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Ice Sheets Caused Massive Sea Level Change During Late Cretaceous
Ice Sheets Caused Massive Sea Level Change During Late Cretaceous (Period
was previously thought to be ice-free)
ARLINGTON, Va.Scientists using cores drilled from the New Jersey coastal
plain have found that ice sheets likely caused massive sea level change
during the Late Cretaceous Period -an interval previously thought to be
ice-free. The scientists, who will publish their results in the
March-April issue of the Geological Society of America (GSA) Bulletin,
assert that either ice sheets grew and decayed in that greenhouse world or
our understanding of sea level mechanisms is fundamentally flawed.
Led by Kenneth Miller of Rutgers University, the scientists examined cores
from Ocean Drilling Program Leg 174AX, an onshore extension of an offshore
expedition. They found indications that sea level changes were large (more
than 25 meters) and rapid (occurring on scales ranging from thousands to
less than a million years) during the Late Cretaceous greenhouse world
(99- 65 million years ago).
Analyses indicate minimal tectonic effects on the New Jersey Coastal Plain
at this time, the scientists say. The other explanation for such large,
rapid changes is the waxing and waning of large continental ice sheets,
they maintain. What is perplexing, however, is that such large and rapid
sea-level changes occurred during an interval thought to be ice free.
"Our studies of cores in New Jersey provide one of the best- dated
estimates of how fast and how much sea level changed during the greenhouse
world of the Late Cretaceous," said Miller. "The Earth was certainly much
warmer at that time, probably due to high carbon dioxide levels in the
atmosphere. At the same time, our estimates require that ice sheets grew
and decayed on Antarctica during this period of peak warmth, which has
been a previously heretical view."
The scientists propose that the ice sheets were restricted in area to
Antarctica and were ephemeral. The ice sheets would not have reached the
Antarctic coast, explaining the relative warmth in Antarctica, but still
could significantly alter global sea level.