In the early 1970s, Carlos started archaeological fieldwork at Guayabo de Turrialba, a large archaeological site representing the remains of a Pre-Columbian village. He also wrote about the collection of indigenous gold objects at the Pre-Columbian Gold Museum in San José. He also contributed to the study of cultural sequences in the Central Area of Costa Rica. In 1974, he published research on zoomorphic monoliths at Guayabo de Turrialba and began fieldwork at the site of El Monito. He published two articles about his research on the archaeology of the Arenal Volcano Area; one in 1977 in National Geographic Society Research Reports over Tephrastratigraphy and Cultural Sequences and one in 1984 in Annals of the Academy of Geography and History of Costa Rica.