Geolipid, pollen and diaton stratigraphy in postglacial lacustrine sediments

Abstract

As part of our continuing investigation of specific compounds as organic matter indicators in lake bottoms, we have examined geolipids, pollen and diatoms in sediments from different periods in the postglacial history of Heart Lake, New York. Sediment core sections representing the major watershed vegetation periods were extracted for unbound and bound fatty acids, hydrocarbons and alcohols. Fatty acids constitute most of the extracted material. Minor decreases in unsaturated acids with depth indicate little degradation of organic matter in these sediments. The dominant unbound n-alkanoic acid in the core sections is either C 22 or C 24, but bound fractions contain few long chain acids and are dominated by n-C 16. Nearly all the hydrocarbons are found in the unbound fraction. The ratio of C 29/C 17 n-alkanes increases from the bottom of the core to near the top as watershed forests have matured and lake productivity has diminished, but drops since European settlement of the region. Organic degradation in this lake bottom is mild, and input indicators appear to be well preserved.