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Notas sobre la geología del área de Hermosillo, Sonora
... En los alrededores de la ciudad de Hermosillo, aflora una secuencia carbonatada atribuida al Carbonífero y el Pérmico que representan facies de plataforma (Peiffer, 1978), sus mejores exposiciones son en los cerros, El Molinito, Santa Gertrudis, La Morena, Tecoripita, Sierra Los Leyva, La Campana y La Cementera (González Sandoval, 2005). La secuencia paleozoica está intrusionada por el granitoide de Hermosillo de 64.1 Ma (Damon et al., 1983) y por diques máficos lamprofídicos de 21 a 25 Ma (Orozco Garza et al., 2013), la secuencia fue afectada por un proceso de metamorfismo generando corneanas con fenocristales de vesubianita (Rodríguez Castañeda, 1981). Existen escasos estudios enfocados en caracterizar el metamorfismo de contacto de Hermosillo y sus alrededores, al momento solo se han realizado estudios para caracterizar la mineralización del skarn de W de El Paloverde (Mendoza Córdova, 2005). ...
... En el estado de Sonora afloran las rocas más antiguas de México, que incluyen rocas del Precámbrico y Paleozoico (Anderson y Silver, 1981), también afloran rocas más jóvenes del Mesozoico y Cenozoico (Rodríguez Castañeda, 1981). A continuación, se hace una descripción de manera general de las rocas de Sonora, comenzando de las más antiguas a las más jóvenes. ...
Abstract (Full text in spanish)
The “Cerro La Cementera” is Located in Hermosillo, Sonora, Mexico city, the area
is composed mainly of paleozoic metasedimentary rocks that were Intruded by a
64.9 to 60.5 ma intermediate composition intrusive granitoid body. The study area
has suffered structural faulting proccess by a NW-SE trending tertiary extensional
phenomena. The study focuses on the genetic aspects of the “Cerro La Cementera”
plutonic and metamorphic rocks and the skarn system supported by petrographic
and geochemical analyses. Petrographic studies were made to look for contact
metamorphism mineral paragenesis, primary and seccondary fabrics to clasificate
the rock appropriately according to SCMR and Meinert (2005) zonations.
Petrography shows a granoblastic-decusate fabric, locally some rocks show a
mylonitic-porphyroblastic fabric due to local fault zones. Isochemical metamorphism
zone is represented by a sequence of marbles and carbonate-silicate rocks with
Calcite - Diopside - Forsterite - Wollastonite paragenesis. Calc-silicate skarn zone is
represented by calc-silicated rocks with Wollastonite - Diopside -Vesubianite -
Garnet - Quartz paragenesis. The Garnet-Pyroxene Skarn zone is mainly composed
by Garnet-Vesubianite-Diopside-Wollastonite Calc-Silicated rocks as prograde
phase paragenesis, Calcite-Quartz-Epidote Calc-Silicated rocks as retrograde
paragenesis. XRD analyses shows Cu-Zn-Fe mineralogy that consists on
Carbonates, Oxides, Phosphates and Sulfides. Geothermobarometry and
Pseudocompound analyses were made to determinate metamorphism conditions
that generated “La Cementera” contact rocks. Geothermobarometry shows
tempreatures from 400 to 500°C associated to retrograde metamorphism and 600-
700°C associated to the prograde phase of the metamorphism and occured at low
pressures (2.9 - 4.0Kbar). Pseudocompound data indicates skarn paragenesis
occurence was domained by the CO2-H2O values more than a low pressures and
high tempreatures system, the “La Cementera” Skarn shows low CO2 (0.05-0.1%)
values and high H2O (99.9-99.95%) values hydrothermal fluids. Mineral paragenesis
and geothermobarometry classificates this metamorphism and metasomatism
between Amphibolite and Pyroxene Hornfels facies occured at very low CO2 values
and high H2O values hydrothermal magmatism.
... This area's geomorphology presents valleys, hills, and mountains aligned NNW-SSE, where peaks of up to almost 700 m high can occur. Hermosillo's geology (Fig. 1b) is generally composed of Paleocene igneous-metamorphic crystalline basement, with granites and granodiorites of continental arc-related cropping out in the mountains located on the eastern edge of the city (Rodriguez-Castañeda 1981). Calco-silicate hornfels and marbles host these units. ...
Studies focused on the seasonal distribution of pollen and spores in semiarid cities are scarce. At these sites, climate change potentiates the emission and transport of fine (PM10) to ultrafine particles (PM2.5), easily attached to pollen surfaces, causing allergen’s release. This study examines the potential correlation of seasonal variations of pollen, fungal spores, PM10, and meteorological parameters with allergic reactions of 150 people living in a Sonoran desert city. We collected PM10, airborne pollen, and spores during a year. We also studied topsoil and road dust samples as potential PM-emission sources. We obtained dust-mineralogy, chemistry, and particle size attached to pollen by X-ray diffraction and scanning electron microscope. Results show that seasonal high PM-loading in the urban atmosphere coincides with aeroallergens promoting micro- to nanoparticles’ attachment to pollen’s surface. A collapsed membrane was observed in several samples after individual grains show the following maximum wall coverage: Poaceae 28%, Asteraceae 40%, Chenopodiaceae-Amaranthacea 29%, Fabaceae 18%. Most of the particles covering pollen’s surface have a geogenic origin mixed with metals linked to traffic (bromide, chlorine, and antimony). Mineralogical, granulometric analysis, and main wind-direction show that two local soil-types are the main contributors to PM. A high frequency of positive sensitization to pollen with high particle loading was detected. These results suggest that climate-driven dust emissions may alter pollen and spore surfaces’ physicochemical characteristics with the further consequences in their allergenic potential.
Graphic abstract
... The mean annual temperature is 24.5°C and the mean annual precipitation is 349 mm (1966( -1998 Nacional del Agua). The principal parent material is Cretaceous granite [35]. The vegetation can be ascribed to the Plains of Sonora subdivision of the Sonoran Desert [37,43], but three major types of vegetation can be found in the area: 1) open desert typical of the Plains of Sonora subdivision, 2) xeroriparian vegetation along the ephemeral arroyos, and 3) tropical thornscrub on the hillsides. ...
We measured carbon mineralization in four different desert habitats (Arroyos, Hillsides, Canopies-Plains and Open-Plains) and the separate effect of litter addition from annual and perennial plants on soil microbial respiration using two laboratory soil incubation experiments. The differences in total aboveground phytomass among habitats correlates with soil nutrient content, soil particulate organic matter (POM) and consequently, C mineralization. The Arroyos habitat with the highest perennial plant phytomass and litter production, had the highest soil nutrient content, soil POM and C mineralization. Litter from annual plants had twice the P concentration than litter from the perennials, but only half the N concentration. Soil microbial respiration was higher with annual plant litter than with perennial plant litter in the Hillsides and Canopies-Plains, suggesting that microbial activity in both habitats was improved by litter with a higher C quality. In contrast, in the poorest habitat, the Open-Plains, the better response to the addition of perennial plant litter suggests that microbial activity may have been constrained by N input.
... The regional topography is typical of the buried ranges, with extensive piedmont alluvial plains, granitic Mesozoic hills, numerous Tertiary extrusive low-ranges, and isolated sedimentary Paleozoic rocks (Rodríguez-Castañeda 1981). The elevation varies between 220 and 600 m. ...
The seasonal pattern of litter production was analyzed in three contiguous desert communities near the southern boundaries of the Sonoran Desert. There was a large spatial variation in annual litter production mainly caused by differences in the composition and structure of vegetation. In the most productive site (Arroyos) annual litterfall was 357g m-2yr-1, a figure higher than some tropical deciduous forests. Litter production was only 60g m-2yr-1in the open desert in the plains (Plains) and 157g m-2yr-1 in the thornscrub on the slopes (Hillsides). Topographic and hydrologic features influence the composition, structure and function of the vegetation, modifying the general relationship between rainfall and productivity described for desert ecosystems. The temporal pattern of litter production showed marked seasonality with two main periods of heavy litterfall: one after the summer rains from September to November (autumn litter production) and another after the winter rains from March to May (spring litter production). In the open desert areas, spring litter production was significantly higher than the autumn pulse, while in the slopes, the autumn production was the most important. The Arroyos site produced similar litterfall amounts during the two dry seasons. The species composition defined the season of maximum leaf-fall. In the Plains, the vigorous winter growth of ephemeral and perennial plants made up most of the litter production, while in the Hillsides, most perennials remained dormant throughout the winter-spring period and a significant peak of litterfall occurred only after the summer growth. This difference in growth between seasons was less pronounced in the Arroyos. The timing of maximum production of reproductive and woody litter also differed from site to site.
A thorough review of the available literature regarding biostratigraphic studies on the Carboniferous sedimentary rocks of Sonora, northwestern Mexico, is presented here. Most frequently reported fossils are marine invertebrates as well as protozoans and vertebrate remains. Most abundant groups are corals, both solitary and colonial, fusulinids and other foraminifera, conodonts, and brachiopods. Less commonly described groups are crinoids, algae, bryozoans, and radiolarians. This revision evidences the high paleobiodiversity and potential research interest of the Carboniferous geological record of Sonora. Although published studies including paleontological information greatly lack detailed specific taxonomic determinations or biostratigraphic analyses, the presence of all Mississippian and Pennsylvanian stages can be inferred. Regional stratigraphic gaps and hiatuses, however, are difficult to determine because of this scarcity of precise datings. Current lithostratigraphic units defined formally or informally are also reviewed.
Anomalous high fluoride concentration up to 7.59mg/dm3 is found in groundwater from “La Victoria” area. This water is used to supply drinking water to Hermosillo City, Sonora. Geochemistry of groundwater, relationship between physicochemical parameters, hydrogeology and geologic setting were correlated to define the origin and the geochemical mechanisms of groundwater fluorine enrichment. High fluoride concentration is associated with high bicarbonates, pH and temperature, and it decreases toward the west and south of the area. Fluoride is in negative correlation to calcium concentration. Sodium sulphate facies of regional deep water flow are related to high fluoride concentration. High electric resistivity rocks associated with granites from the Sierra Bachoco basement might be the deep source of fluoride. Outcropping of Sierra Bachoco in the west causes upward regional flow. Groundwater of longer residence time can be pumped there. The anomalous area is restricted to “La Victoria” because calcareous paleozoic rocks outcrop to the south.
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