The Pleistocene Floral Formation has been described from across central and southern Saskatchewan. In the Saskatoon area it comprises four distinct lithological units: a basal sand overlain by till and an upper sand overlain by till. The upper sand, here named the Riddell Member, contains the rich vertebrate composite Riddell fauna. The fossils are sufficiently distinctive to date the Riddell Member as Late Rancholabrean. This age is considerably younger than the age of the Wascana Creek ash and indicates that various deposits assigned to the Floral Formation are not correlative.Paleoecological analysis indicates that five ecological communities are represented in the composite Riddell fauna; the largest and most extensive habitat is the dry upland prairie. The sympatry of the represented taxa is unusual for central Saskatchewan and suggests that a temperate, equable climate prevailed. Paleoenvironmental reconstruction implies that the Riddell fauna is not synchronous with the Echo Lake fauna, but may be synchronous with the "Sangamon fauna" from Medicine Hat, Alberta.