Owens Lake is situated in a mostly-closed basin fed by water and sediments derived primarily from the eastern Sierra Nevada range. Radiogenic isotope variations in USGS Owens Lake core OL-92 were used in conjunction with major and trace element concentrations in streams draining the eastern Sierras to investigate sediment provenance, the chemical weathering and transport of rare earth elements (REE) in the Owens Lake drainage basin, and possible climate-related shifts in weathering patterns of the eastern Sierras during the last ~30 ka. Filtered (<0.45 μm) stream water samples not influenced by hydrothermal fluids or agriculture fall below world average-normalized values for major cations. Concentrations of Nd in the stream water samples are less than 1 nmol L-1, too dilute for isotopic analysis. Strontium and neodymium isotopic analyses were conducted on the carbonate and silicate fractions of sediment samples representing deposition in Owens Lake from ~30 ka to ~10 ka. The fraction of carbonate in Owens Lake sediments increases from ~7 to 67 % during this period, reflecting the desiccation of the lake. Strontium, samarium, and neodymium are strongly partitioned into Owens Lake chemical sediments. Over the past ~30 ka, epsilon Nd values of clastic sediments in Owens Lake remain relatively constant, near -6.5. Chemical sediments remain approximately one epsilon unit higher than the clastic sediments until ~12 ka ago, at which time they shift to less radiogenic values, matching those of the clastic sediment. Differential mineral weathering of more common mineral phases over REE-enriched accessory phases is the most likely cause of the isotopic shift in Owens Lake chemical sediments at ~12 ka ago. Preferential weathering of hornblende could displace the Nd isotopic composition of Owens Lake chemical sediments away from that of the clastic fraction. Depletion of hornblende could allow the Nd isotopic composition of the two sediment fractions to return to similar values. This study represents the first Nd isotope study of a lacustrine system and suggests Nd isotopes could be a useful paleoclimate proxy. Additional work in older Owens Lake sediments and in other lake systems is clearly warranted.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-12192001-143918 |
| Date | 11 March 2002 |
| Creators | Minervini, Joseph Mario |
| Contributors | William P. Harbert, Rosemary C. Capo, Brian W. Stewart |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu:80/ETD/available/etd-12192001-143918/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
Page generated in 0.0021 seconds