| Title | Evaluating the integrity of C and O isotopes in sub-fossil wood from boreal lakes |
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| Author | Savard, M M ;
Bégin, C; Marion, J; Arsenault, D; Bégin, Y |
| Source | Palaeogeography, Palaeoclimatology, Palaeoecology vol. 348-349, 2012 p. 21-31, https://doi.org/10.1016/j.palaeo.2012.06.003 |
| Image |  |
| Year | 2012 |
| Alt Series | Earth Sciences Sector, Contribution Series 20120104 |
| Publisher | Elsevier BV |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Province | Quebec |
| NTS | 23B; 23E; 23J |
| Area | Caniapiscau River; Nitchequon; Wabush; Schefferville |
| Lat/Long WENS | -71.0000 -66.0000 56.0000 52.0000 |
| Subjects | paleontology; Nature and Environment; isotopes; carbon isotopes; oxygen isotopes; isotope ratios; petrified wood |
| Illustrations | location maps; photographs; plots |
| Program | Climate Change Geoscience |
| Released | 2012 09 01 |
| Abstract | Extending climatic series back to the first millennium using isotopic tree-ring chronologies in northern regions represents a challenge because trees seldom reach the adequate age. Fossil trees
deposited in boreal lakes could serve such an endeavor provided that dating the tree-ring series is possible and that the isotopic ratios of sub-fossil wood are preserved. From two boreal lakes in north-eastern Canada, we collected segments of Picea
mariana (black spruce) stems with different degrees of wood textural preservation and covering the last millennium. Our main objectives are to assess the selection criteria for wood textures suitable for isotopic reconstruction, and verify the
reliability of sub-fossil cellulose carbon and oxygen isotopic series for climatic reconstruction in boreal regions. The isotopic differences between cellulose and lignin obtained for 48 ring pairs of a living tree (delta delta13Cc-l=3.7±0.3permil;
delta delta18Oc-l=13±1) and 46 contemporaneous pairs from a subfossil stem (3.5±0.3 and 12.9±0.9permil in the same order), are systematic and matching. For the selection of all sub-fossil samples, we have visually identified three main classes of
wood textures for which the degree of alteration is confirmed by secondary electron microscopy: well preserved, slightly altered and highly altered. Slightly altered stem segments have cellulose proportion showing a relative decrease reaching 35%,
but delta delta13Cc-l and delta delta18Oc-l values within the range of living trees. Non-altered sub-fossil stems covering the 14th and 11th centuries show systematic and coherent delta delta13Cc-l (3.5±0.2; 3.8±0.4permil) and delta delta18Oc-l
results (13.9±0.7; 13.5±0.5permil). Highly altered wood shows a decrease in both cellulose proportion and delta18Ocellulose values, but apparently preserved delta13C ratios. This research shows that it is possible to visually identify the degree of
wood preservation and preselect sub-fossil segments holding reliable isotope-ratios, and to use subfossil stems collected from boreal lake floors to reconstruct climate over the last millennia. |
| GEOSCAN ID | 291482 |
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