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Temp in Cretaceous

Thanks to Stan Friesen, someone is reading the papers!!!
The North Slope was at least at 70 degrees north (the present latitude), and
some paleomag measurements from sedimentary rocks in the foothills of the
Brooks Range indicate that paleolatitude could have been as much as 85
degrees north.  

The deltaic setting was right next to the Beaufort Sea, which probably did
play an ameliorating role in climate.  That is probably why the climate was
mild temperate and not colder--after all, because of the high latitude, the
winters had to be dark, and probably dusk for part of the fall and spring.
There has been some oxygen isotope paleotemperature work, but it is not
consistent and has not been published.  One study showed a tropical ocean,
which is not consistent with the marine fossils, and one recently by Mike
Arthur showed a more temperate temperature range.  

The seaway that extended from the Arctic to the Gulf of Mexico had indeed
receded to a small remnant in the Western Interior U.S. by late Cretaceous.
By the end of the Cretaceous the Arctic Ocean was isolated because the
seaway receded and a connection with the Atlantic was closed--the Pacific
connection did not reopen until about 3 million years, during the Pliocene.
The Atlantic seaway looks like it was open around the Paleocene or Eocene.

The first evidence of ice in the Arctic is in the Pliocene--Alaskan fossils
indicate about 2.4 my for the first real frigid marine animals in the fossil