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| Titel |
Stable isotope paleoclimatology of the earliest Eocene using kimberlite-hosted mummified wood from the Canadian Subarctic |
| VerfasserIn |
B. A. Hook, J. Halfar, Z. Gedalof, J. Bollmann, D. J. Schulze |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 20 ; Nr. 12, no. 20 (2015-10-16), S.5899-5914 |
| Datensatznummer |
250118127
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| Publikation (Nr.) |
 copernicus.org/bg-12-5899-2015.pdf |
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| Zusammenfassung |
| The recent discovery of well-preserved mummified wood buried within a
subarctic kimberlite diamond mine prompted a paleoclimatic study of the
early Eocene "hothouse" (ca. 53.3 Ma). At the time of kimberlite eruption,
the Subarctic was warm and humid producing a temperate rainforest biome well
north of the Arctic Circle. Previous studies have estimated that mean annual
temperatures in this region were 4–20 °C in the early Eocene,
using a variety of proxies including leaf margin analysis and stable
isotopes (δ13C and δ18O) of fossil cellulose.
Here, we examine stable isotopes of tree-ring cellulose at subannual- to
annual-scale resolution, using the oldest viable cellulose found to date. We
use mechanistic models and transfer functions to estimate earliest Eocene
temperatures using mummified cellulose, which was well preserved in the
kimberlite. Multiple samples of Piceoxylon wood within the kimberlite were crossdated
by tree-ring width. Multiple proxies are used in combination to tease apart
likely environmental factors influencing the tree physiology and growth in
the unique extinct ecosystem of the Polar rainforest. Calculations of
interannual variation in temperature over a multidecadal time-slice in the
early Eocene are presented, with a mean annual temperature (MAT) estimate of
11.4 °C (1 σ = 1.8 °C) based on δ18O, which is 16 °C warmer than the current MAT of the area
(−4.6 °C). Early Eocene atmospheric δ13C (δ13Catm) estimates were −5.5 (±0.7) ‰. Isotopic discrimination
(Δ) and leaf intercellular pCO2 ratio
(ci/ca) were similar to modern values (Δ = 18.7 ± 0.8 ‰; ci/ca = 0.63 ± 0.03 %), but
intrinsic water use efficiency (Early Eocene iWUE = 211 ± 20 μmol mol−1) was over twice the level found in modern high-latitude
trees. Dual-isotope spectral analysis suggests that multidecadal climate
cycles somewhat similar to the modern Pacific Decadal Oscillation likely
drove temperature and cloudiness trends on 20–30-year timescales,
influencing photosynthetic productivity and tree growth patterns. |
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