Typological analysis of the Archaic and later projectile point components from the Sonoran Desert sites of El Fin del Mundo and El Gramal, Northwest Mexico

Ismael Sánchez-Morales
Arizona Museum of Natural History

The Archaic period of Northwest Mexico spans from approximately ~10,000 yr BP to ~4,500 yr BP, encompassing the longest interval of human settlement in the region. However, despite its long duration, it remains the least studied cultural period in Sonora, where most research into pre-sedentary human occupations has focused on the Paleoindian (~13,400 yr BP to 10,000 yr BP) and Early Agricultural (EAP) periods (~4,100 yr BP to 2,000 yr BP) (e.g. Sanchez 2001; Gaines et al. 2009; Carpenter et al. 2015; Sanchez 2016; Holliday et al. 2024). Over the last 25 years, new research programs, CRM projects, and the reevaluation of old archaeological collections have produced new information that documents the significance of Archaic adaptations in the area (e.g. Carpenter et al. 2003; Ochoa D’Aynes 2004; Sánchez-Morales 2012, 2025; Carpenter et al. 2017). Building upon these previous efforts, with the support of a grant from the Arizona Archaeological and Historical Society, in May of 2025 I conducted a typological analysis of Holocene projectile points collected from surface contexts at the Sonoran Desert sites of El Fin del Mundo and El Gramal. Both sites are best known for their record of Clovis occupations (Gaines et al. 2009; Sanchez et al. 2014; Sanchez 2016; Sánchez-Morales 2018; Sánchez-Morales et al. 2022; Holliday et al. 2024). However, their records of Holocene settlements are just as significant but have not been the center of recent research and have only been published in a very limited manner (e.g. Carpenter et al. 2017). Therefore, the present study aims at taking the first step towards developing a post-Clovis occupational sequence for these sites through typological classification of temporally diagnostic materials. Here I report an update on this study.

El Fin del Mundo (FdM) is situated 100 km NW of the city of Hermosillo in a remote, eroded landscape, covering 3 km² within the basin of the Rio Bacoachi (Figure 1). Investigations at this site began in 2007, led by Guadalupe Sanchez (INAH) and Vance Holliday (University of Arizona). The site preserved a megafuna kill feature (Locus 1) consisting of a buried bonebed containing skeletal elements of two gomphotheres (Cuvieronius sp.) associated with Clovis points and lithic debris (Sanchez et al. 2014). This is the only Clovis buried context yet discovered south of the United States and the only human-gomphothere association known from North America (Sanchez et al. 2014; Holliday et al. 2024). Other localities to the south contain scatters of archaeological materials on the surface. Many of these areas produced diagnostic Clovis artifacts indicative of a campsite and lithic workshops of terminal Pleistocene temporality (Sánchez-Morales 2018, 2024; Sánchez-Morales et al. 2022). However, a large assemblage of projectile points of later typologies was also recovered from these contexts (Sánchez-Morales 2012). Test excavations in these localities did not reveal buried archaeological deposits.

Meanwhile, El Gramal is located approximately 60 km southwest of Hermosillo and about 110 km south of FdM, within the basin of the Rio Sonora (Figure 1). This site contains a scatter of archaeological materials on the surface covering 10 km². Unlike FdM, El Gramal has been surveyed for decades by avocational archaeologists who have collected hundreds of projectile points, including some of Paleoindian affiliation (Gaines et al. 2009). Systematic investigations at this site were conducted by G. Sanchez and her team in 2007 and 2016. Multiple projectile points of Holocene typologies were recovered during the latter field season. No buried contexts were located during test excavations. 

The lithic collections from FdM and El Gramal are curated at the laboratory of the project led by G. Sanchez in Hermosillo. Given the surface nature of the Holocene assemblages from both sites, we use temporally diagnostic artifacts (e.g. projectile points) to better understand their occupational histories. Typological, metric, and qualitative data (e.g. raw material and condition) were collected from 111 artifacts from FdM and 84 from El Gramal. These materials include all projectile points and point preforms determined to be part of the Archaic, EAP, and Late Prehistoric components from both sites (Table 1). All points were recovered from surface contexts during systematic surveys that I directed between 2010 and 2020 in the case of FdM, and in 2016 in El Gramal. These materials had not been studied previously beyond general counts for technical reports. The new information from FdM was combined with previously collected data from Holocene projectile points recovered in 2007 and 2008 (Sánchez-Morales 2012), resulting in a total sample of 232 artifacts from this site. Typological classifications were based on Justice 2002a, 2002b, and Sliva 1997, 2015. Temporal classification of artifacts other than finished projectile points, whenever possible, was based on morphology (Sliva 1997; Ochoa D’Aynés 2004). Those that lack any diagnostic features for their typological classification or that were not matched with known types from the Southwest and neighboring regions were, in most cases, considered indeterminate.

The collection from FdM contains point types representative of occupations ranging from the Middle Archaic to the EAP (Figure 2). Middle Archaic artifacts include relatively abundant Pinto and San Jose points and single examples of the Chiricahua and Humboldt types. Late Archaic types include Cortaro and rare Elko points. The EAP component is the largest and includes Empire, abundant San Pedro, and Cienega points. The EAP component from FdM also includes one crudely made cruciform, a type of artifact reported from EAP contexts in the Tucson Basin (e.g. Adams 2005). It is not clear if FdM contains an Early Archaic component. We have identified four damaged points characterized by their relatively large size, concave bases, acute projecting shoulders, and fine craftmanship, which we have grouped as the Placencia type. These points are unlike any published point types from Sonora and Arizona, but they resemble the Early/Middle Archaic Borax Lake and Bajada types, best known from California/Nevada and the Colorado Plateau respectively (Justice 2000a, 2000b). Thus, we speculate that they may represent an Early Archaic occupation at FdM. Lastly, there are 48 indeterminate points, which include unidentifiable fragments (n= 27), not identified points (n= 19), and point preforms (n= 2).       

At El Gramal we observed a high incidence of fragmentary and damaged points, which made typological identifications for nearly half (43 percent) of the collection not possible. However, the 48 points that were classified into types represent occupations ranging from the Middle Archaic to the Late Prehistoric period (Figure 3). The Middle Archaic component includes Pinto, San Jose, Chiricahua, and Gypsum points, the latter type overlapping with the Late Archaic. As in the case of FdM, the EAP component is the largest at El Gramal and includes Empire and San Pedro points, which are the most abundant. One Placencia point, like those from FdM, was also identified. Unlike FdM, El Gramal contains a Late Prehistoric component, represented by small (x̄= 16 mm max length) triangular points with concave bases, similar to some Classic Hohokam arrow heads from Northern Sonora and Southern Arizona (Sliva 1997). 

The preliminary analysis of raw materials suggests that locally available stone was predominantly used at both sites. At FdM, both the Archaic and EAP components are dominated by white quartz and rhyolite, which are abundant in and around the site. Interestingly, quartz, a challenging material to work into finely retouched artifacts, was almost exclusively used to manufacture the Middle Archaic Pinto and San Jose points. This is in stark contrast to the Clovis points from FdM, which were primarily made on multiple varieties of exogenous chert (Sánchez-Morales 2024). At El Gramal, rhyodacite dominates throughout. Obsidian is also common in the Archaic and Later Prehistoric components, and it is lowest during the EAP when it seems to have been replaced by a more intense use of local basalt. It is not certain where the obsidian was procured, but sources of this rock are known in Cerro Izabal near Hermosillo, and in the Sierra Libre and Sierra El Aguaje, around 60 km away (Vidal et al. 2020).  

Thus far, the results of this study indicate that FdM and El Gramal contain an important record of Archaic and later occupations, in the case of El Gramal well into Late Prehistoric times. Both sites were repeatedly occupied by groups of foragers and early farmers over thousands of years, from the terminal Pleistocene to the Late Holocene. Both contain Middle and Late Archaic components; it is not clear, however, if the Early Archaic is represented in the studied materials. We speculate that the Placencia points may fill this gap. In both sites the EAP components are the largest, even though the Archaic period encompasses a much longer time span. This suggests either more intense occupations (i.e. longer stays/more occupation episodes) or larger groups using these sites during the EAP. Perhaps their locations near sources of usable stone made them attractive to human groups. The changes through time in the representations of raw materials may indicate adaptative responses to changing environmental conditions. Of particular interest is the strikingly predominant use of quartz at FdM during the Middle Archaic, a period often associated with drier and warmer conditions in Northwest Mexico and the American Southwest (Antevs 1955). The almost exclusive use of this hyperlocal resource to manufacture Pinto and San Jose points at this site may reflect patterns of tethered mobility (Taylor 1964) as a response to more challenging conditions and a patchier distribution of resources in the Sonoran Desert. 

The next steps of this study include a more detailed analysis of raw material provisioning patterns, including obsidian sourcing analyses, as well as the documentation of private archaeological collections from El Gramal and other localities in the region known to contain Archaic and later materials. This pilot study confirms that the Archaic archaeological record of the Mexican Sonoran Desert warrants further examination and that surface collections, despite their limitations, provide a first approach towards understanding the pre-sedentary occupational sequence of this region. 

Acknowledgements

I would like to thank Centro INAH Sonora for granting access to the archaeological collections and to Guadalupe Sanchez for graciously providing space to carry out this study. This research was possible with the support of the Arizona Archaeological and Historical Society.    

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Table 1. Frequencies (N) and representations (%) of the projectile point types identified in El Fin del Mundo and El Gramal.

Figure 1. Location of selected Archaic and Early Agricultural Period sites in Sonora and Southern Arizona. Map by Matthew Pailes (University of Oklahoma) and Ismael Sánchez-Morales.  

Figure 2. Selected projectile points from El Fin del Mundo: a, Placencia; b, Pinto; c, San Jose; d, Humboldt; e, Chiricahua; f, Cortaro; g, Elko corner notched; h, Empire; i, cruciform; j, San Pedro; k, Cienega long (left and center) and Cienega short (right).

Figure 3. Selected projectile points from El Gramal: a, Placencia; b, Pinto; c, San Jose; d, Chiricahua; e, Gypsum; f, Empire; g, San Pedro; h, concave base triangular.