Steven D. Emslie, David Meltzer, and David Webster NSF Proposal #0819678
In this study, we will complete detailed systematic identification and analysis (radiocarbon, stable isotope) of vertebrate fossils recovered from Cement Creek Cave, an important late Pleistocene locality in the Upper Gunnison Basin, Colorado. Preliminary work at this site in 1998 revealed an extremely rich paleontological record with abundant vertebrate and plant remains dating from before the last Ice Age, over 45,000 years ago, to more recent periods within the past 2000 years. The fossils from this cave are quite significant: no other high-elevation site in North America has produced a near-continuous record of fossil vertebrates that date before and after the last Ice Age (that peaked at about 20,000-18,000 years ago). Analysis of fossil shrews (Sorex spp.) and other taxa recovered in the 1998 excavations, including some species no longer found in Colorado or the Upper Gunnison Basin, indicate there were significant changes in the environment surrounding the cave over time ranging from tundra to subalpine forest to mixed sagebrush steppe environments. However, radiocarbon analyses also reveal there are large gaps in the cave fossil sequence, which seemingly correlate with episodes in glacial history. Whether those gaps are real is uncertain; so too are the questions of how far back the Cement Creek record might extend, and whether a more precise ecological and climatic sequence can be derived from this rich fossil locality. Consequently, in summer 2007 we reopened the area excavated in 1998 and expanded the original 1998 test pit to 1 x 1.5 m and excavated to a depth of 2.2 m in 5-cm levels. These more extensive excavations doubled the depth of the stratigraphic profile in the cave and added thousands more vertebrate fossils to the collections. This expansion also provided a richer assemblage of fossil material for additional analyses proposed here to explore and test hypotheses on climate change and small-mammal community structure and diet in the later Pleistocene and Holocene. Here, the fossils recovered from this new excavation will be sorted and detailed identification will be completed. Analysis of remaining unidentified material from the 1998 excavation also will be completed to provide a more thorough reconstruction of vertebrate communities and environmental change in the Upper Gunnison Basin since the Wisconsin Period. This research will be conducted with the assistance of three undergraduate students at the University of North Carolina, Wilmington, and one graduate student at Southern Methodist University. These students will be involved in field and laboratory research and will develop independent studies of the cave fossils using the scientific method and hypothesis testing. The students will benefit from advanced research experiences and training, will participate in museum visits for detailed analyses of fossil specimens, and will develop their skills at scientific investigation and writing. Matching funds from SMU will be used to involve the graduate student from that institution in this research and how it applies to the paleoindian record in the Upper Gunnison Basin. Public presentations, a web site, and exhibits of data from this project will advance public understanding on the value and importance of protecting archaeological and paleontological resources. The value of cave resources also will be stressed in these presentations.
This project began in the mid 1990s and focuses on reconstruction of late Pleistocene through Holocene environments in the Upper Gunnison Basin, a montane basin surrounded by high-elevation mountain ranges located in west-central Colorado. This research is being conducted in collaboration with Dr. Mark Stiger, Western State College, Gunnison, CO, and Dr. David Meltzer, Southern Methodist University, Dallas, TX. Drs. Stiger and Meltzer are archaeologists interested in early human exploitation of and adaptation to post-glacial environments in the basin. The research funded by the National Science Foundation since 2008 has focused on reconstructing late Pleistocene and Holocene small vertebrate communities based on fossil assemblages in caves. NSF funding has supported analysis and excavations of vertebrate fossils from two high-elevation caves in the Gunnison Basin that have produced the richest and most diverse late Pleistocene mammalian faunas now known from high-elevation (3000 m, or 9500-10,000 feet) sites in North America. We applied stable isotope analysis of enamel from selected species of fossil and living mammals to investigate paleoclimatic conditions and paleotemperatures in the basin before and after the last glacial maximum (LGM) at ~18,000 years ago. We excavated and identified thousands of vertebrate fossils from these caves that date from >40,000 years old to the present and are now conducting systematic analysis of this material. The following website provides more details on these activities including taxa identified and a description of the excavations (http://people.uncw.edu/emslies/colorado.html) as well as a link to a poster on our project results. Additional research at these sites is ongoing and has included the participation of four undergraduate students and one Master's student at UNCW and four graduate students at SMU.
