CaltechAUTHORS
  A Caltech Library Service

A 35 Myr record of helium in pelagic limestones from Italy: Implications for interplanetary dust accretion from the early Maastrichtian to the middle Eocene

Mukhopadhyay, S. and Farley, K. A. and Montanari, A. (2001) A 35 Myr record of helium in pelagic limestones from Italy: Implications for interplanetary dust accretion from the early Maastrichtian to the middle Eocene. Geochimica et Cosmochimica Acta, 65 (4). pp. 653-669. ISSN 0016-7037. https://resolver.caltech.edu/CaltechAUTHORS:20121120-102333961

Full text is not posted in this repository. Consult Related URLs below.

Use this Persistent URL to link to this item: https://resolver.caltech.edu/CaltechAUTHORS:20121120-102333961

Abstract

We have determined the helium concentration and isotopic composition of a suite of early Maastrichtian through middle Eocene pelagic limestones in the Italian Apennines. The results provide a 35 Myr record of the implied flux of extraterrestrial ^3He, which is a proxy for the accretion rate of interplanetary dust particles (IDPs). Our measurements show that the ^3He flux was fairly constant in the Maastrichtian, except for possible minor increases (factor of two or less) from ∼70.5 Ma to 68 Ma and at ∼66 Ma, which probably reflect transient increases in the accretion rate of asteroidal and/or cometary IDPs. We find no evidence for an increase in IDP accretion at or immediately before the K/T boundary, implying that the K/T impact was not associated with enhanced solar system dustiness. This observation precludes the possibility that the K/T impactor was a member of a major comet shower, and is more consistent with impact of a lone comet or asteroid. Our data suggest a 2 to 4 fold increase in IDP accretion between 57 and 54 Ma, followed by a factor of three decrease over an ∼4 Myr period in the early to middle Eocene. The duration and magnitude of this variability is inconsistent with previous observations attributed to a shower of long period comets, and is more likely the result of collisions in the asteroid belt/and or Kuiper belt. In the entire 35 Myr record we find no evidence for major enhancements of the IDP accretion rate of the type expected from comet showers. Our results, in combination with earlier ^3He measurements, do not support models that predict recurrent comet showers with periods of <38 Myrs. If there is a periodicity in the cratering record that is caused by periodic modulation of the Oort cloud, it is not evident in the Apennine sediment data. Along with the ^3He measurements we also obtained ^4He concentrations, which record temporal changes in the flux or composition of terrigenous matter. The most significant change in ^4He occurs in the last 4 Myrs of the Cretaceous, over which the concentration of ^4He in the detrital component rises by 300%. This rise tracks a strong increase in the seawater ^(87)Sr/^(86)Sr ratio, suggesting a globally significant change in the composition of continental detritus delivered to the oceans, possibly arising from increased continental weathering.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/S0016-7037(00)00555-XDOIUNSPECIFIED
http://www.sciencedirect.com/science/article/pii/S001670370000555XPublisherUNSPECIFIED
ORCID:
AuthorORCID
Farley, K. A.0000-0002-7846-7546
Additional Information:© 2001 Elsevier Science Ltd. Received May 30, 2000; accepted in revised form September 13, 2000. Associate editor: C. Koeberl. We thank Kim Robinson, Elizabeth Navarro, and Selene Eltgroth for sample preparation and P. Clayes, B. Peucker-Ehrenbrink, and B. Schmitz for thorough and helpful reviews. This was work was supported by NASA.
Funders:
Funding AgencyGrant Number
NASAUNSPECIFIED
Issue or Number:4
Record Number:CaltechAUTHORS:20121120-102333961
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20121120-102333961
Official Citation:S Mukhopadhyay, K.A Farley, A Montanari, A 35 Myr record of helium in pelagic limestones from Italy: implications for interplanetary dust accretion from the early Maastrichtian to the middle Eocene, Geochimica et Cosmochimica Acta, Volume 65, Issue 4, 15 February 2001, Pages 653-669, ISSN 0016-7037, 10.1016/S0016-7037(00)00555-X. (http://www.sciencedirect.com/science/article/pii/S001670370000555X)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35561
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:20 Nov 2012 18:36
Last Modified:03 Mar 2020 13:01

Repository Staff Only: item control page