ABSTRACT:The Sarapiquí Miocene Arc (22.2-11.4 Ma) is located in northern Costa Rica, Central America. The regional basement is represented by serpentinized peridotites, Albian siliceous pelagites and Paleocene to Middle Eocene turbidites. The units from this arc vary from olivine-bearing basalts to rhyolites, including lavas, pyroclastic deposits and lesser subvolcanic bodies. Based on geological mapping, K/Ar dating and geochemical analysis data the magmatic evolution of the Sarapiquí Arc is established in this paper: 1) Jardín Basalts (22.2 Ma) show a near primary tendency with high MgO, TiO 2 , Ni, Cr, and Nb, high initial La/Yb ratios, and low Ba/La. 2) The Arrepentidos Basaltic-andesites, Chaparrón Pyroclasts, Hito Sar Basalts, Boca Tapada Gabbro, and Chamorro Andesites (17.2-11.4 Ma). 3). Contemporaneous felsic magmas, produced by remelting of preexisting intrusives, originated the Crucitas rhyolites, characterizated by very high Ba/La ratios and REE patterns that indicate a plagioclase rich, amphibole-bearing source. The Zr/Nb ratios (7-36) show the coalition of a minor OIB source with a dominant MORB source, both modificated by subduction. An inverse model of the source using the REE of the mafic units, show that the mantle composition was a garnet peridotite. U/Th ratios <1, indicate that the mantle metasomatism was produced by subduction of carbonate pelagic sediments. Except the lowdegree melts included in the Jardín Basalts, the rest of the units show LILE and Pb enrichments and HFSE depletions, typical of the island arc environment. Key words: Island arc, Sarapiquí arc, Miocene, geochemistry, magmatism. RESUMEN:El Arco de Sarapiquí se localiza en el sector norte de Costa Rica. El basamento de esta región corresponde con peridotitas sepentinizadas, pelagitas silíceas del Albiano y turbiditas del Paleoceno-Eoceno Medio. Las unidades que forman este segmento del arco magmático del Mioceno (22,2-11,4 Ma) varían de basaltos olivínicos a riolitas, representadas por facies lávicas, depósitos piroclásticos y en menor proporción cuerpos subvolcánicos. Con base en el mapeo geológico, dataciones K/Ar y los análisis químicos se logró establecer la siguiente evolución magmática del Arco de Sarapiquí: 1) Los Basaltos Jardín (22,2 Ma) presentan una tendencia primaria con altos contenidos de MgO, TiO 2 , Ni, Cr y Nb; altas razones La/Yb y bajas razones Ba/La. 2) Posteriormente se originó un proceso de evolución del arco magmático (17,2-11,4 Ma), representado por los

A number of side effects have been linked to the use of hormonal contraceptives, among others, alterations in glucose levels. Hence, the objective of this mini-review is to show the main effects of hormonal contraceptive intake on glycemic regulation. First, the most relevant studies on this topic are described, then the mechanisms that might be accountable for this glycemic regulation impairment as exerted by hormonal contraceptives are discussed. Finally, we briefly discuss the ethical responsibility of health professionals to inform about the potential risks on glycemic homeostasis regarding hormonal contraceptive intake.

En la cordillera de Talamanca los productos del magmatismo se encuentran ampliamente distribuidos, y corresponden con episodios intrusivos y extrusivos del Neógeno y del Cuaternario. En general es posible reconocer tres fases magmáticas: 1) Vulcanismo anterior al Mioceno Superior, de unos 17 a 11 millones de años atrás; 2) Plutonismo durante el Mioceno Medio-Superior, entre 12,5 y 7,5 millones de años, conocido como Grupo Intrusivo de Talamanca o Granito-Gabro de Talamanca; 3) Pulsos magmáticos post-intrusivos del Neógeno al Cuaternario, cuyo rango temporal se extiende entre 5 y 2 millones de años. Por primera vez se propone una diferenciación del magmatismo post-intrusivo en tres unidades, separables por aspectos petrográficos: a) Unidad Kámuk, constituida por andesitas con plagioclasa de tipo labradorita y ocasionalmente con ortopiroxeno; b) Unidad Dúrika, definida por plagioclasa de tipo andesina y biotita como fenocristal ferromagnesiano predominante; c) Unidad Río Lori, cuyos productos no fueron recolectados, pero con base en trabajos previos se caracteriza por la presencia de cuarzo, anfíbol y biotita. Se realiza además una contribución a la cartografía geológica de la cordillera de Talamanca, con una descripción geológica de las cimas de Cuericí, Ena, Dúrika, Utyum, Kámuk, fila Pittier y Echandi. También se presentan nuevos datos sobre la geología del cerro Chirripó.

Freshwater turtles (Pseudemys scripta elegans) were exposed to 0.5-13 h of anoxia at 25 degrees C, whereupon the brain concentrations of 14 amino acid and monoamine neurotransmitters and related substances were measured. Monoamines are of particular interest, because their synthesis and (in part) degradation require molecular oxygen. During anoxia, the level of the inhibitory transmitter gamma-aminobutyric acid (GABA) increased (2.3-fold after 13 h) and the level of the excitatory transmitter Glu fell. Furthermore, anoxia caused increases in the levels of Ala (14 times after 13 h), Tau, Gly, and Ser, whereas the Gln level fell. The increase in Ala is likely to inhibit pyruvate kinase, thereby mediating the decreased rate of glycolysis seen after prolonged anoxia. The increased level of Tau might protect the turtle brain against Ca2(+)-mediated anoxic damage. The monoamine metabolites almost vanished within a few hours of anoxia, indicating a halt in monoamine synthesis and breakdown, and the dopamine level fell. Nevertheless, serotonin, norepinephrine, and epinephrine levels were maintained during 13 h of anoxia, at levels extremely high compared with mammals, suggesting adaptive mechanisms such as stockpiling. It is hypothesized that the pattern of change in levels of amino acids (notably GABA and Glu) and monoamines is of functional significance, because it promotes the decrease in brain activity and energy consumption seen in anoxic turtles.

The Talamanca Cordillera in the Central America Arc (Costa Rica‐Panama) preserves the record of the geochemical evolution from an intraoceanic arc to a juvenile continental arc in an active subduction zone, making it a testbed to explore processes that resulted in juvenile continental crust formation and explore potential mechanisms of early continental crust generation. Here we present a comprehensive set of geochronological, geochemical, and petrological data from the Talamanca Cordillera that tracks the key turning point (12–8 Ma) from the evolution of an oceanic arc depleted in incompatible elements to a juvenile continent. Most plutonic rocks from this transition and postintrusive rocks share striking similarities with average upper continental crust and Archean tonalite, trondhjemite, and granodiorite. We complement these data with seismic studies across the arc. Seismic velocities within the Caribbean Plate (basement of the arc) show a relatively uniform lateral structure consistent with a thick mafic large igneous province. Comparisons of seismic velocity profiles in the middle and lower crust beneath the active arc and remnant Miocene arc suggest a transition toward more felsic compositions as the volcanic center migrated toward the location of the modern arc. Seismic velocities along the modern arc in Costa Rica compared with other active arcs and average continental crust suggest an intermediate composition beneath the active arc in Costa Rica closer to average crust. Our geochemical modeling and radiogenic isotopes systematics suggest that input components from melting of the subducting Galapagos hotspot tracks are required for this compositional change.