Biology Reference
In-Depth Information
going of seas and lakes over geologic time has been a signifi cant forcing
mechanism for climatic change and biotic response.
The midcontinent sea began to drain in the Middle Cretaceous as a result
of uplift of the continent, waning of plate tectonic activity, and less fl ood ba-
salt pouring onto the ocean fl oor. By the mid-Eocene at 45 Ma, the margin
of the sea ran from south of Laredo / Nuevo Laredo northward to just east
of Austin, Texas, up the Mississippi Embayment to about Cairo, Illinois,
around the southern end of the Appalachian Mountains, and northward
along the eastern edge of the mountains. By the beginning of the Pleisto-
cene epoch about 2.6 Ma, the coastline had retreated to its approximate
Figure 2.10
Diagram of the northern North American continent during the Middle to Late
Cretaceous showing the epicontinental sea and the
Aquilapollenites
and Normapolles prov-
inces. Numbers represent prominent fossil fl oras outlining the margin of the sea: (1) McNairy,
(2) Lower Atanekerdluk, (3) Vermejo, (4) Raton, (5) Denver, (6) Laramie, (7) Patterson,
(8) Hell Creek-Lance (Colgate), (9) Scollard, Horseshoe Canyon, (10) Coalspur, (11) Prince
Creek (Coville River site). Used with permission from Oxford University Press, Oxford.
