Small scale oxygen isotope variations in ultradeep (>300 km) and transition zone xenoliths

2019 ◽  
Keyword(s):  
Oxygen Isotope ◽  
Transition Zone ◽  
Small Scale

Small-scale mineralogical heterogeneity from variations in phase assemblages in the transition zone and D″ layer predicted by convection modelling

2011 ◽  
Vol 22 (2) ◽  
pp. 160-168
Author(s):  
Arie P. van den Berg ◽  
David A. Yuen ◽  
Michael H. G. Jacobs ◽  
Maarten V. de Hoop
Keyword(s):  
Transition Zone ◽  
Small Scale

scholarly journals Microstructure observations during the spring 2011 STRATIPHYT-II cruise in the northeast Atlantic

Ocean Science ◽  
2012 ◽  
Vol 8 (6) ◽  
pp. 945-957 ◽  
Author(s):  
E. Jurado ◽  
H. A. Dijkstra ◽  
H. J. van der Woerd
Keyword(s):  
Transition Zone ◽  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Small Scale ◽  
Data Set ◽  
Northeast Atlantic ◽  
Eddy Diffusivities ◽  
Scale Temperature ◽  
Spatial Coverage ◽  
Layer Increase

Abstract. Small-scale temperature and conductivity variations have been measured in the upper 100 m of the northeast Atlantic during the STRATIPHYT-II cruise (Las Palmas–Reykjavik, 6 April–3 May 2011). The measurements were done at midday and comprised 2 to 15 vertical profiles at each station. The derived turbulent quantities show a transition between weakly-stratified (mixed layer depth, MLD, <100) and well-mixed waters (MLD > 100), which was centered at about 48° N. The temperature eddy diffusivities, KT, range from 10−5 to 100 m2 s−1 in the weakly-stratified stations, and range from 3 × 10−4 to 2 × 100 m2 s−1 in the well-mixed stations. The turbulent kinetic energy dissipation rates, ε, range from 3 × 10−8 to 2 × 10−6 m2 s−3 south of the transition zone, and from 10−7 to 10−5 m2 s−3 north of the transition zone. The station-averaged KT values throughout the mixed layer increase exponentially with the wind speed. The station-averaged ε values throughout the mixed layer scale with the wind stress similarity variable with a scaling factor of about 1.8 in the wind-dominated stations (ε &amp;approx; 1.8 u&amp;star;3/(−κz)). The values of KT and ε are on average 10 times higher compared to the values measured at the same stations in July 2009. The results presented here constitute a unique data set giving large spatial coverage of upper ocean spring turbulence quantities.

scholarly journals The spatial distribution of Aedes aegypti and Aedes albopictus in a transition zone, Rio de Janeiro, Brazil

2009 ◽  
Vol 25 (6) ◽  
pp. 1203-1214 ◽  
Author(s):  
Nildimar Alves Honório ◽  
Márcia Gonçalves Castro ◽  
Fábio Saito Monteiro de Barros ◽  
Mônica de Avelar Figueiredo Mafra Magalhães ◽  
Paulo Chagastelles Sabroza
Keyword(s):  
Aedes Aegypti ◽  
Transition Zone ◽  
Rio De Janeiro ◽  
Urban Forest ◽  
Viral Disease ◽  
Vegetation Coverage ◽  
Small Scale ◽  
Wet Season ◽  
Forested Areas ◽  
Vector Borne

Dengue fever has become the most important vector-borne viral disease in Brazil. Human facilitated transport of desiccation-resistant eggs has led to its two most important vectors, Aedes aegypti and Ae. albopictus, becoming widespread. In this paper, we report seasonal and spatial variation in larval abundances of Ae. aegypti and Ae. albopictus across a small-scale transition zone between an urban area and an urban wooded/forested area within Rio de Janeiro, Brazil. We installed 400 ovitraps across 10 sites with different human population densities and vegetation coverage. Eggs and larvae were collected for three weeks during the wet and dry seasons of 2002 and 2003. Ae. albopictus was predominantly found in the forested areas of the study site whereas in the urbanized area Ae. aegypti was more abundant. Both species peaked during the wet season. This distribution pattern, which may reflect adult flight range, may favor the co-occurrence of larvae of these species in a small-scale urban/urban forest transition zone.

Modelling nitrogen and oxygen isotope fractionation during denitrification in a lacustrine redox-transition zone

2003 ◽  
Vol 67 (14) ◽  
pp. 2529-2542 ◽  
Author(s):  
Moritz F. Lehmann ◽  
Peter Reichert ◽  
Stefano M. Bernasconi ◽  
Alberto Barbieri ◽  
Judith A. McKenzie
Keyword(s):  
Oxygen Isotope ◽  
Transition Zone ◽  
Isotope Fractionation ◽  
Oxygen Isotope Fractionation ◽  
Redox Transition

A COMPARATIVE ANALYSIS OF HISTORICAL FLOOD EVENTS (POST-1990) IN THE TREBEŞ-NEGEL REPRESENTATIVE BASIN FOR EASTERN CARPATHIANS AND SUBCARPATHIANS TRANSITION ZONE

2021 ◽  
Vol 16 (1) ◽  
pp. 31-46
Author(s):  
Larisa Elena PAVELUC ◽  
◽  
Alin MIHU-PINTILIE ◽  
Elena HUŢANU ◽  
Adrian GROZAVU
Keyword(s):  
Comparative Analysis ◽  
Transition Zone ◽  
Small Scale ◽  
Flood Events ◽  
European Network ◽  
Entire Region ◽  
Eastern Carpathians ◽  
Hydrological Hazards ◽  
Mitigation Effort ◽  
Heavy Rains

The European Network of Experimental and Representative Basins (ENERB) is the results of several experimental projects concerning the hydrological forecasting and flood mitigation effort which have been implemented within states member of European Union. In Romania, the hydrometric activity for ENERB it is currently composed of 14 representative basins (RB) of which the Trebeş-Negel (184 km2) was selected as RB for Eastern Carpathian and Subcarpathian transition zone. Located in one of the most affected territories by hydrological hazards, the Trebeş-Negel RB reacted as a small-scale flood sensor for the entire region. Using the well-documented discharge and pluviometric database collected at five gauge stations within the study area, we develop the first comparative analysis of historical flood events that occurred in the Trebeş-Negel RB post-1990. Five exceptional floods were selected: flood events from July 2 to July 8, 1991; flood events from June 16 to June 22, 1992; flood events from July 11 to July 14, 2005; flood events from July 26 to July 31, 2010; and flood events from June 28 to July 1, 2018. All flood events envisaged were caused by heavy rains, when significant amounts of precipitations were recorded which sometimes exceeded 100 mm/day.

scholarly journals Permafrost distribution and conditions at the headwalls of two receding glaciers (Schladminger and Hallstadt glaciers) in the Dachstein Massif, Northern Calcareous Alps, Austria

2019 ◽  
Author(s):  
Matthias Rode ◽  
Harald Schnepfleitner ◽  
Oliver Sass ◽  
Andreas Kellerer-Pirklbauer ◽  
Christoph Gitschthaler
Keyword(s):  
Transition Zone ◽  
Slope Failure ◽  
Ground Surface ◽  
Northern Calcareous Alps ◽  
Small Scale ◽  
European Alps ◽  
Glacier Surface ◽  
Near Surface ◽  
Northern Calcareous ◽  
Discontinuous Permafrost

Abstract. Permafrost distribution in rockwalls surrounding receding glaciers is an important factor for rock slope failure and rockwall retreat. The Northern Calcareous Alps of the Eastern European Alps form a geological and climatological transition zone between the Alpine Foreland and the Central Alps. Some of highest summits of this area are located in the Dachstein Massif (47°28'32'' N, 13°36'23'' E) in Austria reaching up to 2995 m a.s.l. Occurrence, thickness and thermal regime of permafrost at this partly glaciated mountain massif are scarcely known and related knowledge is primarily based on regional modeling approaches. We applied a multi method approach with continuous ground surface and near-surface temperature monitoring, measurement of bottom temperature of the winter snow cover, electrical resistivity tomography/ERT, airborne photogrammetry, topographic maps, visual observations and field mapping for permafrost assessment. Our research focused on steep rockwalls consisting of massive limestone above several receding glaciers exposed to different slope aspects at elevations between c.2600–2700 m a.s.l. We aimed to quantify distribution and conditions of bedrock permafrost particularly at the transition zone between the present glacier surface and the adjacent rockwalls. Low ground temperature data suggest that permafrost is mainly found at cold, north exposed rockwalls. At southeast exposed rockwalls permafrost is only expected in very favourable cold conditions at shadowed higher elevations (2700 m a.s.l.). ERT measurements reveal high resistivities (> 30.000 ohm.m) at ≥ 1.5 m depth at north-exposed slopes (highest measured resistivity values > 100 kohm.m). Based on laboratory studies and additional measurements with small scale ERT, these values indicate permafrost existence. Such permafrost bodies were found in the rockwalls at all measurement sites independent of investigated slope orientation. ERT data indicate large permafrost bodies at north exposed sites whereas discontinuous permafrost bodies prevail at northwest and northeast facing rockwalls. In summary, permafrost distribution and conditions around the headwalls of the glaciers of the Dachstein Massif is primarily restricted to the north exposed sector, whereas at the south exposed sector permafrost is restricted to the summit region.

scholarly journals Combining Models of Environment, Behavior, and Physiology to Predict Tissue Hydrogen and Oxygen Isotope Variance Among Individual Terrestrial Animals

2020 ◽  
Vol 8 ◽  
Author(s):  
Sarah Magozzi ◽  
Hannah B. Vander Zanden ◽  
Michael B. Wunder ◽  
Clive N. Trueman ◽  
Kailee Pinney ◽  
...  
Keyword(s):  
Oxygen Isotope ◽  
Isotope Ratios ◽  
Body Water ◽  
Mechanistic Modeling ◽  
Small Scale ◽  
Modeling Framework ◽  
Underlying Assumption ◽  
Isotopic Variation ◽  
Model Predictions ◽  
Hydrogen And Oxygen Isotope

Variations in stable hydrogen and oxygen isotope ratios in terrestrial animal tissues are used to reconstruct origin and movement. An underlying assumption of these applications is that tissues grown at the same site share a similar isotopic signal, representative of the location of their origin. However, large variations in tissue isotopic compositions often exist even among conspecific individuals within local populations, which complicates origin and migration inferences. Field-data and correlation analyses have provided hints about the underlying mechanisms of within-site among-individual isotopic variance, but a theory explaining the causes and magnitude of such variance has not been established. Here we develop a mechanistic modeling framework that provides explicit predictions of the magnitude, patterns, and drivers of isotopic variation among individuals living in a common but environmentally heterogeneous habitat. The model toolbox includes isoscape models of environmental isotopic variability, an agent-based model of behavior and movement, and a physiology-biochemistry model of isotopic incorporation into tissues. We compare model predictions against observed variation in hatch-year individuals of the songbird Spotted Towhee (Pipilo maculatus) in Red Butte Canyon, Utah, and evaluate the ability of the model to reproduce this variation under different sets of assumptions. Only models that account for environmental isotopic variability predict a similar magnitude of isotopic variation as observed. Within the modeling framework, behavioral rules and properties govern how animals nesting in different locations acquire resources from different habitats, and birds nesting in or near riparian habitat preferentially access isotopically lighter resources than those associated with the meadow and slope habitats, which results in more negative body water and tissue isotope values. Riparian nesters also have faster body water turnover and acquire more water from drinking (vs. from food), which exerts a secondary influence on their isotope ratios. Thus, the model predicts that local among-individual isotopic variance is linked first to isotopic heterogeneity in the local habitat, and second to how animals sample this habitat during foraging. Model predictions provide insight into the fundamental mechanisms of small-scale isotopic variance and can be used to predict the utility of isotope-based methods for specific groups or environments in ecological and forensic research.

scholarly journals Facies analysis and sequence stratigraphy of the uppermost Jurassic– Lower Cretaceous Sulaiy Formation in outcrops of central Saudi Arabia

GeoArabia ◽  
2015 ◽  
Vol 20 (4) ◽  
pp. 67-122
Author(s):  
Philipp Wolpert ◽  
Martin Bartenbach ◽  
Peter Suess ◽  
Randolf Rausch ◽  
Thomas Aigner ◽  
...  
Keyword(s):  
Saudi Arabia ◽  
Transition Zone ◽  
Lower Cretaceous ◽  
Large Scale ◽  
Arabian Plate ◽  
Small Scale ◽  
Large Solution ◽  
Medium Scale ◽  
Facies Associations ◽  
Sulaiy Formation

ABSTRACT Uppermost Jurassic–Lower Cretaceous carbonates of the Sulaiy Formation are well exposed at the type locality Dahal Hit, and along the entire natural escarpment near Ar Riyad, the capital of the Kingdom of Saudi Arabia. This study provides a facies and sequence-stratigraphic analysis based on detailed sedimentological and gamma-ray logging of 12 outcrop sections. The sections represent the Sulaiy Formation along a 60 km-long outcrop belt, including the Hith-Sulaiy transition in a large solution cavity named Dahal Hit, situated south of Ar Riyad. The latter section is studied in detail because it is the only locality in Saudi Arabia where the Hith Anhyrite (Hith Formation in this study) to the Sulaiy Formation transition crops out. Ten lithofacies types were identified for the Sulaiy Formation including potential reservoirs such as oolitic cross-bedded grainstones, biostromal boundstones, and bioclast-rich, graded pack-to-grainstones. Lithofacies types are grouped into five facies associations: (1) offshoal, (2) transition zone, foreshoal, (4) shoal margin, and (5) shoal, distributed along a carbonate ramp. Their vertical stacking pattern revealed a systematic hierarchy of cyclicity consisting of small-scale cycles, medium-scale cycle sets and two large-scale sequences for the Sulaiy Formation. Four cycle motifs, with an average thickness of 2–4 m, are present: (1) offshoal to transition zone cycle motif, (2) offshoal to foreshoal cycle motif, (3) transition zone to shoal margin cycle motif, and foreshoal to shoal margin cycle motif. A total of 15 cycle sets, ranging between 8 and 12 m in thickness each, were interpreted. They were correlated, where possible, across the study area. Three types of medium-scale cycle sets are observed: (1) offshoal to shoal cycle set motif, (2) offshoal to foreshoal cycle set motif, and (3) shoal margin to offshoal cycle set motif. The Lower Sulaiy Sequence consists of twelve cycle sets and is interpreted to contain two Arabian Plate maximum flooding surfaces (MFS): (1) Upper Tithonian MFS J110 (147 Ma) in its lowermost part, which is interpreted to be the time-equivalent of the Manifa reservoir in subsurface Arabia. (2) Lower Berriasian MFS K10 (144 Ma) in the seventh-up cycle set. The Upper Sulaiy Sequence is only represented in the Wadi Nisah Section and is believed to be incomplete because the Sulaiy/Yamama Formation boundary was not included in our study. It is presumed to contain Upper Berriasian MFS K20 (141 Ma).

Sign in / Sign up

Export Citation Format

Share Document