Late Pleistocene Vertebrate Fauna From Riddell Site Near Saskatoon, Canada

Abstract

Fluvial sand occurs between tills of the Floral Formation in the Saskatoon area and yields mammalian fossils. The recovered fauna is named the Riddell local fauna. The habitat preferences of the known extant species present in the fauna indicate that, at the time of deposition, open grassland with trees and shrubs in the low areas, predominated. The climate was probably equable; it did not suffer extremes of temperature or rainfall. The fossiliferous sand is thus distinctive from the underlying and overlying tills. The palaeontological evidence, in conjunction with lithological and radiometric data, indicates that the Floral Formation is composed of four distinct units. The fossiliferous sand member is here named the Riddell Member of the Floral Formation, and is defined on the basis of its contained vertebrate fauna. The Riddell local fauna contains the most northern record of Cynomys cf. C. ludovicianus and extends the known Pleistocene distribution of Equus conversidens farther north and east than previously reported. The presence of Spermophilus cf. S. undulatus in the fauna suggests that taxa whose modern distributions occur far to the north of the Saskatoon areawere part of a predominantly temperate fauna. The Riddell local fauna contains taxa the presence of which confirms a late Rancholabrean age. A late Sangamon (interglacial) or late early Wisconsin (interstadial) glacial stratigraphical age is indicated. The Riddell local fauna may be synchronous with the Fort Qu'Appelle (Echo Lake) vertebrate fauna but synchrony with the Wascana Creek Ash, dated at 600 000 years B.P. is not supported.