El Vado Research Articles

Historic-archaeological research in the conservation of the building heritage of Cuenca (Ecuador): example of analysis Rodríguez house, El Vado neighborhood

Historic-archaeological research in the conservation of the building heritage of Cuenca (Ecuador): example of analysis Rodríguez house, El Vado neighborhood

Managed spring runoff to improve nursery floodplain habitat for endangered Rio Grande silvery minnow

AbstractWater managers in New Mexico, USA, stored water in El Vado Reservoir and coordinated releases into the Chama River that augmented the runoff of the Rio Grande, resulting in a discharge >1,500 ft3/s (42.5 m3/s) for 35 days (May 17 to June 20, 2016) at Albuquerque. The managed runoff inundated over 400 ha of previously restored floodplains in the Middle Rio Grande, thereby providing spawning and nursery habitat for the endangered Rio Grande silvery minnow (Hybognathus amarus, RGSM). Spawning began April 9 at annual cumulative degree‐days of 717, during daily increases in discharge of 200–300 ft3/s (5.7–8.5 m3/s), and hatch dates were normally distributed over 53 days (April 11 to June 3). RGSM were 73% of larvae collected in six restored floodplain sites and found in shallow water (mean = 19.6 cm), low velocity (mean = 3.9 cm/s), near vegetative cover, and with 75% within 1 m of the water's edge. Declining proportions of early to late larval phases and a near absence of juveniles indicate a gradual departure from floodplains as postflexion mesolarvae and metalarvae 14–22 days post hatch (dph), with most leaving by the juvenile stage 40 dph. The annual RGSM October census showed an increase of 0.16 to 7.20 fish/100 m2 from 2015 to 2016, indicating that the managed runoff resulted in a positive population response. This study showed that constructing floodplains and managing river and reservoir operations to inundate those floodplains during and after RGSM spawning can provide nursery habitat that improves reproductive success and recruitment.

Low Net: Gross Reservoirs of the Transgressive Shelf Systems in the Upper Mancos Shale, El Vado Sandstone, San Juan Basin, New Mexico

The El Vado (EV) Sandstone Member (upper Coniacian) of the Mancos Shale has been considered both a conventional and unconventional hydrocarbon resource target (Ridgley, 2001) in the San Juan Basin (SJB) of northwestern New Mexico. Sandstones of the EV were deposited on the marine intracontinental shelf along the west margin of the Cretaceous Seaway. The EV is part of a transgressive-regressive wedge of rock that overlies a large, older transgressive wedge that contains the Tocito Sandstone. The EV is examined in outcrops in the northeast and the southeast parts of the SJB. In northern outcrops, the EV consists of five parasequences of interbedded sands and shales of similar thickness (∼4 m each) separated by marine-shale units that become progressively sandier upward. To the south, the EV Sandstone transitions from a shelf-deposited into a lower-shoreface sandstone. Well logs and core are used to map the subsurface distribution of the EV Sandstone in the SJB. It is reflected in logs as a thick (∼36.6 m; 120 ft) interval of low gamma ray and high resistivity, associated with highly laminated sand to silt interbedded with shales. A total of 13 cross sections are correlated and used to construct total-interval isopach and parasequence-scale isopach maps for the EV. Regional net-sand and net:gross maps, determined from 104 digitized well logs, highlight the regional distribution of sand in the formation. Thicks are oriented north to south and show compensated deposition suggesting that individual parasequences are not in communication across the basin, but opportunity exists to penetrate stacked parasequences with single vertical wells.

Developmental Defects in the Spine: Initial Findings in Archaeological Cases from Córdoba Highlands (Argentina)

AbstractCongenital disorders are pathologies rarely found in archaeological cases. In recent years, however, there has been an increase in the number of reported cases, and a growing interest in understanding their development and implication as genetic markers within certain collections. In the central region of Argentina, researchers have begun to focus on issues related to the health of prehispanic populations from a bioarchaeological perspective. Between 1999 and 2012 our research group recovered, by rescue archaeological activities, a total number of 62 individuals from different archaeological sites in the province of Córdoba, from which only three individuals with pathologies classified as congenital were recorded (4.83%). Radiocarbon and contextual information sets these individuals in the late Holocene (2156 ± 86 and 920 ± 20 14C years BP). Hence, this work aims at presenting two pathological conditions deriving from congenital developmental abnormalities that arise during the first three months of pregnancy: (a) Klippel–Feil syndrome (type II) which was suffered by the individuals from the sites of Guasmara and El Vado, and (b) central sagittal fissure of the vertebral body or ‘butterfly vertebra’ as in the case of one individual from La Calera. We also analyse other lesions in these skeletons that may be associated with the conditions mentioned above, and we provide a thorough interpretation from an osteobiographical perspective. Copyright © 2015 John Wiley & Sons, Ltd.

Tributary confluences and discontinuities in channel form and sediment texture: Rio Chama, NM

ABSTRACTNumerous morphological changes can occur where two channels of distinct sediment and flow regimes meet, including abrupt shifts in channel slope, cross‐sectional area, planform style, and bed sediment size along the receiving channel. Along the Rio Chama between El Vado and Abiquiu Dams, northern New Mexico, arroyo tributaries intermittently deliver sediment from erodible sandstone and shale canyon walls to the mainstem channel. Much of the tributary activity occurs in flash floods and debris flows during summer thunderstorms, which often load the channel with sand and deposit coarser material at the mainstem confluence. In contrast, mainstem channel flow is dominated by snowmelt runoff. To examine tributary controls, we systematically collected cross‐section elevation and bed sediment data upstream and downstream of 26 tributary confluences along a 17 km reach. Data from 203 cross‐sections were used to build a one‐dimensional hydraulic model for comparing estimated channel parameters at bankfull and low‐flow conditions at these sites As compared to intermediate reaches, confluences primarily impact gradient and bed sediment size, reducing both parameters upstream of confluences and increasing them downstream. Cross‐section area is also slightly elevated above tributary confluences and reduced below. Major shifts in slope and bed sediment size at confluences appear to drive variations in sediment entrainment and transport capacity and the relative storage of sand along the channel bed. The data were analyzed and compared to models of channel organization based on lateral inputs, such as the Network Variance Model and the Sediment Link Concept. At a larger scale, hillslope − channel coupling increases in the downstream third of the study reach, where the canyon narrows, resulting in steeper slopes and more continuous coarse bed material along the mainstem, and thus, limiting the contrast with tributary confluences. However, channel form and sediment characteristics are highly variable along the study reach, reflecting variations in the size and volume of sediment inputs related to the surface geology in tributary watersheds, morphology of the Rio Chama at the junction (i.e. bends, confinement), and the relative magnitude and location of past depositional events. Copyright © 2014 John Wiley & Sons, Ltd.

Factors affecting the structure and maintenance of phytoplankton functional groups in a nutrient rich lowland river

The phytoplankton structure along the mainstem of the Lower Salado River (Argentina) was analysed in relation to the environmental variables and the influence exerted by the inflowing waters from the Paraná River (via El Vado Stream) and an adjacent floodplain shallow lake, between December 2003 and August 2004. Phytoplankton driving forces were explored using a functional approach. Small phytoplanktonic organisms with high metabolism and well adapted to live in mixed environments dominated (functional groups C , D , X1 , X2 ), but the organic enrichment and slow flow also facilitated the thriving of Cyanobacteria ( L O and minor contributions of H1 , K , S N ) and large Euglenophyta ( W1 , W2 ) inflowing from adjacent sites. The longitudinal and temporal changes in the phytoplankton structure depended on the prevailing hydrological conditions. Three scenarios were identified as regards the complex hydrological interactions of the Paraná and Salado Rivers: (i) the hydrological isolation period (low waters) when the Salado had a homogeneous longitudinal pattern and high phytoplankton development; (ii) the period of hydrological interactions with Salado River influence (high waters) when the homogeneous longitudinal pattern extended to the stream, and algal growth in the river was counteracted by dilution and enhancement of water velocity, and (iii) the period of hydrological interactions with Paraná System influence characterised by a longitudinal discontinuity with lower phytoplankton concentrations downriver the Paraná inflow due to dilution. There were no evidences that the lake contributed with algal biomass to the downriver plankton during the study period.

High resolution record of environmental changes constrained by volcanic ashes : Western Interior Basin, Cenomanian-Turonian stage boundary (USA)

Abstract Five altered volcanic-ash beds have been correlated near the Cenomanian-Turonian stage boundary through much of the Western Interior Basin. These instantaneous events constitute independent chronostratigraphic marker-beds enabling the synchroneity of lithological, biological or geochemical records to be tested. In this way, the Greenhorn Sea is a unique place where the potentiality of this high-resolution stratigraphic tool is illustrated. The Cenomanian-Turonian interval is the ideal period for this sort of study because major oceanic changes, including the global expansion of the oxygen minimum zone, are recognised across OAE2 event, involving the disappearance of Rotalipora, complex keeled foraminifera which previously occupied deep oceanic waters. Biostratigraphic data coupled with bentonite correlation, in several sections of Colorado, show the diachronism of the occurrences of R. cushmani and H. helvetica. Consequently, the extension of the W. archaeocretacea partial range zone is extremely variable at the regional scale. Thus, this association has a low temporal value. Planktonic foraminiferal analyses also reveal an A. multiloculata event in the M. mosbyense zone. During tens of thousands of years, this species, plentiful in the Western Interior Basin, multiplies and prevails on Rotalipora before a gradual decline. Rotalipora gave rise to Anaticinella by the atrophy of its keel. Thus, Anaticinella may stay in shallower habitats and avoid the expansion of the oxygen minimum zone. However, even if this adaptation allowed a return to the surface water, this selective advantage would not be enough for Anaticinella to survive the ecologically drastic modifications. Extinction of Anaticinella and its ancestor Rotalipora occurred contemporaneously. Carbon stable isotope analyses show that main paleoceanographic events have occurred at Pueblo during the Cenomanian-Turonian stage boundary. The initial rapid increase and first peak of δ13C indicate the first anoxic event (event 1) before a decrease in values and a main manganese enrichment which are the evidence for a well-oxygenated environment (event 2). This assumption is supported by the occurrence of an abundant and diversified benthic community at the same interval. The second increase in δ13C proxies signs the rise of anoxia (event 3). The temporal distribution of these events with the bentonite marker beds and the ammonite biostratigraphy attest to the synchroneity of events 2 and 3 over 600 km between the Pueblo and Lohali Point sections. The absence of event 1 at Lohali Point in the S. gracile zone implies the existence of a hiatus. Thus, thanks to the five bentonite marker beds, extending from the S. gracile to the M. nodosoides ammonite zone over 2 Ma, we have not only achieved precise regional correlation but, dealing with facies variations, our observations also indicate gaps in the sedimentary record. Thus, in detail, some thin levels expressed in Pueblo (reference section) cannot be correlated in any other eastern sections. Furthermore, supposed continuous sections may contain important hiatuses. An example is given at El Vado (New Mexico) where two bentonite marker beds are missing. In spite of the lack of significant planktonic foraminifera, the indications provided by bentonite geometries and by nannofossils reveal the existence of a hiatus of at least 850 kyr. It could be explained by the location of the area along the trend of a tectonic forebulge linked to the Sevier orogeny. This bathymetric high had great consequences on the currents flows in this large interior sea where tethysian and boreal water masses competed.

Reservoir induced seismicity near Heron and El Vado reservoirs, northern New Mexico

Reservoir induced seismicity near Heron and El Vado reservoirs, northern New Mexico

Reservoir Induced Seismicity Near Heron and El Vado Reservoirs, Northern New Mexico

Spatial, temporal and magnitude-frequency relationships for earthquakes occurring between 1976 and 1984 near Heron and El Vado reservoirs in northern New Mexico are examined for evidence of reservoir-induced seismicity (RIS). Most of the 264 located shocks, including those with the highest magnitude (maximum ML = 2.7; mb = 3.8), occurred in 1982 when Heron reservoir reached its maximum capacity of approximately 0.5 km3 and an impoundment depth of 66 m. Between 1976 and 1984, earthquake swarms followed, or were enhanced by, reservoir filling in three out of four cases where filling resulted in new maximum water volumes for Heron reservoir. Shocks generally cluster between the reservoirs in a region of north-south block faulting. A cumulative earthquake frequency versus magnitude plot for Heron-El Vado produced a b-value of 0.92 ± 0.03 (1 SD) which is slightly higher than other b-values for northern New Mexico and is consistent with b-values for reservoir induced shocks in other areas. The spatial and temporal distribution of these events, along with their b-value, suggests most of them have been triggered by reservoir loading. Practical ramifications of this work are that RIS can occur in reservoirs with impoundment depths of less than 100 m and RIS may occur if other dams are located along the historically seismic Archuleta anticline on the eastern margin of the San Juan basin.

Short term sedimentation response in lakes in western United States as measured by automated sampling1

Sediment traps that can greatly amplify the rate of sedimentation and automatically time the depositional process were set out in El Vado Lake and Morgan Lake (New Mexico), Lake Powell (Utah), and Pyramid Lake (Nevada). In El Vado and Morgan lakes, sediment fluctuations on the scale of days were responsive to local weather factors, with the deposition rate in Morgan Lake greater near the bottom of the water column than near the top. Sedimentation in El Vado and Pyramid lakes appeared to have some diurnal control. Sedimentation in Pyramid Lake and Lake Powell, the two lakes fed by large rivers, was strongly influenced by river discharge and showed lag effects proportional to the distance of sediment transport.