Palynology and paleoecology of the Stone City member, Crockett Formation, Middle Eocene, Burleson Co, Texas

Abstract

A total of 103 genera and 157 species of terrestrial pollen, and at least 36 genera and 52 species of dinoflagellates were recovered from a core taken from the Stone City section in Burleson County, Texas. Both terrestrial and marine taxa confirm a Middle Eocene (Bartonian) age for the section. Analysis of the dinoflagellate taxa reveals that the environment of deposition of the core is open marine, shallow shelf. The presence of brackish and freshwater taxa intermixed with open marine taxa may be a result of high terrigenous input into the open marine environment. Analysis of the terrestrial pollen taxa indicate that the climate during deposition of this section was subtropical to tropical; furthermore, the abundance of terrestrial taxa in the core may identify a transport mechanism responsible for the introduction of the brackish and freshwater taxa into the open marine environment. Multivariate statistical analysis of the terrestrial and marine assemblages illustrates a stratigraphic relationship between taxa in samples, although no relationship to lithology was found. Principal Component Analysis of the dinoflagellates reveals a gradient between the brackish water and the open marine taxa in the section, and may indicate the possibility that the environment of deposition was on the limit of the salinity tolerances for both groups of taxa. Analysis of the terrestrial palynomorphs reveals slight changes in the terrestrial assemblages through time, although diversity was similar between most samples.