Paleo-precipitation from speleothem fluid inclusions

Speleothems (inorganic carbonate deposits in caves, also known as dripstones) are a relatively new and - compared to lake sediments, deep-sea sediments or tree rings - underinvestigated archive of paleoclimatology. Their importance has risen worldwide primarily because these formations allow precise age dating of environmental changes for the past 500,000 years. On a microscopic scale speleothems contain minute amounts of water trapped during slow growth of their calcite crystals. It is these fluid inclusions and their isotopic composition that provide the most direct source of information about climate in the past. This proposal aims at analyzing the stable hydrogen isotopic composition of fluid inclusions from well characterized alpine speleothem samples by using a combination of two techniques, crushing in vacuum and in-situ extraction using a laser. The former is a method established a few years ago in Great Britain, but still used only by a few laboratories worldwide, while the latter technique is novel and has not yet been applied to speleothems. A laser system will be set up at the stable isotope laboratory at Innsbruck University in collaboration with Prof. Z. Sharp (USA), one of the leading scientists in the field of in-situ isotope analysis of geomaterials. Application of this method will allow for the first time to determine the stable isotopic composition of shallow paleo-groundwater and hence paleo-precipitation in the greater alpine region. Given the well established relationship between this parameter and climate, these new data will greatly increase our ability to quantify climate and climate change in the Alps during the past few hundreds of thousands of years.

Speleothems (inorganic carbonate deposits in caves, also known as dripstones) are a relatively new and - compared to lake sediments, deep-sea sediments or tree rings - underinvestigated archive of paleoclimatology. Their importance has risen worldwide primarily because these formations allow precise age dating of environmental changes for the past 500,000 years. On a microscopic scale speleothems contain minute amounts of water trapped during slow growth of their calcite crystals. It is these fluid inclusions and their isotopic composition that provide the most direct source of information about climate in the past. This proposal aims at analyzing the stable hydrogen isotopic composition of fluid inclusions from well characterized alpine speleothem samples by using a combination of two techniques, crushing in vacuum and in-situ extraction using a laser. The former is a method established a few years ago in Great Britain, but still used only by a few laboratories worldwide, while the latter technique is novel and has not yet been applied to speleothems. A laser system will be set up at the stable isotope laboratory at Innsbruck University in collaboration with Prof. Z. Sharp (USA), one of the leading scientists in the field of in-situ isotope analysis of geomaterials. Application of this method will allow for the first time to determine the stable isotopic composition of shallow paleo-groundwater and hence paleo-precipitation in the greater alpine region. Given the well established relationship between this parameter and climate, these new data will greatly increase our ability to quantify climate and climate change in the Alps during the past few hundreds of thousands of years.