UpDate - Vol. 11, No. 28, Page 1
April 23, 1992
Rare Miocene fossil bed find first on Delmarva Peninsula

     A newly discovered fossil bed dating back some 17 or 18 million
years provides proof that Delaware was once inhabited by crocodiles,
rhinoceroses and small horses no bigger than Irish setters.
     The find has been called the most important fossil discovery on
the Delmarva Peninsula this century.
     The Miocene era fossils were discovered last fall when Scott
Andres of the Delaware Geological Survey, housed at the University of
Delaware, visited a sand pit being dug near Garrison's Lake between
Smyrna and Dover by contractors for the Delaware Department of
Transportation (DelDOT).
     Evidence of prolific marine life- fossilized clams, oysters and
snails- was found 5 feet below present sea level. By the time the pit
reached 20 feet below, teeth and bones of vertebrates ranging from
crocodiles and rhinoceroses to sharks and whales were unearthed.
Remains of early beaver, rabbit, a small peccary and an extinct
deer-like animal also have been identified.
     "It's hard to find fossil beds in Delaware," says Kelvin W.
Ramsey, associate scientist with the survey. "The state is generally
flat so we don't have deep highway road cuts, and the water table is
so high we usually don't have deep excavations. This excavation, which
was providing road fill for the new relief route, went unusually deep.
Now, it's about 25 feet below sea level."
     Many types of teeth have been found, Ramsey said, because they
are the hardest bones and most easily preserved. Geologists have
identified nine different types of shark teeth, grinding teeth from a
cow-nose stingray, tiny teeth from coral-grazing fish, at least one
tooth from an ancient crocodile and the horse teeth.
     Although fossil evidence indicates that most animals inhabiting
Delaware during the Miocene era would be recognizable today, some-like
the horse and the whale-were smaller and still others are now extinct.
"Bones were found that are possibly part of a Chalicothere, a strange,
horse-like animal with claws on its three-toed feet," Ramsey says. "On
the other hand, we've identified oysters of the same species that now
live in Delaware Bay.
     "This is the earliest known occurrence of these oysters, so
Delaware can be called the birthplace of the edible oyster," he adds.
     Ramsey speculates that the climate of Delaware was warmer 17
million years ago, probably similar to that of northern Florida or
southern Georgia. The Atlantic Coast reached about 50 miles further
inland than it does today, and shrubby trees and palms grew close to
the shifting shoreline. Because grasses had not developed yet, the
small horses, rhinos and the chalicotheres probably browsed on the
trees and shrubs much as deer do today, he says.
     Fossils of both land and marine species are mingled in one site.
     Several staff members of the Smithsonian Institution are working
on the vertebrate remains to better determine the geology of the site,
Ramsey says. And Lauck Ward of the Virginia Museum of Natural History
is studying the shells. "In fact, the Smithsonian researchers are
particularly excited about the diversity of mammal remains. This may
well provide the best collection of Miocene mammal fossils on the East
Coast of the United States," he says.
     Microfossils of protozoa, such as radiolaria and foraminifera,
are being examined carefully by Richard Benson of the Survey because
these creatures are found world-wide in deep seas and can be used to
date the site with a small time frame, he adds.
     Important as a significant Miocene fossil find in Delaware, the
site is also of interest to geologists because it is part of the
Cheswold aquifer, a subsurface zone that provides drinking water for
the towns of Cheswold and Dover. The study of the geology of the site
will be useful in predicting and modeling groundwater reserves.
     "It's rare to actually get our hands on an aquifer," Ramsey says.
"Normally, we just see records from a well driller or a core sample.
This site will help us understand where the aquifer is located in the
subsurface and how water is stored and moves through the aquifer.
     "We have a short window of opportunity to study these sands and
collect specimens because ultimately the site will be graded over and
water will be allowed to return to normal levels."
     University geologists have gained a little extra time to look for
rare fossils, however. DelDOT has delivered three truckloads of sand
from the site for the scientists to sift through.
     -Cornelia Weil