Old Crow PlainThe Old Crow Plain, about 5000 km2, elev 300 m, referred to locally as Old Crow Flats, is the northernmost part of the Porcupine Plateau in the Yukon, lying north of the Arctic Circle and 150 km south of the BEAUFORT SEA. The name honours the memory of a chieftain of the Gwich'in tribe. The plain is a pristine wilderness area underlain by continuous PERMAFROST and covered with a myriad of shallow lakes and ponds, some of which have an oriented rectangular shape related to prevailing wind directions and to patterned ground phenomena, eg, ice polygons and wedges.
The vegetation is of the tundra type, with outliers of the boreal spruce forest; willow thickets line the course of the Old Crow River. Geologically the plain represents the floor of the intermontane Old Crow Basin, a structural depression of Tertiary age linking the Eastern and Interior Systems of the Cordillera. The basin is bordered on the east by the Richardson Mountains, on the north by the British Mountains and on the west and south by the Old Crow Range. The underlying sediments include a veneer of Holocene and Pleistocene clays, silts, sands and organics, overlying a thick sequence of Tertiary, Mesozoic and Palaeozoic sediments and sedimentary rocks, some of which are potentially oil bearing.
The basin was one of the few areas in Canada untouched by glaciation during the Pleistocene ICE AGES, and it served as a refuge for many ice-age animals. However, abandoned high-level shorelines indicate that the flats were inundated by proglacial lakes during the ice ages. The modern Old Crow River, which joins the Porcupine River at the native village of OLD CROW, is a meandering stream with numerous cutoffs and a well-defined terrace system. The river bluffs have yielded an enormous quantity of mammalian bones, together with artifacts of PREHISTORY.