Obsidian artifact sourcing studies performed over the last 25 years have identified obsidian from outcrops around the communities of Zinapecuaro and Ucareo, Michoacan, at sites widely distributed in time and space. Recent data indicate that Zinapecuaro and Ucareo constitute distinct obsidian sources, although their proximity to each other and their similar chemical compositions merit their consideration as collectively comprising part of an obsidian source area. Sourcing studies that used Ucareo as well as Zinapecuaro source reference samples provide strong evidence of considerably greater pre-Hispanic utilization of the Ucareo source, and raise the possibility that at least some artifacts attributed to Zinapecuaro in studies that did not use Ucareo reference samples may be from the Ucareo source. These findings are supported by recent archaeological evidence of considerably greater exploitation of the Ucareo source, including what is probably one of the largest known pre-Hispanic quarries. Preliminary data provide a tentative chronology for settlement and exploitation of the source area.

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Survey and excavation conducted by Stoner and Nichols (2019) at Altica, located in the Basin of Mexico, recovered nearly 29,000 pieces of obsidian, most of which apparently came from the nearby Otumba source. Formal classification followed by attribute analysis revealed a number of distinct lithic industries represented in the collection, although most are represented by finished objects that do not appear to have been produced on site. Most of the material consists of flakes probably used as unmodified, informal tools and produced on expedient cores consisting of some nodules but mostly percussion blades, spent cores, and other artifacts recycled as secondary cores. I propose that Altica acquired its obsidian from workshops possibly located in an area where they apparently existed in later times and may have during the Early–Middle Formative, as well. Virtually all of the obsidian in the collection appears to have been used for domestic or subsistence activities and was not involved in production or exchange systems believed to have existed at that time. Two unusual caches containing macronodules provide some evidence to the contrary, suggesting that Altica may have been a transshipment center.

The site of Tula, Hidalgo, Mexico, is well known for its distinctive architecture and sculpture that came to light in excavations initiated some 70 years ago. Less well known is the extensive corpus of archaeological research conducted over the past several decades, revealing a city that at its height covered an area of c. 16 km 2 and incorporated a remarkably diverse landscape of hills, plains, alluvial valleys, and marsh. Its dense, urban character is evident in excavations at over 22 localities that uncovered complex arrangements of residential compounds whose nondurable architecture left relatively few surface traces. Evidence of craft production includes lithic and ceramic production loci in specific sectors of the ancient city. Tula possessed a large and densely settled hinterland that apparently encompassed the surrounding region, including most of the Basin of Mexico, and its area of direct influence appears to have extended to the north as far as San Luís Potosí. Tula is believed to have originated as the center of a regional state that consolidated various Coyotlatelco polities and probably remnants of a previous Teotihuacancontrolled settlement system. Its pre-Aztec history exhibits notable continuity in settlement, ceramics, and monumental art and architecture. The nature of the subsequent Aztec occupation supports ethnohistorical and other archaeological evidence that Tula's ruins were what the Aztecs called Tollan.

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