RESEARCH POSTER PRESENTATION DESIGN © 2015 www.PosterPresentations.com Archeomagnetism is the study of archeological materials that contain magnetic minerals, principally iron oxides, which have the ability to register temporal- space variations of the Earth’s magnetic field (EMF). These variations allow us to date these materials (Soler Arechalde, 2014: 2). Minerals acquired an arrangement when they are exposed to fire and heated up above their Curie temperature ( 580 ° C) and cools below this point, recording the direction and strength of the local magnetic field present in that time (Soler Arechalde, 2006: 29). The materials of study of the archeomagnetism are divided into two essential types: the ones found in-situ and those displaced. In the first group are the stoves, furnaces, temazcal, floors, burned walls and floors. From this kind of contexts it is possible to obtain a full description of the EMF, including direction and intensity. The second group includes fired clays like pottery, bricks and shingles. Given that it is not known the position in which the cooling occurred, it is not possible to determine the direction of the EMF at the time, but only its strength (Rodriguez Ceja, 2003: 22). Introduction Materials and Sampling The archaeological site of Tingambato is located in the municipality of the same name, between the cities of Pátcuaro and Uruapan, Michoacán, in Western Mexico. Nestled in a Valley at about 2000 meters above sea level, which is a natural step that connects two very important regions: the Tierra Caliente and the Lacustrine area, and that in its time of splendor could have functioned as a kind of customs, controlling the passage of goods from one region to another. Besides there is no regionally a contemporary site similar to Tingambato, with complex constructions as platforms in which pyramidal bases of large dimensions and tombs were built to entomb the elite, it makes us think that it was the most important site in the region (Punzo Diaz et al., 2015,2016). The occupational temporality of the site is still in doubt. It has had two important interventions: the first one in 1978, by means of the “Proyecto Tinganio” (Piña Chan et al., 1982), and the second one by means of the “Proyecto Especial Michoacán (PEM)” in 2012 (Cruz Hernández et al., 2013). Both proyects generated two different occupational proposals based on ceramic, stratigraphic and architectural analysis, without supporting them with some sort of absolute dating. Archeomagnetism Conclusions As a result of the dating of the 9 ceramic samples, and the preliminary analysis of ceramic types, the stratigraphy of the site and 14 C datings, it was possible to propose the first chronological occupational of the site based on absolute datings, which is summarized in the following table. References Cruz Hernández, Laurie Melchor, Landa Alarcón, Olga Lidia. (2013). Tingambato. Un sitio del Occidente de México y una tumba real. En Arqueología mexicana, XXI (123) Septiembre-Octubre, 43-46. Morales Contreras, Juan Julio (2003). Determinación de la paleointensidad absoluta sobre las rocas mexicanas y sudamericanas: aspectos metodológicos e implicaciones geomagnéticas. Tesis doctoral en Ciencias. UNAM. México. Tauxe, Lisa (2008). Essentials of rock and palemagnetism. University of California Press. Rodríguez Ceja, María Guadalupe (2003). Análisis y fechamiento arqueomagnético de estucos de zonas habitacionales de Teotihuacán (Xala) y Templo Mayor. Tesis de Lic. en Física. UNAM. México Soler Arechalde, Ana María (2006). Investigaciones arqueomagnéticas en México. Fundamentos, historia y futuro. Monografías del Instituto de Geofísica. UNAM. Núm. 10. México. (2014). Arqueomagnetismo en México 1965-2013. En Latinmag letters. Vol. 4 Núm. 4. Piña Chan, Román y Ohi Kuniaki. (1982). Exploraciones arqueológicas en Tingambato, Michoacán. INAH. México D.F. Punzo Díaz, José Luis. Castañón Suarez, Mijaely, González González, Lissandra y Hernández, Cesar Valentín. (2015). Informe técnico. Proyecto Arqueología y Paisaje del Área Centro-Sur Michoacán. Temporada 2015. Archivo Técnico. INAH. Castañón Suarez, Mijaely, González González, Lissandra. (2016). Proyecto Arqueología y Paisaje del Área Centro Sur de Michoacán. Informe técnico 2016. Archivo Técnico. INAH. Contac information David Rangel Campos: david.rangelazul@hotmail.com Dr. Juan Julio Morales Contreras: jmorales@ geofisica.unam.mx Dr. José Luis Punzo Díaz: jlpunzod@mail.com The ceramic type and their stratigraphic location were the selection criteria used in this study. The ceramic type identification is very important since it allows to have a relative dating and make a comparison with other sites where the same ceramic type is found and make inferences about its relationship with these. In Tingambato it was possible the identification of ceramic types which are also present in the basins of Zacapu, Pátzcuaro, Lake Cuitzeo, and Apatzingan, while its stratigraphic location will allow to identify an occupational sequence and a possible evolution of the ceramic. Two lots were formed from the 14 selected samples. The first lot consisted of nine samples whiled the second of five. The objective of the first batch was to date ceramic types of regional importance such as the Cheran in Cuitzeo, and the Agropecuaria, Tres Palos and Loma Alta Pulido in Zacapu and Pátzcuaro, while the objective of the second was to date the beginning of the occupation of the site. Only 9 out of the 14 samples selected yielded successful results, which are shown in the following table. Results David Rangel Campos, Juan Julio Morales Contreras and José Luis Punzo Díaz Proyect: Arqueología y Paisaje del Área Centro Sur de Michoacán Archeomagnetic dating of ceramic potsherds of the Tingambato archeological site ID Ceramic type Excavation unit Cap M01 Agropecuaria 11 V M02 Café esgrafiado 19 III M03 Café pulido 3 F M04 Zacapu Café 4 D M05 Cherán 3 F M06 Loma Alta Pulido 3 F M07 Tres palos 4 E M08 Rojo Pulido (Fogón) 2 Fogón M09 Rojo Escobillado (Fogón) 2 Fogón M10 Olla (Borde) 4 E M11 Lupe Punzonado 4 D M12 No identificado 4 H-I M13 Blanco sobre Rojo Superficie M14 Rojo Pulido (Olla) 4 H Experimental procedure Since the determination of archeointensities is a long process, and that the intensity of the ancient field logged in the sample is easier to alter than its direction, methods to increase the success of the determinations have been implemented through time. In this sense, it was decided to carried out pilot tests on one specimen per sample using alternating field (AF) demagnetization. This technique helped us to identify samples in which its original magnetization has been significantly altered by secondary components and, therefore, are not suitable samples for archeointensity determination experiments. As a result of these pilot tests, two out of the initially selected 14 samples were discarded since they showed an important alteration in its NRM and were not suitable candidates for the archeointensity determination experiments, leaving only 12. Thellier-Coe method In order to determine the archeointensity of the samples several methods have been developed, being the one proposed by Thellier-Coe, which has had more success. This method consists in a gradual thermal demagnetization of the sample’s NRM in a laboratory oven, and an also gradual remagnetization of the sample under a control laboratory field. These double-heating steps represent a single point on the Arai plot, which are repeated at gradually higher temperatures up to 580 °C, the Curie temperature of magnetite at which the sample loses its NRM. The laboratory magnetic field (H lab ) should be as close as to the expected ancient magnetic field (Morales, 2003). In this work the H lab was set to 45 μT since it was the intensity of the Earth's magnetic field present in the region for that temporality. Example of one of the two rejected samples for archeointensity determination. Upper panels: Stereo plot and corresponding Zijderveld diagram, left and right panels respectively. Lower panels: NRM demagnetization and ceramic fragment analyzed, left and right panels respectively. Representative example of a suitable sample for archeointensity determination. Upper and lower panels description as in the left figure. Left. Representative Arai plot obtained during the Thellier-Coe experiment. Each point on the graph represents a double-heating step. The bottom-right panel shows the different temperatures of each heating step. Global geomagnetic field model SHA.DIF.14k Archeointensity data obtained are compared against the predicted geomagnetic field model SHA.DIF.14k. Intensity reference curve (thick solid red curve) with the 95% error envelope (thin red curves) calculated from the SHA.DIF.14k global geomagnetic field model (Pavón- Carrasco et al., 2014) and the undated archeointensity data (thick straight blue line) with the 95% error envelope (green straight lines). ID Ceramic type Stratigraphic cap Most probable age interval M01 Agropecuaria V S/R M02 Café esgrafiado III S/R M03 Café pulido F 601-624 d.C. 639-825 d.C. M04 Café Zacapu D 677-808 d.C. M05 Cherán F 670-815 d.C. M06 Loma Alta Pulido F 0-66 d.C. 140-507 d.C. 969-1226 d.C. 1256-1551 d.C. M07 Tres palos E 99-102 d.C. 536-948 d.C. 1586-1600 d.C. M08 Rojo Pulido Fogón 546-940 d.C. 1596-1600 d.C. M09 Rojo Escobillado Fogón 88-113d.C. 532-734 d.C. 758-950 d.C. 1583-1600 d.C. M10 Olla (Borde) E S/R M11 Lupe Punzonado D S/R M12 No identificado H-I S/R M13 Blanco sobre Rojo 574-841 d.C. 879-915 d.C. M14 Rojo Pulido (Olla) H 554-934 d.C. Archeointensity determination Archeointensities are determined by comparing the demagnetized NRM induced by the ancient field (H ant ) against the acquired pTRM artificially induced by the laboratory field (H lab ) using the following expression:  ௔ =  ܯ  ܯ  ௔௕ As shown in the graph for sample LAF3, the model provides several age intervals. This is because the retrieved data intersect the global geomagnetic field model curve at various points, and cause for displaced objects (like ceramics potsherds) it is only possible the determination of one parameter, intensity. In order to select the most probable age interval it is needed having previously a relative chronology, based on ceramic and stratigraphic analysis, and in the best of cases, relate it to other types of absolute datings, as 14 C. Age Regional cronology (Centro-Norte de Michoacán) Local stage Description 0-300 d.C. Fase Loma Alta Tingambato I La primera nivelación del terreno, en donde se construyeron las primeras casas, correspondiente al nivel de la plaza 1. 300-550 d.C. Tingambato II Se destruyeron los muros de la casas para servir como relleno y subir el nivel del apisonado siguiente. Se construyeron canales de agua hechos de lajas. 550-900 d.C. Fase Lupe Tingambato III Igual que en la etapa anterior, los muros de la casas fueron desmontados para subir el nivel. Este nivel pare ser el nivel actual del área habitacional y la construcción de las tumbas I y II. Accordingly, the objective of this work was to perform absolute datings to generate, together with the stratigraphic analysis of ceramic and 14 C dating, an occupational chronology of the site using the archeomagnetic dating of ceramic.