Geological Science Field Trips 2009-2010
Fall 2009: Garden of the Gods Recreation AreaShawnee National Forest
Saline, Gallatin, Pope, and Hardin Counties
October 24, 2009 and November 14, 2009
The Garden of the Gods area is located within the Shawnee Hills of
southern Illinois. Trip participants will view many interesting rock
formations, given names such as Camel Rock, Anvil Rock, and Devil's
Smokestack. These rock formations and cliffs at the Garden of the
Gods are made of sandstone deposited 320 million years ago during
the Pennsylvanian Period. Overlying these sandstones, in the
northern part of the field trip area, are the Pennsylvanian
coal-bearing shales, siltstones, and sandstones formed about 300
million years ago. In the southern portion of the field trip area
lie exposures of older limestones and shales that were deposited
during the Mississippian Period about 340 million years ago, when
Illinois lay close to the equator and near the shore of a shallow
tropical sea. These Mississippian bedrock layers hold abundant
marine fossils.
The Garden of the Gods area of southern Illinois is south of the rolling topography of the glaciated till plains of the Illinois Glacial Episode. The hilly topography (hence, the name, Shawnee Hills) is a result of tectonic uplift and the absence of glaciation. Within the Shawnee National Forest are large natural ecosystems relatively unchanged by humans. While hiking the trails in this unglaciated area, field trip participants will experience some of Illinois' unique biodiversity, including sandstone glades, upland forests, and deep mesic (wet) ravines where distinctive relict northern plant species have persisted since preglacial times.
Participants should meet before 8:15 a.m. at the parking lot of the U.S. Forest Service office in Harrisburg. To reach the office, take U.S. Route 45 south out of Harrisburg and turn left onto highway 145 and 34 south. The Forest Service office is located on the right side of the road.
Updated 9/11/2009 SLD