Bulletin 3. The flora of the Raritan Formation, 1911 - State of New ...

GEOGRAPHICAtL DISTRIBUTION. 5I
Eastern America during the tong interval of elevation and erosion,
which occupied all of Jurassic time, offers many potential
possibilities as a theater of evolution, as it undoubtedly was, but
the simultaneous appearance of identical types in the mid-Cretaceous
of Europe and.America and Greenland is hard to understand
if either America or Asia was the center of dispersal. The
remaining alternative is that of regarding the A_'etic area as the
scene of evolution and center of dispersal of the modern flora,
and, possibly, the fauna as well. The facts, while suggestive,
are insufficient for definite conclusions. They serve to explain,
for instance, the presence of the oldest known Comptouia in
deposits in Greenland, New Jersey, Sweden and Bohemia, which
are probably all of Cenomanian age; the presence of Morlcouia
from Greenland southward to South Carolina on this continent
and in central Europe at the same time. In fact, numberless
parallels could be drawn between the Albian and Cenomanian
of America and Europe, so that at least tentatively we may picture
successive waves of plant migration sweeping southward
from the Arctic region somewhat as indicated by the arrows in
Figure 3, the recorded floras of middle and later Cretaceous age
being indicated by the solid black areas..
Fig. 3.--Sketch map of the world, showing approximate location of mid-
Cretaceous plant-bearing deposits (ia hl.ack). Arrows indicate _ossible directions
of migration.
NEW JERSEY GEOLOGICAL SURVEY