Abstract The earliest eukaryotes recorded in continental environments are non-pollen palynomorphs (NPP) in Mesoproterozoic strata, and NPP provide our best insights into lacustrine ecosystems through the Paleogene. They have been underexploited in studies of younger lake sediments, either ignored or only qualitatively observed, because many NPP are destroyed by standard processing techniques for pollen and embryophyte spores. The palaeoenvironmental potential of palynomorphs, with representatives from all eukaryotic kingdoms as well as cyanobacteria and from all trophic levels in various lacustrine environments, has been recognized by a few Quaternary palynologists in the past few decades. NPP have proven particularly valuable in archaeological and environmental monitoring studies of human impact on freshwater ecosystems, with spores of some fungi and eggs/egg cases of some flatworms and roundworms associated with faeces of humans and livestock, and the acid-resistant remains of various life stages of cyanobacteria, algae and their aquatic consumers responding to increased turbidity and nutrient influx associated with permanent human settlements, particularly those associated with agricultural activity. Descriptions of NPP commonly encountered in Quaternary lake sediments and case studies illustrating applications to various research questions should encourage more palynologists that ‘“Quaternary non-pollen palynomorphs” deserve our attention!’, to quote Prof. Bas van Geel (2006 , Review of Paleobotany and Palynology , 141 , vii–viii, https://doi.org/10.1016/j.revpalbo.2006.04.001 ), undisputed Father of NPP research.

ABSTRACT The late Eocene Florissant Formation in central Colorado is a rich and diverse continental Lagerstätte yielding well-preserved fossil assemblages from lacustrine and fluvial facies. This investigation focused on the lacustrine facies at Clare’s Quarry and used biotic and abiotic evidence to characterize aspects of the lake and processes that resulted in the accumulation and preservation of the host rock and its fossils. Autecology of modern analogs representing the fossil diatom taxa was used to augment sedimentary data in characterizing the lake, propose peripheral habitats within the catchment area, and suggest a terrestrial source for mudstone units. The sedimentary and stratigraphic record at the study site reveals a lake with sufficient depth to allow bottom waters to remain isolated and anoxic for long periods. Sediments that accumulated in the lake produced distinct lacustrine lithofacies that are interpreted as representing at least three modes of origin: stable lake, pyroclastic, and mud turbidite sedimentation. Slow, suspension settling of fine clays and volcanic ash into a moderately deep, stable lake resulted in laminated shales. These laminated shales contain frustules of diatoms from planktic and benthic lake habitats; diatoms transported into the lake from streams and wetlands; fish, mollusks, ostracods, and insects; and plants from marginal and upslope environments. Intermittent volcanic eruptions produced air-fall ash and granular tuff that accumulated as interbeds within the lake shales. Periods of stable lake sedimentation were frequently interrupted by rapid influxes of suspended fine clays, perhaps as mud-dominated turbidites that prograded into the lake at intervals of high runoff triggered by climatic, volcanic, or tectonic events.