262 The American Geologist. October, 1897 
cussion, is alread^^ so well known that a few words in regard 
to it will suffice atr the present time. Throughout the coun- 
tr}^ within twenty miles on either side of the Mississippi 
river, from St. Paul to the Wapsijjinicon and Green River 
basins in Iowa and Illinois, the streams flow in comparatively 
narrow, steep-sided valleys, wliich have a present depth be- 
tween 100 and 600 feet. The rock bottom of these valleys is 
everywhere from 100 to 200 feet beneath the present stream 
level, indicating that the land was once more elevated than 
at present. 
They are not narrow and deep enough to constitute true 
canons as the term is applied in the southwest, but their form 
and mode of origin are such as to include tiiem under the 
class of "canon valleys." In age, they occupy the time inter- 
val between the completion of the Tertiary peneplain and the 
opening of the Kansan epoch of glaciation. The peneplain is 
probablj' identical in age with that in the southern Appalach- 
ian region, which is the product of the Tennesseean epoch of 
degradation as lately defined by McGee. This was followed, 
in the coastal plain and Mississippi embayment regions, by 
the Lafayette submergence and epoch of aggradation. As 
the same Avriter has indicated, this Lafa3^ette subsidence of 
the territor}' now occupied by the southern states, must have 
been accompanied by a tilting and possible slight uplift of 
the central and upper Mississippi regions, to revive the senile 
streams and enable them to supply to the sea at their mouths, 
material which was rapidly gathered from the red residuary 
clay of the land surface. It is probable that the basin valleys 
of northwestei-n Illinois belong to this Lafayette period of 
increased Ftream action. The Lafayette submergence of the 
continental border was terminated by a marked uplift of the 
entire eastern portion of North America, and to this epoch 
belongs our canon valleys. All that portion of the valleys of 
the upper Mississippi region, which lies beneath the level of 
the floor of the basin valleys, should be classed as Ozarkian 
in age, this name having lately been proposed for the epoch 
between the Lafa3'ette and the Kansan. 
The age and origin of the present Mississijrpi river. Above 
the city of Minneapolis, the Mississippi river flows in a shal- 
low valley channeled beneath the surface of great drift plains. 
