Farley, K. A. and Eltgroth, S. F. (2003) An alternative age model for the Paleocene-Eocene thermal maximum using extraterrestrial ^3He. Earth and Planetary Science Letters, 208 (2-4). pp. 135-148. ISSN 0012-821X http://resolver.caltech.edu/CaltechAUTHORS:20121115-093445626
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A continuous age model for the brief climate excursion at the Paleocene–Eocene boundary has been constructed by assuming a constant flux of extraterrestrial ^3He (^3He_(ET)) to the seafloor. ^3He_(ET) measurements from ODP Site 690 provide quantitative evidence for the rapid onset (<few kyr) and short duration (<120 kyr) of global warming and of the associated disturbance to the Earth’s surficial carbon budget at this time. These observations support astronomically calibrated age models indicating extremely rapid release of isotopically light carbon, possibly from seafloor methane hydrate, as the proximal cause of the event. However, the ^3He_(ET) technique indicates a previously unrecognized and extreme increase in sedimentation rate coincident with the return of climate proxies to pre-event values. The ^3He_(ET)-based age model thus suggests a far more rapid recovery from the climatic perturbation than previously proposed or predicted on the basis of the modern carbon cycle, and so may indicate additional or accelerated mechanisms of carbon removal from the ocean–atmosphere system during this period. ^3He_(ET) was also measured at ODP Site 1051 to test the validity of the Site 690 chronology. Comparison of these data sets seems to require removal of several tens of kyr of sediment within the climatic excursion at Site 1051, an observation consistent with sediment structures and previous age modeling efforts. The Site 1051 age model shows a ∼30 kyr period in which climate proxies return toward pre-event values, after which they remain invariant for ∼80 kyr. If this rise represents the recovery interval identified at Site 690, then the ^3He_(ET)-based age models of the two sites are in good agreement. However, alternative interpretations are possible, and work on less disrupted sites is required to evaluate the reliability of the proposed new chronology of the climate excursion. Regardless of these details, this work shows that the ^3He_(ET) technique can provide useful independent evidence for the development and testing of astronomically calibrated age models.
|Additional Information:||© 2003 Elsevier Science B.V. Received 27 September 2002; received in revised form 5 January 2003; accepted 8 January 2003. We thank Tim Bralower for guidance, encouragement and helpful comments on the manuscript, Debbie Thomas for preparation of samples from Site 690, and constructive reviews by Jim Zachos and Franco Marcantonio. This work was supported by NSF EAR-9909448 and by a Fellowship from the David and Lucille Packard Foundation to K.A.F.[BARD]|
|Official Citation:||K.A. Farley, S.F. Eltgroth, An alternative age model for the Paleocene–Eocene thermal maximum using extraterrestrial 3He, Earth and Planetary Science Letters, Volume 208, Issues 3–4, 30 March 2003, Pages 135-148, ISSN 0012-821X, 10.1016/S0012-821X(03)00017-7. (http://www.sciencedirect.com/science/article/pii/S0012821X03000177)|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||15 Nov 2012 17:52|
|Last Modified:||27 Dec 2012 03:01|
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