Agustín Martín-Algarra

A 21 ± 2 Ma age for the termination of the ductile alpine deformation in the internal zone of the betic cordilleras, South Spain

Abstract Rb-Sr dating of WR-muscovite pairs from two mica schists and two gneisses from the Velez-Malaga-Torrox area, 40 km E of Malaga, gives tie lines indicating ages of 23.4 ± 2.7, 19.3 ± 2.2, 19.5 ± 0.7 and 22.4 ± 0.7 Ma, respectively. Geological evaluation suggests that these analytical ages indicate an age of 21 ± 2 (2σ) Ma for the metamorphic culmination connected with the latest phase of ductile deformation in the area. This Early Miocene (Aquitanian) age compares well with published radiometric ages for major orogenic processes in the westernmost Mediterranean and it is suggested that a significant part of the Alpine orogeny in the region took place in the restricted period of 19–23 Ma ago. Uplift rates in the order of 3–5 km/Ma are tentatively suggested.

Sedimentary patterns in perched spring travertines near Granada (Spain) as indicators of the paleohydrological and paleoclimatological evolution of a karst massif

Perched spring travertines of the Granada basin (South Spain) constitute a perched system with four well-defined steps, which are formed by several facies associations deposited in different sub-environments (travertine pools, dams and cascades). These perched travertines are considered as a freshwater reef system with a facies zonation and stratigraphic architecture closely resembling that of marine reef terraces and prograding carbonate platforms. The travertine deposits have been dated by 230 Th/ 234 U and 14 C methods. As in other Mediterranean areas, the travertine deposition occurred episodically during warm and wet interglacial periods coinciding with isotopic stages 9, 7 and 5, and with the transition between isotopic stages 2/1. During these periods, underground dissolution, large outflow in the springs and subsequent calcium carbonate precipitation occurred. In the same way that evolution of reef systems indicates sea level changes, the geomorphology, age and architecture of perched spring travertine systems may be used to interpret former climatically controlled changes in outflow, in base level marked by the altitude of springs and in the chemistry of spring waters. Thus, aggradation or climbing progradation may indicate an increase of outflow at the spring, progradation with toplap is due to a stable base level and, conversely, dowlapping progradation may signify that the base level was gradually dropping. Therefore, the travertines can be considered semiquantitative indicators of the paleohydrological evolution of karstic massifs and used as an important terrestrial proxy climate record. D 2003 Elsevier Science B.V. All rights reserved.

Compositional and Geochemical Signatures for the Sedimentary Evolution of the Middle Triassic-Lower Jurassic Continental Redbeds from Western-Central Mediterranean Alpine Chains

Compositional and chemical analyses suggest that Middle Triassic–Lower Liassic continental redbeds (in the internal domains of the Betic, Maghrebian, and Apenninic chains) can be considered a regional lithosome marking the Triassic-Jurassic rift-valley stage of Tethyan rifting, which led to the Pangaea breakup and subsequent development of a mosaic of plates and microplates. Sandstones are quartzose to quartzolithic and represent a provenance of continental block and recycled orogen, made up mainly of Paleozoic metasedimentary rocks similar to those underlying the redbeds. Mudrocks display K enrichments; intense paleoweathering under a hot, episodically humid climate with a prolonged dry season; and sediment recycling. Redbeds experienced temperatures in the range of 100°–160°C and lithostatic/tectonic loading of more than 4 km. These redbeds represent an important stratigraphic signature to reconstruct a continental block (Mesomediterranean Microplate) that separated different realms of the western Tethys from Middle-Late Jurassic to Miocene, when it was completely involved in Alpine orogenesis.

Carbonate and Phosphate Precipitation by Chromohalobacter marismortui

The ability of Chromohalobacter marismortui to precipitate carbonate and phosphate minerals has been demonstrated for the first time. Mineral precipitation in both solid and liquid media at different salts concentrations and different magnesium/calcium ratios occurred whereas crystal formation was not observed in the control. The precipitated minerals were studied by X-ray diffraction, scanning electron microscopy and EDX, and were different in liquid and solid media. In liquid media aragonite, struvite, vaterite and monohydrocalcite were precipitated forming crystals and bioliths. Bioliths accreted preferentially close to organic pellicles, whereas struvite preferentially grows in microenvironments free of such pellicles. Magnesian calcite, calcian-magnesian kutnahorite, “proto-dolomite” and huntite were formed in solid media. The Mg content of the magnesian calcite and of Ca-Mg kutnahorite also varied depending on the salt concentration of the culture media. This is the first report on bacterial precipitation of Ca-Mg kutnahorite and huntite in laboratory cultures. The results of this research show the active role played by C. marismortui in mineral precipitation, and allow us to compare them with those obtained previously using other taxonomic groups of moderately halophilic bacteria.

A Lost Realm in the Internal Domains of the Betic‐Rif Orogen (Spain and Morocco): Evidence from Conglomerates and Consequences for Alpine Geodynamic Evolution

The Malaguide‐Ghomaride Complex is capped by Upper Oligocene–Aquitanian clastic deposits postdating early Alpine orogenesis but predating the main tectonic‐metamorphic evolution, end of nappe emplacement, unroofing, and exhumation of the metamorphic units of the Betic‐Rif Orogen. Two conglomerate intervals within these deposits are characterized by clasts of sedimentary, epimetamorphic, and mafic volcanic rocks derived from Malaguide‐Ghomaride units and by clasts of acidic magmatic and orthogneissic rocks of unknown provenance, here studied. Magmatic rocks originated from late‐Variscan two‐mica cordierite‐bearing granitoids and, subordinately, from aplitic dikes. Orthogneisses derive from similar plutonic rocks but are affected by an Alpine metamorphic overprint evolving from greenschist ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

Variscan Tectonics in the Malaguide Complex (Betic Cordillera, Southern Spain): Stratigraphic and Structural Alpine versus Pre‐Alpine Constraints from the Ardales Area (Province of Malaga). I. Stratigraphy

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‘Verrucano’ and ‘Pseudoverrucano’ in the Central-Western Mediterranean Alpine Chains: palaeogeographical evolution and geodynamic significance

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