| Summary: | Biogenic carbonates are valuable archives of paleoenvironmental information because they record chemical signatures of ambient environmental conditions during their formation. Therefore, long-term records of biogenic carbonates provide long-term records of environmental conditions that can be utilized to develop climate histories for specific regions to explore past climatic change. Traditionally, these studies have been conducted with low temporal resolution owing to analytical or economical restrictions. Although these records provide valuable information surrounding long-term climatic change, they lack the resolution to resolve the short-term climatic oscillations such as the Pacific Decadal Oscillation and El Niño Southern Oscillation that drive environmental change. This dissertation focuses on using high-resolution stable isotope analysis of biogenic carbonates for paleoenvironmental reconstruction and associated applications. Three studies are presented herein, applying increasing sampling resolution from sub-centennial, to sub-decadal, to sub-seasonal, that illustrate the diversity of paleoenvironmental information gained with each increase in resolution. The first study uses sub-centennial oxygen isotope analysis of authigenic lake carbonate to assess how climate change has affected precipitation patterns in the southern Yukon Territory from the end of the last glacial to the present day. Large changes in atmospheric circulation patterns associated with changes in the strength of the North Pacific High and the Aleutian Low pressure systems lead to variations in the oxygen isotope value of precipitation in the southwest Yukon Territory recorded in the oxygen isotope values of lake carbonate. The degradation of a glacial anticyclone led to a reduction in strength of the Aleutian Low coupled with an increase in the strength of the North Pacific High resulting in an increase in summer precipitation to the southwest Yukon represented by an increase in effective moisture following the transition from the Late Pleistocene to the Early Holocene. The second study is a sub-decadal oxygen isotope record of lacustrine carbonate stretching back 8,000 years to quantify the strength and state of the Pacific/North American (PNA) Index through time. This study relies on the relationship between the PNA Index and the oxygen isotope values of precipitation from central Canada (Birks and Edwards, 2009), and the ability of Sturgeon Lake to accurately represent 18O values of precipitation. Results show that the strength of the PNA varied through time. The Early to Mid-Holocene (8,000- 4,200 years BP) is characterized by large fluctuations between PNA+ and PNA– phases; PNA–-like conditions dominate the period after 4,200 years BP; and ~1,800 years BP PNA+-like conditions resume. Changes in the Holocene PNA pattern are shown to be contemporaneous with similar changes in Holocene records of El Niño illustrating the intrinsic relationship between Pacific climate patterns. The final study uses sub-seasonal oxygen isotope records from bivalves derived from an overwash deposit to define the seasonality of the deposit. Data indicate a late spring to early summer timing of deposition that presents an alternative interpretation to the previous late fall tsunami origin hypothesis. In conclusion, this dissertation focused on improving our understanding of how paleoenvironmental information is archived in biogenic carbonates by focusing on the use of high-resolution sampling strategies. Modifying the sampling resolution resulted in an enhanced understanding of how short-term climate oscillations drive climate and illustrates how the type of paleoenvironmental information generated varies with sampling resolution.
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