Diskordante Tektonik

Zusammenfassung Die Verfolgung tektonischer Strukturen in die Tiefe ist nur bei kontinuierlicher Verformung einfach. Physikalische oder strukturelle Änderungen innerhalb der sich verformenden Körper, sowie Änderungen in der Richtung der verformenden KrÄfte, bedingungen diskontinuierliche Änderungen in den erzeugten Strukturen, z. B. Scheitelverschiebung, Rückverformung, DurchprÄgung überwÄltigter Strukturen.

---

To pursue tectonical structures beyond observations is simple only if deformations are continuous. Changes of physical or structural properties of rocks, as well as changes in the direction of transforming forces, create discontinuous alterations within thus generated structures, e. g. displacement of apex, retrograde transformation, penetration of subdued lower structures.

---

Résumé Le prolongement des structures tectoniques en profondeur n'est simple que dans le cas de déformations continues. Des changements de propriétés physiques ou structurales durant les déformations à l'intérieur des corps tectoniques, ainsi que des modifications dans la direction des forces actives, produisent des transformations discontinues dans les structures engendrées, p. ex. déplacements des sommets des anticlinaux, déformations en retour, rejeu de structures anciennes et leur pénétration dans les structures superposées; etc.

---

. , : .: , , .

     

Seismische Anisotropie des oberen Erdmantels und Intraplatten-Tektonik

Specially planned explosion seismic measurements in the oceans provided conclusive evidence that the velocity of P_n-waves depends on the azimuths of the direction of propagation through the upper mantle. The orientation of this azimuthal anisotropy suggests a close connection with the generation of the oceanic lithosphere: in the Pacific the maximum and minimum velocities are measured in a perpendicular and parallel direction to the axis of the oceanic ridges respectively. The observed anisotropy is so strong that a number of models for the generation of anisotropy can be discarded. The most likely cause is a preferred orientation of minerals. The generation of the anisotropy can be simulated in the laboratory under P-T-conditions of the upper mantle. The influence of the rate of deformation can be studied as well. A recent analysis of explosion seismic data in Southern Germany suggests that the continental upper mantle possesses also a velocity anisotropy dependent on azimuth.     

The dynamics and thermodynamics of precipitation loading

A one-dimensional, time-dependent numerical cloud model is used to analyze the factors in the dynamic and thermodynamic equations which lead to a steady-state or nonsteady-state solution for the cloud vertical motion, buoyancy, precipitation, and cloud water fields. ‘Bulk water’ microphysical techniques are used for the cloud, rain, and hail variables. An atmospheric sounding from a severe storm situation is used as initial and environmental conditions, yielding model updrafts of 40 m sec^?1 maximum and more than 10 m sec^?1 over the entire cloud region. ‘Early conversion’ of the cloud water to rain leads to loading of lower portions of the updraft by rain, the formation of appreciable amounts of hail by freezing of the supercooled rain, and subsequent loading of the middle and upper portions of the updraft so that the updraft erodes throughout the cloud depth and the cloud dissipates, yielding a vigorous rain shower. A delay in the conversion of the cloud water to rain results in a steady-state solution, no rain or hail falling through the updraft. A two-dimensional cloud simulation of this same case shows rain and hail in the upper cloud regions recycled in the two-dimensional flow into the updraft near cloud base and a breakdown of the updraft with resultant rainout (negligible hail reaching the ground). The breakdown of the updraft has profound effects on the temperature field within the cloud, causing the lapse rate to deviate from the steady-state condition and approach the initial environmental conditions. The results emphasize the fact that the local change in temperature (and other dependent variables as well) is not independent of the vertical velocity, in general. This has implications for the interpretation of measurements made within clouds.     

A method to determine crystallization temperatures of hydrated crystals by intracrystalline oxygen isotope effects

The fractionation of the oxygen isotopes between water molecules from different sites in CuSO₄ · 5H₂O has been measured for crystallization temperatures of 25, 40 and 50°C. The temperature dependence found provides a basis for the determination of crystallization temperatures from such intracrystalline oxygen isotope effects; also for hydrated crystals of mineralogical and geological interest. Necessary suppositions for the application of this method are discussed.     

210Po and 210Pb distributions in ocean water profiles from the Eastern South Pacific

Two ocean profiles from the Peru Basin from regions with different surface productivities were analyzed for total²¹⁰Pb and²⁰¹Po to evaluate the influence of particulates in the water column on their distribution. Comparison with a published²²⁶Ra profile for the region was made. The profile closest to the coast, where upwelling and productivity are high, shows depletion of²¹⁰Pb relative to²²⁶Ra at all depths, with particularly marked excursions from radioactive equilibrium at the surface and in the bottom water.²¹⁰Po appears to be deficient relative to²¹⁰Pb at depth as well. Mean residence times in the deep water, relative to particulate removal from the water column to the sediments, of about 100 years for²¹⁰Pb and about two years for²¹⁰Po are indicated. The profile northwest of the upwelling region shows the²²⁶Ra²¹⁰Pb²¹⁰Po system close to equilibrium at all depths to 1500 m (except for the effect of atmospheric²¹⁰Pb input seen at the surface.