This paper focuses on the flux and characterization of organic substances in cave drip waters for a continental climate. At Marengo Cave in southern Indiana, there is seasonal variations in organic matter concentration in the cave drip water. High levels are introduced during the spring thaw, and lower levels occur during the rest of the year. The fluorescence spectra and ultrafiltration analysis suggest the majority of the organics contained in percolating waters were fulvic acids, with most being less than 1 kDa in size. The seasonal flush of organics from the soil could produce two different types of calcite in the speleothem deposited from these drip waters, a stronger fluorescing calcite during the spring and the less fluorescent calcite during the rest of the year. This is the first study of its type for this particular climatic region.