Estilo de deformación tectónica de las molasas miocenas dentro de la deflexión de Barcelona, entre los ríos Querecual y Aragua, estado Anzoátegui.

En la región nor-oriental de Venezuela, dentro de la Deflexión de Barcelona, afloran secuencias plurikilométricas de sedimenititas molásicas marinas de edad Mioceno inferior y medio. Estas sedimentitas formaron pliegues cilíndricos dekakilométricos en tiempos del Mioceno medio tardío, donde la falla transcurrente dextral de Urica, formó el límite entre los bloques transpresionales (Serrania del Interior) y transtensionales. El rápido levantamiento de la Serranía del Interior Oriental cambió la falla de Urica en una inversa de ángulo alto; la función transcurrente quedó transferida a la falla de Santa Inés, paralela a la anterior bacia el suroeste, durante el Mioceno tardío a Plioceno. La deflexión fue la respuesta transtensional a la compresión transpresional de la serranía en levantamiento. Abstract In north-eastern Venezuela, the Barcelona Deflexion exposes Lower and Middle Miocene molassic sediments of plurikilometric thickness. These sediments developed decakilometric cylindric folds in late Middle Miocene times, where the Urica strike-slip fault constituted the boundary between the transpressional and transtensional blocks. The rapid uplift of Serrania del Interior Oriental reversed the Urica fault, with the strike-slip activity developing a parallel fault, the Santa Ines evolving to the Deflexion during late Miocene to Pliocene times. The Deflexion thus was the transtensional response to the transpressional compression of the mountain range

A Miocene molluscan faunule from Caucagua (Miranda State, Venezuela), with the description of a new species of Tryonia (Mollusca, Gastropoda)

A molluscan faunule from the Miocene Cumaca Formation of the western margin of the Tuy Basin (Venezuela) is described. The fauna yields two species of freshwater snails and a single terrestrial snail species. Tryonia vivasi nov. spec. is described from the fauna, and its biogeographical significance is discussed

Birth and death of the Late Cretaceous "La Luna Sea", and origin of the Tres Esquinas phosphorites

Deposition of organic carbon-rich intervals of the La Luna and Navay formations of northwestern Venezuela was governed by the development of key paleobathymetric barriers (Santa Marta and Santander massifs, Paraguana Block, and ancestral Mérida Andes). These enhanced the development of anoxia in the “La Luna Sea” by causing poor circulation and limited ventilation. Anoxia was also promoted by high evaporation and low precipitation rates (high salinity bottom water), and high levels of marine algal productivity (high organic matter flux). Nutrient supply was augmented by infrequent fluvial sources. Bottom water oxygen levels increased from the Late Santonian through the end of the Cretaceous. Ventilation of anoxic bottom waters may have been enhanced by more frequent or intense seasonal upwelling (caused by higher wind stress) and catastrophic overturn, as well as the removal of a key paleobathymetric barrier. Common byproducts of overturn events were massive phytoplankton blooms, which produced red tides. Fish and marine reptile bone beds within the Tres Esquinas Member (La Luna Formation) are attributed to massive mortality during these events, and are correlative with similar Campanian units in eastern Colombia. During the Maastrichtian, increasing ventilation, combined with siliciclastic dilution, ultimately produced sediments with lower total organic carbon (TOC) content