59 research outputs found
Early Triassic-Anisian continental sediments from SE Iberian ranges: sedimentological and mineralogical features
Depto. de MineralogĂa y PetrologĂaFac. de Ciencias GeolĂłgicasTRUEpu
MineralogĂa, sedimentologĂa y paleosuelos del evento pluvial del Carniense (CPE) en el este de España: indicadores de humedad y variaciones del nivel del mar
Depto. de MineralogĂa y PetrologĂaFac. de Ciencias GeolĂłgicasTRUEpu
Palaeogeographical significance of clay mineral assemblages in the Permian and Triassic sediments of the SE Iberian Ranges, eastern Spain
The evolution of the palaeogeography of the SE Iberian Basin during the Permian and Triassic represents a general
evolution from continental to marine environments. It has been recently studied from the sedimentological,
stratigraphical, tectonic and palaeontological points of view. In spite of these results, many aspects of this
palaeogeography are still a matter of discussion. In this study, clay mineralogy analysis complements previous studies
representing a new aspect for understanding the evolution of the sedimentary environment and the palaeogeography
of the Iberian Basin during the periods in question and thus of the palaeogeography and the location of the major
high areas in the westernmost border of the Tethys sea.
In spite of late diagenetic transformations the original clay mineral associations of the Permian-Triassic sediments
of the SE Iberian Ranges can be reconstructed. Seventy-seven samples of siliciclastic and carbonate sediments of these
ages have been studied (SEM and XRD), revealing six new aspects that help to precise the palaeogeographical
interpretation of the area:
(1) Two major mineral assemblages have been found: illite+ kaolinite +pyrophyllite in the continental facies and
illite + chlorite + vermiculite + mixed-layer clays in the marine facies.
(2) The Mg-rich clay minerals are here considered to be of marine origin.
(3) Active phases of basin boundary faults are marked in the sediments by the presence of pyrophyllite, derived
directly from the Palaeozoic metamorphic basement.
(4) Unconformities separating major depositional sequences also separate formations with different clay mineralogy.
(5) Different groups of clay minerals can be separated clearly coinciding with the different palaeogeographical
stages also distinguished in the westernmost border of the Tethys sea.
(6) The clay mineral associations back up the data of a previous hypothesis of a humid climate for the end of the
Permian in the study area just prior to the first incursion of the Tethys sea
Palaeoenvironmental significance of Late Permian palaeosols in the South-Eastern Iberian Ranges, Spain
The Late Permian (Wuchiapingian) Alcotas Formation in the SE Iberian Ranges
consists of one red alluvial succession where abundant soil profiles developed.
Detailed petrographical and sedimentological studies in seven sections of
the Alcotas Formation allow six different types of palaeosols, with
distinctive characteristics and different palaeogeographical distribution, to be
distinguished throughout the South-eastern Iberian Basin. These characteristics
are, in turn, related to topographic, climatic and tectonic controls. The vertical
distribution of the palaeosols is used to differentiate the formation in three parts
from bottom to top showing both drastic and gradual vertical upwards
palaeoenvironmental changes in the sections. Reconstruction of
palaeoenvironmental conditions based on palaeosols provides evidence for
understanding the events that occurred during the Late Permian, some few
millions of years before the well-known Permian-Triassic global crisis
The graphite deposit at Borrowdale (UK): A catastrophic mineralizing event associated with Ordovician magmatism
The volcanic-hosted graphite deposit at Borrowdale in Cumbria, UK, was formed through precipitation from CâOâH fluids. The ÎŽ13C data indicate that carbon was incorporated into the mineralizing fluids by assimilation of carbonaceous metapelites of the Skiddaw Group by andesite magmas of the Borrowdale Volcanic Group. The graphite mineralization occurred as the fluids migrated upwards through normal conjugate fractures forming the main subvertical pipe-like bodies. The mineralizing fluids evolved from CO2âCH4âH2O mixtures (XCO2 = 0.6â0.8) to CH4âH2O mixtures. Coevally with graphite deposition, the andesite and dioritic wall rocks adjacent to the veins were intensely hydrothermally altered to a propylitic assemblage. The initial graphite precipitation was probably triggered by the earliest hydration reactions in the volcanic host rocks. During the main mineralization stage, graphite precipitated along the pipe-like bodies due to CO2 â C + O2. This agrees with the isotopic data which indicate that the first graphite morphologies crystallizing from the fluid (cryptocrystalline aggregates) are isotopically lighter than those crystallizing later (flakes). Late chloriteâgraphite veins were formed from CH4-enriched fluids following the reaction CH4+O2 â C + 2H2O, producing the successive precipitation of isotopically lighter graphite morphologies. Thus, as mineralization proceeded, water-generating reactions were involved in graphite precipitation, further favouring the propylitic alteration. The structural features of the pipe-like mineralized bodies as well as the isotopic homogeneity of graphite suggest that the mineralization occurred in a very short period of time
New ichnites from the Middle Triassic of the Iberian Ranges (Spain): paleoenvironmental and paleogeographical implications
The Iberian Basin or its present-day expression, the Iberian Ranges, was refilled with red bed sediments of alluvial origin during the late OlenekianâAnisian period represented by the Cañizar (OlenekianâAnisian) and Eslida (Anisian) Formations, both commonly known as Buntsandstein facies. In the late part of the Anisian, the Tethys Sea reached the eastern side of the Iberian microplate, represented by the shallow marine facies of the Landete and Cañete Formations, also called Muschelkalk facies. The ichnites studied in this paper belong to the Anisian continental-marine transition in the SE Iberian Ranges. The Cañizar Formation shows the oldest Triassic footprints found in the Iberian Peninsula, consisting in swimming, uncomplete lacertoid three digit Rhynchosauroides traces with possibly resting (cubichnia) and furrowing (pascichnia) Cruziana/Rusophycus due to large triopsids. Specimens from LacertoĂŻd and CrocodiloĂŻd groups have been collected in the Eslida Formation. Rhynchosauroides sp. is the most representative ichnospecies of the first group, while in the CrocodiloĂŻd group, the presence of Chirotherium barthii Kaup 1835 and Isochirotherium cf coureli (Demathieu 1970) are distinctive.
In the Landete Formation specimens are found from CrocodiloĂŻd and DinosauroĂŻd groups. Brachychirotherium gallicum Willruth 1917, Brachychirotherium sp. and Chirotherium sp. are characteristic of the first one, and âCoelurosaurichnusâ perriauxi and cf Paratrisauropus latus as the most representative of the second group.
Some of the specimens described here present ancestors in the Early Triassic and have been described in the Triassic of North America, Italy and France. Possible paleogeographical connections with faunas of SE France can be inferred. Based on different sedimentary structures and plant remains, the footprints are related to fluvial systems within huge flood plains, playa and shallow marine environments, with alternating dry and wet periods. The vertical ichnites distribution during the Anisian shows that the fauna modification was weak at a high clade level. In the Triassic of the Iberian microplate, there are no findings of traces prior to the Anisian, and the footprint content for the Middle Triassic is less diversified than in other neighbouring regions. By comparison with other western Pangea areas, there was a later appearance of the forms after the end-Permian mass extinction event in the studied areaDepto. de MineralogĂa y PetrologĂaFac. de Ciencias GeolĂłgicasTRUEMinisterio de EconomĂa y Competitividad (MINECO)UCM-BSCH-GR58/08pu
Field trip guide and abstracts of the sepiolite symposium : june 7th, 2010, Madrid-Seville, Spain /2010 SEA-CSSJ-CMS Trilateral Meeting on Clays
Depto. de MineralogĂa y PetrologĂaFac. de Ciencias GeolĂłgicasTRUEpu
The Anisian continental-marine transition in Sardinia (Italy): state of the art, new palynological data and regional chronostratigraphic correlation
The scarce evidence of paleontological records between the upper Permian and the Anisian (Middle Triassic) of Western Europe could reflect (1) large stratigraphic gaps in the continental successions and/or (2) the persistence of disturbed conditions after the PermianâTriassic Boundary extinction event and the succession of ecological crises that occurred during the Early Triassic. In this context, the study of palynological associations, integrated with the stratigraphical and sedimentological data, plays a key role in dating and correlating the successions of the Western European domain and improves our understanding of environmental and paleoclimatic conditions. In some cases, pre-Anisian paleontological evidence is lacking, as in Sardinia (Italy), where a long gap encompasses the middle Permian (pars) to late Lower Triassic successions. Although fragmented and disseminated, the continental Lower-Middle Triassic sedimentary successions (Buntsandstein) of Sardinia have proved crucial to our understanding of the evolution of the southern edge of the Paleo-Europe and the different timings of the Tethys transgression (Muschelkalk facies) in some of these areas. Various paleogeographic reconstructions were attempted in previous works, without providing any consensus on the precise position of Sardinia and its surrounding seaways in the Western Tethys domain during this time interval. At present, the configuration and distribution of the subsiding and emerging landmasses and the temporal development of the transgressions of the Western Tethys during the Middle Triassic remain unclear. This work focuses on the stratigraphical, sedimentological and palynological aspects of three Middle Triassic continental-marine sedimentary successions in Sardinia, with particular attention to the analysis of the palynological associations sampled there, and it also provides a detailed review of all previous palynological publications on the Sardinian Anisian. The studied successions are: Su Passu Malu section (Campumari, SW Sardinia), Arcu is Fronestas section and Escalaplano section (Escalaplano, Central Sardinia). These sections were also correlated to other significant sections in the SW (Scivu Is Arenas) and NW (Nurra) parts of the island
AnĂĄlisis de la evoluciĂłn en la adquisiciĂłn de competencias especĂficas y transversales en los Grados de GeologĂa e IngenierĂa GeolĂłgica
Depto. de MineralogĂa y PetrologĂaFac. de Ciencias GeolĂłgicasFALSEsubmitte
Material audiovisual para el mural "El Tiempo en GeologĂa" de la Facultad de Ciencias GeolĂłgicas
La GeologĂa abarca toda la historia del planeta, por lo que se hace inviable utilizar conceptos temporales de nuestra vida cotidiana. Por ello, se ha realizado un friso para el hall de la Facultad y para presentarlo, se ha realizado un vĂdeo explicativo del mismo
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