Central Sonora Research Articles

Ordovician and Devonian microfacies of Sierra Agua Verde, central Sonora, Mexico: A new locality of the Nuia Province from Western Laurentia

The Lower Ordovician carbonate rocks exposed in the Tuntunudé hill north of the Sierra Agua Verde, northeast of the town of Mátape, in central Sonora, consists of intraformational breccia, conglomeratic limestone, sandy limestone and limestone, which are overlain by a mixed succession of quartz sandstone and dolomitic sandstone. This succession is in turn unconformably overlain by an Upper Devonian sequence of dolomitic limestone, marl, conglomeratic limestone and sandy dolomite. The Lower Ordovician rocks contain abundant bioclasts of gastropods, brachiopods, trilobites, echinoderms, and sponges. Their microfacies show a marine medium to low energy environment, with sedimentation dominated by distal tempestites in laminar stages and intraclast debris formation during deposition. The depositional paleoenvironment corresponds to a marine middle-to-outer ramp. These strata are characterized by conodonts belonging to the Oepikodus communis and Reutterodus andinus biozones, as well as cyanobacteria incertae sedis Nuia sibirica. Devonian rocks overlying the Ordovician strata contain bioturbation and abundant bioclasts of echinoderms, brachiopods, bryozoans, gastropods, chaetetiform sponges, stromatoporoids; and also, colonial corals like Hexagonaria attenuata, Phillipsastrea hennahii and Phillipsastrea jachowiczi, monothalamous foraminifera like Vicinesphaera sp., monoserials such as Tikhinella measpis and planispiral such as Nanicella gallowayi. The microfacies show a high-energy environment in marine tropical shallow open-sea lagoonal waters, with ooids and reef building organisms.

Biostratigraphy of fusulinids from the lower Permian of central Sonora, Mexico. Paleoenvironmental implications

The central region of Sonora state, Mexico, is recognized by its different upper Paleozoic outcrops, highlighting the La Cueva Limestone and Mina México Formation. The rocks of Cerro Las Rastras and Sierra Martínez are considered among the most important Permian localities in central Sonora. This work studies the fusulinid faunas in two different sections, focusing on their biostratigraphical and paleoenvironmental relevance. Both sections comprise strata from the La Cueva Limestone and Mina México Formation. The fusulinids identified are Parafusulina sp., Paraskinnerella cf. skinneri, Praeskinnerella crassitectoria, Skinnerella cobachiensis, Skinnerella imlayi, and Eoparafusulina cf. linearis. The presence of Pa. cf. skinneri, Pr. crassitectoria, S. cobachiensis and S. imlayi indicates a lower–middle Leonardian (=upper Artinskian–lower Kungurian) age for the Las Rastras Section. The occurrence of E. cf. linearis in the base of the Sierra Martínez 2 Section suggests a youngest age of upper Wolfcampian for the bearing rocks. The microfacies analysis allowed the identification of six facies associations in the Las Rastras Section related to deep shelf, slope, and ramp-margin sand shoals. While three associations were identified in the Sierra Martínez 2 Section, indicating the deposition of open marine and slope environments. Fusulinids from both sections are classified as allochthonous elements in most facies associations (except those of open waters) since they are found in environments that are known to not been inhabited by these foraminifera. The fusulinids identified have a paleobiogeographic affinity with coeval assemblages from the North American Province.

Geodiversity Assessment in the Midriff Islands Region of the Gulf of California (Northwest Mexico)

A concurrent qualitative-quantitative assessment of geodiversity was carried out within the Midriff Islands, a priority region within the Gulf of California that stands out for its geological, ecological, and cultural importance. This study is carried out on the coast of central Sonora, where the Comcaac indigenous community has lived for more than a thousand years imbuing their territory with material and symbolic values. The objective of this study was to highlight the elements of geodiversity and contribute to the management and conservation strategies that are carried out in the area. The qualitative approach consisted of detailed fieldwork and a descriptive-documentary assessment of the geodiversity attributes of the study area, which led to the preparation of geomorphological and geological maps. The quantitative approach consisted of the elaboration of a geodiversity index map using an adapted methodology that considered some sites of cultural value due to their relationship with abiotic natural elements of geodiversity. As a result of both approaches, several localities and zones of high to medium geodiversity were identified mainly located along the mountain ranges and the coast. Coastal areas, although not having the highest geodiversity, could be considered the most relevant in terms of geological heritage and geoconservation, because they comprise a variety of rocky outcrops and extraordinary landforms with scientific interest, as well as cultural and aesthetic values. In addition, the concurrent assessment was favorable to recognize localities where geoconservation and sustainable use strategies, such as geotourism, can be implemented.

Depositional facies of Cambrian Series 2 – Miaolingian transition in the El Sahuaral Hill, central Sonora, Mexico: Paleoenvironments and regional stratigraphic correlation

Studies on lower Paleozoic sedimentary facies are scarce in northwestern Mexico, and the information is mainly restricted to Ordovician sequences in central Sonora. Series 2 – Miaolingian detrital-carbonate deposits of the El Sahuaral Hill located in central Sonora, northwestern Mexico, were analyzed for siliciclastic and carbonate microfacies, and biofacies based on the presence of trilobites. This research fills a gap in the knowledge of Cambrian strata in Mexico and is based on 25 thin sections, where the microfacies analysis resulted in recognition of one siliciclastic (M1), eight carbonate microfacies (M2-M9), and three biofacies (B1–B3). Based on the information obtained, the silicilastic microfacies (M1) for the Proveedora Formation indicates a shallow marine environment in intertidal to subtidal conditions related to the Skolithos ichnofacies. The carbonate microfacies M2, M3, M4, and M5 for the Buelna Formation denote a carbonate platform that varies between a lagoonal environment of open circulation and a restricted platform. Microfacies M6 and M7 for the Cerro Prieto Formation were deposited in carbonate sand shoals and banks within a moderate-energy environment in restricted platform, and open marine to platform-margin sand shoal within a high-energy environment. On the other hand, the faunal associations in the El Gavilán Formation allow to recognize three main biofacies: B1 is characterized by the presence of Euagnostus and abundant of agnostid trilobites; B2 is characterized by the presence of various genera of trilobites of the family Oryctocephalidae; and B3 represents trilobites of the genera Elrathina and Bathyuriscus. In accordance with the above, for the El Gavilán Formation, it is established that it was deposited on an external platform, transiting to a deeper environment towards the slope area. Microfacies M8 and M9 of the El Tren Formation indicate a transition from an open marine platform to a restricted circulation lagoonal environment, possibly at the outer margin of the carbonate platform, exposed to surface waters and mixed with meteoric water.The El Sahuaral Hill strata record environmental and eustatic changes, where abrupt facies change occurred from inner to outer platform during the Cambrian Series 2 – Miaolingian. The above correlate with other deposits in North America (Nevada, California, and British Columbia) which record relatively drastic eustatic changes at the platform edge. Furthermore, the lithological and faunal characteristics of the El Gavilán Formation in the El Sahuaral Hill suggest an affinity with the deposits of Sonora, Clayton Ridge in Nevada and the Burgess Shale Lentil, which is a member of the Stephen Formation in British Columbia, where the paleogeographic identity with the North American craton is confirmed within an outer platform environment.

Can legume seeds establish after land degradation by buffelgrass? Evidence to initiate restoration in Central Sonora, Mexico

AbstractBuffelgrass (Pennisetum ciliare) has been introduced in many localities of northwestern Mexico for cattle grazing. Recent studies have documented how the conversion of natural vegetation to buffelgrass pastures affects several ecological processes that result in high levels of desertification and the subsequent abandonment of lands. However, no previous study has documented successful restoration in these habitats. In this paper we report the results of several experiments focused on the restoration of these areas using native legume species of the region. We selected a degraded buffelgrass pasture considered unproductive by local ranchers in central Sonora. We carried out experiments to evaluate seed removal, seedling emergence, and seedling establishment of native legumes species (Prosopis glandulosa, Parkinsonia microphylla and P. praecox). Our results showed that P. microphylla had greater emergence (10%) than the other two species despite the high seed removal recorded. In addition, P. microphylla was the species with the highest survival (1.4%). Thus, our results show that ecological recovery using native species is possible in desertified buffelgrass pastures. Considering the ecological benefits of P. microphylla in the Sonoran Desert (i.e., nurse plant, positive associations, plant‐growth promoting), this species could be considered highly valuable in restoration procedures.

Distribution and habitat of Ocelot (Leopardus pardalis) in Sonora, México

The ocelot (Leopardus pardalis) ranges from northeastern Argentina to southern Texas and southeastern Arizona. It is listed as Endangered in Mexico and the United States. Previous works on ocelots in Sonora, found them occupying different habitats, including tropical deciduous forest, thornscrub, desert grassland, oak woodland, and pine-oak forest, avoiding the driest areas of the Sonoran Desert. The majority of our records are from camera traps, with indirect records from tracks. We analyzed images and videos of more than 100 camera traps used to monitor wildlife in ranches and natural protected areas of Sonora. Cameras were set at an altitude of 70 to 100 cm above ground, some were baited with a sardine-tomato mixture, others were not, the majority were set in areas where other species were the main objective. We obtained 147 recent records from 2015 to 2021 and 28 previous records of ocelots in Sonora. Ocelots occur in the eastern half of Sonora, avoiding areas with less than 400 mm of annual rainfall in the eastern and northwestern Sonoran Desert. Ocelots have been recorded from 53 to 2,151 m elevation (av. 996 m). 21 images in nine localities show females with kittens, indicating breeding populations. In southern and east-central Sonora, ocelots live in tropical deciduous forest, and foothills thornscrub. At Maycoba east of Yécora, in Sierra Huachinera and in the Sky Islands Mountain ranges in northeastern Sonora, ocelots live in temperate vegetation, including desert grassland, oak woodland, and pine-oak forest. Ocelots have been recorded in riparian habitats, transecting other vegetation types in the principal rivers of the state: Ríos Bavispe-Yaqui, Mayo, and Sonora, which drain the Sierra Madre Occidental, the Sky Island Region and southeastern Arizona to the Gulf of California, providing dispersal corridors. Other medium sized rivers provide corridors for the dispersal of ocelots, such as Río Mátape in central Sonora, and Ríos Cocóspera, San Pedro, and Santa Cruz in the north. The nearest Sonoran populations to Arizona are in the Sierra El Alacrán and Río Cocóspera on Rancho El Aribabi.

Depositional environments and transgression-regression cycles in the Mural Limestone, central Sonora, Mexico

Results of analytical studies in the Mural Limestone of the Bisbee Group exposed in northwest Mexico, carried out to determine the paleo-bathymetry of the marine depositional environment, reveal that deposition occurred in a restricted carbonate platform environment, varying from inner-neritic to shelf margin with the development of lagoon, shoal and biohermal conditions, reflecting minor transgression-regression cycles. Furthermore, the fossiliferous content and lithological characteristics support the interpretation that the studied section corresponds to the transition between Cerro La Puerta and Cerro La Espina members of the Mural Limestone.

Monarch Butterflies in Sonora and Adjacent Northwestern Mexico

Since 1979, observations of monarch butterfly (𝐷𝑎𝑛𝑎𝑢𝑠 𝑝𝑙𝑒𝑥𝑖𝑝𝑝𝑢𝑠 L.) in Sonora, Mexico have been low. There are 10 records of monarchs breeding in Sonora on 𝐴. 𝑙𝑒𝑚𝑚𝑜𝑛𝑖𝑖, 𝐴. 𝑙𝑖𝑛𝑎𝑟𝑖𝑎 y 𝐴. 𝑠𝑢𝑏𝑢𝑙𝑎𝑡𝑎 (Apocynaceae).In July-August, monarchs from the Canelo-Hereford area in Arizona fly to the Río San Pedro, Sonora, south to the Cananea area, and then in the Río Sonora through central Sonora to Hermosillo and the Gulf of California. From the Río Sonora, they move up into the Sky Island Mountain ranges. In Hermosillo, they thrive in urban gardens. Higher humidity along the coast allows them to disperse in arid habitats from Bahía de Kino north to Punta Chueca and south to Guaymas. Individuals observed in northwestern Sonora may be from the Colorado River population in western Arizona- southeastern California.The population in tropical southern Sonora and western Sinaloa with winter feeding and breeding may be resident, reflecting the continuously blooming and abundance of the native 𝐴. 𝑐𝑢𝑟𝑎𝑠𝑠𝑎𝑣𝑖𝑐𝑎 in large areas of tropical deciduous forest converted into agricultural fields.Monarchs tagged in southeastern Arizona recovered in Michoacán (Morris 𝑒𝑡 𝑎𝑙. 2015; Billings 2019) likely traveled eastward to the Janos area in northwestern Chihuahua on the east side of the Sierra Madre Occidental to join the southward migration across the Mexican Plateau.From the relatively few monarch records in Sonora, the few observations in the Sierra Madre Occidental in Sonora and Chihuahua,and winter feeding-breeding populations in tropical southern Sonora and western Sinaloa, we conclude that the Sonoran population is not connected to the eastern migration to overwintering sites in Michoacán. Like the Rocky Mountains, the Sierra Madre Occidental is more a barrier to migration than a corridor.

Middle Ordovician (Whiterockian) gastropods from central Sonora, Mexico: affinities with Laurentia and the Precordillera

AbstractThe Lower–Middle Ordovician (Ibexian, Whiterockian) sedimentary rocks exposed at Rancho Las Norias includes the informally named Las Norias formation, which consists of an intercalation of carbonate and clastic sediments with abundant marine fauna. These deposits occur as the most austral sedimentary rocks of Ordovician age for Laurentia, providing a critical link to understand the distribution of Ordovician marine faunas of North America. An investigation of the gastropod fauna from the upper portion of the Las Norias formation, Sonora, Mexico, is undertaken for the first time. The gastropod assemblage includes Maclurites acuminatus, ?Monitorella sp., Lecanospira sp., Malayaspira aff. M. rugosa, Lophospira perangulata, and Hormotoma? sp. This assemblage indicates a paleogeographic relationship with Laurentia, including the USA (Nevada), Canada (British Columbia, Newfoundland), Greenland, and the Argentine Precordillera.

Depositional Environments and Transgression-Regression Cycles in the Mural Limestone, Central Sonora, Mexico

Depositional Environments and Transgression-Regression Cycles in the Mural Limestone, Central Sonora, Mexico

Quantitative paleoecology of Cambrian (Series 2–Miaolingian) communities from central Sonora, Mexico

This work presents a paleoecological approach to study benthic communities preserved in Cambrian strata exposed at the Sahuaral locality in central Sonora, northwestern Mexico. Based on species richness and abundance, this work analyzed 627 individuals corresponding to 33 species from five distinctive Cambrian formations: the lowermost Proveedora Formation characterized by bioturbation horizons that record the occurrence of a benthic-infaunal biota from coastal shallow seas, followed by the Buelna Formation which contains reef deposits dominated by autotrophic epibenthic communities. The Cerro Prieto Formation was deposited in a high-energy shallow marine environment, dominated by primary consumers-epifaunal and suspensions feeders. The uppermost unit, the El Gavilán Formation, is an intercalation of shale and fossiliferous limestone characterized by the fossil remains of suspension feeders, detritus feeders and nektobenthic organisms of low energy deep water environments. The paleobiota consist of ichnofossils, microbial oncolites, chancellorids, brachiopods, hyolithids, and trilobites in a sequence of increasing diversity and complexity. Paleoecological indices (Simpson Dominance, Shannon-Weaver Index, Evenness Index, and Total Richness) were determined and compared in the study area. In addition, the effective number of species and the true diversities were obtained, which are similar between each station distributed in each formation. However, it is possible that the high degree of dominance is a factor to indicate an inequality between the true diversity and the species richness identified. These results provide new analytical and paleoecological criteria for better understanding depositional environments and fossil associations where the spatial distribution of benthic organisms, richness and abundance provide a valued window to Cambrian biotas. The structure of the marine community of the El Sahuaral area has a great affinity with other Cambrian communities, such as those from the Stephen Formation (Burgess Shale, British Columbia) and the Chengjiang biota of the Yangtze Shelf deposits in South China.

Paleoecology of a Lower Cretaceous (lower Albian) marine community of Cerro de Oro, central Sonora, Mexico

The Early Cretaceous time is characterized by regression and transgression events in the oceans, which impulsed the radiation processes of species. In particular, these oscillation events controlled the distribution of marine invertebrates because they generated geographical barriers and the geographical connection between the different ecological niches. These events promote speciation of which there is a limited record in the state of Sonora. This work is the first quantitative paleoecological study of Early Cretaceous marine invertebrate fauna from central Sonora. The Mural Limestone exposed at the El Caloso Hill, located in the Cerro de Oro area, comprises 28 invertebrate taxa belonging to several groups such as corals, bivalves and gastropods, cephalopods, and echinoderms. These paleocommunities are part of the Early Cretaceous Mexican Sea, which covered the southwestern United States and Mexico during regressive/transgressive events. To evaluate and compare the diversity and richness of these paleocommunities, paleoecological indexes like the Simpson Dominance and Evenness index, Shannon index, Menhinick Species Richness, Total Chao Richness, and Pielou's Evenness index have been applied. In addition, the distribution described for these paleocommunities was defined as a clumped type. The limestone textures described for these environments comprises wackestone, and floatstone, typical of a shallow lagoon environment with low energy. Finally, the dominant guilds were represented by epifaunal sessile suspension, infaunal sessile suspension, and semi-infaunal facultative vagile suspension feeders.

Porifera and Chancelloriidae of the Cambrian of Sonora, Mexico: A review

Archaeocyaths, articulated reticulosans, protospongiid sponge spicules, fragments of chancelloriid scleritomes and isolated sclerites are typical components of the lower-middle Cambrian Sonora biota of Mexico. This report briefly introduces the Cambrian sponges and chancelloriid fossils of the Sonoran platform described and illustrated to date.Early Cambrian (Series 2, stages 3 and 4) sponge spicules, Kiwetinokia sp. and extinct sponge-like archaeocyaths occur in the Puerto Blanco Formation, at the Cerro Clemente and Cerro Rajón in the Caborca region, northwest Sonora. Besides, a variety of chancelloriid sclerites belonging to Chancelloria, Allonia, and Archiasterella have been described in that region. Also, Chancelloria sclerites have been documented in the Arrojos Formation of the Caborca region.A fauna of hexactinellid sponges and chancelloriids was recorded from the middle Cambrian (Wuliuan Stage, Miaolingian Series) strata from the Arivechi section, in the eastern part, and San José de Gracia and El Sahural sections in the central Sonora. The middle Cambrian El Mogallón Formation in the Arivechi area yield assemblages of reticulosan thin-wall sponges, isolated protospongiid spicules and chancelloriid sclerite morphotypes. Fragments of articulated scleritomes of Chancelloria eros were reported for the first time for the Cambrian of Mexico, and sclerites of Allonia and Archiasterella in the Cerro El Sahuaral near San José de Gracia. Protospongiid spicules and isolated sclerites of chancelloriids were determined in the Cerro El Chihuarruita section at the San José de Gracia area.The mid-Cambrian Sonoran faunas have been compared with the Burgess Shale biota in Canada, and those of the Utah formations, in the USA localized around the Laurentia. Nevertheless, as the chancelloriid fauna is cosmopolitan, some of these genera are also present in other palaeocontinent including Siberia, China, and Australia.Sponges and chancelloriids are an important biotic component of the Sonoran communities. Their discovery constitutes a valuable tool for the reconstruction of the faunas, their paleoecology and paleoenvironments. These findings expand the paleogeographical distribution of these faunas during the Cambrian in the warm platform of Sonora.

Geochemical changes of Mn in contaminated agricultural soils nearby historical mine tailings: Insights from XAS, XRD and, SEP

Manganese is ubiquitous in nature and essential for some metabolic reactions, but also it is present in the environment as a product of anthropogenic activities. Despite evidence linking high concentrations of Mn to several diseases, it is not commonly considered during environmental risk assessment of soils. Changes in chemical forms, oxidation state, and speciation of Mn in impacted agricultural soils by historical mine tailings in central Sonora in northwestern Mexico were studied using X-ray Absorption Near Edge Spectroscopy (XANES), X-ray Diffraction (XRD), and Sequential Extraction Procedures (SEP) techniques. Mn concentrations ranged from 1093 to 2919 mg·kg−1 in these soils, which exceeded the local geochemical background by up to six-fold. According to SEP, the tendency found in agricultural soils was reducible (42–66%) > soluble and exchangeable (16–42%) > residual (5–22%) > oxidizable (4–24%). In contrast, the tendency in sulfide-rich tailings samples was soluble and exchangeable (47–49%) > residual (35–41%) > oxidizable (5–11%) > reducible (5–7%), and in oxide-rich materials was residual (21–79%) > soluble and exchangeable (1–30%) > reducible (1–45%) > oxidizable (2–15%). The considerable percentage of the soluble forms indicated the potential of mobilization and availability to exposed organisms. No Mn-bearing mineral phases were identified with XRD, which suggested that manganese was mostly found in low-crystalline forms. XANES measurements indicated that the oxidation state of Mn in agricultural soil samples varied from Mn2+ through Mn4+. Conversely, the main oxidation state in mine tailings samples was Mn2+. Substantial changes were detected in Mn XANES spectra in the whole sample and residues left from SEP in agricultural soils, which confirmed the presence of all chemical forms (e.g., soluble and exchangeable, reducible, oxidizable, residual). A well-defined structure spectrum was obtained in soils once low crystallinity species and/or organic compounds were removed, which was similar to that acquired for mine tailings, suggesting mobility from tailings deposit to agricultural soils. Substantial contribution of compounds with mineral structures like birnessite (((Na, Ca, K)0.6(Mn4+, Mn3+)2O4·1.5H2O) and minor contributions of hausmannite (Mn3O4), spessartine (Mn3Al2(SiO4)3) and szmikite (MnSO4) were identified by Linear Combination Fitting (LCF) in soils, whereas the significant contribution of structures like hausmannite and spessartine, and minor contributions of rhodochrosite were found in tailings material. An LCF analysis in residues from SEP also suggests that the chemical species involved in the Mn mobilization were scachite and szmikite. In general, the results obtained indicate that leaching processes favored the presence of chemical species of Mn with a considerable potential of mobility and toxicity in agricultural soils interacting with historical mine tailings in central Sonora.

Cambrian (Series 2 to Miaolingian) platform facies from central Sonora, Mexico and the regional correlation

This study provides new insights about depositional paleoenvironments through siliciclastic microfacies, carbonate microfacies, and biofacies analysis from sedimentary formations of the lower and middle Cambrian (Stage 4–Wuliuan), exposed in central Sonora, northern Mexico. Results of the petrographic analysis of 48 samples revealed the following lithologies: quartzarenite, oncolytic rudstone, grainstone-packstone, wackestone, mudstone, and to a lesser extent sandy limestone. Two siliciclastic microfacies were identified: (A) quartzarenite with cross-bedded and horizontal stratification deposited in an intertidal and supratidal environment; and (B) massive quartzarenite with Skolithos ichnofacies deposited in subtidal and intertidal environments. Four carbonate microfacies were identified: microfacies 1 is a sandy limestone with trilobite fragments; microfacies 2 is a grainstone with intraclasts, salterellids, hyolithids, trilobites, and echinoderms plates; microfacies 3 is an oncolytic rudstone consisting of microbes and abundant echinoderms plates; and microfacies 4 is a packstone-grainstone with abundant ooids, trilobite fragments, and echinoderm plates. Two biofacies were identified: Agnostid-polymeroid biofacies with predominance of the trilobites Pentagnostus, Bathyuriscus, Oryctocephalites, and Elrathina; and Pagetia biofacies with abundant trilobites of the genera Pentagnostus, Pagetia and Elrathina. It is concluded by the sedimentation model that changes in sea level is the most important parameter in determining the siliciclastic microfacies, carbonate microfacies and biofacies; as well as the depositional environments that vary from the coastline (subtidal to supratidal) to shallow-water open circulation marine platform with low and high energy waters. The Cambrian deposits of northern Mexico are correlated with the deposits of California and Nevada (USA), as well as to the Precordillera (Argentina), where the species in common show a strong affinity.

First record of Ubaghsicystis (Eocrinoidea - Echinodermata) from the Cambrian (Miaolingian, Wuliuan) of Sonora, Mexico: Biostratigraphical and paleoecological considerations

Introduction: The present work constitutes the first record of Ubaghsicystis Gil-Cid & Domínguez-Alonso (Echinodermata-Eocrinoidea) in the El Gavilán Formation, exposed in the El Sahuaral Hill, a new Cambrian locality of central Sonora, Mexico. The El Gavilán Formation is a sedimentary sequence mainly made up of shale interbedded with limestone, with abundant invertebrate fossils, deposited in an open shelf marine environment. Objective: The main objective of this research work is to describe the species Ubaghsicystis cf. U. segurae for the first time in Mexico, in addition to biostratigraphic and paleoecological considerations. Methods: A composite stratigraphic section of the El Gavilán Fm. was measured in central Sonora, where samples corresponding to eocrinods were collected, the material was examined in the Microscope Leica MZ10. Results: The biotic association is composed of reticulosan sponges, chancelloriids (Chancelloria eros, Allonnia tintinopsis, Archiasterella sp.), hyolithids, brachiopods, trilobites (Quadragnostus depressa, Peronopsis sp., Tonkinella valida, and Elrathina sp.), and echinoderms (Ubaghsicystis cf. U. segurae). Regarding the age, the trilobite association establishes a chronostratigraphic position from the middle Cambrian (Miaolingian, Wuliuan), Altiocculus Subzone, Ehmaniella Zone. The material studied is constituted by isolated echinoderm plates, which probably represent various cycles of theca plates assigned to Ubaghsicystis cf. U. segurae. The genus Ubaghsicystis has been scarcely recorded in a few Cambrian regions (e.g., Burgess Shale in Canada and Los Barrios de Luna in Spain), so that the information about this taxon is limited. Conclusions: The Cambrian succession of Sonora, where Ubaghsicystis occurred, was part of the border from the Laurentia craton during this period, located near the Paleoequator during this period, where ideal conditions for increasing diversity and abundance of species were developed, including echinoderms.

Analyzing water policy impacts on vulnerability: Cases across the rural-urban continuum in the arid Americas

Climate change is posing emerging threats to people and the environment, particularly in arid regions. However, some groups are more vulnerable than others, depending on their levels of exposure, sensitivity and adaptive capacity, which are determined by climatic and non-climatic factors. In water-scarce environments, water policies become key non-climatic factors that affect vulnerability yet enable modifications if their impacts unintentionally exacerbate vulnerability. Therefore, it is necessary to analyze the impacts of water policies on vulnerability, particularly for disadvantaged groups. In this paper, we analyze four cases in the arid Americas that illustrate an array of challenges at different scales and across the rural-urban continuum: (1) irrigated oases in Mendoza, Argentina, where groundwater and surface water management are disconnected; (2) rural communities in central Sonora, Mexico, where local water rights have been transferred to large scale mining; (3) peri-urban marginalized neighborhoods in Hermosillo, Mexico, where competition for water is driving changes in land use; and (4) underserved communities in Tucson, Arizona, USA who are left behind in a rainwater harvesting movement. Our analysis shows that water policies in arid regions interact with land and neoliberal policies between sectors across different scales, exacerbating vulnerabilities disproportionately in less privileged groups and enhancing disparities. Here, we offer recommendations for more inclusive policymaking processes that can build capacity, protect the livelihoods of disadvantaged groups, and reduce their vulnerability to climate change.

Cambrian stratigraphy (Series 2 to Miaolingian) of the El Sahuaral area in central Sonora, Mexico: Biostratigraphic implications

The lower and middle Cambrian strata exposed in the state of Sonora, Mexico, consists of sequences of quartzarenite, limestone, shale and dolomite exposed in several localities, mainly in the northwestern and central regions of Sonora. Approximately 800 m interval of Cambrian marine sedimentary rocks are exposed in the El Sahuaral area, a new Cambrian locality in central Sonora. The sedimentary succession of these marine facies is divided into five lithostratigraphic units previously documented in Mexico: Proveedora, Buelna, Cerro Prieto, El Gavilán and El Tren formations. The Proveedora Formation is the oldest sequence of Cambrian strata in the region and consists of a 168 m thick sequence of bioturbated, fine-grained quartzarenite. The Buelna Formation conformably overlies the Proveedora Formation in the El Sahuaral and adjacent areas and consists of 70 m of interbedded limestone and shale, with abundant fragments of olenellid trilobites from either the Bristolia mohavensis or Bristolia insolens zones (Series 2, Stage 4). The overlying Cerro Prieto Formation is composed of a 70 m thick sequence of recrystallized oolitic limestone with possible fragments of Amecephalus arrojosensis, suggesting the Amecephalus arrojosensis Zone (uppermost Series 2, Stage 4). The El Gavilán Formation conformably overlies the Cerro Prieto Formation with a thickness of 225 m; it is composed of interbedded limestone and shale deposited in a marine open shelf environment, with abundant fauna of the upper Ehmaniella Zone (Altiocculus Subzone), Ptychagnostus praecurrens - Ptychagnostus gibbus Zone (Miaolingian Series, Wuliuan Stage). The El Tren Formation, reported by the first time in central Sonora, conformably overlies the El Gavilán Formation and consists of 250 m thick sequence of dolomitic limestone with unidentified trilobite fragments. The Cambrian deposits of central Sonora present marine facies that vary from the littoral zone to open marine shelf, accumulated in the western part of the North American craton and contains an abundant and diverse biota comprised by cyanobacteria, poriferans, brachiopods, trilobites, and echinoderms.

Landscape Dynamics in an Iconic Watershed of Northwestern Mexico: Vegetation Condition Insights Using Landsat and PlanetScope Data

Natural vegetation in arid and semi-arid environments of Northwestern Mexico has been subject to transformation due to extensive and intensive human occupation related mostly to primary activities. Keystone habitats such as riparian ecosystems are extremely sensitive to land use changes that occur in their surrounding landscape. In this study, we developed remote sensing-based land cover classifications and post-classification fragmentation analysis, by using data from Landsat’s moderate resolution sensors Thematic Mapper and Operational Land Imager (TM and OLI) to assess land use changes and the shift in landscape configuration in a riparian corridor of a dynamic watershed in central Sonora during the last 30 years. In addition, we derived a high spatial resolution classification (using PlanetScope-PS2 imagery) to assess the “recent state” of the riparian corridor. According to our results, riparian vegetation has increased by 40%, although only 9% of this coverage corresponds to obligate riparian species. Scrub area shows a declining trend, with a loss of more than 17,000 ha due to the expansion of mesquite and buffelgrass-dominated areas. The use of moderate resolution Landsat data was essential to register changes in vegetation cover through time, however, higher resolution PlanetScope data were fundamental for the detection of limited aerial extent classes such as obligate riparian vegetation. The unregulated development of anthropogenic activities is suggested to be the main driver of land cover change processes for arid ecosystems in this region. These results highlight the urgent need for alternative management and restoration projects in an area where there is almost a total lack of protection regulations or conservation efforts.

New conodont data related to the western Ouachita-Marathon-Sonora orogen: Age of the autochthonous Laurentian deformation

We report herein new Permian conodont data from the strata of the La Cueva Limestone and the Mina Mexico Formation in central Sonora. These data allow us to characterize the biostratigraphy of the southwestern Laurentian Permian successions and the last stage of the Ouachita-Marathon-Sonora orogen in northwestern Mexico. We studied three sections in central Sonora, which cover the stratigraphic contact between both formations. In the Las Rastras Section (LRS), we recognized a conodont association that includes Neostreptognathodus exsculptus sensu Henderson and McGugan, Sweetognathus “whitei”, Sw. subsymmetricus, and Hindeodus aff. H. minutus at its base and Sw. subsymmetricus, Hindeodus aff. H. gulloides, Gullodus tieqiaoensis, and Mesogondolella siciliensis at its top. These conodonts date the upper part of the La Cueva Limestone as latest early to earliest late Kungurian and the lower part of the Mina Mexico Formation as late Kungurian in the LRS. In the Sierra Martinez 1 and 2 sections (SMS-1 and SMS-2), located 7 km to the east of the LRS, the conodont association points to an age corresponding to the latest early to earliest middle Kungurian for both La Cueva Limestone and Mina Mexico Formation. This association is represented by the species Ns. exsculptus sensu Henderson and McGugan and Sw. subsymmetricus. The stratigraphic contact between both formations has been interpreted as the beginning of the autochthonous deformation of the Laurentian platform. This new conodont data allows us to associate this event to the latest early–earliest middle Kungurian in SMS-1 and SMS-2, and to the late Kungurian in the LRS showing a diachrony between these localities. This diachrony may be related to the continental oblique collision of Laurentia against Gondwana that resulted in progressively younger basins westward along the Ouachita-Marathon-Sonora orogen. This diachrony can also be due to the configuration of the subsiding Mina México foredeep, which would have produced a non-coeval contact in the areas closer to the thrust front and those located far from it.