Hey johny, finally I have below the result of my searching for East south America's civilizations.
As far as I understand it, Sambaquis are not a people but a cultural phenomenon of fisher tribes who had theses things called Sambaquis, which were at the same time a place for cooking, burials and shelter, and could get so big as to be considered small wonders. I could be wrong though as I'm basing that on what I found in my limited research. In tupi sambaqui is samba (shellfish) + ki (heap).
But one important bit is that they were most probably not done by the tupi-guarani, since they are dated between 8k and 2k years ago. They are most likely from the Humaitá.
So let's get to the meat. The most important tribes have an asterisk (*).
*Humaitá - circa 7300 years ago, while other source says 6600 y.a.
Umbu - c. 6700 y.a.
Ananatuba - c. 3500 up until 2500 y.a.
Jê - c. 3000 y.a.
*Marajoara - c. 1800 y.a. - between 2000 and 1000 more generally they were at their best, but they started developing from hunter-gatherers to ceramists around 5000 y.a. so that could be used too. They probably had contact with more developed civilizations due to the Marajó island being up there almost in central america, from whom they'd have learned ceramics and agriculture.
Itararé - c. 1500 y.a.
*Tupi-guarani - c. 1500 y.a.
Kuhikugu - c. 1500 up until 400 y.a. - an Amazon civilation which built villages and big cities, and were not harmed by the early colonialists for being deep into the forest
Santarém is a region, their most predominant tribe being Tapajós, we could use that instead. But I don't have precise info on their timeframe, still they could be used for colonial era and a bit before that. Though the ceramics from Tapajós are legendary and dated as early as 7000 y.a., an american arquelogist named Anna Roosevelt disputes that they were work of Tapajós, rather being from an earlier culture (we could call it all Tapajós surely enough, though).
Although I haven't found much info on them, I took a liking for the Mbaya-Guaicurus, which after contact with europeans assimilated fully the horse and offered perhaps the biggest resistance deep into brazilian territory. They raided not only rival tribes but colonial settlements, and were for a long time thought 'invincible'. Classically portrayed as side-riding their horses, so the enemy would mistake their approach for a band of wild horses (not sure that'd work out so well but it's romantic
). See link for picture.
http://www.overmundo.com.br/overblog/os-guaicuru-os-indios-cavaleiros-ainda-vivem
http://www.ajbonito.com.br/index.php?idcanal=235
May be a fun resistance option to offer at the dawn of colonization, 1500-1600 a.d.
Tupi-guarani definitely take after Humaitá.
Also Vieira and Taquara existed between Humaitá and Tupi-guarani, thus I'd put them in the 6000-2000 years ago timewindow, if they're needed.
Though tupi and guarani are different cultures and are indeed the most known brazilian indigenous cultures, they are almost always treated as a single entity historically, bundling together actual hundreds of cultures over the last couple thousand years.
Please let me know if the tribes and civilizations above are enough, or if it's lacking a specific time frame or era.
I'm posting my sources below, so when it's time to develop the unique tech trees I can refer to these links for that kind of information.
http://www.historiamais.com/primeiroshabitantes.htm
http://www.paraty.tur.br/historia/povosprehistoricos.php
http://pt.wikipedia.org/wiki/Sambaqui
http://www.itaucultural.org.br/arqueologia/pt/tempo/marajoara/index.html
http://pt.wikipedia.org/wiki/História_pré-colonial_do_Brasil
http://basilio.fundaj.gov.br/pesqui...on=com_content&view=article&id=675&Itemid=188
