In a paper I am reading, the authors note "large (5-7%) negative shifts in the oxygen isotopic composition of geologic proxy materials" (Davis 2008, pg. 102) in several regional basins. This is then interpreted by the authors as evidence of a significant tectonic change in elevation for the three basins being studied.

My question is regarding this scale of negative oxygen isotope shift (d18O). How much change in temperature would 5-7% suggest? Is there some online resource that might help me understand these factors of global climate versus local climate versus local tectonics better, as related specifically to oxygen isotope ratios and any details of actual temperature that can be inferred.

If relevant, the ratios are being measured in chert. The basins are all inland (western USA), in a fluvio-lacustrine environment that changes from open to closed various times. The 5-7% change in one basin is from 22.5% to 14.6% between 42-37 Ma (pg. 110); the basin I am studying. Another nearby basin, to the north, changes from 28.5% to 20.5% between 44.2-43.1 Ma (pg. 108). The third basin, to the south, changes from 17.2% to 13.2% between 44-40 Ma (pg. 109).

Source: Steven J. Davis, Andreas Mulch, Alan R. Carroll, Travis W. Horton, C. Page Chamberlain; Paleogene landscape evolution of the central North American Cordillera: Developing topography and hydrology in the Laramide foreland. GSA Bulletin ; 121 (1-2): 100–116. doi: https://doi.org/10.1130/B26308.1

Available online at: https://www.academia.edu/17709420/Paleogene_landscape_evolution_of_the_central_North_American_Cordillera_Developing_topography_and_hydrology_in_the_Laramide_foreland


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