- Title
- Replicate palaeoclimate multi-proxy data series from different speleothems from N. Italy: reproducibility of the data and new methodologies
- Creator
- Belli, Romina
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2013
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Changes in geochemical and physical properties of speleothems are considered to be accurate proxies of climate variability. However, the climate signal is modified by the internal dynamics of the whole karst system. The aim of the research was to obtain reproducible data extracted by established and non-conventional techniques from two coeval speleothems removed at Grotta Savi cave (Italy), to gain information about regional climate responses across the Last Glacial Maximum to Holocene transition. Different past hydrological regimes for the two stalagmites’ drips were reconstructed on the basis of stalagmites’ physical characteristics and this helped to disentangle the global from the local phenomena. This non-conventional approach, was applied here for the first time on fossil sample, resulting in a benchmark for interpreting the chemical proxies, and enabling assessment of calcite formation environment, hitherto not possible. The interpretation of δ18O values as reflecting past hydrology was then validated by using the Hydrology Index. The Index, developed in this study, considers two independent proxies: the Mg concentrations and the fraction of Sr uptake that is not dictated by growth rates. The method allowed recognition of a non-hydrological component encapsulated in δ18O values, then interpreted as changes of air mass provenance and rainfall seasonality. The δ13C was chiefly driven by temperature-dependent soil respiration rate. However, a hydrological component was also detected in the δ13C by using dead carbon proportion (dcp) and 87Sr/86Sr ratios. Increases of 87Sr/86Sr ratios suggest increases of aeolian dust deflated from proximal subalpine periglacial regions facilitated by vegetation-cover reduction, soil destabilisation and windier conditions, which in turn enhanced drier conditions. Although, the dcp trend was likely related to a local, faster, soil organic matter turnover, enhanced by warmer conditions, episodes of high dcp values were possibly hydrologically induced, as a result of wetter conditions. Furthermore, the Hydrology Index and δ13C signal allowed reconstructing that wet conditions occurred during climate cooling, an improvement relative to the state of the art of δ13C interpretation, where more commonly wet conditions occurs during warming. The comparison of δ13C trend of Savi with another stalagmite with similar physical characteristics, but from a cave (Sofular) located in Turkey, revealed a common trend despite the impact of the last glaciation having been drastic at Savi (no speleothem growth). Such δ13C similarity could be related to global phenomena and point to an intriguing possibility, which needs future testing, that speleothems may encode information of the C cycle, similar to soil carbonates. The palaeoclimate interpretation extracted from the Savi records between 15 to 9 ka indicates that the Younger Dryas (YD) was a dramatic climate reversal. In the northern Adriatic, the YD is characterised by high hydrological variability, strong winds and a cooling, which resulted in a decrease of vegetation cover and increase of soil erosion. The wind regime was possibly orographically induced, with the Alps acting as a barrier, deviating westerly winds and causing increased windiness in the northern Adriatic region. The Savi records reveal a significant Early Holocene anomaly (10.4 ka), whose drier and colder conditions were probably amplified by a local synoptic framework.
- Subject
- palaeoclimate; calcite fabric; stalagmite; trace elements; radiocarbon; strontium isotopes; stable isotopes
- Identifier
- http://hdl.handle.net/1959.13/1037787
- Identifier
- uon:13485
- Rights
- Copyright 2013 Romina Belli
- Language
- eng
- Full Text
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