DATING FELDSPAR USING POST-ISOTHERMAL LUMINESCENCE AND APPLICATION TO CLIMATE-SENSITIVE PALEOENVIRONMENTS

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Our planet is facing a critical part of its history as modern societies need to implement adaptation strategies to rapidly changing surface environments in response to global warming. Using the past to better apprehend the future, one should take advantage of the geological record as it contains archives that can be used to interpret the resilience or sensitivity of physical environments to climate change. These archives are represented mainly by sediments and in order to be accurately interpreted, they need to be inserted in a proper time-frame, hence dated. The main objective of this research program is therein to develop new dating methodologies in the field of feldspar luminescence for assessing the chronology of climate-sensitive geological and archaeological sedimentary archives. The scientific approach is to focus on the luminescence properties and the phenomenology of single feldspar grains in sediments. Due to the nature of its solid-state physics, luminescence dating of feldspar shall be applicable to a large part of the last million years of Earth history. This method can therefore probe one order of magnitude deeper into geological time than radiocarbon and more than 5 times the current age range of quartz optically-stimulated luminescence, routinely used in luminescence dating. Our recent work as resulted in the development of an innovative protocol in which low-temperature IRSL following post-isothermal treatments is shown to yield ages in accordance with the stratigraphical assignment for several samples from different parts of the world. This novel approach is now possible following the development of new instrumentation in luminescence readers, most of these are now available in the Montréal laboratory as a result of a major CFI funding to the UQAM geochronology group. This innovation shall provide precise as well as accurate age determinations as no correction for fading is needed. The detailed methodology is two-fold. 1) In order to develop a new method, laboratory protocols have to be devised and implemented, that will investigate the phenomenology of feldspar luminescence. This research shall contribute to HQP training for laboratory-focused and physics-inclined students. 2) These innovative methodologies will then be tested and validated in climate-sensitive geological contexts: a) “warm” interglacial coastal sediments, indicators of high sea level (e.g. USA, Brazil, Morocco), b) “cold” periglacial features (e.g. Yukon, Alaska). HQP training is strongly entangled in the specific research projects for field-oriented Earth sciences students.The novelty of this research and its upmost significance is in offering new ideas and concepts to the luminescence dating field as well as providing access to a new chronological tool for the natural sciences community involved in the science of Global Changes.