Upper bathyal trace fossils document palaeoclimate changes

Marine trace fossils were investigated in a 102-m cored section that covers −14.379 to −14.142 Ma (Middle Miocene). Long-term climate trends are perfectly reflected by changing trace fossil communities of the upper bathyal (−200 to −300 m). The community structure is expressed in abundance of taxa based on probabilities of time concordance between the deposition of the sediment and the time, when the traces were produced. Changes in community structure precisely parallel the increasing δ¹³C isotopes during the Middle Miocene climate transition and perfectly mirror oscillations in solar insolation in both amplitudes and phase. Furthermore, the density stratification of the seawater caused by wind-induced currents is reflected in trace fossil communities. Additionally, the dependence of ichnotaxa abundance from threshold values in the sedimentation rate could be demonstrated.     

Radiative damping of trapped gravity waves in the solar atmosphere

The radiative damping of trapped gravity waves in an optically thin atmosphere is studied for a stratified Boussinesq fluid. The character of the atmospheric eigenmodes depends on the distribution of the Brunt-Väisälä frequency N and the radiative relaxation time . The calculations for simple layer models show that if N is large over some finite fraction of the trapping region, then modes of long lifetime can exist. In order to suppress gravity waves entirely, it is necessary that N < 1 over the entire trapping region. Qualitative application of the results to the solar atmosphere leads to the conclusion that gravity wave eigenmodes of the solar atmosphere, although damped, are by no means eliminated by radiative effects.     

Helium and neon isotopes in stratospheric particles

Abstract— Helium and neon isotope ratios were determined for 16 interplanetary dust particles (IDPs) collected in the stratosphere. The concentration of helium observed varied greatly from particle to particle, with the highest values approaching those found for lunar surface fines and some gas-rich meteorites. With the exception of one particle, for which the ³He/⁴He was (1.45 ± 0.05) × 10^?3, the remainder of the particles had ratios falling between 1.4 and 3.1 × 10^?4, with an average of (2.4 ± 0.3) × 10^?4, substantially less than is associated with the solar wind or observed in average lunar fines or in lunar fines having sizes comparable to those of the IDPs studied. The average ²⁰Ne/²²Ne found was 12.0 ± 0.5. Only three reasonably reliable ²¹Ne/²²Ne ratios could be determined, and for these the average was 0.035 ± 0.006. The isotopic ratios appear to preclude the presence of any appreciable amount of cosmic ray-produced spallogenic products. The high ⁴He concentrations observed for some of the particles, approaching those observed for lunar surface grains, suggest they were not heated to high temperatures and degassed as they descended in the earth's atmosphere. From Flynn's study of the dynamics of IDPs entering the earth's atmosphere this could mean they entered the atmosphere at relatively low velocities, and hence may be primarily of asteroidal rather than cometary origin.     

Die Kristallstruktur von BeSO4

Zusammenfassung BeSO₄ kristallisiert im BPO₄-Typ, der sich von der Cristobalitstruktur herleitet. a=4·49 A, c=6·90 A, c/a=1·536. Die Atomabstände sind: S–O=1·50 A, Be–O=1·56 A.     

Nutrient dynamics in the Pomeranian Bay (southern Baltic): Impact of the Oder River outflow

The Pomeranian Bay is a coastal region fed by the Oder River, one of the seven largest Baltic rivers, whose waters flow through a large and complex estuarine system before entering the bay. Nutrients (NO₃ ⁻, NO₂ ⁻, NH₄ ⁺, Ntot, PO₄ ³⁻, P_tot, DSi), chlorophylla concentrations, oxygen content, salinity, and temperature were measured in the Pomeranian Bay in nine seasonally distributed cruises during 1993–1997. Strong spatial and temporal patterns were observed and they were governed by: the seasonally variable riverine water-nutrient discharges, the seasonally variable uptake of nutrients and their cycling in the river estuary and the Bay, the character of water exchange between the Pomeranian Bay and the Szczecin Lagoon, and the water flow patterns in the Bay that are dominated by wind-driven circulation. Easterly winds resulted in water and nutrient transport along the German coastline, while westerly winds confined the nutrient rich riverine waters to the Polish coast and transported them eastward beyond the study area. Two water masses, coastal and open, characterized by different chemical and physical parameters and chla content were found in the Bay independently of the season. The role of the Oder estuary in nutrient transformation, as well as the role of temperature in transformation processes is stressed in the paper. The DIN:DIP:DSi ratio indicated that phosphorus most probably played a limiting role in phytoplankton production in the Bay in spring, while nitrogen did the same in summer. During the spring bloom, predominated by diatoms, the DSi:DIN ratio dropped to 0.1 in the coastal waters and to 0.6 in the open bay waters, pointing to silicon limitation of diatom growth, similar to what is being observed in other Baltic regions.     

Synneusis of Kilauea Iki olivines

Olivine phenocrysts in the picritic scoria that erupted from Kilauea Iki in 1959 occur as glomeroporphyritic aggregates of 2–16 crystals. The compositions and three-dimensional textures of the olivines vary within an aggregate and within individual lapilli. The attachment of crystals from different environments indicates that these aggregates formed by synneusis — the swimming together of crystals. Most of the crystals are attached along faces with their a crystallographic axes parallel and their c axes either parallel or perpendicular, so that the structural mismatch and interfacial energy are minimized. Observed facial attachments are consistent with fluid dynamical interactions of crystals falling with their large {010} faces horizontal. The aggregates formed in a liquid-rich magma. Rough computations suggest that the minimum aggregation time could be on the order of minutes. Aggregation of very small crystals suggests that the yield strength was less than 3 dynes cm^–2. The textures of the aggregates are similar to those of cumulate peridotites.