Geology of the Falcón Basin (NW Venezuela)

This paper presents a geological map and cross-section of the Falcón Basin based both on published and unpublished work and on new data collected in the northern and southern basin margins. The geological map covers an area of 4600 km2 at 1:100,000 scale. The cross- section is oriented NNW-SSE, traversing perpendicular to the main structures. In general, the structure of the study area results from the inversion of a graben (Oligocene-early Miocene back-arc basin), that started in the middle Miocene due to the convergence between the Caribbean and South American plates. The map, the cross-section and the observations made in the field have been used to generate a tectonostratigraphic reconstruction of the Falcón Basin. The Oligocene-early Miocene sedimentary succession mapped and described is relevant to the hydrocarbon exploration in the Caribbean and in the Gulf of Venezuela, where new hydrocarbon resources have recently been discovered (i.e. Perla gas field)

The La Luna/Río Negro(.) Petroleum system at the Urdaneta West Field, lake Maracaibo basin, NW Venezuela: ID basin modelling and secondary oil migration

This paper investigates the timing of hydrocarbon generation in the northern part of the Urdaneta West field in the NW of the Lake Maracaibo Basin, NW Venezuela, based on ID basin modelling at three wells referred to as wells X, Y and Z. Kitchen areas were identified and secondary migration directions were inferred based on analyses of the thermal and burial history of the Upper Cretaceous La Luna Formation source rock and the geochemistry of 20 oil samples from the Río Negro Formation reservoir. Aliphatic hydrocarbons in the oil samples were analysed by gas chromatography - mass spectrometry (GC-MS) while the vanadium- nickel and sulphur contents were determined by energy dispersive X-ray spectrometry and inductively coupled plasma optical emission spectroscopy, respectively. Bulk and molecular characterizations indicated that the oils originated from a marine carbonate source rock containing oil-prone Type II kerogen, consistent with generation by the La Luna Formation. Burial and thermal history modelling in the study area indicated that the La Luna source rock at wells X, Y and Z reached the oil window during the late Eocene, mid-Eocene and early Paleocene respectively. ID model results from the three wells showed that hydrocarbon generation began in the early Eocene. The transformation ratio of the La Luna Formation source rock in the modelled wells reached values of 35%, 98% and 100% by the end of the Eocene. In the Urdaneta West field, two different oil charges appear to have mixed in the Río Negro reservoir. Both oil charges were generated by the La Luna Formation source rock but at different times. A first charge of less mature oil occurred in the middle-late Eocene (Phase 1 generation), and a second, more mature oil charge took place in the Miocene - Quaternary (Phase 2 generation). The kitchen area for the first oil charge is inferred to have been located to the north and NE of Urdaneta West; that for the second oil charge to the south of the field. This migration model is supported by observed variations in the geochemical compositions of the oil samples analysed from different wells in the Urdaneta West field.J.G. Diaz acknowledges the support of the PDVSA Western Exploration Project Management and the University of Zulia. The authors are grateful to Iván Chirino and Patricia Marín for their scientific assistance. We are also grateful to the JPG referees (Karla Quintero-Bonilla, Katya Reategui and anonymous) whose comments helped to improve the original version of this manuscript. Carlos Boente obtained a post-doctoral contract within the program PAIDI 2020 (Ref 707 DOC 01097), co-financed by the Junta de Andalucía (Andalusian Government) and the EU

A new Megatheriinae skull (Xenarthra, Tardigrada) from the pliocene of northern venezuela – Implications for a giant sloth dispersal to central and North America

A skull of a ground sloth from the Pliocene San Gregorio Formation documents a northern neotropical occurrence of a megatheriine that addresses issues on intraspecific variation and biogeography. The new specimen is broadly similar in size and morphology to that of Proeremotherium eljebe from the underlying Codore Formation in the Urumaco Sequence, differing in several features such as a longer basicranial area and a more posteriorly projected basioccipital between the condyles. The living sloths species of Bradypus and Choloepus do not have unequivocal anatomical features that indicate sexual dimorphism. Nevertheless, fossil sloths may have shown such dimorphism, and speculations on this subject are part of the considerations that can be made when allocating fragmentary fossils (e.g., in the new skull the presence of a long sagittal crest could indicate a male individual and the absence of an extended crest in Proeremotherium eljebe a female one). We speculate that as early as the late middle Miocene, two main lines of Megatheriinae had clearly separated in two geographic areas, one in the rising Andean area and one at low latitudes on the lowlands of central and northern South America.Fil: Carlini, Alfredo Armando. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Departamento Científico de Paleontología de Vertebrados; ArgentinaFil: Brandoni, Diego. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; ArgentinaFil: Sánchez, Rodolfo. Museo Paleontológico de la Alcaldia de Urumaco; VenezuelaFil: Sánchez Villagra, Marcelo R.. Universitat Zurich; Suiz

Comment on 'Tectonic and environmental factors controlling on the evolution of Oligo-Miocene shallow marine carbonate factories along a tropical SE Circum-Caribbean' by Silva-Tamayo et al. (2017)

Silva-Tamayo et al. (2017) study the Chattian to Langhian carbonate succession of the Siamana Formation in the Cocinetas Basin (La Guajira, Colombia). They identify a change in carbonate factory from mixed photozoan-heterozoan and photozoan associations dominated by corals in the Chattian-early Burdigalian to a heterozoan rhodalgal association in the late Burdigalian-Langhian. To validate the regional scale of this shift in carbonate-producing biota along the southeastern Circum-Caribbean realm, Silva-Tamayo et al. compare the Siamana Formation with the San Luis carbonate succession in the Falcón Basin (NE Venezuela) and the Perla carbonates in the Urumaco Trough (Gulf of Venezuela). Referring to Albert-Villanueva (2016) they state that, as in the case of the Siamana Formation, the carbonates of the San Luis Formation also recorded a change in carbonate-producing biota, from a photozoan/heterozoan carbonate factory in the late Oligocene-early Miocene to a heterozoan/rhodalgal carbonate factory in the middle Miocene. Notwithstanding, Albert-Villanueva (2016) interprets the carbonate units cropping out in the Falcón Basin (San Luis and Churuguara formations) as early Miocene in age, and the passage from photozoan to heterozoan carbonate factory as a lateral change of facies within the lower Miocene carbonate platforms of the Falcón Basin

TSUNAMI HAZARD IN NORTHERN VENEZUELA

Based on LANDSAT ETM and Digital Elevation Model (DEM) data derived by the Shuttle Radar Topography Mission (SRTM, 2000) of the coastal areas of Northern Venezuela were investigated in order to detect traces of earlier tsunami events. Digital image processing methods used to enhance LANDSAT ETM imageries and to produce morphometric maps (such as hillshade, slope, minimum and maximum curvature maps) based on the SRTM DEM data contribute to the detection of morphologic traces that might be related to catastrophic tsunami events. These maps combined with various geodata such as seismotectonic data in a GIS environment allow the delineation of coastal regions with potential tsunami risk. The LANDSAT ETM imageries merged with digitally processed and enhanced SRTM data clearly indicate areas that might be prone by flooding in case of catastrophic tsunami events

Sertulum Ternstroemiacearum I. Sinopsis del género Freziera (Ternstroemiaceae) en Venezuela, incluyendo una especie nueva de la Cordillera de Mérida

The genus Freziera Willd. is distributed in Venezuela along major mountain systems, including Los Andes, Coastal Cordillera, and Guayana Shield. Two out of 11 Freziera species known from Venezuela are endemic to this country and could be endangered, but their actual conservation status is unknown, being Data Deficient according to the criteria of the IUCN. In this work, a key for the Venezuelan species is provided for the first time, and Freziera polita A.L.Weitzman ex J.R. Grande, sp. nov., from Cordillera de Mérida, is described and illustrated. Diagnostic characters of the new species, which is most closely similar to F. Guaramacalana D.Santam. & Cuello, include elongated petioles, subglabrous mature leaves, and corollas (at anthesis) that are exerted less than half the length of sepals.El género Freziera Willd. se encuentra distribuido en Venezuela a lo largo de los sistemas montañosos de Los Andes, la Cordillera de la Costa y el Escudo Guayanés. Dos de las 11 especies conocidas del país son endémicas y podrían encontrarse amenazadas, pero su estado real de conservación se desconoce, correspondiendo a la categoría Datos Deficientes de acuerdo con los criterios de la UICN. En el presente trabajo se ofrece por primera vez una clave para todas las especies presentes en el país y se describe e ilustra Freziera polita A.L.Weitzman ex J.R.Grande, sp. nov., una especie restringida a la Cordillera de Mérida. Los caracteres diagnósticos de la nueva especie, la cual es muy similar a F. Guaramacalana D.Santam. & Cuello, incluyen pecíolos alargados, hojas maduras subglabras y corolas (en antesis) exertas menos de la mitad del largo de los sépalos

New records and distribution extensions of centrolenid frogs for Venezuela

We report the first record of Centrolene notostictum for Venezuela, the first records of Centrolene venezuelense and Hyalinobatrachium pallidum for Zulia state, and extend the distribution of Hyalinobatrachium tatayoi and Espadarana andina based on specimens coming from the eastern versant of the Sierra de Perijá in northwestern Venezuela. The altitudinal ranges of all species are extended, and comments and notes on natural history provided

A new Megatheriinae skull (Xenarthra, Tardigrada) from the pliocene of northern Venezuela : Implications for a giant sloth dispersal to central and North America

A skull of a ground sloth from the Pliocene San Gregorio Formation documents a northern neotropical occurrence of a megatheriine that addresses issues on intraspecific variation and biogeography. The new specimen is broadly similar in size and morphology to that of Proeremotherium eljebe from the underlying Codore Formation in the Urumaco Sequence, differing in several features such as a longer basicranial area and a more posteriorly projected basioccipital between the condyles. The living sloths species of Bradypus and Choloepus do not have unequivocal anatomical features that indicate sexual dimorphism. Nevertheless, fossil sloths may have shown such dimorphism, and speculations on this subject are part of the considerations that can be made when allocating fragmentary fossils (e.g., in the new skull the presence of a long sagittal crest could indicate a male individual and the absence of an extended crest in Proeremotherium eljebe a female one). We speculate that as early as the late middle Miocene, two main lines of Megatheriinae had clearly separated in two geographic areas, one in the rising Andean area and one at low latitudes on the lowlands of central and northern South America.Facultad de Ciencias Naturales y Muse

The Neogene tropical America fish assemblage and the paleobiogeography of the Caribbean region

This first analysis of the marine fish fossil record in the Caribbean region during the Neogene is based on comprehensive new faunal compilation lists at the generic level from basins of nine Central and South American countries during Miocene and Pliocene times. Joint ordination and classification techniques were used to analyze data comprising 236 genera and 346 species. Principal Component Analyses were used to calculate covariance and variance between localities. We identified four subprovinces, representing four different patterns. The subprovince of Venezuela shows distinct and unique features since the Neogene in the diversity of ecosystems represented. The Antillean subprovince has a western orientation and is composed of Jamaica, the Dominican Republic, and the Trinidad islands. The third subprovince combines Panama and Ecuador. It reflects the Pacific faunal influence into the proto-Caribbean and a characteristic benthopelagic fauna. The fourth subprovince is Costarican. Its nektonic fish fauna reflects the overprinting impact over the proto-Caribbean fish fauna mostly due to local paleoenvironmental changes (neritic, estuarine and deep water assemblages), whereby the overall composition of genera is largely not affected (except few lamnids, such as the giant-toothed white sharks and the wide-toothed mako shark). The results of the analyses are concordant with previous ones based on invertebrates and identified regions in need of study (e.g., Colombia, Nicaragua, Honduras, and Brazil