Search

[EN] The environmental changes leading up to the first continent-wide glaciation of Antarctica during the Eocene-Oligocene Transition (EOT) are still not fully understood. Declining atmospheric CO2 concentrations and associated feedbacks have been invoked as underlying mechanisms, but the role of the coeval opening/deepening of Southern Ocean gateways (Drake Passage and Tasman Gateway), and subsequent changes in paleoceanography remain poorly understood. Evidence suggests both a temperate late Eocene and cooling before the EOT, both broadly coetaneous with a wide, supra-regional diagenetic event that resulted in green-clay (glaucony) formation in the marine realm around Antarctica (Houben et al., 2019; López-Quirós et al., 2019). Glaucony formation and evolution are driven by the activity of bacteria thriving in the organic-rich environment, a bio-geochemical system now considered to play a key role in the control of global ocean chemistry. Investigation of the reaction mechanisms throughout the formation of glaucony provides reliable information about (i) macro-scale environmental conditions, such as ocean transgression-regression cycles and ocean circulation changes, and (ii) the micro-scale sedimentary environment, such us sediment permeability, ion mobility and organic matter content – all of which are registered in the fabric and crystal-chemical characteristics of glaucony (e.g., López-Quirós et al., 2019; 2020; 2023). In addition, K-Ar dating of glaucony has provided 40% of the absolute-age dates for the geological timescale of the past 250 Ma. Glaucony is thus an important tool to date depositional ages of sediments and to reconstruct paleoenvironmental conditions. In spite of all, the nature, depositional setting, paleoenvironmental implications and chronology of the late Eocene glaucony reported in diverse shallow-marine settings in the Southern Ocean are loosely constrained (López-Quirós et al., 2019). In this contribution we describe, for the first time

[EN] The historyof surface uplift rates in the Iberian Meseta, as well as the deep and shallow mechanisms that generated and currently support its characteristic elevated topography, are still debated.The objective of our project is to quantify the degree to which contributions to topography in the Iberian Meseta partition into crustal, lithospheric mantle, and sublithospheric mantle dynamic processes.

[EN] The GI-CARTO research group is articulated around geological mapping as a research methodology developed in many projects. The activities of the team can be distributed in various working lines: 1.-Research activities devoted to the solving of specific geological problems 2.-Systematic geological mapping 3.-Implementation of a new geological information model 4.-Edition and preparation of new geological maps 5.-International activitie

Las remagnetizaciones químicas regionales relacionadas con procesos de enterramiento y diagénesis son un proceso ampliamente extendido en cuñas orogénicas y cuencas sedimentarias. Este proceso conlleva la neoformación autigénica de minerales ferromagnéticos s.l. en relación con el aumento de temperatura asociado al enterramiento. Sin embargo, todavía no se conoce bien la cinética de estos procesos, debido en parte a que la mayoría de las remagnetizaciones de este tipo descritas en la literatura científica se produjeron durante supercrones magnéticos. Los materiales turbidíticos eocenos de la Cuenca de Jaca (Pirineos Occidentales) muestran una remagnetización química de doble polaridad, registrando varios crones a lo largo de la secuencia sedimentaria remagnetizada. Dentro del proyecto UKRIA4D (PID2019-104693GB-I00/CTA), se va a realizar un estudio multidisciplinar para relacionar temperatura de enterramiento, mineralogía magnética y edad de la remagnetización con la que evaluar de manera empírica las relaciones cinéticas entre los distintos factores.

Burial diagenesis is one of the main mechanisms claimed for explaining pervasive remagnetizations in sedimentary basins and orogenic wedges worldwide. It involves authigenic formation (e.g. chemical remagnetization) of magnetic minerals in response to enhanced temperature conditions at deep basinal positions. Key questions about the kinetics of this process in natural cases remain unsolved because most of the best-documented cases occurred during long-lasting magnetic superchrons. The Western Pyrenees display a dual polarity record of a burial remagnetization affecting the deepest part of the Eocene Jaca turbiditic basin and its underlying units. A preliminary study of 49 sites distributed along three cross sections reveals that postfolding (remagnetized) ChRM directions are found within the lowermost part of the studied sedimentary pile, which is affected by cleavage, in such a way that ChRM unblocking temperatures increase as a function of depth. Noteworthy, this remagnetization is associated with hysteresis data typical for chemical remagnetizations (samples falling mainly within the SP+SD+MD mixing line in the Day plot), and displays up to five different polarity zones that are consistent along strike in the three studied cross sections. Prefolding ChRM directions are found, in contrast, in the overlying sequence above the cleavage domain. We intend to carry out a detailed, multidisciplinary study of this remagnetization in the framework of the recently funded UKRIA4D project, that will integrate: A) a full characterization of the remagnetization front combining paleomagnetic and rock-magnetic data; B) characterization of the burial conditions based on SEM and TEM observations of mineral assemblages and temperature estimates from RAMAN spectroscopy on carbonaceous material; and C) magneto-biostratigraphic dating of the 7 km-thick overlying sedimentary sequence. Integration of these data will allow establishment of the burial conditions that led to the observed r

The Paleocene (66¿56 Ma) was a critical time interval for understanding the geological history in high palaeolatitudes after the end of Cretaceous event (recovery from mass extinction, palaeoclimate, global sea level changes, among others). The sedimentary succession from Seymour Island (Antarctic Peninsula) provides key reference material from this important phase of the early Cenozoic. A detailed age model is proposed for the López de Bertodano Formation (LBF), Sobral Formation (SF) and Cross Valley¿Wiman Formation (CVWF) based on a new magnetostratigraphic section which integrates previous dinoflagellate cyst biostratigraphy, Iridium anomaly (K-Pg boundary), U-Pb zircon dating (airfall tuff) and strontium isotope values from macrofossils. The new composite magnetostratigraphic section, which includes the Cretaceous¿Paleogene boundary, has been correlated to the GPTS from C29r up to C24r. The top of the LBF is confirmed as latest Maastrichtian to earliest Danian (~65.4 Ma) in age. The overlying SF is mostly Danian in age (~65.2¿ ~63 Ma) and CVWF is Selandian¿Thatenian (~61.3¿56.9 Ma). LBF, SF and CVWF are unconformity-bounded units (alloformations) that record the geological evolution of the James Ross Basin during a period of relative decreasing tectonism but coeval with volcanic activity. Unconformity based internal units have been recognized, dividing each formation into allomembers (LBF: Molluscan and Cenozoic; SF: A, B and C; CVWF: Díaz, Arañado, Bahía Pingüino). The new age model allows correlation of base-level changes with eustatic sea-level fluctuations. The bases of the SF and CVWF are correlated with the 65.3 and 61.5 Ma sea level lowstands.

La cartografía geológica es la disciplina que, empleando diversas técnicas, expresa mediante una representación gráfica la información geológica referida a un sector de la corteza terrestre. El producto resultante es el Mapa Geológico que es la figuración sobre un plano, de la naturaleza, distribución espacial y relaciones geométricas de los materiales que afloran en la superficie terrestre, observables tanto directa como indirectamente y representables, a una escala determinada, sobre una base topográfica o cualquier otro soporte de información geográfica.

La Sierra de O Barbanza se sitúa entre la Ría de Arousa al sur y la de Muros-Noia al norte, en la costa Atlántica gallega. El curso alto del río Barbanza discurre por una superficie de poca pendiente, en un valle abierto a favor de fracturas de dirección NW-SE. El curso del río tiene un trazado sinuoso controlado por el patrón de fracturación, en el que se observan acumulaciones sedimentarias desarrolladas en los tramos caracterizados por cambios en la dirección del cauce. A lo largo del curso se han localizado yacimientos arqueológicos que cubren un amplio rango cronológico. Los túmulos y los petroglifos se sitúan preferentemente en partes altas y las estructuras de “chozas o cabañas” se emplazan en los sectores de acumulación aluvial, al pie de las laderas y relativamente alejadas del curso actual del río. La secuencia edafosedimentaria estudiada, situada en la superficie aluvial de mayor dimensión del tramo fluvial, está en un contexto arqueológico. Los resultados sugieren que el yacimiento se ha emplazado sobre una pequeña llanura aluvial, formada por sedimento arenoso con alto contenido en limos y arcillas, sobre la que se acumularon materiales procedentes de las laderas graníticas, ricos en gravas y macrocarbones. Los resultados permiten identificar una superficie aluvial, sobre la que se levantan estructuras arqueológicas, que son fosilizadas por material coluvial. Se han realizado dos dataciones radiocarbónicas en fragmentos de carbón. La más antigua, a 82 cm de profundidad, ubicada en la transición entre los niveles edafo-sedimentarios identificados como facies aluvial y la coluvial, es un fragmento de carbón de Quercus caducifolio, proporcionó una fecha cal BP de 8595-8455 (cal BC 6645-6505). La segunda, a 40 cm de profundidad, sobre un fragmento de carbón de Erica sp., aportó la edad cal BP de 1235-1205 (cal AD 715-745)., The O Barbanza mountain range is located between the Ria de Arousa to the south and the Ria de Muros-Noia to the north, on the Atlantic coast of Galicia. The upper reaches of the Barbanza river flow through a gently sloping area with an open valley following fractures in a NW-SE direction. The course of the river follows a winding path directed by the pattern of fracturing, in which sediment has accumulated in sections characterized by changes in the direction of the channel. Along the course of the river, archaeological sites have been located spanning a wide chronological range. Mounds and petroglyphs are preferably located in high places and structures of “huts” are located in areas with alluvial accumulation at the foot of the slopes, slightly away from the current course of the river. The pedo-sedimentary sequence studied, located in the largest alluvial plain of the stretch of river, is set in an archaeological context. The results suggest that the site is located on an alluvial plain formed by sandy sediments with a high content of silt and clay. Material originating from the granite slopes, and rich in gravels and macrocharcoals, fossilized on this alluvial plain. The results allow us to identify an alluvial surface on which archaeological structures were built, which have been fossilized by colluvial material. Radiocarbon dating was carried out on two charcoal fragments. The oldest, located at a depth of 82 cm, in the transition between the pedosedimentary levels identified as alluvial and colluvial facies, consists of a fragment of deciduous Quercus charcoal, with a date of 8595-8455 cal BP (6645-6505 cal BC). The second, at a depth of 40 cm, on a piece of Erica sp. charcoal, was dated at 1235 to 1205 cal BP (cal AD 715-745)

La costa sur de Bahía Esperanza se sitúa en el extremo septentrional de la Península Antártica. La cubierta glaciar de la zona corresponde a los glaciares Buenos Aires, Depot, Kenney y Flora, éste última actualmente reducido a un glaciar de circo. Gran parte de este territorio presenta evidencias de la actividad glaciar pasada y de los fenómenos periglaciares que posteriormente la afectaron, además de otras formas ligadas al litoral. Durante el Último Máximo Glaciar (LGM), el casquete que cubría la península Antártica alcanzó espesores entre 150-400 m mayores que los actuales y se extendió unos 200 km hacia el E y NE de la actual línea de costa. La transición al Holoceno interglaciar se completa cuando se alcanzan volúmenes y una configuración de hielo similar al actual. caracterizándose por la aparición de lagos de agua dulce en tierra y por la ocupación de terrenos costeros por pingüineras.

El presente libro, titulado "Comprendiendo el relieve: del pasado al futuro", constituye la expresión gráfica de los trabajos presentados en la XIV Reunión Nacional de Geomorfología, celebrada en la ciudad de Málaga entre los días 22 y 25 de junio de 2016.

Bahia Esperanza, constituting the NE tip of the Antarctic Peninsula, is made up of Paleozoic clastic sedimentary rocks overlain by a Jurassic volcano-sedimentary series and intruded by Cretaceous gabbros and diorites. The area is located along the southern part of the Pacific Margin magnetic anomaly belt. Field magnetic researches during February 2010 contribute to determining the deep geometry of the intermediate and basic intrusive rocks. Moreover, the new field data help constrain the regional Pacific Margin Anomaly, characterized up to now only by aeromagnetic and marine data. Field magnetic susceptibility measurements of intrusive intermediate and basic rocks, responsible for magnetic anomalies, ranges from 0.5 × 10− 3 SI in diorites to values between 0.75 × 10− 3 SI and 1.3 × 10− 3 SI in gabbros. In addition, a significant remanent magnetism should also have contributed to the anomalies. The regional magnetic anomaly is characterized by a westward increase from 100 nT up to 750 nT, associated with large intrusive diorite bodies. They probably underlie most of the western slopes of Mount Flora. Gabbros in the Nobby Nunatak determine local residual rough anomalies that extend northwards and westwards, pointing to the irregular geometry of the top of the basic rocks bodies below the Pirámide Peak Glacier. However, the southern and eastern boundaries with the Buenos Aires Glacier are sharp related to deep glacier incision. As a result of the glacier dynamics, magnetic anomalies are also detected north of the Nobby Nunatak due to the extension of the anomalous body and the presence of gabbro blocks in the moraines. The Bahia Esperanza region is a key area where onshore field geological and magnetic research allows us to constrain the shape of the crustal igneous intrusions and the basement glacier geometry, providing accurate data that complete regional aeromagnetic research

Bahia Esperanza, constituting the NE tip of the Antarctic Peninsula, is made up of Paleozoic clastic sedimentary rocks overlain by a Jurassic volcano-sedimentary series and intruded by Cretaceous gabbros and diorites. The area is located along the southern part of the Pacific Margin magnetic anomaly belt. Field magnetic researches during February 2010 contribute to determining the deep geometry of the intermediate and basic intrusive rocks. Moreover, the new field data help constrain the regional Pacific Margin Anomaly, characterized up to now only by aeromagnetic and marine data. Field magnetic susceptibility measurements of intrusive intermediate and basic rocks, responsible for magnetic anomalies, ranges from 0.5 × 10− 3 SI in diorites to values between 0.75 × 10− 3 SI and 1.3 × 10− 3 SI in gabbros. In addition, a significant remanent magnetism should also have contributed to the anomalies. The regional magnetic anomaly is characterized by a westward increase from 100 nT up to 750 nT, associated with large intrusive diorite bodies. They probably underlie most of the western slopes of Mount Flora. Gabbros in the Nobby Nunatak determine local residual rough anomalies that extend northwards and westwards, pointing to the irregular geometry of the top of the basic rocks bodies below the Pirámide Peak Glacier. However, the southern and eastern boundaries with the Buenos Aires Glacier are sharp related to deep glacier incision. As a result of the glacier dynamics, magnetic anomalies are also detected north of the Nobby Nunatak due to the extension of the anomalous body and the presence of gabbro blocks in the moraines. The Bahia Esperanza region is a key area where onshore field geological and magnetic research allows us to constrain the shape of the crustal igneous intrusions and the basement glacier geometry, providing accurate data that complete regional aeromagnetic research