Oriental Basin Research Articles

Paleoenvironmental conditions during the Medieval Climatic Anomaly, the Little Ice Age and social impacts in the Oriental Mesoamerican region

The Medieval Climatic Anomaly and the Little Ice Age periods are the most relevant climatic events in the last 1000 yr BP. Although some research describes the effects on Mesoamerican paleoenvironmental conditions and the potential atmospheric-oceanic drivers involved, more studies are needed. While most paleoenvironmental records reveal a Medieval Climatic Anomaly dominated by arid conditions, the paleoclimatic signature of the Little Ice Age seems to be more controversial. Some records display prevailing drought conditions and a minor number of records suggest wetter conditions. Here, we present a new high-resolution paleoenvironmental record from the Serdan Oriental Basin, located in the Oriental Mesoamerican region. We employed the partly laminated sedimentary sequence from the Alchichica crater maar lake. A multi-proxy study by means of microfacies analyses, geochemical analyses, mineralogical composition and magnetic analysis was conducted. Enhanced endogenic calcium carbonate precipitation in the Alchichica lake points to dominant dry conditions during the Medieval Climatic Anomaly. On the other hand, the Little Ice Age represented the rise of predominantly wetter conditions interrupted by short drought intervals. The wetter event is described by increased varve preservation, detrital input, and decreased calcium carbonate precipitation. Furthermore, we argue that the variability of the North Atlantic Oscillation in conjunction with hurricane activity could have influenced the hydrological patterns during both climatic anomalies in the Oriental Mesoamerican sector. Finally, we hypothesize that severe drought conditions registered during the Medieval Climatic Anomaly, which encompasses the Postclassic archeological period, had severe implications in two important landscape elements useful to the agriculture lifestyle: El Salado lacustrine plain and piedmonts.

Hydrochemical and isotopic characteristics of groundwater in the Continental Intercalaire aquifer system: Insights from Mzab Ridge and surrounding regions, North of the Algerian Sahara

Study regionNorth of Sahara, Algeria. Study focusThe effects of water/rock interactions and hydrodynamic conditions on the characteristics of groundwater in the Continental Intercalaire aquifer (CI) are demonstrated using hydrochemical and isotopic data from the Mzab Ridge. New hydrological insightsThe results confirm that CI groundwater in the oriental basin is highly mineralized (1010 > EC > 3500 μS/cm) and is of the SO4-Cl-Na type. However, it is poorly mineralized (340 > EC > 960) in the occidental basin and predominantly belongs to the HCO3-Ca type. The important contribution of evaporite minerals has been deduced using saturation indices and minor element ratios of Sr/Ca and Br/Cl. This is explained by lithological heterogeneities within the CI aquifer and corroborates the observations from regional piezometric features which suggest a groundwater divide located between 31.55° and 31.57 °N latitude. δ18O-NO3 and δ15N-NO3 analyses show that NO3 has a predominantly natural origin, which is soil nitrification even for the high concentrations exceeding 50 mg/L. CI groundwaters are highly depleted in both δ18O and δ2H compared to modern rainfall isotopic signatures. The most depleted ones are those situated in the Great Oriental Erg sub-basin. Isotopic values as low as δ18O=−6‰ can be taken as the limit for groundwater that is typically old. In the El Golea region, isotopic enrichment seems to indicate mixing between old groundwater and evaporation-affected groundwater infiltrating through the dunes of the Great Occidental Erg.

Evaluación del grado de conservación de las cuencas hidrográficas de Nuevo León, México

Se evaluó la condición de conservación de las cuencas hidrográficas de Nuevo León, mediante el análisis de 48 variables ambientales para construir cuatro índices. Cuatro de las 14 cuencas del estado cubren 79 % del territorio estatal, destacan la cuenca Río Bravo - San Juan por albergar al Área Metropolitana de Monterrey que concentra más de 90 % de la población estatal. En contraste, seis cuencas comprenden 2 492 km2 (3.9 % del territorio total), por lo que se consideran marginales. Estas y la cuenca Río Soto La Marina obtuvieron las puntaciones más bajas para el Índice de Sitios con Declaratoria Oficial (< 2.4 puntos). Las tres cuencas con los mayores valores para el índice de Sitios Prioritarios Propuestos corresponden al grupo de cuencas marginales: Sierra de Rodríguez, Río Tamesí y Matehuala con valores de 45.3, 39.1 y 36.8 puntos, respectivamente. Río Bravo - San Juan y Río San Fernando tuvieron los registros más altos para el Índice de Impacto Ambiental, con 60.7 y 40.5 puntos, respectivamente. El Índice del Grado de Conservación, fue positivo para cinco de las 14 cuencas: Río Tamesí, Sierra Madre Oriental, Matehuala, Sierra de Rodríguez y Presa San José - Los Pilares, cuatro de las cuales son marginales; sin embargo, su extensión conjunta representa solo 2.3 % del estado. La quinta cuenca con valor positivo para este índice fue la Sierra Madre Oriental. Las nueve cuencas presentaron valores negativos para este índice, lo que significa que los impactos ambientales superan a sus atributos de conservación.

Diet selectivity in relation to food quality and availability by the endemic Perote squirrel (Xerospermophilus perotensis)

Climatic fluctuations have a biogeochemical effect on food availability and quality, resulting in adjustments of the foraging and food selection behavior of animals. Our study aimed to evaluate the influence of seasonal variation on abundance of food resources and its effect on food selection of Xerospermophilus perotensis, an endemic species of ground squirrel in the Oriental Basin. Food selection behavior was recorded using focal animal and continuous behavior sampling on a squirrel population inhabiting the grassland of a semi-arid area. The results show that their diet consisted of 6 plant species with significant differences in the time spent feeding on each plant species (X2 = 128.96; P = 0.01). The species with the highest feeding times included Scleropogon brevifolius (63.6 %), Verbena bipinnatifida (10.6 %) and Erigeron pubescens (10.5 %). These plant species had the highest percentage of vegetation cover and availability among seasons, but they were of low nutritional quality with regard to their protein/fiber ratio. However, during specific periods, associated either with gestation and lactation or prior to hibernation, the squirrels increased their protein consumption. This suggests that squirrels are opportunistic feeders, and under certain conditions tend to select plant species that provide them with better quality diets.

Incrustation ability of geothermal waters of the Continental Intercalaire aquifer in the Grand Erg Oriental basin (Algeria and South Tunisia)

The chemical composition of groundwater from wells tapping the Continental Intercalaire (CI) aquifer in the Grand Erg Oriental basin and the detailed analysis of saturation indices enable identification of the mineralization origin. CI groundwater is characterized by a Ca–SO4/Cl abundant water type and a Na–Cl second type. Chemical pattern is controlled by evaporites dissolution (halite, anhydrite and gypsum). Recently, the decrease in these CI geothermal water wells performance is explained by an incrustation in the well screen. To study the scaling process, we used the degree of calcite saturation, hardness and Langelier Saturation Index (LSI). It has been demonstrated that scaling potential is the most important in the basin axis, around El Oued region (southern Algeria) and in the south-east of Tunisia and the Chott Djerid borders (El Hamma of Gabes, Tozeur and Kebili) corresponding to the discharge zones. However, the scaling potential decreases towards Algerian reliefs (Tademait and Tinrhert) representing aquifer recharge zones.

Embryonic Growth Rate Thermal Reaction Norm of Mediterranean Caretta caretta Embryos from Two Different Thermal Habitats, Turkey and Libya

Abstract Ectothermic species are strongly affected by thermal changes. To assess the viability of these species under climate change constraints, we need to quantify the sensitivity of their life history traits to temperature. The loggerhead marine turtle (Caretta caretta) nests regularly in the Oriental Basin of the Mediterranean Sea. The different populations are separated because of time (< 12,000 yrs) and very different thermal habitats; it is hotter on the southern coast (Libya) than on the northern ones (Cyprus, Greece, and Turkey). Patterns of embryo growth response to incubation temperatures have been searched for these 2 populations. We found that both populations have similar thermal reaction norms for embryonic growth rate. This highlights that 12,000 yrs is not enough time for this species to adapt to specific thermal habitats and raises the question of the persistence of these populations in the context of rapid climate change.

Tempo and mode in the replacement of trilobite evolutionary faunas from the Cordillera Oriental basin (Northwestern Argentina)

Major ecological transitions among evolutionary faunas are matters of continual debate. Our study analyses the timing and mode of replacement of Ibex I and II Trilobite Evolutionary Faunas (TEF) in Lower Ordovician successions of northwestern Argentina, with special emphasis on olenids and asaphids as key groups of the Ibex I and Ibex II faunas, respectively. We explore richness by using the sample rarefaction method, and occupancy based on a presence–absence dataset. The late Tremadocian 2 (Tr2) represents an inflexion point in richness and occupancy trajectories of asaphids and olenids. While olenids diminish their generic richness through time, asaphids became the richest family since the Tr3 predating the global trend recognized for the expansion of the Ibex II Fauna. Asaphids gained diversity at the expense of other trilobites as well, their rise in diversity lags behind the increase in occupancy suggesting a displacement scenario as the probable mode of replacement between the Ibex I and II TEFs. Apparently, the processes of replacement variate among regions across the globe, configuring a complex global mosaic of regional patterns.

Potential fields modeling of the Serdán Oriental basin, Eastern Mexico

In the eastern portion of the Trans-Mexican Neovolcanic Belt a group maars, rhyolitic domes, and cinder cones are scattered within the Oriental-Serdán basin. They are flanked by large polygenetic volcanoes. We use aeromagnetic and gravimetric fields to infer and model the main anomalies in the region, with the objective of identifying and characterizing the sub-surface sources of the volcanic activity. A large, positive magnetic anomaly overlaps the principal area of volcanic activity; it coincides with the main, positive gravimetric anomaly in the area. Both 2-D and 3-D gravity, as well as magnetic models confirm the existence of a large, dense, and magnetized intrusion body nearly reaching the surface, inferred to be the source of the observed anomalies. The intrusion is flanked to the south by rhyolitic domes. Three independently modeled cross-sections coincide in correlating the presence of maars with upward projections of the main intrusion; these projections we interpret as diatreme-type structures, although the modeling scale does not allow for individual identifications. The conduit that supplied magma for the emplacement of the rhyolitic domes of Las Derrumbadas is also identified to depths of four kilometers. A gravity inversion shows in 3-D space the density distribution at various density ranges.

Flea diversity and prevalence on arid-adapted rodents in the Oriental Basin, Mexico

Inventorying biodiversity is basic for conservation and natural resources management because constant loss of natural areas increases the need for fast biodiversity inventories. Desert flea diversity and associations are not well known in Mexican deserts, especially in the Oriental Basin (OB). Rodents were trapped in the Oriental Basin through June 2007, 2009, and 2010, and July 2008, in 10 localities. A total of 144 rodents belonging to 10 species were trapped, of which 133 were parasitized by 350 fleas belonging to 18 species. Peromyscus difficilis had the highest parasite richness with 9 species, followed by P. maniculatus with 8. The most abundant fleas in the OB were Polygenis vazquezi, Plusaetis parus, Meringis altipecten, and Plusaetis mathesoni. Seven species were found representing new records for 3 states.

From local adaptation to ecological speciation in copepod populations from neighboring lakes.

Continental copepods have been derived from several independent invasive events from the sea, but the subsequent evolutionary processes that account for the current diversity in lacustrine environments are virtually unknown. Salinity is highly variable among lakes and constitutes a source of divergent selection driving potential reproductive isolation. We studied four populations of the calanoid copepod Leptodiaptomus cf. sicilis inhabiting four neighboring lakes with a common history (since the Late Pleistocene) located in the Oriental Basin, Mexico; one lake is shallow and varies in salinity periodically (1.4–10 g L-1), while three are deep and permanent, with constant salinity (0.5, 1.1 and 6.5 g L-1, respectively). We hypothesized that (1) these populations belong to a different species than L. sicilis sensu stricto and (2) are experiencing ecologically based divergence due to salinity differences. We assessed morphological and molecular (mtDNA) COI variation, as well as fitness differences and tests of reproductive isolation. Although relationships of the Mexican populations with L. sicilis s.s. could not be elucidated, we identified a clear pattern of divergent selection driven by salinity conditions. The four populations can still be considered a single biological species (sexual recognition and hybridization are still possible in laboratory conditions), but they have diverged into at least three different phenotypes: two locally adapted, specialized in the lakes of constant salinity (saline vs. freshwater), and an intermediate generalist phenotype inhabiting the temporary lake with fluctuating salinity. The specialized phenotypes are poorly suited as migrants, so prezygotic isolation due to immigrant inviability is highly probable. This implication was supported by molecular evidence that showed restricted gene flow, persistence of founder events, and a pattern of allopatric fragmentation. This study showed how ecologically based divergent selection may explain diversification patterns in lacustrine copepods.

Análisis demográfico de una especie en estado crítico de conservación: la ardilla de Perote

Introduction: The density and structure of populations are basic demographic parameters to calculate for species with a conservation concern. The endemic Perote ground squirrel (Xerospermophilus perotensis) is distributed in the Oriental Basin, in the states of Puebla, Veracruz and Tlaxcala (Mexico). At present, this squirrel is facing serious conservation problems because their habitat has been drastically reduced and transformed, mainly by the conversion to agricultural lands, causing that it only persist in small and isolated populations. The International Union for Conservation of Nature and the Mexican government has classified this species as endangered and threatened respectively. Inasmuch as the species has a restricted distribution, small population and reduced habitat, our aim was to obtain the basic population parameters such as density and population structure. Methods: From years 2010 to 2011 we captured, marked, and recaptured individuals of X. perotensis to determine the age (juveniles and adults), weight, sex ratio and reproductive status (scrotal testes in males or pregnancy and lactation signs in females) in three sites in the Perote Valley, Veracruz, Mexico. The plant associations were the main difference among these sites. All samplings were carried out every two months just including the activity period of the squirrel (April-October). Results: The population parameters evaluated showed similar values at the three study sites (Figure 1). The densities were higher in April-June (breeding season) with 24 ind/ha and lowest in October (beginning hibernation) with 2 ind/ha. Adults predominated in all sites (Figure 2). Juveniles were more abundant in August. The highest number of individuals with reproductive characters (scrotal testes, pregnancy or lactation signs) was found in June (Figure 3). Densities were higher in April-June (breeding season) with 24 ind/ha and lowest in October (beginning hibernation) with 5 ind/ha. The number of juveniles and adults showed significant differences ( P = 0.002). Discussion and Conclusions: The results indicate that the population of the Perote ground squirrel is declining and shows low population recruitment. Also their habitat is being transformed rapidly and offers few opportunities for the development of the species. We suggest that the species should be categorized as an endangered species instead of threatened in Mexico. Also, farmers could allow the establishment of animals when they do not use the land, this action can stimulate the population growth.

Dissolved uranium, radium and radon evolution in the Continental Intercalaire aquifer, Algeria and Tunisia

Natural, dissolved 238U-series radionuclides (U, 226Ra, 222Rn) and activity ratios (A.R.s: 234U/238U; 228Ra/226Ra) in Continental Intercalaire (CI) groundwaters and limited samples from the overlying Complexe Terminal (CT) aquifers of Algeria and Tunisia are discussed alongside core measurements for U/Th (and K) in the contexts of radiological water quality, geochemical controls in the aquifer, and water residence times. A redox barrier is characterised downgradient in the Algerian CI for which a trend of increasing 234U/238U A.R.s with decreasing U-contents due to recoil-dominated 234U solution under reducing conditions allows residence time modelling ∼500 ka for the highest enhanced A.R. = 3.17. Geochemical modelling therefore identifies waters towards the centre of the Grand Erg Oriental basin as palaeowaters in line with reported 14C and 36Cl ages. A similar 234U/238U trend is evidenced in a few of the Tunisian CI waters. The paleoage status of these waters is affirmed by both noble gas recharge temperatures and simple modelling of dissolved, radiogenic 4He-contents both for sampled Algerian and Tunisian CI and CT waters. For the regions studied these waters therefore should be regarded as “fossil” waters and treated effectively as a non-renewable resource.

Present and future potential distribution of the endemic Perote ground squirrel (Xerospermophilus perotensis) under different climate change scenarios

The current distribution of the endemic Perote ground squirrel ( Xerospermophilus perotensis ) and its future potential response to climate change have not been addressed. Thus, in this work, we focus on both aspects of this species by means of ecological niche modeling, using different general circulation models and Intergovernmen- tal Panel on Climate Change emission scenarios. Because the species ' life history includes a hibernation period, we performed two different sets of analysis: one consid- ering the whole annual cycle and another considering only the species ' active season. According to our results, the current potential distribution of X. perotensis extends further out of the Oriental Basin, to which the species is endemic. Future projections vary among different climatic scenarios and data sets used in the modeling process, but virtually all of them project a substantial encroach- ment of the species ' potential distribution area by 2050. Our models suggest that, compared with species that are active throughout the year, X. perotensis , being a seasonal species, could be affected by climate change, increasing the risk of extinction. This may pose a serious threat to the Perote ground squirrel ' s persistence throughout the following decades.

Spatiotemporal population genetics of the endangered Perote ground squirrel (Xerospermophilus perotensis) in a fragmented landscape

Abstract The Perote ground squirrel (Xerospermophilus perotensis) is endemic to Mexico and is currently at risk of extinction. Its original range comprised 5,250 km2 in an area known as the Oriental Basin, between the states of Puebla and Veracruz. By the end of the 20th century, however, extensive agricultural practices, overgrazing, and urbanization had already restricted suitable habitat for this species to only 16 localities. Temporal changes in genetic diversity and structure in this species were assessed from 34 museum specimens from 5 historical populations (1990–1992) and 44 individuals from 3 current populations (2007) using the mitochondrial (mtDNA) control region and 5 nuclear microsatellites. We observed a general trend (significant in some cases and nonsignificant in others) suggesting a decrease in genetic diversity within populations and an increase in genetic structure between them in recent years for both sets of markers. A Bayesian skyline reconstruction for the mtDNA sequences was congr...

Distribution, Taxonomy, and Conservation Status of the Perote Mouse Peromyscus bullatus (Rodentia: Muridae) in México

The Perote deer mouse Peromyscus bullatus is a rare species known only from a few specimens. It is endemic to the plains surrounding the Oriental Basin in the states of Veracruz and Puebla, Mexico, in the area where the Sierra Madre Oriental and the eastern end of the Transverse Volcanic Range merge. In past studies, a small area within the basin provided the only known habitat. During two recent surveys adjacent to this area, in habitats that matched the area in the state of Puebla where P. bullatus was previously found, we made new surveys. This mouse is differentiable from other species of the genus, mainly in the large of the auditory and the size of the ear. Intrinsic factors are highly discriminating in choice of habitat, low densities, and has restricted distribution, as well as the extrinsic factor of habitat deterioration, indicates a serious conservation problem.

The major features of the crustal structure in north-eastern Venezuela from deep wide-angle seismic observations and gravity modelling

Venezuela is located on the plate boundary zone between the South American continent and the Caribbean plate. A relative movement of 2 cm/year is accommodated by a system of strike–slip faults running from the Andes to the Gulf of Paria. The Interior Range, a moderate-height mountain range, separates the Oriental Basin from the Caribbean. To the south, predominantly Precambrian rocks are outcropping in the Guayana Shield south of the Orinoco River. Results of deep wide-angle seismic measurements for the region were obtained during field campaigns in 1998 (ECOGUAY) for the Guayana Shield and in 2001 (ECCO) for the Oriental Basin. The total crustal thickness decreases from 45 km beneath the Guayana Shield, to 39 km at the Orinoco River, and 36 km close to El Tigre, in the center of the Oriental Basin. The average crustal velocity decreases in the same sense from 6.5 to 5.95 km/s. Detailed information was obtained on the velocity distribution within the Oriental Basin. Velocities are as low as 2.2 km/s for the uppermost 2 km, 4.5 km/s down to 4 km in depth, and a maximum depth of 13 km was derived for material with seismic velocities up to 5.9 km/s, interpreted as the base of the sedimentary basin. A gravimetric model confirms the structures derived from the seismic data. Discrete increases in sedimentary thickness along the basin may be associated to extension processes during the passive margin phase in the Cretaceous, or during earlier extension phases.

Caecidotea williamsi (Crustacea: Isopoda: Asellidae), a new species from a saline crater-lake in the eastern Mexican Plateau

A new species of Caecidotea, an aquatic isopod crustacean is described from Alchichica crater-lake in the state of Puebla, Oriental Basin, central Mexico. This is the first report of an epigean asellid isopod, with cryptic behavior inhabiting inland saline waters in America. Comparisons made with other co-occurring asellid species in the region show that the species Caecidotea pasquinii differs from the new species in lacking eyes, having different features on the male endopod of pleopod 2, a shorter pereiopod 6, and having elongated uropods. The epigean species Caecidotea communis differs from the new species in having pleopod 4 of the A type pattern of Lewis & Bowman (1981) and 5–8 retinacula on pleopod 1 sympod.

The crustal structure of the Guayana Shield, Venezuela, from seismic refraction and gravity data

We present results from a seismic refraction experiment on the northern margin of the Guayana Shield performed during June 1998, along nine profiles of up to 320 km length, using the daily blasts of the Cerro Bolı́var mines as energy source, as well as from gravimetric measurements. Clear Moho arrivals can be observed on the main E–W profile on the shield, whereas the profiles entering the Oriental Basin to the north are more noisy. The crustal thickness of the shield is unusually high with up to 46 km on the Archean segment in the west and 43 km on the Proterozoic segment in the east. A 20 km thick upper crust with P-wave velocities between 6.0 and 6.3 km/s can be separated from a lower crust with velocities ranging from 6.5 to 7.2 km/s. A lower crustal low velocity zone with a velocity reduction to 6.3 km/s is observed between 25 and 25 km depth. The average crustal velocity is 6.5 km/s. The changes in the Bouguer Anomaly, positive (30 mGal) in the west and negative (−20 mGal) in the east, cannot be explained by the observed seismic crustal features alone. Lateral variations in the crust or in the upper mantle must be responsible for these observations.

Regional gravity analysis of the crustal structure of Tunisia

Gravity data were integrated with seismic refraction/reflection data, well data and geological investigations to determine a general crustal structure of Tunisia. The gravity data analysis included the construction of a complete Bouguer gravity anomaly map, residual gravity anomaly maps, horizontal gravity gradient maps and a 2.5-D gravity model. Residual gravity anomaly maps illustrate crustal anomalies associated with various structural domains within Tunisia including the Sahel Block, Saharian Flexure, Erg Oriental Basin, Algerian Anticlinorium, Gafsa Trough, Tunisian Trough, Kasserine Platform and the Tell Mountains. Gravity anomalies associated with these features are interpreted to be caused either by thickening or thinning of Palæozoic and younger sediments or by crustal thinning. Analysis of the residual gravity anomaly and horizontal gravity gradient maps also determined a number of anomalies that may be associated with previously unknown structures. A north-south trending gravity model in general indicated similar subsurface bodies as a coincident seismic model. However, thinner Mesozoic sediments within the Tunisian Trough, thinner Palæozoic sediments in the Gafsa Trough, and a greater offset on the Saharian Flexure were required by the gravity data. Additionally, basement uplifts under the Kasserine Platform and Gafsa Trough, not imaged by seismic data, were required by the gravity data. The gravity model revealed two previously unknown basins north and south of the Algerian Anticlinorium (5 km), while the Erg Oriental Basin is composed of at least two sub-basins, each with a depth of 5 km.

Threats to the saline lakes of the Oriental Basin, Mexico, by human activities

(1998). Threats to the saline lakes of the Oriental Basin, Mexico, by human activities. SIL Proceedings, 1922-2010: Vol. 26, No. 3, pp. 1383-1386.