Significance of Preburial Taphonomic Processes to Visual Organic Analyses of Recent Lacustrine Sediments of Reelfoot Lake, Tennessee

Jeff S. Beckner, Michael J. Andrejko

Visual microscopic analyses of the recent lacustrine sediments of Reelfoot Lake in northwestern Tennessee revealed a possible paradox between the organic matter (OM) types expected versus those presently accumulating within this small lacustrine-palustrine environment. Based on the present wetland habitats, the dispersed OM actively being accumulated should predominantly consist of herbaceous (Type II) and woody (Type III) debris. However, preliminary observations revealed abundant Type I, amorphous/sapropel-like dispersed OM in bottom sediments.

Two biologic conditions may account for some taphonomic loss. The lake is located within the northern end of the Mississippi Embayment and, therefore, is situated directly in a major migrational route for water-fowl. The Environmental Protection Agency reported that 16.1% of the total phosphorous loading into the lake results from feeding activities of wild ducks and geese, suggesting that a considerable part of OM being deposited in the lake has been affected by avian activities. Also, in 1983, 30,000 White Amur (grass carp) fish were introduced into the lake to control the aquatic vegetation encroachment. These fish can consume and digest mass quantities of aquatic vegetation during their lifetime (average 5-7 years). Thus, such aquatic herbivores also should account for a significa t amount of the "erosional" activity within this environment.

These observations of biologic activities indicate that OM may be degraded considerably, penecontemporaneously with deposition. Therefore, these factors should be considered when evaluating visual kerogen analyses of organic-rich lacustrine sequences.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.