Papers by Alicia Palencia Ortas
Complutum, Mar 10, 2022
Resumen. Los trabajos de excavación que se han llevado a cabo en el yacimiento de Quinta de Crest... more Resumen. Los trabajos de excavación que se han llevado a cabo en el yacimiento de Quinta de Crestelos (Merinhos, Mogadouro, Portugal), han puesto de manifiesto la presencia de una importante ocupación durante la II Edad del Hierro y la romanización de esta zona. En la zona alta de este enclave se ha registrado un poblado fortificado, con complejos sistemas defensivos, entre los que se encuentran unas potentes murallas y fosos, que van a sufrir diferentes reestructuraciones a lo largo del tiempo. La evolución que se ha podido identificar en esta zona muestra el proceso de romanización de esta región, y la adaptación que se produce en los poblados de la Edad del Hierro, a través de la reformulación de espacios defensivos, como los fosos, en áreas funcionales y productivas. Se ha llevado a cabo un estudio de paleomagnetismo, y análisis de todas estas estructuras de combustión, con la finalidad de poder determinar la función de las mismas, sus principales características, y su uso a lo largo del tiempo. Palabras clave: II Edad del Hierro; romanización; estructuras de combustión; foso; poblado fortificado.
Geotemas ( Madrid ), 2016
por haberme permitido desarrollar mi trabajo tanto aquí como allí. Gracias Marisa, por transmitir... more por haberme permitido desarrollar mi trabajo tanto aquí como allí. Gracias Marisa, por transmitirme tu entusiasmo por la ciencia, por haberme enseñado tanto, eres muy buena directora y sin tu apoyo no estaría aquí este trabajo. La verdad es que me siento muy afortunada porque se cruzaran nuestros caminos. Gracias por tu amistad. Casi no me lo creo, pero estoy escribiendo los últimos párrafos para la tesis. Y me lleno de alegría y emoción al recordar a todas las personas que me han acompañado en este camino, para hacerlo más fácil. Tengo que reconocer que he tenido mucha suerte por haberme encontrado con tan buena gente: que me ha enseñado tanto, que me ha apoyado en todo momento, y que me ha hecho sentir bien durante estos años. Sin ellas no habría sido posible escuchar y entender las historias que cuentan las piedras. Gracias a todos. A los geólogos con que he trabajado, que me han enseñado a ver el campo con otros
Geophysical Journal International, 2011
Available apparent polar wander (APW) paths for the 200 Ma configuration of Pangea, just prior to... more Available apparent polar wander (APW) paths for the 200 Ma configuration of Pangea, just prior to the opening of the Central Atlantic Ocean, differ as much as 10 o in arc length. Here, we add new data from northwest Africa for this time, obtained from the northeasttrending Foum-Zguid and Ighrem dykes (ca. 200 Ma). These dykes form part of the northern domain of the Central Atlantic Magmatic Province (CAMP), and crosscut the Anti-Atlas Ranges in Morocco, and compositionally correspond to quartz-normative tholeiites intruded in continental lithosphere shortly before the opening of the Central Atlantic Ocean. The Foum-Zguid dyke has been intensively studied, whereas the Ighrem dyke has received less scientific focus. We sampled both dykes for paleomagnetic investigation along 100 km of each dyke (12 sites for Foum-Zguid and 11 for Ighrem, 188 samples included in the final analyses). Rock magnetic experiments indicate a mixture of multidomain and single-domain magnetite and/or low-Ti titanomagnetite particles as the principal remanence carriers. In both dykes, the primary nature of the characteristic remanent magnetization is supported by positive contact tests, related to Fe-metasomatism or baked overprints of the corresponding sedimentary country rocks. The directions of the characteristic magnetization exhibit exclusively normal polarity. Site-mean virtual geomagnetic poles are differently grouped in each dyke, suggesting distinct geomagnetic secular variation records. The Foum-Zguid paleomagnetic pole (N = 12, PLat = 67.9 • N, PLon = 247.9 • E, κ = 125, A 95 = 3.9 •) plots close to that of Ighrem (N = 11, PLat = 78.4 • N, PLon = 238.2 • E, κ = 47, A 95 = 6.7 •), confirming those mineralogical and geochemical evidences supporting that they represent dissimilar magmatic stages. Virtual geomagnetic poles dispersion from both dykes (S = 10.5 •13.0 • 8.1 •) is in line with those obtained from recent studies of a CAMP-related dyke in Iberia and results from CAMP lavas in the Argana basin. These three new estimates of paleosecular variation at low latitudes around the Triassic-Jurassic boundary are concordant with a recently proposed dispersion curve for the Jurassic but suggest a slightly lower geomagnetic scatter than considered so far. After combining results from both dykes, the resulting paleomagnetic pole (PLat = 73.0 • N, PLon = 244.7 • E, N = 23, κ = 55, A 95 = 4.1 •) is statistically compared with existing and coeval African paleopoles, and with global synthetic 200 Ma running mean poles in northwest Africa coordinates.
Excavaciones arqueológicas en Asturias 2013-2016, 2018
Geotemas ( Madrid ), 2016
El conocimiento de las caracteristicas del campo geomagnetico disminuye retrocediendo en el tiemp... more El conocimiento de las caracteristicas del campo geomagnetico disminuye retrocediendo en el tiempo. Las magnetizaciones primarias registradas en rocas magmaticas son registros puntuales y fiables del paleocampo y constituyen la fuente de los estudios de Variacion Paleosecular del campo geomagnetico (PSV, en ingles), por lo que estos se concentran en los ultimos 5 Ma. Como una estimacion de la PSV, se analiza la dispersion angular geomagnetica en funcion de la paleolatitud. En este estudio, la PSV se evalua en el Jurasico analizando los datos paleomagneticos disponibles en Iberia para rocas magmaticas de esas edades, que se reducen a los realizados en el dique de Messejana-Plasencia, de edad Jurasico Inferior. Los resultados obtenidos en el dique concuerdan con los provenientes de una seleccion de datos paleomagneticos globalmente distribuidos para el periodo Jurasico. Ademas, se presentan los resultados paleomagneticos y de magnetismo de rocas preliminares obtenidos en rocas volcani...
El Cierro se localiza en Fresnu, en el concejo de Ribadesella (Asturias). Sus coordenadas geográf... more El Cierro se localiza en Fresnu, en el concejo de Ribadesella (Asturias). Sus coordenadas geográficas son 43º 27’ 26’’ de latitud N y 5º 06’ 20’’ de longitud O. Se sitúa a unos 83 m sobre el nivel del mar, del que dista en la actualidad 3,1 km en línea recta a la desembocadura del río Sella y 2,1 km a los acantilados de Tereñes. La cueva se encuentra en el extremo oriental del macizo asturiano de la Cordillera Cantábrica, en un sector formado por materiales paleozoicos de la Zona Cantábrica del Macizo Ibérico. Se trata de una cavidad kárstica situada en las calizas de La Escalada, del Carbonífero (Moscoviense), constituidas por calizas micríticas y bioclásticas de color gris y muy recristalizadas.info:eu-repo/semantics/publishedVersio
Trabajo presentado en la European Geosciences Union General Assembly, celebrada en Viena (Austria... more Trabajo presentado en la European Geosciences Union General Assembly, celebrada en Viena (Austria), del 23 al 28 de abril de 2017In this work we present the first archaeomagnetic intensity database for the Iberian Peninsula covering the last 3 millennia. In addition to previously published archaeointensities (about 100 data), we present twenty new highquality archaeointensities. The new data have been obtained following the Thellier and Thellier method including pTRM-checks and have been corrected for the effect of the anisotropy of thermoremanent magnetization upon archaeointensity estimates. Importantly, about 50% of the new data obtained correspond to the first millennium BC, a period for which there was not possible to develop an intensity palaeosecular variation curve before due to the lack of high-quality archaeointensity data. The different qualities of the data included in the Iberian dataset have been evaluated following different palaeomagnetic criteria, such as the number of specimens analysed, the laboratory protocol applied and the kind of material analysed. Finally, we present the first intensity palaeosecular variation curve for the Iberian Peninsula centred at Madrid for the last 3000 years. In order to obtain the most reliable secular variation curve, it has been generated using only selected high-quality data from the cataloguePeer reviewe
A Paleomagnetic investigation o f 11 sites across the southern part o f Messejana-Plasencia dike ... more A Paleomagnetic investigation o f 11 sites across the southern part o f Messejana-Plasencia dike has been carried out. The magnetic behaviour o f p ilot samples indicates that thermal demagnetisation is more effective than alternating field cleaning (AF) in isolating the Characteristic Remanent Magnetisation (ChRM). Therefore thermal demagnetisation was systematically used with the remaining samples. The ChRM is w ell grouped. M ost sites exhibit normal polarities with the exception o f two sites, where samples with reversed polarities have been observed. The paleomagnetic pole derived from the sites is w ell defined, with values o f Plat=72.5, Plong=243.7 and A l)€;=6.0. This coincides with the pole calculated in a previous investigation (Schott et at. 1981) o f the dike. It is also in agreement with Toarcian poles from the Iberian Range (Osete et al. 2000) and statistically different from the Oxfordian Pole obtained in the same region. Previous radiometric studies suggested that the age o f dike intrusion is 160-200Ma. Paleomagnetic data indicates that the age o f intrusion can be constrained between 180-200Ma.
Se presenta una revision de los polos paleomagneticos de Iberia de los ultimos 300 Ma. Con objeto... more Se presenta una revision de los polos paleomagneticos de Iberia de los ultimos 300 Ma. Con objeto de analizar la consistencia del registro paleomagnetico y el oceanico, e investigar el movimiento relativo de Iberia con respecto a las Placas Africana y Euroasiatica, se compara la curva de Iberia, con la Curva patron de Africa y Eurasia de los ultimos 200 Ma (Besse y Courtillot, 2002). Los resultados de Iberia discrepan de los africanos en el Periodo Aptiense-Albiense, debido probablemente a que los polos ibericos corresponden a polos obtenidos de materiales reimanados hace 95-100 Ma. Tambien se observa una contradiccion entre los polos ibericos de 70 Ma y la Curva Patron de Africa. Esta diferencia se explica por la asuncion erronea de que Iberia se movio solidaria con Africa entre las anomalias 33-21 (Srivastava et al., 1990) y, por tanto, por la inexactitud de los polos de rotacion de Euler obtenidos a partir del registro oceanico. Los datos paleomagneticos indican que Iberia tuvo u...
Physics of the Earth and Planetary Interiors, 2021
Abstract Absolute past geomagnetic intensity values can mainly be recovered by fired archaeologic... more Abstract Absolute past geomagnetic intensity values can mainly be recovered by fired archaeological materials and volcanic rocks. Here, we present 10 new archeointensities from the Mediterranean region that help to better constrain geomagnetic field intensity changes in Europe over the last two millennia. The new archeointensity results were obtained from the Thellier classical method including thermoremanent magnetization (pTRM) checks and both the TRM anisotropy and cooling rate corrections and were derived from at least three specimens. The new data presented, together with a selection of previous archeointensities satisfying a set of quality criteria, confirm the presence of several intensity maxima in Europe over the last 2000 years. In particular, the new archeointensities allow to better define the starting point of the double-oscillation feature that occurred in Europe during the second half of the first millennium CE, and reinforce the existence of a relative maximum at the end of the 14th century - beginning of the 15th century in Western Europe. From selected European archeointensities two new paleosecular variation curves are constructed for Western and Eastern Europe using temporal cubic b-splines in a bootstrap approach. The obtained curves suggest that the occurrence of the intensity maxima is characterized by a period of about 300 ± 50 years. In addition, our results suggest that the maxima do not occur simultaneously in Western and Eastern Europe, pointing out an intensity eastward drift with a mean lag-time of about 100 years.
Physics of the Earth and Planetary Interiors, 2021
International audienceIn directional archaeomagnetic studies, it is rarely analysed whether the c... more International audienceIn directional archaeomagnetic studies, it is rarely analysed whether the combustion structures display anisotropy of their thermoremanent magnetization (ATRM). It has been observed that, in specific cases like thin baked clays from the base of small hearths, archaeomagnetic directions can also be disturbed by the ATRM. We re-examine data from 56 combustion structures from Iberia and use them to analyse the ATRM effect on their archaeomagnetic directions. Flattening of inclinations up to 13 degrees has been found in highly anisotropic structures that can be adequately corrected by the ATRM tensors. We show how the lack of anisotropy corrections on directional values can dramatically deteriorate the ages obtained from archaeomagnetic dating, highlighting the importance of systematically analysing this property in future archaeomagnetic studies
Episodes, 2010
The Almonacid de la Cuba section, located in the Iberian Range, in central-eastern Spain, contain... more The Almonacid de la Cuba section, located in the Iberian Range, in central-eastern Spain, contains an outstanding record of the Pliensbachian-Toarcian boundary (Early Jurassic). Four ammonite assemblages, characterized respectively by the presence of Pleuroceras, Canavaria, Dactylioceras (Eodactylites) and Dactylioceras (Orthodactylites) have been distinguished. The base of the Toarcian is located at level CU35.2, based on the first occurrence of Dactylioceras. The presence of Boreal and Mediterranean taxa allows correlation between both bioprovinces. Magnetostratigraphy shows the most complete record of reversals of the Earth magnetic field for the base of Toarcian. The onset of the positive δ 13 C excursion which has been found in the Toarcian of several sections in Europe has been recorded. Average paleotemperatures for the latest Pliensbachian Spinatum Zone was about 12.5°. Seawater temperature rise during the lowermost Toarcian, reaching average temperatures of 16.7°C at the Tenuicostatum Zone. The 87 Sr/ 86 Sr curve fits with the LOWESS calibration curve.
Archaeological and Anthropological Sciences, 2019
The chronology of the Late Bronze Age and the earliest stages of the Iron Age in the Mediterranea... more The chronology of the Late Bronze Age and the earliest stages of the Iron Age in the Mediterranean is an important topic of debate since the study of both local social dynamics and trade and colonial activity around the Mediterranean requires obviously well-established chronological frameworks. However, the exact chronology of the Early Iron Age in the Mediterranean region is still a problematic issue today since different, and in some cases unbalanced, sources of information (historical texts, material culture sequences, and radiocarbon dating results) are used. The NE Iberian Peninsula is not an exception and different time periods are proposed in the literature for the Early Iron Age. Here, and in order to provide a new and an independent input to feed this debate, we apply the archeomagnetic dating method to four archeological hearths from the Sant Jaume Complex, a set of several Early Iron Age archeological sites located in the northeastern part of the Iberian Peninsula. The archeomagnetic dating results suggest that the abandonment of the studied structures (that can be linked to the abandonment of the archeological sites) most probably occurred before 650 BC, and therefore invalidate the age commonly ascribed to the Early Iron Age sites in this area. Our study provides, hence, new evidences that the traditional view of human settlement development in the NE Iberian Peninsula should be revisited.
A paleomagnetic investigation of 39 sites (591 samples) across the 530 km ot the Messejana-Pla se... more A paleomagnetic investigation of 39 sites (591 samples) across the 530 km ot the Messejana-Pla sencia dike has been carried out. Rock magnetic experiments indicate PSD low Ti titanomagnetite and magnetite as the minerals carrying the NRM. The samples where mostly demagnetised by thermal demagnetisation. Most sites exhibit a characteristic remanent component o f normal pola rity with the exception o f two sites, where samples with reversed polarities have been observed. The paleomagnetic pole derived from the sites is well defined, with values ot Plat=70.5, Plong=238.0, K= 47.8 and a gs=3.5. Paleomagnetic data indicates: (i) the dike had a brief empla cement time, (ii) the age o f intrusion can be constrained between 180-200 Ma, (Hi) the high grou ping of the VGPs directions suggest no important tectonic perturbations o f the whole structure of the dike since its intrusion to the present.
Tectonophysics, 2011
A revision of Jurassic palaeomagnetic data from Iberia has been carried out in order to investiga... more A revision of Jurassic palaeomagnetic data from Iberia has been carried out in order to investigate the consistency between the palaeomagnetic information and the tectonic models proposed for the western Mediterranean. Due to the presence of a widespread (but partial) remagnetization which affected most Jurassic sediments in Iberia, selection criteria have been designed to avoid completely remagnetized sites. A total of 72 sites have been considered for the palaeomagnetic discussion (35 sites from the Messejana-Plasencia dolerite dyke, 14 sedimentary sites from the Iberian Range and 23 sites from the Betic Cordillera). Three palaeopoles for Iberia have been selected (from the Iberian Massif and from the Iberian Range) for the period around 200 Ma, the Toarcian-Aalenian and the Oxfordian. Data from the Subbetic Zone (Betic Cordillera) are used to constrain the palaeolatitude of the Iberian microplate. Iberian data are in general agreement with the BC02 master curve and the reconstruction parameters used to transfer the Iberian data to Europe, but lower palaeolatitudes than predicted by BC02 master curve are observed in Iberia for the Late Jurassic. Iberia reached a maximum in palaeolatitude during the Toarcian-Aalenian (the reference point of Madrid was at about 37°), and since then, the palaeolatitude decreased (Madrid was at 22°by the Kimmeridgian). Tectonic reference models for the Western Mediterranean (Stampfli and Borel, 2002, 2004) do not fit the Iberian declinations and palaeolatitudes. New palaeogeographic reconstructions are proposed for the Hettangian-Sinemurian, the Toarcian-Aalenian and the Oxfordian.
Tectonophysics, 2006
The only Iberian lower Jurassic paleomagnetic pole come from the "Central Atlantic Magmatic Provi... more The only Iberian lower Jurassic paleomagnetic pole come from the "Central Atlantic Magmatic Province"-related Messejana Plasencia dyke, but the age and origin of its remanence have been a matter of discussion. With the aim of solving this uncertainty, and to go further into a better understanding of its emplacement and other possible tectonic features, a systematic paleomagnetic investigation of 40 sites (625 specimens) distributed all along the 530 km of the Messejana Plasencia dyke has been carried out. Rock magnetic experiments indicate PSD low Ti-titanomagnetite and magnetite as the minerals carrying the NRM. The samples were mostly thermally demagnetized. Most sites exhibit a characteristic remanent component of normal polarity with the exception of two sites, where samples with reversed polarities have been observed. The paleomagnetic pole derived from a total of 35 valid sites is representative of the whole structure of the dyke, and statistically well defined, with values of PLa = 70.4°N, PLo = 237.6°E, K = 47.9 and A 95 = 3.5°. Paleomagnetic data indicates that: (i) there is no evidence of a Cretaceous remagnetization in the dyke, as it was suggested; (ii) most of the dyke had a brief emplacement time; furthermore, two dyke intrusion events separated in time from it by at least 10,000 y have been detected; (iii) the high grouping of the VGPs directions suggests no important tectonic perturbations of the whole structure of the dyke since its intrusion time; (iv) the pole derived from this study is a good quality lower Jurassic paleopole for the Iberian plate; and (v) the Messejana Plasencia dyke paleopole for the Iberian plate is also in agreement with quality-selected European and North American lower Jurassic paleopoles and the magnetic anomalies data sets that are available for rotate them to Iberia.
Stratigraphy and Geological Correlation, 2010
We present the biostratigraphy (ammonites, brachiopods, fo raminifers, and ostracodes), lithos tr... more We present the biostratigraphy (ammonites, brachiopods, fo raminifers, and ostracodes), lithos tratigraphy, sedimentology, sequence stratigraphy, magnetostratigraphy, and isotope stratigraphy of the Almonacid de la Cuba section located in the Iberian Range, central-eastern Spain. This section, which con tains a continuous and expanded record of the Pliensbachian-To arcian boundary (Early Jurassic), has been proposed as a complementary section for the Toarcian GSSP. An excellent ammonite-based biozonation has been obtained. Four ammonite assemblages characterized by the presence of Pleuroceras, Canavaria, Dactylio ceras (Eodactylites), and Dactylioceras (Orthodactylites) have been distinguished. The base of the To arcian is located at level eU35.2, based on the fi rst occurrence of Dactylioceras. The occurrence of taxa fr om the NW European and the Mediterranean provinces is useful to improve the correlation between both provinces. Fo r aminiferal and ostracode assemblages are rich and diversified and no significant biostratigraphic events take place at the Pliensbachian-To arcian boundary. The magnetostratigraphic data presented here are the most complete record of reversals of the earth magnetic fi eld for the Pliensbachian-To arcian boundary. A good record of the onset of the positive o13e excursion reported in the Lower To arcian of many European sections has been obtained. Ave rage paleotemperatures measured at the latest Pliensbachian Spinatum Biochron of about 12.5°e, recorded a marked increase of the seawater temperature which started durin� the To arcian , reaching average temperatures of 16.rC at the Te nuicostatum Biochron. The obtained 87 Sri 6 Sr va lues fully agree with the LOWESS calibration curve .
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Papers by Alicia Palencia Ortas