Dahlin's work focused primarily on the bajo swamps and mapping, while Matheny's team focused primarily on excavations in the site center and architecture. This project ended in 1983. To the surprise of the archaeologists, it was found that a large amount of construction was not contemporary with the large Maya classic cities in the area, like Tikal and Uaxactun, but rather from centuries earlier in the pre-classic era (see: Mesoamerican chronology).[2]