I am currently working on creating a 3D model of the tornado damage paths and surrounding destruction left behind by the May 11, 1970 tornadoes in Lubbock, Texas. These tornadoes were extremely powerful, and it lead to Tetsuya Theodore (Ted) Fujita developing the F-Scale. The Lubbock tornado was rated as an F-5.
Stance Hurst, Field Manager, Lubbock Lake Landmark
The focus of the first six weeks of the 2019 field season was excavation at Macy Locality 126 — a Protohistoric-age (1450-1650) site. Volunteers from Texas, Oklahoma, and California joined the Landmark research team. Notable among the volunteers was a returning member after 47 years who first worked with Dr. Eileen Johnson during her second season of excavation at the Lubbock Lake Landmark in 1973 (Figure 1).
Macy Locality 126 was located on a terrace overlooking the South Fork of the Double Mountain Fork of the Brazos River within the Post research area. Previous surveys and excavation at Macy Locality 126 took place between 2008-2012 and 2018. The focus of this work was on the southern section of the locality that was more heavily eroded.
This locality was a regularly used campsite location. Multiple hearths were found and excavated in the previous field seasons. Two hearths superimposed on top of each other were found, indicating the same hearth was used numerous times in different years. Stone tools recovered surrounding the hearth features indicated they were being used for processing animal remains. Also, stone tool manufacturing debris suggested the manufacture of new stone tools and maintenance of transported stone tools occurred at the site.
Hunter-gatherers at this locality were regular traders with Puebloan agricultural peoples of the Southwest and possibly the Caddoan people of East Texas. Southwest trade items included obsidian flaked stone, Apache Micaceous and El Paso Brownware ceramic sherds, and a turquoise bead. The turquoise bead was a disk shape typical for aboriginal beads originating in the Southwest. The Apache micaceous sherds originated from the Taos/northeastern New Mexico area. El Paso Brownware had its center of production in the El Paso area. Obsidian often was gathered from gravel deposits along New Mexico’s Rio Grande River. Ceramic sherds with fingernail impressions suggested these hunter-gatherers also may have been trading with Caddoan people of East Texas. Further work, however, would be needed to confirm the source of these pottery sherds.
Excavation of a new area at Macy Locality 126, located north of the previous work, was the focus of the 2019 field season. In 2018, a survey revealed a new hearth feature and associated stone tool material that had eroded out of the terrace edge. Results of this further excavation showed that the occupations at Macy Locality 126 were much more extensive than previously thought.
Excavation of the new eroding hearth and surrounding areas has revealed numerous stone tools and associated manufacturing debris. Several large Apache micaceous ceramic sherds (Figure 2) have been found. The excavation of these new additional units indicates that the occupations at Macy Locality 126 extend much farther to the north of the site. The objects within the northern portion of the locality are more buried than at the southern part of the site. This observation is because it indicates much more is to be discovered at Macy Locality 126 than previously realized. The Landmark team currently is planning for additional excavations at Macy Locality 126 for next summer.
Over the past three field seasons at the Post research area, the survey team has recorded the skeletal remains of several extinct Ice Age animals within the Spring Creek beds. The Spring Creek beds are lake sediments left from an extinct lake that had formed during the Pleistocene. During this time, under more moist weather conditions, several paleolake basins formed along the eastern escarpment edge of the Southern High Plains. The exact age of the Spring Creek beds and their relation to other regional extinct paleolakes has puzzled researchers for several decades.
The Blanco basin, located in Crosbyton County, Texas is the largest known paleolake of the region. This basin has been the center of early Pleistocene animal research for over a century, and also is the only one dated. A volcanic ash layer is located within lake deposits of the Blanco basin, and another upper ash layer occurs above the lake sediments within the later wind-blown sediments of the Blackwater Draw Formation.
Throughout the Pleistocene (~2.6 mya-11,000 ka), sporadic eruptions from volcanoes in the Jemez Mountains region of north-central New Mexico and Yellowstone National Park in Wyoming blanketed the Great Plains. Where these ash lenses were preserved from erosion, they provided a reliable chronological marker for determining the age of sedimentation.
In the early 1970s, researchers dated two samples of the Blackwater Draw Formation ash layer, above the Blanco lake bed, and the estimated ages of these samples were 1.4 and 1.77 million years ago. This ash layer was identified as the Guaje ash that has its source in the Jemez Mountains in New Mexico. The lower ash layer within the Blanco paleo-lake sediments was dated to 2.8 million years ago. If these ages are correct, then the Blanco paleolake sediments date between ~2.8 – 1.4 million years ago.
At the Post research area, the Landmark team has discovered a thick deposit of volcanic ash located on an upland ridge. The research team currently is tracing the lateral extinct of the ash layer and mapping the Spring Creek lake basin using a drone.
During the 2019 field season, Landmark crew member collected samples from ash beds for ³⁹Ar/⁴⁰Ar dating at the Oregon State Geochronology lab (Figure 1). This Argon dating method now is regarded as the most reliable for determining the age of volcanic ash layers. Results of this work will help to narrow down the age of the Spring Creek beds and their relationship to other Southern High Plains paleolakes.
The Landmark team also is collecting ash samples from the Blanco basin to double check the ages of the 1970s results. Geologists at the time used fission-track dating, and some researchers have questioned these age determinations. Results of redating the Blanco ash layers and ascertaining the age of the ash found in the Spring Creek beds will help to refine the known ages of extinct Southern High Plains paleolakes and the extensive extinct animal remains within them.