Ernie Lundelius, Jay Banner, and Jim Samson
In 1963 a large cave was found by the Texas Highway Department while conducting foundation core drilling for a railroad overpass of Interstate Highway 35 south of Georgetown, Texas. A two foot diameter hole was drilled into the cave for access. Exploration by highway department personnel and members of the Texas Speleological Association found an extensive cavern underlying the site of the proposed overpass and surrounding area. The landowner, Dr. Laubach, received permission from the Texas Highway Department to develop a commercial cavern under the highway, and it was named Inner Space Cave. The cavern is located in the Cretaceous age Edwards Formation and within the Balcones Fault Zone, both known for having caves and sinkholes.
Cave calcite deposits (speleothems) offer insight into past climate. As the calcite grows from drip water entering the cave, it may record changes in the rate of drip and/or the chemical composition of the drip water. In this way, speleothems my preserve past climate information, yet there are many uncertainties regarding how accurately we can interpret a climate signal from speleothem analysis. At Inner Space and other cave systems in central Texas, ongoing research is monitoring cave meteorology, drip water physical and chemical parameters, and the growth of calcite on artificial substrates. The goal of these studies is to evaluate the extent to which modern speleothem calcite preserves climate changes. Speleothems have the potential to record past changes in temperature and the sources of moisture for rainfall in Texas.
Deposits in Laubach (Inner Space) Cave have produced vertebrate fossils from five separate old openings that are marked underground by debris cones. Radiocarbon (C-14) dates are available for three 23,000, 15,000 and 13,000 YBP. The fossils represent fauna that lived in Texas during the late Pleistocene and include a number of extinct species as well as extant species no longer found in central Texas. The extinct species include the scimitar toothed cat, Homotherium serum, large armadillo, Dasypus bellus, sloth Megalonyx, glyptodont Glyptotherium sp., Columbian mammoth Mammuthus columbi, camel, Camelops sp., dire wolf Canis dirus, four horned antelope Tetrameryx sp. and large javelina Platygonus compressus. The extra-limital species, Microtus ochrogaster/pinetorum, the shrew Blarina carolinenesis, prairie dog, Cynomys ludovicianus, and Dipodomys elator indicate changes in the environment since the last glacial stage. Some differences in the faunas from the five localities may indicate changes in the fauna through time. The oldest fauna contains remains of the Mexican free tailed bat that is absent from most of the Pleistocene faunas of Central Texas. The C-14 date of 23,000 YBP indicates that it was present during the last interstadial that preceded the last glacial maximum. There are old guano deposits in the cave that could be dated to determine if they are the same age as the Mexican free tailed bat specimens.
Biographical information on the Speakers:
Jay Banner: http://www.jsg.utexas.edu/researcher/jay_banner/
Ernest Lundelius: http://www.jsg.utexas.edu/researcher/ernest_lundelius/
James Samson: James is an independent geological consultant and an AGS Honorary Member.