by Jim North
Southeast Campus Editor
The basic geology of Tulsa consists of 300,000,000 year old rocks.
Claude Bolze is an associate professor of geology at Tulsa Community College (TCC).
He points out the geological history of Earth is divided into time periods, separated by hundreds of millions of years.
Sequences of rock are subdivided into rock types or “lithologies,” with Tulsa consisting primarily of sandstone, shale and limestone.
Most rocks in Oklahoma are sedimentary, according to Bolze, because they were deposited in water at Earth’s surface.
Igneous rocks, on the other hand, are a result of volcanic activity.
“To find igneous rocks in Oklahoma, we have to go to the southwestern part of the state, the Wichita Mountains, [primarily composed of] granite.”
Metamorphic rocks are not found in Oklahoma, says Bolze. But sedimentary rocks are in abundance, due to the sandstone deposited in streams or along beaches.
Sedimentary rocks are also deposited as flood plain along streams and quiet water offshore, as well as limestone where there is biological activity.
“It’s that biological activity that attracts me to the geology of Tulsa, because the biological activity contains fossils,” he adds.
Fossils are traces and remains of former living organisms and in Oklahoma limestone, there lie fossils.
There were dinosaurs in Tulsa at one time, explains Bolze. He adds that dinosaur bones will not be found in Tulsa due to the fact they are found in much younger rock, Mesozoic in age, 200,000,000 years ago.
“We do find dinosaurs in Oklahoma, but we have to go to Mesozoic-age rock in the Panhandle and along the Red River.”
He says bones are easier to find in the Panhandle than near the Red River because the abundance of vegetation near rivers makes discovery difficult.
The bare exposed rock in the Panhandle provides easier access to dinosaur bones, according to Bolze.
Oklahoma was submerged under water at one time as ocean, he points out. The sequence of rocks in the
northeastern part of the state is evidence of that fact.
“Pangea” was the super-continent of landmasses unified and theorized by geologist Alfred Wegener in the 1930s.
North America, Europe, Asia, Africa and South America were colliding and the collision of those produced the Appalachian Mountains. With the new production of land, the water had to flow down from the uplift, says Bolze.
“We’re at the western edge of this Appalachian formation, so we had land to the east and northeast. We had ocean to the west. Also during this time, we had glaciers taking place at the South Pole.”
Bolze goes further to say that with glaciers, the source of water for ice is the sea level and its oceans—so whenever glaciers were expanding, the sea level drops. When glaciers melt, sea level rises.
“That’s what we’re seeing here in the rocks of Tulsa. We have sandstones, shales and limestones. Sandstones are deposited when the sea level drops. Limestones deposit when sea level rises.”
“When seas go out, what we have close to land is sand. When the seas come in, we have deep water deposits, limestones and shales.”
Bolze describes the snapshot: “Oklahoma was under water. We had to the east, probably the boundary line of land and water was probably near Indiana, Illinois, or maybe as far east as western Pennsylvania.”
Besides Oklahoma, all of Colorado and California were under water.
The southern part of Africa, South America, Antarctica and Australia were near the South Pole, at the time.
Landmasses near the poles accumulate snow. The snow is compacted into ice and when the ice moves, it becomes a glacier, says Bolze.
He adds that Oklahoma was once near the equator. This can be determined by a concept called uniformitarianism: the study of present-day climate conditions reveals the past.
Near the equator, the climate is hot and tropical with rainforests and abundant biological activity.
Oklahoma’s water was both warm and tropical.
“You could swim all year round here in the oceans. It would be like the Bahama’s or Bermuda with the nice, luxurious, coastal conditions.”
As a result of Oklahoma’s tropical rainforests, trees fell over, thus getting buried in mud and then turning into coal.
Bolze points out, “Oklahoma has lots of coal deposits.”
At the same time, fish became more complex, along with plankton, floating plants and animals. They were microscopic and secreted a mineral shale—limestone silica. In order to stay afloat, those bodies had to produce oils, he says.
The oils, plankton and microscopic organisms sank to the sea floor, becoming buried by sand and shale, and were then squeezed into oil.
The result he adds is, “Oklahoma also has lots of oil. Geography in the area was ideal for coal production, oil production and life was fine.”
By the Permian age, glaciers had receded. Pangea was completely formed and Oklahoma then became mostly land.
“It’s [become] kind of a desert, so we’ve gone from a nice luxurious, Bermuda-type environment to a Sahara Desert.”
Evidence of the change can be seen in Oklahoma City, where the rocks are red. Red indicates abundance of oxygen and more dry, arid conditions, concludes Bolze.
Many downtown Tulsa buildings are composed of area rock, including the First Presbyterian Church, composition primarily limestone.
Oral Roberts University in Tulsa houses the Elsing Museum, where unique displays of Oklahoma rocks and others can be viewed. Go to elsing.oru.edu for tour information.
For more information about TCC geology classes, contact firstname.lastname@example.org.