Stable-isotope changes in tufa stromatolites of the Quaternary Añamaza fluvial system (Iberian Ranges, Spain)
The stable isotope composition (S’3C and S,80) of the laminae in three Quaternary, calcitic, tufa strom atolites of different ages (M IS6, M IS 5 a n d M IS1 ) in the Anamaza valley are studied and compared with the modern tufa in the Ahamaza river. The cyclic textural variations represent thick cya...
| Authors: | ; ; ; ; |
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| Format: | Article |
| Publication date: | 2017 |
| Country: | España |
| Institution: | Universidad de Huelva (UHU) |
| Repository: | Arias Montano. Repositorio Institucional de la Universidad de Huelva |
| Language: | English |
| OAI Identifier: | oai:ariasmontano.uhu.es:10272/14549 |
| Online Access: | http://hdl.handle.net/10272/14549 |
| Access Level: | Open access |
| Keyword: | Stromatolite texture Stable isotopes Fluvial tufa Pleistocene Textura de estromatolitos Isótopos estables Tobas fluviales Pleistoceno Holoceno |
| Summary: | The stable isotope composition (S’3C and S,80) of the laminae in three Quaternary, calcitic, tufa strom atolites of different ages (M IS6, M IS 5 a n d M IS1 ) in the Anamaza valley are studied and compared with the modern tufa in the Ahamaza river. The cyclic textural variations represent thick cyanobacteria! growth in the light laminae and thin or absent cyanobacteria! growth in the dark laminae. The textural cyclicity is parallel to 8 180 changes: Each light-dark couplet corresponds to one year in which the light lamina (lower 8 ’80 values) represents warmer water temperatures (Tw) than the dark lamina (higher 8 ’80 values). This is consistent with the fact that the large crystals composing the dark laminae correspond to precipitation in the absence of microbial films and likely represent the coldest conditions. The 8 ,s0 ^ -derived Tw from M IS 5 stromatolite is higher than the MIS6 and MIS 1 samples, which agrees with the commonly admitted climatic conditions during MIS5 in NE Iberia. Moreover, S^O^mi Tw from MIS6 suggests a wider yearly Tw range than the two other samples. The higher a n d more disperse S ,3C values o f the M IS1 stromatolite are consisten t with the peculiarities o f the vegetal co ver a n d the de cre a se d w a ter availability in the Holocene |
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