript by B. Schmitz and I. McDonald.
Series Name:Special papers (Geological Society of America)
Issue or Number:452
Record Number:CaltechAUTHORS:20150202-124202237
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Official Citation:Farley, K.A., 2009, Late Eocene and late Miocene cosmic dust events: Comet showers, asteroid collisions, or lunar impacts?, in Koeberl, C., and Montanari, A., eds., The Late Eocene Earth- Hothouse, lcehouse, and Impacts: Geological Society of America Special Paper 452, p. 27-35, doi: 10.1130/2009.2452(03)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:54301
Deposited By: Tony Diaz
Deposited On:04 Feb 2015 04:13
Last Modified:03 Mar 2020 13:01

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