Sedimentary record of sources and accumulation of organic matter in Pyramid Lake, Nevada, over the past 1,000 years
Limnol. Oceanogr., 43(1), 1998, 160-169 | DOI: 10.4319/lo.1998.43.1.0160
ABSTRACT: We have examined the organic matter contents of two 210Pb-dated cores of sediment from Pyramid Lake for consequences of the historic environmental and limnological changes that have occurred since modem settlement of this region began in the 1850s. Agricultural diversion of Truckee River water has diminished the volume of this saline, terminal lake by one-fourth since 1905. Organic C : N ratios, organic d13C values, and terrigenous : aquatic n-alkane ratios indicate that the proportion of land-derived organic matter in sediments has decreased as river flow has decreased. Algal productivity also appears to have decreased since 1930. Some prehistorical variations in the delivery of organic matter are evident in older sediments. Elevations in the proportion of land plant wax and in C : N ratios in sediments deposited A.D. 1200-1400 suggest that contributions of land-derived organic matter were enhanced at this time. Proportions of biomarker n-alkanes indicate that grasses were more important than trees and shrubs as the dominant source of land plant waxes during this period, suggesting an interlude of regionally wetter climate.