Facies and architectural variability of sub-seismic slope-channel fills in prograding clinoforms,Mid-Jurassic Neuquén Basin,Argentina

Most slope-channel outcrop studies have been conducted at continental margin-scale on seismic data. However, in foreland and back-arc deepwater settings, sub-seismic scale slope channels hold equally important information on deepwater sediment delivery, often in hydrocarbon-bearing provinces. One such slope-channel system is examined in Lower Jurassic prograding shelf-margin clinoforms in Bey Malec Estancia, La Jardinera area, southern Neuquén Basin, Argentina. In a 4 km wide, 300 m tall, slightly oblique- to depositional-dip section of Jurassic Los Molles Formation deepwater slope deposits, seven clinoform timelines were identified by isolated slope-channel fills with thicknesses less than 50 m. Sedimentary logs, satellite images, a digital elevation model and drone photogrammetry were used to map variations in downslope channel geometry and infill facies. The slope channels are filled with sediment density flow deposits: poorly sorted conglomeratic debrites, structureless sandy high-density turbidites and well-sorted, fine-grained, graded low-density turbidites. The debrite portion decreases downslope, whereas high- and low-density turbidites increase. A grain-size analysis reveals a broad downslope fining trend of turbidite and debrite beds within slope channels with increasing water depth, and some notable bypass of conglomeratic facies to the lowermost slope channels and basin floor fans. The architecture of the slope channels changes from lateral to aggradational infill downstream. The Bey Malec clinoforms and its slope channels add new knowledge on downslope changes for sediment delivery in relatively shallow (<500 m water depth), prograding-dominant deepwater basins. They also highlight one of very few outcropping examples of oblique-type clinoforms.     

Assessment of runoff,water and sediment quality in the Selenga River basin aided by a web-based geoservice

The Selenga River is the main artery feeding Lake Baikal. It has a catchment of ~450000 km² in the boundary region between Northern Mongolia and Southern Siberia. Climate, land use and dynamic socioeconomic changes go along with rising water abstractions and contaminant loads originating from mining sites and urban wastewater. In the future, these pressures might have negative impacts on the ecosystems of Lake Baikal and the Selenga River Delta, which is an important wetland region in itself and forms the last geobiochemical barrier before the Selenga drains into Lake Baikal. The following study aims to assess current trends in hydrology and water quality in the Selenga-Baikal basin, identify their drivers and to set up models (WaterGAP3 framework and ECOMAG) for the prediction of future changes. Of particular relevance for hydrological and water quality changes in the recent past were climate and land use trends as well as contaminant influx from mining areas and urban settlements. In the near future, additional hydrological modifications due to the construction of dams and abstractions/water diversions from the Selenga’s Mongolian tributaries could lead to additional alterations.     

Spatial distribution and estimation of rainfall trends and erosivity in the Epitácio Pessoa reservoir catchment,Paraíba,Brazil

Natural Hazards - The main goals of this study are to better understand the spatial and temporal variabilities in rainfall and to identify rainfall trends and erosivity for the period from 1963 to...     

Hydrological and hydrochemical studies in the permafrost drainage basin of Oobloyah Valley,N-Ellesmere Island,NWT, Canada

During the “Heidelberg-Ellesmere-Island-Expedition” to Oobloyah Valley, N-Ellesmere Island, NWT, Canada in 1978 the summerly water balance of this high arctic catchment area with continuous permafrost was investigated. The following results will be presented:

1. Three hydrogeological areas with different physical parameters, thawing depths and drainage are distinguished and studied on slope I, II and slope III.
2. The climatic situation of summer 1978 was mainly influenced by the change of radiating and cloudy periods. Due to air temperatures (2 m above ground), which never went below 0°C, these periods regulated the thawing of the glaciers and the respective run-off.
3. Most of the winterly snow cover melted before July, thereafter soil thawing and its drainage began. In none of the sediments the latter reached field capacity.
4. Considering the course of daily discharge and soil water balance the three studied streams were characterized by the “Dry-Weather-Discharge-Line”, DWL, of Peri-Creek the “Radiation-Weather-Discharge-Line”, RWL, and the “Cloudy-Weather-Discharge-Line”, CWL, of Nukapingwa River and Heidelberg River.
5. The periglacial streams never had a measurable sediment load not even during snow melt, whereas the glacial and mixed glacial-periglacial streams as Nukapingwa River and Heidelberg River showed a sediment drift depending on their run-off. Only in Peri-Creek the ion concentrations were correlated to discharge.
6. Precipitation (snow plus rain) add up to 51% of the summerly water balance. The glaciers contributed up to 48%, and the actual evapotranspiration is only 1%.

     

Hydrothermal recrystallization and transformation of tridymite

Well ordered tridymites containing atmost 0.016% Na (0.004% Na) were prepared at 1400° C from Na₂WO₄-(K₂WO₄-) fluxes using high purity amorphous silica as starting material. No further reduction of these Na-contents was attainable by soxhlet extraction. These tridymites were treated hydrothermally at temperatures between 815 and 950° C and 200 bars H₂O. The products obtained were investigated optically as well as by powder X-ray methods and were analyzed for Na-contents: the hydrothermal treatment resulted either in recrystallization of tridymite or transformation into quartz mostly depending on Na-contents. Na-contents below about 0.015% tend to favour recrystallization of tridymite within the quartz field (<870° C), Na-contents above about 0.03% tend to favour formation of quartz within the tridymite field (>870° C). This may be due to influences of Na-traces either on the kinetics or on the equilibrium temperature of tridymite-quartz transformation.     

Precipitazioni intense al margine meridionale delle Alpi

Riassunto In questo lavoro sono studiate specialmente le precipitazioni intense (quantità giornaliere 50 mm) del periodo 1901–1950, mediante 6 stazioni del margine meridionale delle Alpi, confrontate con una stazione del nord delle Alpi (Zurigo) e una della Lombardia (Milano). Si trova che le precipitazioni intense sul versante sud delle Alpi sono molto più frequenti che nelle stazioni di confronto e che al margine meridionale delle Alpi è considerevole l'apporto delle precipitazioni intense alla somma totale.

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Summary In the present paper is being examined particularly the frequency of large precipitations (daily amounts 50 mm) on the southern side of the Swiss Alps (period 1901–1950). For this purpose the conditions of precipitation of six stations in Southern Switzerland are compared with those of one station on the northern side of the Alps (Zürich) and of one in Lombardy (Milan). It is shown that the frequency of large precipitations is much higher on the southern slope of the Alps than on the stations mentioned in comparison. Also that the share of the amount of large precipitations on the total amount is rather considerable.

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Zusammenfassung In der vorliegenden Arbeit werden vor allem die grossen Niederschläge (Tagesmengen 50 mm) der Periode 1901–1950 anhand von 6 Stationen auf der Alpensüdseite untersucht und mit je einer Station auf der Alpennordseite (Zürich) und in der Lombardei (Mailand) verglichen. Dabei zeigt sich, dass grosse Niederschläge an der Südabdachung der Alpen viel häufiger sind als an den Vergleichstationen und dass der Anteil der grossen Niederschläge an der Gesamtmenge am Alpensüdfuss beträchtlich ist.

     

Heat flow and quantity of methane deduced from a gas hydrate field in the vicinity of the Dnieper Canyon,northwestern Black Sea

Seismic reflection data document for the first time the existence of a BSR in a limited area west of the Dnieper Canyon in the northwestern Black Sea. Seismic wide-angle data suggest that gas hydrates occupy in average 15±2% of the pore space in a zone of 100 m in thickness. A conservative quantification of the amount of methane associated with this gas hydrate occurrence is about 12±3×10¹¹ m³ (0.6±0.2 Gt of methane carbon). Conductive heat flow deduced from the BSR depth is in the range of 21±6 to 55±15 mW m^–2.     

Misure della radiazione ultravioletta diretta del sole a Locarno-Monti

Summary From 1945–47 measurements of direct ultra-violet radiation from the sun have been carried out with a cadmium cell at Locarno-Monti. Besides seasonal and diurnal variations, researches were made concerning the influence of airclearness, of airmasses and of pervailing weather conditions upon UV-radiation (continental and marittime airmasses, northfoehn, divergences of the wind, fronts, etc.). Very important differences in the amount of UV-radiation were observed.

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Zusammenfassung Von 1945–47 wurde in Locarno-Monti mit einer Cadmiumzelle die direkte Sonnenstrahlung im Ultraviolett gemessen. Neben dem Tages- und Jahresgang wurde vor allem die Abhängigkeit der UV-Strahlung von der Reinheit der Luft, von den Luftmassen und den herrschenden Wetterlagen (maritime und kontinentale Luftmassen, Nordföhnlagen, Winddivergenz, Fronten, usw.) untersucht. Dabei zeigen sich sehr bedeutende Unterschiede in der UV-Strahlung.

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Résumé Avec la cellule au cadmium on a mesuré la radiation ultraviolette directe du soleil durant la période 1945–1947. On examine la variation diurne et annuelle de cette grandeur, ainsi que sa dépendance du degré de pureté de l'air, des masses d'air maritime et continental, des situations avec «Föhn» du nord, avec divergence des vents, etc. Nos recherches ont montré que l'intensité des radiations UV subissent de très fortes variations.

     

Elektronenmikroskopische Untersuchungen an mikritischen Kalken

Zusammenfassung Es werden die Entstehungsmöglichkeiten von mikritischen Kalken diskutiert und an Hand von elektronenmikroskopischen Aufnahmen Hinweise auf genetische Interpretationen vorgeführt.

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The origin of micritic limestones is discussed and genetic interpretation of micrites from different environments, studied by electron microscope, is given.

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Résumé L'origine des calcaires micritic est discutée et une interprétation génétique des micrites de milieux différents est donnée à l'aide de la microscopie électronique.

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Vorgetragen auf der 56. Jahresversammlung der Geologischen Vereinigung in Wien im Februar 1966.