A geochemical baseline for clays of the Toluca Valley, Mexico

Journal of Archaeological Science: Reports 29 (2020) 102094

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A geochemical baseline for clays of the Toluca Valley, Mexico a,⁎

Angela C. Huster , Daniel E. Pierce a b

T

b

School of Human Evolution and Social Change, Arizona State University, 541 979-3078, United States Archaeometry Laboratory, University of Missouri Research Reactor, 573 882-4257, United States

A R T I C LE I N FO

A B S T R A C T

Keywords: INAA Clay sampling Mesoamerica Toluca Valley

This paper presents the results of the INAA of 28 geological clay samples from the Toluca Valley (Upper Lerma) in the State of Mexico, Mexico and the immediately adjacent areas to the north, west, and south. While preliminary, these results demonstrate that there are internal elemental clines within the Toluca Valley, based on elevation (Na, K) and latitude (Cr), among other patterns. These samples also demonstrate that the underlying geology of the Toluca Valley can be systematically differentiated from that of the adjacent Basin of Mexico based on higher Ba and lower K concentrations. This study confirms the results of prior analyses of archaeological ceramics from the Toluca Valley, and provides new avenues for dividing the region into multiple sub-regional source areas in future archaeological analyses.

1. Introduction This paper presents a general description of the chemical variability of clays within the Toluca Valley (Upper Lerma) of Central Mexico, based on Instrumental Neutron Activation Analysis (INAA) of 28 clay samples from across the region (Fig. 1). These samples include 23 samples from within the Toluca Valley, and 5 samples from adjacent areas to the north, west, and south. The samples from the Toluca Valley proper cover approximately 2000 square kilometers, resulting in a sample density of one sample per 87 square kilometers. We acknowledge that this is a relatively low sample density and that our results should be interpreted at a corresponding level of precision. Nonetheless, it is important to take the limited information we do have regarding the soil chemistry of the Toluca Valley to begin to develop an understanding of the range of compositional variation for the purposes of identifying provenance of ancient ceramics. The Toluca Valley region formed an important part of the Teotihuacan and Aztec states, likely providing agricultural goods to support populations in the Basin of Mexico but has been relatively understudied archaeologically. The current analysis has two goals: identifying elements that vary spatially within the Toluca Valley, and identifying elements that serve as reliable markers to differentiate the Toluca Valley as a whole from adjacent areas. These baselines will improve the geographic source identification of archaeological ceramics from neighboring regions, as well as allowing for the establishment of multiple sub-regional source groups within the Toluca Valley. While ceramic sourcing has had a long history in Central Mexico, studies have overwhelmingly focused on both clays

⁎

and archaeological samples from core areas, such as the Basin of Mexico and the Valley of Oaxaca. This perpetuates the apparent primacy of these areas, since ceramics imported from many adjacent areas will either appear as unknown outliers in chemical analyses, or be lumped into core groups because the degree within group variation relative to between group variation is unknown. 1.1. Background Reference samples of clays and other geological materials form important comparative datasets for chemical and petrographic analyses of archaeological ceramics (Cordell et al., 2017). Intensive sampling within a region can be used to determine whether elemental variability is relatively discrete or continuous across the landscape, and which elements are the most geographically variable (Minc and Sherman, 2011). It is not necessarily assumed that the sampled clays represent the specific raw material source locations used by ancient potters (Neff et al., 1992); a single clay stratum may be accessible at multiple points on a landscape, or multiple clay deposits formed from the same parent material in a region may have similar compositional signatures. Pottery also rarely directly matches raw clays in a region. Due to either cleaning processes that remove some components of raw clays, such as levigation, and/or tempering practices that add additional material to clays to make them appropriate for making vessels, the chemical composition of finished pottery is rarely identical to that of the parent clay (Arnold et al., 1991). Such practices may also vary over time, creating differences in the ceramic composition of ceramics from the same area in

Corresponding author. E-mail addresses: [email protected] (A.C. Huster), [email protected] (D.E. Pierce).

https://doi.org/10.1016/j.jasrep.2019.102094 Received 22 May 2019; Received in revised form 5 November 2019; Accepted 11 November 2019 2352-409X/ © 2019 Elsevier Ltd. All rights reserved.

Journal of Archaeological Science: Reports 29 (2020) 102094

A.C. Huster and D.E. Pierce

Fig. 1. Sample locations and selected archaeological sites in the Toluca Valley.

sedimentary breccias and igneous andesites and volcaniclastics. The Nevado de Toluca is an andesitic- dacitic stratovolcano which sits on three intersecting fault systems (García-Palomo et al., 2002). The Nevado de Toluca has had at least three major eruptions; a Vulcanian eruption around 28 ka BP and two Plinian eruptions that left significant ash layers over most of the Toluca Valley and into the Basin of Mexico, known as the Upper (~10.5 ka BP) and Lower (~24.5 ka BP) Toluca Pumices (Arce et al., 2003; Bloomfield and Valastro, 1974, 1977). Lahar flows associated with the Upper Toluca eruption extend from the summit to the modern valley floor along drainages. Both the Nevado and various volcanoes within the Chichinautzin field have produced other, smaller tephra layers which cover more limited portions of the southern valley (Newton and Metcalfe, 1999). The valley forms the headwaters of the Lerma River, which runs from south to north, historically forming a series of shallow lakes or marshy areas in the center of the valley. Today, it can be formally described as the southern half of Mexico’s Hydrological Region 12, consisting of five and a half hydrological basins (a narrow drainage in northeast, a large one covering the southeastern half of the valley, two draining the Nevado de Toluca in the south-western valley, one covering the western wing of the valley and one covering the northern quarter of the basin as well as areas of the adjacent Ixtlahuaca region). Due to differences in geological, cultural, and hydrological boundaries, three of the “Toluca Valley” samples from the western end of the sample area (#s ACH-587, 588, and 589) technically fall outside of the greater Lerma watershed, as do the three external reference samples from the west and south. The two external refence samples from the north represent a continuation of the Lerma watershed, as it continues north through the Ixtlahuaca Valley. Analyses of sediment cores from lakes at the southern end of the valley and paleosols from the Nevado de Toluca demonstrate that temperature and precipitation have fluctuated over the past 25,000 years, with associated shifts in vegetation and sediment loads. Broadly, the Late Pleistocene was characterized by grasslands under cooler conditions and a relatively stable water table. It was followed by the appearance of denser forests with the warmer conditions with more variable precipitation characteristic of the Holocene. (Caballero et al., 2002; Lozano-García et al., 2005; Sedov et al., 2003). This may have affected patterns of sediment mixing in

different time periods (Stoner, 2016). In Central Highland Mexico, studies of the chemical and mineralogical properties of clays have formed an important component in the compositional analysis of archaeological ceramics (BranstetterHardesty, 1978; Cohen, 2016; Minc and Sherman, 2011; Pollard et al., 2005; Tenorio et al., 2005). Studies range from including a few local clay samples with a larger set of archaeological samples, to large-scale clay sampling across entire regions. Studies on the former end of the range usually focus on positive source confirmation; that is, if archaeological samples match local clays, this provides additional support for hypothesizing that the samples are local. Larger regional sets of clay samples still allow for this type of positive matching, but they also provide grounds for stronger statements concerning whether types are non-local; that is, that they fall outside the elemental ranges that could reasonably result from the sampled clays, even accounting for a reasonable degree of tempering. 1.2. The Toluca Valley The Toluca Valley is located immediately west of the Basin of Mexico, covering approximately 2700 square kilometers. For the purposes of this study, the region is bounded on the east by the Sierra de los Cruces (which separates it from the Basin of Mexico), to the south by the Sierra Nahutlaca-Matlazinca, to the southwest and west by the Nevado de Toluca and San Antonio volcanos, and to the north by the low transitional hills into the Ixtlahuaca Valley. The region is part of the Central Mexican Transvolcanic Axis. The underlying geology of the Toluca Valley (Fig. 2) consists of a ring of mountains and hills of Upper Tertiary and Quaternary extrusive igneous composition surrounding a valley floor of primarily quaternary alluvial and lacustrine sedimentation derived from volcanics (INEGI, 2001). The mountains surrounding the valley are generally older to the north, consisting of Upper Tertiary basalts to the northwest and Upper Tertiary andesites to the northeast. To the southeast, Upper Tertiary andesites are intermixed with Quaternary basalts and basic tuffs, with the more recent materials produced by the Chichinautzin Volcanic Field. The southwest portion of the edge of the valley is dominated by the Nevado de Toluca volcano, consisting of a mix of Upper Tertiary 2

Journal of Archaeological Science: Reports 29 (2020) 102094

A.C. Huster and D.E. Pierce

Fig. 2. Sample locations relative to regional geology.

alluvial areas of the valley floor, as well as human settlement patterns and the associated use of specific clay deposits. Archaeologically, the Toluca Valley has been a buffer zone between Central and West Mexican groups through much of prehistory, with cultural and economic ties in both directions (Huster, 2016; Kabata, 2010; Sugiura Yamamoto et al., 2015, 2013). There was a first peak of settlement during the Formative, including ties to other parts of Central Mexico and the broader Olmec cultural sphere (González de la Vara, 2011, Stoner and Nichols, 2019). The area was then largely depopulated and then resettled by groups with strong ties to Teotihuacan; this parallels the general concentration of population into Teotihuacan in the Basin of Mexico. Classic period ceramic types in the Toluca Valley include variants of both types characteristically produced at Teotihuacan, and other regional tradewares, such as local imitations of ThinOrange (Kabata, 2010; Ramírez Sánchez, 2012; Sugiura Yamamoto et al., 2013). The Classic period population of the region saw a sharp increase during the Epiclassic and an increasingly hierarchical settlement pattern, suggesting that the region absorbed refugee populations leaving Teotihuacan (Sugiura Yamamoto, 2005a). Throughout the Teotihuacan and Epiclassic periods, the region’s lithic assemblages have relatively high frequencies of Ucareo obsidian, demonstrating ongoing ties to West Mexico (Benitez, 2006, Sugiura Yamamoto et al., 2018). The region is characterized by a widespread presence of Coyotlatelco ceramics in the Epiclassic (Sugiura Yamamoto, 2013). Subsequently, the local ceramic tradition diverges from broader Central Mexican trends in the Early Postclassic, moving toward a distinct regional style that continued through the Spanish conquest. The Middle and Late Postclassic also saw the development of regional ceramic spheres within the valley, which might be linked to the various ethnic groups in the region at the time of Spanish conquest (Sugiura Yamamoto, 2005b). Further west, near the Ucareo obsidian source, in Michoacán, there are a handful of intrusive sites (known as Cumbres sites), which have material culture very similar to what is seen in the Early-Middle Postclassic Toluca Valley (Hernández and Healan, 2008), and the valley does have

much higher frequencies of West Mexican obsidian than most contemporaneous Central Mexican areas (Golitko and Feinman, 2015; Huster, 2016). The region came under the direct control of the Triple Alliance (Aztec Empire) around 1470 CE, though economic interaction with the Basin had been increasing for 50 years prior to military conquest. Middle and Late Postclassic ceramic exchange demonstrates ties to both the Basin of Mexico and areas to the south, but little interaction across the Tarascan border (Huster, 2018). Current archaeological work has focused largely on the Classic-Epiclassic transition (Sugiura Yamamoto, 2009; Sugiura, Pérez and Zepeda, 2017), and Middle-Late Postclassic changes related to the Aztec conquest of the region (Smith et al., 2009, 2013). Within the Toluca Valley, samples of archaeological ceramics have previously been analyzed via INAA from the Formative site of Ojo de Agua (Stoner and Nichols, 2019), the Epiclassic sites of Santa Cruz Atizapán and San Mateo Atenco (Stoner and Glascock, 2011; Sugiura Yamamoto and Nieto Hernández, 2006; Sugiura Yamamoto, 2009), and from the Postclassic sites of Calixtlahuaca (Huster, 2016) and Tlacotepec (McVicker et al., 2003). An additional project analyzed ceramics and clays from San Miguel Ixtapan (Tenorio et al., 2005), located southwest of the Toluca Valley, approximately halfway between the south and west peripheral samples (Samples 591/592 and 586, respectively) in the present study, using both INAA and other methods. These studies have generally been successful in differentiating between locally produced ceramics and those imported from other regions, such as the Basin of Mexico. However, despite differences in ceramic composition among studied sites, geographically-meaningful subdivisions among local samples have remained elusive. It has been unknown whether this difficulty in subdividing the broad “local” groups at individual Toluca Valley sites was due to underlying geological issues, such as an unusual degree of homogeneity in regional clays, or due to a relative lack of trade within the valley. More broadly, past analyses of archaeological ceramics from the Toluca Valley have shown that such samples have unusually high levels of Ba and Sr and relatively low

3

Journal of Archaeological Science: Reports 29 (2020) 102094

A.C. Huster and D.E. Pierce

Table 1 Sample locations and preliminary group assignments. ANID

Local Subregion

Site/Town name

Lat.

Long.

Prelim. group

ACH571 ACH572 ACH573 ACH574 ACH575 ACH576 ACH577 ACH578 ACH579 ACH580 ACH581 ACH582 ACH583 ACH584 ACH585 ACH586 ACH587 ACH588 ACH589 ACH590 ACH591 ACH592 ACH593 ACH594 ACH595 ACH596 ACH597 ACH598

Toluca Valley Toluca Valley Toluca Valley Toluca Valley Toluca Valley Toluca Valley Toluca Valley Toluca Valley Toluca Valley Toluca Valley Toluca Valley Ixtlahuaca Valley Ixtlahuaca Valley Toluca Valley Toluca Valley Valle de Bravo Toluca Valley Toluca Valley Toluca Valley Toluca Valley Malinalco-Tenancingo Malinalco-Tenancingo Toluca Valley Toluca Valley Toluca Valley Toluca Valley Toluca Valley Toluca Valley

Calixtlahuaca (1) Teotenango (Tenango de Arista) Calimaya Metepec San Mateo Atenco Ocoyoacac Atarasquillo Tlamimilolpan Jiquipilco el Viejo Villa Seca Santa Cruz Tepexpan Santa Ana Ixtlahuaca San Antonio Bonixi Santa Catarina Tabernillas Almoloya de Juarez La Peña (Valle de Bravo) Pueblo Nuevo Amanalco Villa Victoria Los Berros Cieniguillas de Guadalupe Acatzingo (Tenancingo) Malinalco San Miguel de Ocampo Santiago Tilapa Calixtlahuaca (2) Dilatada Tlacotepec Zinacantapec

19.3320 19.1113 19.1751 19.2498 19.2542 19.2747 19.3236 19.3927 19.5146 19.4006 19.5673 19.5890 19.4807 19.4907 19.3630 19.2020 19.2932 19.4377 19.3940 19.3941 18.9178 18.9488 19.1007 19.1941 19.3336 19.2946 19.2279 19.2820

−99.6931 −99.5984 −99.6323 −99.6031 −99.5237 −99.4594 −99.4547 −99.4797 −99.5808 −99.6307 −99.7020 −99.8983 −99.7282 −99.8690 −99.7572 −100.1425 −100.0292 −100.0024 −100.0463 −99.8437 −99.5853 −99.4765 −99.5361 −99.4126 −99.6906 −99.9030 −99.6750 −99.7602

West West West West Rio Lerma East East East East Rio Lerma East West Rio Lerma West West Far West Far West Far West Far West West South South Rio Lerma East West Far West West West

modern construction or fill. Clay samples were taken by cleaning an exposed profile with a freshly washed trowel and then filling a quart ziplock bag. GPS coordinates and a brief description of the collection site were recorded. At the Calixtlahuaca Archaeological Project (CAP) lab at the Colegio Mexiquense in Zinacantepec Mexico, texture and wet and dry Munsell colors were recorded for each sample. Samples were air-dried, and a small (5–10 g) subsample was repackaged for submission to MURR for INAA. The remainder of each sample was stored at the CAP lab for future analyses.

levels of rare earth elements relative to the better-studied, adjacent Basin of Mexico, through it is uncertain whether these patterns are due to the composition of the clay, temper, or both (Stoner and Glascock, 2013a). 2. Methods 2.1. Field sample collection Clay samples were collected between August 7th and 16th, 2017, spanning the Toluca Valley and immediately adjacent areas (See Fig. 1 for a map of sample locations). Twenty-three samples were taken within the Toluca Valley, while five were in immediately adjacent regions to the north (Samples 581 and 582), west (Sample 596), and south (Samples 591 and 592) in order to provide limits to the observed patterns in these directions (Table 1). The area to the east, the Basin of Mexico, is already well-represented in the University of Missouri Research Reactor (MURR) database and thus did not require additional sampling. The samples cover all of the major geological formations within the Toluca Valley. Soil profiles in the foothills and small freestanding hills on the valley floor tend to be homogenous, with O-A-B-C horizons ending in decaying volcanic ash (locally referred to as tepetate); in these cases samples were taken from the bottom of the B horizon. Samples were collected from modern exposures of clayey soils, including roadcuts, modern construction, and streambanks. For approximately half of the samples, there were visible archaeological artifacts in the surrounding area. For the remaining half, prior survey records (Sugiura Yamamoto, 2000, 2005b) indicate that there were Postclassic sites within a few miles of the collection point, though the specific site location was not relocated. In several cases, the collection point was currently being used for quarrying material for modern cinderblock production. The upper elevation limits of sample collection were chosen based on a combination of reduced archaeological site densities at higher elevations, and a desire to maintain are reasonable degree of similarity to the primarily valley-floor samples used to characterize the Basin of Mexico. The central alluvial valley floor is under-sampled due to the difficulty of finding areas that were not under

2.2. Lab analysis methods At MURR, the clay samples were prepared into test tiles and fired at 700° C. Two analytical specimens were then removed from each source tile and ground into a fine powder. Portions of approximately 150 mg of powder were weighed into clean high-density polyethylene vials to be used for short irradiations, while 200 mg was weighed into clean highpurity quartz vials used for long irradiations. Along with the unknown samples, standards made from National Institute of Standards and Technology (NIST) certified standard reference materials of SRM-1633a (coal fly ash) and SRM-688 (basalt rock) were prepared in the same way, as were quality control samples (e.g., standards treated as unknowns) of SRM-278 (obsidian rock) and Ohio Red Clay (a standard developed for in-house applications). The full preparation procedures are described in greater detail in Cogswell et al. (1996). The sample ANIDs are ACH-571 to 598. Neutron activation analysis was conducted according to MURR protocol (Glascock, 1992), consistent with most other NAA laboratories (Neff, 1992, 2000). This analysis consisted of two irradiations and a total of three gamma counts. The first irradiation was carried out through a pneumatic tube system in which samples were irradiated for only five seconds by a neutron flux of 8 × 1013 n cm−2 s−1. This short 720-second count yields gamma spectra containing peaks for nine short-lived elements: aluminum (Al), barium (Ba), calcium (Ca), dysprosium (Dy), potassium (K), manganese (Mn), sodium (Na), titanium (Ti), and vanadium (V). Similarly, the larger 200 mg sample was subjected to a 24–hour irradiation at a neutron flux of 4

Journal of Archaeological Science: Reports 29 (2020) 102094

A.C. Huster and D.E. Pierce

Table 2 NAA elemental concentrations. ANID

As

La

Lu

Nd

Sm

U

Yb

Ce

Co

ACH571 ACH572 ACH573 ACH574 ACH575 ACH576 ACH577 ACH578 ACH579 ACH580 ACH581 ACH582 ACH583 ACH584 ACH585 ACH586 ACH587 ACH588 ACH589 ACH590 ACH591 ACH592 ACH593 ACH594 ACH595 ACH596 ACH597 ACH598

0.0000 0.0000 0.0000 1.9885 0.0000 0.0000 0.0000 0.0000 4.8955 2.3744 0.0000 0.0000 0.0000 4.6694 3.8956 39.3955 3.1939 4.3498 7.2745 2.8633 2.8834 0.0000 6.1108 0.0000 4.1171 0.0000 6.3833 0.0000

22.5610 20.1057 20.0572 25.5785 13.8236 28.0895 18.6349 26.2701 18.3041 18.3000 17.0049 27.9675 18.7555 23.6397 29.7934 10.1695 15.9888 19.7771 34.4250 19.9440 21.4694 19.4007 31.9969 14.6883 32.3200 42.6445 31.8825 13.7800

0.3314 0.2599 0.2345 0.3399 0.2342 0.3115 0.3071 0.2577 0.3116 0.2728 0.2352 0.3994 0.2443 0.3258 0.3701 0.3468 0.3034 0.2701 0.4945 0.3069 0.2494 0.2859 0.3349 0.3539 0.4163 0.5185 0.4191 0.1784

24.0826 25.3878 22.0172 27.1845 14.7003 31.4006 21.5124 26.6668 19.6833 20.3396 16.1579 31.7843 19.6325 28.0014 30.4751 10.6719 18.6078 18.3848 36.2744 21.4268 21.0668 23.7846 32.7914 22.7508 35.5989 48.9756 35.1369 14.2837

5.1339 4.9378 4.9420 5.7114 3.4692 6.8137 4.6220 5.3502 5.0259 4.6894 3.7897 6.4207 4.4068 6.0190 7.1568 2.6399 4.3901 4.4766 7.9349 4.9184 5.2391 5.3556 6.7384 6.0689 7.9430 10.2232 7.5741 3.6672

1.1910 1.8100 1.8093 1.6397 1.3171 2.0552 3.2867 1.5254 3.3683 1.8089 3.1059 1.2825 2.1424 2.6375 1.3875 1.8430 2.9327 3.5824 3.8813 1.1429 2.4843 1.5942 2.6622 1.7292 1.8324 2.2002 2.2085 1.9576

2.1100 1.6753 1.7317 2.2958 1.1464 2.2246 1.8843 1.6380 2.0295 1.7136 1.5471 2.4306 1.6237 2.1485 2.4881 2.2630 1.9556 1.6654 2.9990 2.0808 1.6960 2.2471 2.1848 2.3448 2.8473 3.6581 2.6473 1.3561

46.1214 44.2648 42.4317 51.5058 28.6737 61.6747 44.2156 52.5569 67.1442 38.6445 38.2343 65.8315 35.2826 80.2219 26.5481 22.5719 34.4843 90.9069 72.8671 39.9328 77.6741 47.0756 72.8985 51.3771 74.3639 67.2218 70.2049 27.9572

15.3360 14.9821 15.1344 20.8909 10.4646 15.9234 19.3119 14.8613 15.7338 14.0016 14.4542 33.1123 9.3521 28.2426 7.5467 14.5435 33.5207 30.9111 23.1453 19.2557 25.1020 66.1955 21.3062 70.6818 24.7695 21.0411 24.5278 13.9974

ANID

Cr

Cs

Eu

Fe

Hf

Ni

Rb

Sb

Sc

ACH571 ACH572 ACH573 ACH574 ACH575 ACH576 ACH577 ACH578 ACH579 ACH580 ACH581 ACH582 ACH583 ACH584 ACH585 ACH586 ACH587 ACH588 ACH589 ACH590 ACH591 ACH592 ACH593 ACH594 ACH595 ACH596 ACH597 ACH598

90.2889 86.3013 92.3456 166.5140 58.5568 62.4719 102.7155 38.8729 53.1628 69.3360 45.5373 267.2393 39.8100 89.6195 115.9190 49.0539 174.3813 154.5316 124.1169 41.9064 578.6887 655.5367 117.1651 812.7938 72.6305 97.7381 138.0378 70.4552

1.5550 1.9848 1.9200 3.0973 1.8790 0.4415 3.7571 1.8977 5.0427 2.7339 4.6145 1.8865 2.6978 4.5935 3.4640 3.8823 3.8816 4.4680 3.9431 2.0607 1.3364 3.0143 3.5381 0.3263 3.7240 2.6550 4.1773 2.0420

1.5407 1.4678 1.4302 1.5874 1.1484 2.0557 1.1310 1.5700 1.2909 1.3066 1.0445 1.8644 1.2799 1.6467 1.9278 0.6835 1.2765 1.0138 2.1484 1.3579 1.3921 1.5798 1.8236 1.8177 1.9998 2.9157 2.0485 1.3407

38357.7 40304.8 38161.3 48517.3 30486.6 52604.6 53365.3 43679.9 56561.7 39236.9 29298.4 60509.0 27506.0 57809.4 44699.9 54256.3 76938.7 84967.9 63480.8 54027.5 87348.0 88785.5 52975.1 95782.8 42137.4 63202.8 57313.6 34609.6

4.7051 5.0675 4.8501 5.8196 3.6189 6.5760 7.3808 5.4371 8.4419 4.9833 5.7077 6.4332 4.8951 8.3639 6.2503 3.8950 8.5844 12.8189 8.2959 4.4675 8.4958 7.2301 7.7074 5.8310 5.9029 7.6103 6.8387 3.8205

25.89 59.05 34.83 57.09 0.00 0.00 0.00 0.00 0.00 19.94 0.00 84.88 0.00 0.00 41.01 0.00 40.84 51.73 0.00 0.00 132.05 131.24 35.91 180.39 47.08 32.44 0.00 0.00

25.61 29.46 28.74 47.23 36.05 15.50 59.43 22.08 55.32 36.21 61.64 25.48 53.93 45.26 44.11 69.71 32.20 43.47 29.51 30.17 7.12 24.88 42.48 13.92 37.72 20.20 46.78 35.26

0.1817 0.2323 0.2716 0.4598 6.3979 0.1517 0.3913 0.2003 0.6547 0.4024 0.3452 0.3327 0.1322 0.3799 0.3607 2.6252 0.5893 0.6794 0.5563 0.2890 0.3904 0.2606 0.4976 0.4343 0.3724 0.3621 0.6239 0.1565

13.2166 13.4722 13.1651 16.8141 9.7848 17.2372 16.4812 12.6706 17.4579 13.0102 9.2707 23.6628 10.0531 18.1339 15.4494 22.3599 24.4753 23.2136 22.1047 13.5652 31.7858 26.1559 16.6245 39.6914 13.5697 19.0490 20.8641 11.9926

ANID

Sr

Ta

Tb

Th

Zn

Zr

Al

Ba

Ca

ACH571 ACH572 ACH573 ACH574 ACH575 ACH576 ACH577 ACH578 ACH579 ACH580 ACH581 ACH582

590.96 506.09 603.89 276.36 629.24 389.16 161.30 652.68 0.00 455.15 329.73 137.81

0.5205 0.5284 0.5011 0.7068 0.3670 0.6677 0.7390 0.5403 1.0087 0.5467 0.6993 0.5612

0.7229 0.6161 0.5648 0.7605 0.4336 0.8048 0.5712 0.6761 0.6812 0.6676 0.4482 0.7021

4.8230 4.5210 4.1901 6.6315 2.8872 5.7281 6.9689 6.0471 9.3053 4.2041 7.0072 5.1105

78.61 74.88 75.88 92.58 91.65 105.32 86.01 73.27 72.78 111.36 55.35 87.77

84.11 114.04 111.72 148.49 94.19 144.23 156.65 141.61 217.45 104.09 122.72 133.77

106922.3 103185.6 86110.8 106162.2 78798.0 129912.7 116365.9 110637.3 145538.3 87470.9 91261.8 132459.8

1099.4 460.5 537.0 382.7 423.6 566.7 747.8 995.9 370.7 449.6 476.0 436.8

32617.6 23350.7 26944.1 18547.8 31989.9 25857.9 9176.3 28738.5 1718.3 22584.4 18871.7 8356.3

(continued on next page) 5

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Table 2 (continued) ANID

Sr

Ta

Tb

Th

Zn

Zr

Al

Ba

Ca

ACH583 ACH584 ACH585 ACH586 ACH587 ACH588 ACH589 ACH590 ACH591 ACH592 ACH593 ACH594 ACH595 ACH596 ACH597 ACH598

749.22 166.33 280.16 125.58 126.85 0.00 198.88 584.08 61.19 202.49 488.21 0.00 331.24 351.74 361.45 572.52

0.4145 1.0433 0.7927 0.3660 0.7112 1.0851 0.9952 0.4661 0.7417 0.6576 0.7919 0.3957 0.8099 0.7485 0.7915 0.4234

0.5699 0.7661 1.2583 0.4291 0.6407 0.3759 1.0499 0.6964 0.4720 0.5815 0.7568 0.7877 1.0228 1.2270 0.9253 0.4734

4.7888 8.6550 6.9139 3.6357 5.7924 11.3580 9.0395 4.5562 6.8956 5.6323 7.2439 3.3653 8.0315 7.5087 7.7797 3.0452

71.15 81.56 75.14 126.63 95.31 113.11 118.55 80.97 75.66 93.67 84.07 84.34 81.68 99.00 91.49 67.62

125.40 199.42 137.93 70.33 168.35 276.34 181.47 149.93 175.93 201.31 215.94 152.16 158.28 197.46 180.59 99.91

94718.3 119639.5 135684.4 107871.9 170255.7 171479.9 175382.3 124783.5 196070.5 141401.4 147982.3 172292.8 139990.5 177731.2 149972.8 100279.2

447.1 525.1 388.8 232.9 391.7 369.3 497.9 1361.3 410.2 711.3 562.5 509.1 493.3 877.6 808.3 335.9

30260.8 9796.1 14516.7 3738.7 7674.4 2614.5 15517.9 29514.3 1280.7 4608.4 22872.3 4165.4 20447.9 16180.0 23992.4 30317.0

ANID

Dy

K

Mn

Na

Ti

V

ACH571 ACH572 ACH573 ACH574 ACH575 ACH576 ACH577 ACH578 ACH579 ACH580 ACH581 ACH582 ACH583 ACH584 ACH585 ACH586 ACH587 ACH588 ACH589 ACH590 ACH591 ACH592 ACH593 ACH594 ACH595 ACH596 ACH597 ACH598

3.6925 3.5945 3.1974 4.0308 2.3292 4.7472 3.1671 3.4926 3.4782 3.4119 2.6003 4.4290 3.1865 4.6194 5.6307 2.8658 3.4801 2.7267 6.3127 4.2035 3.6091 3.8591 4.7322 4.6482 5.6293 8.1087 4.9929 2.4660

5571.6 8447.1 10242.2 6511.3 11466.5 4206.1 11748.8 4323.0 4177.6 6054.0 13832.2 0.0 9476.7 7620.9 4597.5 16558.2 5139.1 4825.4 3389.6 4590.5 1153.9 12609.8 8946.0 0.0 13775.4 4190.4 4263.2 10234.9

703.74 689.79 682.69 846.97 1002.40 923.52 535.67 781.35 399.68 772.90 633.36 856.74 493.02 1062.25 286.89 327.54 401.72 1233.82 927.20 1020.03 421.19 1135.28 1254.11 1592.45 1725.27 755.65 963.78 899.97

24010.1 17865.7 20754.5 13214.8 25092.6 15514.0 10411.3 22080.8 1605.8 17457.0 18583.0 3098.7 25503.5 7764.9 10902.7 360.1 5463.7 1752.1 7435.1 21165.1 325.0 9303.9 19018.0 875.5 14009.4 10069.6 17228.6 24472.4

4011.1 5342.5 4678.0 5749.2 3624.9 6680.3 7015.1 4543.6 7385.1 5062.3 3893.1 6738.6 3667.7 9458.5 5974.8 5295.2 12264.5 13205.6 8743.0 6214.0 9743.0 11175.0 7632.7 8553.2 5362.7 8889.3 6743.2 4764.5

77.94 100.34 84.21 100.20 62.10 82.01 132.53 75.23 148.87 104.42 73.32 89.27 64.98 158.83 110.01 187.95 278.18 270.30 181.03 135.73 97.10 234.89 146.07 171.64 122.53 201.85 134.57 136.01

5 × 1013 n cm−2 s−1. After this longer irradiation, samples were allowed to decay for seven days, and were subsequently counted for 1800 s (the “middle count”) on a high-resolution germanium detector. This middle count yields data in regards to seven elements with medium half-life isotopes, namely arsenic (As), lanthanum (La), lutetium (Lu), neodymium (Nd), samarium (Sm), uranium (U), and ytterbium (Yb). Finally, after an additional four-week decay period, a final count of 8500 s was carried out on each sample. The latter measurement yielded the remaining 17 elements with long half-life isotopes available through Ceramic NAA: cerium (Ce), cobalt (Co), chromium (Cr), cesium (Cs), europium (Eu), iron (Fe), hafnium (Hf), nickel (Ni), rubidium (Rb), antimony (Sb), scandium (Sc), strontium (Sr), tantalum (Ta), terbium (Tb), thorium (Th), zinc (Zn), and zirconium (Zr). The concentrations of each of these elements were then tabulated in parts per million for interpretation. Statistical analysis was carried out on base-10 logarithms and/or linear concentrations for the purposes of normalization of trace elements. Nonetheless, Arsenic (As) and Nickel (Ni) were removed from the compositional dataset due to their high frequencies of missing values (Table 2)

2.3. Data analysis methods Clays and ceramics from Central Mexico can be more difficult to chemically analyze than those from other regions of Mesoamerica due to their common origin from the erosional runoff of the same parent rock (Parsons et al., 1982; Sanders et al., 1979). In the well-studied Basin of Mexico, compositional variation in sediments is often subtle at best, particularly near the lake where minerals weathered from rocks will settle (Stoner and Glascock, 2013a). Considered individually, clays collected from adjacent locales can be quite different compositionally, while less proximal clays may appear similar. However, when samples are considered regionally and in aggregate, general trends can be identified (Neff and Glascock, 2000; Nichols et al., 2002; Stoner, 2016). In this way, differences in the raw materials used to manufacture pottery can at times be identified. It is therefore critical to characterize any specimen as part of a larger sample rather than in isolation. To achieve this characterization with the current samples, we have used a variety of analytical methods. These can generally be grouped into three stages of analysis: comparisons among the current samples based on pre-assigned provisional geographic clusters, calculations of continuous variation across the region using the current samples, and comparisons between the Toluca Valley and adjacent regions, using

6

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A.C. Huster and D.E. Pierce

Fig. 3. Spatial locations of samples by assigned provisional group.

patterns of continuous elemental variation. Likewise, we find it useful to also consider finer scale compositional variation of clay sediments beyond the five arbitrary geographic groups discussed above for the Toluca Valley. After establishing a basic understanding of the compositional structure of the sample through the above analyses, we then turned to the prospective general trends concerning the chemistry of individual specimens to identify valley-wide spatial patterns within the Toluca Valley. In doing so, not only have we attempted to characterize the region broadly, but we were then also able to compare the revealed compositional trends to those already identified within the Basin of Mexico (Stoner, 2016, Fig. 6) to better identify key differences between the two sides of the Sierra de las Cruces. Though initial calculations of Pearson’s correlation r-values and subsequent independent sampled t-tests revealed correlations between specific elemental concentrations and northing and/or easting information for each sample (Table 4), an analysis such as this restricts our understanding of spatial trends to strictly cardinal directions. Rather, spatial trends are not limited to such rigid structure. In recognition of this concern, we plotted each sample in ArcMap 10.3.1. We then used the concentrations (ppm) of each element to interpolate a map of compositional values across space throughout the valley. To accomplish this, we utilized a universal Kriging method of interpolation. This Gaussian process utilizes covariances to weight distance from a cell to a known point value (Papritz and Stein, 1999). The influence of each known value upon the cell is inversely correlated the distance from the cell. This method differs from the Inverse Distance Weighted method in that interpolated values are also dependent upon the spatial relation of the known points. This provides a new surface raster in which hotspots are minimized and more gradualistic clinal patterns can be observed. Due to the wide dispersal of our samples, we have set a limit of 12 points at no more than 10 km away to inform all interpolated cell values. In cases where less points are found within the 10 km radius, fewer known points were allowed to influence the interpolation. These settings prevent the interpolation from being erroneously influenced by the composition of clay samples from great distances away. Overall, this interpolation resulted in the creation of a valley-wide choropleth raster for each recorded element. While this method does work under the inevitable assumption of gradualism in projecting hypothetical elemental values between sample points, we have limited the effect of punctuated anomalies through the inclusion of values for multiple collected clay sediments weighted by proximity to each unknown cell.

both the current samples and the previously analyzed clay samples in the larger MURR reference database. Using the 31 recorded elements, we first performed a hierarchical cluster analysis to determine compositional relatedness for the 28 clay samples. This analysis log transformed the compositional data, weighting each element equally. The overall similarity of each sample is then quantifiably expressed through multivariate Euclidean distance. Relatedness is then visualized through a dendrogram in which branch lengths represent relative similarity between specimens. Per the provenance postulate (Weigand et al., 1977:24) the sourcing of items such as pottery is possible due to the fact that samples from the raw material source will be more compositionally similar to each other than specimens from farther away. As such, samples within the same general area, are expected to be more similar to each other than those collected elsewhere. To identify spatial patterns, we separated the samples into five locational groups (Table 1, Fig. 3); Along the Rio Lerma, East of Rio Lerma, West of Rio Lerma, Southern Deposits, and the Far West Deposits. These groups were selected based upon the proximity to the Rio Lerma, given the relationship between elevation, drainage, and soil chemistry. If spatial patterns exist between clays, one would expect cluster analyses to reveal compositional grouping of proximal samples. Principal Component analyses and coefficient of variation calculations for the assemblage were then also calculated to identify specific elements for which variation is highest throughout the region (Table 3). Finally, using the five aforementioned locational groups, elemental biplots were visually assessed to identify clusters of proximal samples to better understand which elements may have spatial trends. These analyses allowed us to identify compositional differences in clays from one portion of the Toluca Valley to another. In the past, the determination of geographical provenances of Central Mexican archaeological samples has been accomplished in part through the demonstration of subtle chemical patterns across the landscape (Nichols et al., 2002, Neff and Glascock, 2000; Stoner and Glascock, 2013a,b). Much of this analysis has been rooted in the comparison of thousands of archaeological samples and relied heavily upon the criterion of abundance (Bishop et al., 1982), and much less so upon the comparison to raw clay deposit data. At the same time, these analyses have been largely restricted to the Basin of Mexico, east of the Toluca Valley. Some studies have included raw clay samples in large numbers, however (e.g. Stoner, 2016). In these studies, researchers had some success in attributing source at the sub-regional level using 7

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Table 3 Elemental Loadings for the pottery sample on Principal Component Axes 1 through 6.* Element

Mean

PC1

PC2

PC3

PC4

PC5

PC6

Na Al K Ca Sc Ti V Cr Mn Fe Co Zn Rb Sr Zr Sb Cs Ba La Ce Nd Sm Eu Tb Dy Yb Lu Hf Ta Th U % variance: Eigenvalues:

8328.1095 125463.1755 6578.9177 12805.5323 16.9552 6446.7387 123.2446 106.3239 759.6502 51281.6466 19.8570 85.9101 32.8515 313.3056 145.4394 0.4058 2.4871 523.0977 21.6391 49.2854 23.6964 5.3429 1.5008 0.6705 3.8742 2.0325 0.3095 6.1642 0.6340 5.7895 2.0374

−0.6399 0.0945 −0.1144 −0.4785 0.1674 0.1424 0.1295 0.2956 −0.0367 0.1522 0.1640 0.0337 −0.0837 −0.2697 0.0693 0.1296 −0.0135 −0.0788 −0.0262 0.0685 −0.0169 0.0023 −0.0190 −0.0226 0.0149 0.0336 0.0319 0.0907 0.0520 0.0528 0.0647 44.96% 0.657523

−0.2272 −0.1119 0.2229 −0.1094 −0.0998 −0.1235 −0.0402 −0.3144 −0.1821 −0.1143 −0.2011 0.0036 0.2517 −0.0142 −0.1400 0.4161 0.1930 −0.1893 −0.2061 −0.1995 −0.2333 −0.2055 −0.2100 −0.1668 −0.1773 −0.1110 −0.0835 −0.1041 −0.0986 −0.1005 0.0153 17.87% 0.261422

0.1634 0.0683 0.0056 −0.0622 −0.0287 0.1240 0.1808 −0.2110 −0.0261 0.0222 −0.0228 0.0293 0.3139 −0.1053 0.1890 0.1310 0.5972 0.0008 0.1550 0.1491 0.1169 0.0949 0.0354 0.0973 0.0929 0.0976 0.1073 0.1786 0.2683 0.3017 0.2130 11.27% 0.164873

−0.2062 0.0123 −0.3948 −0.1449 −0.0825 −0.0715 −0.1774 −0.3720 −0.3846 −0.0809 −0.3422 −0.0863 −0.0941 −0.0395 −0.0153 −0.5246 −0.0147 −0.0139 0.0515 0.0165 −0.0039 −0.0015 −0.0202 0.0103 −0.0048 −0.0292 −0.0560 0.0409 0.0689 0.1153 0.0797 6.88% 0.100647

−0.1681 0.0559 −0.3418 0.2126 0.0197 −0.0709 −0.1228 −0.2096 −0.0311 −0.0092 −0.2190 0.1044 −0.1577 0.0277 −0.0574 0.6047 −0.1707 0.0440 0.1759 0.0484 0.1647 0.1510 0.1481 0.2094 0.1952 0.1256 0.1914 −0.0566 −0.0170 −0.0055 −0.1166 5.40% 0.079024

−0.0365 0.0252 −0.1790 −0.1679 −0.0638 0.0666 0.0153 −0.3231 0.4085 0.0436 0.0914 −0.0012 −0.1043 0.4545 0.2108 0.1365 −0.1821 0.1208 −0.0658 0.3125 −0.0982 −0.0697 −0.0898 −0.2216 −0.1640 −0.1813 −0.1460 0.1190 0.0720 0.1078 0.1834 3.35% 0.04893

*Values in bold explain the greatest amount of variation within each component. Those in italics explain a significant portion of the variation, but less than those in bold.

their proximity. However, in many ways these samples differ greatly and appear unrelated compositionally. In fact, they are less similar to each other than they are to more distant specimens. This nevertheless demonstrates that great compositional variability can occur within a small geographical space within the Toluca Valley despite overall spatial trends. Yet, this variability can be further addressed through other analytical methods. These results, though limited in scope, necessitate a further exploration of the aforementioned variation. Principal component analyses were conducted using log transformed data and based on the covariance matrix. Results describe the nature of the overall variation within the sample. Overall, the first six principal components explain approximately 90% of the variability of the sample. Among these PC’s, Sr, Na, Sb, Cr, Ca, and K explain the greatest amount of variation across the sample of clays (Fig. 5; Table 3). Next, determining the coefficient of variation (CV), or relative standard deviation, for each element can also be useful in the quantification of elemental variation across space and in the identification of which elements are more proportionately homogenous (Table 5). This statistic shows not only which elements are the most variable, but just how proportionally variable they are. Of the six elements identified as highly variable in the above principal component analysis, all feature a CV of at least 0.6. Of these, Sb and Cr are the most variable, each with a CV of greater than 1.2. A closer examination of the specimens in isolation reveals further information which may explain this variability. Notably, the elements that are more variable (e.g. higher CV) are generally similar in the specimens from Calixtlahuaca. This suggests that the high variability of these elements is spatially related and may be indicative of which elements may be geospatially diagnostic for the entire assemblage. In other words, while the distribution of certain elements appears randomly distributed across space, other elements are clearly part of wider trends which may be

While it is unknown just how precise these estimates are, the interpolated values closest to true collection points are the most reliable in reflecting likely values. Ultimately, these results allowed us to then assess the landscape to visualize compositional trends on multiple axes concurrently. Finally, the interpolated rasters were compared to those created for the greater Basin of Mexico to identify common trends and divergences. 3. Results and discussion As well as the general characterization of Toluca Valley clays, this study addresses two more focused research questions. First, are there systematic variations in elemental concentrations within the Toluca Valley which may serve as guidelines for future chemical sub-groups within the region? Second, are there elemental signatures which are characteristic of the Toluca Valley as a whole which can be used to distinguish between the Toluca Valley and adjacent regions, particularly the Basin of Mexico? 3.1. Region-wide compositional variation Considering all recorded elements, with the exceptions of Ni and As due to missing values, cluster analyses suggest some compositional groupings based upon the five preliminary geographic areas (Fig. 4). As such, there do appear to be some similarities among specimens from broad divisions of the region. Therefore, compositional relatedness has been revealed to be at least somewhat associated with relative proximity for the samples. Nonetheless, important differences can be observed within a small geographical space. For example, two specimens were collected from the site of Calixtlahuaca (ACH571 and ACH595). One would expect these two clays to have similar chemistries due to 8

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east and south are removed from consideration, indicating that the observed variation is not being driven by a few unusual samples from peripheral areas. The identification of these peripheral samples as distinctive from the Toluca Valley proper is discussed further at the end of this section. The six highly variable elements can be grouped into three pairs, each of which shows related patterning. First, K and Na, for example, show distinct spatial trends, with samples located inside the Toluca Valley diverging from those taken outside of it and on the margins at higher elevations. Potassium, for example, is particularly variable (CV = 0.61). With it, we see that the high levels of variation are primarily driven by four specific clays collected peripherally on the margins of the Toluca Valley. The one specimen collected at La Peña, outside of the Rio Lerma watershed to the west, features significantly higher levels of K. By contrast, the most northern, southern, and eastern specimens all feature distinctly low levels (below detection limits in two cases) when compared to the mean value of the assemblage as a whole; the first two of these cases are also comparative samples taken outside of the Toluca Valley and their differences are likely driven by geology rather than elevation. Overall, within the Rio Lerma watershed and central Toluca Valley, K levels are consistent and are generally higher, while more variable and lower along the outer margins. Sodium levels also appear to be nonrandom. Generally, higher levels of Na can be found at locations closer to the Rio Lerma at lower elevations, while Na decreases radiating up and away from the center of the valley (Fig. 6). This is due to the increased mobility of alkali metals such as K and Na in which weathering of higher elevation volcanic rocks results in the condensation of the elements at lower elevations (Golitko et al., 2012; Buxeda i Garrigos, 1999; Buxeda i Garrigos et al., 2002; Schwedt and Mommsen, 2004). Previously, Stoner et al. (2014) have demonstrated a similar pattern of elevated Na and K levels with sherds from Xaltocan, a low-lying island settlement in the Basin of Mexico. Their series of experiments resulted in a conclusion that these elevated levels could not be a product of post depositional processes. Rather, they concluded that elevated levels of these elements were the result of natural diagenesis of the clays themselves and/or the pre-firing production processes of the potters. In the present study, with no archaeological sherds included, any anthropogenic activity can be

Table 4 Pearsons correlation analysis demonstrating geographic trends in clay chemistry *critical value: α = 0.05; 2.048/ α = 0.10; 1.701. East-west trends

North-south trends

Element

r value

t score

r value

t score

La Lu Nd Sm U Yb Ce Co Cr Cs Eu Fe Hf Rb Sb Sc Sr Ta Tb Th Zn Zr Al Ba Ca Dy K Mn Na Ti V

−0.0705 −0.3493 −0.0131 −0.0835 −0.2494 −0.2951 −0.0401 0.1447 0.3019 −0.4311 0.0501 −0.0905 −0.2267 −0.2554 −0.0205 −0.0579 0.2321 −0.2126 −0.0817 −0.2276 −0.4336 −0.0666 −0.2149 0.1674 0.2257 −0.1639 −0.0076 0.2116 0.3193 −0.2756 −0.4834

−0.3739 −1.9723 −0.0693 −0.4433 −1.3627 −1.6346 −0.2122 0.7741 1.6755 −2.5282 0.2655 −0.4808 −1.2318 −1.3981 −0.1087 −0.3068 1.2624 −1.1515 −0.4337 −1.2367 −2.5459 −0.3533 −1.1644 0.8985 1.2261 −0.879 −0.0401 1.1458 1.7829 −1.5169 −2.9223

0.0545 0.1158 0.0027 −0.0117 0.2012 0.0062 0.0358 −0.3274 −0.531 0.3564 −0.0569 −0.3692 0.0582 0.3916 −0.0902 −0.3874 0.0124 0.2134 0.1041 0.2626 −0.1014 −0.0055 −0.2372 0.0147 0.0959 −0.0068 −0.1196 −0.0887 0.0563 −0.2114 −0.1445

0.2888 0.6171 0.0141 −0.062 1.0868 0.0327 0.1896 −1.8335 −3.3163 2.0187 −0.3018 −2.1022 0.3084 2.2521 −0.4792 −2.2234 0.0658 1.1557 0.5537 1.4402 −0.5395 −0.0292 −1.292 0.0776 0.5097 −0.0358 −0.6375 −0.4713 0.2982 −1.1444 −0.7725

useful in determining provenance without comparison to precise deposit locales. It should also be noted that these six elements remain the most variable (highest CV), when the distinctive outlier samples to the

Fig. 4. Results of Cluster Analysis relative to preliminary group assignments. 9

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Fig. 5. R-Q Mode biplot of the sample on Principal Component 1 and Principal Component 2.

having water sources characterized by high sodicity as a result of the weathering of volcanic ash (Krasilnikov et al., 2013: 113), and the relatively high levels of Na + and K + measured in regional groundwater flows in the Toluca Valley specifically (Esteller and Andreu, 2005). Second, Sb and Sr concentrations may distinguish particular subregions. Sb varies within the Toluca Valley samples as well; samples from the southern and western portions of the valley generally feature higher concentrations than samples from the more north-central portion of the valley. This may be related to the underlying geology; these western and southern portions of the valley are generally younger and more basic-igneous. The pattern for Sr is more complex, on the other hand, with a broad trend toward relatively low values in the western wing of the Toluca Valley and in the external reference samples from south of the valley proper, but spatially mixed values in most of the central and southern Toluca Valley. Third, the final two highly variable elements, Cr and Co are best considered in light of their known patterns in the adjacent Basin of Mexico. In that region, due to the mafic composition of the volcanic material from which clays originated (Mooser et al., 1974; Nichols et al., 2002; Stoner, 2016), Cr and Co, among other transition metals, generally increase from north to south in the Basin on the eastern side of Lake Texcoco. While the subtleties of individual specimens may have compositional distributions that blur this distinction, the trends are clear. Like the identification of Na and K as geographically diagnostic elements above, the identification of these trends is of particular value in that they may allow for informed hypotheses of geographic origin of archaeological ceramics. For example, in the Basin of Mexico, a compositional group that is high in Cr and Co is more likely to have originated further south in the Basin than a group with low Cr and Co values (Stoner, 2016). Though most study has focused upon the eastern side of the Basin, similar north–south trends have been observed on the western side of the Basin as well. But, this side also features gradations of Hf, Rb, Th, and Ta, among other trace elements that vary gradually from the east to the west (Neff and Glascock, 2000; Nichols et al., 2002; Stoner, 2016). Statistically, these types of trends can be demonstrated through regression analyses corresponding with the northing and easting values. In this regard, some similar trends are present in the

Table 5 Descriptive statistics for Toluca Valley Clays by element. Element

Mean

St. Dev.

% St. Dev

La Lu Nd Sm U Yb Ce Co Cr Cs Eu Fe Hf Rb Sb Sc Sr Ta Tb Th Zn Zr Al Ba Ca Dy K Mn Na Ti V

22.7633 0.3183 24.9565 5.5592 2.1578 2.094 52.6031 22.7981 159.4902 2.8791 1.5604 54175.882 6.4296 36.4096 0.669 18.0476 333.2959 0.665 0.7029 6.1309 87.3371 152.2787 129298.63 566.7439 17366.098 4.0443 7069.7106 833.1776 13047.78 6871.8148 134.361

7.4474 0.0787 8.2459 1.6196 0.7615 0.5314 18.675 14.5713 193.8746 1.2627 0.4455 18569.7 1.9727 15.2046 1.2101 6.9085 221.549 0.2071 0.227 2.0743 16.3799 46.4022 32226.781 256.1525 10413.681 1.2793 4293.1187 353.3397 8324.7125 2577.6525 59.0943

32.72% 24.71% 33.04% 29.13% 35.29% 25.38% 35.50% 63.91% 121.56% 43.86% 28.55% 34.28% 30.68% 41.76% 180.89% 38.28% 66.47% 31.14% 32.30% 33.83% 18.75% 30.47% 24.92% 45.20% 59.97% 31.63% 60.73% 42.41% 63.80% 37.51% 43.98%

ruled out. As such, the formation processes of the clays themselves appear to be the only reasonable conclusion for elevated Na and K levels in samples closer to the valley floor. Like Xaltocan, therefore, these two elements are spatially diagnostic in the Toluca Valley and reflect a higher density of saline clays near the Rio Lerma. This corresponds well to the general characterization of the Transmexican Volcanic Belt as 10

Journal of Archaeological Science: Reports 29 (2020) 102094

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Fig. 6. Valley-wide sodium interpolation.

that the control samples taken from areas outside of the valley to the south and west can be clearly differentiated from those located within the valley (Fig. 8). For example, specimen ACH586 shows little compositional relatedness to the rest of the sample and is also located in a uniquely schistose region to the west of the Toluca Valley at the site of La Peña. Based upon the comparison of specimens within our sample, it does appear that the Toluca Valley and Rio Lerma drainage features a unique chemistry that may differ from clays collected elsewhere, which is not unexpected based on the differing geologies of the regions where these samples were taken. As a result, a more thorough discussion of these specimens in regard to larger scale regional patterns and differences is warranted.

Toluca Valley (Fig. 7) west of the Sierra de las Cruces. Cr and Rb, for example, show directional trends comparable to those from the Basin of Mexico (see Table 4). These results demonstrate a continuity of compositional gradations throughout the broader region with some elements while others show diverging patterns. Thus, as these clinal geographic trends at times appear common between the Basin and the Toluca Valley, the determination of the chemical structure of the Toluca Valley as well as the broader region can be particularly useful for differentiation among resource acquisition locales Fig. 8. The limitations posed by the aforementioned regression analysis approach reduces the identification of trends to strict cardinal directions. For this reason, it is necessary to look at compositional differences at a finer resolution to determine the full suite of elements that may be spatially diagnostic along a variety of axes. Specifically, along the Rio Lerma and in other low-lying areas, there tends to be higher proportions of K, Na, Ba, Sr, and Ca. Additionally, samples in closer proximity to the Rio Lerma feature lower levels of most transition metals, lanthanide series elements, Hf, and Zr than higher elevation areas. This is largely due to the concentrations of transition metals and lanthanides in the parent volcanic rocks that make up the surrounding mountain ranges. These particular elements tend to be less mobile and are less susceptible to leaching (Stoner et al., 2014). By contrast, Alkali and Alkaline Earth metals are less static due to their greater mobility and leaching. Therefore, certain elements such as Ca, K, Na, and Ba will become concentrated in lower elevations as they weather out of the volcanic rocks (Golitko et al., 2012; Buxeda i Garrigos, 1999; Buxeda i Garrigos et al., 2002; Schwedt and Mommsen, 2004) as is evident here by the concentration of certain elements nearer to the Rio Lerma. These patterns can be visually expressed through the GIS compositional interpolation technique described above. In doing so, this demonstration of compositional clines based upon increasing and/or decreasing proportions of specific elements across space, provides further demonstration of each element’s utility as a geographically diagnostic aspect of clay composition for the Toluca Valley. Notably, the two control samples (ACH581 and ACH582) from the areas just north of the Toluca Valley do not show strong compositional distinctions from those collected within the valley. As the area to the north represents the continuation of the Lerma drainage and underlying geological formations, the lack of difference in these samples is unsurprising. On the other hand, our data exploration has demonstrated

3.2. Differences between the Toluca Valley and adjacent regions Given the differences noted between the current samples taken within the Toluca Valley, and those taken from adjacent areas to the west and south, comparisons between the current samples and broader regional datasets are useful for illuminating broader regional patterns. MURR’s compositional database contains a total of 237 raw clay samples from elsewhere in the Central Highland region, making it the most thoroughly sampled region in Mesoamerica for clays. However, these clays are primarily from the eastern side of Lake Texcoco, and the region around Teotihuacán in particular is heavily represented. The wealth of data from this region is due in large part to the long-term work of Mary Hodge (Hodge, 1992; Hodge et al., 1992, 1993; Minc, 1994; Minc et al., 1994; Hodge and Neff, 1997; Hodge and Neff, 2005; Neff and Hodge, 1997), Elizabeth Brumfield (Brumfiel, 2005; Brumfield and Hodge, 1996), Deborah Nichols (Nichols et al., 2002), Destiny Crider (2011), and Wesley Stoner (Stoner, 2016; Stoner and Nichols, 2019; Stoner et al., 2014, 2015), and has been invaluable to broader Basin of Mexico analyses. Above, we have identified a number of elements which are geographically diagnostic in the Toluca Valley through multiple complimentary analyses. This has permitted us to compare the Toluca Valley clays to those from the Basin of Mexico to determine key differences and similarities in these diagnostic trends. Taken in aggregate, Toluca Valley clays tend to be higher in transition metals such as Co, Cr, Sc, Ti, and Fe, but lower Ca and K. Barium, in particular, has distinct differences between the two areas, demonstrating both intra-regional and 11

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Fig. 7. North-south trending of Chromium and Rubidium in the Basin of Mexico and the Toluca Valley.

trends in Cr levels, Co is a diagnostic element in the Basin of Mexico with a distinct Northerly trend. In the Toluca Valley, on the other hand, Co is much more variable and lacks the same gradual increase in levels gradating northward. To more directly compare the two areas multi-dimensionally, we at last conducted another Cluster Analysis containing both the Toluca Valley samples and the Basin of Mexico samples. While the Toluca Valley sample does not clearly discriminate from the Basin of Mexico specimens in all cases, a small cluster of Basin of Mexico specimens does show some notable similarity to the Toluca Valley specimens. The vast majority of the Basin of Mexico samples were collected from just northeast of the lake. Yet the specimens most similar to the Toluca Valley sample are primarily peripheral samples further to the northeast and samples on the southern margins of the past lake. The fact that these peripheral specimens are most similar to the Toluca sample when considering all elements in a Cluster Analysis confirms the above analyses in which compositional variables are largely driven by the provenance in context to latitude and elevation. As such, there is a notable continuity in the geochemistry of clays on both sides of the Sierra de las Cruces in many ways, despite having some differentiating elements between the two areas.

inter-regional variation. Potassium, on the other hand, may be less effective in differentiating the two regions, despite large differences in mean K between the two assemblages. On average, K is higher to the east of the Sierra de las Cruces due to the collection of leeched minerals in the Basin in the form of salty clays. In the West, our sample was less densely collected and features samples from a wide variety of elevations and even multiple watersheds. For reasons discussed above, the greater variability in elevation of this sample has resulted in a higher K CV. However, within the Toluca Valley, samples collected near the Rio Lerma are more homogenous and have proportions similar to the Basin of Mexico, suggesting that valley floor clays in the two regions may not show significant differences in K. Conversely, at higher elevations on the western side, K levels are lower than in the Basin of Mexico to the east. These few outlying specimens in a relatively small sample have resulted in mean K values west of the Sierra de los Cruces notably divergent from those to the east (Fig. 9). As such, high K alone may indicate a number of potential origin locales based upon elevation on both sides of the Sierra de las Cruces. With K as well as many other elements, there is some overlap in the frequency ranges. Further, we are also limited in our ability to fully understand compositional distributions across the Toluca Valley by the small and widely dispersed sample presently available. Nonetheless, clays are generally more homogenous in the Basin of Mexico, and certain elements are far more variable west of the Sierra de las Cruces. For example, as well as the aforementioned 12

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Fig. 8. Noted outliers in the present sample demonstrated through distribution of Chromium and Europium.

Fig. 9. Comparison of Potassium and Chromium distributions in the Toluca Valley vs. the Basin of Mexico.

4. Conclusions

those within the valley. In contrast, samples taken from areas to north (Samples 591 and 592), which is a continuation of the same watershed, are not differentiated from those from within the Toluca Valley. When compared to prior datasets of clay samples from the greater Basin of Mexico to the east, the Toluca Valley can be distinguished by higher levels of many transition metals, with barium being especially distinctive, though there is some overlap in the ranges of values present. These results confirm those previously produced by the analysis of archaeological ceramics from the Toluca Valley region. On a local scale, adjacent clays can exhibit relatively high levels of chemical variability,

This article presents the results of INAA of 28 clay samples from the Toluca Valley and immediately surrounding areas. While the limited sample size of this study means that the results should be interpreted with a reasonable degree of caution, they demonstrate internal clines in Sodium and Potassium frequencies within the Toluca Valley based on elevation, and a north–south gradient in Chromium concentrations. Samples taken from areas to the west (Sample 586) and south (Samples 591 and 592) of the Toluca Valley were compositionally distinct from 13

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something that corresponds well to the relatively broad “local” compositional groups produced by archaeological ceramics from sites in the region. On a regional scale, prior studies of archaeological ceramics from the Toluca Valley found relatively high levels of Ba and Sr and lower levels of rare earth elements compared to archaeological ceramics from the Basin of Mexico (Stoner and Glascock, 2013a). The present study demonstrates that the differences, especially in Ba, are also present in clays from the respective regions, and thus not solely the product of differential tempering practices. The results of the current study also show partial agreement with results of Tenorio et al (2005) who analyzed archaeological ceramics (both stylistically local and foreign) and clays from San Miguel Ixtapan, a site at approximately the same latitude as the current peripheral southern samples (Samples 591 and 592), and the same longitude as the peripheral western sample (Sample 586), though the site’s underlying geology is distinct from all of our samples. In that study, samples in the “local” groups generally had higher Cr values than those the “foreign” groups, which correspond to the Toluca Valley and the Basin of Mexico, matching well with the relatively higher Cr values in our southern periphery samples. However, their regional frequencies of Rb are reversed relative to our study, suggesting a complex local geology along the edges of the Central Highland Plateau. From a broader methodological standpoint, this study demonstrates the value of sampling outside of an expected source region in order to establish the limits of an observed pattern. While including an outgroup is common in many scientific fields, it is not a common practice in most archaeological analyses. Within the current samples, the clear distinctions between some of the peripheral samples and the Upper Lerma watershed allow for the identification of geographic boundaries across which archaeological ceramics are likely to have distinctly different chemistry. In a relatively chemically variable area, such as the Toluca Valley, such outgroup samples also provide markers for how much variation can be considered local “noise” as opposed to meaningful macroregional variation. On a larger geographic scale, the entire current sample provides an outgroup to the better-studied Basin of Mexico, but a less distinctive one than has often been assumed. The relative similarities between the northeastern Basin and the Toluca Valley may warrant increased caution in automatically assuming that ceramic samples found in the Basin must also source there, especially for periods such as the Epiclassic, when there are few stylistic distinctions between ceramics produced in the two regions.

Bishop, R.L., Rands, R.L., Holley, G.R., 1982. Ceramic compositional analysis in archaeological perspective. In: Advances in Archaeological Method and Theory, vol. 5. Academic Press, New York, pp. 275–330. Bloomfield, K., Valastro, S., 1974. Late Pleistocene eruptive history of Nevado de Toluca volcano, Central Mexico. Geol. Soc. Am. Bull. 85 (1974), 901–906. Bloomfield, K., Valastro, S., 1977. Late Quaternary tephrachronology of the nevado de toluca volcano, central Mexico. Overseas Geol. Mineral Resour. 46 (1977), 1–15. Branstetter-Hardesty, B., 1978. Ceramics of Cerro Portezuelo, Mexico: an Industry in Transition. Department of Anthropology, University of California, Los Angeles, Los Angeles. Brumfiel, E.M. (Ed.) 2005 La producción local y el poder en el Xaltocan Posclásico / Production and Power at Postclassic Xaltocan. Arqueología de México. Instituto Nacional de Antropología e Historia, Mexico City; University of Pittsburgh, Pittsburgh. Brumfiel, E.M., Hodge, M.D., 1996. Interaction in the Basin of Mexico: the case of Postclassic Xaltocan. In: Mastache de Escobar, A.G., Parsons, J.R., Santley, R.S., Serra Puche, M.C. (Eds.), Arqueología Mesoamericana: Homenaje a. Instituto Nacional de Antropología e Historia, Arqueología Mexicana, México, pp. 417–437. Buxeda i Garrigos, J., 1999. Alteration and contamination of archaeological ceramics: the perturbation problem. J. Archaeol. Sci. 26 (3), 295–313. Buxeda i Garrigos, J., Mommsen, H., Tsolakidou, A., 2002. Alterations of Na, K, and Rb concentrations in Mycenaean pottery and a proposed explanation using X-ray diffraction. Archaeometry 44 (2), 187–198. Caballero, M., Ortega, B., Valadez, F., Metcalfe, S., Macias, J.L., Sugiura, Y., 2002. Sta. Cruz Atizapán: a 22-ka lake level record and climatic implications for the late Holocene human occupation in the Upper Lerma Basin, Central Mexico. Palaeogeogr. Palaeoclimatol. Palaeoecol. 186 (3–4), 217–235. Cogswell, J.W., Neff, H., Glascock, M.D., 1996. The effect of firing temperature on the elemental characterization of pottery. J. Archaeol. Sci. 23, 283–287. Cohen, A.S., 2016. Creating an Empire: Local Political Change and Angamuco, Michoacán, Mexico. Doctoral Dissertation. Department of Anthropology, University of Washington. Cordell, A.S., Wallis, N.J., Kidder, G., 2017. Comparative clay analysis and curation for archaeological pottery studies. Adv. Archaeol. Pract. 5 (1), 93–106. Crider, D.L., 2011. Epiclassic and Early Postclassic Interaction in Central Mexico as evidenced by decorated pottery. Doctoral Dissertation. Arizona State University, Tempe, AZ. Esteller, M.V., Andreu, J.M., 2005. Anthropic effects on hydrochemical characteristics of the Valle de Toluca aquifer (Central Mexico). Hydrogeol. J. 13 (2), 378–390. García-Palomo, A., Macías, J.L., Arce, J.L., Capra, L., Garduño, V.H., Espíndola, J.M. 2002 Geology of Nevado de Toluca Volcano and Surrounding Areas, Central Mexico. Glascock, M.D., 1992. Characterization of archaeological ceramics at MURR by neutron activation analysis and multivariate statistics. In: Neff, H. (Ed.), Chemical Characterization of Ceramic Pastes in Archaeology. Prehistory Press, Madison, WI, pp. 11–26. Golitko, M., Dudgeon, J.V., Neff, H., Terrell, J.E., 2012. Identification of post-depositional chemical alteration of ceramics from the north coast of new guinea (sandaun province) by time-of-flight laser ablation-inductively coupled plasma-mass spectrometry (TOF-LA-ICP-MS). Archaeometry 54 (1), 80–100. Golitko, M., Feinman, G.M., 2015. 2015 Procurement and distribution of Pre-hispanic Mesoamerican obsidian 900 BC-AD 1520: a social network analysis. J. Archaeol. Method Theory 22, 206–247. González de la Vara, F. 2011 Historia prehispánica del valle de Toluca. In Historia general ilustrado del Estado de México, vol. 1: geografía y arqueología, edited by Y. Sugiura Yamamoto, pp. 181-216, M. T. Jarquín Ortega and M. Miño Grijalva, general editors. Gobierno del Estado de México and El Colegio Mexiquense, Toluca. Hernández, C.L., Healan, D.M., 2008. The role of late pre-contact colonial enclaves in the development of the Postclassic Ucareo Valley, Michoacan. Mexico. Ancient Mesoamerica 19 (2), 265–282. Hodge, M.G., 1992. The geographical structure of Aztec imperial-period market systems. Natl. Geogr. Soc. Res. Explor. 8, 428–445. Hodge, M.G., Neff, H. 1997 Xaltocan in the Economy of the Basin of Mexico: A View from Ceramic Tradewares. In Postclassic Xaltocan: Ecological and Social Determinants of Production in the Northern Basin of Mexico, edited by E. M. Brumfiel. Latin American Archaeology Report. Department of Anthropology, University of Pittsburgh, and Instituto Nacional de Antropología e Historia, Mexico. Hodge, M.G., Neff, H., Blackman, M.J., Minc, L.D., 1992. A compositional perspective on ceramic production in the Aztec Empire. In: Neff, H. (Ed.), Chemical Characterization of Ceramic Pastes in Archaeology. Prehistory Press, Madison, pp. 203–220. Hodge, M.G., Neff, H., Blackman, M.J., Minc, L.D., 1993. Black-on-orange ceramic production in the Aztec Empire’s heartland. Latin Am. Antiquity 4, 130–157. Huster, A.C., 2016. The Effects of Aztec Conquest on Provincial Commoner Households at Calixtlahuaca, Mexico. Doctoral Dissertation. School of Human Evolution and Social Change, Arizona State University, Tempe, AZ. Huster, A.C., 2018. Regional-level exchange in Postclassic Central Mexico. J. Anthropol. Archaeol. 50, 40–53. Hodge, M.G., Neff, H. 2005 Xaltocan in the Economy of the Basin of Mexico: a view from ceramic tradewares. In La producción local y el poder en el Xaltocan Posclásico / Production and Power at Postclassic Xaltocan, edited by E. M. Brumfiel, pp. 348-368. Arqueología de México. Instituto Nacional de Antropología e Historia, Mexico City and University of Pittsburgh, Pittsburgh. INEGI 2001 Carta Estatal Geológica: México. INEGI: Direccion General de Geografía. Kabata, S. 2010 La dinámica regional entre el Valle de Toluca y las areas aircundantes: intercambio antes y después de la Caída de Teotihuacan. PhD Dissertation, Instituto de Investigaciones Antropológicas, UNAM, Mexico, D.F. Krasilnikov, P., Gutiérrez-Castorena, M. de C., Ahrens, R.J., Cruz-Gaistardo, C.O., Sedov,

Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements Funding for the field collection and INAA of samples was provided by a Rust Family Foundation Grant to Huster (RFF-2017-37). Analysis of samples at MURR was supported by National Science Foundation grant to the Archaeometry Laboratory at the University of Missouri Research Reactor (1415403). The authors also thank two anonymous reviewers for their suggestions; any remaining errors are our own. References Arce, J.L., Macías, J.L., Vázquez-Selem, L., 2003. The 10.5 ka plinian eruption of Nevado de Toluca volcano, Mexico: stratigraphy and hazard implications. Geol. Soc. Am. Bull. 115 (2), 230–248. Arnold, D.E., Neff, H., Bishop, R.L., 1991. Compositional analysis and “sources” of pottery: an ethnoarcheological approach. Am. Anthropol. 93 (1), 70–90. Benitez, A.V. 2006 Late Classic and Epiclassic obsidian procurement and consumption in the southeastern Toluca Valley, Central Highland Mexico. Doctoral Dissertation, Department of Anthropology, University of Texas at Austin, Austin, TX.

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Smith, M.E., Novic, J., Huster, A.C., Krofges, P.C., 2009. Reconocimiento superficial y mapeo en Calixtlahuaca en 2006. Expresión Antropológica (Instituto Mexiquense de Cultura) 36, 39–55. Stoner, W.D., 2016. The analytical nexus of ceramic paste composition studies: a comparison of NAA, LA-ICP-MS, and petrography in the prehispanic Basin of Mexico. J. Archaeol. Sci. 76, 31–47. Stoner, W.D., Glascock, M.D. 2011 Neutron Activation Analysis of Ceramic Samples from Five Sites in the Toluca Valley and the Basin of Mexico. Unpublished technical report. Report on File: Archaeometry Laoratory. University of Missouri Research Reactor. Stoner, W.D., Glascock, M.D. 2013a Neutron Activation Analysis of Formative and Early Classic Pottery from the Teotihuacan Valley. Unpublished technical report. Report on File: Archaeometry Laoratory. University of Missouri Research Reactor. Stoner, W.D., Glascock, M.D. 2013b Neutron Activation Analysis of Pottery from Calixtlahuaca in the Toluca Valley. Unpublished technical report. Report on file: Archaeometry Laboratory. University of Missouri Research Reactor. Stoner, W.D., Nichols, D.L., 2019. Pottery trade and the formation of Early and Middle Formative style horizons as seen from Central Mexico. Ancient Mesoamerica 30 (2), 311–337. Stoner, W.D., Nichols, D., Alex, B.A., Crider, D., 2015. The emergence of Early-Middle Formative exchange patterns in Mesoamerica: a view from Altica in the Teotihuacan Valley. J. Anthropol. Archaeol. 39, 19–35. Stoner, W.D., Millhauser, J.K., Rodríguez-Alegría, E., Overholtzer, L., Glascock, M.D., 2014. Taken with a grain of salt: experimentation and the chemistry of archaeological ceramics from Xaltocan, Mexico. J. Archaeol. Method Theory 21 (4), 862–898. Sugiura Yamamoto, Y. 2000 Proyecto Arqueológico del Valle de Toluca: informe final. Informe entragado al Consejo de Arqueología, Instituto Nacional de Antropología e Historia. Sugiura Yamamoto, Y., 2005a. Y atrás quedó la Ciudad de los Dioses: historia de los asentamientos en el Valle de Toluca. Instituto de Investigaciones Antropológicas, Universidad Nacional Autónoma de México, Mexico City. Sugiura Yamamoto, Y., 2005b. Reacomodo demográfico y conformación multiétnica en el valle de Toluca durante el Posclásico: una propuesta desde la arqueología. In: Manzanilla, L. (Ed.), Reacomodos demográficos del clásico al postclásico en el centro de México. Instituto de Investigaciones Antropológicas, Universidad Nacional Autónoma de México, Mexico City, pp. 175–202. Sugiura Yamamoto, Y. 2009 La gente de la ciénaga en tiempos antiguos: la historia de Santa Cruz Atizapán. Universidad Nacional Autónoma de México, Instituto de Investigaciones Antropológicas, DGAPA. Sugiura Yamamoto, Y., 2013. Reflexiones en torno a los probelmas del Epiclásico y el Coyotlatelco. In: Pomédio, C., Pereira, G., Fernández-Villanueva, E. (Eds.), Tradiciones cerámicas del epiclásico en el Bajío y regiones aledañas: cronología e interacción. BAR Publishing, Oxford, pp. 106–114. Sugiura Yamamoto, Y., Jaimes Vences, G., Kabata Omoya, S., Glascock, M.D., 2018. La obsidiana como un bien de intercambio entre el valle de Toluca y sus regiones circunvecinas durante el Clásico. Anal. Antropol. 52 (2), 55–69. Sugiura Yamamoto, Y., Nieto Hernández, R., 2006. San Mateo Atenco: una sociedad lacustre prehispánica del valle de Toluca. In: García Castro, R., Jarquín Ortega, T. (Eds.), La Proeza Histórica de un pueblo. San Mateo Atenco en el valle de Toluca siglos viii-xix. El Colegio Mexiquense and La Universidad Autonoma del Estado de Mexico, Toluca, Mexico, pp. 21–36. Sugiura, Y., Pérez, C., Zepeda, E., 2017. Acercamiento a un sitio lacustre. Instituto de Investigaciones Antropologicas, UNAM, Mexico City. Sugiura Yamamoto, Y., Villalobos Acosta, C., del Pérez, M.C., Zepeda, E., 2015. Una mirada hacia el proceso de identidad en el valle de Toluca precortesiano, México. Rev. Indias 75 (264), 289–322. Sugiura Yamamoto, Y., Villalobos Acosta, C., Zepada Valverde, E., 2013. Biografía cultural de la cerámica arqueológica desde la perspectiva de la materialidad: el caso del Valle de Toluca. Anal. Antropol. 47 (2), 63–90. Tenorio, D., Almazán-Torres, M.G., Monroy-Guzmán, F., Rodrígiez-García, N.L., Longoria, L.C., 2005. Characterization of ceramics from the archaeological site of San Miguel Ixtapan, Mexico State, Mexico, using NAA, SEM, XRD and PIXE techniques. J. Radioanal. Nucl. Chem. 266 (3), 471–480. Weigand, P., Harbottle, G., Sayre, E., 1977. Turquoise sources and source analysis: Mesoamerica and the southwestern U.S.A. In: Earle, T.K., Ericson, J.E. (Eds.), Exchange Systems in Prehistory. Academic Press, New York, pp. 15–34.

S.,Solleiro Rebolledo, E. 2013 The Soils of Mexico. World Soils Book Series. Springer, New York. Lozano-García, S., Sosa-Nájera, S., Sugiura, Y., Caballero, M., 2005. 23,000 yr of vegetation history of the Upper Lerma, a tropical high-altitude basin in Central Mexico. Quat. Res. 64 (1), 70–82. Minc, L.D., 1994. Political Economy and Market Economy Under Aztec Rule: A regional Perspective Based on Decorated Ceramic Production and Distribution Systems in the Valley of Mexico. Unpublished PhD. Dissertation. Ann Arbor, Department of Anthropology, University of Michigan. Minc, L.D., Hodge, M.D., Blackman, M.J., 1994. Stylistic and spatial variability in early aztec ceramics: insights into pre-imperial exchange systems. In: Hodge, Mary G., Smith, Michael E. (Eds.), Economies and Polities in the Aztec realm. Institute for Mesoamerican Studies, State University of New York, Albany, pp. 133–174. Minc, L.D., Sherman, R.J., 2011. Assessing natural clay composition in the valley of oaxaca as a basis for ceramic provenance studies. Archaeometry 53 (2), 285–328. Mooser, F., Naim, A.E., Negerdank, J.F.W., 1974. Paleomagnetic investigations of the tertiary and quaternary ignaeous rock: VIII, a paleomagnetic and petrologica study of volcanics in the valley of Mexico. Geol. Rundsch. 63 (2), 451–483. Neff, H., 1992. Introduction. In: Neff, H. (Ed.), Chemical Characterization of Ceramic Pastes in Archaeology. Prehistory Press, Madison, WI, pp. 1–10. Neff, H., 2000. Neutron activation analysis for provenance determination in archaeology. In: Ciliberto, E., Spoto, G. (Eds.), Modern Analytical Methods in Art and Archaeology. John Wiley and Sons, Inc., New York, pp. 81–134. Neff, H., Bove, F.J., Lou, B., Piechowski, M.F., 1992. Ceramic raw materials survey in Pacific coastal Guatemala. In: Neff, H. (Ed.), Chemical Characterization of Ceramic Pastes in Archaeology. Prehistory Press, Madison, WI, pp. 59–84. Neff, H., Glascock, M.D., 2000. Provenance Analysis of Aztec Period Ceramics From the Basin of Mexico: Final Technical Report. University of Missouri Research Reactor. McVicker, D., Lambertino-Urquizo, L., Glascock, M.D., Neff, H. 2003. Regional Production for the International Market: Aztec Black-on-Orange Ceramics from Tlacotepec, Valley of Toluca, Mexico. Unpublished manuscript. Neff, H., Hodge, M.G. 1997 Serving Vessel Production at Chalco: Evidence from Neutron Activation Analysis. In Place of Jade: Society and Economy in Ancient Chalco, edited by M.G. Hodge. Latin American Archaeology Reports. Department of Anthropology. University of Pittsburgh, Pittsburgh and Instituto Nacional de Antropología e Historia, Mexico. Newton, A.J., Metcalfe, S.E., 1999. Tephrochronology of the Toluca basin, central Mexico. Quat. Sci. Rev. 18 (8–9), 1039–1059. Nichols, D.L., Brumfiel, E.M., Neff, H., Hodge, M., Charlton, T.H., Glascock, M.D., 2002. Neutrons, markets, cities, and empires: A 1000-year perspective on ceramic production and distribution in the Postclassic Basin of Mexico. J. Anthropol. Archaeol. 21 (1), 25–82. Papritz, A., Stein, A., 1999. Spatial prediction by linear kriging. In: Stein, A., Van der Meer, F., Gorte, B. (Eds.), Spatial Statistics for Remote Sensing. Springer, Netherlands, pp. 83–113. Parsons, J.R., Brumfield, E.M., Parsons, M.H., Wilson, J.D., 1982. Pre-Hispanic settlement patterns in the Southern Valley of Mexico: the Chalco-Xochimilco region. University of Michigan, Ann Arbor. Pollard, H.P., Hirshman, A., Neff, H., Glascock, M.D., 2005. Exchange, elites, and the emergence of the Tarascan core. In: Dillon, B.D., Boxt, M.A. (Eds.), Archaeological Papers in Honor of Clement W. Meighan. Labrynthos, Lancaster, CA, pp. 295–307. Ramírez Sánchez, S.P. 2012 Desarollo histórico de una comunidad del Valle de Toluca. Sitio Arqueológico “El Calvario”, Santa María Rayón. Licenciatura Thesis, Centro Universitario UAEM Tenancingo, University Autonoma del Estado de Mexico, Toluca, Mexico. Sanders, W.T., Parsons, J., Santley, R.S., 1979. The Basin of Mexico: Ecological Processes in the Evolution of Civilization. Academic Press, New York. Schwedt, A., Mommsen, S., 2004. Clay paste mixtures identified by neutron activation analysis in pottery of a Roman worshop in Bonn Germany. J. Archaeol. Sci. 31 (9), 1251–1258. Sedov, S., Solleiro-Rebolledo, E., Morales-Puente, P., Arias-Herreı ̀a, A., Vallejo-Gòmez, E., Jasso-Castañeda, C., 2003. Mineral and organic components of the buried paleosols of the Nevado de Toluca, Central Mexico as indicators of paleoenvironments and soil evolution. Quat. Int. 106, 169–184. Smith, M.E., Borejsza, A., Huster, A.C., Frederick, C.D., Rodríguez López, I., Heath-Smith, C., 2013. Aztec period houses and terraces at Calixtlahuaca: the changing morphology of a Mesoamerican hilltop urban center. J. Field Archaeol. 38 (3), 225–241.

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