Mound-building Marajoara, the warrior chiefdom of Santarém, and the riverbank Omagua packed the Amazon várzea so thickly that Orellana's men in 1542 thought villages never ended.
The complex chiefdoms collapsed within a century of European contact as epidemics, slave raids and Jesuit aldeias depopulated the floodplain; descendant peoples survive scattered along the river.
The atlas holds 3 border frames for Amazon Floodplain Chiefdoms — the shape you scrub through changes in 900 · 1542 · 1641.
Argues for the dense, complex várzea chiefdoms — Marajoara, Santarém, Omagua — that Orellana's 1542 expedition described (broad pre-Columbian context).
Hemming's history of Amazon exploration recounts the riverbank chiefdoms and their collapse after contact.