Lost Oasis Cave Preserve

Preserve Manager: Drew Thompson


by William Russell, March 2003

The entrance to this cave was discovered in early 1985 by surveyors staking the roadway for the proposed northern extension of Lost Oasis Hollow. Their survey line crossed a bush-covered hole at the edge of a shallow sink. The small hole, two feet long, one foot wide, and less than two feet deep, might have been ignored except for the strong current of air that blew from it. Espy Huston and Associates later conducted resistivity surveys across the sink, and their results indicated an area of low resistivity trending NE-SW towards two other karst features: Greenbrier Sink and Dead Tree Sink.

In March 1985, Bill Russell enlarged the entrance with a sledgehammer and was able to squeeze along a low bedding plane passage for six feet to where it dropped abruptly into one corner of a room 35 feet wide and 40 feet long. This room is up to eight feet high and is almost divided in two by a mass of flowstone and a row of formations. The southeastern half of the room is larger and has few formations. Along the southeast wall, a crack between breakdown and the wall was excavated to a depth of eight feet, where cracks continued into breakdown, but no large passage or airflow was found. The NW half of the room is lower, from 3 to 6 feet high, and is floored with flowstone over breakdown. Digging in this area following airflow led to a small lower room with a six-foot pit at one side. The air came from a four-inch hole at the bottom of the pit. This hole was enlarged, but led into a porous solution zone composed of clay-covered nodules that were roughly one foot in diameter and surrounded by interconnecting voids. This appears to be the same solution zone exposed in nearby Sand Burr and Greenbrier caves.

The cave, being shallow but damp, contains a rich biota. Two species of cave-adapted millipedes were observed, as well as a species of blind Rhadine beetle, and several types of spiders. Much organic matter enters the cave from a now-filled entrance along the east wall of the room. A cone of black dirt and small rocks extends into the room from this old entrance. The cave is developed along a series of NE-SW trending fractures that concentrated solution. Initially, a room was dissolved at the solution zone level. Then this room was extended upward by collapse and further solution. This left the present cave floored with large breakdown blocks resting on unconsolidated clay and solution remnants. Air flows from beneath the breakdown near the north edge of the cave and from holes along the south wall of the cave. This air flow might indicate favorable localities to dig for new cave, or the air might be coming from a large area of solution rubble and fill with no large open space.

Years later, the original plans for the subdivision were abandoned during the real estate slump, and the new developer, not knowing what to do with the feature, donated the cave and some surrounding land to the Texas Cave Management Association in January 1993.

The cave was visited by Kate Walker and her UT Biology class (about 5 students), accompanied by Bill Russell and Jean Krejca on the cool wet morning of March 2, 2003. The cave was cool and damp following a long period of cold, wet weather. However, various cave critters were present, though not as numerous as in the spring. No Rhadine beetles were seen, but Speodesmus millipedes were present. Some crickets were concentrated on the ceiling near the entrance, approximately 200, which was less than the large number normally emerging from the entrance in the summer. The cool temperature had likely reduced the number of animals active on the cave floor, but more study is needed to confirm this.

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