Conference papers by David Gomez Gras
Geofluids VIII conference, 2016
The Montjuïc hill is a tilted block formed by middle Miocene sandstones, located within the Barce... more The Montjuïc hill is a tilted block formed by middle Miocene sandstones, located within the Barcelona Plain (NE Spain). This block is part of the horst and graben system that was developed by NE-SW faults during the Neogene extension. These sandstones are affected by a strong silicification only in this uplifted block whereas they are unsilicified in core samples around the hill. After silicification, an intense fracturing occurred. Fractures crosscutting the silicified area are characterized by a cementation sequence defined by barite followed by silica±iron oxides. Barite is only found in the fractures along the uppermost 40 m below the present-day surface and precipitated from the mixing of upflowing seawater, as indicated by sulphur and oxygen isotopes, and percolating meteoric water, which supplied Ba and radiogenic Sr. Consequent silica precipitation, defined by opal to quartz sequences, is characterized by the formation of stalactites, illuviation structures and shrinkage cracks pointing to its vadose meteoric origin. The alternation between silica and iron oxides may reflect small fluctuations from reducing to oxidizing conditions, probably related to oscillations of the water table level produced by episodic rainfall/evaporation or seasonality (wet and dry periods). Thus, a model of fracture silicification is proposed: during dry periods, silica dissolution occurs due to alkaline conditions whereas at the onset of the wet season, the entry of the acid rainwater lows the pH producing silica precipitation. Low pH conditions are supported by the presence of alunite. Oxygen values of silica speleothems up to +25‰VSMOW may indicate that silica precipitation occurred during a cold period after the Pliocene uplift.
Book Chapters (Iberian Prehistory) by David Gomez Gras
Crafting pottery in Bronze Age Europe: the archaeological background of the CRAFTER project, 2021
In the Argaric society, developed during the Early Bronze Age (c. 2200–1550 BC) in the south-east... more In the Argaric society, developed during the Early Bronze Age (c. 2200–1550 BC) in the south-east of the Iberian Peninsula, a ruling class emerged, which controlled the land and the basic means of production. In view of the available evidence concerning the centralisation of cereal surplus as well as other products in certain settlements and buildings, we hypothesize that a group of high-ly standardized ceramic repertoire of classical El Argar (c.1900–1550 cal BC), distributed in 8 basic shapes, was produced by specialised potters and fulf lled specific functions in the storage, distribution and transformation of subsistence goods. In this research we have studied an import-ant assemblage of vessels from the El Argar coastal areas of Murcia and Almería (Spain) focusing on its production and use, through petrographic, organic residues, volumetric capacity, and usewear analyses. This interdisciplinary analytical approach to pottery is surprisingly rare in pottery studies but seems crucial in order to better understand the social, political and economic dimension of the El Argar pottery.
Papers by David Gomez Gras
Geogaceta, 2017
espanolEl analisis de minerales pesados es una tecnica que permite precisar sobre la procedencia ... more espanolEl analisis de minerales pesados es una tecnica que permite precisar sobre la procedencia de los materiales detriticos, asi como su historia diagenetica y las caracteristicas energeticas de su ambiente de sedimentacion. Esta tecnica, juntamente con un analisis petrografico cuantitativo, se aplica por primera vez en los materiales del Cretacico Superior de la cuenca surpirenaica central, en las Sierras Marginales y Sierras Exteriores. El presente trabajo estable ce las asociaciones de minerales pesados y la petrografia de los materiales del Santoniense y Maastrichtiense en un momento clave de la evolucion de la cuenca surpirenaica central, en el que se produce la inversion de cuencas previas, y el registro mas temprano de la sedimentacion detritica de la cuenca de antepais. Las asociaciones empobrecidas de minerales pesados, junto a la madurez composicional elevada que muestran dichas areniscas (cuarzoarenitas y arcosas con feldespato potasico), sugieren que estos sedimentos han estado sometidos a una intensa disolucion que ha modificado profundamente su composicion original. Dicha composicion fue alterada por los procesos de meteorizacion acaecidos en el area fuente, por la abrasion mecanica durante el transporte y por la diagenesis durante el enterramiento acompanada de la circulacion de aguas acidas. EnglishHeavy-mineral analysis allows constraining provenance of detrital materials as well as their diagenetic history and the energetic characteristics of depositional environment. This technique, coupled with sandstone petrography, is applied for the first time to the Upper Cretaceous materials of the south-central Pyrenean basin, in the Sierras Marginales and Sierras Exteriores. The present paper determines the heavy-mineral suites and the petrography of the Santonian and Maastrichtian materials during a key moment of the south-central Pyrenean basin evolution, in which the inversion of the previous extensio nal basins occurs together with the earliest record of the detrital sedimentation of the foreland basin. The impoverished heavy-mineral assemblages, together with the high compositional maturity displayed by the Upper Cretaceous sandstones of the south-central Pyrenean basin (quartzarenites and K-feldspar arkoses), suggest that these sediments where affected by an intense dissolution which have strongly modified their original signal. Such composition was modified due to weathering processes that occurred at the source area,to mechanical breakdown during transport and to diagenesis during burial accompanied by acid-water circulation.
Geogaceta, 2017
espanolLa secuencia de Jaca registra un cambio paleogeografico importante en la cuenca surpirenai... more espanolLa secuencia de Jaca registra un cambio paleogeografico importante en la cuenca surpirenaica central, registrado por la sedimentacion marina, representada por las turbiditas del Grupo de Hecho (Luteciense), por ambientes deltaicos y aluviales (Bartoniense-Priaboniense). Este trabajo estudia las asociaciones de minerales pesados de los sistemas clasticos eocenos de la parte norte de la cuenca de Jaca, mediante el analisis petrografico y la espectrometria Raman. Todos los sistemas muestran asociaciones empobrecidas, constituidas basicamente por oxidos de titanio, apatito, zircon y turmalina. En los sistemas aluviales, en cambio, se identifican otros minerales, como estauro lita, pirita alterada, goethita y hematites. Los resultados muestran un cambio importante en las asociaciones de minerales pesados en la transicion desde los depositos turbiditicos hasta los someros y continentales. Los sistemas turbiditicos muestran elevadas proporciones de apatito, con un area fuente en la Zona Axial de los Pirineos Orientales, mientras que los sistemas aluviales se caracterizan por un contenido elevado en goethita y por la presencia de estaurolita. Se interpreta que el cambio se relacionaria con el inicio del emplazamiento del cabalgamiento de Gavarnie, que provoco el levantamiento de las turbiditas y la exhumacion del basamento paleozoico al norte de la cuenca de Jaca. EnglishThe Jaca sequence records a major paleogeographic change in the south-central-pyrenean basin, recorded by the replacement of the deep-marine Hecho Group turbidites (Upper Lutetian) by deltaic and alluvials (Bartonian-Priabonian). This work studies the heavy-mineral assemblages of the Eocene clastic systems in the northern Jaca basin, applying o ptical analysis and Raman spectroscopy. All the clastic systems display impoverished heavy-mineral suites, mainly constituted by titanium oxides, apatite, zircon and tourmaline. Other heavy minerals, as staurolite, weathered pyrite, goethite and hematite, are found in the alluvial systems. Our results show a major heavy-mineral content shift along the transition from turbidites to shallow-water and continental deposits. The turbiditic systems display high content of apatite sourced from the Axial Zone in the eastern Pyrenees, whereas the alluvial systems are characterized by a heavy-mineral suite containing goethite and staurolite. The shift is here interpreted as related to the onset of the Gavarnie thrust, which resulted in the uplift and recycling of the turbidites as well as the exhumation of Paleozoic basement, located to the north of the Jaca basin.
Palaeogeography, Palaeoclimatology, Palaeoecology, 2007
... Cited By in Scopus (2). Permissions & Reprints. Triassic magnetic overprints rela... more ... Cited By in Scopus (2). Permissions & Reprints. Triassic magnetic overprints related to albitization in granites from the Morvan massif (France). ... An Early Triassic magnetic overprint has been recorded in the albitized basement rocks of the Morvan massif. ...
Geologica Acta, 2007
The Oligocene deposits of Montgat are integrated in a small outcrop made up of Cenozoic and Mesoz... more The Oligocene deposits of Montgat are integrated in a small outcrop made up of Cenozoic and Mesozoic rocks located in the Garraf-Montnegre horst, close to the major Barcelona fault. The Oligocene of Montgat consists of detrital sediments of continental origin mainly deposited in alluvial fan environments; these deposits are folded and affected by thrusts and strike-slip faults. They can be divided in two lithostratigraphic units separated by a minor southwest-directed thrust: (i) the Turo de Montgat Unit composed of litharenites and lithorudites with high contents of quartz, feldspar, plutonic and limestone rock fragments; and (ii) the Pla de la Concordia Unit composed of calcilitharenites and calcilithorudites with high contents of dolosparite and dolomicrite rock fragments. The petrological composition of both units indicates that sediments were derived from the erosion of Triassic (Buntsandstein, Muschelkalk and Keuper facies), Jurassic and Lower Cretaceous rocks (Barremian to Ap...
Ongoing civil engineering works in the city of Barcelona have allowed getting new data on lhe str... more Ongoing civil engineering works in the city of Barcelona have allowed getting new data on lhe stratigraphy of the Pia de Barcelona minor graben. The tectonic evolution ofmis small basin is divided in a Palacogene compression phase and a Neogene extensional one. Even though sedimentation already occurred during the compression stage, the bulk of sediments was deposited during the extensional one. The study ofseveral geological cores has shown that the earliest layers deposited during this extensional phase correspond to alluvial fan sediments that were provisionally referred to the early Miocene (Mi-Ia unit). The study of the rodent remains recovered from these samples allows refining the dating and assign an age of 17 to 14.5 Ma to this lithostratigraphic unit.
Journal of Geochemical Exploration, 2006
Advances in Biochemical Engineering/Biotechnology
Boletin Geologico Y Minero, 1990
Revista De La Sociedad Geologica De Espana, 2014
Uploads
Conference papers by David Gomez Gras
Book Chapters (Iberian Prehistory) by David Gomez Gras
Papers by David Gomez Gras