- GeoRef, Copyright 2004, American Geological Institute. Reference includes data from Bibliography and Index of North American Geology, U. S. Geological Survey, Reston, VA, United States
A mid-Cretaceous Minnesota lacustrine deposit, capped by a lignite and then channeled by a Cretaceous stream, has yielded a number of megaspores of both aquatic ferns and aquatic and terrestrial lycopods. Distribution of these megaspores shows differences in percentages in the several depositional environments. The lacustrine and fluvial deposits contain spores derived from the uplands, as well as those also occurring in the lignite. The lignite, representing deposition in a swamp, lacks Costatheca and Spermatites, and has a high incidence of Tenellisporites. Two new species are described, Tenellisporites spiinatus and Ariadnaesporites varius.