A modified profile method for determining the vertical fluxes of NO,NO2, ozone,and HNO3 in the atmospheric surface layer

A modified profile method for determining the vertical deposition (or/and exhalation) fluxes of NO, NO₂, ozone, and HNO₃ in the atmospheric surface layer is presented. This method is based on the generally accepted micrometeorological ideas of the transfer of momentum, sensible heat and matter near the Earth's surface and the chemical reactions among these trace gases. The analysis (aerodynamic profile method) includes a detailed determination of the micrometeorological quantities (such as the friction velocity, the fluxes of sensible and latent heat, the roughness length and the zero plane displacement), and of the height-invariant fluxes of the composed chemically conservative trace gases with group concentrations c ₁=[NO]+[NO₂]+[HNO₃], c ₂=[NO₂]+[O₃]+3/2·[HNO₃], and c ₃=[NO]–[O₃]–1/2·[HNO₃]. The fluxes of the individual species are finally determined by the numerical solution of a system of coupled nonlinear ordinary differential equations for the concentrations of ozone and HNO₃ (decoding method). The parameterization of the fluxes is based on the flux-gradient relationships in the turbulent region of the atmospheric surface layer. The model requires only the vertical profile data of wind velocity, temperature and humidity and concentrations of NO, NO₂, ozone, and HNO₃.The method has been applied to vertical profile data obtained at Jülich (September 1984) and collected in the BIATEX joint field experiment LOVENOX (Halvergate, U.K., September 1989).     

The origin of carbonate mud in isolated carbonate platforms of Belize,Central America

Carbonate mud from three small isolated carbonate platforms of Belize (Central America) is largely a product of the breakdown of skeletal grains. The composition of the 63-20- and 20-4-µm fractions of 37 samples was determined by point counting under SEM; composition of the <4-µm fraction was assessed qualitatively under SEM. The 63-4-µm fractions are dominated by fragments of mollusks, the codiacean alga Halimeda, and other skeletal types. About one-third of the particles in the 63-4-µm fractions remained unidentified, probably due to obliteration of diagnostic features by early recrystallization processes such as micritization. Nanograins (<1 µm) and short (3-5 µm) aragonite needles are most common in the <4-µm fraction. These grains are interpreted to be largely fragments of codiacean algae (Halimeda, Penicillus). The 20-4- and <4-µm sediment fractions are composed of 80 and 75% aragonite on average, respectively. Trace element composition of strontium averages 7,900 ppm in the 20-4-µm fraction and in codiacean algae samples, and 5,600 ppm in the <4-µm fraction. Geochemical (trace element) data also argue against inorganic aragonite precipitation within the water column, and favor a skeletal origin. The lower strontium contents in the <4-µm fraction as compared with the 20-4-µm fraction may also be a consequence of early recrystallization processes.     

Der Basaltvulkanismus des Djebel Haroudj Ostfezzan/Libyen

A geological map of Djebel Haroudj is presented which shows the distribution of volcanoes and six major basalt flows over an area of approximately 45,000 square kilometres. Differences between the flows are based on age rather than petrographic composition. The oldest flows most probably erupted in the late Pliocene, though it is possible that locally flows of Miocene or even Oligocene age are present. The middle flows most probably occurred during the Pleistocene. The absence of erosional forms and drainage indicates that the youngest flows are of post-pluvial, Holocene age. The zones of volcanic activity at Djebel Haroudj are related to three major tectonic elements of very different ages (see alsoKlitzsch 1966 a): the early Paleozoic southern Haroudj uplift, the western edge of the Mesozoic Tibesti-Sirte uplift, and the south-eastern prolongation of the Hon graben fault system of late Cretaceous to Tertiary age.     

Shatter cones produced experimentally by impacts in limestone targets

Experimentally produced impact craters in limestone targets displayed millimeter-sized shatter cones within crater spallation zones. The craters have been produced by accelerating spherical metal projectiles by means of a light-gas gun. Variation of the impact velocity showed that at about 3 km/s shatter cone formation starts and is reproducible at any higher impact velocities. In most cases the cone apices were pointing in the direction of the impact center. The occurrence of shatter cones directly at the target surface (spallation zones of craters) does not support a theoretical model on shatter cone formation published by Gash (1971).     

Sur la paléoflore post-carbonifère de la bordure est du Bassin de Mourzouk (Libye)

Until recently the age of the continental sediments overlaying marine strata of Carboniferous age at the Murzuk Basin was unknown and long distance correlation was not possible because of lack of correlation criteria. The flora now described allows, for the first time, to identify the age of parts of this strata. Together with new sedimentological criteria of subdivision worked out by R.Glaeser, H.Kallenbach and I.Zöller which will be published later, the paleobotanical investigations contribute towards a final subdivision of these continental sediments. The terms “Nubian Series”, and “Posttassilien” will be abandoned, because they are useless within the area concerned. The creation of correlatable stratigraphical data is an important prerequisite for groundwater and mineral exploration within the large areas covered by these strata. Along the eastern Murzuk Basin these sediments containFilicophytae, Pteridophyllae,Pteridospermaphytae, Cycadophytae andConiferophytae. At Jebel Ben Ghnema the upper part of the lower third of the continental sediments contains plants which are known from triassic strata in Europe, India, North America, South America, South Africa, and Asia. At Jebel Ben Ghnema the top of the strata contains Jurassic plants known from Europe, North America, and Asia. Almost 300 kilometres further South at Jebel Ati near the top of these continental sediments plants of Jurassic age were found, too. It seems that the development of this flora has taken place under a generally warm and dry climate with wet seasons. From the paleophytographical point of view the flora described is of great interest, because it contains coexisting species of the Northern and Southern hemisphere. The Jurassic flora is comparable to that known from adjacent basins in Algeria and Egypt, and to flora known from Virginia.     

Zr contents of glaucophane-bearing meta-basalts of Western Crete,Greece

Chemical analyses of hornblendes from different regional metamorphic terrains and from rocks of different metamorphic grade have been compared. Hornblendes of lowpressure type are distinguished from hornblendes of high-pressure type by their Al^VI and Si contents. The Ti content of hornblende is shown to increase with metamorphic temperature from the greenschist-amphibolite transition facies to the hornblende-granulite facies.