Brasier, A., Andrews, J.E., Marca-Bell, A.D. and Dennis, P.F. (2010) Depositional continuity of seasonally laminated tufas: Implications for δ18O based palaeotemperatures. Global and Planetary Change, 71(3-4), pp. 160-167. (doi: 10.1016/j.gloplacha.2009.03.022)
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Publisher's URL: http://www.elsevier.com/locate/gloplacha
Abstract
A ~100 ka old laminated tufa (freshwater carbonate) deposit from central Greece was studied for evidence of a seasonal origin of the laminae. Annual laminar couplets (6 mm thick) consist of dense β bands of spring– early summer calcified cyanobacterial bushes and porous α bands of autumn precipitated calcite on unclustered cyanobacterial filaments. This is evidence of likely seasonal palaeoclimate during the last interglacial in Greece. δ<sup>18</sup>O variability is explained by seasonal changes in stream water temperature; however, the total range in δ<sup>18</sup>O translates to ~6 °C (±1 °C) almost certainly underestimating the likely actual range of ~17 °C. As abrupt changes in δ<sup>18</sup>O inferred temperatures (from warming to cooling and vice versa) occur exactly on sharp petrographic lamina boundaries, we infer that mid-summer and mid-winter precipitates are missing. We suggest that when stream conditions (summer drying and winter cold) are unsuited to cyanobacterial substrate development, no tufa build-up occurs. Laminated tufas are thus incomplete records of annual tufa formation, as are the δ18O based palaeoclimate records they preserve. They require careful petrographic study linked to high resolution sampling for δ<sup>18</sup>O to ensure that palaeotemperature ranges are not seriously underestimated.
| Item Type: | Articles |
|---|---|
| Keywords: | laminated tufa; stable isotopes; geochemistry; last interglacial; Greece |
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Brasier, Dr Alexander |
| Authors: | Brasier, A., Andrews, J.E., Marca-Bell, A.D., and Dennis, P.F. |
| Subjects: | G Geography. Anthropology. Recreation > GE Environmental Sciences |
| College/School: | College of Science and Engineering > Scottish Universities Environmental Research Centre |
| Journal Name: | Global and Planetary Change |
| Publisher: | Elsevier |
| ISSN: | 0921-8181 |
| ISSN (Online): | 1872-6364 |
| Published Online: | 23 April 2009 |
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