Summertime Mixing Heights At Vienna, Austria, Estimated from Vertical Soundings and by a Numerical Model

Mixing heights calculated by the Danish OML meteorological pre-processor are compared to those diagnosed from radio- and tether-sonde vertical potential temperature profiles. All methods give reliable estimates of noon mixing heights deduced from radiosoundings, especially when the boundary layer is fully convective. Differences are larger during convective conditions without a well-defined capping inversion in the radiosonde potential temperature profile or when OML calculates a mechanical mixing height. The OML model is also able to calculate the daily course of the mixing height as expected. The tethersonde-derived mixing heights are especially valuable during the morning rise of the elevated inversion. Modifications to all three methods to improve mixing-height predictions are discussed.     

An experimental comparison of three direct methods of marine source signature estimation

Three methods for estimation of the pressure wavefield generated by a marine airgun array are tested experimentally and compared. In the trial a variety of radiation angles and array configurations were used and some large synchronization errors were deliberately introduced. The source was equipped with near-field hydrophones and a subsource ministreamer. A tethered far-field hydrophone was used so that the three estimated far-field signatures could be compared with an independent measurement. The knowledge of the source signature is important for on-board source array QC, deconvolution, multiple attenuation, stratigraphic trap prediction, modelling and inversion, AVO analysis and reservoir monitoring. The methods perform very well and give estimates whose frequency-domain spectra match the measured spectra to within a few dB and within a few tens of degrees of phase over the tested bandwidth of 3.5–110 Hz. The time-domain error-energy is typically only a few per cent of the signal energy for radiation angles within about 30° of the vertical. The third method proved to be sensitive to an experimental shortcoming leading to overloading of the ministreamer and meaningful comparison was not possible for some test configurations.     

An Stratigraphische Hiate gebundene Vererzungen in den Tschechoslowakischen Karpaten

During the course of the geotectonic development of the West Carpathians there were ore mineralisation periods, which are associated with different stratigraphical hiatuses. Hematite-magnetite ore was deposited in the first period between the Silurian and the Devonian. In both the Middle and the Upper Carboniferous, some stratiform siderite deposits originated, which were exploited in the vicinity of Dobiná and Mlynky during about the last 100 years. In the Permian, some haematite occurrences, fossil gold placers and uranium-bearing strata were formed, the last of which was exploited. Some minor haematite occurrences are widespread in the Lower Triassic. The same type of occurrence is known in the Upper Triassic and in the Lower Jurassic, too. In the Jurassic, small occurrences of manganese ore are known. Bauxite occurreces were found in the Middle and Upper Cretaceous, but they are very small. More important are the sedimentary manganese deposits, which were deposited in the Middle Eocene. These were exploited during the last 70 years. The fossil gold placers of the east Slovakian, Paleogene flysch series are very interesting from genetic point of view. The small kaoline, bauxite and silicate-nickel occurrences, which are associated with the alteration processes of basic rocks of different age, were found during the Miocene. The Quaternary period is well known for its gold placers, from which those of the Danube river as well as others were exploited in the past.

---

---

Nach einem Vortrag gehalten auf der Tagung des Lagerstättenausschusses der G. D. M. B. und der S. G. A. in Clausthal am 4. / 5. April 1975     

Equilibrium-disequilibrium relations in the Monte Rosa Granite,Western Alps: Petrological,Rb-Sr and stable isotope data

Nine samples from the Monte Rosa Granite have been investigated by microscopic, X-ray, wet chemical, electron microprobe, stable isotope and Rb-Sr and K-Ar methods. Two mineral assemblages have been distinguished by optical methods and dated as Permian and mid-Tertiary by means of Rb-Sr age determinations. The Permian assemblage comprises quartz, orthoclase, oligoclase, biotite, and muscovite whereas the Alpine assemblage comprises quartz, microcline, albite+epidote or oligoclase, biotite, and phengite. Disequilibrium between the Permian and Alpine mineral assemblages is documented by the following facts: (i) Two texturally distinguishable generations of white K-mica are 2 M muscovite (Si=3.1–3.2) and 2 M or 3 T phengite (Si=3.3–3.4). Five muscovites show Permian Rb-Sr ages and oxygen isotope fractionations indicating temperatures between 520 and 560 ° C; however, K-Ar ages are mixed or rejuvenated. Phengite always shows mid-Tertiary Rb-Sr ages, (ii) Two biotite generations can be recognized, although textural evidence is often ambiguous. Three out of four texturally old biotites show mid-Tertiary Rb-Sr cooling ages while the oxygen isotopic fractionations point to Permian, mixed or Alpine temperatures, (iii) Comparison of radiogenic and stable isotope relations indicates that the radiogenic isotopes in the interlayer positions of the micas were mobilized during Alpine time without recrystallization, that is, without breaking Al-O or Si-O bonds. High Ti contents in young muscovites and biotites also indicate that the octahedral (and tetrahedral) sites remained undisturbed during rejuvenation. (iv) Isotopic reversals in the order of O¹⁸ enrichment between K-feldspar and albite exist. Arguments for equilibrium during Permian time are meagre because of Alpine overprinting effects. Texturally old muscovites show high temperatures and Permian Rb-Sr ages in concordancy with Rb-Sr whole rock ages. For the tectonically least affected samples, excellent concordance between quartz-muscovite and quartz-biotite Permian temperatures implies oxygen isotope equilibrium in Permian time which was undisturbed during Alpine metamorphism. Arguments for equilibrium during the mid-Tertiary metamorphism are as follows: (i) Mid-Tertiary Rb-Sr mineral isochrons of up to six minerals exist, (ii) Oxygen isotope temperatures of coexisting Alpine phengites and biotites are concordant.The major factor for the adjustment of the Permian assemblages to Alpine conditions was the degree of Alpine tectonic overprinting rather than the maximum temperatures reached during the mid-Tertiary Alpine metamorphism. The lack of exchange with externally introduced fluid phases in the samples least affected by tectonism indicates that the Monte Rosa Granite stewed in its own juices. This seems to be the major cause for the persistence of Permian ages and corresponding temperatures.     

Temperatur-Änderungen in der Erdgeschichte

This paper on “Temperature changes in earth-history” is an extension of a lecture given as an introduction to a section of equal title on the annual meeting of the Geologische Vereinigung, March 1976, in Hannover. The general development of paleoclimatological research in the last 300 years is represented on two diagrams (fig. 1–2) showing also the part of different climatic indicators. Otherwise, however, mostly new results and problems of the last years are treated (mainly papers since 1973; references of older literature are to be found in the 3^rd edition of the author's book on “Climates of the Past” = “Klima der Vorzeit”, Enke/Stuttgart 1974). This paper refers a) to some short comments on certain climatic indicators as diamictites (a similar term isSchermerhorn's “mixtite”, but “diamictite” is 6 years older and has therefore priority to “mixtite”) and “stellate nodules” (in the chapter “Mesozoic”) indicating perhaps cool climate in the Arctic. - b) Some great ice-ages are briefly discussed: Huronian (very important because of its old age); Late Proterozoic (“Eocambrian”) with many problems on account of its pretended worldwide extension. but with many uncertainities (partly pseudotillites, inconsistent paleomagnetic poles, combination of tillites with dolomites etc.); Permo-Carboniferous (many hypothesises up to 1975 try to explain the pretended “equatorial” position of tillites); Cenozoic ice-age (once “Quaternary” ice-age), with table 1 indicating some possibilities to evaluate the beginning of glaciations in Tertiary time (fig. 4). Why does glaciation start in Antarctica in the Tertiary? (Not or not only on account of drift via South Pole, but perhaps because of high relief and changes in global paleogeography). — c) Diagram of the great ice-ages in earth-history (fig. 6 b): it probably shows not all ice-ages but only the known ones indicating their maxima (i. e. times when inlandice extended to middle latitudes). This curve is probably essentially correct back to 300–400 m. y. yet especially the Precambrian time is still mostly paleoclimatic noman's-land. It is not possible to fix beginning and end of the Pre-Tertiary ice-ages exactly but at any rate the “akryogene” climates lasted longer than the “kryogene” ones (“kryogene” defined as climate with “much ice” [“pleistokryogene”], “akryogene” not as climate “without ice” but as climate with “a little ice” [“oligokryogene”]). - d) Periodicities in the temperature history: before exact dates were available (especially for Late Proterozoic and Huronian ice-ages) and before the Sahara glaciation of the Old Paleozoic was known, a periodicity of 250–300 m. y. was likely to exist. Therefore relations to the “Galactic year” were reasonable, stimulating attempts to find out plausible mechanisms for such a relation. But now, such a periodicity seems unlikely to exist (and much more one of 155 m. y., supposed byWilliams). The relative constancy of global earth temperatures over at least more than 2 billion years is more striking than their variations, though regionally the depressions may be very conspicious (in the middle, “sensitive” latitudes). Such depressions, however, are triggered by very small climatic changes on account of the existence of a hydrosphere with temperatures very favorable for a transformation of water into ice and vice versa. No other celestial body of our solar system has these optimal conditions with the consequences of occasional initiation of ice-ages. Ice ages, so to speak, are an inherited pecularity of the earth. The earth is the only “Ice-age Planet”. Under these circumstances, relatively small factors may cause ice-ages: multilateral origin of climatic changes. The most efficient parameters may be paleogeographic variations (relief etc. inclusive continental drift). Some comments are made on the radiation curves reflecting not the direct cause of glacials and interglacials but perhaps shorter climatic variations as they appear possibly in the curves of ocean temperatures (Emiliani etc.). Volcanic ashes seem not to have any farreaching influence on global temperatures; at least it is geologically impossible to support appropriate hypothesises by observations on continental volcanic sequences. The number of ash-layers in deep-sea cores may reveal sounder arguments though much more observations are needed to corroborate this supposition. — Table 2 gives a summary of the primary (planetary), secondary (multilateral) and — in special situations — tertiary “autocyclic” causes of climatic changes. Table 3 focuses on autocycles i. e. mechanisms which run. off automatically and could have caused the regular climatic variations in the Late Pleistocene with the classic glacialinterglacial sequence (not known from the older Quaternary or Pre-Tertiary ice-ages). In my opinion the most probable hypothesises on autocycles are those which were founded on wide extending subarctic continents of the northern hemisphere (qualified for the formation of large inlandice) in combination with mighty oceanic heat storage (Stokes, D. P. Adam, R. E. Newell).     

Anisotropy of magnetic susceptibility variations in a single icelandic columnar basalt

Measurements of the anosotropy of magnetic susceptibility in 34 specimens drilled from a single Icelandic columnar basalt segment reveal a preferred, long-axis alignment of magnetic minerals normal to the long axis of the column and well grouped. Maximum elongation of these minerals occurs in regions which crystallized late, as independently indicated by relative samarium concentrations. We propose that the variations in magnetic mineral elongation are controlled by variations in thermal stress in the cooling column, before complete solidification. An upper limit of 75–100 bars is suggested for these stresses.     

Chloritoid-bearing metapelites associated with glaucophane rocks in western Crete,Greece

Problems related to the formation of chloritoid in metapelites, associated with lawsonite-glaucophane bearing metabasalts, in the quartzitephyllite series of western Crete (Greece) are discussed. It is supposed that chloritoid was formed, during prograde metamorphism, according to a gliding-equilibrium reaction of the type (Fe,Mg)-carpholite₁+chlorite₁ (Fe,Mg)-carpholite_{1 2}+(Fe,Mg)-chloritoid_{1 2} +chlorite_1→2+quartz+H₂O ? (Fe,Mg)-chloritoid₂+chlorite₂+quartz+H₂O. This view is stipulated by the occurrence of ferrocarpholite-chloritoid schists in the southeastern part of central Crete. The assemblage chloritoid+ lawsonite recently recognized in western Crete provides evidence that the formation of chloritoid started well within the stability field of lawsonite.