161 miospore species and 122 microplankton species are described from 106 samples in six sections of the Lower Colorado Group and its equivalents in central and west-central Alberta. Two miospore species, and two genera and twenty-five species of microplankton, are newly described. The miospore and microplankton assemblages are used as a basis for division of the Lower Colorado Group into several time-stratigraphic units. The age of the Group is determined as Upper Albian (latest Lower Cretaceous). A method for defining recurrent microplankton species groups is developed and applied to assemblages from two of the sections. The distribution of the recurrent groups formulated is shown to be correlated in part with palynological, lithological and other data. Application and extension of the results and conclusions of this investigation should prove useful in understanding many aspects of western Canadian Cretaceous stratigraphy and in the investigation of microplankton occurrence patterns from other deposits. / Thesis / Doctor of Philosophy (PhD)