FOSSIL FIELD TRIP TO
OHIO AND INDIANA
On Saturday, 20 November 2010, the geology club took a
fossil collecting field trip to southwestern Ohio and southeastern
Indiana. The first stop was Caesar Creek Lake State Park. The visitor
center near the dam for the lake has several fossil displays of local Late
Ordovician-aged fossils, including a large, complete Isotelus trilobite (Ohio's
official state fossil), plus modern wildlife-related exhibits. A couple
hour's worth of fossil collecting was done at the nearby Caesar Creek
Lake’s emergency spillway, which has an extensive exposure of interbedded
fossiliferous limestones and fossiliferous shales (Waynesville Formation,
Liberty Formation, Whitewater Formation - all Upper Ordovician). Commonly
seen fossils included brachiopods, bryozoans, nautiloids, clams, snails, and
trilobite fragments.
Fossil collecting at Caesar Creek Lake's emergency spillway
(northeastern Warren County, southwestern Ohio, USA). The walls &
slopes of this exposure are interbedded limestone & shale, all richly
fossiliferous. The beds that stick out are the limestones. The gray
beds in-between are the shales. The most common type of fossil found here
is brachiopod shells (lower right-hand corner) - this one is Rafinesquina
ponderosa.
Fossiliferous limestone - this fossil plate is typical of the limestone
interbeds exposed at Caesar Creek Lake's emergency spillway (northeastern
Warren County, southwestern Ohio, USA). The shells are various species of
brachiopods, dominated by the strophomenid brachiopod Rafinesquina ponderosa.
This is from the upper Liberty Formation or lower Whitewater Formation (upper
Cincinnatian Series, upper Upper Ordovician).
A large roadcut in southeastern Indiana was visited
next - Southgate Hill along Rt. 1, north of St. Leon and south of the
Whitewater River. The rocks there also included interbedded limestones
and shales, all richly fossiliferous, and the same age as the rocks at Caesar
Creek. The fossils seen at Caesar Creek were also seen at Southgate
Hill. Unusual finds of the day included a small, but nice, lustrous
pyrite crystal mass and the head of a rare local trilobite, Ceraurus
milleranus.
Southgate Hill - this is part of a large roadcut in southeastern
Indiana, USA. The rocks are interbedded fossiliferous limestones and
shales. The slope in the center of this photo is the upper Waynesville
Formation (Cincinnatian Series, upper Upper Ordovician).