A review of the taphonomy of plant remains in lacustrine sediments

Abstract

Lacustrine sediments contain rich plant fossil assemblages because of rapid accumulation rates and the often close proximity of lakes to wetland and upland vegetation. An understanding of modern sedimentological processes that control accumulation of plant remains in lakes enhances the interpretation of ancient plant assemblages recovered from lacustrine rocks. The abundances of taxa in Holocene sediments and the degree of preservation are related to the distance and mode of transportation and to biological and mechanical degradation. These facts and the natural diversity of lacustrine sediments complicate the interpretation of fossil assemblages. Nevertheless, careful analysis of several factors increases the probability of correctly deciphering an ancient lacustrine assemblage of plant remains: (1) observation of mega- and microfossils; (2) analysis of faunal remains in context with plant remains and sediments; and (3) traditional bed-form and sedimentary structure analyses. Studies of the remarkable fossil occurrences from the Eocene of western North America, the Triassic of the eastern U.S., and the Permo-Triassic of South Africa provide an especially valuable body of paleofloristic data. Classic paleobotanical sites in the U.S., in particular, now require reinvestigation in the light of improved appreciation of the complexity of lacustrine phytotaphonomy.