Kincaid Shelter

Kincaid Shelter (41UV2) is a stratified archeological site in Uvalde County, Texas, an area poised between the verdant, rugged beauty of the Hill Country and the more desert-like plains of South Texas. Carved into a low limestone bluff of the Cretaceous-age Anacacho formation, the shelter extends inward to form a semi-circular "room" roughly 32 feet deep by 35 feet wide (about 10 by 11 meters) in size. The shelter ceiling is an irregular dome, a feature which suggests that the shelter may have formed as a solution cavern later dissected by the river cutting into the bluff.

The shelter is located in the Balcones Fault zone near the northern edge of the Rio Grande Plain. There, the low flat land of the coastal plain gives way to a belt of low rolling hills and rocky terrain that marks the southern margin of the Edwards Plateau. Changes in surface elevation are abrupt, ranging from about 900 feet (275 m) above sea level near the shelter to more than 1,900 feet (582 m) above sea level on the plateau. The climate of the region is semi-arid, and in the vicinity of the Kincaid Shelter (as well as farther south) the climate is somewhat hotter and drier than on the higher plateau.

The Kincaid Shelter lies within an ecotone, or transitional zone between different plant communities—the Tamaulipan biotic province of the coastal plain and the Balconian biotic province of the Edwards Plateau. For prehistoric peoples, this meant a rich mix of resources—nuts, fruits, seeds, and various kinds of wildlife—was available nearby. By striking off in different directions, different sets of resources were encountered.

The Tamaulipan is dominated by thorny and arid-adapted brush such as mesquite, acacia, cenizo, white brush, prickly pear and tasajillo. Within the Balconian province, oak and juniper savannas dominate the uplands and slopes and hardwood forests line canyons and valleys. Bald cypress, sycamore, black willow, pecan, black walnut, and other trees thrive along more-permanent streams. Species characteristic of both biotic provinces occur in the immediate vicinity of Kincaid Shelter.

The Sabinal River today flows within 500 feet of the shelter. Its headwaters lie about 40 miles to the north on the Edwards Plateau. Within the plateau, the river is deeply entrenched in Cretaceous limestones of the Glen Rose, Comanche Peak, and Edwards formations. Springs issuing from the porous Glen Rose maintain a nearly permanent flow of water for a distance of 20 to 25 miles. During periods of normal flow, the water disappears underground at the Balcones Fault zone not far upstream from Kincaid Shelter. The water drains into thick streambed gravels and through a series of fractures in the Edwards Limestone. During major floods, the Sabinal flows across the fault zone and onto the Gulf Coastal Plain where it joins the Frio River.

At Kincaid Shelter, the Sabinal is dry most of the time, but a semi-permanent pool is present about 2500 feet (762 meters) downstream. This pool has been known to dry-up in historical times (e.g. summer of 1953), but standing water persisted in another pool about one-half mile upstream from the shelter. A pool also remained about three miles downstream during the prolonged drought of the 1950s.

In the vicinity of the shelter, the Sabinal River bed is floored with modern limestone gravel bars that rise 6 to 8 feet above the river bed. An incipient flood plain (alluvial terrace), whose surface averages about 14 feet above the stream bed, also occurs as disconnected "bench" segments along the present channel. These modern deposits, still in the process of active development, are not directly related to any of the cultural material in the Kincaid Shelter.

An older, well-developed alluvial terrace is closely related to the cultural deposits in and near the shelter. This terrace abuts the bluff that contains the Kincaid Shelter, and some of the upper deposits within the shelter extend outward and are incorporated into the terrace material. The terrace surface extends as a broad brush-covered flat from the bluff to the present river channel, and lies about 25 feet (7.6 m) above the river bed. According to local ranchers, floods have spread across the terrace several times since 1900. These major floods have not much modified the level of the terrace surface, as there has been only a small amount of deposition or erosion since the latest aboriginal occupation in the area.

The age of the oldest part of the 25-foot terrace is not known. Archaic-period cultural materials and modern faunal remains (animal bones) are present in the upper part of the terrace in front of the shelter. Thus, the terrace reached its final development in the Holocene (modern) geological period. This terrace deposit is equivalent to the second terrace that occurs in the upper Sabinal River valley of the Edwards Plateau.

Viewed over the millennia, the land has constantly changed and continues to do so. Looking back to the time of the first peoples at Kincaid, the scene would have appeared quite different from what we see today. During the relatively cool and moist Late Pleistocene period, the Sabinal was a more constantly flowing river able to support wildlife such as alligators and aquatic turtles, as indicated by faunal material from the lower deposits of the shelter. Megafauna—mammoth and large bison—as well as camel, horse, and sloth roamed the region.

The climate appears to have experienced a relatively brief dry period sometimes called the Clovis Drought around 13,000 years ago. By 12,000 years ago the climate shifted to a moderately moist period that lasted to perhaps 9,000 years ago, followed by a prolonged period of warm and dry conditions that lasted for over 4,000 years punctuated by a a brief moist interlude sometime between 5,000 and 6,000 years ago. By about 4,000 years ago, the climate shifted back to somewhat wetter conditions similar to the modern climate.

As the climate fluctuated between dry and moist periods over time, the vegetation and animal communities shifted as well. Prehistoric hunters and gatherers, keenly attuned to the land and its changing resources, would have adapted or moved on.