Measurements of tropospheric OH concentrations: A comparison of field data with model predictions     

D. Perner  U. Platt  M. Trainer  G. Hübler  J. Drummond  W. Junkermann  J. Rudolph  B. Schubert  A. Volz  D. H. Ehhalt  K. J. Rumpel  G. Helas 《Journal of Atmospheric Chemistry》1987,5(2):185-216

Using long path UV absorption spectroscopy we have measured OH concentrations close to the earth's surface. The OH values observed at two locations in Germany during 1980 through 1983 range from 0.7×10⁶ to 3.2×10⁶ cm^-3. Simultaneously we measured the concentrations of O₃, H₂O, NO, NO₂, CH₄, CO, and the light non methane hydrocarbons. We also determined the photolysis rates of O₃ and NO₂. This allows calculations of OH using a zero dimensional time depdendent model. The modelled OH concentrations significantly exceed the measured values for low NO _x concentrations. It is argued that additional, so far unidentified. HO _x loss reactions must be responsible for that discrepancy.  相似文献   

Contemporary and palaeo channel patterns and the late quaternary stratigraphy of Cooper Creek,Southwest Queensland,Australia     

Brian R. Rust  Gerald C. Nanson 《地球表面变化过程与地形》1986,11(6):581-590

Braided and anastomosing channels make up two major coexistent networks in the mud-dominated fluvial system of Cooper Creek, Southwest Queensland. The floodplain is characterized by a system of mud braids operative when floods inundate the whole alluvial surface. Anastomosing channels are inset deeper into the floodplain, operate at modern flows, and transport a traction load of sand. Shallow stratigraphic data show that an underlying sand sheet is unrelated to surface channel patterns and was formed by a system of meandering streams. According to preliminary dates based on thermoluminescence, the change from a sand- to mud-dominated fluvial regime took place between 50 000 and 200 000 years B.P., and probably reflects increasing aridity.  相似文献   

Book reviews     

John A. Couch  Michael T. Ledbetter  Gerald N. Smith  John D. Boon 《Estuaries and Coasts》1986,9(3):229-231

  相似文献   

Processes controlling precipitation of carbonate cement and dissolution of silica in reef and near-reef settings     

Samuel A. Epstein  Gerald M. Friedman 《Sedimentary Geology》1982,33(3):157-171

Carbonate cementation in the surface layer of reefs and beachrock eliminates porosity and partially replaces detrital quartz grains. The uptake and release of CO₂ by photosynthesis and respiration in reef communities cause a shift in the carbonate buffer system of seawater. Field studies and experimentation simulating the natural settings show minimum values of CO₂ (1.9 mmoles 1^?1) and HCO₃^? (2.4 meq 1^?1) in association with maximum values of pH (9.8) and O₂ (> 100% oxygen saturation) in waters covering corals and algae prior to sunset. The converse is true for these variables prior to sunrise, when minimum values of pH (7.6) and O₂ (<66% oxygen saturation) occur with maximum values of CO₂ (2.7 mmoles 1^?1) and HCO₃^? (2.7 meq 1^?1). Experimental tanks containing plain seawater showed almost no diurnal variability in pH (a constant 7.5–7.6) or O₂ (80–90% oxygen saturation) measurements. Seawater adjacent to reef biomass, with elevated pH and supersaturated with calcium carbonate, is periodically pumped into the underlying reef and beach sediments due to pressure-buildups between the reef framework or algal zones and open waters. Carbonate precipitation and quartz dissolution follow. As the system equilibrates, pH values progressively decrease.  相似文献   

Proterozoic aeolian quartz arenites from the Hornby Bay Group, Northwest Territories, Canada: Implications for Precambrian aeolian processes     

Gerald M. Ross 《Precambrian Research》1983,20(2-4)

The Hornby Bay Group is a Middle Proterozoic 2.5 km-thick succession of terrestrial siliciclastics overlain by marine siliciclastics and carbonates. A sequence of conglomeratic and arenaceous rocks at the base of the group contains more than 500 m of mature hematitic quartz arenite interpreted to have been deposited by migrating aeolian bedforms. Bedforms and facies patterns of modern aeolian deposits provided a basis for recognizing two sequences of aeolian arenite. Both sequences interfinger with alluvial—wadi fan conglomerates and arenites deposited by braided streams. Depositional processes, facies patterns and paleotopographic position of the arenites are consistent with modern sand sea dynamics.Distal aeolian facies in both sequences are composed of trough crossbed megasets deposited by climbing, sinuous-crested, transverse dunes. Megasets comprise a gradational assemblage of tabular to wedge-planar cosets formed by deflation/reactivation of dune lee slopes and migration of smaller superposed aeolian bedforms (small dunes and wind ripples). Megasets in the proximal facies are thinner, display composite internal stratification and have a tabular-planar geometry which suggests that they were formed by smaller, straight-crested transverse dunes. Most stratification within the crossbeds is inferred to have formed by the downwind climbing of aeolian ripples across the lee slopes of dunes.Remarkably few Precambrian aeolian deposits have been reported previously. This seems anomalous, because most Precambrian fluvial sediments appear to have been deposited by low sinuosity (braided) streams, the emergent parts of which are prime areas for aeolian deflation. Frequent floods and rapid lateral migration of Precambrian humid climate fluvial systems probably restricted aeolianite deposition to arid paleoclimates. Thus the apparent anomaly may reflect non-recognition and/or non-preservation of aeolianites and/or variations in some aspect of sand sea formation and migration unique to the Precambrian. Reconstruction of the Hornby Bay Group aeolianites using recently developed criteria for their recognition suggests that the latter reason did not exert a strong influence.  相似文献   

Textures of sandstones and carbonate rocks in the world's deepest wells (in excess of 30,000 ft or 9.1 km): Anadarko Basin,Oklahoma—Reply     

Gerald M. Friedman 《Sedimentary Geology》1983,35(2):156-157

  相似文献   

Erhitzungsversuche am Markasit     

Dr. Enno Schubert 《Contributions to Mineralogy and Petrology》1959,6(6):388-398

Zusammenfassung Allen, Crenshaw, Johnston andLarsen (1915) untersuchten den Existenzbereich des Markasits gegenüber thermischer Beanspruchung. Sie konnten eine Modifikationsänderung mit meßbarer Geschwindigkeit his hinunter zur Temperatur von 450° C nachweisen. Umwandlungsversuche bei geringeren Temperaturen waren ergebnislos.Durch Erhitzungsversuche an Erzen von den telethermalen Verdrängungslagerstätten um Aachen wurde gezeigt, daß bei Normaldruck his herab zur Temperatur von etwa 350° C eine Umwandlung mit meßbarer Geschwindigkeit stattfindet. Wahrscheinlich ist also Markasit bei Normaldruck bis 350° C existent gegenüber thermischer Beanspruchung.Die Umwandlungserscheinungen in den verschiedenen Stadien wurden durch Mikrophotographien dargestellt.Als geologisches Thermometer ist das Auftreten von Markasit in natürlichen Paragenesen anwendbar mit folgenden Aussagen:Der mögliche Bildungsbereich der betreffenden Paragenese reicht bei normalem Druck bis zur Temperatur von etwa 350° C.Das Existenzfeld des Markasits gegeniiber rein thermischer Beanspruchung reicht bei normalem Druck bis 350° C, also kann die betreffende Paragenese niemals auf höhere Temperaturen erhitzt gewesen sein.Für die Anregung and fur ihr stets Interesse an meiner Arbeit möchte ich Frau Professor Dr.Schachner and Herrn Doz. Dr.Lindley aufrichtig danken.Auszug aus der Dissertation des Verfassers, TH Aachen 1959.  相似文献   

Der Original-Beerbachit im Odenwald,ein Amphibolit-Hornfels in Pyroxen-Hornfelsfazies     

Siegfried Matthes  Wolfgang Schubert 《Contributions to Mineralogy and Petrology》1971,33(1):62-86

With this petrographic re-investigation of the beerbachite (Chelius, 1892) from Odenwald/Germany geochemical and phase-petrological data are given for the first time.By petrofabric relics (Fig. 7) and geochemical characteristics (Figs. 8–11) is shown that the beerbachite-xenoliths are due to blocks broken down from the surrounding amphibolite series. They are present high grade hornfelses.Beerbachite, porphyroblastic by plagioclase (here porphyroblastic beerbachite, Bbp) (Chelius' Gabbroporphyrit) (Fig. 6) frequently forms marginal zones of beerbachite blocks and is explained as beerbachite-metablastite.Phase relation (Fig. 13) and mineral reactions with increasing metamorphic grade from amphibolite to amphibolite-hornfels (containing hornblende) finally to beerbachite are demonstrated and discussed.The first step may be the mineral reaction: plag_I(An 35–40)+hbl_I+sphene= plag_II(An 50–60)+hbl_II+cpx+opx+magnetite/ilmenite+H₂O. The pyroxene-hornfels facies respectively the orthopyroxene subfacies of the K-feldspar-cordierite-hornfels facies (Winkler, 1967) is only reached with the typical assemblage: plag(An 55–70)-cpx-opx-mt/ilm±(quartz) of beerbachite.On condition that the load correspondends to 3–4 km the maximum temperatures may not have exceeded 720–750° C. This valuation would result from experimental data of Choudhuri and Winkler (1967) of the model reaction: hbl=en+di+an+H₂O, if . The natural conditions will differ from this experimental model because of resp. P _load (p. 81)The very probably required temperature for the mineral assemblage of beerbachite would still be within sub-solidus temperatures of the corresponding model system, according to Fig. 13d. Therefore, the coarse grained plagioclases of Bbp (p. 69) could not be formed from cotectic pockets, too.Finally, convergences and divergences to the beerbachite concept are discussed out of the recent literature.

---

---

Herrn Dr. E. Knauer vom hiesigen Institut danken wir sehr für die Bestimmung des Chemismus zweier Pyroxen-Paare aus Beerbachit bzw. Hornfels mit der Mikrosonde (CAMEGA MS 46), Leihgabe der Deutschen Forschungsgemeinschaft. Den Herren Prof. E. Nickel und Dr. M. Maggetti vom Mineralogischen Institut der Universität Fribourg (Schweiz) und Dr. H. D. Trochim, Mineralogisches Institut der Universität Bochum, verdanken wir Vergleichsproben oder Einsichtnahme in vorhandene Dünnschliffe.  相似文献   

Chlorit-Hornblende-Felse des Bergsträßer Odenwaldes und ihre Phasenpetrologie     

Wolfgang Schubert 《Contributions to Mineralogy and Petrology》1969,21(4):295-310

Ultrabasic metamorphic rocks with typical mineral assemblage of cummingtonitic hornblende+Mg-chlorite+talc (described byMatthes u.Okrusch, 1965, and called “hösbachit”) were found for the first time in Odenwald/Germany. Three steps of metamorphic development can be described: the primary magmatic ultrabasic rock consisted of (1) orthopyroxene (bronzite), clinopyroxene (diallage), poikilitic olivine, and some hornblende. This is indicated by textural relicts, structural and geochemical investigations. A regional metamorphic process under conditions of the staurolite-almandine-subfacies ofWinkler’s andTurner andVerhoogen’s almandine-amphibolite facies transformed this assemblage to (2): cummingtonitic hornblende I+Mg-chlorite I (clinochlore)+talc. The third step followed under more diaphthoritic conditions and brought mineral assemblage (3): tremolitic hornblende II+Mg-chlorite II (pennine)+talc.  相似文献   

Aluminum-26 in meteorites—VII. Ureilites,their unique radiation history     

Laurel L Wilking  Gerald F Herman  Edward Anders 《Geochimica et cosmochimica acta》1973,37(7):1803-1810

Cosmogenic ²⁶A1 activities have been measured by γ-γ coincidence counting in the three ureilites which had not previously been studied. The values in dpm/kg are: Dingo Pup Donga, 38.4 ± 2.4; North Haig, 39.3 ± 4.8; Dyalpur, 55.8 ± 4.8. Five of the six known ureilites thus have lower ²⁶A1 contents, 63 per cent to 77 per cent, than the calculated saturation values, in marked contrast to most other stony meteorites. This cannot be attributed to short cosmic ray exposure ages. Nor do size and depth effects account for the narrow range of ²⁶A1 activities, because a nuclear particle track study indicates that preatmospheric radii were highly variable, from ≥ 40 cm for Goalpara to only a few cm for Dingo Pup Donga. By default, the most likely explanation is that the ureilites had much smaller or much larger orbits than all other stony meteorites.  相似文献