P.A. Fernández‐Mendiola

University of the Basque Country

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J. García‐Mondéjar

University of the Basque Country

M.A. López-Horgue

University of the Basque Country

Hugh Owen

Natural History Museum

Irene Gómez-Pérez

Society of Economic Geologists

Arantza Aranburu

University of the Basque Country

Isabel Pérez Millán

University of Alicante

Eneko Iriarte

Centro de Epilepsia y Neurocirugía Funcional

Bruno Caline

Fondation de Coopération Scientifique

Jone Mendicoa

University of the Basque Country

Idoia Rosales

Instituto Geológico y Minero de España

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University of the Basque Country

Total (France)

IFP Énergies nouvelles

Sorbonne Université

Universitat de València

Friedrich-Alexander-Universität Erlangen-Nürnberg

ETH Zurich

Universidad de Burgos

Centre National de la Recherche Scientifique

Fondation de Coopération Scientifique

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Tectonic control of sequence boundaries in rift margins: a Cretaceous example from northern Spain

Zeitschrift der Deutschen Gesellschaft für Geowissenschaften (2006)

J. García‐Mondéjar Arantza Aranburu Mikel A. López‐Horgue P.A. Fernández‐Mendiola

Sequence (biology)

Rift zone

Margin (machine learning)

10.1127/1860-1804/2006/0157-0647

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Citations (1)

Structurally controlled hydrothermal dolomites in Albian carbonates of the Asón Valley, Basque-Cantabrian Basin, northern Spain

Stefan Schroeder M.A. López-Horgue Eneko Iriarte Stefan Schröder P.A. Fernández‐Mendiola

Shallow marine carbonate sedimentation dominated during the Albian in the western part of the Basque Cantabrian Basin in Northern Spain, forming the large Ramales Carbonate Platform. This platform originated on a less subsiding tectonic block facing deeper subsiding areas to the south and east whose origin is related to intense tectonic activity due to the opening of the Bay of Biscay. The As�n valley area shows excellent outcrops of fracture-related hydrothermal dolomites hosted mainly in these Albian carbonates. Mapping in the studied area shows several dolomite bodies related to main faults that cut the platform stratification almost at right angles. The bodies show a main vertical development along fault-strike up to 900 m thick from which kilometre-scale branches expand following the stratification. Dolomitization is usually pervasive and independent of the limestone facies. Main dolomite facies are fine replacive, sucrosic and saddle. Burial analysis of the host limestone supports maximum burial temperatures of 80�C and an intense tectonic activity from Albian to Turonian with the highest subsidence interval in the latest Albian. Albian stretching of the crust and subsequent ascent of the isotherms in the area is suggested to produce sufficient heat to the dolomitizing fluids. The structural analysis indicates a strong extensional to transtensional tectonic activity in the studied area during Albian to Turonian with the creation of a overstep between W-E trending Cabu�rniga and Ruahermosa faults and N-S structures like the Ramales fault. In this scenario, fluids could have moved from subsiding deeper areas to fractured uplifted parts of the Ramales platform enhanced by diapiric activity. Petrography, C, O and Sr isotope-study and fluid inclusion analysis support a polyphase hydrothermal dolomitization at fluid-temperatures between 75�C and 240�C and highly variable salinity of up to 22wt.% NaCl. Fine dolomite replaced limestone firstly and then, sucrosic and saddle dolomites replaced part of the first dolomite and cemented newly created fracture-porosity together with different calcite cements. Zebra dolomites and hydroclastic breccias are products of this later stage.

Dolomitization

Carbonate platform

Outcrop

Fault block

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The OAE1a in Cuchía (Early Aptian, Spain): C and O geochemistry and global correlation

Acta Geologica Polonica (2015)

J. García‐Mondéjar P.A. Fernández‐Mendiola Hugh Owen

Abstract C-isotopes, TOC and O geochemical data from the lower Aptian Cuchía section in the western Basque-Cantabrian basin (BCB) allow an accurate delimitation of the OAE1a-equivalent and its geochemical Menegatti´s segments, a detailed δ 13 C carb correlation with regional and interregional sections, and a high-resolution construction of TOC and bulk-rock δ 18 O carb curves and their interpretation. The δ 13 C carb values range from -2‰ and +4‰ (VPDB). They agree with previous data from the eastern BCB sections (Aralar) confirming the ammonite age of the OAE1a in the Basque-Cantabrian basin: Deshayesites forbesi, Deshayesites deshayesi, and Deshayesites deshayesi-Dufrenoyia furcata transition Zones. Interregional δ 13 C carb correlation with pelagic (Cismon, Italy, and Mid-Pacific Mountains, DSDP Site 463) and neritic (Roquefort-La Bédoule, France) core sections, reveals a common profile of a wide negative excursion characteristic of the OAE1a. It consists of a double trough separated by a flat relative maximum, with two negative spikes in the upper trough of neritic sections. TOC absolute values range from 0.12% to 1.37%. Segments of the TOC curve with persistent low values closely correspond with descending segments of the δ 13 C carb curve, and are attributed to lesser organic productivity in the BCB. Detailed bulk-rock δ 18 O carb data (-5.71‰ to -1.05 ‰ PDB) and variation curve show two main positive O-isotope shifts and three minor positive inflections, within a general negative trend characteristic of the OAE1a. The two major positive shifts correspond to both shallowing upwards sequences and the lowermost can be related to a eustatic sea level fall. Independent interregional correlation of the O-isotope shifts with C-isotopes supports their interpretation as punctuating colder events within a general warming trend.

Aptian

Ammonite

Trough (economics)

10.1515/agp-2015-0023

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Citations (7)

Sequence Stratigraphy and Systems Tracts of a Mixed Carbonate and Siliciclastic Platform-Basin Setting: The Albian of Lunada and Soba, Northern Spain

AAPG Bulletin (1993)

J. García‐Mondéjar P.A. Fernández‐Mendiola

In the Lunada-Soba carbonate platform-basin setting (Albian of Basque-Cantabrian region, northern Spain), nine type 1 depositional sequences have been identified. Their boundaries represent times of complete exposure of the platform with accompanying karstification and fluvial erosion. Relative sea level falls of 15-50 m have been estimated from depths of erosion or from diagenetic effects on platform materials and facies analysis. During lowstands, deposits of the corresponding systems tract onlapped the platform foreslope or filled incised valleys on the platform top. These deposits comprise a variety of facies: limestone megabreccias derived from the platform margin, allodapic grainstones, hemipelagic marls, fine-grained turbiditic sandstones, basinal lutites, fine-gra ned estuarine sandstones, bank bafflestones and grainstones, fluvio-deltaic pebbly conglomerates and sandstones, and shallow-water orbitolinid grainstones. Relative sea level rises were characterized by deposition of monotonous marls in the basin, and by the growth of coral-rudist mud mounds and accumulations of skeletal grainstones and marls, sometimes with back-stepping stacking, on the platform. During highstands, hemipelagic marls and prodeltaic and talus delta lutites and sandstones dominated in the basin, whereas coral wackestones and orbitolinid grainstones, sometimes with prograding clinoforms, dominated on the platform. Transgressive surfaces have erosion or simply omission features, such as pebble lags or numerous burrows, respectively. No well-developed condensed sections exis , and they are represented by thin beds of marls rich in orbitolinids. Transgressive and highstand systems tracts are normally difficult to differentiate, both in the basin and on the platform, but in sequences with an accused wedge shape, the presence of back-stepping and prograding stacking patterns makes it easier. Four main types of sequences are documented, based on geometrical characteristics. Three of them are continuous from the platform to the basin: tabular, wedge shaped with tilted base, and wedge shaped with incised base. The fourth type (scalloped) is discontinuous from the platform to the basin. It results from the collapse of the platform margin, whose debris contributed to form the following sequence, and the unveiling of the underlying sequence at the site of collapse. Most of the sequence boundaries suggest a tectonic influence, and three of them show angular unconformities in the basin margin and/or the inner platform. These angular unconformities show major erosional vacuities at the cores of anticlines on the inner platform. They are attributed to phases of accentuated transpression in a major strike-slip tectonosedimentary environment, related to the opening of Bay of Biscay. A local curve of Albian relative sea level changes correlates, in part, with the eustatic curve of the Vail charts.

Marl

Siliciclastic

Transgressive

Carbonate platform

Sequence Stratigraphy

10.1306/bdff8be6-1718-11d7-8645000102c1865d

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Citations (38)