The Solimoes Formation is situated in the Acre Basin, a sedimentary basin formed by Andean tectonic events that occurred along the west margin of South America in the
Neogene. It is traditionally dated to the
Late Miocene by biostratigraphy and zircon geochronology. The formation is mostly consists of mudstones, siltstones and muddy sandstones,deposited under fluvio-lacustrine settings. == Paleofauna ==