Sediment cores were collected (GPS coordinates taken) at three transects, one at the north end of Utah Lake and two within a kilometer of the Lake on the Jordan River. The cores were sub-sampled at 5 cm resolution for sediment grain size, C and N stable isotope and C/N ratio, and lead-210 analyses. All sampling was standardized. Sampling data is one time data (summer field collection). Carbon and nitrogen stable isotope compositions show a 4 per mil and a 2 per mil positive shift, respectively, as a depth of 55cm. C/N ratios show large variations (9-18) at depths shallower that 55cm, but are more stable (11-14) with greater depth. These results indicate a shift in organic matter sources to Utah Lake at a depth of 55cm, which likely represents the boundary between pre- and post-pioneer settlement in the valley around 1847. At depths greater than 55cm, the major contribution of soil organic matter was likely terrestrial C3 and autochthonous native C4 plants, whereas at depths shallower than 55cm terrestrial vegetation, manure/sewage-derived matter, and lake algae were the major lake organic matter sources. From this information, we approximate the post-settlement sedimentation rate in the lake to be 3.3mm/yr. Students and leads were responsible for data collection, data analysis, and data interpretation of the project.
isotopes,Utah Lake,grain size,Jordan River
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