Cerros de Trinchera was built on the side of a high hill with a central plaza, and walls in the shape of a snail shell spiral. The shell ornaments produced there were worked from 2,800 BC to 1400 AD. INAH and the University of Binghamton researchers have found seven kilograms of sea shells there worked into rings and bracelets with geometric motifs.

The La Playa site had 10,000 years of occupation. Shell ornamentation began there at 850 BCE-200 CE. This jewelry has not been found in burials in the area, so they were trade items sent to people further north and west. They worked shells into hoops worn as bracelets, which were worn by individuals all over northwest Mexico and the Southwestern US. The shell jewelry was exchanged for Paquime pottery and pottery from Arizona and New Mexico.

INAH has the report here (in Spanish) with a beautiful slide show of the jewelry. (Click on the tiny camera icon above the article to see the slide show,)
http://www.inah.gob.mx/en/boletines/6466-brazaletes-de-conchas-daninas-dan-identidad-a-los-pueblos-de-deierto-de-sonora

Mike Ruggeri’s Aztlan World
http://mikeruggerisaztlanworld.tumblr.com