ALBERT

Notizen: The widespread use of common depth point techniques has emphasized the need for accurate static corrections. Manual interpretation methods can give excellent results, but a computer technique is desirable because of the great volumn of data recorded in common depth point shooting. The redundancy inherent in common depth point data may be used to compute a statistical estimate of the static corrections. The corrections are assumed to be time-invarient, surface-consistent, and independent of frequency. Surface consistency implies that all traces from a particular shot will receive the same shot static correction and all traces from a particular receiver position will receive the same receiver correction.Time shifts are computed for all input traces using crosscorrelation functions between common depth point traces. The time shift for each trace is composed of a shot static, a receiver static, residual normal moveout if present, and noise. Estimates of the shot and receiver static corrections are obtained by averaging different sets of the measured time shifts. Time shifts which are greatly in error are detected and removed from the computations.The method is useful for data which has a moderate to good signal to noise ratio. Residual normal moveout should be corrected before estimating the statics. The program estimates the statics for correctly stacking common depth point traces but it is not sensitive to constant or very slowly changing static errors.

Notizen: It was found in Part I of this paper that approximating the sharp cut-off frequency characteristic best in a mean square sense by an impulse response of finite length M produced a characteristic whose slope on a linear frequency scale was proportional to the length of impulse response, but whose maximum overshoot of ±9% was independent of this length (Gibbs' phenomenon). Weighting functions, based on frequency tapering or arbitrarily chosen, were used in Part II to modify the truncated impulse response of the sharp cut-off frequency characteristic, and thereby obtain a trade-off between the value of maximum overshoot and the sharpness of the resulting characteristic. These weighting functions, known as apodising functions, were dependent on the time-bandwidth product Mξ, where 2ξ, corresponded to the tapering range of frequencies.Part III now deals with digital filters where the number 2N–1 of coefficients is directly related to the finite length M of the continuous impulse response. The values of the filter coefficients are taken from the continuous impulse response at the sampling instants, and the resulting characteristic is approximately the same as that derived in Part II for the continuous finite length impulse response. Corresponding to known types of frequency tapering, we now specify a filter characteristic which is undefined in the tapering range, and determine the filter coefficients according to a mean square criterion over the rest of the frequency spectrum. The resulting characteristic is dependent on the time bandwidth product Mξ= (N–1/2)ξ up to a maximum value of 2, beyond which undesirable effects occur. This optimum partially specified characteristic is an improvement on the previous digital filters in terms of the trade-off ratio for values of maximum overshoot less than 1%. Similar to the previous optimum characteristic is the optimum partially specified weighted digital filter, where greater “emphasis is placed on reducing the value of maximum overshoot than of maximum undershoot”. Such characteristics are capable of providing better trade-off ratios than the other filters for maximum overshoots greater than 1/2%. However these filters have critical maximum numbers 2.NC–1 of coefficients, beyond which the resulting characteristics have unsuitable shapes. This type of characteristic differs from the others in not being a biassed odd function about its cut-off frequency.

Notizen: In Part I of this paper, we examined the properties of the best mean square approximation to the sharp cut-off frequency characteristic by an impulse response of finite length. It was found that the sharpness of cut-off for the resulting frequency characteristic depended on the length of the impulse response–but because of the discontinuous nature of the specified frequency characteristic, this best mean square approximation always had a maximum overshoot of ± 9%, independent of the length of the impulse response (Gibbs phenomenon).In Part II, we investigate ways of reducing this ± 9% overshoot at the expense of a reduced sharpness of cut-off. The discontinuous frequency characteristic is first approximated by a continuous characteristic with linear or cosine frequency tapering. The impulse response for such tapered characteristics consists of the impulse response of the discontinuous frequency characteristic weighted by a certain function corresponding to the type of tapering employed. The best mean square approximation to the tapered characteristic by an impulse response of finite length M will produce a frequency characteristic whose properties are now dependent on the time-band width product Mζ, where 2ζ is the tapering range.A trade-off exists between the maximum overshoot and the sharpness of cut-off for the resulting characteristic for both forms of frequency tapering. Instead of considering other forms of tapering in the frequency domain, we now investigate arbitrarily chosen weighting functions in the time domain to determine the minimum length of impulse response for a minimum value of maximum overshoot and a maximum value of sharpness of cut-off.Part III will discuss the digital realization of the above finite length impulse responses together with the optimum partially specified digital filter approximation to the desired frequency characteristic.

Notizen: Book reviewed in this article:Le Filtrage en Sismique, Tome IJ. AUBOUIN “Geosynclines” (Developments in Geotectonics 1). Elsevier Publishing CompanyEarth and Planetary Science Letters Vol. 1. Nr. 2H. Ramberg Gravity, Deformation and the Earth's Crust Academic Press“Potassium Argon Dating” Compiled by O. A. Schaeffer and J. Zähringer

Notizen: Deep seismic sounding was performed along two profiles which cross at the Dinarides area right angles. One of the profiles goes far into the Adriatic Sea.Besides considerations on the lithophysical conditions, characteristics of the registered waves are analysed. The amplitude curves and curves of amplitude ratios are shown. Special attention was paid to the frequency of the registered waves.In order to obtain a better knowledge of the registered wave pattern three-component recordings of waves were carried out. The analysis of the records obtained is given, with particular regard to the possibility of creating converted waves.The Earth's crust structure along the profiles II and III is given.

Notizen: Nomograms for solving equations in multilayer and dipping layer cases are presented. The nomograms constructed are used to solve the following equations: I. Intercept-time formula. 2. Critical distance formula. 3. Critical angle formula. 4. Critical angle and dip angle formula. 5. Vertical depth formula.

Notizen: When, in a two-layer earth, the substratum is insulating or infinitely conducting, the thickness of the top layer can be determined from surface potential measurements along a radius from a single point power electrode. The observed potential needs to be numerically integrated in a direction perpendicular to the said radius, and Figure 4 can then be used to find the thickness. A field example is included.

Notizen: In order to increase the seismic efficiency of the Sparker-system developments were made in 1966/67. Results illustrating the main steps of this development are discussed. A new type of electrode called Transploder electrode was field-tested and proved to be promising.

Notizen: The theory of electrical dipole soundings proved that this method can produce resistivity measurements, which are comparable with those obtained by electrical soundings of the Wenner or Schlumberger type. Their main advantage is the use of short cable lengths, which is important if the depth of penetration should be large.A considerable disadvantage of the dipole method is the great sensitivity to lateral discontinuities. Though these have an influence on the Schlumberger arrangement as well, they can disturb a dipole sounding to such an extent than an interpretation based on a horizontal layer case is no more possible.There are six different dipole arrays, which differ from each other with respect to the angle enclosed by the two dipole orientations-the current dipole AB and the measuring dipole MN. The theoretical comparison of the dipole arrays with the Schlumberger array concerning their sensitivity to lateral discontinuities is a useful basis for the choice of the most suitable configuration.Considering geological subsurface conditions the right choice of a dipole array can give an optimal result, i.e. a dipole sounding for which the sensitivity to lateral discontinuities is as small as possible under the given circumstances.

Notizen: Deconvolution and deringing are well known subjects and it is not necessary to state again their objectives nor the basical methods used to reach them. Let us just remember that, generally, among many others, the two following assumptions are made for simplification purposes:〈list xml:id="l1" style="plain"〉—for deconvolution, it is assumed that the recorded seismic signal is constant, meaning that its shape is the same all along the time interval during which the trace is to be deconvolved;—for de-ringing, it is assumed that the ringing period is constant and that the intensity of the ringing phenomenon is independant of the time.With these two assumptions, a single constant operator can be applied for deconvolving, deringing or both. In most cases, the time variations of the signal or of the ringing are small enough and the error resulting of the application of a constant operator is acceptable. It results into a slight increase of the noise level or into a small residual ringing in the processed trace.When this noise or the residual ringing are too important, the assumption of a constant signal and ringing period must be rejected. This is the case that is examined here according to the following steps:〈list xml:id="l2" style="plain"〉—short definition of the problem;—fast evaluation of some possible solutions;—the selected solution: resulting approximations and how to obviate them, computing method and a remark about the operators;—theoretical example: the efficiency of the process used is evaluated on data in which the results aimed at are known; the influence of the selection of numerical values to be assigned to the parameters is examined;—real cases: comparison of results obtained with the Protee process and with more conventional processes assuming a time invariance or including a weighted composition of several conventional processes each with a different operator.

Notizen: Sharp cut-off frequency filtering is carried out in the discrete time domain on digital computers. A convolution of the digital filter impulse response with the sampled input yields the output. For practical reasons, the length of the filter inpulse response, corresponding to the number of filter coefficients, is limited, and consequently the resulting frequency characteristic will no longer be identical to that originally specified. This is analogous to synthesising some specified frequency characteristic with a finite number of resistive, capacitative and inductive components.In Part I of this paper, we examine the effect of approximating the sharp cut-off frequency characteristic best in a mean square sense by an impulse response of finite length. The resulting frequency characteristic corresponds to the truncated impulse response of the specified frequency characteristic. It has a cut-off slope proportional to, and a mean square error inversely proportional to, the length of the impulse response, and is a biassed odd function about the cut-off frequency point. Because of the Gibbs phenomenon for discontinuous functions, the resulting frequency characteristic will always have a maximum overshoot with respect to the specified characteristic of ± 9%, regardless of the length of the corresponding impulse response. Equal length truncated impulse responses of specified filters with different cut-off frequencies yield frequency characteristics which are almost identical about their respective cut-off points. Now on a log frequency scale (as against a linear frequency scale implied previously) such characteristics may be made almost identical about the respective cut-off points by having the truncated impulse responses composed of an equal number of zero crossings. Results for the low-pass filter are applicable to the high-pass and band-pass characteristics.In the latter case, the mean square error is double that for a single slope characteristic (low-pass or high-pass) and the slopes at both edges of the passband are approximately equal in magnitude to the length of the impulse response (linear frequency scale).Part II of this paper is concerned with reducing the ± 9% overshoot that results from the discontinuous nature of the sharp cut-off frequency characteristic and which is not dependent on the length of the truncated impulse response. The reduction is achieved, at the expense of the steepness of cut-off for the resulting frequency characteristic, by the use of functions which weight the truncated impulse response of the specified frequency characteristic. These functions are called apodising functions. Among other variables, the length of the truncated weighted impulse response will determine the amount of maximum overshoot since the effective frequency characteristic being approximated is no longer a discontinuous function. The digital realization of the finite length impulse responses of Parts I and II is discussed in Part III, together with the optimum partially specified digital filter approximation to the desired frequency characteristic.

Notizen: The purpose of this report is to show a method of determining the top of a refractor departing from the times and slopes of the direct and inverse dromocrones. The method does not need topographical correction and can be applied without knowledge of the distance between the geophone and the shot point.These results having been obtained, the commonly accepted point of view is upset: instead of looking for two points on the surface corresponding to one point of the refractor, we try to etablish, starting with only one point from the surface, the two corresponding points from the top of the refractor.This method can be applied to isolated points and does not demand interpretative hypotheses of any kind, excluding the velocity evaluation of the overburden and of the refractor.The necessary calculations can be easily executed by means of a digital computer to which the dromocrone times and the distances between the geophones must be given. These calculations can also be executed by a person having no knowledge of refraction seismology.This report also examines the validity of the approximations involved in the method proposed.

Notizen: Determining the shape of a pulse generated by an explosion solely from the data provided by the recorded seismic trace is a difficult and even ambitious task.Knowledge of parameters such as length and number of “arches” of the pulse under study is, in fact, indispensable in solving this problem.These parameters cannot be found directly in the seismic trace, which nevertheless contains a great amount of information. Autocorrelation, with its mathematical and statistical properties, is an efficient way of making the best of this information.We compute all the autocorrelations of reflections having a given number of arches which fulfil certain conditions determined in advance. Then, after statistical testing of some parameters pertaining to the autocorrelations (abcissae of zeros, of extrema …), we select only those with a maximum likelihood. It is sufficient to consider only the reflections whose autocorrelations have been selected and to arrange them in groups according to their shape and arch number in order to obtain average pulses.In so doing several solutions are arrived at, but when considering a given number of traces, a single record for instance, it is possible by comparing these results with each other to considerably reduce their number.In the last part of the paper the nature of the impulse obtained with our method is examined in order to find out whether it is “minimum phase” for carrying out deconvolutions.

Notizen: In recent years considerable work has been done to devise a satisfactory non-dynamite seismic system that would replace dynamite in offshore areas. Prior to the advent of digital recording and processing, the non-dynamite sources have generally not provided the depth of penetration or the resolution required for satisfactory seismic interpretation.More recent developments in non-dynamite offshore marine sources include adaptation of the Vibroseis from a land unit to a marine unit, and adaptation of the Dinoseis unit from a land to a marine unit. The SUE (Seismic Underwater Explorer) system is a thermodynamic non-dynamite source utilizing a mixture of propane and oxygen detonated in a special chamber approximately 15 feet below the water surface. This source gives penetration to more than 4 sec in areas typified by Gulf of Mexico type geology and shows deeper penetration than had previously been obtained by dynamite along the western United States in areas with 20 lb charge limitations. A pneumatic source, the airgun, has been in production use in the United States since June 1966. This non-dynamite source provides an intriguing amount of versatility and can be expanded to provide additional energy as necessary to obtain the penetration desired. Tests using systems comprised of from eight to twenty-three airguns show penetration in excess of 5 seconds in many areas. Power spectra comparisons both in amplitude and frequency content demonstrate that this is a controlled source generating a controlled seismic wavelet and a controlled frequency spectrum that can be tailored to fit requirements of particular areas. Sample sections obtained in the Gulf of Mexico and the Pacific Ocean offshore California show adequate penetration to 5.0 seconds reflection time.Quantitative measurements with the airguns demonstrate the effect of:〈list xml:id="l1" style="custom"〉1Variation of the number of guns in the system;2Shaping the frequency spectrum by using different sizes of airguns in the system;3Effects on signal-to-noise ratios as a result of stacking several small energy sources together;4Reproducibility of the initial pulse wavelet from shot to shot.The improvement in record quality as a result of advanced digital processing with non-dynamite sources is comparable to that obtained with dynamite sources. Non-dynamite sources make additional improvements possible where high source multiplicity is advantageous. Excellent dynamic correlations yield accurate velocity control as well as definitions of apparent velocities attributable to multiples and primary-to-multiple amplitude relationships.Non-dynamite sources are being used more and more extensively in offshore exploration. The advent of digital recording and processing provides a means for improving depth of penetration and resolution of many non-dynamite sources.

Notizen: The use of MKS system units in preference to the cgs system facilitates accurate numerical calculation in magnetostatic problems in geophysics and the practice of stating the precise dimensions of every unit guards against confusion. Suggestions are made for the unique definition of quantities such as magnetic potential, etc. for which the undesirable circumstance of arbitrary alternatives still persists.

Notizen: The Fourier transform formula for a two-dimensional fault truncating a horizontal bed at an arbitrary angle of inclination is derived. The amplitude spectrum of the Fourier transform is found to give information about the depth to the top of the upper part of the faulted bed and the inclination of the fault-plane. Under suitable conditions the thickness and the displacement of the bed involved can be obtained. With actual field data, these transforms can be obtained at discrete points by a Fourier analysis of the gravity anomaly. A field example from the Logan fault area near Montreal, Que., Canada, is given.

Notizen: Die Interpretation magnetischer Anomalien durch Modellkörper geschieht bevorzugt nach der indirekten Methode (trial und error). Dieses von Hand aufwendige Verfahren läβt sich mit Hilfe der Ausgleichsrechnung nach der Methode der kleinsten Quadrate Rechenautomaten übertragen.Die allgemeinen Grundlagen des Verfahrens werden beschrieben. Wesentliche Voraus-setzungen sind:〈list xml:id="l1" style="custom"〉1)die Annahme bestimmter Körperformen2)das Vorhandensein von Näherungswerten der Unbekannten (Lage, Magnetisierung etc.)3)eine genügend groβe Anzahl von Meβwerten, um den Ausgleichsprozeβ durchführen zu können.Die Vorteile der Methode sind:〈list xml:id="l2" style="custom"〉1)weitgehende Automatisierung und schnelle Arbeitsweise bei Verwendung von Rechenautomaten2)Ermittlung der Fehler der UnbekanntenDie Methode wurde angewandt auf die Interpretation 2-dimensionaler ΔZ- und ΔT-Anomalien. Drei Körpertypen werden dem Rechenprogramm zugrunde gelegt, und zwar die unendliche und endliche diinne Platte und der Kreiszylinder. In die Maschine ein-gegeben werden nur die Meβwerte. Die Interpretation erfolgt im einzelnen in folgenden Schritten:〈list xml:id="l3" style="custom"〉1)Ermittlung von Näherungswerten2)Bestimmung der Körper bester Annäherung3)Iteration für den Körper bester Annäherung.Die Maschine gibt die Endwerte der Unbekannten (Lage, Einfallen, Magnetisierung etc.) mit Angabe der mittleren Fehler sowie die hierzu gehörigen Modellanomalien aus. Diese Endwerte werden einem Zeichenautomaten übergeben, der die gemessene Kurve, die theoretische Kurve und die gesuchten Modellkorper zeichnet.Interpretationsbeispiele werden vorgeführt.

Notizen: In the first part, the author, recalling the principle of d/c current measurements, shows by means of some examples, different experimental results relative to the induced polarization phenomenon. He presents the case of the negative induced polarization which can be explained by geometric effects. He gives some examples of saturation curves and discusses the problem of the linearity of the I.P. phenomenon. Then he shows some aspects which demonstrate that I.P. decay curves do not always conform to the general law. He concludes by showing the influence of the current electrodes, the position of which, relative to the polarizable bodies, may alter the shape of the I.P. anomalies.In the second part, the author presents different case histories of I.P. mineral surveys where I.P. is compared to other geophysical methods and drilling results.

Notizen: Magneto-telluric measurements were carried out at a group of eight sites, from Braunschweig to Lübeck, to determine the resistivity values associated with the North German conductivity anomaly. The data were analyzed for scalar and tensor apparent resistivities over the period range 5–2000 seconds. The results in general indicate very conductive (˜I Ω-m) sediments overlying a resistive basement which is strongly lineated.Interpreted basement depth (˜6 km) is compatible with published seismic refraction data. Principal conductivity axes in the basement appear to be directly related to trends of salt domes and major troughs. A major change in axis direction occurs near the center of the North German anomaly.

Notizen: Results of gravimetric surveys can be interpreted by comparing the Bouguer field values with master curves based on simplified geological models. It has been shown in a previous paper how this procedure can be transformed into routine processes which can be computerized. The application of this method has yielded useful results in detailed gravity surveys.The present paper discusses the application of the same interpretation principles to magnetic data. After some modifications, the method elaborated for the gravimetric data can be used for the interpretation of magnetometric survey results. Magnetometric-tectonic maps are obtained which show the structural picture by common geological symbols. In the case of faults, the dimensions of depth of burial and throw are indicated on the maps.The method is illustrated by an example where these procedures have been applied to gravimetric and magnetometric data of the same area. Two different maps are obtained: One shows the tectonics according to density contrasts and the other map depicts the tectonic situation on the basis of magnetic susceptibility contrasts.

Notizen: A theoretical solution is obtained for the problem of a two-layer earth with transitional boundary. In practice, the transition layer can stand for the weathered zone in hard rock areas where the degree of weathering diminishes with depth. Master curves and tables of data are presented for the case when the lower half-space is infinitely resistive.

Notizen: Digital aeromagnetic profiles recorded with a high accuracy can be filtered with an electronic computer. Linear filtering is not very efficient, because the frequency spectrum of a given anomaly is very wide. But other methods are possible which, through a step by step analysis of the profile, leave some categories of anomalies unaltered while they remove the others completely.Our method uses as a criterium the width of the anomalies; it distinguishes and processes differently “bell-shaped” and “multi-legged” anomalies. Some examples of the use of the method are shown.

Notizen: Bei reflexionsseismischen Untertagemessungen werden die Geophonaufstellungen und die Schußpunkte im Bergwerk angelegt. Die Möglichkeiten hierzu sind durch das Grubengebäude und durch die Meßmethode eingeschränkt. Ungeachtet dessen werden oft Aussagen über die Lage eines Reflektors im dreidimensionalen Raum benötigt. Es müssen daher hohe Anforderungen an die Konstruktionsmethoden gestellt werden können.Zunächst ist es im Hinblick auf die Meßgenauigkeit erforderlich, zwischen günstigen und ungünstigen Anordnungen von Aufstellungen und Schußpunkten zu unterscheiden. Diese Frage wird in der Einleitung kurz behandelt.Die Beschreibung von allgemeingültigen Konstruktionen ist das eigentliche Ziel dieser Arbeit in ihrer hier vorliegenden Fassung. Es wird gezeigt, wie mit Hilfsmitteln der Darstellenden Geometrie beliebig im Raum gelegene ebene reflektierende Flächen-elemente nach der Spiegelpunktmethode konstruiert werden können. Dies kann, je nach der Korrelation, auf zwei verschiedenen Wegen geschehen, die in den Abschnitten I und 2 getrennt beschrieben werden.Im ersten Abschnitt wird der Fall zweier Geophonaufstellungen behandelt, welche wie die Schenkel eines Winkels aneinandergefügt sind. Sie können von einem beliebig gelegenen Schußpunkt aus beschossen werden (siehe den linken Teil der Abbildung I). Anhand eines Beispiels aus der Kaligrube Salzdetfurth bei Hildesheim wird dies etwas näher erläutert. Bei bekannter Streichrichtung oder bei bekanntem senkrechten Einfallen des Reflektors führt bereits eine Geophonaufstellung zum Ziel und es vereinfacht sich die Konstruktion.Der zweite Abschnitt bringt den Fall zweier nicht notwendig zusammenhängenden Aufstellungen, die nicht in einer gemeinsamen Ebene zu liegen brauchen. Durch Anwendung der Technik des Gegenschießens gelingt es auch so, ein reflektierendes Flächen-element zu erhalten (siehe den rechten Teil der Abbildung I). Naturgemaß ist die Lage der beiden Schußpunkte hierbei nicht beliebig.

Notizen: In a paper presented at last year's Amsterdam meeting (viz. Geophysical Prospecting 14 (1966), 3, 301–341), J. R. Schopper derived formulas relating formation factor, permeability and porosity, by means of a statistical-network approach and by treating the electric and hydraulic resistance analogously.The model of the porous medium consists of a network of branch resistors, their values being statistically distributed about a mean Ro with a relative standard deviation (variation coefficient) s. A properly defined total resistance R of the network can be expressed by the relationship:〈displayedItem type="mathematics" xml:id="m1"〉(1′)〈mediaResource alt="image" href="urn:x-wiley:00168025:GPR277:GPR_277_m1"/〉Here α is a geometrical factor dependent only on the shape of the network (i.e. the number of meshes in the longitudinal and transversal direction), ε is a characteristical constant dependent only on the individual mesh shape (i.e. the number of nodes and branches within a mesh).This network constant ε enters the equations relating formation factor, permeability and porosity, ε had been found to be in the range zero to one by calculating algebraically two special limiting network cases. However, for a better understanding of which value exactly this constant will have in actual porous media, networks with various mesh shapes have to be treated generally.Because of the basically statistical approach, the networks have to be large so that a general algebraic treatment is precluded. Hence numerical methods using digital computers must be applied.The determination of the total resistance R of any resistance network leads to the problem of solving a system of linear, inhomogeneous equations; i.e. Ohm's law written in matrix form:〈displayedItem type="mathematics" xml:id="m2"〉(2′)〈mediaResource alt="image" href="urn:x-wiley:00168025:GPR277:GPR_277_m2"/〉〈list xml:id="l1" style="plain"〉(R) is the matrix of the coefficients, composed of the individual branch resistances.(I) is the column vector, its components being fictitious circular mesh currents.(U) is the inhomogeneity column, its components being source voltages within the individual meshes.The matrix (R) has characteristic properties that depend on the mesh shape on the one hand and on the number and arrangement of the meshes on the other hand. With the regular arrangement of identical meshes investigated here, the matrix always has a banded structure and is symmetrical with respect to the main diagonal, positive definite, and non-singular.For the numerical determination of the wanted constant ε the coefficients matrix is provided with values having a known distribution. Here, in particular, a computer-generated pseudorandom homogeneous distribution is used. The system, of equations is solved for R by a modified Cholesky method. Equation (1′) can then be solved fore. The main features of an ALGOL program written for this purpose and optimized with respect to storage space requirement and computer time are discussed.Networks of triangular, square and hexagonal meshes have been investigated. The results are discussed.

Notizen: The accuracy of the magnetic registrations of a new field station constructed at Niemegk Observatory is described. The most important aspects for the construction were good mechanical stability, a good constancy of all physical data and the fact, that the station is ready in the field for solid registration ere long. The apparatus was proved during geomagnetic survey in the field, especially in view of the variability of the geomagnetic variations. The results obtained by field work and by comparison at observatories are good. It is planned to enlarge the registrations by means of photocellcompensators.Der Plan zur Konstruktion einer transportablen und schnell aufstellbaren geomagnetischen Feldregistrierstation geht schon auf das Jahr 1939 zurück. In diesem Jahr wurde von Fanselau ein Plan für eine solche Station den Askania-Werken in Berlin-Friedenau unterbreitet und zur Konstruktion empfohlen. Der Krieg verhinderte eine rasche Durchführung der Fertigungsarbeiten, so daß erst nach Beendigung des Krieges die Askania-Werke den auf diesen Vorschlägen beruhenden Magnetographen fertigen konnten. Am Adolf-Schmidt-Observatorium für Erdmagnetismus in Niemegk wurden dann weitere geomagnetische Feldregistrierstationen entwickelt [1, 2, 3]. Bei der Konstruktion des Gerätes wurde bewußt auf Robustheit und Stabilität Wert gelegt, während der Gesichtspunkt, ein möglichst leichtes und kleines Gerät zu haben, nicht so sehr im Vordergrund stand. Von dem neuen Typ der Station sind inzwischen schon eine ganze Reihe von Exemplaren in Betrieb genommen worden, so daß es an der Zeit ist, einige Bemerkungen über Zuverlässigkeit in der Konstanz der Skalen- und Basiswerte sowie über andere instrumentelle Daten der Geräte zu machen. Auf Grund eingehender Messungen am Observatorium und im Gelände liegt genügend umfangreiches Material vor, um diese Fragen sicher beantworten zu können.

Notizen: Several papers have been published in which the electromagnetic anomalies are described that are produced by conductive ore bodies of different shapes. No publications are available, however, in which the electrical current pattern is described that is induced in these ore bodies. Yet an insight in this electrical current pattern would be valuable in order to assess the possibilities of different electromagnetic techniques, for instance with regard to the determination of the dip and of the depth extent of plate shaped ore bodies.In the present paper computations are given of the electrical current pattern induced by an oscillating magnetic dipole in a semi infinite plate shaped orebody of infinitesimal thickness, in which the penetration depth of the current is infinitesimal to a higher order than the thickness of the plate. The computations are based upon an equation derived by Wesley for the magnetic field produced in these conditions, combined with the relation between the electrical current density in a laminar sheet and the magnetic field produced by this current at the surface of the sheet.The results of the computations show that, if the horizontal distance between the dipole source and the sheet is sufficiently small, the maximum current density of the return current may occur at a depth below the upper edge of the sheet which is appreciably smaller than the depth of the upper edge of the sheet below the surface. The depth of the return current becomes large when the horizontal distance between the source and the sheet is large.

Notizen: An aquifer test and analyses of water samples, showed that the anomalous water quality of a municipal well was caused by leakage from a nearby abandoned well tapping another aquifer.

Notizen: Electric-analog or digital-computer models are used to compute the effect of ground-water withdrawal or recharge on streamflow. The results can be generalized on a map showing lines of equal elapsed time. The lines indicate the time of recharging or discharging that is needed to affect the streamflow by a given fraction of the amount pumped or injected. The generalization is based on the similarity in shape of the relations between pumping time and stream depletion for (1) semi-infinite homogeneous aquifers drained by a straight, fully penetrating stream, and (2) complex heterogeneous aquifers. Response curves from a model reflect the combined effect of stream sinuosity, irregular impermeable boundaries, areal variation in aquifer properties, and imperfect hydraulic connection between the stream and aquifer. The elapsed-cime lines are identified by sdf (stream depletion factor) values. These values can be calculated from observations made on an electric-analog model and then may be used in a digital-computer program for determining the effects of ground-water pumping or recharge on streamflow.

Notizen: Hydrologic systems in arid lands normally include a recharge area in mountains and a discharge area in lowlands often with an intermediate area of lateral flow between recharge and discharge areas. This system is often modified by local geologic, climatic, and physiographic factors. Most water-supply, contamination and disposal problems arise from a combination of features superimposed on this system by concentration of population and agricultural activity in the discharge areas. Also most of our data on the system comes from the lowlands and little data is available from the recharge areas.In the Great Basin two general categories of ground-water flow systems are recognized: (1) local flow systems where drainage areas are usually small, flow paths are relatively short, interbasin flow is uncommon, springs have large fluctuations in discharge, water temperature is low, and concentration of Na, K, Cl, and SO4 is low, and (2) regional flow systems, where drainage areas are large, flow paths long, interbasin flow common, springs have large discharge, and the water is characteristically of higher temperature and contains higher concentrations of K, Na, Cl, and SO4. Hydrologic approaches used, in addition to conventional methods, include hydrologic budget, water-potential, and water-chemistry studies. Although detailed delineation of most flow systems in Nevada has not been accomplished, integration of hydrologic, geologic, and chemical methods allow approximate portrayal of many systems, both local and regional.Adequate methods upon which to base planning for optimum development of water resources in desert basins are now available. A conceptual model of optimal ground-water reservoir development illustrates how to determine optimum use of storage and perennial yield provided the use to which the water is to be put and the time of withdrawal are known.

Notizen: In 1965, a ground-water recharge facility was constructed and placed in operation to forestall an impending water shortage at Minot, North Dakota. The facility is unique in that the rate of recharge to a buried sand and gravel aquifer is augmented by perforating an overlying bed of clay using hydraulic connectors (gravel-filled bored holes) in conjunction with an open-pit excavation. The connectors were drilled by typical well-boring techniques and the open pit was excavated by common construction methods. The recharge technique made it possible to add about million gallons per day of water to underground storage with a total capital investment of about $200,000. The alternative originally proposed was a 50-mile long pipeline to Garrison Reservoir, at a 1959 estimated cost of $12,000,000. The recharge technique employed at Minot should have wide application in the ground-water industry in areas where natural recharge to permeable deposits is impeded by overlying beds of low permeability.

Notizen: A totally new concept, called the Deep Tunnel Plan for Flood and Pollution Control, is being implemented by the Metropolitan Sanitary District of Chicago. The plan envisions temporary storage of combined sewer overflows in a system of tunnels excavated in solid rock, deep under the City. After the end of a storm, the stored water would be pumped to the surface where it would be treated to remove pollution before being discharged into the waterways.Early planning studies indicate that the most favorable location for the tunnels is the Galena-Platteville Dolomite which is the uppermost member of the Cambrian-Ordovician aquifer. The protection of this highly-developed aquifer from any possible contamination is therefore mandatory for the feasibility of the Deep Tunnel Plan.Preliminary investigations using an electric analog model, constructed on the basis of available data, indicate that aquifer protection can be provided by a system of recharge wells which would maintain flow into the tunnels at all times. Further detailed studies are in progress to verify and refine those preliminary conclusions. These studies include (a) detailed exploratory drilling; (b) controlled aquifer tests in selected zones; (c) pumping tests for specific capacity in the zone to be tunneled; (d) recharge injection tests; and (e) analog model analysis for future effects of the tunnels and recharge operations.

Notizen: The interdisciplinary graduate program in hydrogeology at the University of Idaho is described. The curriculum is structured to permit the design of individual study programs which are in keeping with multiple use concepts. Flexibility sufficient to permit courses to be taken in several fields which support the students' major area of research is provided. This flexibility is maximized by the offering of two degree options. Discussion of a number of the research projects at the University illustrates several of the types of problems now being studied.

Notizen: The University of Connecticut well field is located in a sand and gravel ice-contact stratified drift aquifer which fills the Fenton River valley to a depth of about 60 feet. The water that supplies these wells consists of captured ground-water underflow which would normally discharge into the Fenton River, and water induced directly into the aquifer from river flow by pumping. Measurements of streamflow made at three weirs installed in the Fenton River adjacent to two of these pumped wells show the influence of wells on streamflow. Approximately 34 percent of the water pumped from the wells was stolen from the river via induced streambed infiltration, although this figure varies in accordance with pumping. Water-level measurements in 30 observation wells installed in the aquifer around the pumped wells show that the cones of depression spread underneath the river, following coarse-grained partially buried eskers. The fact that the water table is detached from the river and is below the streambed near the pumped wells is explained by the low vertical permeability of the streambed in contrast to the horizontal permeability of the rest of the aquifer. The streambed is unable to recharge the aquifer with as much water as the aquifer can carry away. Time-drawdown pumping test plots show no effect of the river.

Notizen: A resistance network analogue is used to study the early stages of a pumping test in an unconfined aquifer. The results are compared with an alternative analysis due to Boulton (1965) and a good agreement is obtained.Unlike the theoretical analysis the analogue technique is versatile and can easily be used to study pumping tests with nonidealized boundary conditions, e.g., partially penetrating wells can be simulated. Thus the analogue method of analysis could prove to be a more realistic method for studying pumping tests than standard analytical techniques.

Notizen: Coarse granular deposits in preglacial river valleys are an important source of ground water on the Canadian prairies. Such an aquifer can commonly be modeled by an infinite-strip leaky-artesian aquifer. Test results can be analyzed, future drawdowns predicted, and safe yields estimated by applying the standard leaky-artesian formula in conjunction with image-well theory, making due allowance for well-loss factors.This paper develops basic formulas required for safe yield estimation for an array of n wells located on the axis of an infinite-strip leaky-artesian aquifer. In general, determination of safe yield for each well depends on the solution of n simultaneous linear or nonlinear equations. For certain symmetrical arrays, however, the number of equations to be solved is approximately halved. A linear equation will apply for any well if flow adjacent to the well bore always obeys the Darcy law for all pumping rates of interest. If all n equations are linear, they may be solved by the methods of matrix algebra; if not, a trial-and-error solution must be adopted.The method is illustrated by an application to a 6-mile stretch of a buried-valley aquifer near Edson, Alberta. The numerical coefficients in the system of equations are first derived and the equations then solved to obtain estimated 20-year safe yields for well arrays containing up to 38 equally spaced wells.

Notizen: In 1966 more than 50 billion gallons of water was pumped daily from an estimated 10 to 15 million water wells in the United States. This was more than one-sixth of the national withdrawal of water. On the basis of past rates of increase, a much greater future use of ground water is suggested. Our annual investment in water wells is one-half to three-quarter billion dollars, not including pumps and plumbing. In 1964 approximately 436,000 new wells were drilled; however, less than 1 percent of these wells were logged by any geophysical means. The application of _ge_o.phy.sical well logging to ground-water hydrology is comparable to its use in petroleum exploration in the 1930's; however, we can take advantage of equipment and interpretation techniques developed in the oil industry that are available now for use in ground-water investigations.Although most petroleum well logging techniques may be utilized in hydrology; modifications in equipment and interpretation are necessary because of basic economic and environmental differences between petroleum and ground-water evaluation. If logging is to be widely applied to ground-water exploration and evaluation, the expense of equipment and services must be reduced. Fortunately, this can be accomplished, because most water wells are not as deep as oil wells and the temperatures and pressures are lower.The Water Resources Division of the U. S. Geological Survey is conducting research on the application of borehole geophysics to ground-water hydrology. The following logging devices are utilized in the evaluation of ground-water environments: spontaneous potential, resistivity, gamma, gamma-gamma, neutron, radioactive tracer, flowmeter, caliper, fluid resistivity, gradient and differential temperature, and sonic velocity. Lightweight logging sondes and control modules are operated by one man, either on a vehicle-mounted 6,000-foot logger or on a suitcase-mounted 500-foot logger. An inexpensive magnetic tape system has been developed and is used routinely for log recording and playback.If commercial well logging service is to be widely used in ground-water exploration and development, water well contractors, and State and municipal agencies must be educated on the advantages of obtaining more information from each hole drilled. It will be necessary also to demonstrate how well logging can provide much of this information. In addition, the well logging industry must adapt their equipment and services to the requirements of ground-water hydrology. The need for additional logging capability in this field exists at the present time and is expected to increase. Hopefully industry will be able to fill the gap.

Notizen: Heavy development in certain areas of the United States and the growing shortage of additional, readily available water supplies therein have forced planners and hydrologists to resort progressively to more elaborate water-supply systems. Among the most elaborate and most expensive systems proposed to date are the various plans for. transferring water toward the south from northward flowing Arctic rivers. A considerable portion of this water would be utilized for the expansion of already heavily urbanized areas.Meanwhile, many of the densely populated areas experiencing water shortages are subjected to other, perhaps more complex problems which appear to be, at least in part, a product of their increasing size. Therefore, the expenditure of large sums to supply them with water for indefinite growth appears to merit scrutinous study.An alternative approach designed to minimize both water diversion costs and problems associated with over-populated areas is the stimulation of development in carefully selected regions well endowed with water and other natural resources. One such area and several of its attributes are discussed herein.

Notizen: A gravity survey covering 250 square miles and including the Walnut Gulch watershed at Tombstone, Arizona has been conducted. The watershed is one of the experimental areas of the Southwest Watershed Research Center, Agricultural Research Service in Tucson, Arizona.The gravity survey method was selected as the geophysical method that would give a regional picture of the subsurface geology before making extensive surveys by the seismic. refraction method. Basically, the gravity survey method detects and measures variations in the earth's gravitational force. These variations are associated with changes in rock and alluvium density near the surface. Many geologic structures of interest in watershed ground-water hydrology cause disturbances in the normal density distribution which give rise to anomalies.The geology of the watershed is typical of Basin and Range province and contains deep basin fill deposits surrounded on the east, south, and southwest by igneous intrusives, volcanics, and sedimentary rocks. Concealed border faults may have a decided effect on the hydrology of the watershed.Four base stations were established and 360 gravity stations occupied by a Worden Educator* gravimeter loaned from the Geophysics Laboratory of the University of Arizona. Bench marks and large scale topographic maps served as control. Raw field data were reduced to the simple Bouguer anomaly values through the use of a computer program.The gravity survey reveals a 16-mgal. gravity low over the east-central portion of the watershed. This low is interpreted as indicating that about 3200 feet of low density alluvium underlies the area at this point. Gravity highs are associated with mountain ranges and igneous plugs where the more dense rocks occur.

Notizen: Recent increased interest in subsurface disposal of industrial liquid wastes in Illinois has shown the need for both geohydrologic and engineering criteria and State regulatory policies for evaluating proposed installations, with the object of protecting other resources, chiefly potable ground water.Favorable geohydrologic conditions–specifically the presence of a variety of permeable formations that contain nonpotable water and are well confined from shallow to great depth–make waste disposal by wells feasible in much of the southern two-thirds of Illinois. Natural safeguards permit disposal wells to be planned with conventional engineering precautions and only a minimal program of preoperational testing.In much of the northern third of the State, the permeable rocks contain potable water to great depth, and there is moderate to high development of the ground-water resource because of urban and industrial concentration. Exhaustive testing, substantial proof of acceptable site conditions, and incorporation of optimum engineering safeguards are considered necessary before the State regulatory agency can authorize installation.

Notizen: Comparative costs of ground water were needed for comprehensive planning of water resources development in the Susquehanna River basin in order to appraise the feasibility of alternative sources of water supply. Log-normal plots on logarithmic-probability paper that represented specific capacities adjusted to 180 days of pumping were used to estimate well yields and costs of obtaining the ground water from each of 65 potential aquifers. The 25, 50, and 75 percent probability of occurrence of the specific capacities of successful wells were used in the calculations. The estimated well yields at these probabilities of occurrence were obtained using hypothetical well designs and selected drawdowns. Ground-water costs for the estimated or design yields were calculated using amortized costs of well construction, electrical power costs, and maintenance costs, all obtained from standard sources.The calculated well yields and costs for the 25 to 75 percent probability interval range from 15 to 9,000 gpm (gallons per minute) and from $0.004 to $0.11 per thousand gallons of design yield. The yields and costs group according to aquifer rock type. The calculated costs decrease with increasing well yield and the available yield depends upon the aquifer rock type available. Representative costs per thousand gallons of design yield for selected yields from aquifers composed of different rock types analyzed are: 50 gpm −$0.060 for shale and interbedded sandstone and shale, and $0.050 for metamorphic rock; 100 gpm - $0.043 or shale and interbedded sandstone and shale, $0.037 for metamorphic rock, and $0.032 for carbonate rock; 500 gpm—$0.020 for sandstone, $0.015 for carbonate rock, and $0.012 for glacial sand and gravel; and 1,000 gpm —$0.009 for glacial sand and gravel. Differences in cost to obtain the same yield from different rock types are primarily due to differences in electrical power costs as determined by differences in pumping water levels.If used with caution, the generalized yield and cost estimates for aquifer rock types may have usefulness in estimating ground-water costs and yields in similar humid areas. They are primarily useful for planning and comparative purposes, but not for the actual design of engineering Projects.

Notizen: Hazards to ground water may result from adding to water which may infiltrate the soil, or to the soil through which water percolates, wastes from man's life processes; his industrial and commercial activity; or his use of water, fertilizers and pesticides in agriculture. From experimental data it is evident that particulate matter, including bacteria and viruses, do not move far with percolating water in a soil system. The chemical products of biodegradation of organic wastes, however, with a few exceptions such as phosphates, move quite freely and hence reach ground water. Since they are no different than the compounds found in ground waters the effect of domestic use of water is generally to increase the concentration of salts normally present in such waters. From the vast spectrum of compounds produced by the chemical industry and used in industry and commerce comes hazards to ground-water quality such as metal ions, phenols, tar residues, brines, and exotic organics which may through accident, carelessness or waste-water discharge contaminate ground water. Mineralization with nutrients and soluble soil fractions, and possibly, pesticide residues are the hazards from agricultural use. Leaching from solid waste landfills is possible under poor long-term management and might involve chemicals, iron, and various earth minerals. It is concluded that the most serious hazard is the buildup of dissolved solids to levels inimical to beneficial use.

Notizen: In this paper, basic design principles for disposal wells are set out and then exemplified by discussion of two recently constructed wells for disposal of very corrosive refinery waste. One well is designed for 700 gpm of waste containing 4200 ppm hydrogen sulfide. The other is designed for 50 gpm of waste containing 32 percent hydrochloric acid. Both wells are in the Gulf Coastal Plain and are completed in a deep, unconsolidated fine sand containing salt water. Screens fabricated from exotic metals were incorporated in the design. Unique combinations of materials were used for the casing.It is pointed out that oil field type completions are often used in disposal well construction, which usually results in low specific injection capacity, high operation and maintenance costs, and short useful life of the hydraulic structure.

Notizen: A supply of good-quality water is our most critical natural resource, for our municipal growth and an increasingly healthy industrial base. The economic viability of our farms depends upon it. The locating and development of this resource is the province of the hydrogeologist.The hydrogeologist is more than just a ground-water geologist, for he deals with water in virtually every geologic situation, above-the water table as well as below it, and at the surface as well as underground.The hydrogeologist must of course possess the necessary background in the allied sciences and fluid mechanics, and should know something of the social science aspects of water decision-making. He must be able to work closely with the civil and sanitary engineers, and he must be able to make himself understood to planners.In performing his work he has a responsibility to society, and this is equated with a responsibility to his profession. As Martin Van Couvering has said, the respect that our profession deserves “cannot be bought or solicited; it has to be earned by the right kind of performance.”

Notizen: Water well drillers gather information essential to recovery tests as part of normal procedure. Added effort could yield additional valuable information. More care in measurement of water levels both before and after a period of pumping can be used with ground-water formulae to determine approximate well efficiency.A relationship exists between the ability of an aquifer to perform (transmissibility) and the specific capacity of a well. By means of pumping tests, both transmissibility and specific capacity may be measured. The theoretical specific capacity can be obtained based on the measured transmissibility. Well efficiency may be estimated from a comparison between measured specific capacity and theoretical specific capacity.Tests of wells owned by the City of Houston, Texas, were selected for analysis. Test results were compared with curves showing theoretical relationships. From the comparison, wells in the Houston area are not completely developed. It may not be economical to develop a well to 100 percent efficiency, but theoretical relationships should be used in well development.

Notizen: An induction-tuned device was designed and tested under a variety of well casing conditions. It can detect casing lengths to within 0.4 to 2.0 inches for casing ranging from 2 to 14 or more inches in diameter which are made of either magnetic or nonmagnetic metals. A casing separation as small as one inch is detectable for 12-inch diameter casing and a four inch or more separation is detectable for 4-inch I.D. casing. These values indicate the range in sensitivity expectable when determining casing separations.Dial readings in microamps are indicated as the ptobe is raised or lowered within a well bore. Readings vary depending whether the probe is centrally located or located to one side. The maximum and minimum dial reading is established for a given casing diameter at the start of a survey. A consistent change in dial reading from previous valves indicate a casing diameter change.The sensing element is a coil whose inductance is changed by varying its proximity to any metallic conductor. A coil and capacitor in parallel make a tuned circuit resonant at 3 K.C. The device includes a transistor in a phase shift oscillator, and a second transistor which acts as a current amplifier, a 0–100 μa d. c. meter driven through a bridge rectifier, capacitors, and other elements. Twelve to 14 volts at 4 to 6 milliamperes or less than 0.1 watt is sufficient to power the device.A maximum meter reading is obtained by adjusting an oscillator to the resonant frequency of the probe. Lowering the probe into a well casing detunes the probe, changing its impedance and the meter reading.All electrical elements are standard except the probe and all materials can be purchased for about $40.00 exclusive of the reel and cable assembly.

Notizen: The electrical resistivity method has been a valuable tool used in the discovery of ground-water recharge facilities with percolation capacities in excess of 100,000 acrefeer per year. The procedures used in doing the field work and the methods of plotting the data are described using a typical area where studies were made. Correlations of soil types, recharge rates, and resistivity data for Santa Clara -County are included. Ground-water level data from observation wells are used to measure the regional and long-term effects of the ground-water recharge program.

Notizen: Buried valleys are classified into two main types — those valleys completely buried by glacial drift, without present streams along their courses (Type I), and those partly buried or partly exhumed, usually with present streams along their courses (Type II). If a stream is flowing mainly in a Type II valley, the bottom of which is deeply buried by drift, local areas where the stream is cutting bedrock are postglacial channels of derangement. Postglacial channels of derangement, which often can be recognized on a topographic map, reveal that a buried valley (often Type I) exists nearby.

Notizen: Ground water of acceptable quality is commonly interspersed with water of inferior quality. Water of inferior quality may be naturally occurring salty water commonly underlying fresh water, or it may be enclaves of contaminated water from wastes that lie in the fresh-water bodies. Disposal of wastes on and in the ground and pumping of water from wells cause a dispersion of contaminated water; migration of contaminated water toward wells may be spontaneously induced by the natural hydraulic gradient, or it may be induced artificially by the cone of depression about one or more wells. Economic methods of determining precisely the boundary zones between contaminated and uncontaminated water are not available. Much reliance is placed on monitoring wells.A prerequisite to monitoring is a synthetic hydrogeologic framework or model in which the behavior of the contaminated water is conceived. Such a conceptual model, using pertinent data that are available, helps to assess the need for monitoring and to guide a monitoring program for optimum results. Unplanned, indiscriminate monitoring of water from wells is expensive, inefficient, and fallible. The need for monitoring will increase in the future; yet, the proper objective is to improve the technology of determining the distribution of contaminated water so that monitoring can be minimized and conducted with optimum results.

Notizen: Ground-water development frequently provides a means whereby tremendous new economic opportunities are opened up. If supplies are overdrawn (mined) the ensuing regional economy may be able to afford replacements from more costly sources. In the United States the Salt River Valley of Arizona and the valleys of California provide examples.Two cases are treated in this paper, Israel and West Pakistan. In Israel, besides furnishing more than half of the basic source of water supply, ground-water development provides opportunity for both quantity and quality management, which makes possible use of surface supplies and reclaimed sewage as firm rather than marginal sources. This development will permit the total water resource of this small country, where agricultural production ranks among the world's most efficient, to be utilized effectively down to almost the last drop by the mid 1970's. Israel must then look to desalted water from the sea for-further expansion of its over-all water supply.In West Pakistan a combination of level terrain and leaky canals since about 1890 led to threatened waterlogging and salinity of more than 25 million acres of irrigated land, even though supplies were less than half adequate for good productivity. By the 1950's low yields and increasing population threatened starvation. However, initiation of ground-water development, first by the government and later by private enterprise, has, since 1960, led to construction of 3,500 governmental tube wells of about 3 cfs capacity and 30,000 private tube wells of slightly less than 1 cfs capacity.Results have been dramatic. Agricultural production and use of fertilizer are rapidly increasing, and opening of well development to private enterprise is providing the irrigator with benefits of free competition for his water custom which he did not previously enjoy. Ultimately, besides providing full supplies for an estimated 26 to 30 million acres, drainage and salinity problems will be mitigated if about 50 million acre-feet are pumped each year from ground water including about 28 million acre-feet to be mined from a reserve of about 1,900 million acre-feet. With some difficult surface storage development due to terrain, mining may eventually be reduced. Though an eventual technological solution for the continuing overdraft is not now in sight, perhaps an economy may be built which can afford such a solution when the time comes.

Notizen: The effects on flow of a nearby stream from pumping a well can be calculated readily using dimensionless curves and tables. Computations can be made of: (1) the rate of stream depletion at any time during the pumping period or after the cessation of pumping; (2) the volume induced from the stream during any time, both during pumping or after the cessation of pumping; and (3) the effects, both in rate and volume of stream depletion, of any selected pattern of intermittent pumping. Sample computations illustrate the use of the curves and tables. An example shows that intermittent pumping may have a pattern of stream depletion not greatly different from a pattern for steady pumping of an equal volume.The residual effects of pumping, that is, effects after cessation of pumping, on streamflow may easily be greater than the effects during the pumping period. Adequate advance planning that includes consideration of residual effects thus is essential to effective administration of a stream-aquifer system.

Notizen: The Piedmont is underlain by igneous and metamorphic rocks, from which it is difficult to locate quantities of ground water adequate for municipal and industrial purposes. Ground-water occurrence and movement in the Piedmont is controlled by topography, recharge and discharge, rock type, fracture systems, and type and thickness of saprolite.Approximately 12 square miles in the Heflin area, Cleburne County, Alabama, were included in this study. Fractures within bedrock are the most effective avenues for ground-water movement in this area, but domestic supplies can be produced from saprolite and alluvium overlying bedrock. Thick saprolite contributes to bedrock-fracture production by absorbing water from streams and rainfall and releasing it slowly to underlying fractures.Seismic methods were used with geologic, hydrologie and topographic data to locate and define favorable areas for drilling. As shown on the seismic sections, faults or fracture systems appear to correlate with depressions on bedrock surfaces associated with thick saprolite zones. Seismic data indicate twenty-five prospective areas for test drilling.Resistivity data were used to confirm seismic depth to bedrock, and to locate gravelly zones in buried stream channels. Some of the buried alluvium is thick enough to be considered a potential aquifer.Twenty-five prospective areas are indicated by geophysical work in the Heflin area. A proposal to drill 10 wells to evaluate the most promising of these areas is presently being considered.

Notizen: The Floridan aquifer in northeast Florida is comprised of limestone and dolomite beds of Tertiary age. These formations in ascending order are: the Cedar Keys Formation of Paleocene age; the Oldsmar Limestone, Lake City Limestone, Avon Park Limestone, and the Ocala Group, all of Eocene age; locally the Suwannee Limestone of Oligocene age; and limestone and sand beds at the base of the Hawthorn Formation of Miocene age. The top of the Ocala Group ranges in elevation from 100 feet above sea level to 550 feet below sea level throughout the area.Except in the western part of the area where the Ocala Group is at the surface, impermeable beds in the Miocene to Recent deposits overlie the aquifer and confine the water under artesian pressure. Hard, impermeable beds within the aquifer separate the water-bearing zones. The coefficient of transmissibility ranges from about 50,000 gpd/ft (gallons per day /foot) to more than 1,000,000 gpd/ft and the coefficient of storage ranges from 1.5 × 10−4 to 1.7 × 10−2 in areas where the water in the aquifer is under artesian conditions.The estimated annual recharge averages one-half mgd (million gallons per day) in the western part of northeast Florida and 45 mgd in the south central part. Limited recharge also occurs throughout the central and eastern part of northeast Florida by downward leakage of water through the overlying confining beds. The coefficient of leakance of these confining beds ranges from about 1.7 × l0−2 to 1 ×10−3 gpd/ft3.Natural discharge occurs by perennial and intermittent springs and upward leakage through the confining beds in the areas of artesian flow. Artificial discharge by wells occurs principally in the farming, urban, and industrial areas in the eastern part of northeast Florida.Between 1940 and 1962 artesian pressures declined from 5 to 25 feet throughout the eastern part of northeast Florida.Seasonal declines of artesian pressure of 5 to 10 feet in the farming areas resulted in temporary increases of chloride content of water of 200 to 500 ppm (parts per million). The chloride content of water in the aquifer in the vicinity of Jacksonville and Fernandina has increased from 22 to 1400 ppm in wells more than 1,400 feet deep. Thus far, impermeable zones below the fresh water have prevented serious salt-water contamination in shallower wells at Jacksonville and Fernandiua.

Notizen: The significance of the work associated with the protection of aquifers against salt-water encroachment, primarily in the area of Southern California goes far beyond the solution of this local problem. Engineers and planners are now able to turn to the record of extensive practice in the field of artificial ground-water recharge to modify the concepts based on theoretical studies. Thus depleted aquifers, anywhere, can be evaluated as potential reservoirs for the storage of ground water – evaluated as to cost, legal complications, and administrative design in the same way, and on the same basis, that surface-water impoundments are evaluated.The work done on the West Coast in artificial recharge increases the number of alternates that are available to the water planner and, in the long run, this may be the most significant output of the engineering, construction, and operation of the barrier projects.

Notizen: Electrical earth resistivity and soil temperature surveys have been conducted in the vicinity of four sanitary landfills in northeastern Illinois to test the possibility of detecting and tracing any chemical or temperature alteration of ground water by leachates from buried refuse. Reference data on water quality, levels, and movement were provided by a system of monitor wells drilled for a hydrogeologic study of the landfills.The resistivity survey, which was in homogeneous silty sand outwash, traced mineralized water from the landfill for a distance of more than 1000 feet. Apparent resistivity values were one fourth those obtained from unaffected areas. Interpretations of direction of ground-water flow and location of discharge boundaries from the geophysical data agree vith interpretations based on the monitor well data.The soil temperature survey indicated the presence of a halo of higher temperatures around the landfill and indicated areas of surface recharge.The geophysical surveys show, in general, that chemically altered water is traceable in uniform earth materials where the depth of the water table is constant.

Notizen: The U. S. Geological Survey, on behalf of the U. S. Atomic Energy Commission, performs a broad range of geologic and hydrologic studies related to underground nuclear explosions at the Nevada Test Site. One phase of the studies involved extensive geophysical logging and hydraulic testing in deep exploratory holes at Pahute Mesa, Nevada Test Site. Various geophysical logs and hydraulic testing techniques used in the study are described in this paper.Interpretations of logs and logging techniques depend on factors such as rock characteristics in a particular area, drilling methods, and the objectives of the hydrologic investigations. From experience gained at Pahute Mesa, some qualitative data on rock lithologies and hydraulic conditions in the borehole may be determined by electric, caliper, temperature, and fluid resistivity logs. Quantitative data on the major water-yielding intervals in the borehole are obtained from radioactive tracer or spinner surveys. Interpretations of the geophysical logs have been verified by isolating specific zones in the drill holes with inflatable packers and spacers. These intervals were tested by injection or swabbing of fluid and measuring the resultant change in water level caused by fluid outflow from or inflow to the interval of rock isolated by the packers.

Notizen: Portable pumping equipment for sampling of wells, discribed by written text, photographs, and a detailed drawing, has been constructed by the Robert S. Kerr Water Research Center.The equipment can sample to depths of 300 feet at pumping rates ranging between 7 and 14 gallons per minute, with rate variation dependent upon sampling depth.The unit is convenient in size and easy to operate because only one line has to be handled during its operation. This is a wire-reinforced rubber hose that supports the submersible pump, contains the electrical cable, and conveys water.

Notizen: The landlocked Republic or Upper Voira lies in the heart of West Africa and comprises a wide lareritic plateau at the south edge of the Sahara Desert. From south to north, the rainfall decreases from about 1.200 mm. to less than 500 mm.; the evaporation increases from a low of 1,945 mm. to 3,385 mm.; and temperatures from 30° C to 34° C.Latentic rocks occur as surficial deposits over much of the reconnaissance area, and generally are ferruginous, hard, and cemented. The underlying bedrock consists primarily of granite and granodiorite with lesser amounts of metamorphics.The so-called “under latérite” materials, consisting of the weathering products of the igneous and metamorphic rocks, constitute the principal aquifers in the investigated areas. These clays and sands generally can be counted upon to yield small supplies of water, adequate for at least domestic and stock use. Large-diameter dug wells are used exclusively to tap the thin water-bearing zones. Where 15 meters or more of weathered material occur above fresh bedrock, water can be found and exploited. A “good” well is one which produces 2,000 litersb per hour.The chief importance of the bedrock as a source of water is that it may yield at least a small quantity of water from fractures at most localities where ir is below the water table.Water in sufficient quantity and adequate quality is not now available to raise the standards of living in the 631 villages in the areas visited. Most of the immediate need can be met by developing ground water from the weathered material through large-diameter dug wells.

Notizen: A theory of the lateral decrease of grain size and bed thickness with increasing distance of downwind transport is developed for ash falls. The theory is based on: the sediment load density of a turbulent slug of fluid, a turbulent diffusitivity coefficient, and the decay of turbulent velocity fluctuations. All three factors are founded on empirical observation and are generally accepted as having widespread applicability to turbulent sediment-fluid mixtures. The theory yields good qualitative agreement with observational data.

Notizen: Photographs and descriptions of quartz sand grains from soils, paleosols and silcretes show that grain shape can be modified by solution in situ. Dissolution is attributed to solutions rich in organic molecules present in weathering profiles, and commonly results in rounding of protuberances and re-entrants on grains. The incidence of this process may vary with climate. It is postulated that solution rounding during weathering plays an important role in shaping quartz sand grains in general, its significance varying with climate. This postulate, which remains unconfirmed, has considerable implications for the interpretation of textural maturity of sandy sediments. If true, super-mature sands may be as much a climatic indicator as an indicator of tectonic quiesence.

Notizen: Of the several uncommon types of large-scale cross-stratification encountered in Late Holocene upper-pointbar sandy deposits of the Rhine, one is examined in detail. This type is structurally bipartite as it consists of a relatively coarse-grained, upper interval of large-scale foresets, which indentate with the oppositely dipping small-scale foresets in the underlying finer interval. The lower interval is usually of smaller, and incidentally of the same thickness as the upper one. Together they constitute the so called “interwoven set”.The interwoven set is regarded as formed by a mega ripple (dune) with in front of it, a simultaneously active system of small-scale, oppositely moving, ripples propelled by the backflow branch of the mega ripple's lee-side vortex.Comparison of dip, strike, and principal bedding-plane (= horizontal) sections brought to light dissimilarity in the crestline orientations of the mega-ripple and backflow-ripple systems. The latter's oblique, or incidentally perpendicular orientation with respect to the mega-ripple front indicates a conspicious component of lateral water movement, which in the present outcrop was consistent from the left to the right, for the observer looking down(main)stream.It is suggested that this lateral water movement is due to the radial (transverse) flow in the bend of a meandering river. From the sense of the radial flow the river's bend configuration (here: right hand turn) can be inferred. Relative wander velocities of mega- and backflow-ripple systems were deduced from the configuration in a horizontal section made through the interaction zone of the two structural intervals.

Notizen: A new method is presented for the measurement of grain orientation in clastic sediments.The method is based on the principle that when an inclined beam of light passes through an elliptical hole in a plate of a certain thickness, the amount of light passing through depends on the orientation of the long axis of the ellipse with respect to the direction of incidence of the light beam. If such a plate is rotated in its own plane, the amount of light passing through will fluctuate. Such fluctuations are larger the greater the eccentricity of the ellipse, the amount of light passed being maximal when the long axis coincides with the plane of incidence of the light.If the plate contains many holes, which need not be elliptical but for the ease of reasoning can be approximated by ellipses, their main orientation direction can be inferred from the maximum intensity of passed light.It is shown in the paper that results of a similar kind can be obtained by using a black and white picture of the grain packing in combination with a mirror. These pictures can be obtained either from thin-sections or from printed replicas of etched polished sections of impregnated samples.The resulting data represent an integrated orientation pattern instead of a long-axis distribution pattern as given by the grain-by-grain counting technique.The new method has been thoroughly checked against the visual counting method. Excellent agreement was observed.

Notizen: Accurate particle-size measurement by sieving requires that consideration is given to particle shape and screen opening size variations. The effect of particle shape has been studied by determining experimentally the probability of passage through each of five woven-wire screens of 35 different mm-sized ellipsoids. These range in shape from T/D= 0.2 to 1.0 and from L/D= 1.125 to 2.625, where T is particle thickness, L is particle length, and D is particle intermediate diameter. Passage tests were performed for both static and dynamic conditions of sieving.A mathematical sieving theory stemming from the idea of particle passing probability is developed. The theory is put to use by computer-simulated sieving of idealized input samples of simple shape make-up. When near-spheres are sieved it is found that a bar-type histogram is a justifiable depiction. For some other more realistic shape inputs, what is obtained are broad, overlapping bell-shaped fraction distributions considerably offset from the nominal openings of the limiting screens. For these distributions, conventional representation in histogram form is incongruous.The treatment presented contains allowance for screen opening size variations. Some apparently polymodal distributions are probably explainable as a result of unsuspected differences between the screens used and an ideal screen series.

Notizen: Examination of the primary sedimentary texture of rocks and sediments by X-radiography can be extended to include the study of bioturbation and burrowing by living organisms. This technique involves making time-lapse X-radiographs while the animals are in the process of disturbing the sediment.Artificially and naturally stratified sediments are contained in plexiglass aquaria connected to a continuously flowing seawater system. The burrowing animals to be studied are introduced into these aquaria and the effect of their activities on the sediments is recorded by X-radiography over a period of hours, days or weeks.

Notizen: Results of X-ray textural studies of dolomite and the clay minerals in the Marl Slate and of siderite from the top of the Mansfield Marine Band are interpreted in terms of the possible diagenetic development of the re-crystallized carbonates in these two rocks. From computer processed (1014) fabrics of the two trigonal carbonates it is deduced that there is a c-axis preferred orientation concordant with the normal to the stratification. An early diagenesis in this oriented mode must be a function of both a threshold stress difference in a non-hydrostatic stress field (in effect a necessary minimum depth of burial) and also of the presence of connate solutions. The existance of a minor percentage of dolomite oriented with the rhomb faces parallel to the stratification probably reflects an even earlier crystallization within the top few metres of sediment, when the confining pressures and pressure differences were of insignificant amplitude. It is concluded that a higher rate of sedimentation associated with the Coal Measure sequence is responsible for the singular preferred orientation of the siderite.

Notizen: Statistical methods in micro-biofacies This paper deals with statistical methods as applied to micro-biofacies problems. The samples for the tests were taken from four quarries in Jurassic and Cretaceous limestones in northwestern Germany. The calculations are based on acetate-peels. Two millions of figures were considered.The percentages of nine organic and nine inorganic components were calculated, hierarchically. In the beginning, the results were plotted as segments of circles. This way of representing the percentages of components just shows the general distribution of the main components.A more detailed picture can be given by plotting the distribution expressed in percentage, in reference to the distance of sampling points. The figures show the importance, not of the individual amplitudes, but of the average values of all amplitudes measured in one layer. Therefore, the change of the average amplitude represents a micro-biofacies change of the layer under consideration. The measurements have shown that the differences in the distribution of the organic and inorganic components within the individual layers are not greater than those between the single layers.Correlation-analyses had no positive results. Also tests of inhomogeneity did not give satisfying results. By decision-analyses (discriminance-analyses), however, it was possible to show small differences in the distribution of the components within the individual layers.Differentiations of the homogeneity and of the micro-biofacies setting can be demonstrated by the intersections of the curves of the decision factors (=discriminance factors) and of the values of the arithmetic mean and sliding mean. By applying the X2-test and/or variance-analyses, the boarder lines between fields of homogeneity can be shown accurately.Information about the homogeneity of the tested samples and the number of samples necessary for getting representative data, can be calculated from sequence tests.

Notizen: Small, dendritic structures in probable playa lake sediments of the basal Keuper Marl in Leicestershire are interpreted as habit-modified halite pseudomorphs.

Notizen: Wave-formed ripple marks in the nearshore zones of the Baltic Sea (tideless) and North Sea (tidal) exhibit a unidirectional internal lamination identical to that of current ripples. This holds true whether the ripples are symmetrical or asymmetrical. In most cases wave-formed ripple laminae dip toward shore and can thereby provide a shoreline direction indicator when found in ancient sediments. The sediment transport direction, however, may be other than in the foreset laminae dip direction, and cross-lamination as a sediment transport direction indicator should be used with caution.Ripple height, wave length and the orientation of the ripple internal structure are dependent upon both the orbital diameter and the velocity of the positive component of oscillation of the waves forming them. The thickness of the individual laminae making up ripples is highly dependent upon sediment grain size; the role hydrodynamics plays is problematic.

Notizen: Book reviewed in this article: Ground Wcter Problems. E. Eriksson, Y. Gustafson and K. Nilsson (Editors). Geochemie der Sedimente. E. T. Degens. Current Ripples—Their Relation to Patterns of Water and Sediment Motion. J. R. L. Allen. “Meteor” Forschtrngsergebnisse, Reihe C, 1. GeoIogie und Geophysik. E. Seibold und H. Closs Tertiary Sea-Level Fluctuations. W. F. Tanner (Editor). Amphibotes. W. G . Ernst. Introduction to Paleolimnology — Developments in Sedimentology, 11. C.C. Reeves Jr.

Notizen: Although supplied to rivers, grains of about 1–6 mm diameters are notably deficient in fluvial deposits because they are more readily entrained and more rapidly transported than grains of larger or smaller size. Very coarse sand and fine gravel are rarely found in shallow-water sediments for the same reason. Currents, mainly of wave origin, concentrate these grains in beaches, where they are present in more-than-ordinary abundance.

Notizen: The Río de la Plata Drainage Basin is the second largest in South America, with more than 75% of its discharge provided by the Paraná River and the remainder by the Uruguay River. Erosion rates, and silt- and clay-size mineralogy indicate that most of the basin loads are provided by the mountainous environment-type.

Notizen: The Cape Fear Formation rests on basement rocks in the Cape Fear River valley of the North Carolina Coastal Plain. It consists primarily of graded muddy sand—sandy mud couplets. A typical sequence for each couplet starts with a disconformity, followed by a basal gravelly sand with megaclasts of quartz and clay pebbles, cross-bedded sand, and finally a structureless mud bed. Fossils are absent. The sand fraction is poorly sorted and the sediment has a clayey texture. Structures and textures suggest that each couplet is the product of a current waning from an upper flow regime, to the lower part of a lower flow regime. Turbidity current and fluvial origins are considered. Cross-bedding and textural criteria indicate that normal, low-density currents are responsible for at least part of the typical sequence. A normal fluvial origin is rendered less likely by the absence of mud cracking, root casts, and textural criteria of a partitioned subaerial environment. Stratigraphic and geochemical considerations suggest that the formation may have been deposited in estuaries or coastal lagoons; if so, the stratification may record sedimentation during the periodic flushing of saline water by river floods.

Notizen: Analysis of influx and efflux of sediment and water to and from the ocean and of residence times of the elements indicates that the oceans and atmosphere are in a steady state with respect to erosion and sedimentation. A detailed examination of the ocean-atmosphere model is needed to see how the system worked in the geological past. Weathering is characterized primarily by the absorption of H+ by silicates and secondarily by liberation of SiO2, alkalies and HCO3—to the oceans. The H+ is supplied mainly by the H2O-CO2 system via the ionization of H2CO3 but some is supplied by HCI from volcanic emanations. Weathering of carbonate rocks results in the same absorption of H+, releasing Ca2+, Mg2+, and HCO3—. Sedimentation, silicate reconstitution, and diagenesis are seen as the reverse of weathering in that H+ is released and SiO2 and alkalies are precipitated from solution. Thus a constant H+ release is necessary to keep constant the CO2 pressure of the atmosphere by transforming the HCO3—of the ocean into CO2+ H2O. The sedimentary products that are part of the steady-state model are reconstituted silicates (degraded clay minerals that become diagenetically altered to less hydrous, more siliceous illites and chlorites), limestone (precipitation reverses limestone weathering), salt (uses up alkalies), and chert (uses op free SiO2). It is concluded that the major site of silicate reconstitution is not on the open sea floor but in coastal subsiding sedimentation belts in which high-grade diagenesis takes place and whose formation waters are ultimately connected with the ocean and so can buffer it. The obvious consequences of the model are that the global amounts of carbonate, reconstituted silicate, salt, and chert must be related in a systematic way for any time interval in which the system is steady. To keep CO2 constant, the total of carbonate precipitation and silicate reconstitution must be conserved. Similarly, salt precipitation and silicate reconstitution must be related to keep alkali removal constant. Finally, chert must be related to silicate reconstitution so that all silica released by weathering is removed from the ocean. A careful examination of the stratigraphic record is needed to objectively determine from such parameters whether the steady-state system has always been operating much as today or whether there have been major secular changes or periodic perturbations.

Notizen: Electron microprobe analyses of skeletal carbonate structures in coralline algae and pelecypods show that the magnesian content of the calcite depends on skeletal growth rates. Growth rate is a function of certain variables, including water temperature, light, and physiological cycles. The Mg-content of calcareous sediment from specific organisms is not, therefore, mainly dependent on water temperature, as is generally believed, but also on the other factors affecting growth.

Notizen: The basic differences between mechanical analysis of sand by Ro-Tap sieving and by settling in a sedimentation balance are discussed. The Groningen balance can continuously and rapidly record settling times of the grains (50–1,000 μ) of a 1.5-g sample with a maximum recording and reading error of about 2%.The theory of sieving is not fully developed yet, nor has the theory of settling of sand-sized particles been adequately expressed by any mathematical law. The drag coefficient (CD) and Reynolds number (Re) relation often used to derive diameter (d) from settling velocity (v) in this size range, are calculated from experimental data on diameter and velocity. Conversion of settling times to “sedimentation diameters” with the help of experimental curves for single, spherical quartz grains and their comparison with the corresponding “sieve diameters” are often found to be unsatisfactory in the case of natural sands, because shape and density variations of every individual grain in a sample can never be taken into account. Therefore, the use of settling velocity as a new grain parameter is advocated.

Notizen: Ripple, flaser and lenticular bedding are well known, but for describing profiles, they are not sufficiently defined and subdivided. It is, therefore, the intent of the following text to present such a definition and classification.The classification contains the following main bedding types and intermediary types (Fig.1):〈inlineGraphic alt="inline image" href="urn:x-wiley:00370746:SED99:SED_99_f1" location="image_n/SED_99_f1.gif"/〉〈list xml:id="l1" style="custom"〉1Cross-bedding with flasers.2Flaser bedding, subdivided in: (a) simple flaser bedding; (b) bifurcated flaser bedding; (c) wavy flaser bedding; (d) bifurcated wavy flaser bedding.3Wavy bedding.4Lenticular bedding with thick or flat lenses, subdivided in: (a) continuous lenticular bedding (with connected lenses); (b) broken lenticular bedding (with single lenses).

Notizen: This report describes an investigation by means of laboratory tests of the critical shear stress and bed erosion as a function of time and bed shear stress for a sediment consisting of alternating sand and clay layers 0.1–3 cm thick (sand-clay laminae). This type of deposit occurs quite frequently in estuaries and tidal inlets. The tests were carried out on an original bed deposited in an estuary.The critical shear stress and the degree of erosion in relation to time for the sand-clay lamination were found to agree in order of magnitude with those for clay layers. The resistance to erosion of the sand-clay lamination is therefore comparable with that of clay layers.

Notizen: Turbidity currents are thought to be the agency responsible for the transport and deposition of the sediments known as turbidites. The way in which such currents may arise has been studied experimentally in a glass-walled tank.The starting point of the experiments was setting the sediments in motion by raising their pore pressure via a shock or vibration. This was achieved in the experiments by striking the metal bottom of the tank with a mallet.The response of a heap of homogeneous sand to such a shock was merely to change the angle of its slope. If a layer of sand was draped over a core of coarser, homogeneous sand, sliding occurred along the plane of permeability contrast and the less coarse sand was deposited at the toe of the slope. When the layer consisted of kaolin, which has a much lower permeability than sand, sliding again took place, but the clay subsequently mixed with the water and was moved along the bottom of the tank in the manner attributed to turbidity currents.An attempt is made to set up a scaling rule for experiments of this type and the consequences that such a rule may have in subsequent study are briefly discussed.

Notizen: Book reviewed in this article: Statistische Methoden für Erdwissenschaftler (Statistical Methods for Earth Scientists). D. Marsal. E. Schweizerbart Petroleum Microbiology. J. B. Davis. Geology of Shelf Seas. D. T. Donovan (Editor). Oliver Boyd

Notizen: In the Kinderscout Grit (Namurian, R1c) of the southern half of the Central Pennine Basin, England, there occur tabular, isolated, cross-bedded sets of coarse sandstone, between 4 and 40 m thick. The sets are up to 1 km wide and the foresets, in plan, are convex in the direction of dip. The sets interfere laterally to form extensive sheets. Foresets dip at up to 27° and are sometimes themselves internally cross-bedded in trough-shaped sets, here termed “intrasets”. The large sets are thought to be deltaic sedimentation units rather than sandwaves. In the delta top environment in which these sets were deposited, a high rate of bed-load sediment supply and a sudden deepening were required to initiate the sets.Medium-scale cross-bedding, thought to have been laid down in migrating, fluviatile channels overlies the large-scale sets and represents the topset member of the sedimentation units. From the spatial arrangement of the large- and medium-scale cross-bedding, it is possible to distinguish those areas where deposition took place during the deepening, from those where it took place essentially after the deepening. The causes of the deepening, which must have been on at least a basinal scale, may have been eustatic or tectonic.

Notizen: The sparitic Plassen Limestone (Tithonian, N.K.A., Upper Austria) The sparitic Plassen Limestone (Tithonian, N.K.A., Upper Austria) shows various types of calcite-fabric. We distinguish fibrous, fibrous-drusy, and drusy cavity fillings. While the fibrous fabric can be interpreted as submarine precipitation soon after sedimentation, an explanation of the drusy calcites as submarine or subaerial precipitation remains an open question. There are, however, indications of subaerial influences. For the origin of the dismicrites an interpretation as shrinkage structures may be considered.