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Identification of prehispanic rotary querns production areas in Las Cañadas del Teide (Tenerife, Canary Islands, Spain)
Journal of Archaeological Science: Reports 28 (2019) 102048
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Identification of prehispanic rotary querns production areas in Las Cañadas del Teide (Tenerife, Canary Islands, Spain)
T
Matilde Arnay-de-la-Rosaa,b, , Emilio González-Reimersa,b, Efraín Marrero-Salasa,b, Carlos García-Ávilaa,b, Constantino Criado-Hernándeza,b, Alberto Lacave-Hernándeza,b, Rebeca González-Fernándeza,c, Ithaisa Abreu-Hernándeza,b ⁎
a
Universidad de La Laguna, Tenerife, Canary Islands, Spain Researchers adscribed to the MINECO-FEDER project “Guanches y Europeos en las Cañadas del Teide, Ocupación, producción y comunicación”, Spain c Servicio de Apoyo a Criminalística Forense, Servicio General de Apoyo a la Investigación (SEGAI) and Laboratorio de Biología del Desarrollo, UD de Bioquímica y Biología Molecular, Universidad de La Laguna, Tenerife, Canary Islands, Spain b
ARTICLE INFO
ABSTRACT
Keywords: Grinding stone Portable querns Guanches Tenerife Las Cañadas del Teide portable X ray fluorescence
Portable querns were commonly used by the prehispanic population of Tenerife. In Tenerife, these instruments are built on rocks, usually of vesicular nature –such as those emitted as scoria by pyroclastic cones-, resistant enough to allow molturation of grains, but generally of light weight to facilitate manual transport. In the highlands of Tenerife there are many archaeological remains of the prehispanic population (Guanches). After systematic survey of 19 pyroclastic cones present in the highlands, only in 2 we found remains of workspaces in which grinding stones were manufactured. This finding suggests that production of grinding stones was a specialized task, and that, instead of producing them as needed, the Guanches acquired them in these two production sites. Chemical composition of 30 samples of the raw material used in each of these two wokspaces showed differences in composition big enough to perform a discriminant analysis that allowed a clear-cut separation of both workspaces. Indeed, the function was applied to 13 pieces or fragment of pieces found about 500 m around the workspaces, fully confirming the validity and usefulness of the function obtained. In addition, we also examined 12 rotary querns (complete or fragmented) found at diverse locations of the island, currently housed at the laboratory of the Department of Prehistory of the University of La Laguna (Tenerife). The application of the discriminant function to these samples allowed the identification of the provenance of 9 cases. Therefore pXRF analysis may be useful in provenance studies of rotary querns, although our data also suggest that not all the rotary querns were manufactured in the workspaces described in this study.
1. Introduction Tenerife is the largest island of the Canary Archipelago, sharing with the remaining islands a turbulent geological history. After many submarine eruptions, the island finally emerged about 7.5–11.5 million years ago (Ancochea et al., 1990; Anguita et al., 2002). Continuous volcanic activity with repeated eruptions followed by several massive gravitational collapses have contributed to shape the current landscape of the island, with a central volcanic caldera 16 km in diameter (Las Cañadas), towered by the Teide peak (3718 m height). A range with some peaks reaching 2000–2400 m over sea level extends from the center to the northeastern part of the island (Cordillera Dorsal). On the other side, some relatively recent volcanoes, reaching 1500–1800 m over sea level prolong the central highlands to the northwest.
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Therefore, a northern slope and a southern slope are clearly defined in the island, separated by the Teide/Cañadas volcanic complex, the northwestern volcanoes, and the Cordillera Dorsal. Located at 28th North, in front of the Sahara desert, two main factors have a decisive influence on the climatic conditions of the island: the vicinity of the Sahara desert and the northeastern trade winds, which usually blow below 1300–1800 m altitude. Therefore, clouds associated with the trade winds stagnate in the northern slopes, providing rain and moisture to this part of the island. In contrast, arid conditions predominate in the southern slopes. The central highlands of Tenerife (mean altitude of the Cañadas caldera is about 2000–2300 m over sea level) constitute a special environment, with sparse vegetation, many lava flows, and rough climatic conditions. Visited by the inhabitants of the island during centuries or
Corresponding author at: Dpt. de Geografía e Historia, Universidad de La Laguna, Tenerife, Canary Islands, Spain. E-mail address: [email protected] (M. Arnay-de-la-Rosa).
https://doi.org/10.1016/j.jasrep.2019.102048 Received 20 January 2019; Received in revised form 14 October 2019; Accepted 15 October 2019 2352-409X/ © 2019 Elsevier Ltd. All rights reserved.
Journal of Archaeological Science: Reports 28 (2019) 102048
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Fig. 1. Prehispanic portable rotary quern found near Cruz de Tea.
individuals, buried following the prehispanic ritual, with an antiquity dating from the 16th and even 17th centuries, nearly 200 years after Spanish conquest. These individuals were buried in the same caves that harbor other corpses with an antiquity of 900–1100 BP (Arnay-de-laRosa et al., 2011). In Las Cañadas there are also other burial caves containing skeletons with an antiquity of 1600 BP. Therefore, the central highlands were inhabited by the prehispanic people (Guanches) either temporarily or permanently during at least 1200 years, something attested by the many archaeological remains found in this area. Among the several kinds of archaeological remains observed in Las Cañadas, grinding stones, especially rotary querns, are quite abundant (Diego Cuscoy, 2008). Rotary querns were usually employed by the prehispanic inhabitants of the Canary Islands, and far beyond the conquest, by the modern rural population. In contrast with Gran Canaria, in which the main raw material destined to the production of these artifacts was lapilli tuff (Mangas et al., 2008), and, less frequently, basalt, extracted from vertical basaltic walls (Naranjo-Mayor et al., 2016), in Tenerife, rotary querns were manufactured in diverse porous magmatic rocks (Fig. 1), that can be found in the volcanic landscape of the Island, especially in cinder cones with gross pyroclastic blocks. Grinding stones have been found in many parts of Las Cañadas and also in coastal areas or medium height areas. It is unclear, however, whether the prehispanic population of the island manufactured the querns when needed, or if there were some kind of workspaces in which more or less specialized people manufactured these instruments. Only a report in 1950 describes a small “factory” in a place named Pedro Méndez (Serra Rafols and Diego Cuscoy, 1950).
millennia, as inferred from C-14 dating (Arnay-de-la-Rosa et al., 2011), geographical environment does not favor a steady settlement in an island in which there are northern coastal regions with a subtropical climate and enough rainfall that allows agriculture, and middle-height zones with dense forest, abundant rain and a mild temperate climate. However, in the central highlands there are many remains of the Prehispanic population, including burial caves containing more or less mummified corpses, and many dwelling areas with abundant pottery fragments and stony artifacts – especially obsidian tools (Arnay-de-laRosa and González-Reimers, 2006). The reasons by which this area was colonized before the Spanish conquest are not well understood. Possibly this central region constituted a place in which trade between North and South took place, and it was also a possibly place in which crossbreeding took place between goat (and to a lesser extent, sheep and pig) herds belonging to the population living in the northern and southern slopes. Probably these activities were performed in summer. Reports of chroniclers arriving with Spanish conquerors lend support to this seasonal migration to the highlands (Espinosa, 1980(1590)). Chroniclers also mention that dead were interred in the caves of the central highlands (Frutoso, 2004(1590)). In exceptional conditions of war or danger of captivity, the many caves and rough lava flows of Las Cañadas might constitute excellent places of refuge. These conditions did appear with the Spanish conquest. After cruel battles, some people fled into the mountains, in which the huge lava flows (mainly trachyte or phonolite) with enormous blocks and many caves offered a place where they could hide. Indeed, there are some C-14 dates of skeletal remains of partially mummified
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Fig. 2. Map indicating the two main manufacturing places (asterisks) and the other 17 pyroclastic areas surveyed (circles). 1 = Samara; 2 = La Botija; 3 = Montañeta Negra; 4 = Reventada; 5 = Adara; 6 = Tebite; 7 = Tamarco; 8 = Chircheros; 9 = Cruz de Tea (workspace); 10 = Chío; 11 = Volcán Ciego; 12 = La Corona; 13 = Volcán Escondido; 14 = Los Corrales (workspace); 15 = Los Tomillos; 16 = Mostaza; 17 = Arneas Negras; 18 = Cerrillar; 19 = Calderón.
(Las Cañadas caldera and the western slopes of Pico Viejo, Fig. 2). Most of these areas are scoria cones (cinder cones), besides Calderón (a small collapse caldera, surrounded by an extense area covered with scoria) and Tamarco (a spatter cone). Although in several of them some vestiges of manufacturing of grinding stones were observed (for instance, Los Chircheros, or Los Tomillos), only in two (Cruz de Tea/Chío and Los Corrales) there were data that allow to classify these sites as a production centers or areas, such as many partially manufactured artifacts, chips and fragments of raw material derived from the manufacturing process, and accumulation of tools employed in manufacturing the grinding stones (Fig. 3a and b).
However, detailed prospection of Las Cañadas del Teide carried up by ourselves during the last decades have led to the identification of two main areas of grinding stone manufacturing, namely Cruz de Tea and Los Corrales, quite away from each other. The first one is located in the slopes of Teide Viejo (western part of Las Cañadas) whereas the second one, in the northeastern corner of the Caldera (Fig. 2). Geological composition of these volcanic cones is similar, since they derive from a common evolved parent magma (Ablay et al., 1998), but there are subtle differences in composition of lava flows – more salic in the eastern part of the Caldera, more alkaline in the western slopes. In contrast with the only two major workspaces in which rotary querns were produced, several complete or fragmented pieces are found in the many dwelling areas distributed within the Caldera. It is therefore important to define the characteristics/composition of the raw material of these two major workspaces in which the grinding stones were produced. This allows the adscription of any of the complete pieces found in the dwelling areas to any of the two main production centers. This aids in reconstruction of trade and migration of the primitive inhabitants (Guanches) of Tenerife within the Cañadas caldera. Based on these considerations, the present study was performed in order to characterize the chemical composition of the raw material that served to manufacture the grinding stones in the two mentioned sites, looking for discriminant factors that allow a precise assignation of a given new piece to any of the two main sites of production described.
a) Cruz de Tea. – This is a complex volcanic area (Fig. 4), dominated by three volcanic systems: the Cruz de Tea mountain, The Montaña de Chío mountain, and an innominate third volcanic apparatus, located eastwards from Montaña de Chío, that erupted in the western slope of the stratovolcano Pico Viejo. The area is quite extense, since the workspaces are distributed along the southern slope of Montaña de Chío and its eastern prolongation, and Cruz de Tea. Two lava flows surround the mentioned volcanoes. One of them disrupts the possible union that existed between the lowest (most westernly located) slopes of Montaña de Chío, closing a pyroclastic plain at the southeast, and flowing down around the southern slope of Cruz de Tea; and another one, that flows down in the southern slope of Montaña de Chío (eastern prolongation). Both flows join together westwards, forming a plain, as commented. Both lava flows consists of rocky accumulations separated by relatively large pyroclastic plains. The main area of extraction of raw material is Cruz de Tea, a
2. Methods We surveyed 19 volcanic pyroclastic areas located in the highlands 3
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Fig. 3. Manufacturing place a) general overview; b) lithic instruments used in manufacturing process.
cinder cone formed by basanite/phonotephrite material (Carracedo, 2006), a composition also confirmed by the preliminary results derived from ICP-MS (inductively coupled mass spectrometry) analyses performed by members of our team (Criado-Hernández et al, unpublished data).
surrounds the southern slopes of Cruz de Tea. In this lava flow there are several places that were prepared to achieve more or less flattened areas, usually at the foot of big lava boulders (3–5 m height). In these flattened areas there are many remains of flakes, instruments, fragmented querns, and pottery fragments.
The workspace at Cruz de Tea occupies an area of about 40.000 square meters. Raw material (scoria blocks) was collected from the nearby located slopes of Cruz de Tea mountain and transported to the lapilli plains that partially covered the mentioned lava flow that
b) Los Corrales is a single volcano, in which several cones emerge (4 major ones) surrounding a relatively flat area, covered by gross pyroclastic blocks and some pumice (probably derived from a more recent eruption from Montaña Blanca). In this relatively flat area
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Fig. 4. Cruz de Tea pyroclastic cone.
whether the mineral composition of the 60 samples analyzed adapted to a normal distribution or not. After, we calculated differences in chemical composition of raw material from Cruz de Tea and Los Corrales. Content of some elements were by far higher in the samples from Cruz de Tea than in those from Los Corrales, whereas other elements showed just an opposite trend. Therefore we calculated the ratios between those elements that showed the highest concentrations and those that showed the lowest ones, and compared these ratios among the samples from the two workspaces. With those variables that showed maximal differences (including both single elements and ratios) we performed a stepwise discriminant function analysis, and, after, we applied this discriminant function to the 13 test samples found near the workspaces, in order to assess the reproducibility of the discriminant function. All these analyses were performed with the SPSS 15.0 program (Springfield, Ill, USA). In order to explore the utility of the discriminant function to assign a given rotary quern to any of the two manufacturing sites, we performed a post-hoc analysis of 12 terminated querns or fragments. These querns were currently housed at the laboratory of the Department of Prehistory of the University of La Laguna. In some cases a precise information about the place in which the instrument was recovered was available, but for some other querns only a vague reference was recorded (i.e. “Las Cañadas”, “near Los Tomillos” or “Pico Viejo”).
there are many evidences of partially manufactured specimens, together with many instruments of compact aphanitic stone. The manufacturing area measures approximately 25,000 square meters (Fig. 5). Raw material consists of benmoreite-phonotephrite (Carracedo, 2006) 2.1. Analytical procedure We used a portable energy dispersive X-ray fluorescence analyzer (XRF Thermo Scientific™ Niton™ XL3t GOLDD+; PANATEC SL, Madrid) that allows the identification of the elemental profile of a sample without destroying it. This is achieved by measuring the fluorescent Xray emitted from a sample after excitation by a primary X-ray source. Time of exposure to the X ray beam was 125 s in order to improve detection of light elements. The Analyzer possesses a 50 kV X-ray tube and a silver anode. The samples were measured in La Laguna University (SEGAI) by a direct shot, using the Mining Mode calibration. The area of the sample in contact with the analyzer was carefully cleansed with a brush prior to analysis. By this way, we determined the elemental composition of 30 samples from Cruz de Tea, and 30 samples from Los Corrales. These samples consist of chips and fragments of raw material derived from the manufacturing process. In addition we analyzed the mineral composition of 13 grinding stone fragments found near (in a radius of about 500 m) the two workspaces, as well as elemental composition of 12 querns found in several parts of Tenerife (see below).
3. Results Of the many elements analyzed, we discarded those whose concentrations were very low, around the detection limit. So, concentration of several elements, such as gold, uranium, silver, wolfram, tin, selenium, thorium and rare earths, among others, were not utilized in this
2.2. Statistics We performed a Kolmogorov-Smirnov test in order to discern 5
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Fig. 5. Los Corrales volcanic complex.
study. Crude data of those elements relevant for this study are shown in Table 1. As we can see in Table 2, raw material of the site Cruz de Tea has higher concentration of calcium, magnesium, iron and titanium than rocks from Los Corrales, probably indicating the presence of calciumcontaining plagioclase in higher amounts in Cruz de Tea than in Los Corrales, whereas iron and titanium may reflect the presence of clinopyroxene, a common component of basaltic/basanitic rocks in the Island. As shown in Fig. 6a and b, scattergrams clearly separate Cruz de Tea and Los Corrales. When we calculate the indices Rb/Ca, Rb/Fe, or Rb/Ti we observe that differences are even more marked (Fig. 7a–c). As shown in Fig. 8, the scattergram plotting the correlations between the indices Rb/Ca and Rb/Fe also shows that both sites are clearly identifiable, with no overlapping values. Considering that the values of the calculated indices are normally distributed within each group, the limits of the 95% confidence intervals for the three aforementioned indices are clearly different when the two sites are compared (Fig. 7a–c). In addition, we performed a stepwise discriminant function analysis, introducing the three indices mentioned before, given the marked differences obtained when Cruz de Tea and Los Corrales were compared. Only the indices Rb/Ca and Rb/Fe were selected, and the obtained discriminant function correctly classified the totality of the samples analysed. Discriminant function is 0.903 × Rb/Ca + 4.947 × Rb/Fe −8.457, and centroids are −4.164 for Cruz de Tea and +4.164 for Los Corrales, with standard deviations of 0.903 and 1.262, respectively, that yield confidence intervals of −2.394 to −5.934 for Cruz de Tea and +1.69 to +6.638 for Los Corrales (Fig. 9).
When we applied the discriminant function to 13 samples (flakes, fragments or complete or nearly complete portable querns) found near Cruz de Tea or Los Corrales we obtained the results shown in Table 3, that confirm the reproducibility of the discriminant function obtained. In Table 4 we show the elemental composition, the Rb/Fe, Rb/Ca and Rb/Ti ratios, and the punctuation obtained after applying the discriminant function, of the rotary querns used to test the usefulness of these calculations in the assessment of the provenance of these querns. In Fig. 10 we show the places in which these querns were found, and in Table 4 we also provide the likely provenance of the included querns. 4. Discussion In this study we have characterized the geochemical composition of two quarries in which portable querns were manufactured by the Guanches (the indigenous population of Tenerife). The methodology employed is similar to that reported by other researchers in other parts of the world. For instance, Gluhak and Hofmeister (2009) could identify several quarries in the Eifel region, that served for the production of huge amounts of millstones during the Roman period; Antonelli and Lazzarini (2010) analyzed several vesicular rocks from the Italian Peninsula and neighboring islands in order to identify the quarries that served for manufacturing of millstones and rotary querns and trade routes. In addition, XRF methodology has been successfully applied for identification of the quarries from which lithic material was extracted (for instance, Frahm, 2014; Campbell and Healey, 2018) or the places from which raw material for pottery production was obtained (for instance, Szilagy et al, 2012) or to ascertain variability of ceramic vessels,
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Table 1 Some crude data (direct measurements, in ppm) relevant for this study.
LC-1 LC-2 LC-3 LC-4 LC-5 LC-6 LC-7 LC-8 LC-9 LC-10 LC-11 LC-12 LC-13 LC-14 LC-15 LC-16 LC-17 LC-18 LC-19 LC-20 LC-21 CT-1 CT-2 CT-3 CT-4 CT-5 CT-6 CT-7 CT-8 CT-9 CT-10 CT-11 CT-12 CT-13 CT-14 CT-15 CT-16 CT-17 CT-18 CT-19 CT-20 CT-21 CT-22 CT-23 CT-24 CT-25 CT-26 CT-27 CT-28 CT-29 CT-30 LC-22 LC-23 LC-24 LC-25 LC-26 LC-27 LC-28 LC-29 LC-30
Rb
Zn
Fe
Ba
Ti
Ca
Sr
Mn
K
76.29 77.69 70.48 59.28 76.96 70.84 75.71 59.99 78.33 70.67 61.15 74.41 75.95 77.93 79.82 78.29 71.53 64.33 76.89 72.33 73.12 40.87 45.32 44.09 48.12 40.42 42.29 48.26 40.77 33.74 40.76 41.14 40.71 43.88 49.20 41.53 38.88 42.27 45.02 39.28 39.35 37.13 40.92 35.75 37.82 44.76 37.30 34.46 36.03 30.71 39.38 60.71 56.13 61.02 62.73 61.69 67.19 58.89 67.27 62.05
109.77 114.91 97.70 101.79 133.92 118.90 110.97 100.24 108.21 113.14 103.21 117.96 111.07 132.45 151.91 144.53 96.20 106.25 132.50 118.84 117.71 127.72 137.92 125.40 142.14 141.74 138.59 133.06 114.53 138.67 115.18 127.08 122.03 132.90 149.74 130.78 125.75 135.38 141.45 134.33 123.69 117.54 137.81 113.85 129.72 100.33 133.35 122.38 127.83 97.72 119.88 138.11 137.95 108.26 108.50 127.23 141.49 81.34 158.96 112.34
40397.55 41970.02 38356.85 38964.09 39081.18 36029.65 41398.98 40587.52 41121.71 38867.51 38677.11 41194.20 41468.87 42670.17 39764.36 44143.34 33832.03 33517.05 39810.61 40250.09 39043.77 65808.95 66372.83 58920.74 72387.91 63007.86 63309.18 60849.38 64333.48 59057.49 61479.02 61859.01 63908.66 67428.92 61182.62 64616.31 64873.07 64670.64 66669.53 60444.03 61523.46 57474.30 60410.27 59686.70 63231.43 46075.21 60924.70 61350.98 61654.29 60482.91 63765.00 39468.72 39029.79 38460.79 38484.32 42237.84 44377.58 36222.63 44503.83 40625.40
1011.34 965.46 1092.68 1074.37 1330.62 1376.83 1320.50 1329.72 889.75 1235.36 1127.40 1451.47 1363.96 1184.89 1202.89 1050.07 1532.47 1330.68 1376.80 1157.19 1268.12 835.84 716.35 687.72 645.00 760.67 792.41 773.08 842.51 884.23 771.72 785.36 778.20 795.43 742.26 855.78 885.98 919.98 728.91 876.98 970.79 873.22 838.84 620.83 777.03 734.72 907.31 810.77 610.89 810.77 610.89 1033.92 1258.22 976.91 1101.39 1136.36 815.39 1042.68 768.08 1206.95
5997.32 6494.80 6758.15 8258.36 5967.04 6971.95 5420.46 7045.64 5421.59 6257.56 6054.89 7054.51 7371.97 6665.26 7198.11 6543.82 6802.35 4915.14 6458.20 5588.20 6783.73 12472.11 11404.18 10585.84 12638.38 9165.74 12424.44 11234.99 11652.80 11528.32 11735.39 11067.98 11734.67 12236.55 8985.04 11552.23 12300.75 11880.13 11230.99 10891.19 11713.19 11379.98 11725.37 11071.39 10573.39 6906.20 11348.57 11118.42 10882.73 10259.46 12641.02 5884.05 4735.56 6206.60 5702.71 5567.02 5744.22 5446.87 5533.67 6119.56
16451.49 15816.92 16913.52 24388.20 16369.87 19395.91 13667.40 18287.82 14599.94 13465.44 15011.18 17141.72 16943.47 16286.82 20535.62 16844.84 17233.21 14331.85 15038.71 15099.56 18257.47 42213.23 34881.64 31564.96 39717.04 31359.11 40809.88 36085.11 37914.86 36629.29 34555.31 36536.27 36101.39 37807.02 25055.97 36574.34 38217.02 36063.51 34418.28 35043.70 38991.37 35369.00 39043.41 39959.21 36102.63 22479.13 38546.88 36809.46 32710.98 32978.96 40830.09 12667.56 11423.43 13579.93 15073.62 17462.28 12600.48 15989.13 12428.35 18280.58
880.91 736.02 811.52 797.12 814.04 820.58 779.11 952.84 729.01 864.52 830.97 890.17 830.07 810.88 766.76 882.66 818.54 785.06 866.60 898.33 856.43 1176.08 1107.65 938.51 1022.87 1009.46 1073.97 1034.90 1145.63 986.61 958.37 1065.97 1125.43 1136.08 917.53 1106.88 1110.94 1139.54 1194.62 1053.25 1165.45 888.63 966.15 1013.39 980.02 459.48 960.50 958.98 953.95 932.17 959.96 613.47 772.20 745.37 735.23 766.10 487.65 701.45 485.46 745.86
1071.93 1264.99 1193.94 1555.37 1128.60 1406.90 1126.86 1427.35 1108.96 1190.83 1057.03 1293.06 1242.94 1347.25 1677.13 1329.67 1082.93 1093.90 1251.56 1179.35 1192.64 1602.30 1646.19 1538.43 1802.50 1569.05 1438.29 1475.93 1504.66 1408.29 1569.43 1449.97 1462.85 1458.40 1599.20 1464.43 1437.09 1559.57 1543.75 1386.68 1409.73 1380.84 1465.92 1591.68 1583.09 1246.67 1532.20 1660.77 1637.38 1458.24 1667.86 1415.48 1591.97 1351.18 1303.20 1743.37 1685.58 1359.72 1654.67 1204.74
15893.94 18800.71 18782.63 21746.66 15959.17 21338.96 14462.74 16975.44 15716.92 16851.00 14866.53 20773.89 20896.46 17611.28 20813.94 17379.69 21230.57 12074.59 15145.14 14528.40 19514.61 12905.59 15139.49 11181.60 16064.27 9610.92 14326.38 14514.42 11533.11 9665.93 10902.53 12659.74 12220.75 12003.06 11545.20 13280.21 12129.37 13295.59 11636.70 12670.37 12082.14 11620.00 12893.26 13145.58 11872.27 16996.34 13290.96 12245.74 11921.54 10056.42 13698.93 16503.09 11350.88 17465.19 15709.12 15983.61 15734.09 14420.63 14864.91 19289.95
characterizing their geochemical composition (Emmitt et al., 2018). Portable querns were commonly utilized by the Prehispanic inhabitants of Tenerife, and these artifacts remained still in use by the population living in rural areas until a few decades ago. Grinding stones are built from rocks, usually of vesicular nature, resistant enough to allow molturation of grains, but generally of light weight to facilitate manual transport. Therefore, vesicular scoria blocks emitted by volcanic cones constitute an excellent raw material for manufacturing these tools. In Las Cañadas del Teide there are several volcanoes that
emitted material that fulfill these two conditions. In this study we have identified two major workspaces for manufacturing of grinding stones in Las Cañadas. The criteria followed to consider an archaeological site as a place in which grinding stones were manufactured include the presence of several lithic artifacts of foreign material (as shown in Fig. 3b) used in the manufacturing process, as well as the observation of many half-done or unfinished end products, chips or flakes of vacuolar rocks, as shown in Fig. 3a. The two workspaces identified fulfilled these criteria, and in both sites, we also found
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Table 2 Mean values of different elements in the samples of raw material from Cruz de Tea and Los Corrales.
Zirconium Strontium Rubidium Zinc Copper Nickel Iron Manganese Barium Niobium Bismuth Chrome Vanadium Titanium Calcium Kalium Aluminium Sulphur Magnesium Silicon Rubidium × 1000/calcium Rubidium × 1000/iron Rubidium × 1000/titanium
Cruz de Tea
Los Corrales
444 ± 66 1018 ± 137 40.7 ± 4.3 128 ± 12.0 30.9 ± 43.6 79.3 ± 70.6 62260 ± 4310 1518 ± 111 800 ± 89 111 ± 11 9.0 ± 5.4 101.2 ± 19.2 218 ± 28.0 11210 ± 1189 35850 ± 4247 12570 ± 1688 47190 ± 13850 895 ± 409 7827 ± 3844 227600 ± 17600 1.16 ± 0.26 95% CI = 0.65–1.67 0.66 ± 0.085 95% CI = 0.49–0.83
653 ± 78 7905 ± 106 69.3 ± 7.4 119 ± 17.9 31.9 ± 38.2 79.1 ± 45.2 39820 ± 2653 1318 ± 201 1167 ± 186 144 ± 14 23.0 ± 4.3 92.1 ± 19.3 132 ± 24 6232 ± 779 16050 ± 2679 17090 ± 2743 47470 ± 14050 2606 ± 3017 5560 ± 2550 234100 ± 25290 4.14 ± 0.72 95% CI = 2.73–5.55 1.75 ± 0.19 95% CI = 1.38–2.12
3.69 ± 0.73 95% CI = 2.26–5.12
11.25 ± 1.50 95% CI = 8.31–14.19
remains of prehispanic pottery. In addition C14 dating of bone remains (fauna) dug out in two nearby located dwelling places revealed an antiquity of 800–650 BP, therefore, fully corresponding to the prehispanic period. Prehispanic remains in Las Cañadas del Teide are widespread. Hundreds of dwelling places have been identified. Probably, during many centuries (C14 dating of human remains range from 400 to 1600 BP, Arnay-de-la-Rosa et al., 2011), at least seasonal occupation took place, and after the conquest, many Guanches probably fled to Las Cañadas and hid themselves in the many caves among the lava blocks. In fact, travelers who arrived at Tenerife towards the end of the 16th century (nearly 100 years after the conquest) warned about the presence of “savages” in the Central highlands (Aznar Vallejo, 1984). Vestiges of dwelling places are observed in the pumice plains bordering the lava flows, in the slopes of volcanic cones, within the lava flows in the spaces formed between massive lava blocks, and in caves. In all these places pottery remains are clearly observable, together with obsidian and other lithic artifacts, and, sometimes, fragmented or complete portable grinding stones. But, in contrast with the many dwelling places, only two major sites in which grinding stones were produced have been identified. The discovery of working places in which grinding stones were manufactured, and the fact that this occurred only in two volcanic cones of the 19 surveyed ones constitutes, by itself, an important finding. Indeed, it suggests that there was a certain kind of specialization in the manufacturing process of these tools: the Guanches did not (or at least usually did not) manufacture the grinding stones they needed utilizing the raw material located near their dwelling places, but acquired these tools from people who were specialized in their production in the aforementioned workspaces. A same conclusion was also suggested in relation with the production of obsidian tools (Hernández and Galván, 2008). The next research question was to characterize the raw material employed, since, by this way, it is possible to assign any finding of a new grinding stone to any of the working places- or, eventually, to any other unknown working place outside Las Cañadas. This information
T = 11.25; p < 0.001 T = 7.48; p < 0.001 T = 18.28; p < 0.001 T = 2.39; p = 0.021 Z = 0.22; p = 0.82 (NS) T = 0.02; p = 0.99 (NS) T = 24.29; p < 0.001 T = 4.80; p < 0.001 T = 9.76; p < 0.001 T = 9.81; p < 0.001 T = 11.01; p < 0.001 T = 1.82; p = 0.07 (NS) T = 12.76; p < 0.001 T = 19.18; p < 0.001 T = 21.59; p < 0.001 T = 7.69; p < 0.001 T = 0.08; p = 0.94 (NS) Z = 4.86; p < 0.001 T = 2.69; p = 0.009 T = 1.14; p = 0.26 (NS) T = 23.16; p < 0.001 (Z = 6.65; p < 0.001) T = 28.52; p < 0.001 (Z = 6.65; p < 0.001) T = 24.95; p < 0.001 (Z = 6.65; p < 0.001)
would allow inference about trade routes and migration of the ancient inhabitants of the island within the Cañadas Caldera. In Tenerife there are many different volcanic rocks, which have been fully characterized both by petrographic and/or chemical analysis. Indeed, the island probably formed in three phases, during at least 11 million years. The so called Las Cañadas Volcano was the youngest of these phases (about 3.5 million years ago, Ancochea et al., 1999). Once formed, the Cañadas volcano suffered important remodeling, with several episodes of formation of stratovolcanoes and collapse events (Ancochea et al, 1990), before the final emergence (about 150 thousand years ago) of the Teide/Pico Viejo massif, that filled the northwestern part of the Caldera and defines the current landscape of the area (Ancochea et al., 1999). As a result of this turbulent past, several kinds of volcanic rocks, both trachyte and phonolite or mainly basalt or basanite/tephrite that, logically, show clear-cut differences in their chemical composition, are present in the current caldera. But in addition, recent “minor” volcanic activity has taken place. Several eruptions have occurred in the few last millennia, partially covering with their lava fields the previous structures (Carracedo, 2006). Pryroclastic cones and some pumice domes (obviously not considered in this study, since pumice does not allow the production of a suitable grinding stone) account for the most recent volcanic episodes (Ablay et al., 1995). These episodes probably derive from the same magmatic camera, although at different stages of differentiation. Therefore, differences in composition of the pyroclastic emissions of the recent volcanic cones are more subtle. Los Corrales and Cruz de Tea belong to these last volcanic eruptions. We looked for criteria that allow discrimination between the material produced in Los Corrales and Cruz de Tea. Vesicular structure of the raw material hampers the possibility to obtain adequate slices to perform a petrographic analysis; moreover the aphanitic nature of the rocks impede the identification of any crystal with the bare eye or magnification glass. Therefore, elemental composition analysis was the preferred method. This can be done with dispersive X-ray fluorescence analysis, that allows determination of chemical composition of relatively big samples, and, especially, because it is a non-destructive
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Fig. 6. Correlation between rubidium and calcium (Fig. 6a) and rubidium and iron (Fig. 6b), clearly showing marked differences between Los Corrales and Cruz de Tea raw material.
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Fig. 7. Box-and-whisker plots showing the marked differences between Cruz de Tea and Los Corrales regarding the indices Rb/Ca, Rb/Fe and Rb/Ti.
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Fig. 8. Correlation between the Rb/Ca and Rb/Fe indices, that clearly separate the samples from Cruz de Tea from those from Los Corrales.
Fig. 9. Box-and-whisker plots showing the marked differences between Cruz de Tea and Los Corrales regarding the discriminant function.
method that permits simultaneous determination of many elements (Shackley, 2011). This method, that has been widely used in the analysis of archaeological remains (Liritzis and Zacharias, 2011; Richards, 2019), especially obsidian tools (as excellently compiled by Speakman and Shackley, 2013), was also employed in this study. Logically –and following published suggestions (Liritzis and
Zacharias,2011), we did not include in this study elements with very low concentrations, around the limit of detection. So, we considered only about 20 elements that are present in reliable, amounts in the rocks analyzed, and we compared the concentrations of these elements among the two sites. In Table 2 we show that in the univariate analysis there are marked differences in the concentrations of some elements. 11
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Application of the function to these precisely located material fully assign its composition to each of the two manufacturing centers, confirming its validity. In order to test the practical value of the several indices and discriminant function obtained, we have analyzed 12 complete or fragmented rotary querns, some of them found during excavation of dwelling places, some others found during prospections in several parts of Tenerife, and also some querns housed at the Laboratory of Prehistory of our University with only a vague indication of the place they were found. Results are shown in Table 4. Interestingly, those found in the excavation of the dwelling place of Chasogo, another one with an imprecise label “Pico Viejo” and a last one found at a site named “Los Frontones” located in the southwestern slopes of Tenerife, at about 1100 m over sea level (see map, Fig. 10) seem to have been manufactured in Cruz de Tea, as was also the case for two other samples dug out during the excavation of a dwelling place near Cruz de Tea, and also the case of a quern housed at the Laboratory of Prehistory, labelled “Teide Viejo west”. The theoretical possibility exists that these querns were produced using (not still analyzed) scoria of any other volcanic cone, but what we can assure is that they were not manufactured using material from Los Corrales. On the other hand, the vaguely labeled quern “near Los Tomillos”, with a positive value of the discriminant function (but slightly below the 95% confidence interval for Los Corrales) was possibly manufactured in Los Corrales, but surely not in Cruz de Tea. Some other querns, as shown in Table 4, from “Las Cañadas” or from the southern coast (Las Galletas) showed elemental compositions and a value of the discriminant function that are outside the confidence intervals of both the material from Cruz de Tea and Los Corrales, suggesting that other sources of raw material must have been employed for the production of some querns. Therefore, in this study we have added another example about the usefulness of XRF methodology in analyzing archaeological material. We have fully characterized chemical composition of the raw material of two major workspaces in which grinding stones were manufactured and used the data to perform a discriminant function that allows a clear-cut identification of each of the two sites. Application of this function served to assess provenance of rotary querns found in the excavation of precisely located dwelling places, and also of some querns found at more or less vaguely labeled distant sites, although elemental composition of some other querns suggest that other sources of raw material were also utilized. Another important conclusion of this study is just the finding of only two major workspaces in the highlands of Tenerife in which grinding stones were produced, strongly suggesting that manufacturing of these artifacts was a specialized procedure. This is an archaeological finding relevant for the interpretation of the style of life and socio-economical conditions of the ancient Guanches.
Table 3 Values of the discriminant function when it was applied to new samples (portable querns or fragments found near the wokspaces, not included in the discriminant function. Cruz de Tea Cruz de Tea Los Corrales Los Corrales Los Corrales Los Corrales Los Corrales Los Corrales Los Corrales Los Corrales Los Corrales
−4.96472 −5.12885 5.05556 5.21092 4.74531 7.60082 6.57642 4.02482 2.64609 3.79048 2.60295
This is the case of rubidium, titanium, calcium or iron, with t-values around 20. The raw material from Cruz de Tea shows by far higher contents of titanium, iron and calcium than that of Los Corrales, which, on the other hand, contains much more rubidium. Silicon and aluminium contents are similar in the rocks of both places, and magnesium is slightly higher among the raw material from Cruz de Tea. The proportion of mafic minerals is more abundant in the basanite scoria from Cruz de Tea than in the phonotephrite/benmoreite rocks of Los Corrales, thus explaining the significantly higher content of magnesium, and, especially, iron observed in the rocks from Cruz de Tea. The differences in calcium can be explained on the possible existence of more intermediate plagioclases among the rocks of Cruz de Tea. The relatively recent volcanoes of the western slope of Pico Viejo show indeed a relative abundance in calcium plagioclases and iron and titaniumcontaining clinopyroxenes (Ablay et al,1998; Bravo, 1962). Showing lower rubidium, but higher titanium, iron and calcium, the differences of the ratios Rb/Fe, Rb/Ti, or Rb/Ca are even more marked among the two archaeological sites, something that becomes clearly illustrated in Fig. 7a–c. Next, we performed a stepwise discriminant function analysis introducing the three mentioned indices as independent variables. Only the Rb/Fe and Rb/Ca ratios were selected (by the SPSS program), yielding a discriminant function that clearly separates both sites (Fig. 9). Moreover, mean and 95% confidence intervals of the punctuations obtained when the discriminant function was applied to each of the samples show very different, not overlapping values, that allow a clear-cut distinction between the materials of the two sites, as is also clearly shown in Fig. 9. Lastly, we applied this function to the composition of several pieces that constitute the test group, destined to confirm the reproducibility of the discriminant function using samples not included in its calculation.
Table 4 Values of the Rb/Ca, Rb/Fe, Rb/Ti indices and of the punctuation obtained when the discriminant function was applied to querns found at diverse locations. For comparative purposes we also provide the confidence intervals of the mentioned indices and discriminant function punctuations derived from the analysis of the raw material from Cruz de Tea and Los Corrales.
Chasogo-1 Chasogo-2 Chasogo-3 Pico Viejo Piece number 32 Cruz de Tea-1 Cruz de Tea-2 Piece number 18 (Las Cañadas) Las Galletas Los Frontones “Near Los Tomillos” Pico Viejo West Raw material Cruz de Tea Raw material Los Corrales
Excavation Excavation Excavation Lab Prehistory Lab Prehistory Excavation Excavation Lab Prehistory Prospection Prospection Lab Prehistory Lab Prehistory
Rb/Ca
Rb/Fe
Rb/Ti
Discriminant function
Provenance
0.97 1.16 1.07 0.94 2.72 0.68 0.77 2.12 0.19 0.94 3.24 0.62 0.65–1.67 2.73–5.55
0.51 0.68 0.71 0.52 1.12 0.44 0.43 0.94 0.16 0.66 1.32 0.38 0.49–0.83 1.38–2.12
2.78 3.75 3.65 2.85 7.19 2.41 2.23 6.67 0.83 3.49 9.36 1.84 2.62–5.12 8.31–14.19
−5.04 −4.03 −3.97 −5.15 −0.41 −5.69 −5.65 −1.87 −7.49 −4.35 +1.02 −6.02 −2.39 to −5.93 1.69–6.64
Cruz de Tea Cruz de Tea Cruz de Tea Cruz de Tea Unknown Cruz de Tea Cruz de Tea Unknown Unknown Cruz de Tea Corrales? Cruz de Tea?
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Fig. 10. Map showing the central and southern part of Tenerife. In this map one can see the sites in which the querns were found (circles), and also the two workspaces (Cruz de Tea and Los Corrales).
Declaration of Competing Interest
Phonolite lineages of the Teide-Pico Viejo Volcanic complex, Tenerife, Canary islands. J. Petrol. 39, 905–936. Ancochea, E., Fúster, J.M., Ibarrola, E., Cendrero, A., Coello, J., Hernán, F., Cantagrel, J.M., Jamond, C., 1990. Volcanic evolution of the island of Tenerife (Canary Islands) in the light of new K-Ar data. J. Volcanol. Geothermal Res. 44, 231–249. Ancochea, E., Huertas, M.J., Fúster, J.M., Coello, J., Hernán, F., Cantagrel, J.M., Arnaud, N., Ibarrola, E., Cendrero, A., Jamond, C., 1999. Evolution of the Cañadas edifice and its implications for the origin of the Cañadas Caldera (Tenerife, Canary Islands). J. Volcanol. Geothermal Res. 88, 177–199. Antonelli, F., Lazzarini, L., 2010. Mediterranean trade of the most widespread Roman volcanic millstones from Italy and petrochemical markers of their raw materials. J. Archaeol. Sci. 37 (9), 2081–2092. Anguita, F., Màrquez, A. Castiñeiras, P., Hernán, F.., 2002. Los volcanes de Canarias. Ed. Rueda. Madrid. Arnay-de-la-Rosa, M., González-Reimers, E., 2006. “El poblamiento prehistórico del Parque Nacional del Teide”. In: Carracedo, J.C. (Ed). Los volcanes del Parque Nacional del Teide 314–341. Organismo Autónomo Parques Nacionales, Ministerio de Medio Ambiente. Madrid, pp. 314–341. Arnay-de-la-Rosa, M., González-Reimers, E., Yanes, Y., Romanek, C.S., Noakes, J.E., Galindo-Martín, L., 2011. Paleonutritional and Paleodietary survey on prehistoric humans from Las Cañadas del Teide (Tenerife, Canary Islands) based on chemical and histological analysis of bone. J. Archaeol. Sci. 38, 884–895. Aznar Vallejo, E. 1984. El capítulo de Canarias en el Islario de André Thevet. Coloquios de Historia Canario-Americana (6, T2): pp 829–862. Bravo, T., 1962. El circo de Las Cañadas y sus dependencias. Boletín de la Real Sociedad Española de Historia Natural 40, 93–108. Campbell, S., Healey, E., 2018. Diversity in obsidian use in the prehistoric and early historic Middle East. Quarter. Int. 468 (A), 141–154. https://doi.org/10.1016/j. quaint.2017.09.023. Carracedo, J.C., 2006. El Volcán Teide. Servicio de Publicaciones de la Caja General de Ahorros de Canarias, Santa Cruz de Tenerife. Diego Cuscoy, L., 2008. Los Guanches. Vida y cultura del primitivo habitante de Tenerife. Instituto de Estudios Canarios, La Laguna-Tenerife. Espinosa, A., 1980 [1590]. Del origen y milagros de la Santa Imagen de Nuestra Señora de Candelaria, que apareció en la isla de Tenerife con la descripción de esta isla. Introducción y notas de Alejandro Cioranescu. Goya Ediciones, Santa Cruz de Tenerife. Emmitt, J.J., McAlister, A.J., Phillipps, R.S., Holdaway, S.J., 2018. Sourcing without
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. Acknowledgments The authors are thankful to the direction and rangers of the Parque Nacional del Teide, as well as the SEGAI staff (University of La Laguna) for their support and suggestions during the preparations of this report. The authors also acknowledge the thoughtful and encouraging comments of the anonymous reviewers of the manuscript. Financial disclosure This project was partially financed by the “MINECO_FEDER” (HAR 2015-68323P). Appendix A. Supplementary data Supplementary data to this article can be found online at https:// doi.org/10.1016/j.jasrep.2019.102048. References Ablay, G.J., Ernst, G.G.J., Martí, J., Spark, R.S.J., 1995. The subplinian eruption of Montaña Blanca, Tenerife. Bull. Volcanol. 57, 337–355. Ablay, G.J., Carroll, M.R., Palmer, M.R., Martí, J., Sparks, R.S.J., 1998. Basanite-
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M. Arnay-de-la-Rosa, et al. sources: measuring ceramic variability with pXRF. J. Archaeolog. Sci.: Rep. 17, 422–432. Frahm, E., 2014. Characterizing obsidian sources with portable XRF: accuracy, reproducibility, and field relationships in a case study from. Armenia J. Archaeol. Sci. 49, 105–112. https://doi.org/10.1016/j.jas.2014.05.003. Frutoso, G.,2004 [1590]. Descripción de las Islas Canarias, Capítulos 9 al 20 del libro I de Saudades da Terra. Centro de la Cultura Popular Canaria. Santa Cruz de Tenerife. Gluhak, T.M., Hofmeister, W., 2009. Roman lava quarries in the Eifel region (Germany): geochemical data for millstone provenance studies. J. Archaeol. Sci. 36 (8), 1774–1782. Hernández, C.M., Galván, B., 2008. Estudio geoquímico de dos centros de roducciónde obsidianas en la prehistoria de Tenerife: el Tabonal de los Guanches (Icod de los Vinos) y el Tabonal Negro (Las Cañadas). Trabajos de Prehistoria 62, 151–168. Liritzis I, Zacharias N.,2011. Portable XRF of Archaeological Artifacts: current research, potentials, and limitations. In MS Shackley (ed) X-ray fluoresbece Spectrometry (XRF) in Geoarchaeology, pag 109-142 (chapter 6) DOI: 10.1007/978-1-4419-68869_6 Springer Science + Business Media, LLC 2011.
Mangas, J., Rodríguez, A.C., Martín, E., Francisco, I., 2008. Canteras aborígenes de molinos de mano en la isla de Gran Canaria (España): caracterización petrológica de tobas de lapilli. Geo-temas 10, 1301–1304. Naranjo-Mayor, Y., Francisco-Ortega, I., Rodríguez-Rodríguez, A., 2016. The quarry and workshop of Barranco Cardones (Gran Canaria, Canary Islands): Basalt quern production using stone tools. J. Lithic Studies 3. https://doi.org/10.2218/jls.v3i2.1779. Richards, M.J., 2019. Realising the potentialof portable XRF for the geochemical classification ofvolcanic rock types. J. Archaeol. Sci. 105, 31–45. Serra Rafols, E., Diego Cuscoy, L., 1950. Los molinos de mano. Rev. Historia 92, 384–397. Speakman, R.J., Shackley, M.S., 2013. Silo science and portable XRF in Archaeology: a response to Frahm. J. Archaeol. Sci. 40, 1435–1443. Shackley, M.S., 2011. An introduction to X-ray fluorescence (XRF) analysis in archaeology. In: Shackley, M.S. (Ed.), X-ray fluorescence Spectrometry (XRF) in Geoarchaeology. Springer, New York, pp. 7–44 pag 109–142 (chapter 6). Szilagy, V., Gyarmati, J., Toth, M., Taubald, H., 2012. Petro-mineralogy and geochemistry as tools of provenance analysis on archaeological pottery: study of Inka period ceramics of Paria. J. South America Earth Sci. 36, 1–17.
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Identification of prehispanic rotary querns production areas in Las Cañadas del Teide (Tenerife, Canary Islands, Spain)
T
Matilde Arnay-de-la-Rosaa,b, , Emilio González-Reimersa,b, Efraín Marrero-Salasa,b, Carlos García-Ávilaa,b, Constantino Criado-Hernándeza,b, Alberto Lacave-Hernándeza,b, Rebeca González-Fernándeza,c, Ithaisa Abreu-Hernándeza,b ⁎
a
Universidad de La Laguna, Tenerife, Canary Islands, Spain Researchers adscribed to the MINECO-FEDER project “Guanches y Europeos en las Cañadas del Teide, Ocupación, producción y comunicación”, Spain c Servicio de Apoyo a Criminalística Forense, Servicio General de Apoyo a la Investigación (SEGAI) and Laboratorio de Biología del Desarrollo, UD de Bioquímica y Biología Molecular, Universidad de La Laguna, Tenerife, Canary Islands, Spain b
ARTICLE INFO
ABSTRACT
Keywords: Grinding stone Portable querns Guanches Tenerife Las Cañadas del Teide portable X ray fluorescence
Portable querns were commonly used by the prehispanic population of Tenerife. In Tenerife, these instruments are built on rocks, usually of vesicular nature –such as those emitted as scoria by pyroclastic cones-, resistant enough to allow molturation of grains, but generally of light weight to facilitate manual transport. In the highlands of Tenerife there are many archaeological remains of the prehispanic population (Guanches). After systematic survey of 19 pyroclastic cones present in the highlands, only in 2 we found remains of workspaces in which grinding stones were manufactured. This finding suggests that production of grinding stones was a specialized task, and that, instead of producing them as needed, the Guanches acquired them in these two production sites. Chemical composition of 30 samples of the raw material used in each of these two wokspaces showed differences in composition big enough to perform a discriminant analysis that allowed a clear-cut separation of both workspaces. Indeed, the function was applied to 13 pieces or fragment of pieces found about 500 m around the workspaces, fully confirming the validity and usefulness of the function obtained. In addition, we also examined 12 rotary querns (complete or fragmented) found at diverse locations of the island, currently housed at the laboratory of the Department of Prehistory of the University of La Laguna (Tenerife). The application of the discriminant function to these samples allowed the identification of the provenance of 9 cases. Therefore pXRF analysis may be useful in provenance studies of rotary querns, although our data also suggest that not all the rotary querns were manufactured in the workspaces described in this study.
1. Introduction Tenerife is the largest island of the Canary Archipelago, sharing with the remaining islands a turbulent geological history. After many submarine eruptions, the island finally emerged about 7.5–11.5 million years ago (Ancochea et al., 1990; Anguita et al., 2002). Continuous volcanic activity with repeated eruptions followed by several massive gravitational collapses have contributed to shape the current landscape of the island, with a central volcanic caldera 16 km in diameter (Las Cañadas), towered by the Teide peak (3718 m height). A range with some peaks reaching 2000–2400 m over sea level extends from the center to the northeastern part of the island (Cordillera Dorsal). On the other side, some relatively recent volcanoes, reaching 1500–1800 m over sea level prolong the central highlands to the northwest.
⁎
Therefore, a northern slope and a southern slope are clearly defined in the island, separated by the Teide/Cañadas volcanic complex, the northwestern volcanoes, and the Cordillera Dorsal. Located at 28th North, in front of the Sahara desert, two main factors have a decisive influence on the climatic conditions of the island: the vicinity of the Sahara desert and the northeastern trade winds, which usually blow below 1300–1800 m altitude. Therefore, clouds associated with the trade winds stagnate in the northern slopes, providing rain and moisture to this part of the island. In contrast, arid conditions predominate in the southern slopes. The central highlands of Tenerife (mean altitude of the Cañadas caldera is about 2000–2300 m over sea level) constitute a special environment, with sparse vegetation, many lava flows, and rough climatic conditions. Visited by the inhabitants of the island during centuries or
Corresponding author at: Dpt. de Geografía e Historia, Universidad de La Laguna, Tenerife, Canary Islands, Spain. E-mail address: [email protected] (M. Arnay-de-la-Rosa).
https://doi.org/10.1016/j.jasrep.2019.102048 Received 20 January 2019; Received in revised form 14 October 2019; Accepted 15 October 2019 2352-409X/ © 2019 Elsevier Ltd. All rights reserved.
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Fig. 1. Prehispanic portable rotary quern found near Cruz de Tea.
individuals, buried following the prehispanic ritual, with an antiquity dating from the 16th and even 17th centuries, nearly 200 years after Spanish conquest. These individuals were buried in the same caves that harbor other corpses with an antiquity of 900–1100 BP (Arnay-de-laRosa et al., 2011). In Las Cañadas there are also other burial caves containing skeletons with an antiquity of 1600 BP. Therefore, the central highlands were inhabited by the prehispanic people (Guanches) either temporarily or permanently during at least 1200 years, something attested by the many archaeological remains found in this area. Among the several kinds of archaeological remains observed in Las Cañadas, grinding stones, especially rotary querns, are quite abundant (Diego Cuscoy, 2008). Rotary querns were usually employed by the prehispanic inhabitants of the Canary Islands, and far beyond the conquest, by the modern rural population. In contrast with Gran Canaria, in which the main raw material destined to the production of these artifacts was lapilli tuff (Mangas et al., 2008), and, less frequently, basalt, extracted from vertical basaltic walls (Naranjo-Mayor et al., 2016), in Tenerife, rotary querns were manufactured in diverse porous magmatic rocks (Fig. 1), that can be found in the volcanic landscape of the Island, especially in cinder cones with gross pyroclastic blocks. Grinding stones have been found in many parts of Las Cañadas and also in coastal areas or medium height areas. It is unclear, however, whether the prehispanic population of the island manufactured the querns when needed, or if there were some kind of workspaces in which more or less specialized people manufactured these instruments. Only a report in 1950 describes a small “factory” in a place named Pedro Méndez (Serra Rafols and Diego Cuscoy, 1950).
millennia, as inferred from C-14 dating (Arnay-de-la-Rosa et al., 2011), geographical environment does not favor a steady settlement in an island in which there are northern coastal regions with a subtropical climate and enough rainfall that allows agriculture, and middle-height zones with dense forest, abundant rain and a mild temperate climate. However, in the central highlands there are many remains of the Prehispanic population, including burial caves containing more or less mummified corpses, and many dwelling areas with abundant pottery fragments and stony artifacts – especially obsidian tools (Arnay-de-laRosa and González-Reimers, 2006). The reasons by which this area was colonized before the Spanish conquest are not well understood. Possibly this central region constituted a place in which trade between North and South took place, and it was also a possibly place in which crossbreeding took place between goat (and to a lesser extent, sheep and pig) herds belonging to the population living in the northern and southern slopes. Probably these activities were performed in summer. Reports of chroniclers arriving with Spanish conquerors lend support to this seasonal migration to the highlands (Espinosa, 1980(1590)). Chroniclers also mention that dead were interred in the caves of the central highlands (Frutoso, 2004(1590)). In exceptional conditions of war or danger of captivity, the many caves and rough lava flows of Las Cañadas might constitute excellent places of refuge. These conditions did appear with the Spanish conquest. After cruel battles, some people fled into the mountains, in which the huge lava flows (mainly trachyte or phonolite) with enormous blocks and many caves offered a place where they could hide. Indeed, there are some C-14 dates of skeletal remains of partially mummified
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Fig. 2. Map indicating the two main manufacturing places (asterisks) and the other 17 pyroclastic areas surveyed (circles). 1 = Samara; 2 = La Botija; 3 = Montañeta Negra; 4 = Reventada; 5 = Adara; 6 = Tebite; 7 = Tamarco; 8 = Chircheros; 9 = Cruz de Tea (workspace); 10 = Chío; 11 = Volcán Ciego; 12 = La Corona; 13 = Volcán Escondido; 14 = Los Corrales (workspace); 15 = Los Tomillos; 16 = Mostaza; 17 = Arneas Negras; 18 = Cerrillar; 19 = Calderón.
(Las Cañadas caldera and the western slopes of Pico Viejo, Fig. 2). Most of these areas are scoria cones (cinder cones), besides Calderón (a small collapse caldera, surrounded by an extense area covered with scoria) and Tamarco (a spatter cone). Although in several of them some vestiges of manufacturing of grinding stones were observed (for instance, Los Chircheros, or Los Tomillos), only in two (Cruz de Tea/Chío and Los Corrales) there were data that allow to classify these sites as a production centers or areas, such as many partially manufactured artifacts, chips and fragments of raw material derived from the manufacturing process, and accumulation of tools employed in manufacturing the grinding stones (Fig. 3a and b).
However, detailed prospection of Las Cañadas del Teide carried up by ourselves during the last decades have led to the identification of two main areas of grinding stone manufacturing, namely Cruz de Tea and Los Corrales, quite away from each other. The first one is located in the slopes of Teide Viejo (western part of Las Cañadas) whereas the second one, in the northeastern corner of the Caldera (Fig. 2). Geological composition of these volcanic cones is similar, since they derive from a common evolved parent magma (Ablay et al., 1998), but there are subtle differences in composition of lava flows – more salic in the eastern part of the Caldera, more alkaline in the western slopes. In contrast with the only two major workspaces in which rotary querns were produced, several complete or fragmented pieces are found in the many dwelling areas distributed within the Caldera. It is therefore important to define the characteristics/composition of the raw material of these two major workspaces in which the grinding stones were produced. This allows the adscription of any of the complete pieces found in the dwelling areas to any of the two main production centers. This aids in reconstruction of trade and migration of the primitive inhabitants (Guanches) of Tenerife within the Cañadas caldera. Based on these considerations, the present study was performed in order to characterize the chemical composition of the raw material that served to manufacture the grinding stones in the two mentioned sites, looking for discriminant factors that allow a precise assignation of a given new piece to any of the two main sites of production described.
a) Cruz de Tea. – This is a complex volcanic area (Fig. 4), dominated by three volcanic systems: the Cruz de Tea mountain, The Montaña de Chío mountain, and an innominate third volcanic apparatus, located eastwards from Montaña de Chío, that erupted in the western slope of the stratovolcano Pico Viejo. The area is quite extense, since the workspaces are distributed along the southern slope of Montaña de Chío and its eastern prolongation, and Cruz de Tea. Two lava flows surround the mentioned volcanoes. One of them disrupts the possible union that existed between the lowest (most westernly located) slopes of Montaña de Chío, closing a pyroclastic plain at the southeast, and flowing down around the southern slope of Cruz de Tea; and another one, that flows down in the southern slope of Montaña de Chío (eastern prolongation). Both flows join together westwards, forming a plain, as commented. Both lava flows consists of rocky accumulations separated by relatively large pyroclastic plains. The main area of extraction of raw material is Cruz de Tea, a
2. Methods We surveyed 19 volcanic pyroclastic areas located in the highlands 3
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Fig. 3. Manufacturing place a) general overview; b) lithic instruments used in manufacturing process.
cinder cone formed by basanite/phonotephrite material (Carracedo, 2006), a composition also confirmed by the preliminary results derived from ICP-MS (inductively coupled mass spectrometry) analyses performed by members of our team (Criado-Hernández et al, unpublished data).
surrounds the southern slopes of Cruz de Tea. In this lava flow there are several places that were prepared to achieve more or less flattened areas, usually at the foot of big lava boulders (3–5 m height). In these flattened areas there are many remains of flakes, instruments, fragmented querns, and pottery fragments.
The workspace at Cruz de Tea occupies an area of about 40.000 square meters. Raw material (scoria blocks) was collected from the nearby located slopes of Cruz de Tea mountain and transported to the lapilli plains that partially covered the mentioned lava flow that
b) Los Corrales is a single volcano, in which several cones emerge (4 major ones) surrounding a relatively flat area, covered by gross pyroclastic blocks and some pumice (probably derived from a more recent eruption from Montaña Blanca). In this relatively flat area
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Fig. 4. Cruz de Tea pyroclastic cone.
whether the mineral composition of the 60 samples analyzed adapted to a normal distribution or not. After, we calculated differences in chemical composition of raw material from Cruz de Tea and Los Corrales. Content of some elements were by far higher in the samples from Cruz de Tea than in those from Los Corrales, whereas other elements showed just an opposite trend. Therefore we calculated the ratios between those elements that showed the highest concentrations and those that showed the lowest ones, and compared these ratios among the samples from the two workspaces. With those variables that showed maximal differences (including both single elements and ratios) we performed a stepwise discriminant function analysis, and, after, we applied this discriminant function to the 13 test samples found near the workspaces, in order to assess the reproducibility of the discriminant function. All these analyses were performed with the SPSS 15.0 program (Springfield, Ill, USA). In order to explore the utility of the discriminant function to assign a given rotary quern to any of the two manufacturing sites, we performed a post-hoc analysis of 12 terminated querns or fragments. These querns were currently housed at the laboratory of the Department of Prehistory of the University of La Laguna. In some cases a precise information about the place in which the instrument was recovered was available, but for some other querns only a vague reference was recorded (i.e. “Las Cañadas”, “near Los Tomillos” or “Pico Viejo”).
there are many evidences of partially manufactured specimens, together with many instruments of compact aphanitic stone. The manufacturing area measures approximately 25,000 square meters (Fig. 5). Raw material consists of benmoreite-phonotephrite (Carracedo, 2006) 2.1. Analytical procedure We used a portable energy dispersive X-ray fluorescence analyzer (XRF Thermo Scientific™ Niton™ XL3t GOLDD+; PANATEC SL, Madrid) that allows the identification of the elemental profile of a sample without destroying it. This is achieved by measuring the fluorescent Xray emitted from a sample after excitation by a primary X-ray source. Time of exposure to the X ray beam was 125 s in order to improve detection of light elements. The Analyzer possesses a 50 kV X-ray tube and a silver anode. The samples were measured in La Laguna University (SEGAI) by a direct shot, using the Mining Mode calibration. The area of the sample in contact with the analyzer was carefully cleansed with a brush prior to analysis. By this way, we determined the elemental composition of 30 samples from Cruz de Tea, and 30 samples from Los Corrales. These samples consist of chips and fragments of raw material derived from the manufacturing process. In addition we analyzed the mineral composition of 13 grinding stone fragments found near (in a radius of about 500 m) the two workspaces, as well as elemental composition of 12 querns found in several parts of Tenerife (see below).
3. Results Of the many elements analyzed, we discarded those whose concentrations were very low, around the detection limit. So, concentration of several elements, such as gold, uranium, silver, wolfram, tin, selenium, thorium and rare earths, among others, were not utilized in this
2.2. Statistics We performed a Kolmogorov-Smirnov test in order to discern 5
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Fig. 5. Los Corrales volcanic complex.
study. Crude data of those elements relevant for this study are shown in Table 1. As we can see in Table 2, raw material of the site Cruz de Tea has higher concentration of calcium, magnesium, iron and titanium than rocks from Los Corrales, probably indicating the presence of calciumcontaining plagioclase in higher amounts in Cruz de Tea than in Los Corrales, whereas iron and titanium may reflect the presence of clinopyroxene, a common component of basaltic/basanitic rocks in the Island. As shown in Fig. 6a and b, scattergrams clearly separate Cruz de Tea and Los Corrales. When we calculate the indices Rb/Ca, Rb/Fe, or Rb/Ti we observe that differences are even more marked (Fig. 7a–c). As shown in Fig. 8, the scattergram plotting the correlations between the indices Rb/Ca and Rb/Fe also shows that both sites are clearly identifiable, with no overlapping values. Considering that the values of the calculated indices are normally distributed within each group, the limits of the 95% confidence intervals for the three aforementioned indices are clearly different when the two sites are compared (Fig. 7a–c). In addition, we performed a stepwise discriminant function analysis, introducing the three indices mentioned before, given the marked differences obtained when Cruz de Tea and Los Corrales were compared. Only the indices Rb/Ca and Rb/Fe were selected, and the obtained discriminant function correctly classified the totality of the samples analysed. Discriminant function is 0.903 × Rb/Ca + 4.947 × Rb/Fe −8.457, and centroids are −4.164 for Cruz de Tea and +4.164 for Los Corrales, with standard deviations of 0.903 and 1.262, respectively, that yield confidence intervals of −2.394 to −5.934 for Cruz de Tea and +1.69 to +6.638 for Los Corrales (Fig. 9).
When we applied the discriminant function to 13 samples (flakes, fragments or complete or nearly complete portable querns) found near Cruz de Tea or Los Corrales we obtained the results shown in Table 3, that confirm the reproducibility of the discriminant function obtained. In Table 4 we show the elemental composition, the Rb/Fe, Rb/Ca and Rb/Ti ratios, and the punctuation obtained after applying the discriminant function, of the rotary querns used to test the usefulness of these calculations in the assessment of the provenance of these querns. In Fig. 10 we show the places in which these querns were found, and in Table 4 we also provide the likely provenance of the included querns. 4. Discussion In this study we have characterized the geochemical composition of two quarries in which portable querns were manufactured by the Guanches (the indigenous population of Tenerife). The methodology employed is similar to that reported by other researchers in other parts of the world. For instance, Gluhak and Hofmeister (2009) could identify several quarries in the Eifel region, that served for the production of huge amounts of millstones during the Roman period; Antonelli and Lazzarini (2010) analyzed several vesicular rocks from the Italian Peninsula and neighboring islands in order to identify the quarries that served for manufacturing of millstones and rotary querns and trade routes. In addition, XRF methodology has been successfully applied for identification of the quarries from which lithic material was extracted (for instance, Frahm, 2014; Campbell and Healey, 2018) or the places from which raw material for pottery production was obtained (for instance, Szilagy et al, 2012) or to ascertain variability of ceramic vessels,
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Table 1 Some crude data (direct measurements, in ppm) relevant for this study.
LC-1 LC-2 LC-3 LC-4 LC-5 LC-6 LC-7 LC-8 LC-9 LC-10 LC-11 LC-12 LC-13 LC-14 LC-15 LC-16 LC-17 LC-18 LC-19 LC-20 LC-21 CT-1 CT-2 CT-3 CT-4 CT-5 CT-6 CT-7 CT-8 CT-9 CT-10 CT-11 CT-12 CT-13 CT-14 CT-15 CT-16 CT-17 CT-18 CT-19 CT-20 CT-21 CT-22 CT-23 CT-24 CT-25 CT-26 CT-27 CT-28 CT-29 CT-30 LC-22 LC-23 LC-24 LC-25 LC-26 LC-27 LC-28 LC-29 LC-30
Rb
Zn
Fe
Ba
Ti
Ca
Sr
Mn
K
76.29 77.69 70.48 59.28 76.96 70.84 75.71 59.99 78.33 70.67 61.15 74.41 75.95 77.93 79.82 78.29 71.53 64.33 76.89 72.33 73.12 40.87 45.32 44.09 48.12 40.42 42.29 48.26 40.77 33.74 40.76 41.14 40.71 43.88 49.20 41.53 38.88 42.27 45.02 39.28 39.35 37.13 40.92 35.75 37.82 44.76 37.30 34.46 36.03 30.71 39.38 60.71 56.13 61.02 62.73 61.69 67.19 58.89 67.27 62.05
109.77 114.91 97.70 101.79 133.92 118.90 110.97 100.24 108.21 113.14 103.21 117.96 111.07 132.45 151.91 144.53 96.20 106.25 132.50 118.84 117.71 127.72 137.92 125.40 142.14 141.74 138.59 133.06 114.53 138.67 115.18 127.08 122.03 132.90 149.74 130.78 125.75 135.38 141.45 134.33 123.69 117.54 137.81 113.85 129.72 100.33 133.35 122.38 127.83 97.72 119.88 138.11 137.95 108.26 108.50 127.23 141.49 81.34 158.96 112.34
40397.55 41970.02 38356.85 38964.09 39081.18 36029.65 41398.98 40587.52 41121.71 38867.51 38677.11 41194.20 41468.87 42670.17 39764.36 44143.34 33832.03 33517.05 39810.61 40250.09 39043.77 65808.95 66372.83 58920.74 72387.91 63007.86 63309.18 60849.38 64333.48 59057.49 61479.02 61859.01 63908.66 67428.92 61182.62 64616.31 64873.07 64670.64 66669.53 60444.03 61523.46 57474.30 60410.27 59686.70 63231.43 46075.21 60924.70 61350.98 61654.29 60482.91 63765.00 39468.72 39029.79 38460.79 38484.32 42237.84 44377.58 36222.63 44503.83 40625.40
1011.34 965.46 1092.68 1074.37 1330.62 1376.83 1320.50 1329.72 889.75 1235.36 1127.40 1451.47 1363.96 1184.89 1202.89 1050.07 1532.47 1330.68 1376.80 1157.19 1268.12 835.84 716.35 687.72 645.00 760.67 792.41 773.08 842.51 884.23 771.72 785.36 778.20 795.43 742.26 855.78 885.98 919.98 728.91 876.98 970.79 873.22 838.84 620.83 777.03 734.72 907.31 810.77 610.89 810.77 610.89 1033.92 1258.22 976.91 1101.39 1136.36 815.39 1042.68 768.08 1206.95
5997.32 6494.80 6758.15 8258.36 5967.04 6971.95 5420.46 7045.64 5421.59 6257.56 6054.89 7054.51 7371.97 6665.26 7198.11 6543.82 6802.35 4915.14 6458.20 5588.20 6783.73 12472.11 11404.18 10585.84 12638.38 9165.74 12424.44 11234.99 11652.80 11528.32 11735.39 11067.98 11734.67 12236.55 8985.04 11552.23 12300.75 11880.13 11230.99 10891.19 11713.19 11379.98 11725.37 11071.39 10573.39 6906.20 11348.57 11118.42 10882.73 10259.46 12641.02 5884.05 4735.56 6206.60 5702.71 5567.02 5744.22 5446.87 5533.67 6119.56
16451.49 15816.92 16913.52 24388.20 16369.87 19395.91 13667.40 18287.82 14599.94 13465.44 15011.18 17141.72 16943.47 16286.82 20535.62 16844.84 17233.21 14331.85 15038.71 15099.56 18257.47 42213.23 34881.64 31564.96 39717.04 31359.11 40809.88 36085.11 37914.86 36629.29 34555.31 36536.27 36101.39 37807.02 25055.97 36574.34 38217.02 36063.51 34418.28 35043.70 38991.37 35369.00 39043.41 39959.21 36102.63 22479.13 38546.88 36809.46 32710.98 32978.96 40830.09 12667.56 11423.43 13579.93 15073.62 17462.28 12600.48 15989.13 12428.35 18280.58
880.91 736.02 811.52 797.12 814.04 820.58 779.11 952.84 729.01 864.52 830.97 890.17 830.07 810.88 766.76 882.66 818.54 785.06 866.60 898.33 856.43 1176.08 1107.65 938.51 1022.87 1009.46 1073.97 1034.90 1145.63 986.61 958.37 1065.97 1125.43 1136.08 917.53 1106.88 1110.94 1139.54 1194.62 1053.25 1165.45 888.63 966.15 1013.39 980.02 459.48 960.50 958.98 953.95 932.17 959.96 613.47 772.20 745.37 735.23 766.10 487.65 701.45 485.46 745.86
1071.93 1264.99 1193.94 1555.37 1128.60 1406.90 1126.86 1427.35 1108.96 1190.83 1057.03 1293.06 1242.94 1347.25 1677.13 1329.67 1082.93 1093.90 1251.56 1179.35 1192.64 1602.30 1646.19 1538.43 1802.50 1569.05 1438.29 1475.93 1504.66 1408.29 1569.43 1449.97 1462.85 1458.40 1599.20 1464.43 1437.09 1559.57 1543.75 1386.68 1409.73 1380.84 1465.92 1591.68 1583.09 1246.67 1532.20 1660.77 1637.38 1458.24 1667.86 1415.48 1591.97 1351.18 1303.20 1743.37 1685.58 1359.72 1654.67 1204.74
15893.94 18800.71 18782.63 21746.66 15959.17 21338.96 14462.74 16975.44 15716.92 16851.00 14866.53 20773.89 20896.46 17611.28 20813.94 17379.69 21230.57 12074.59 15145.14 14528.40 19514.61 12905.59 15139.49 11181.60 16064.27 9610.92 14326.38 14514.42 11533.11 9665.93 10902.53 12659.74 12220.75 12003.06 11545.20 13280.21 12129.37 13295.59 11636.70 12670.37 12082.14 11620.00 12893.26 13145.58 11872.27 16996.34 13290.96 12245.74 11921.54 10056.42 13698.93 16503.09 11350.88 17465.19 15709.12 15983.61 15734.09 14420.63 14864.91 19289.95
characterizing their geochemical composition (Emmitt et al., 2018). Portable querns were commonly utilized by the Prehispanic inhabitants of Tenerife, and these artifacts remained still in use by the population living in rural areas until a few decades ago. Grinding stones are built from rocks, usually of vesicular nature, resistant enough to allow molturation of grains, but generally of light weight to facilitate manual transport. Therefore, vesicular scoria blocks emitted by volcanic cones constitute an excellent raw material for manufacturing these tools. In Las Cañadas del Teide there are several volcanoes that
emitted material that fulfill these two conditions. In this study we have identified two major workspaces for manufacturing of grinding stones in Las Cañadas. The criteria followed to consider an archaeological site as a place in which grinding stones were manufactured include the presence of several lithic artifacts of foreign material (as shown in Fig. 3b) used in the manufacturing process, as well as the observation of many half-done or unfinished end products, chips or flakes of vacuolar rocks, as shown in Fig. 3a. The two workspaces identified fulfilled these criteria, and in both sites, we also found
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Table 2 Mean values of different elements in the samples of raw material from Cruz de Tea and Los Corrales.
Zirconium Strontium Rubidium Zinc Copper Nickel Iron Manganese Barium Niobium Bismuth Chrome Vanadium Titanium Calcium Kalium Aluminium Sulphur Magnesium Silicon Rubidium × 1000/calcium Rubidium × 1000/iron Rubidium × 1000/titanium
Cruz de Tea
Los Corrales
444 ± 66 1018 ± 137 40.7 ± 4.3 128 ± 12.0 30.9 ± 43.6 79.3 ± 70.6 62260 ± 4310 1518 ± 111 800 ± 89 111 ± 11 9.0 ± 5.4 101.2 ± 19.2 218 ± 28.0 11210 ± 1189 35850 ± 4247 12570 ± 1688 47190 ± 13850 895 ± 409 7827 ± 3844 227600 ± 17600 1.16 ± 0.26 95% CI = 0.65–1.67 0.66 ± 0.085 95% CI = 0.49–0.83
653 ± 78 7905 ± 106 69.3 ± 7.4 119 ± 17.9 31.9 ± 38.2 79.1 ± 45.2 39820 ± 2653 1318 ± 201 1167 ± 186 144 ± 14 23.0 ± 4.3 92.1 ± 19.3 132 ± 24 6232 ± 779 16050 ± 2679 17090 ± 2743 47470 ± 14050 2606 ± 3017 5560 ± 2550 234100 ± 25290 4.14 ± 0.72 95% CI = 2.73–5.55 1.75 ± 0.19 95% CI = 1.38–2.12
3.69 ± 0.73 95% CI = 2.26–5.12
11.25 ± 1.50 95% CI = 8.31–14.19
remains of prehispanic pottery. In addition C14 dating of bone remains (fauna) dug out in two nearby located dwelling places revealed an antiquity of 800–650 BP, therefore, fully corresponding to the prehispanic period. Prehispanic remains in Las Cañadas del Teide are widespread. Hundreds of dwelling places have been identified. Probably, during many centuries (C14 dating of human remains range from 400 to 1600 BP, Arnay-de-la-Rosa et al., 2011), at least seasonal occupation took place, and after the conquest, many Guanches probably fled to Las Cañadas and hid themselves in the many caves among the lava blocks. In fact, travelers who arrived at Tenerife towards the end of the 16th century (nearly 100 years after the conquest) warned about the presence of “savages” in the Central highlands (Aznar Vallejo, 1984). Vestiges of dwelling places are observed in the pumice plains bordering the lava flows, in the slopes of volcanic cones, within the lava flows in the spaces formed between massive lava blocks, and in caves. In all these places pottery remains are clearly observable, together with obsidian and other lithic artifacts, and, sometimes, fragmented or complete portable grinding stones. But, in contrast with the many dwelling places, only two major sites in which grinding stones were produced have been identified. The discovery of working places in which grinding stones were manufactured, and the fact that this occurred only in two volcanic cones of the 19 surveyed ones constitutes, by itself, an important finding. Indeed, it suggests that there was a certain kind of specialization in the manufacturing process of these tools: the Guanches did not (or at least usually did not) manufacture the grinding stones they needed utilizing the raw material located near their dwelling places, but acquired these tools from people who were specialized in their production in the aforementioned workspaces. A same conclusion was also suggested in relation with the production of obsidian tools (Hernández and Galván, 2008). The next research question was to characterize the raw material employed, since, by this way, it is possible to assign any finding of a new grinding stone to any of the working places- or, eventually, to any other unknown working place outside Las Cañadas. This information
T = 11.25; p < 0.001 T = 7.48; p < 0.001 T = 18.28; p < 0.001 T = 2.39; p = 0.021 Z = 0.22; p = 0.82 (NS) T = 0.02; p = 0.99 (NS) T = 24.29; p < 0.001 T = 4.80; p < 0.001 T = 9.76; p < 0.001 T = 9.81; p < 0.001 T = 11.01; p < 0.001 T = 1.82; p = 0.07 (NS) T = 12.76; p < 0.001 T = 19.18; p < 0.001 T = 21.59; p < 0.001 T = 7.69; p < 0.001 T = 0.08; p = 0.94 (NS) Z = 4.86; p < 0.001 T = 2.69; p = 0.009 T = 1.14; p = 0.26 (NS) T = 23.16; p < 0.001 (Z = 6.65; p < 0.001) T = 28.52; p < 0.001 (Z = 6.65; p < 0.001) T = 24.95; p < 0.001 (Z = 6.65; p < 0.001)
would allow inference about trade routes and migration of the ancient inhabitants of the island within the Cañadas Caldera. In Tenerife there are many different volcanic rocks, which have been fully characterized both by petrographic and/or chemical analysis. Indeed, the island probably formed in three phases, during at least 11 million years. The so called Las Cañadas Volcano was the youngest of these phases (about 3.5 million years ago, Ancochea et al., 1999). Once formed, the Cañadas volcano suffered important remodeling, with several episodes of formation of stratovolcanoes and collapse events (Ancochea et al, 1990), before the final emergence (about 150 thousand years ago) of the Teide/Pico Viejo massif, that filled the northwestern part of the Caldera and defines the current landscape of the area (Ancochea et al., 1999). As a result of this turbulent past, several kinds of volcanic rocks, both trachyte and phonolite or mainly basalt or basanite/tephrite that, logically, show clear-cut differences in their chemical composition, are present in the current caldera. But in addition, recent “minor” volcanic activity has taken place. Several eruptions have occurred in the few last millennia, partially covering with their lava fields the previous structures (Carracedo, 2006). Pryroclastic cones and some pumice domes (obviously not considered in this study, since pumice does not allow the production of a suitable grinding stone) account for the most recent volcanic episodes (Ablay et al., 1995). These episodes probably derive from the same magmatic camera, although at different stages of differentiation. Therefore, differences in composition of the pyroclastic emissions of the recent volcanic cones are more subtle. Los Corrales and Cruz de Tea belong to these last volcanic eruptions. We looked for criteria that allow discrimination between the material produced in Los Corrales and Cruz de Tea. Vesicular structure of the raw material hampers the possibility to obtain adequate slices to perform a petrographic analysis; moreover the aphanitic nature of the rocks impede the identification of any crystal with the bare eye or magnification glass. Therefore, elemental composition analysis was the preferred method. This can be done with dispersive X-ray fluorescence analysis, that allows determination of chemical composition of relatively big samples, and, especially, because it is a non-destructive
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Fig. 6. Correlation between rubidium and calcium (Fig. 6a) and rubidium and iron (Fig. 6b), clearly showing marked differences between Los Corrales and Cruz de Tea raw material.
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Fig. 7. Box-and-whisker plots showing the marked differences between Cruz de Tea and Los Corrales regarding the indices Rb/Ca, Rb/Fe and Rb/Ti.
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Fig. 8. Correlation between the Rb/Ca and Rb/Fe indices, that clearly separate the samples from Cruz de Tea from those from Los Corrales.
Fig. 9. Box-and-whisker plots showing the marked differences between Cruz de Tea and Los Corrales regarding the discriminant function.
method that permits simultaneous determination of many elements (Shackley, 2011). This method, that has been widely used in the analysis of archaeological remains (Liritzis and Zacharias, 2011; Richards, 2019), especially obsidian tools (as excellently compiled by Speakman and Shackley, 2013), was also employed in this study. Logically –and following published suggestions (Liritzis and
Zacharias,2011), we did not include in this study elements with very low concentrations, around the limit of detection. So, we considered only about 20 elements that are present in reliable, amounts in the rocks analyzed, and we compared the concentrations of these elements among the two sites. In Table 2 we show that in the univariate analysis there are marked differences in the concentrations of some elements. 11
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Application of the function to these precisely located material fully assign its composition to each of the two manufacturing centers, confirming its validity. In order to test the practical value of the several indices and discriminant function obtained, we have analyzed 12 complete or fragmented rotary querns, some of them found during excavation of dwelling places, some others found during prospections in several parts of Tenerife, and also some querns housed at the Laboratory of Prehistory of our University with only a vague indication of the place they were found. Results are shown in Table 4. Interestingly, those found in the excavation of the dwelling place of Chasogo, another one with an imprecise label “Pico Viejo” and a last one found at a site named “Los Frontones” located in the southwestern slopes of Tenerife, at about 1100 m over sea level (see map, Fig. 10) seem to have been manufactured in Cruz de Tea, as was also the case for two other samples dug out during the excavation of a dwelling place near Cruz de Tea, and also the case of a quern housed at the Laboratory of Prehistory, labelled “Teide Viejo west”. The theoretical possibility exists that these querns were produced using (not still analyzed) scoria of any other volcanic cone, but what we can assure is that they were not manufactured using material from Los Corrales. On the other hand, the vaguely labeled quern “near Los Tomillos”, with a positive value of the discriminant function (but slightly below the 95% confidence interval for Los Corrales) was possibly manufactured in Los Corrales, but surely not in Cruz de Tea. Some other querns, as shown in Table 4, from “Las Cañadas” or from the southern coast (Las Galletas) showed elemental compositions and a value of the discriminant function that are outside the confidence intervals of both the material from Cruz de Tea and Los Corrales, suggesting that other sources of raw material must have been employed for the production of some querns. Therefore, in this study we have added another example about the usefulness of XRF methodology in analyzing archaeological material. We have fully characterized chemical composition of the raw material of two major workspaces in which grinding stones were manufactured and used the data to perform a discriminant function that allows a clear-cut identification of each of the two sites. Application of this function served to assess provenance of rotary querns found in the excavation of precisely located dwelling places, and also of some querns found at more or less vaguely labeled distant sites, although elemental composition of some other querns suggest that other sources of raw material were also utilized. Another important conclusion of this study is just the finding of only two major workspaces in the highlands of Tenerife in which grinding stones were produced, strongly suggesting that manufacturing of these artifacts was a specialized procedure. This is an archaeological finding relevant for the interpretation of the style of life and socio-economical conditions of the ancient Guanches.
Table 3 Values of the discriminant function when it was applied to new samples (portable querns or fragments found near the wokspaces, not included in the discriminant function. Cruz de Tea Cruz de Tea Los Corrales Los Corrales Los Corrales Los Corrales Los Corrales Los Corrales Los Corrales Los Corrales Los Corrales
−4.96472 −5.12885 5.05556 5.21092 4.74531 7.60082 6.57642 4.02482 2.64609 3.79048 2.60295
This is the case of rubidium, titanium, calcium or iron, with t-values around 20. The raw material from Cruz de Tea shows by far higher contents of titanium, iron and calcium than that of Los Corrales, which, on the other hand, contains much more rubidium. Silicon and aluminium contents are similar in the rocks of both places, and magnesium is slightly higher among the raw material from Cruz de Tea. The proportion of mafic minerals is more abundant in the basanite scoria from Cruz de Tea than in the phonotephrite/benmoreite rocks of Los Corrales, thus explaining the significantly higher content of magnesium, and, especially, iron observed in the rocks from Cruz de Tea. The differences in calcium can be explained on the possible existence of more intermediate plagioclases among the rocks of Cruz de Tea. The relatively recent volcanoes of the western slope of Pico Viejo show indeed a relative abundance in calcium plagioclases and iron and titaniumcontaining clinopyroxenes (Ablay et al,1998; Bravo, 1962). Showing lower rubidium, but higher titanium, iron and calcium, the differences of the ratios Rb/Fe, Rb/Ti, or Rb/Ca are even more marked among the two archaeological sites, something that becomes clearly illustrated in Fig. 7a–c. Next, we performed a stepwise discriminant function analysis introducing the three mentioned indices as independent variables. Only the Rb/Fe and Rb/Ca ratios were selected (by the SPSS program), yielding a discriminant function that clearly separates both sites (Fig. 9). Moreover, mean and 95% confidence intervals of the punctuations obtained when the discriminant function was applied to each of the samples show very different, not overlapping values, that allow a clear-cut distinction between the materials of the two sites, as is also clearly shown in Fig. 9. Lastly, we applied this function to the composition of several pieces that constitute the test group, destined to confirm the reproducibility of the discriminant function using samples not included in its calculation.
Table 4 Values of the Rb/Ca, Rb/Fe, Rb/Ti indices and of the punctuation obtained when the discriminant function was applied to querns found at diverse locations. For comparative purposes we also provide the confidence intervals of the mentioned indices and discriminant function punctuations derived from the analysis of the raw material from Cruz de Tea and Los Corrales.
Chasogo-1 Chasogo-2 Chasogo-3 Pico Viejo Piece number 32 Cruz de Tea-1 Cruz de Tea-2 Piece number 18 (Las Cañadas) Las Galletas Los Frontones “Near Los Tomillos” Pico Viejo West Raw material Cruz de Tea Raw material Los Corrales
Excavation Excavation Excavation Lab Prehistory Lab Prehistory Excavation Excavation Lab Prehistory Prospection Prospection Lab Prehistory Lab Prehistory
Rb/Ca
Rb/Fe
Rb/Ti
Discriminant function
Provenance
0.97 1.16 1.07 0.94 2.72 0.68 0.77 2.12 0.19 0.94 3.24 0.62 0.65–1.67 2.73–5.55
0.51 0.68 0.71 0.52 1.12 0.44 0.43 0.94 0.16 0.66 1.32 0.38 0.49–0.83 1.38–2.12
2.78 3.75 3.65 2.85 7.19 2.41 2.23 6.67 0.83 3.49 9.36 1.84 2.62–5.12 8.31–14.19
−5.04 −4.03 −3.97 −5.15 −0.41 −5.69 −5.65 −1.87 −7.49 −4.35 +1.02 −6.02 −2.39 to −5.93 1.69–6.64
Cruz de Tea Cruz de Tea Cruz de Tea Cruz de Tea Unknown Cruz de Tea Cruz de Tea Unknown Unknown Cruz de Tea Corrales? Cruz de Tea?
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Fig. 10. Map showing the central and southern part of Tenerife. In this map one can see the sites in which the querns were found (circles), and also the two workspaces (Cruz de Tea and Los Corrales).
Declaration of Competing Interest
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