If we are not able to isolate sufficient quantities of terrestrial matter to produce high-resolution 14C chronologies, we will consider alternative materials for 14C dating. However, aquatic matter is subject to a lake reservoir effect that can make high-resolution chronostratigraphic correlation between lake systems difficult. Radiocarbon plateaus are an additional impediment to the development of a high-resolution chronology. In varved sediments, we will use annual records of charcoal deposition using both the area and sieve methods to determine the frequency of fire. In non-varved sediments, we will use the sieve method only.
N can indicate changes in source and supply of organic matter.
Routine analysis of organic matter is preformed by the loss on ignition technique. Our previous work has shown that in highly organic sediments the LOI technique is sufficiently accurate and rapid to be a measure of organic content. In cores where stable isotope analyses are preformed, organic C and N are determined as part of the stable isotope analysis. Calcium Carbonate Carbonates are rare in Holocene sediments of most interior lakes. We will determine if carbonates are present by the loss on ignition technique.