Evening star., 1950-05-22
Fossils Yield New Duto
On Ancient Inland SEQ
Arctic Oceans Solt Tides
Once loshed New Mexico Hills
By Thomos R. Henry

BY Thomos R. Henry
Four times the Arctic Ocean thrust
long arms southwark into the western
interior Of North America.
At the fartheSt extension its salt tides
lashed the hills around the present site
of Albuquerque. N Mex. Edmonton and
Calgary in Canada, and Butte. Cheyenne.
Denver and Salt Lake City were at the
bottom Of a shallow sea.
This was during the so-called JuraSsic
geological period. On land 1t was the
heyday of the giant dinosaurs. The
ancestors Of birds were making their
first appearance. The sea waters were
thronged with weird monSters-icthyo.
Saurs and pleSiosaurs-gigantic flesh
eating marine reptiles closely related
to the dinosaurs. 1t was one of the
most disturbed periods of the planets
history.
A comprehensive picture Of this great
inland sea which advanced and retreated
four times. based on studies of fossils
and rock formations, has just been
prepared by the Division of Geology
and Geography Of the National Research
Council. During its last three advances
it extended southwark at least 2.S00
miles and had q maximum width of
about 800 miles,
Each invasion spread farther south
and southeast than the preceding one,
but the waters never quite succeeded
in joining up either with the Gulf OF
Mexico or the Pacific. 1t stretched
between low-lying shores. For the most
part 1t was salt sea in q desert, ex-
cept for small area of the present
western Montana, where rainfall appears
to have been plentiful and vegetation
abundant.
1t was a shallow. warm, clear sea.
In the last few million years of its
history. however. the changing fauna
shown by fossil remains, indicate that
the waters were growing colder.
This study was carried out by Or.
Ralph w. INLAY of the Geological Sur
Vey. The existence Of the ancient sea
has long been known but there has
been no consistent picture of its ebbs
and surges and its probable shore lines.
Throughout its history, DR.. Inlay
finds from his study of fossils and geo.
logical strata, the inland sea was cut
OIL from the Pacific. with which it
never had any connection, by q narrow
land mass which extended from Mexico
as far as the Yukon. 1t was cut of from
the Gulf of Mexico by hilly country In
central Arkansas, southern Oklahoma
and central Texas.
This separation was about $50 miles
wide. 1t was bounded on the east.
through what is now Minnesota and the
DakotaS. by highlands which were ex-
tensions of the very ancient rocks of
eastern Canada.
There were numerous islands and very
shallow areas in the warm sea, particu-
larly in Montana and Colorado where
the waters barely succeeded In reaching
the tops Of low mountains. The average
depth. at the utmost. cannot have been
more than 800 feet.
Each Arctic invasion spread somewhat
further south than the preceding one.
So far as the fossil evidence goes the
first influx came only as far south as
the town of Fernie in extreme south
eastern British Columbia Inlets, how
ever. may have penetrated as far as the
present Montana border.
The second spread southwark to
northern Arizona but was very narrow.
1t never reached western Colorado nor
southeastern Wyoming. The third pro-
duced sea Of considerably greater
width. During this period. land up.
heavals of this sort cut of part of 1t
and produced a typical dead sea" in
Utah. southern Idaho and southwestern
Wyoming. This is indicated by great
salt deposits.
The fourth invasion was by far the
fastest and most extensive. The waters
soon receded. geologically speaking,
from northern Arizona to eastern Al
berta. where they persisted throughout
the Jurassic period.
During much of this seas history.
the evidence indicates. the inflow Of
water from the Arctic was quite slug.
gish. Probably fairly cold when it left
the polar regions. 1t had plenty Of time
to become lukewarm under the SOUTH
ern sun.
There must have been an abundant
life in the ooZe Of the ancient sea bottom.
for fossils show the existence. some
times In great numbers Of most Of
the invertebrate animals known today.