El Colorín de Jecota

As of this writing (2026), the most recent obsidian source recorded in the Southwest is the El Colorín de Jecota source near the bend of the Rio Sonora in central Sonora. The composition was originally discovered in a large obsidian provenance project in northern and central Sonora with no known provenance and named “Río Sonora Unknown” (Shackley 2024). It was dominant in the archaeological contexts in the region at 44% (n=141) of the total analyzed. Eventually contacts with local ranchers in the valley near the bend of the Río Sonora led Bill Doolittle and Matt Pailes to a Sr. Julio Noriega who led them to a dome complex that ultimately solved the unknown (Carpenter et al. 2024:6; Shackley et al. 2024). The source is a typical Neogene rhyolite dome approximately 150 m in diameter(see image below). The marekanites are embedded in a perlite matrix characteristic for obsidian in the Neogene Southwest. The largest nodule collected was 34.2 mm in diameter also typical of Neogene sources, and larger than any artifact produced from this source so far. The obsidian is opaque black except in very thin flakes, and bipolar reduction of the marekanites is easily performed, although some of the nodules “explode” on impact like Los Vidrios (Lomas de Norte) and Antelope Creek East at Mule Creek. The obsidian pressure flakes well. Secondary deposits of this source are not extensive and inspection of the nearby arroyo found only about several hundred meters of secondary deposition (Matt Pailes, personal communication 2024). El Colorín de Jecota, like so many Neogene sources, is a local source not likely exchanged any great distance from the source, and least as seen in recent studies (see Carpenter et al. 2024:Table 2).

Location of El Colorín de Jecota obsidian source in Sonora and other obsidian sources in Chihuahua and Sonora

Top (arrow) geological setting of the El Colorín de Jecota obsidian source – note ashy/perlitic lava in foreground: bottom left a marekanite in the ash matrix; bottom right nearby secondary deposits of marekanites (black dots) among perlitic lava (image by Matt Pailes).

El Colorin de Jecota
	N	Minimum	Maximum	Mean	Std. Deviation
Ti	25	931	1.202	1053.6	73.7
Mn	25	285	395	357.5	27.5
Fe	25	7.314	8.306	7753.7	267.6
Zn	25	33	74	42.5	9.0
Rb	25	132	160	144.9	7.1
Sr	25	73	86	79.3	3.6
Y	25	12	20	16.5	2.0
Zr	25	95	109	102.3	3.7
Nb	25	11	22	15.8	3.3
Ba	25	588	725	633.4	35.9
Pb	25	21	29	25.5	2.5
Th	25	8	25	17.4	4.4

References

Carpenter, J.P., G.M. Sánchez, M.S. Shackley, W.E. Doolittle, J.A. López-Rivera, and M. Pailes 2024, Obsidian circulation in the Sierra Madre Occidental of northern México: new source identification and analysis of procurement patterns. Journal of Archaeological Science: Reports 57:104615.

Shackley, M.S. 2024, Obsidian sources and source provenance of archaeological obsidian in northern Sonora: the known and unknown. In Kiva Special Issue: H. Claypatch and E. Villalpando Canchola (Eds.) Reframing and Expanding Sonoran Archaeology, Kiva 90:293-305.

M. S. Shackley, M. Pailes, and G. Sánchez, 2024, Composición elementa para El Colorín (Antes Rio Sonora Desconocido): Una fuente de obsidiana recién descubierta cerca de Maxocahui, Sonora. In Carpenter, J., M. Pailes, G. Sánchez, J.A. López, K. Worthey, P.A. Estrada, J.K. Feathers, and M.S. Shackley: Informe de la sexta temporada del Proyecto Sahuaripa y la ladera oeste de la Sierra Madre: actividades realizada en el trabajo de investgacion de campo Quiriego, Mazocahui, Fronteras y Análisis de los materiales de las temporadas 2021-2022, 2022-2023, Zooarqueología y resultados de las dataciones por C14 y luiniscencia, characterización de la Obsidiana. Report for the Director of Archaeology, National Institute of Archaeology and History, México City, México.