Geology of Ohio
The two geologies of Ohio are limestone, found in the western part, and sandstone, found in eastern Ohio. Limestone is a rock type that is nonresistant in humid climates, resulting in erosion and being worn down to a flat landscape. On the other hand, sandstone is a relatively resistant rock type, only resulting in carved out deep valleys, but not wearing away at higher land.
The Sequence of Sedimentary Rock Strata
The original sequence of sedimentary rock strata is a thick layer of limestone overlain by shales, which is overlain by sandstone. Before erosion began, the sequence of sedimentary rock was in the form of a low arch. This arch was a product of the pressures which created the Appalachian Mountains in the east. The crest is the oldest rock, which extends north-south through western Ohio. Farther east, the youngest rock layers of sandstone were not removed, creating sandstone hills. Most of the erosion of all the limestone is in western Ohio and the shale/sandstone in the east was accomplished by a preglacial stream called Teays River, which was present in Ohio for about 200 million years.
When the Pleistocene glaciers came through Ohio, they were slowed down greatly by the steep-sided sandstone hills in eastern Ohio. This resulted in a glacial boundary in Ohio, going no farther south than the latitude of Canton.
Source: Linking Geology and Botony by Jane Forsyth; https://ohioplants.org/geobotany/
Glacial till is mainly found on the plains of western Ohio. It is a limy, clayey substrate that provides impermeable soil, high in lime but poorly drained and inadequately aerated. This causes the water to not soak in very quickly, forcing it to remain on the surface and create low oxygen availability during wet periods and dry spells. In eastern Ohio, however, the substrate is a very permeable sandstone bedrock and produces a very acidic, low-nutrient substrate.
Basic Substrate for Plants in Western and Eastern Ohio
Western Ohio: Impermeable soil, high in lime, poorly drained and inadequately aerated, low oxygen, abundant nutrient availability
Eastern Ohio: Permeable sandstone bedrock, very acidic, well-drained, low-nutrient substrate
Trees/shrubs that have a distribution generally limited to limestone or limey substrates
This group also includes, but is not pictured: Redbud and Blue Ash
Trees/shrubs that have a distribution generally limited to high-lime, clay-rich substrates developed in the thick glacial till of western Ohio
Sugar Maple, Beech, Red Oak, Shagbark Hickory, and White Oak
Trees/shrubs that have a distribution generally limited to sandstone hill of eastern Ohio
Sourwood, Mountain Laurel, Scrub Pine, Eastern Hemlock, Chestnut Oak, and Pitch Pine
Major Determinant of the Distribution of Species
a) sweet buckeye: outside of the glacial boundary; problems with repopulation in the clayey, high-lime glacial tills; restrictions unknown
b) hemlock: outside of the glacial boundary; restriction to continuously cool, moist environments like in deep valleys
c) rhododendron: belong to the mixed mesophytic association; lived in the Appalachian highlands and migrated down through the preglacial Teays River system