Arqueomagnetisme, contribucions a l'estudi i valorització del patrimoni

La publicació de quatre articles al Journal of Archaeological Science sobre investigacions arqueomagnètiques a Catalunya i Tunísia consolida aquesta línia de recerca al departament de Geologia de la UAB. En aquest article s'explica què és l'arqueomagnetisme i es donen detalls sobre les investigacions dutes a terme en jaciments púnics i romans. Aquest tipus de recerca contribueix a millorar el coneixement històric i a datar jaciments arqueològics, una tasca important per a valoritzar el patrimoni arqueològic.La publicación de cuatro artículos en el Journal of Archaeological Science sobre investigaciones arqueomagnéticas en Cataluña y Túnez consolida esta línea de investigación en el Departamento de Geología de la UAB. En este artículo se explica qué es el arqueomagnetismo y se dan detalles sobre las investigaciones llevadas a cabo en yacimientos púnicos y romanos. Este tipo de investigación contribuye a mejorar el conocimiento histórico y a datar yacimientos arqueológicos, una tarea importante para valorizar el patrimonio arqueológico.The publication of four articles in the Journal of Archaeological Science dealing with archaeomagnetic studies in Catalonia and Tunisia consolidates this research line within the UAB Department of Geology. This popular science article describes what archaeomagnetism is and details are given on the research undertaken at Punic and Roman sites. These types of investigations contribute to improving historical knowledge and dating archaeological sites, an important task in the promotion of archaeological heritage

Penelitian Magnetostratigrafi Dan Penerapan Satuan Stratigrafi Polaritas Magnet Sebagai Satuan Kronostratigrafi: Studi Kasus Di Cekungan Bandung Serta Daerah Mojokerto Dan Sangiran, Jawa

DOI: 10.17014/ijog.v5i2.99Palaeomagnetism has a role to make a new stratigraphic nomenclature based on the earth magnetism of a nonperiodic reversal polarity phenomenon. Since this phenomenon has a global impact, it can be used as a potential correlation, known as the Magnetic Polarity Chronostratigraphy Unit. Remanent magnetism direction having reversal polarity against present earth magnetic field has long been known since early palaeomagnetic studies. Modern development of geomagnetic polarity time scale (GPTS), initiated in early 1960\u27s has followed the advancement of radiometric dating which is more accurate. A palaeomagnetic record obtained in the past of 3 Ma of rock in the Sangiran Area, East Java, has contributed in making a correction of previous magnetostratigraphy researches as well as a new level stratigraphy boundary and a new event of geomagnetic polarity. Based on the correlation record of secular variation in Mojokerto and Sangiran, the magnetostratigraphy of formations of Pleistocene age at Mojokerto has been arranged. The geomagnetic polarity stratigraphy of the past 4 Ma of the rocks in the Bandung Basin and its surrounding areas can be used as a guidance of isochronous position in the stratigraphy correlation

Deccan volcanism at the Cretaceous-Tertiary boundary

The accuracy with which one can claim that Deccan trap volcanism occurred at the Cretaceous-Tertiary boundary (KTB) over a very short time interval is of key importance in deciding whether a volcanic origin of the KTB events should be taken seriously. In the two years since paleomagnetic, paleontological and geodynamic evidence was published, further data have become available and the case now appears to be well constrained. The Ar-40/Ar-39 results from six labs have yielded some 24 reliable plateau ages that narrow the age range to 65 to 69 Ma. Moreover, it appears that a significant part of this range results from inter-lab spread and possible minor alteration. Paleontology demonstrates that volcanism started in the Maestrichtian, more precisely in the A. mayaroensis zone. Paleomagnetism shows that volcanism spanned only 3 chrons and only one correlation remains possible, that of the main central reversed chron with 29R. Therefore, whereas Ar-40/Ar-39 is able only to restrict the duration of volcanism to some 4 Ma, paleomagnetism restricts it to 0.5 Ma. Using some geochemical indicators such as C-13 as proxy, it is suggested that volcanism actually consists of a few shorter events of unequal magnitude. Extrusion rates may be as high as 100 cu km/yr and fissure lengths as long as several 100 km. Such a scenario appears to be at least as successful as others in accounting for most anomalies observed at the KTB. Particularly important are Iridium and other platinum group elements (PGE) profiles, Sr-87/Sr-86, C-13, 0-18, other exotic geochemical signatures, spherules, soot, shocked minerals, selective and stepwise extinctions. The environmental impact of CO2 possibly released during explosive phases of volcanism, and SO2 released during effusive phases, and the ability of volcanism to ensure worldwide distribution of KTB products are now all addressed. In conclusion, the case for a causal link between internal hotspot activity, birth of the Reunion hotspot itself as the Deccan and KTB events appears to rest on an increasingly stronger basis

Magnetostratigraphy of the Lower Triassic beds from Chaohu(China) and its implications for the Induan–Olenekian stage boundary.

A magnetostratigraphic study was performed on the lower 44 m of the West Pingdingshan section near Chaohu city, (Anhui province, China) in order to provide a magnetic polarity scale for the early Triassic. Data from 295 paleomagnetic samples is integrated with a detailed biostratigraphy and lithostratigraphy. The tilt-corrected mean direction from the West Pingdingshan section, passes the reversal and fold tests. The overall mean direction after tilt correction is D=299.9º, I=18.3º (κ=305.2, α95=1.9, N=19). The inferred paleolatitude of the sampling sites (31.6ºN, 117.8ºE) is about 9.4º, consistent with the stable South China block (SCB), though the declinations indicate some 101o counter-clockwise rotations with respect to the stable SCB since the Early Triassic. Low-field anisotropy of magnetic susceptibility indicates evidence of weak strain. The lower part of the Yinkeng Formation is dominated by reversed polarity, with four normal polarity magnetozones (WP2n to WP5n), with evidence of some thinner (<0.5 m thick) normal magnetozones. The continuous magnetostratigraphy from the Yinkeng Formation, provides additional high-resolution details of the polarity pattern through the later parts of the Induan into the lowest Olenekian. The magnetostratigraphic and biostratigraphic data shows the conodont marker for the base of the Olenekian (first presence of Neospathodus waageni) is shortly prior to the base of normal magnetozone WP5n. This provides a secondary marker for mapping the base of the Olenekian into successions without conodonts. This section provides the only well-integrated study from a Tethyan section across this boundary, but problems remain in definitively relating this boundary into Boreal sections with magnetostratigraphy

Datos paleomagnéticos en materiales sin-diapíricos Aptienses-Albienses (cuenca Vasco-Cantábrica, N Iberia)

In order to obtain a kinematic model linking the diapir formation and the geometry of the syn-diapir sediments, a paleomagnetic study has been conducted in selected syn-diapiric sequences of the Basque-Cantabrian Basin. The studied diapirs (Bakio, Bermeo, Guernika and Mungia) developed during the Early Cretaceous in relation to the North Iberian extensional margin which was subsequently reactivated during the Pyrenean contractional deformation (Late Cretaceous-Miocene). They are cored by Triassic red clays and evaporites and they are flanked by synkinematic Albian shelf and slope carbonates and Upper Albian to Cenomanian siliciclastics. The paleomagnetic study has focused on the synkinematic overburden to detect and quantify vertical axis rotations related to the growth of the diapirs. 29 paleomagnetic sites have been analyzed. After obtaining the site mean directions it can be concluded that most of the sites are remagnetized, hindering the kinematics of the diapirs growth to be deduced. The age of this remagnetization is difficult to assess, it could be either an earlier Albian-Maastrichtian remagnetization or a remagnetization linked to the Pyrenean compression.Trabajo financiado gracias a los proyectos coordinados CGL2014-54118-C2-1-R y CGL2014-54118-C2-2-R y al GGAC 2014SGR467Peer Reviewe

Arqueologia i globalització. Una reflexió des de l'Arqueologia medieval.

[spa] Este artículo presenta una reflexión sobre los cambios que han tenido lugar en la Arqueologia en los últimos 25 años, con una especial inflexión en la Arqueologia medieval, desde el propio concepto de Arqueologia y sus límites cronológicos hasta la aplicación de las nuevas tecnologias. Pero sobre todo es un planteamiento de las consecuencias que la globalización puede tener sobre los yacimientos y la investigación local. [fra] Archéologie et globalisation. Une réflexion de l"Archéologie médiévale Cet article présente une réflexion sur les changements que l"Archéologie a subi au cours des vingtcinc dernières années, avec une inflexion particulière en Archéologie médievale, de la notion même de l"Archéologie et les limites chronologiques à l"application des nouvelles technologies. Mais surtout, c"est une approche sur les effets que la globalisation peut avoir sur les sites archéologiques et la recherche locale

Eocene-Oligocene magnetostratigraphy from the central part of the SE margin of the Ebro Basin

Previous magnetostratigraphic studies focused in the Eocene successions of the eastern Ebro Basin have provided some absolute age for the basin infill. These results were based on some biostratigraphic constraints wich have been recently challenged. Our new results from the approximately 3000 m thick Montserrat and Maians-Rubió magnetostratigraphic sections have been integrated into the both marine and continental biochronology data, providing a more independent chronology. The resulting absolute chronology of the Montserrat-Rubió composite section represents about 10 My, covering the Lutetian to Rupelian (approximately 40.7 to 30.5 Ma). This leads to the re-evaluation of the age of the La Salut Fm. (Lutetian to Bartonian) and the Montserrat conglomerates (Bartonian to Priabonian). The last marine regression in the central part of the SE margin of the Ebro Basin yields an approximate age of about 36.0 Ma (Priabonian)