Eocene lake environments: Depth and distance-from-shore variation in fish, insect, and plant assemblages

Eocene lake environments of British Columbia, Canada, and Washington State, U.S.A., are reconstructed using assemblages of fishes, fish bones, scales, and coprolites. Assemblages of terrestrial insects and terrestrial plant organs corroborate and help explain those based on fishes. For each fossil type, a major deep-water, off-shore/shallow-water, near-shore component of variation is apparent. This variation appears between stratigraphic intervals at one site, and between sites representing various Eocene lakes and formations. Deep/off-shore assemblages are more uniform and taxonomically less diverse than shallow/ near-shore assemblages. For terrestrial fossils, a near-shore/off-shore sorting by flying ability, wind, or floating is suggested. Fish assemblages are distinguished by taxa present and by degree of disarticulation. Shallow-water/near-shore assemblages have more amiids, percopsids, disarticulated fish, bibionids, incomplete insects, evergreen needles, and taxodiaceous leafy shoots. A moderately deep/near-shore assemblages has abundant salmonids and hiodontids. Deep-water/off-shore assemblages are dominated by articulated catostomid skeletons, catostomid scales, complete insects, dicot leaves, and wood.