It is noteworthy that Johnston county contains precambrian rock from the creation of Earth.
Quote from the linked article ...
Precambrian
(Beginning of earth - 543 million years ago)
All geologic time before the beginning of the Paleozoic era. This includes about 90% of all geologic time and spans the time from the beginning of the earth, about 3.8 billion years ago, to 543 million years ago. Its name means "before Cambrian." The Precambrian is divided into the "Proterozoic" and the "Archean".
CVO Menu - America's Volcanic Past - Oklahoma: "Arbuckle Mountains
Arbuckle Mountains:1
Granite exposed in the Arbuckle Mountains in Johnston County is 1.4 billion years old. It is the oldest rock exposed between the southern Appalachians and the Rocky Mountains. The Arbuckle Mountains are an area of low to moderate hills in south-central Oklahoma. They contain a core of Precambrian granite and gneiss formed about 1,300 million years ago; in the western Arbuckles, Precambrian rocks are overlain by at least 5,000 feet of Cambrian rhyolites formed about 525 million years ago. Most of the Arbuckles consist of 15,000 feet of folded and faulted limestones, dolomites, sandstones, and shales deposited in shallow seas from Late Cambrian through Pennsylvanian time (515 - 290 million years ago). Folding and uplift of the mountains occurred during several mountain-building episodes in the Pennsylvanian Period.
What is the Precambrian?
What is Granite?
What is Gneiss?
What is Rhyolite?
MORE Arbuckle Mountains:1
The Arbuckle Mountains are an area of low to moderate hills in south-central Oklahoma. They contain a core of Precambrian granite and gneiss formed about 1,300 million years ago; in the western Arbuckles, Precambrian rocks are overlain by at least 5,000 feet of Cambrian rhyolites formed about 525 million years ago. Most of the Arbuckles consist of 15,000 feet of folded and faulted limestones, dolomites, sandstones, and shales deposited in shallow seas from Late Cambrian through Pennsylvanian time (515-290 million years ago). Folding and uplift of the mountains occurred during several mountain-building episodes in the Pennsylvanian Period. The complex mountain area probably was never more than several thousand feet above the surrounding plains and s"
