Cenozoic Tectonic History of the Sierra de Perija, Venezuela- Colombia, and Adjacent Basins

The four major Cenozoic tectonic phases in the Sierra de Perija and adjacent basins are the early Eocene tectonic phase, the middle Eocene Caribbean orogeny, the late Oligocene phase, and the late Miocene to present Andean orogeny. Ages of unconformities associated with particularly rapid regional uplift during these phases are early Eocene (53 m.y.), middle Eocene (45 m.y.), late Oligocene (25 m.y.), and Pliocene (3 m.y.). Northwest-southeast compression may have commenced in the Perija and the Maracaibo Basin as early as the early Eocene. By the early Eocene the Macoa-Totumo arch had begun to to form during intense alpine-type folding and thrusting to the east in Falcon and Lara. During the late Oligocene phase, the Palmar area was uplifted and the most important structural features for hydrocarbon accumulation in the Maracaibo Basin developed. The late Oligocene phase initiated a basement block tectonic style that culminated during the Pliocene in the northwest thrusting of the Santa Marta massif, Sierra de Perija, and Venezuelan Andes over the adjacent basins. The main uplift of the Sierra de Perija occurred during the late Miocene-Pliocene Andean orogeny. Right-lateral oblique-slip movement of 90-100 km on the Oca fault and the left-lateral oblique-slip movement of 100 km on the Santa Marta fault were caused by late Tertiary overthrusting in the Sierra de Perija and Santa Marta massif. The northwest-southeast shortening that uplifted the Santa Marta massif, Sierra de Perija, and Venezuelan Andes us related to Caribbean-North Andean convergence along the South Caribbean marginal fault. During the Pliocene the Panama volcanic arc collided with South America. The North Andean block became detached from the South American plate and is being wedged slowly to the north between the rapidly converging Nazca, Caribbean, and South American plates. The convergence of the three plates has produced rapid subduction at the Colombia trench (6.4±0.7cm/yr; 088°±7°), slow subduction at the South Caribbean marginal fault (1.7±0.7cm/yr; 128°±24°), and the right-lateral shear (1.0±0.2cm/yr; 235°±5°) on the Bonoco and East Andean fault systems

Particle-in-cell simulations of electron acceleration by a simple capacitative antenna in collisionless plasma

We examine the electron acceleration by a localized electrostatic potential oscillating at high frequencies by means of particle‐in‐cell (PIC) simulations, in which we apply oscillating electric fields to two neighboring simulation cells. We derive an analytic model for the direct electron heating by the externally driven antenna electric field, and we confirm that it approximates well the electron heating obtained in the simulations. In the simulations, transient waves accelerate electrons in a sheath surrounding the antenna. This increases the Larmor radii of the electrons close to the antenna, and more electrons can reach the antenna location to interact with the externally driven fields. The resulting hot electron sheath is dense enough to support strong waves that produce high‐energy sounder‐accelerated electrons (SAEs) by their nonlinear interaction with the ambient electrons. By increasing the emission amplitudes in our simulations to values that are representative for the ones of the sounder on board the OEDIPUS C (OC) satellites, we obtain electron acceleration into the energy range which is comparable to the 20 keV energies of the SAE observed by the OC mission. The emission also triggers stable electrostatic waves oscillating at frequencies close to the first harmonic of the electron cyclotron frequency. We find this to be an encouraging first step of examining SAE generation with kinetic numerical simulation codes

Five Songs by Armstrong Gibbs (1889-1960): From Nostalgia to Christian Hope and the Assurance of Heaven

During the first few decades of the twentieth century, prolific composer, teacher, and conductor, Armstrong Gibbs (1889-1960), was well-regarded for his contribution to the landscape of English art song. However, against the backdrop of Modernism and the tumult of the Second World War, his musical style was deemed “out of touch.” In a 1943 chain of correspondence with fellow songwriter Roger Quilter, Gibbs describes feeling “exceedingly sore and discouraged at neglect at the hands of the critics.” He further explains, “Just because we both write music that is intelligible & frankly tries to aim at beauty, we are considered beneath the notice of the clever young men who are wholly occupied in boosting the [newer generation].” Indeed, England’s sensibilities had changed, and its spotlight turned to a list of younger composers. Gibbs’s songs—many of them steeped in Romanticism, childlike imagination, and magic—were criticized for avoiding bleak subjects. However, the intentional wide-eyed wonder in his songs is anything but escapist. Gibbs’s ideals concerning beauty had everything to do with a lifelong progression of Christian theological thought that evolved from an orientation of Nostalgia to the hope and future of Heaven. In this vein, Gibbs’s songs—including some missing ones that I recently discovered—very much confront harsh realities such as the composer’s troubled childhood and the tragic death of his son in the Second World War. Analysis and appreciation of Gibbs’s music demand sensitivity to the following four themes: 1) Gibbs’s spoiled childhood; 2) the wars that bracketed his adulthood; 3) Nostalgia as the shaping force behind his concept of beauty; and 4) evolving Christianity as its guiding light. The first two are biographical realities. The latter two are lenses through which I assert Gibbs worked and through which scholars and performers can achieve the richest understanding of Gibbs’s songs. To that end, this DMA document includes five analyses of songs that span Gibbs’s career, woven into a biographical narrative that examines various aesthetic philosophies that undergird Armstrong Gibbs’s maturing Christian worldview. These selections are: “Ann’s Cradle Song,” “The Splendour Falls,” “Before Sleeping,” “Quiet Conscience,” and “The Oxen.

Interview with Andrew and Nettie Kellogg

An interview with Andrew and Nettie Kellogg regarding their experiences in a one-room school house.https://scholars.fhsu.edu/ors/1131/thumbnail.jp

The Sunday-School Teacher as a Conversationalist

Intense energy, coupled with wise direction, and a watchful solicitude and thoughtful tenderness, belong also to the true instructor in the Sunday-school. We would add to these, and all other excellent traits, the grand accomplishment of a good conversationalist. To achieve this will be no mean undertaking. ... Many of the grandest truths, the sweetest promises, the loftiest thoughts in all the Scriptures, have been expressed in conversation. It is a royal power, a gracious gift, a pure and lofty accomplishment, to be fitted and furnished for sweet and precious converse of the things of the kingdom.https://place.asburyseminary.edu/ecommonsatsdigitalresources/1069/thumbnail.jp

The Solar Anomalous and Magnetospheric Particle Explorer (SAMPEX) yo-yo despin and solar array deployment mechanism

The SAMPEX spacecraft, successfully launched in July 1992, carried a yo-yo despin system and deployable solar arrays. The despin and solar array mechanisms formed an integral system as the yo-yo cables held the solar array release mechanism in place. The SAMPEX design philosophy was to minimize size and weight through the use of a predominantly single string system. The design challenge was to build a system in a limited space, which was reliable with minimal redundancy. This paper covers the design and development of the SAMPEX yo-yo despin and solar array deployment mechanisms. The problems encountered during development and testing will also be discussed

Tectonic Development of Panama, Costa Rica, and the Colombian Andes: Constraints from Global Positioning System Geodetic Studies and Gravity

Global Positioning System (GPS) measurements suggest the existence of a rigid Panama- Costa Rica microplate that is moving northward relative to the stable Caribbean Plate. Northward motion of South America relative to the Caribbean plate is independently suggested by the April 1991 Costa Rica earthquake, active folding in the North Panama deformed belt, and a south-dipping Wadati-Benioff zone beneath Panama. Panama may also be continuing to collide eastward with the northern Andes. Rapid subduction is occurring at the Middle America (72mm/yr), Ecuador (70mm/yr), and Colombia (50mm/yr) trenches. The northern Andes are moving northeastward relative to stable South America. Preliminary GPS results also suggest Caribbean-North Andean convergence and an independent North Nazca plate. About 6 Ma the Panama-Choco island arc collided with the northwestern margin of South America, eventually forming a land bridge between the Americas; closed the Pacific-Caribbean seaway, changing ocean circulation patterns and perhaps the world\u27s climate; folded the East Panama deformed belt; and uplifted the Eastern Cordillera of Colombia. An interpretation of the paleo-Romeral suture in southern Colombia as a low-angle fault dipping to the west into the lower crust under the Cordillera Occidental is compatable with seismic velocity and gravity data. During the Late Cretaceous the Western Cordillera oceanic terrain was obducted eastward on the fault system over continental crust

A 3-D Gravity Tectonic Study of Ita Mai Tai Guyot: An Uncompensated Seamount in the East Mariana Basin

Ita Mai Tai is a large, locally uncompensated seamount on the eastern edge of the East Mariana Basin. A large positive gravity anomaly of 254 mgal characterizes the summit and a low of -69 mgal, the surrounding moat. Using polygonal prisms to approximate the bathymetry, the observed gravity was inverted to calculate an average density of 2.59 g/ems for the seamount. Observed-calculated gravity residuals are reduced by including the flanking sedimentary basins and a dense volcanic conduit. The drill sites from DSDP Legs 20 and 89 describe a volcanic edifice formed in the Aptian!Albian on Jmassic/Cretaceous crust. The volcanism is recorded in volcanoclastic and epiclastic deposits in the basins nearby. The guyot was covered initially by a succession of reefal and lagoonal sediments followed by a thick mantling of pelagic sediments after it subsided. Gravity models that adequately match the calculated and observed data sets for Ita Mai Tai show little crustal thickening, suggesting that Ita Mai Tai is almost completely locally uncompensated

The Extended Tracking Network and Indications of Baseline Precision and Accuracy in the North Andes

The CASA UNO Global Positioning System (GPS) experiment (January-February 1988) included an extended tracking network which covered three continents in addition to the network of scientific interest in Central and South America. The repeatability of long baselines (400-1000 km) in South America is improved by up to a factor of two in the horizontal vector baseline components by using tracking stations in the Pacific and Europe to supplement stations in North America. In every case but one, the differences between the mean solutions obtained using different tracking networks was equal to or smaller than day-to-day rms repeatabilities for the same baselines. The mean solutions obtained by using tracking stations in North America and the Pacific agreed at the 2-3 millimeter level with those using tracking stations in North America and Europe. The agreement of the extended tracking network solutions suggests that a broad distribution of tracking stations provides better geometric constraints on the satellite orbits and that solutions are not sensitive to changes in tracking network configuration when an extended network is used. A comparison of the results from the North Andes and a baseline in North America suggests that the use of a geometrically strong extended tracking network is most importanwt hen the network of interest is far from North America