My fieldwork mainly aims to increase geographic and temporal (time interval) sampling within South America. Most terrestrial mammal fossils from South America come from the southern part of the continent (particularly Argentina). Therefore, my colleagues and I have focused our efforts on other areas, such as Bolivia, Chile, and Peru. Some of these localities have also increased the temporal sampling in South America by producing fossils from time periods that were previously unrecognized or very poorly known. I mostly work at sites that are Eocene, Oligocene, or Miocene in age, which means we are finding fossils that are between about 45 and 10 million years old. We mainly collect fossils by prospecting but sometimes use other strategies as well. Most of this fieldwork was initially supported by exploratory grants from the National Geographic Society and subsequently supported by larger grants from the National Science Foundation (NSF). Our fieldwork in Chile has also been supported by that country’s equivalent of the NSF, CONICYT.
- Bolivia (southern): The Bolivian sites I investigate are middle to late Miocene in age, generally between 16 and 12 million years old. They are located in arid regions at high elevations, typically above 11,500 feet (3,500 m).
- Chile (northern): Our sites in northern Chile are early to late Miocene in age, between about 18 and 10 million years old. Most of our studies have focused on a site known as Chucal that is located in the Chilean Altiplano at more than 13,000 feet (4,000 m).
- Chile (central): We have discovered many sites in the Andes mountains to the west and southwest of Santiago. These range in age from middle Eocene (45 million years old) to early Miocene (16 million years old). The fossils are preserved in very hard rocks that represent ancient lahars (volcanic mud flows). As a result, it takes a very long time (typically two to eight weeks) to clean each specimen.
- Chile (south-central): The main site we are investigating in south-central Chile, Laguna del Laja, is situated about 250 miles (400 km) southwest of Santiago in a beautiful, mountainous area next to a recently-active volcano and a natural lake. The thick sequence of rocks preserves early to middle Miocene fossils that range from about 20 to 10 million years in age.
- Peru (eastern): Our field sites in Peru are in the eastern topical lowlands where it is warm and wet throughout the year. The fossils from this area range from in age from middle Eocene (about 41 million years old) to middle Miocene (about 12 million years old).