SEDIMENTATION IN MACKENZIE RIVER BASIN 343 
greater Lake Athabasca which was a contemporary of Lake Agassiz. 
Similar beds occur along the lower Slave River (Fig. 2), which belong 
to the period when a much greater Slave Lake was developing the 
Fic. 2.—Lacustrine sediments on the Slave River near Salt River, representing 
deposits of a former greatly extended stage of Great Slave Lake. Photograph by 
E. J. Whittaker. 
wave-cut cliffs and elevated beaches now found far back from its 
shores. The following section, taken above Little Rapids on the 
Peace, indicates the general character of these lacustrine beds: 
MRTOTES De Cuarl dia SOnl ny aah p pend Wien tisees alan t foot 
ZR BTOWNNSATIG ie Chey iset cn fn Me eu. 3 feet 
Ge OLeSt DEGaye LC. ne ait) cotaas Mesmvaten el gia end 6 inches to o 
4. Gray sand with pebble band in middle....... 1 foot 
Peelardssanduwithvlimy bands a peer = eT TOOk 
OB Nihite mar ey Aes oie ysl en aat atm m Ore 4" 340.2 8 inches to o 
jeg Giay, sang with calcined moots. yan)... 25 feet 
See Narhyssain dhyeci icy isin ela ene nod ees rusk 2 inches 
g. Gray even-bedded sand partly covered....... 30 feet 
The broad low plain of lacustrine sands which have been 
extensively re-worked by the river, extends from the pre-Cambrian 
hills east of Slave River and the lower Athabasca many miles to the 
westward. It meets the foot of a plateau called the Caribou 
Mountains west of the Slave River, while a similar upland known 
