Southwestern Venezuela Research Articles

Description of the larva of Hypsilara (Coleoptera: Elmidae).

The mature larva of the Larainae riffle beetle genus Hypsilara Maier & Spangler, 2011 is described here for the first time, based on larvae of Hypsilara autanai Laššová, Čiampor Jr, Čiamporová-Zaťovičová, 2014. The larvae were collected with adults in the stream near the tepui Cerro Autana and Cerro Cuao (southwestern Venezuela) and associated together using DNA barcoding. Larvae of Hypsilara strongly resemble those of Phanoceroides, here we present important morphological diagnostic characters. This description complements the descriptions of the Larainae larvae in the Neotropics, as the larva of Hypsilara was the last one of the group missing so far.

Crustal structure and tectonic implications of the southernmost Merida Andes, Venezuela, from wide-angle seismic data analysis

The crustal structure of the Merida Andes in southwestern Venezuela is crucial to our understanding of both, the complex regional geodynamics of the northern part of South America, as well as the development of the hydrocarbon basins located along its flanks. Symmetric and asymmetric models of the Merida Andes have been proposed based on geological and geophysical (principally gravimetric) surveys, without counting detailed structures from wide-angle seismic. This work examines the crustal structure of the southwestern part of the Merida Andes in Venezuela using controlled seismic sources along a 500 km wide-angle seismic profile (named ANDES SUR). Forward modeling is carried out to obtain a layer-based, P-wave, crustal velocity model. An alternative velocity model is obtained by applying a first arrival tomography for the upper 20 km depth, and a joint PmP and Pn inversion for the deeper crust. Important lateral P-wave velocity variations and low-velocity zones (LVZ) are observed within the upper crust. To the northwest, these lateral velocity variations are probably related to the deformation zones of Icotea and Tarra Faults, and the southeast to the Mantecal and Apure grabens. The integration of seismological data to the profile provides some clues about a possible slow-shear movement between the upper and the lower crust (brittle-ductile transition zone) at the NW end of the profile, as well as the possible northwestward incipient subduction of the South American Plate beneath the Maracaibo Triangle Block. We interpret the Boconó Fault's main trace as a take-off surface detaching from the interface between the upper and lower crust and dipping to the SE. A slight NW displaced crustal root of the Merida Andes is observed in all models, being the root ∼150 km wide with an approximately 9 km downward deflection (from ∼46 to 55 km depth) of the Moho. The crustal structure along the profile ANDES SUR, together with the observations along two profiles located further north, provide information about the tectonic implication along the strike of the Merida Andes, favoring an asymmetric model with possible NW directed South American lower crust and upper mantle underthrusting or incipient subduction beneath the Maracaibo Triangle Block beneath the center of the Merida Andes.

Palynostratigraphy and lithostratigraphy of Upper Cretaceous and Paleogene outcrop sections, Mérida Andes (Maracaibo Basin), Western Venezuela

Detailed palynologic and lithostratigraphic studies of outcrop sections on the western flank of the Mérida Andes in Western Venezuela were undertaken to establish a framework for interpreting and correlating regional and local unconformities from the outcrop to subsurface data. The Upper Cretaceous to lower Paleogene section of the Maracaibo Basin consists of laterally continuous rock units attributed to the Mito Juan and Barco/Catatumbo formations, which are characterized by marine sediments deposited relatively close to shore. The continuity of plant and dinoflagellate species across the Cretaceous-Paleogene boundary in this area may have potential significance to K/Pg studies elsewhere. The lower to upper Paleogene Los Cuervos, Mirador, and Carbonera formations were predominantly deposited in non-marine environments, though palynologic and stratigraphic data from each unit show the variable influence of marine and lacustrine conditions. A new chronostratigraphic framework for the study area (the “Venezuelan Composite Standard”) was developed based on first and last appearances of spores, pollen, and dinoflagellates, and three pollen acme events and calibrated to the latest time scale. Graphic correlation plots of the most complete outcrop sections at Río Lobaterita, Río Lora, and Río Chama indicate the presence of significant hiatuses in time, due to erosion and non-deposition (or a combination of the two) reflecting the complex structural and depositional history of the southeastern Maracaibo Basin. A regionally significant upper Paleocene to lower Eocene unconformity, as well as several local and regional intra middle Eocene unconformities appear to have been caused by a drop in base level (sea level plus structural uplift) forming incised valleys over much of the study area. Unconformities are also present in the upper middle Eocene to Oligocene and represent ravinement surfaces caused by transgressive marine reworking of pre-existing units. These surfaces are often marked by the presence of dinoflagellates within the upper Eocene Carbonera Formation. Depositional environments during much of the Upper Cretaceous to Paleogene succession vary from fluvial-floodplain to marginal marine, with newly noted periods of widespread lacustrine deposition in all geologic units. Temporal differences between similar Paleogene lithostratigraphic units in northeastern Colombia and southwestern Venezuela are likely due to the influence and timing of structural events on regional and local depositional environments.

Geochemical and mineralogical records of late Albian oceanic anoxic event 1d (OAE-1d) in the La Grita Member (southwestern Venezuela): Implications for weathering and provenance

In this paper, stratigraphic distributions of major, trace and rare earth element (REE) concentrations as well as the bulk and clay mineralogy of organic-rich calcareous rocks of the La Grita Member (Capacho Formation) in southwestern Venezuela were studied to constrain sedimentary depositional conditions during the late Albian-early Cenomanian oceanic anoxic event 1-d (OAE-1d; 103 to 99.5 Ma). The statistically significant correlations observed between total REEs and Al, total organic carbon (TOC) and phyllosilicates suggest that REEs mainly occur in clay minerals and organic matter. Ce anomalies are mainly controlled by detrital input and cannot be used as redox proxies in this stratigraphic sequence. Detrital proxies, notably phyllosilicate/(K-feldspar + plagioclase), K-feldspar/(K-feldspar + plagioclase), and kaolinite/illite, suggest that greenhouse warming established during the OAE-1d intensified the hydrologic cycle and consequently increased continental chemical weathering rates. The Zr/Sc ratio and Al2O3–TiO2–Zr ternary diagram suggest detrital input dominated by recycling of older sedimentary rocks, while the La–Th-Sc ternary relationship indicates that most sediment samples were deposited between a passive margin and a continental island arc setting. Sedimentary discrimination diagrams (including La–Th-Sc and Co/Th vs. La/Sc), combined with chondrite-normalized REE patterns, suggest that siliciclastic sediments of the La Grita Member were mainly supplied by metasedimentary and intracratonic rocks of the Guayana Craton, notably the Roraima Formation, suggesting that this area was the main source for siliciclastic sediments during the Cretaceous. The Santander Massif and Merida and El Baúl Arches likely acted as secondary provenance areas, confirming previous work using U–Pb detrital zircon geochronology.

Paleoenvironmental changes during the late Albian oceanic anoxic event 1d: An example from the Capacho Formation, southwestern Venezuela

The late Albian–early Cenomanian oceanic anoxic event 1d (OAE-1d; ~103 to 99.5 Ma) represents a global interval of enhanced organic carbon burial due to widespread oxygen deficiency in the water column and/or increased primary productivity. The biostratigraphy and geochemistry of organic-rich sediments in the La Grita Member (Capacho Formation) in southwestern Venezuela were studied to document the paleoenvironmental conditions that governed the deposition of this succession during OAE-1d. Carbon-isotope (δ13Ccarb and δ13CCorg) chemostratigraphy and biostratigraphic constraints show that the La Grita Member spans the late Aptian period (Rotalipora appenninica Zone), and that OAE-1d is well recorded in this succession. A prominent increase in total organic carbon (TOC) values (up to 10%) is clearly recorded through the onset of OAE-1d, coinciding with a prominent change in overall redox-sensitive proxies suggesting that the La Grita Member sediments accumulated under anoxic (and possibly euxinic) bottom-water conditions in a partially restricted basin. The detrital proxies suggest that the greenhouse climate prevailing during OAE-1d induced significant acceleration of the hydrologic cycle and an increase in continental chemical weathering rates. Overall, the carbon and oxygen isotope records, TOC contents, as well as the detrital proxies show cyclic variation during the late Albian stage. These variations support the hypothesis that orbital forcing likely also modulated the equatorial monsoonal activity during the OAE-1d.

A new species of Cryptonympha Lugo-Ortiz McCafferty (Ephemeroptera, Baetidae) from Cerro Duida (Venezuela).

The genus Cryptonympha includes three species: C. copiosa Lugo-Ortiz McCafferty, 1998; C. dasilvai Salles Francischetti, 2004 and C. genevievae Thomas, Manchon Glémet, 2013, known only from the nymphal stage. A description of the nymph of a fourth representative, Cryptonympha tracheata sp. n. is provided here, based on material collected in a blackwater stream on the slopes of the Cerro Duida mountain in south-western Venezuela. The nymph of the new species can be easily distinguished from the other species of the genus by very long tracheal gills II-VII, 2.5 times the length of each tergum, gill I small, nearly half length of gill IV and by posterior margin of terga with rounded spines. A complete description of the new species and a key for nymphs of all known Cryptonympha species are provided.

Revision of the Neotropical water scavenger beetle genus Globulosis García, 2001 (Coleoptera: Hydrophilidae: Acidocerinae).

The Neotropical water scavenger beetle genus Globulosis García, 2001 is revised. Originally described from a single male specimen from southeastern Venezuela, the genus has since been found in localities across the Guiana Shield region and beyond, including Colombia, Suriname, Guyana, and Brazil. The genus is redescribed. Morphological characters and genetic data from the mitochondrial gene COI from ten populations across its range provide support for two distinct species, corresponding loosely to geography. The type species, G. hemisphericus García, is redescribed and newly recorded from Guyana, Suriname, and Brazil (Amazonas, Para). One new species is described, Globulosis flavus sp. n. from southwestern Venezuela (Amazonas, Bolivar). The genus is associated with lotic habitats, and typically found along the margins of small to medium sized streams. High-resolution habitus and aedeagal images and distribution maps for all species are provided.

Long-distance bird migration within South America revealed by light-level geolocators

Little is known about the timing of migration, migration routes, and migratory connectivity of most of the >230 species of birds that breed at south temperate latitudes of South America and then migrate toward the tropics to overwinter. We used light-level geolocators to track the migration of 3 male and 3 female Fork-tailed Flycatchers (Tyrannus savana) captured on their breeding territories in Argentina. All birds initiated fall migration between late January and late February, and migrated 45 to 66 km day-1 in a northwesterly direction through central South America to either one or two wintering areas. Five individuals first spent several weeks (in April and May) in western Amazonia (mainly Peru, northwestern Brazil, and southern Colombia) before moving east to spend the rest of the non-breeding season in central Venezuela and northern Brazil. One individual occupied primarily one wintering area in eastern Colombia, northwestern Brazil, and southwestern Venezuela. Fall migration took approximately 7–12 weeks to complete and covered a distance of 2,888–4,105 km. We did not analyze spring migration data because of broad overlap with the austral spring equinox. These results are the first data on wintering locations, migration timing, and routes of individual migrant passerine birds that breed in South America. Given the general lack of similar data for practically all migratory birds that breed in South America, geolocator technology has the potential to revolutionize our understanding of how birds migrate—and the threats they face—on South America's rapidly changing landscape.

Probabilistic facies discrimination from simultaneous seismic-inversion results in clastic reservoirs in southwestern Venezuela

Facies volumes were obtained in southwestern Venezuela reservoirs integrating rock-physics analysis and seismic-inversion results. Facies volumes showed a sandstone-shale spatial distribution that matches log data and the conceptual sedimentologic model of the reservoir. After seismic-gather conditioning, applying a simple but robust processing sequence, the signal-to-noise ratio was increased. Two angle stacks were generated to perform a simultaneous seismic inversion to obtain P- and S-wave impedance volumes. Parallel to the inversion process, rock-physics analysis was done using rock-physics templates (RPT) for constant-cement models (CCM) to discriminate between sandstone and shale. P- and S-wave impedance bivariate probabilistic density functions (PDF) were computed from well-log data as an a priori probability. Finally, these PDFs were used to classify facies from P- and S-wave impedance volumes obtained from simultaneous inversion, using a Bayesian probabilistic approach. This classification produced two facies volumes, sandstone and shale, which honored the well information and rock-physics models.

New records of Leptophis ahaetulla ahaetulla (Serpentes, Colubridae) for Venezuela, Colombia and the placement of L. a. copei into the synonymy of L. a. ahaetulla

The taxonomic validity of Leptophis ahaetulla copei is assessed. This subspecies is distinct from the nominal subspecies on the basis of differences in the number of ventral scales, maxillary teeth and dorsal coloration. However, comparison of its type specimens with specimens of L. a. ahaetulla revealed that L. a. copei is a junior synonym of the latter. In addition, the distribution of L. a. ahaetulla is expanded from Brazil to southwestern Venezuela and southern Colombia.

Estimating Permeability of Vuggy-and-Fractured Carbonates by Modeling Mud-Filtrate-Invasion Effects on Resistivity Logs

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 121136, "Modeling Mud-Filtrate-Invasion Effects on Resistivity Logs To Estimate Permeability of Vuggy-and-Fractured Carbonate Forma tions," by Luis Javier Miranda, SPE, Carlos Torres-Verdin, SPE, and Jerry Lucia, SPE, University of Texas at Austin, prepared for the 2009 SPE EUROPEC/EAGE Annual Conference and Exhibition, Amsterdam, 8-11 June. The paper has not been peer reviewed. A method was developed to diagnose and estimate secondary porosity and absolute permeability of vuggy-and-fractured carbonate formations by use of numerical simulation of mud-filtrate-invasion process. The method was used to interpret data acquired in a carbonate reservoir in the Barinas-Apure basin in southwestern Venezuela. Introduction Permeability estimation is an important step of reservoir characterization. In heterogeneous reservoirs, in which rock composition and petrophysical properties vary, integration of core measurements with well-log data is necessary to predict petrophysical properties in zones with no or scarce core samples. Permeability was estimated by numerical simulation of the mud-filtrate-invasion process that takes place in complex reservoirs having a triple-porosity system. Dual-laterolog and array-induction-resistivity logs were simulated to validate the estimation of petrophysical properties. This method includes the geological characterization of core measurements and the integration of well-log and production data. Field Description The O-BOR-2E reservoir is in the Borburata field, in the Barinas-Apure petroleum basin of southwestern Venezuela. The field, covering a total area of 14 km2, includes a group of smaller zones delimited by faults. The carbonate reservoir accounts for most of the hydrocarbon production of the field, which was discovered in 1994. It has wide variations of rock composition and petrophysical properties and, as Fig. 1 shows, comprises a triple-porosity system (i.e., matrix, vugs, and fractures), according to observations and analysis of core measurements and nonconventional well logs. Sedimentary Model Facies in the O-BOR-2E reservoir are sandstone, mixed sandstone/dolostone, dolostone, pelecypod limestone, foraminiferal limestone/siltstone, and shale. The volumetric concentration of each facies varies across the field. An important observation is that the best oil-producing wells are in zones with large amounts of dolomite that also are associated with an increase of secondary porosity (interconnected vugs and fractures). Method of Core/Log Integration Most interpretation methods to estimate permeability are based on empirical correlations between permeability and porosity, irreducible water saturation, pore-throat radius, and other factors. Integration of core and log data is necessary to estimate permeability. The large variability observed in rock composition and petrophysical properties, coupled with a high degree of spatial diversity, makes it necessary to use nonconventional interpretation methods to estimate permeability.

Seasonality and Sex Differences in Travel Distance and Resource Transport in Venezuelan Foragers

The anthropological literature generally describes forager women as less mobile than men because of their child-care responsibilities and the energetic costs of reproduction. Examination of resource transport among the savanna Pumé of southwestern Venezuela reveals, in contrast, that for certain food resources travel distances and resource weights relative to body weights are greater for women than for men. Male foraging is often associated with greater travel distances, but men frequently walk unencumbered because hunting trips may exhibit low or zero food returns and hunters usually carry only a minimum tool kit. Women, who target highly predictable foods that can be collected in large quantities, frequently carry firewood, tools, and large baskets of food for extended distances during gathering. It appears that the consistent and large returns of female foraging underwrite the large energetic effort of men's hunting.

Volatile Constituents from the Aerial Parts of Salvia angulata H.B.K. of Venezuela

The essential oil isolated by hydrodistillation from the aerial parts of Salvia angulata H.B.K., (Lamiaceae) collected from southwestern Venezuela, was analyzed by GC and GC/MS. Among the 22 identified compounds, the major components were the sesquiterpenes hydrocarbons which made up 79.8% of the oil, with β-caryophyllene (27.7%), germacrene D (19.5%) and bicyclogermacrene (18.3%) as the most abundant ones. Oxygenated sesquiterpenes made up 14.2% of the oil, while the monoterpene fraction was only 3.3%. As far as we know, this is the first report on S. angulata essential oil.

Rubiacearum Americanarum Magna Hama Pars XIX. New species of Palicourea (Psychotrieae) from Ecuador, Peru, and Venezuela

Abstract Eight new South American species of Palicourea are described and illustrated: P. crystallina from north-central Peru differs from P. loxensis from Ecuador, also described herein, by its longer calyx limbs, 1.2–2.5 mm long, with the lobes often unequal in length; P. cutucuana from southern Ecuador differs from P. angustifolia in its broader leaves and inflorescences and larger corollas; P. gelsemiiflora of northern Peru is distinguished by its pedicels 11–20 mm long, calyx limbs 7–11 mm long, relatively large yellow corollas with tubes 32–33 mm long, relatively large fruits 12–13 mm long, and pyrenes with an unusual spongy wall; P. gemmiflora of southern Ecuador and northern Peru differs from P. subtomentosa by its longer corollas with horn-like projections on the abaxial surfaces of the lobes; P. lemoniana of southwestern Venezuela differs from P. nitidella by its corolla tubes 17–18 mm long with the lobes pubescent abaxially and from P. grandiflora by its secondary leaf veins only 7–10 pairs and...

EPR stratigraphy applied to the study of two marine sedimentary sections in southwestern Venezuela

This work explores the application of the electron paramagnetic resonance (EPR) technique, a high sensitivity spectral method, as a means of characterizing stratigraphic facies and identifying depositional environments. We have studied two marine sedimentary sections, of mid-Cretaceous and mid-Eocene ages, that are located in southwestern Venezuela. The different paramagnetic species (e.g. manganese, free radicals and different forms of Fe) have been identified and their relative concentrations measured from the EPR spectra. These results were then integrated to those from petrographic and magnetic susceptibility analyses (room and high temperature) as well as to some other rock magnetic data such as Q n and S-ratios. Because Mn 2+ content seems to be finely tuned to variations of redox conditions, it could serve as a sensitive index of paleoenvironmental changes in stratigraphic columns with large lithological contrasts. Conversely, the presence and concentration of distinct Fe species proves to be quite useful characterizing different depositional environments at those stratigraphic sections that exhibit similar lithologies throughout. The integration of EPR results with rock magnetic data allows the identification of diagenetic events that could have taken place after sediment deposition.

Palinología e icnología en la determinación del contacto discordante Cretácico-Terciario en Venezuela suroccidental y su impacto en la exploración por hidrocarburos

Palynology and ichnology in the determination of Cretaceous-Tertiary unconformity contact in southwestern Venezuela and their impact in hidrocarbons exploration. Palynological results from the southwest of Venezuela are given. The material comes from two wells drilled in Barinas state. Integration of results from analyses of marine and terrestrial palynomorphs, and ichnofacies, allows to determine the Maastrichtian-middle Eocene unconformity in well #1 at 9901´5´´ by the presence of Foveotriletes margaritae (Van der Hammen) Germeraad, Hopping & Muller, peridinioid dinocysts and the Glossifungites ichnofacies. In well # 2, the unconformity was established by the presence of F. margaritae, Ariadnaesporites Potonie and Buttinia andreevi Boltenhagen at 10154´6´´.

Geochemistry of the Mirador Formation (Late Eocene-Early Oligocene), southwestern Venezuela: Chemostratigraphic constraints on provenance and the influence of the sea level

A geochemical study was carried out on Eocene-Lower Oligocene sedimentary rocks (the Mirador Formation) from the southern Lake Maracaibo Basin, western Venezuela. The goal of this work was the identification of source rock composition and tectonic settings of source areas, and their temporal changes. The geochemistry was also used to investigate attributes of the paleoenvironment. Eighty-nine rock samples were collected and the bulk inorganic geochemistry (Al2O3, SiO2, TiO2, Fe2O3, MnO, CaO, MgO, K2O, Li, B, Sc, V, Cr, Ni, Zn, Rb, Y, Mo, La, Ce and Th) was determined by ICP-AES; total sulfur was determined in a LECO SC-432 analyzer. Multivariate statistical tools were employed to evaluate the correlation between the different variables. Through cluster-constrained analysis, four subdivisions, or main chemofacies, were defined and correlated with the significant lithologic units. The tectonic setting for the source rock could be a passive margin, and a mixed source was inferred, consisting of recycled sedimentary rocks and igneous and/or meta-igneous rocks of predominantly felsic composition. The most marine-influenced lithological units occur at the bottom of the section.

Magnetic and mineralogical studies to characterize oil reservoirs in Venezuela

High-resolution aeromagnetic surveys over oil fields and magnetic susceptibility (MS) measurements in soils, sediments, and drill cuttings have been proposed as complementary or alternative means of exploration and assessment of hydrocarbon reservoirs. Some micromagnetic anomalies detected by these studies could be the likely result of the existence, at shallow depths, of authigenic magnetite and/or Fe-sulphides. It has been hypothesized that such magnetic minerals are the chemical byproducts of primary Fe-oxides exposed to a reducing environment induced by the underlying reservoir. Secondary magnetite could appear as spherical aggregates (framboids) of submicronic crystals identifiable by scanning electron microscopy (SEM). The formation of these framboids seems linked either to inorganic chemical processes associated with the presence of hydrocarbons or to oil biodegradation. In the last few years, we have examined the causal relationship between framboids of magnetic minerals and hydrocarbons via rock magnetic and electron paramagnetic resonance (EPR) analyses of drill cuttings. The samples used have been taken at different depths (within the first 1500 m) of producing and nonproducing wells from two oil fields in southwestern Venezuela. We have complemented MS results with S-ratio logs, SEM, X-ray energy dispersion (EDX), IRM acquisition curves, and high-temperature susceptibility measurements. More recently we have also studied soil samples from an oil prospective area in western Venezuela, where rock magnetic and EPR results were compared with ethane gas analyses and remote sensing data. Rock magnetic and EPR studies have been performed in 14 oil wells from La Victoria (3) and Guafita (11) fields (Figure 1). Since our research has focused at the near-surface expression of hydrocarbon migration, the samples analyzed (drill cuttings) were taken from different depth at intervals of about 15 m between 100 and 1500 m. All samples belong to a single group of molasses from strata that lie far above the producing levels …

Azimuthal offset‐dependent attributes applied to fracture detection in a carbonate reservoir

Offset‐dependent attributes—amplitude versus offset (AVO) and frequency versus offset—are extracted from 2‐D P‐wave seismic data using the multiple signal classification technique. These attributes are used to detect fracture orientation in a carbonate reservoir located in the Maporal field in the Barinas basin of southwestern Venezuela. In the fracture normal direction, P‐wave reflectivity is characterized by a large increase of amplitude with offset (large positive AVO gradient) and a large decrease of frequency with offset (large negative frequency versus offset gradient). In the fracture strike direction, P‐wave reflectivity shows a scattered variation in AVO but a small variation in frequency with offset. Our results also show that the reservoir heterogeneity can lead to large variations of AVO signatures and that using azimuthal offset‐dependent frequency attributes can help lessen the ambiguity when detecting fracture orientation.

GEOPHYSICS: This issue of GeophysicsThis issue of Geophysics

Grech et al. use the first arrivals from a multi-offset VSP to determine the anisotropy parameters by traveltime inversion. The authors demonstrate the application of these parameters during anisotropic PSDM for enhanced depth imaging. Shen et al. introduce a technique to AVO and FVO attribute estimation in the frequency domain and demonstrate the application of these attributes to the detection of fracture orientation in a carbonate reservoir in the Maporal field of southwestern Venezuela. They also show that reservoir heterogeneity has an important effect on AVO signatures and should be considered in fractured reservoir characterization. Slater and Reeve propose that electrical geophysics methods are excellent tools for the investigation of the stratigraphy and hydrogeology of peatland systems and the related controls on vegetation communities observed at the surface. Whereas GPR and IP imaging are appropriate for determining peat and underlying lake sediment thickness, resistivity imaging is valuable for investigating the mineral basement, which exerts a strong control on peatland hydrogeology. Soroka et al. demonstrate how 3-D AVO can be an effective tool for identifying potential missed reserves in old producing fields. The advantages of 3-D over 2-D AVO are discussed. Valuable acquisition and processing lessons learned in this early onshore 3-D AVO project are presented for future reference. Berryman et al. present a new synthesis based on ideas of Gassman and Biot that uses compressional and shear wave velocities in a scheme that is much simpler to understand and apply, yet yields detailed information about porosity and fluid saturation magnitudes and spatial distribution. The density and the Lame elastic parameter λ are the two parameters determined from seismic velocities that also contain information about fluid saturation, and this observation leads to concepts for two types of λ -diagrams for evaluating partial and patchy saturation in reservoirs. Prasad shows how P …