Rocks and Ancient People in Southeastern New Mexico

The immensity and stark beauty of the Pecos River valley in southeastern New Mexico has long been a source of wonder for travelers to the area. Throughout this landscape, there is a staggering variety of rock types—some dramatically exposed as outcrops and others swept into the area by the Pecos River and its tributaries. An example of the dramatic landforms that characterize the area is the Llano Estacado, or “Stockaded Plains.” At approximately 32,000 square miles—an area greater than all of New England—the Llano Estacado is one of the largest mesas on the continent. The Llano Estacado stops abruptly west of the New Mexico state line at a long, steep slope formed of caliche caprock, the Caprock Escarpment. This slope extends for miles from north to south, breaking the uniformity of the plains. A series of terraces and sand dunes to the west leads down into the Pecos River valley; this landscape varies markedly from the high-desert scenery of the Llano Estacado. On the other side of the river, additional terraces lead to the gently dipping Pecos Slope, the broad eastern flank of the Sacramento Mountains, and ultimately to ever-steeper hills and narrow, rugged canyons of limestone. Southeastern New Mexico is renowned not only for its remarkable geology but for the long history of human occupation recorded in its vast and varied landscape—a history we are still piecing together. Many questions are still being answered: What rocks did the ancient inhabitants of the region use to make stone tools? Where did they find these materials? What remains at these locations that might help us understand the techniques they used to produce these tools?