SOURCES AND DISTRIBUTION OF ORGANIC AND CARBONATE CARBON IN SURFACE SEDIMENTS OF PYRAMID LAKE, NEVADA

Surface sediment samples from 32 sites in Pyramid Lake, Nevada, have b een studied to investigate the sources and distribution of carbon with in a large, terminal lake basin, The origins of organic and inorganic carbon in the sediments of this lake are predominantly from in-lake so urces, Dilution of these sedimentary materials by land-derived elastic components occurs near the mouth of the Truckee River, the only peren nial river entering the lake, Total organic carbon (TOC) concentration s and CaCO3 concentrations and delta(18)O values increase while organi c matter C/N atomic ratios and delta(13)C values decrease with increas ing distance from the river mouth as the proportion of river-derived c omponents decreases, Aragonite precipitates from lake water and domina tes CaCO3 deposition in most parts of the lake, except near underlake springs, where calcite precipitates, TOC concentrations increase as wa ter depth increases, reflecting grain sorting as smaller particles are resuspended and focused toward the deep basin center.