Spring Lake, located on the Texas State University campus in San Marcos, Texas, boasts a rich environment and history that includes the 2nd largest natural spring system in the state (and the former home of Ralph the Swimming Pig at the Aquarena Springs Resort and Hotel.) Excavations at Spring Lake indicate that Paleo-Indians were regularly present at the springs by at least 8,000 years ago. According to history provided by Brune (2010), The Tonkawa Indians referred to the springs as Canocanayesatetlo, meaning “warm water,” and farmed the area 800 years ago. In addition he also suggests the first Europeans to discover the springs were members of the Espinoza-Olivares-Aguirre Spanish expedition of 1709, who were seeking to missionize the Tejas Indians. In the late 18th century, a Spanish mission, San Xavier, occupied the headwaters of the San Marcos River, followed by the failed settlement of San Marcos de Neve in the early 19th century (Brune 2010). Throughout the Spanish period, the springs were an important stop on the Old San Antonio Road from Mexico to Nacogdoches, and, after the Civil War, remained an equally important stop for cattle drives up the Chisholm Trail. The construction of a large spillway at the west end of Spring Lake in the 1950s formed a popular swimming pool and led to development of an amusement park that encompassed the springs. Texas State University bought the site in 1994 and, as of 2007, has worked to return the springs to a more natural state and remove most of the amusement park developments (Reeves 2008).
The Center for Archaeological Studies (CAS) has, since its founding in 2000, conducted multiple studies at the Spring Lake site, many of which include the monitoring of the removal of old park developments, as well as nearby locations at the Ice House site and the Burleson Homestead. Recently, CAS has begun plans to excavate again at Spring Lake. Part of that process is assembling an Archaeological Studies Report that includes sections such as Goals and Methods of the study, Historic Background of the site, Paleoenvironmental Reconstruction of the area, Summary of Findings, and multiple sections on the various types of artifacts found. An Archaeological Studies Report is created to summarize the research, excavations, and methodology, undertaken by the team at CAS for each project. My internship at the Center for Archaeological Studies focused on compiling a draft chapter for the Paleoenvironmental Reconstruction section of what will be the Archaeological Studies Report for the upcoming Spring Lake study. What I found during the research process reinforced something we are taught from the get go in archaeology classes: this isn’t a hard science. We are making assumptions on the archaeological record (the body of physical evidence of the past); however, these assumptions are based on very technical and scientifically tested proxies. In addition, in geology and archaeology courses, we are also taught that landscape evolves and changes over time, and the most interesting part of my research was being able to visualize a prehistoric Central Texas. I would like to use the rest of this paper to briefly discuss the geology, climate, and vegetation of the region, and how it was much different at times.
The Balcones Escarpment is geology’s most prominent mark across the state of Texas, formed by the Balcones Fault that runs approximately from Del Rio to Waco along Interstate 35. The fault zone is thought to be related to the Ouachita Mountains, formed approximately 300 million years ago during a continental collision between a primitive North America and an unknown landmass (Harrigan 1987). For eons these continents mashed into one another, leaving the area crumpled with large mountains and hills. Over time, in Texas, these mountains were eroded away and pressed downward as sediment piled on top and water dissected the limestone, forming the valleys we know and love today as the Hill Country. In addition, rainwater poured into the fractured rocks, creating the vast aquifer system beneath our feet, and discharged through the multiple springs along the Balcones Fault zone.
Our understanding of the paleoclimate of Central Texas can be largely attributed to pollen analysis, which is probably the most widely used and popular technique of environmental archaeology. The pollen grains of plants are preserved in anaerobic soil deposits; they can be extracted, identified under a microscope, and counted. The relative abundance of the various groups can be used to infer vegetation present at that time. Bousman (1998) reexamined pollen data from the Boriack and Weakly Bogs in Central Texas by first constructing a deposition rate for the bog sediments, which was used to infer the age of the strata in which specific pollen grains were found. By subsequently comparing the percentage of arboreal pollens to grass pollens, he was able to postulate whether the area was a forest, woodland, or grassland. A rise in arboreal pollen is interpreted as a cooler and moister climate at the expense of grasslands, which prosper in more arid conditions. The pollen records from Boriack Bog are shown in figure 1, and illustrate fluctuations between woodlands and grasslands over the past 10,000 years. However, theories remain open to revision and it should be noted that pollen analysis in particular is indicative of local vegetation and climate.
The climate of the Pleistocene (20,000 – 10,000 BP [years before present]) is thought to have been moister and cooler by about 5 to 6 degrees Celsius than present times. However, faunal evidence from the Edwards Plateau (Toomey et al. 1993) and speleothem analysis (think tree-ring dating on stalagmites and stalactites) from multiple caves across Central Texas (Lauritzen and Lundberg 1999) propose that severe droughts plagued the area c. 14,400 but were terminated as temperatures increased and glacial water surged south. The presence of particular species of animal from the Edward’s Plateau, specifically Hall’s Cave, can be indicators of paleoclimatic conditions, and we see the disappearance of multiple species from the archaeological record adapted to arid conditions on the plateau during this time. The Gulf, during the Pleistocene, was likely smaller and cooler, resulting in a lower number of both tropical storms as well as intense, convectional storms in the Texas interior. Precipitation was likely regular and cyclonic, carrying in moisture via jet stream from the Pacific. The Holocene (10,000 BP – present) is marked by a gradual warming trend, reduced rainfall, and increased aridity. Toomey et al. (1993) speculates that increased temperatures coupled with a stronger influence of a now larger and warmer Gulf of Mexico would have caused a majority of Central Texas precipitation to be very heavy rains during the summer months. Intense storms, previously uncommon, would have been seen regularly during these times across the region. By about 4,000 BP, climate as well as landscape reaches a contemporary balance; a grassland environment experiencing peak rainfall in late spring and early fall and periodic intense summer storms from the Gulf.
It is very interesting to know that Central Texas hasn’t always resembled the environment we live in today and that it will continue to change. As archaeology grows as a discipline, organizations such as CAS will have a prominent role in bringing prehistory and archaeology to the masses. In addition, as archaeological knowledge continues to change and grow, this coupled with new technologies will enhance any future assumptions made on the paleoenvironment or anything within the archaeological record. Similarly, as archaeologists continue to develop and utilize a holistic, multi-disciplinary approach (e.g. ethnoarchaeology, geoarchaeology, paleoethnobotany) more precise assumptions will be made.
- Bousman, C. Britt. 1998. Paleoenvironmental Change in Central Texas: The Palynological Evidence. Plains Anthropologist 42(164):201-209
- Brune, Gunnar. 2010. SAN MARCOS SPRINGS. Handbook of Texas Online. Published by the Texas State Historical Association.
- Harrigan, Stephen. 1987. Texas Primer: The Balcones Escarpment. Texas Monthly. Austin, Texas.
- Lauritzen, Stein-Erik, and Hoyce Lundberg. 1999. Speleothems and Climate: A Special Issue of The Holocene. The Holocene 9:643-64.
- Oksanen, Eric. 2011. Regional Environmental Setting: Present and Past Climates of the Blackland Prairie and Balcones Escarpment. From Archaeological Investigations at the Ice House Site, 41HY161: Early Archaic Technology, Subsistence, and Settlement along the Balcones Escarpment, Hays County, Texas. Archaeological Studies Report No. 14. Center for Archaeological Studies, Texas State University, San Marcos.
- Reeves, Kimberly. 2008. Last Goodbye to Aquarena Springs, The Austin Chronicle.