Denuded Ouachita Rock Belt

Duane's take

This one comes straight off an official Texas Historical Commission marker, and I'll tell it to you just the way the rock tells it to anyone patient enough to listen. Now, out here in Brewster County, if you glance toward the east in those highway cuts, you're looking at something that'll make your timeline feel real small. Almost vertical rock layers standing up like they're at attention, part of what geologists call the Ouachita Fold Belt.

A northeasterly trending, folded and faulted mountain range that was uplifted somewhere between two hundred seventy-five and two hundred ninety million years ago. Let that sink in while the road rolls under you. The deformation you're seeing is comparable in age to the uplift that built the Appalachian Range away off in the eastern United States.

So what you've got here is a mirror of those old eastern mountains, written in stone right along a Texas highway cut. The name Ouachita, it traces to the Ouachita Mountains of Arkansas and Oklahoma, and those mountains were named by the Indians, whose words were then rendered into written language by the sixteenth century French explorers. Layers upon layers, in more ways than one.

Now here's where the story takes a turn. Swing your gaze toward the northeast, and the hillside tells a different chapter. Those highly deformed strata, twisted, tilted, ancient, are overlaid by rock layers sitting almost perfectly horizontal.

Younger rock. Formed about a hundred and thirty-five million years ago. How do you get neat, flat layers sitting on top of all that chaos?

Well, erosion wore down those old mountains. Wore them right down. And when the sea came in and covered this area, those horizontal layers were quietly deposited on the sea floor.

Patient as anything. Then came yet another round of uplifting earth movement, comparable in age to the forming of the Rocky Mountain range, that gently elevated this whole region back up, handing it over to the erosional forces that have been sculpting the topography you see right now out that window. Two hundred ninety million years of push and pull, flood and rise, mountain and sea floor and mountain again.

This region, the marker tells us, abounds in vivid lessons in geology, and it is under constant study by scientists. Out here in Brewster County, the rocks aren't just scenery; they're the longest story Texas has got to tell.

What the marker says

In highway cuts toward the east are excellent exposures of almost vertical rocks layers--part of the Ouachita Fold Belt, a northeasterly trending folded and faulted mountainous range which was uplifted about 275 to 290 million years ago. The deformation is comparable in age to the uplift that formed the Appalachian Range of the eastern United States. The term "Ouachita" for this earth formation comes from the Ouachita Mountains of Arkansas and Oklahoma. (These were named by the Indians, whose words were rendered into written language by the 16th century French explorers.) In the hillside toward the northeast, the highly deformed strata are overlaid by almost horizontal layers of "younger" rock--formed about 135 million years ago. Erosion wore down the old mountains; and when the area was coverd by the sea, the horizontal layers were deposited on the sea floor. Later uplifting earth movement comparable in age to the forming of the Rocky Mountain range gently elevated this area, exposing it to erosional forces which have shaped the topography seen today. This region abounds in vivid lessons in geology, and is under constant study by scientists.