Provenance of the Upper Cretaceous to upper Eocene clastic sediments of the Western Cordillera of Ecuador: Geodynamic implications

The Late Cretaceous–Eocene clastic deposits of the Western Cordillera of Ecuador record significant changes in the source areas, grain size, and location of the depocenters, related to the accretion of oceanic terranes that constitute the present-day Western Cordillera and Coast. Major changes in the source areas occurred in the ?late Maastrichtian and ?late middle Eocene. They are interpreted as corresponding to the accretion of the Guaranda and Macuchi oceanic terranes, respectively. Major increases in the grain sizes occurred in the ?late Maastrichtian, late Paleocene(?), and ?late middle Eocene, and seem to coincide with the accretion of the Guaranda, Piñón, and Macuchi terranes, respectively. The increasing occurrence of plutonic or metamorphic fragments and the westward shift of the depositional areas through the Paleocene–upper Eocene interval indicate an increasing uplift and erosion of the Cordillera Real. Continuous, although jerky, uplift of the latter during the Maastrichtian–Eocene period, supports the idea that the accreted oceanic material contributed to the crustal thickening and relief creation of the Ecuadorian Andes.     

Land Use Diversification in the Elite Residential Sector of Quito,Ecuador*

It is generally assumed that older mansions in the elite residential sector of Latin American cities filter down to the middle classes once their residents migrate to modern suburban homes. Five land use maps compiled between 1975 and 1999 show that the elite residential sector of Quito (Mariscal Sucre) experienced a much more complex fate. Diffusion of nonresidential land uses from the city center and its associated spine transformed the residential neighborhood into a vibrant upper‐scale business district. Sophisticated businesses subsequently moved on to modern suburban facilities, but Mariscal Sucre became a major hub for business, nocturnal entertainment, and tourism. Diversification of land use in Mariscal Sucre confirms the Crowley hypothesis of complexity in Latin American urban land use patterns ( Crowley 1995 ).     

A Pliocene–Quaternary compressional basin in the Interandean Depression, Central Ecuador

The segment of the Interandean Depression of Ecuador between Ambato and Quito is characterized by an uppermost Pliocene–Quaternary basin, which is located between two N-S trending reverse basement faults: the Victoria Fault to the west, and the Pisayambo Fault to the east. The clear evidence of E-W shortening for the early Pleistocene (between 1.85 and 1.21 Ma) favours a compressional basin interpretation. The morphology (river deviations, landslides, folded and flexure structures) demonstrates continuous shortening during the late Quaternary. The late Pliocene-Quaternary shortening reached 3400 ± 600 m with a rate of 1.4 ± 0.3 mm yr⁻¹. The E-W shortening is kinematically consistent with the current right-lateral reverse motion along the NE-SW trending Pallatanga Fault. The Quito-Ambato zone appears to act as a N-S restraining bend in a system of large right-lateral strike-slip faults. The compressive deformation which affects the Interandean Depression during the Pliocene is apparently coeval to the beginning subduction of very young oceanic lithosphere north of the Gulf of Guayaquil. The relatively buoyant new crust may have significantly increased the mechanical coupling in the subduction zone from Pliocene to Present.     

Sovereignty and subterranean resources: An institutional ethnography of Repsol’s corporate social responsibility programs in Ecuador

State mandated corporate social responsibility (CSR) programs emerged in Ecuador in the 1990s, following indigenous protests rooted in social and environmental impacts of oil extraction. CSR programs aim to deflect blame for a company’s operations, by providing development or infrastructural improvements in indigenous communities, including micro-credit projects, potable water systems, and electricity. Through an institutional ethnography of CSR programs of the Spanish owned multinational oil company, Repsol, I explore how companies intervene in transformations of social life challenging the roles of the state in securing its territorial sovereignty linked to subterranean oil resources. Drawing on interviews, participant observation, and textual analysis of company and state documents, my analysis demonstrates how CSR programs allow companies to secure their presence in the region, even in the face of shifting regimes of governance. In this article, I provide more insight into Ecuador’s transition from neoliberal to post-neoliberal eras, by calling attention to social processes that seek to legitimize expansion of corporate capital in spaces of sovereignty. If state control over subterranean resources is still crucial to understanding forms of sovereignty, then the extension of that control via CSR programs represents new relationships of power that construct the company as an expert in the region. Exploring the everyday processes of these legal relationships of sovereignty through an institutional ethnography of CSR programs uncovers the programs’ impacts and effects that seek to consolidate power in the company, undermine indigenous rights, and discipline the state.     

Daily monitoring of Ecuadorian volcanic degassing from space

We present daily measurements of sulfur dioxide (SO₂) emissions from active volcanoes in Ecuador and southern Colombia between September 2004 and September 2006, derived from the Ozone Monitoring Instrument (OMI) on NASA's EOS/Aura satellite. OMI is an ultraviolet/visible spectrometer with an unprecedented combination of spatial and spectral resolution, and global coverage, that permits daily measurements of passive volcanic degassing from space. We use non-interactive processing methods to automatically extract daily SO₂ burdens and information on SO₂ sources from the OMI datastream. Maps of monthly average SO₂ vertical columns retrieved by OMI over Ecuador and S. Colombia are also used to illustrate variations in regional SO₂ loading and to pinpoint sources. The dense concentration of active volcanoes in Ecuador provides a stringent test of OMI's ability to distinguish SO₂ from multiple emitting sources. Our analysis reveals that Tungurahua, Reventador and Galeras were responsible for the bulk of the SO₂ emissions in the region in the timeframe of our study, with no significant SO₂ discharge detected from Sangay. At Galeras and Reventador, we conclude that OMI can detect variations in SO₂ release related to cycles of conduit sealing and degassing, which are a critical factor in hazard assessment. The OMI SO₂ data for Reventador are the most extensive sequence of degassing measurements available for this remote volcano, which dominated regional SO₂ production in June–August 2005. At Tungurahua, the OMI measurements span the waning stage of one eruptive cycle and the beginning of another, and we observe increasing SO₂ burdens in the months prior to explosive eruptions of the volcano in July and August 2006. Cumulative SO₂ loadings measured by OMI yield a total of ~ 1.16 Tg SO₂ emitted by volcanoes on mainland Ecuador/S. Colombia between September 2004 and September 2006; as much as 95% of this SO₂ may originate from non-eruptive degassing. Approximate apportionment of the total SO₂ loading indicates that ~ 40% originated from Tungurahua, with ~ 30% supplied by both Reventador and Galeras. These measurements of volcanic SO₂ degassing in Ecuador confirm OMI's potential as an effective, economical and risk-free tool for daily monitoring of SO₂ emissions from hazardous volcanoes.     

Reventador Volcano 2005: Eruptive activity inferred from seismo-acoustic observation

Reventador Volcano entered an eruptive phase in 2005 which included a wide variety of seismic and infrasonic activity. These are described and illustrated: volcano-tectonic, harmonic tremor, drumbeats, chugging and spasmodic tremor, long period and very long period events. The recording of this simultaneous activity on an array of three broadband, seismo-acoustic instruments provides detailed information of the state of the conduit and vent during this phase of volcanic eruption. Quasi-periodic tremor at Reventador is similar to that observed at other volcanoes and may be used as an indicator of vent aperture. Variations in the vibration modes of the volcano, frequency fluctuations and rapid temporal fluctuations suggest the influx of new material, choking of the vent and possible modification of the conduit geometry during explosions and effusion over a period of six weeks.     

Volcanic impediments in the progressive development of pre-Columbian civilizations in the Ecuadorian Andes

Archaeological investigations in Ecuador have proposed that there appear to be hiatus or anomalous jumps in the progressive development of pre-Columbian indigenous cultures, based upon the fact that their ceramics and tools demonstrate abrupt advances in their sophistication at several horizons in the soil profile. Because some of these horizons are clearly associated with volcanic ash layers, archaeologists have sought a causal relation with volcanism, that is, the eruptive events or their products severely interfered with the early inhabitants, resulting in their abandonment of certain areas.     

Diffuse CO2 emission rate from Pululahua and the lake-filled Cuicocha calderas,Ecuador

We report herein the first results of two soil CO₂ efflux surveys carried out at Cuicocha lake-filled and Pululahua caldera volcanic systems, Ecuador. A total of 172 and 217 soil CO₂ efflux measurements were taken at the surface environment of Pululahua and Cuicocha calderas respectively, by means of the “accumulation chamber” method during the summer of 2006 to constrain the total CO₂ output from the studied area. Soil CO₂ efflux values ranged from non-detectable up to 48.5 and 141.7 g m^{− 2} d^{− 1} for Cuicocha and Pululahua calderas respectively. In addition, probability graphs were used to distinguish the existence of different geochemical populations. Sequential Gaussian Simulation was used to construct an average map for 100 simulations and to compute the total CO₂ emission at each studied area: 106 and 270 t d^{− 1} (metric tons per day) for Cuicocha (13.3 km²) and Pululahua (27.6 km²) volcanoes respectively.     

Late Pleistocene and Holocene activity of the Atacazo–Ninahuilca Volcanic Complex (Ecuador)

The Atacazo–Ninahuilca Volcanic Complex (ANVC) is located in the Western Cordillera of Ecuador, 10 km southwest of Quito. At least six periods of Pleistocene to Holocene activity (N1 to N6) have been preserved in the geologic record as tephra fallouts and pyroclastic flow deposits. New field data, including petrographic and whole-rock geochemical analyses of over forty soil and tephra sections, 100 pumice and lithic samples, and 10 new ¹⁴C ages allow us to constrain: (1) the tephra fall isopachs and detailed characteristics of the last two events (N5–N6) including volume estimates of the tephra and pyroclastic flow deposits and the corresponding volcanic explosivity index (VEI); (2) the petrographical and geochemical correlations between domes, tephras, and pyroclastic flow deposits; and, (3) the timing of the last 4 eruptive events and a period of quiescence that endured a few thousand years (1000–4000).