Carbon isotopes in aquatic plants, Long Valley caldera, California as records of past hydrothermal and magmatic activity

摘要

Hot and cold springs contribute "dead" (C-14 free) dissolved inorganic carbon (DIC) to the Owens River and Hot Creek. Headwaters aquatic plants have modem C-14, but live plants downstream of the intracaldera springs are depleted in C-14, (,, low as 19% modem, with apparent ages up to 13.3 kyrs). In an abandoned meander of the upper Owens River, preserved streambed plants are buried by 600 year old Inyo Craters pumice. Apparent C-14 ages of these plants exceed true ages by similar to 1100 years indicating that they also incorporated dead DIC as they grew. The preserved plants are downstream of Big Springs, whose elevated dead DIC may represent magmatic `CO2. The buried plants incorporated similar to 10% dead carbon, although modern plants here have similar to 50% dead carbon, suggesting that more magmatic CO, is now entering the upper Owens River than at the time of the Inyo Craters eruptions 600 years ago. [References: 20]