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An integrated magnetic survey was carried out on key places within the La Quemada archaeological complex, built over a hill on the northern frontier of Classic period Mesoamerica. Samples were collected from the Plaza of Sacrifices and Hall of Columns in an attempt to precisely determine the age intervals corresponding to the decline and abandonment of the site, apparently due to the intentional firing as a closure ritual. Well-defined characteristic remanent magnetizations were retrieved from 23 of 32 samples. Moreover, twelve samples belonging to two areas yielded reliable determinations under criteria curtailed in this study. In any case, a primary remanent magnetization is carried by pseudo-single-domain Ti-poor titanomagnetite, as evidenced by hysteresis and continuous thermomagnetic curves. The archaeomagnetic dating was performed using full geomagnetic vector (directions and absolute intensity) using the last SHADIF14k model. The Plaza of Sacrifices seems to been burned between a time interval from 854 to 968 CE, while a late interval from 1018 to 1163 CE is assigned to the samples collected in the Hall of Columns, which suggest the gradual abandonment of the site. The first abandonment stage is almost synchronous to the same phenomena observed for other sites at the Bajio area (central and western Mesoamerica) region. Under these circumstances, it cannot be discarded that La Quemada was burned in its entirety during the first stage of abandonment, but the Hall of Columns was again burned later.

In absence of organic remains suitable for radiocarbon dating, archaeomagnetic dating can contribute significantly to the better understanding and rescue of our past and cultural heritage. Nowadays, in the archaeological research is fundamental to obtain as much information as possible, including precise dates of the archaeological sites; indeed, the rapid expansion of urban areas implies the destruction of archaeological structures, causing the loss of knowledge about our past. In this effort, we report an archaeomagnetic and rock-magnetic study on burnt archaeological samples from two kilns discovered at the monastery of San Pelayo del Cerrato (Cevico Navero, Palencia, Spain). This was a rescue excavation where arose the possibility of studying archaeomagnetically two ovens for the manufacture of tiles and bells before their destruction due to the restoration works of the monastery. Given their suitable conditions and the lack of independent absolute dating, the aim of the study is to archaeomagnetically date their last use. The main magnetic carrier is pseudo-single domain (PSD) Ti-poor titanomagnetite, indicating that the magnetic signal is stable. The comparison of mean full-vector values (mean direction and absolute archaeointensity determinations) with the SCHA.DIF.14k model determined their last use between 1301–1391 CE (bells´ kiln) and 1295–1404 CE (tiles´ kiln) at 95% confidence level, respectively. These dates agree well with the archaeological evidence indicating that the last use of both kilns occurred almost simultaneously or closely confined in time (14th century AD). The dating resolution obtained is comparable to the radiocarbon with the benefit that archaeomagnetism dates the last use (abandonment) of the structures and no material associated to it which might be slightly younger.

For centuries, and until a few years ago, it was considered that the distillation process had been brought to the new world by the Spaniards, who in turn learned it from the Arabs. For this reason, it was believed that the only alcoholic beverage of the Mesoamerican societies was pulque - a ferment of maguey. However, recent archaeological investigations revealed that the alcohol distillation was known in Mesoamerica long before the arrival of Europeans, for at least 25 centuries. The direct evidence comes from the ceremonial and administrative center of Xochitecatl-Cacaxtla (state of Tlaxcala) with several ovens where cooked maguey remains were discowered. The corresponding archaeological context was radiometrically dated from 600 to 400 BCE. Here, we report a detailed archaeomagnetic study on burned archaeological artifacts found in these cooking ovens. 35 specimens belonging to two pottery fragments, one burned rock and two burned soil samples were pre-selected for archaeointensity experiments. Pottery samples exhibited essentially reversible behavior during thermomagnetic experiments pointing to Ti-poor titanomagnetite (almost magnetite phase) as main magnetic carrier while two ferromagnetic phase seems to co-exist in burned soils. In contrast, burned rock samples exhibited some instabilities during the heating at high temperatures and indirect evidence of the presence of antiferromagnetic hematite grains. In total, 29 specimens allowed the estimation of absolute geomagnetic intensity recorded during the last use of the furnace. Archaeomagnetic dating yielded two possible time intervals between 878 to 693 BCE and 557 to 487 BCE. These new data reinforce the initial hypothesis and corroborate the temporality of these pre-Hispanic kilns.

A detailed rock-magnetic and archaeomagnetic investigation were carried out on seven pottery fragments (49 specimens) found within the burial of an individual with the most body/dental modifications and prestige elements found so far in the ancient Teotihuacan city. The skull of this 35 to 40 years old woman (at the time of death) shows an intentional cephalic modification with frontal-occipital compression. This is very uncommon within the Teotihuacan population and indicating the southern provenance (Oaxaca or Maya area). The age estimations, based on relative datings, placed the archaeological context between 350 and 400 CE. The magnetic mineralogy experiments were characterized by a single remanence component, occasionally accompanied by a soft overprint, probably of viscous origin and Curie temperatures between 540 °C and 565 °C. Only twelve specimens, belonging to two distinct pottery fragments, yielded reliable determinations meeting very strict selection criteria. The values retrieved from both fragments are statistically undistinguishable. The absolute age estimation of the Tlailotlacan Woman archaeological context obtained in this study contradicts the early estimations and indicates a late time interval between 650 and 800 CE corresponding to the decline of Teotihuacan, where the social differences of their inhabitants became much more evident.

The paper presents an overview of the current state of investigation of heated and heat-treated artefacts from Pleistocene sites, the methods frequently used in such investigation, and the main goals of similar research. Heated artefacts should be targeted in pre-excavation (mostly by non-destructive surficial methods), excavation (e.g., primary visual estimation, archaeomagnetic measurements in situ), and the post-excavation phases (a range of analytical methods). Apart from distinguishing heated artefacts, we are frequently able to date them directly, distinguish deliberately heated artefacts, assess the role of heat treatment on different Pleistocene sites, and draw conclusions about the spatial organization of such sites based on the distribution of heated artefacts. Successful heat treatment made stone knapping easier, enabled pressure flaking and the formation of sharper edges. The main causes of such improvements are the closing of pores due to the formation of new bonds, the appearance of fluid inclusions with high-velocity crack propagation, and potentially neo-formed iron oxides or other fluxes in the siliceous matrix. In view of recent research, the recrystallization of silica matter or the positive role of microcracks within the siliceous matrix are less probable causes of improved flakeability. Heat treatment was a type of technological and symbolic adaptation of modern humans to the frequently hostile environments of the Pleistocene as the two spread together over the world before the onset of the Holocene. The oldest dates of the technique currently come from the Near East. Though it might have spread from there to some parts of Eurasia, polycentric invention of heat treatment in the Pleistocene must be assumed. Independent centres of development of the technique are probably southern Africa, South America or Australia – relatively isolated regions where technological influence from other areas is not evidenced.

There is a significant lack of geomagnetic field strength (archaeointensity) measurements for many archaeological time periods in the United Kingdom (UK). This not only makes past geomagnetic secular variation difficult to model but also limits the development of archaeointensity dating. This paper presents the first archaeointensity study on UK Neolithic material. In this study, twenty-five sherds of Neolithic Grooved Ware pottery from the Ness of Brodgar, Orkney, UK, some with direct radiocarbon dates, were subjected to a full archaeomagnetic investigation with the aim of increasing the amount of archaeointensity data for the UK. Both thermal Thellier and microwave palaeointensity experiments were used to determine which technique would be most suitable for British Neolithic pottery. Three successful archaeointensity results between 35 and 40μT were obtained using thermal Thellier method, which is consistent with the limited data available within a 15° radius and geomagnetic field model predictions from the same time. We separated the results into four different types with an intention of explaining the behaviours that determine the likelihood of achieving an acceptable archaeointensity estimate. The feasibility of obtaining geomagnetic field strength information during the UK Neolithic from ceramics has been demonstrated and the results provide a solid basis for improving our knowledge of geomagnetic secular variation during archaeological time in Britain.

Red colored paintings contain small amount of antiferromagnetic hematite grains. When the red pigment is applied to the wall, these grains are free to move and they align their magnetic moment with the Earth's magnetic field. The resulting magnetization is called pictorial remanence. Here, we evaluate the usefulness of natural remanent magnetization carried by mural paintings in archaeomagnetism in order to try to estimate whether it may be used as a reliable dating tool. Moreover, we report a first ever attempt to analyze samples of cave paintings.

Lime production structures and their combustion were investigated in the western Yucatan Peninsula (Mexico). Limekilns were excavated and the specific calcination temperature for each kiln was calculated using Fourier transform infrared spectroscopy (FTIR). A temperature range of 750–850 °C was estimated for the furnaces used for lime production. This unambiguously confirms the thermoremanent origin of magnetization carried by kiln samples and thus the validity of archaeomagnetic dating. Rock-magnetic and magnetic studies were carried out on eight well-identified limekilns. Archaeomagnetic dating based on the full geomagnetic field vector indicated that five of the kilns were last used between 900 and 1050 CE and three of the kilns were used between 1460 and 1630 CE. The absolute chronology provided in the present study is linked to the constructive splendor in the northern plains of the Maya area.

Since the Late Preclassic, the ball court has been one of the most widely distributed features throughout Mesoamerican territory. Despite its maximum splendor in sites in the Mayan and Olmec area, this ritual and political phenomenon has important architectural expression within the archaeological complex of La Quemada in Zacatecas. To place this enclosure in an absolute chronological framework, an archaeomagnetic study was carried out on two fire pits within rooms associated with the court and a burnt cavity on one of its walls. The dating exercise for the first fire pit yielded an interval between 931 and 1006 CE as the best estimate of temporality for its last use. Two equally likely intervals were obtained from the second one (693–947 CE and 1463–1623 CE), so it is not possible to rule out any of them. The burnt cavity revealed a single interval between 757 and 980 CE These periods would correspond to the La Quemada Phase and its transition to the Citadel Phase, which was the last period of activity in the area before the ball court was abandoned. However, the dating of fire pit 2, which shows a possible late occupation (1463–1623 CE), could be interpreted as a reoccupation during the Postclassic by Zacatecos groups.

Most detailed archaeometric studies come from central and southern Mesoamerica while many important sites belonging to the western regions are not yet rigorously studied. Here we report a detailed rock-magnetic and archaeomagnetic study from the El Coporo archaeological site at the northern border of Mesoamerica. Our study of more than 100 oriented samples was performed on the six most important sites distributed along the archaeological zone. Continuous thermomagnetic curves revealed magnetite as responsible for magnetization accompanied by unstable (titano)maghemite. Most of the samples are characterized by a single component magnetization, which is almost completely removed applying 50 mT, suggesting the presence of relatively low coercivity magnetic minerals. Characteristic directions were precisely determined for four out of six studied sites, yielding statistically undistinguishable directions. Corresponding archaeomagnetic age intervals range from 820 to 950 A.D. in good agreement with previous archaeological studies that suggested a period of abandonment at about 900 A.D. as an attempt to reoccupy the place by the Toltecs. Numerous archaeological evidences argue in favor of an intentional fire. However, the possibility of ritual closure should be also considered since there is no evidence of violent or warlike actions.

A re-analysis of archaeomagnetic data from seven vitrified hillforts in Scotland, sampled in the 1980s, shows excellent agreement with recent radiocarbon dates. In the past thirty years our knowledge of the secular variation of the geomagnetic field has greatly improved, especially in the 1st millennium BC, allowing earlier archaeomagnetic data to be reconsidered. We evaluate the likelihood of the data with respect to a state-of-the-art field geomagnetic model and find close coherence between the observed directions and the model for the closing centuries of the first millennium BC. A new Bayesian method of calibration gives the most likely number of separate events required to produce a series of magnetic directions. We then show that the burning of three of the four oblong forts most likely took place around the same time, and our estimate for the date of this is indistinguishable from recent radiocarbon dates from another fort of similar type.

We carried out a detailed mineral magnetic and archaeomagnetic investigation on wattle and daub (locally known as Bajareque) building remains recovered at Teuchitlan archeological site (Jalisco, Mexico) in order to estimate the suitability of such material for Thellier double heating absolute geomagnetic intensity determinations and to contribute to the still incipient archaeomagnetic database for Mesoamerica. The single-domain Ti-poor titanomagnetite and hematite seem to be main magnetic carriers in most of samples. Although the presence of hematite is confirmed for all samples, its contribution to the remanent magnetization seems negligible and the most part of remanent magnetization is carried by almost magnetite phase. All 42 analyzed Bajareque samples yielded technically acceptable archaeointensity determination, which is probably a unique case since a 100% of success rate is reached. Present study underlines the exceptional magnetic properties of Bajareque samples and their high suitability for absolute geomagnetic intensity determinations. Selected mean archeointensity data currently available for Mesoamerica show unusually high dispersion, which makes it difficult to make any firm conclusion about the evolution of Earth's magnetic field through archeological time.

The large Protobyzantine settlement of Megali Kypsa was excavated at the NW part of Chalkidiki peninsula (North Greece). Among the numerous residential buildings a big ceramic complex with twelve kilns was unearthed. Nine of the kilns were preserved fairly well and the archaeological investigation suggested a large ceramic production for local use and exportation. The three best preserved kilns were sampled for an archaeomagnetic study, while numerous TL dating results in combination with archaeological information constrained the last use of the kilns from the end of the 4th to the middle of the 5th century AD. Rock magnetic analyses have been performed on pilot samples and identified magnetite as the main carrier of the natural remanent magnetisation. The samples were subjected to both alternating field and thermal demagnetisation providing reliable directions. Intensities were calculated with the Triaxe protocol and yielded a mean value of 61.2 ± 1.8 μΤ. The obtained results are compared with regional and global geomagnetic field models (SCHA.DIF.3K and ARCH.3K). Our study provides 3 new full-vector data, improving the resolution of the Greek secular variation curve for this poorly documented period.

The present study is a multi-analytical approach for the characterization of several potsherd samples, dated from Late Classical to the Hellenistic period at three different archaeological sites of Northern Greece: Pella, Thasos and Samothrace. Ceramic petrography, Scanning Electron Microscopy coupled with Energy Dispersive Spectrometry (SEM-EDS) and X-Ray Powder Diffraction Analysis (XRPD) were applied for the determination of the chemical and mineralogical characteristics of the studied ceramics as well as the morphology of the clay with high resolution SEM images. Magnetic measurements on the sherds enriched the present study and when combined with the archaeometrical approach described above, contribute to the characterization of the material on its suitability for archaeomagnetic experiments. The overall obtained results confirm a local provenance and techniques used for the pottery production.

A comprehensive rock magnetic and absolute archaeointensity (AI) investigation was carried out on baked bricks from the east coast of India with an aim to obtain a set of well-defined palaeointensity (PI) data. The new PI data from India comprise a significant first step to improve the regional intensity reference curve, which can be used as reliable dating tool mainly for archaeomagnetic material. Standard Thellier-Coe experiments were applied on 12 independent brick samples collected from a Buddhist monument at Adurru in the Godavari delta and a Medieval Fort at Kolleti Kota site situated on an island in the Kolleru Lake. The samples thus collected represent two different archaeological periods, one around the 3rd century BCE and the other between the 4th and 7th centuries CE respectively. The data obtained from thermal demagnetization of Saturation Isothermal Remanent Magnetization (SIRM), temperature dependent magnetic susceptibility (χ–T), Isothermal Remanent Magnetization (IRM) acquisition curves, and hysteresis measurements showed that the primary carriers of Natural Remanent Magnetization (NRM) are fine-grained Pseudo-Single Domain (PSD) (Stable Single Domain (SSD) + Superparamagnetic (SP)) titanomagnetite with various titanium contents. This implies that the samples had significant stable Thermoremanent Magnetization (TRM), and, therefore, good candidates for PI analysis. Strict selection and quality-control criteria for detecting magnetomineralogical alteration and intensity data corrected for anisotropy and the cooling rate effects on TRM acquisition, offer high quality PI determinations with respect to the previous available data that missed such corrections. A total 33 specimen level PI determinations that correspond to linear NRM–TRM plots, were made using the Thellier GUI software. The corrected data yielded mean PI values of 44.6 ± 1.4 μT for the Buddhist Monument, and 36.6 ± 2.9 μT for the Fort site. By comparison and evaluation of new PI data with Global Geomagnetic Field Model predictions, the sampled bricks were archaeomagnetically dated using the Matlab tool developed by Pavon-Carrasco et al. (2011) . Both ARCH3K.1 and SHA.DIF.14 K global models were used to evaluate the age estimates. The SHA.DIF.14 K model provided the most accepted age estimates that varied between 305 and 182 BCE for the early historic Buddhist Structure at Adurru, and 516–889 CE for the Medieval Fort at Kolleti Kota. These new reference archaeointensity data highlight the potential of archaeomagnetic dating to improve the archaeologically determined time periods of bricks, and also show the need for new high quality reference data to improve the geomagnetic field models from India.

Colombia is located along so-called intermediate area between two major American civilizations: Mesoamerica and Central Andes. Despite impressive archaeological sites throughout whole Colombian territory and great cultural heritage, still no regional geomagnetic secular variation curve is available. Here, we report first, systematic archaeointensity measurements on the Bogota Savanna Pre-Hispanic pottery samples corresponding to a radiometrically well dated archaeological context. Seventy-two samples belonging to six potsherds were subjected to the full battery of rock-magnetic experiments in order to select the most suitable samples for double heating palaeointensity experiments. The selected samples exhibited magnetically and thermally stable behavior pointing to titanium-poor titanomagnetite as responsible for magnetization. Under our imposed selection and acceptance criteria, only 37 specimens coming from two pottery fragments provided high-quality technical determinations. These new data together with all up to now available similar-quality determinations from the Caribbean region were used to build a first regional reference curve using a bootstrap method. The main variation tendency observed in the Caribbean curve is rather similar to the North American (central Mexico and southern United States) patterns but show substantial difference with the South American regional variation curve, most probably influenced by non-dipole contribution due to the South Atlantic Magnetic Anomaly. This first Caribbean curve extends the knowledge of the absolute intensity variation over the three millennia and should be considered as most reliable dating tool in Colombia and surrounding regions.

A Roman glass workshop situated near the German-Dutch border in the vicinity of the modern village of Goch-Asperden has been investigated archaeomagnetically. Archaeological evidence including potsherds, coins and fragments of glass vessels suggests that the workshop was in use from shortly before 400 CE to the first third of the 5th century CE, though from archaeological point of view the period of operation cannot have covered more than a few years. The archaeomagnetic directions of the two superimposed glass furnaces are well defined while a feature of burnt sand gave relatively scattered directions. The mean direction of the upper furnace agrees well with that of the burnt sand but the results from the lower furnace are significantly different. This difference is likely to be due to a tilting of the lower furnace because of the sandy foundation. Archaeointensities obtained from classical Thellier and multiple-specimen paleointensity domain-state corrected experiments are in good agreement between methods as well as between the furnaces. This supports the hypothesis for contemporaneity of the furnaces. Archaeomagnetic dating evidence is in good agreement with the archaeological age indicators but is not able to refine it further. The well dated and reliable archaeomagnetic full vector contributes to the archaeomagnetic database of Europe.