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A record of the extraterrestrial ^3He flux through the Late Cretaceous

Farley, K. A. and Montanari, A. and Coccioni, R. (2012) A record of the extraterrestrial ^3He flux through the Late Cretaceous. Geochimica et Cosmochimica Acta, 84 . pp. 314-328. ISSN 0016-7037.

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Late Cretaceous (100–73 Ma) pelagic limestones were measured for helium concentration and isotopic composition to characterize the interplanetary dust flux using ^(3)He as a tracer. In the Bottaccione section near Gubbio, Italy, three intervals of elevated 3He concentration were detected: K1 in the Campanian stage at ∼79 Ma, K2 in the Santonian stage at ∼85 Ma, and K3 in the Turonian stage at ∼91 Ma. All three of these episodes are associated with high ^(3)He/^(4)He and ^(3)He/non-carbonate ratios, consistent with their derivation from an enhanced extraterrestrial ^(3)He flux rather than decreased carbonate sedimentation or dissolution. While K2 is modest in magnitude and duration and thus is of limited significance, K1 and K3 are each identified by a few myr interval with an ∼4-fold enhancement in mean 3He flux compared with pre-event levels. Samples from ODP Hole 762C in the Indian Ocean spanning both K2 and K3 (93–83 Ma) confirm the presence of a peak in the Turonian stage, suggesting that K3 is a global event. The K1 and K3 3He events are similar in most respects to the two peaks previously detected in the Cenozoic, suggesting a similar origin. These have been attributed to a major asteroid collision in the Late Miocene and to a shower of either comets or asteroids in the Late Eocene. Based on the age and temporal evolution of K1, we suggest that it most likely records the collision which produced the Baptistina asteroid family independently dated at ∼80 Ma. The K3 event is less easily explained. It is characterized by an unusually spiky and erratic temporal progression, suggesting an unusual abundance of very ^(3)He rich particles not previously seen in the sedimentary ^(3)He record. We suggest this episode arises either from a comet shower or from an asteroid shower possibly associated with dust-producing lunar impacts.

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Farley, K. A.0000-0002-7846-7546
Additional Information:© 2012 Elsevier Ltd. Received 7 October 2011. Accepted 18 January 2012. Available online 3 February 2012. This work was partially supported by the U.S. National Science Foundation (OCE-1060877). We thank Scott Farley and Daniel Blado for their contributions to the analytical work and Christian Koeberl for thoughtful early discussions. The manuscript benefitted from reviews by P. Claeys and J. Fritz.
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Official Citation:K.A. Farley, A. Montanari, R. Coccioni, A record of the extraterrestrial 3He flux through the Late Cretaceous, Geochimica et Cosmochimica Acta, Volume 84, 1 May 2012, Pages 314-328, ISSN 0016-7037, 10.1016/j.gca.2012.01.015.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:31368
Deposited By: Jason Perez
Deposited On:09 May 2012 18:13
Last Modified:03 Mar 2020 13:01

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