Organic Fluvial Sediment - Palynomorphs and Palynodebris in the Lower Trinity River, Texas

In 1961-1962, the author studied the lower Trinity River, Texas, for palynomorph content, as a model of how pollen, spores, and palynodebris reach depositional areas for incorporation in sedimentary rocks. The river was selected partly because it was at that time relatively undisturbed by industry and damming. Three stations were selected for surface and mid-depth water sample collection, 00 in Trinity Bay, 04 on the Trinity River delta, and 09 on the lower Trinity River. Palynomorph loads at 04 and 09 were especially high, often reaching 10(5) or more per 100 liters of water. Water of the bay station usually contained much lower concentrations of palynomorphs. A wide range of pollen and spore types occurred in the water, dominated by major floral elements of the lower Trinity River area, but including forms from farther upstream. Reworked pollen and spores, eroded from rocks hundreds of kilometers north and northwest of the sampling localities, were regularly recovered. Engelhardia/Momipites-type pollen of Paleogene age was an especially significant reworked form. There were seasonal changes in the composition of the palynoflora, reflecting flowering peaks such as that of Taxodium (swamp cypress) in late winter and Poaceae (grass) in summer. In 1985-1986, the same stations were once again sampled. Since the earlier sampling, damming upstream had created Lake Livingston, which acts as a huge settling basin, resulting in decreased palynomorph load in the water at all stations in the lower river. Fungal spores as well as pollen apparently have been reduced in concentration. A sampling in 1986 of the lake itself and of the river at its inlet tends to confirm that the lake acts as a settling basin for waterborne palynomorphs. Rivers deliver a sampling of the terrestrial flora, via palynomorphs and palynodebris. to the continental shelf. In total, this particulate organic matter is an important part of the earth's budget of buried carbon. Studies of the palynomorph-palynodebris load of streams therefore contribute to understanding the origin and fate of organic matter in sedimentary rocks