Palaeoenvironment of late Neogene lacustrine sediments at the Gray Fossil Site, Tennessee, USA

Abstract

A new palaeopalynological investigation was conducted on 15 samples from four test-pits at the Gray Fossil Site (Bear Pit, Elephant Pit, Test Pit 2-2010, and Rhino Pit). In total, 50 morpho-species of miospores (including five species of spores, eight species of gymnosperm pollen, and 37 species of an giosperm pollen) and 18 morpho-species of fresh water algal micro-remains were identified. One new morphological species, related to zygospores of the Zygnemataceae, Stigmozygodites grayensis sp. nov., is proposed. The assemblage of fossil algae recovered provides in sights into the palaeoenvironmental conditions of the uppermost (125 cm) part of the Gray Fossil Site sedimentary cover, deposited after the formation of a number of sink holes, and the fill of the palaeosinkholes. Most of the algae identified prefer meso- to eutrophic conditions and are characteristic of stagnant to slowly flowing shallow fresh water. Therefore, the lacustrine fossiliferous sediments at the Gray Fossil Site represent pond deposits. The palaeopalynological analysis revealed differences in the composition of the miospore and algal assemblages of the pits studied, suggesting that the Test Pit 2-2010, Bear, and Elephant pits are similar and may have been formed in the same pond, while the presence of a higher percentage of algae in the Rhino Pit may indicate sedimentation in a separate waterbody.