Sedimentology of a sandur formed by multiple jökulhlaups,Kverkfjöll,Iceland

The Kverkfjöll sandur in north Iceland is the furthest upstream of a suite of fluvial landforms extending for 200 km along the Jökulsá á Fjöllum river. Incision of the sandur exposes over 3 km of sedimentary sections, up to 15 m in height. A sandur wide, well-bedded succession of matrix-rich cobble-gravel and pebble/granule gravel, with individual beds 0.2 to 0.5 m thick indicates that the sandur is primarily the product of sandur-wide sheet-floods, with sediment-rich hyperconcentrated flows and also some debris flows and channelised turbulent flows. This interpretation is evidenced by bedded hyperconcentrated flow deposits occurring as laterally extensive tabular depositional units that dominate the entire sandur, reflecting the unconfined nature of the flow. Clast-supported boulder-gravel units interpreted as the product of macroturbulent flow occur in relatively narrow, but deep channels. The sedimentary succession is interpreted as the product of at least six volcanically generated catastrophic outburst floods (jökulhlaups) during the Little Ice Age. The sedimentology of these Little Ice Age flood deposits, on a small, high-gradient sandur, contrasts strongly with the deposits of volcanically-generated jökulhlaups on large, low-gradient coastal sandar, and sandar associated with retreating glaciers which have been the basis for most previous models of jökulhlaup sedimentation.     

Determination of radioactivity levels in Akhisar,Gördes,Gölmarmara and Sindirgi regions,Western Turkey

In this study, radioactivity measurements in the environment of Akhisar, Gölmarmara, Gördes and Sindirgi regions in Western Turkey were investigated in order to evaluate the implications of any excess radioactivity in the environment of geological formation. The radioactivity concentrations of ⁴⁰K, ²³⁸U and ²³²Th radionuclides in the soil samples were measured by a NaI(Tl) gamma spectrometer system, and the radium activity concentrations in the water samples were also analyzed by an ZnS(Ag) alpha counter by the collector chamber method. The radioactivity of ⁴⁰K, ²³⁸U and ²³²Th in soils ranged 2.80–2,347.77, 9.90–256.19 and 9.66–106.53 Bq kg^?1, respectively. The activity of ²²⁶Ra in the water samples ranged from 0.03 Bq L^?1 (0.89pCi/L) to 0.80 Bq L^?1 (21.58pCi/L). In addition, the external terrestrial gamma dose rate in air (nGy h^?1), annual effective dose rate (mSv year^?1) and radium equivalent activity (Bq kg^?1) were calculated and compared with international standard values.     

See-Erz,Roströhren und verwandte Konkretionen

Zusammenfassung Den Röhrensteinen des Großen Plöner Sees verwandte Bildungen werden an Hand der wichtigsten Literatur beschrieben. Fe- und Mn-Konkretionen — unter diese fallen See-Erze, Roströhren, Fe-Anhäufungen in Seesedimenten u. a. — sind nach dem jetzigen Stande der Forschung im wesentlichen durch Mikroben gebildet oder wenigstens in ihrer Entstehung durch diese Organismen unterstützt, obgleich meistens eine rein chemisch-physikalische Deutung der Prozesse möglich ist. Die Grundzüge der regionalen Verbreitung von See- und Wiesenerzen in Schweden wurden zuerst vonStapff dargelegt und später durchNaumann den neuesten Anschauungen angepaßt. Kalk, Ton und elektrolytreiche Gewässer unterdrücken die Erzbildung. Auch von karbonatreichen Böden und Wässern sind Anhäufungen von Eisenhydroxyd bekannt, aber den schwedischen Massenvorkommen gegenüber geringfügig. Die Entstehung der Roströhren wird näher erläutert. O₂-Abgabe der Pflanzenwurzeln, physikalische Adsorptionsprozesse, wahrscheinlich auch Gerbstoffe und Kalk usw. fällen Fe und Mn aus. Den Röhrensteinen Ähnliche Bildungen sind bei den Wohnröhren vonCorophium beobachtet worden. Auch die Osteokollen gestatten eine Parallele; dennoch handelt es sich dabei um Kalkfällung. Die bekanntesten fossilen Roströhren stammen aus dem Münzenberger Sandstein.     

Über röhrenförmige Lösungserscheinungen im Kalke bei Amt-Mitterbach bei St. ägyd am Neuwalde,Niederösterreich

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Late Weichselian and Holocene relative sea-level history of Bröggerhalvöya,Spitsbergen

Radiocarbon-dated whalebones from raised beaches record a relative sea-level history for Bröggerhalvöya, western Spitsbergen that suggest a two-step deglaciation on Svalbard at the end of the late Weichselian glaciation. The late Weichselian marine limit was reached at about 13,000 yr B.P. and was followed by relatively slow emergence until about 10,000 yr B.P. either in response to ice unloading in the Barents Sea, initial retreat of local fjord glaciers, or some combination of the two. Rare whale skeletons dating between 13,000 and 10,000 yr B.P. indicate that the Norwegian Sea was at least seasonally ice free during that interval. Deglaciation of Spitsbergen is recorded by the rapid emergence of Bröggerhalvöya after 10,000 yr B.P. This was followed by a transgression during the mid-Holocene, here named the Talavera Transgression, and another in modern times. Raised beach morphologies suggest striking differences in nearshore depositional processes before and after 10,000 yr B.P. that are probably related to changes in the rate of uplift and in sea-ice conditions.     

Sediment character in a micro-tidal, harbor-estuary environment, Göteborg, Sweden

Harbor-estuaries are complex sedimentary environments where both natural and anthropogenic processes influence the distribution and accumulation of sediments, which in turn is of importance for maintenance dredging and pollution control. This paper uses sediment characteristics from the Göta älv estuary, Sweden to evaluate the natural estuarine processes that persist despite the extensive human impact on the estuary and to separate and characterize depositional sub-environments. The most important harbor processes include maintenance dredging and turbulence from ship traffic, and their influence upon shallow stratigraphy and sediment distribution and deposition is significant. Polymodal particle-size distributions are interpreted to reflect the natural estuarine transport processes. Suspension transport is generally predominant, except in the river and inner harbor where bottom transport and selective deposition of sand occur. Particle-size characteristics divide the estuary into four depositional areas: the river and the inner, middle, and outer harbor. The shallow stratigraphy reveals a hiatus between the firm silty clays and the loose recent sediments. The hiatus in the stratigraphy is probably related to dredging in most areas of the harbor. Significant maintenance dredging and turbulence from ship traffic also influence the accumulation (0–61 cm) of recent sediments, during the 20th century.     

Strukturböden,Solifluktion und Frostklimate der Erde

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Untersuchungen am Grauen Salzton der Grube „Königshall-Hindenburg”, Reyershausen bei Göttingen

Zusammenfassung Es wurden 15 stratigraphiseh aufeinanderfolgende Proben des Grauen Salztons aus dem Kalisalzbergwerk Königshall-Hindenburg, Reyershausen bei Göttingen, auf ihren Mineralbestand untersueht und ihre chemische Zusammensetzung ermittelt. Die Hauptkomponenten des loslichen Anteils (Salz) sind Anhydrit, Steinsalz und Dolomit, während sick der unlösliche Anteil zum größten Teil aus Illit, Chlorit und Quarz zusammensetzt. Die Korngrößenfraktionen < 6,32 des unlöslichen Anteils bestehen fast aussehlioßlich aus Rlit und Chlorit. Die röntgenographische und mikroskopische Untersuchung ergab eine kontinuierliche Zunahme des Illitgehaltes vom Liegenden zum Hangenden des Profils und eine Abnahme des Chloritgehaltes. Im Zusammenhang mit der Röntgenanalyse konnte der Chemismus dieser beiden Tonminerale bestimmt werden. Es zeigte sich, daß der Chlorit seine Zusammensetzung innerhalb des Profils ändert. Sie entspricht der des Sheridanits (Liegendes), des Klinochlors und des Pennins (Hangendes). Für den Hit muß detritische Herkunft angenommen werden, während der Chlorit sich wahrscheinlich aus der Lösung gebildet hat und damit eine diagenetische Neubildung ist.     

Mineralogical and petrological features of the Cemilköy ignimbrite,Cappadocia, Turkey

The Cemilköy ignimbrite is one of the voluminous ignimbrite deposits in Cappadocia. The Cemilköy ignimbrite contains pumice and lithic clasts of volcanic and ophiolitic origin in an ash matrix. The unwelded Cemilköy ignimbrite is distinguished from other deposits in Cappadocia by flattened pumices, elongate vesicles and a slaty fabric. The mineral assemblage of the Cemilköy ignimbrite is plagioclase, biotite, quartz and oxides (magnetite and Ti-magnetite) and the matrix is glassy. Eutaxitic texture is dominant and all pumice clasts have a vitrophyric-porphyritic texture. The same textural properties were observed throughout the spatial distribution of Cemilköy ignimbrite. Microprobe studies reveal that plagioclase compositions range from albite through oligoclase-andesine. Estimated plagioclase-liquid temperatures (T) and pressures (P) are varying between 806 and 847?°C and 4.2–7.1 (kbar), and the H₂O content of the melt is estimated to have been 5?wt.% from the pumice clasts. Based on geochemical data, the Cemilköy ignimbrite is rhyolitic and calc-alkaline in character, and all pumice clasts are enriched in LIL and LRE elements relative to HFS elements. Negative Nb, Ta and Ti anomalies, ratios of Ba/Nb >28 (56–77), Ba/Ta ?450 (590–700) and Th/Yb vs. Ta/Yb are consistent with a subduction-related origin. According to the geochemical and mineralogical-petrographical data, the Cemilköy ignimbrite originated from partial melting of a mantle source which was enriched during previous subduction processes with variable degrees of assimilation fractional crystallization (AFC) through time and Cemilköy ignimbrite erupted from a crustal magma chamber at shallow to intermediate depth.     

I. Erdöl Ergebnisse der erdölgeologischen Erforschung Nordwestdeutschlands 1932–1947, ein Überblick

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Ichnological evidence of jökulhlaup deposit recolonization from the Touchet Beds,Mabton, WA,USA

The late Wisconsinan Touchet Beds section at Mabton, Washington reveals at least seven stacked jökulhlaup deposits, five showing evidence of post-flood recolonization by vertebrates. Tracemakers are attributed to voles or pocket mice (1–3 cm diameter burrows) and pocket gophers or ground squirrels (3–6 cm diameter burrows). The Mount St. Helens S tephra deposited between flood beds contains the invertebrate-generated burrows Naktodemasis and Macanopsis. Estimates of times between floods are based on natal dispersal distances of the likely vertebrate tracemakers (30–50 m median distances; 127–525 m maximum distances) from upland areas containing surviving populations to the Mabton area, a distance of about 7.9 km. Tetrapods would have required at least two to three decades to recolonize these flood beds, based on maximum dispersal distances. Invertebrate recolonization was limited by secondary succession and estimated at only a few years to a decade. These ichnological data support multiple floods from failure of the ice dam at glacial Lake Missoula, separated by hiatal surfaces on the order of decades in duration. Ichnological recolonization times are consistent with published estimates of refill times for glacial Lake Missoula, and complement the other field evidence that points to repeated, autogenically induced flood discharge.     

Geologie des Erdöls nach Höfer

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Persönliches

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