Effects of non-conserved denominators on pearce element ratio diagrams

Pearce element ratios (PER's) have conserved denominators which have not participated in the material transfer processes that cause chemical variations in rocks. Theoretically, there is no truly conserved element (constituent) which can be used as a PER denominator because in every material transfer process all constituents have non-zero concentrations in the phases that are being transferred. Thus, constituents used as denominators of PERs may have undergone at least a small amount of material transfer. This communication investigates the degree to which a non-conserved PER denominator changes the trend of data produced by a material transfer process from that produced by the same process but plotted on a PER diagram with a truly conserved denominator. An equation is developed that utilizes the partition coefficient as the measure of the degree of involvement of the denominator constituent in the phase undergoing transfer. This equation is examined to determine how the magnitude and direction of a PER diagram data trend change with increasing involvement of the denominator constituent in the transferring phase. A set of plagioclase fractionation examples are presented which use different elements as PER denominators and consider the effects that small amounts of these elements in the plagioclase structure will have on the data trend, as a function of the element partition coefficient between crystal and melt. Results demonstrate that the direction of change in slope of a material transfer data trend is a function of the initial relative magnitudes of the numerator constituents on the PER diagram. Additionally, if the amount of involvement of a PER denominator in a separating phase is very small relative to the amount of the numerator constituents in the separating phase, there is no significant change in the data trend caused by material transfer on a PER diagram. Moreover, if the denominator constituent substitutes for a numerator constituent in the phase undergoing transfer, the intercept of the trend of the data may not converge to zero when there is a large partition coefficient, as would be expected from theory. Thus, statistical tests to determine if a PER denominator is conserved, which evaluate whether the intercept is significantly different from zero, may not be very powerful because a large amount of denominator variation is necessary before the intercept of a data trend is forced through the origin, if at all.     

Definition and detailed characterization of Lunar surface units using remote observations

Remote sensing techniques and data may be subdivided into three principal types according to how they are used: (1) defining techniques help to define unit boundaries and extent; (2) characterizing techniques allow classification and characterization of physical features, lithology, or chemical composition; (3) supporting techniques provide additional useful information but are not fundamental to the definition or characterization of units. Defined units represent a fundamental subdivision of the rocks in a planetary crust and thus represent processes and sequences of events. The definition and characterization of units provides a framework for the interpretation of planetary processes and history. Detailed consideration of unit definition and characterization is presented using the mare deposits of the Imbrium basin as an example. This example provides guidelines for the utilization of remote sensing techniques in geologic mapping of the Moon and other planets.     

Structure and evolution of solar radio bursts at 26.4 MHz

Two dimensional source brightness distributions at 26.4 MHz for solar bursts of spectral type II, III, IV, and V are derived from observations with a multiple-baseline, time-sharing interferometer system. It was designed explicitly to study the large angle (40 halo) component of low frequency solar bursts first reported by Weiss and Sheridan (1962). Thirty-two bursts occurring in the interval of June–August, 1975, were fit with a circular gaussian core and an elliptical gaussian halo component. Half-power halo diameters (E-W×N-S) averaged 30×28 for type III bursts and 42×27, 28×37, 30×25 for type V, II and IV bursts respectively. Typical core sizes fell in the range of 10±4 giving 31 halo to core size ratio. All burst types were found to have some large angle structure: the specific intensity was 10% compared to the core but the total power in each component was comparable. Two processes for producing the core-halo structure of type III bursts are compared: scattering and refraction of a point source and refraction from many sources over an extended region. It is concluded that the core can be explained by either model but the halo is more consistent with emission from an extended source region of 40° in longitude.     

A spectroscopic study of moderately bright planetary nebulae

Spectroscopic results are presented for most of the nebulae observed in a programme involving some forty planetaries measured with an image tube scanner at Lick Observatory and with a photo-electric spectrum scanner at Mt. Wilson Observatory. The spectroscopic range normally covered, 3700 to 8700 is supplemented for a few objects with appropriate photographic data calibrated photoelectrically for the region 3120- 3800. Available published photoelectric data are also employed to improve the calibration of the finally adopted system of intensities.The main thrust of the programme is to investigate weaker lines, arising from less abundant ions, or due to less favorable excitation conditions. Information pertaining to additional ions gives further diagnostic data on the nebular plasma.For a given nebula, different diagnostics suggest different values of the electron temperature and density. These are believed to represent actual variations in physical conditions from point to point within the nebula, although in some instances, they may reflect inadequacies in atomic parameters, particularly collisional cross-sections. The spectroscopically most interesting nebulae show a wide variation in physical conditions, indicated by lines ranging in excitation from those of Mgi to [Fevii]. Relatively cool clouds of denser material appear to be immersed in a high excitation plasma excited by a hot central star.     

Problems in Estimating Impacts of Future Climate Change on Midwestern Corn Yields

Recent studies of trends in Midwestern precipitation show marked increases over the last 50 years of the 20th Century, and most climate models project that future rainfall in the Corn Belt will be increased further. During five years, 1988–1991 and 1994, field tests were conducted on agricultural test plots in central Illinois, an area typical of the Corn Belt, to discern how corn yields reacted to varying levels of added rainfall (+10%, +25%, and +40%) during the growing season. The best treatment over the five years was a 40% rain increase, with an average yield increase of 9%. Its yield increase was up to 34% in a hot-dry year, but below that of natural rainfall in a wet year as were the yields of the other lesser increases. The average yield changes from the three treatments were not statistically significantly different. Major interannual yield differences were found in the yields for each rain treatment, reflecting how rain timing and temperatures also have major effects on yields. A 40% summer rain increase has little influence if natural rains do not occur in the high stress period of mid summer. The plots results show that only small average increases in corn yields occur from growing season rain additions in the 10% to 40% range, except in dry years. Weather-crop yield regression models incorporating the same rain increases predict greater yield increases than found in these field tests. This suggests that future yields projected for a wetter climate using yield-weather models may be over-estimated. The plot sample size is small but conditions sampled in the five years represented 43% of all past 97 growing seasons in central Illinois and extremely good and bad weather years, which resulted in large between-year yield differences. Hence, the experimental results provide useful information about how increased rainfall may affect future corn yields, especially since the sample included three of the five types of dry growing seasons found in the area's climate since 1900.     

Linkage between microzooplankton grazing and phytoplankton growth in a Gulf of Mexico estuary

Microzooplankton dilution grazing experiments were conducted with water collected from Pensacola Bay, Florida (USA) on 12 dates at 2 sites. Statistically significant grazing rates were observed in 22 of 24 experiments. Grazing rates in Upper Bay and Lower Bay were similar averaging 0.54 and 0.51 d⁻¹, respectively. Phytoplankton growth rates were also similar at the two sites, averaging 1.02 and 1.00 d⁻¹ at Upper Bay and Lower Bay, respectively. Phytoplankton growth rates usually exceeded grazing rates by about a factor of two, though microzooplankton grazing represented a significant mortality for phytoplankton. The literature suggests a linkage between phytoplankton growth and microzooplankton grazing that spans a wide variety of aquatic environments. While individual growth and grazing rates were variable, growth frequently exceeded grazing by about two-fold. This implies that the role of microzooplankton is similar across a wide variety of aquatic systems.     

Multistage shortening in the Dauphiné zone (French Alps): the record of Alpine collision and implications for pre-Alpine restoration

Three-dimensional modelling tools are used with structural and palaeomagnetic analysis to constrain the tectonic history of part of the Dauphiné zone (external Western Alps). Four compressive events are identified, three of them being older than the latest Oligocene. Deformation D1 consists of W–SW directed folds in the Mesozoic cover of the study area. This event, better recorded in the central and southern Pelvoux massif, could be of Eocene age or older. Deformation D2 induced N-NW-oriented basement thrusting and affected the whole southern Dauphiné basement massifs south of the study area. The main compressional event in the study area (D3) was WNW oriented and occurred before 24 Ma under a thick tectonic load probably of Penninic nappes. The D2-D3 shift corresponds to a rapid transition from northward propagation of the Alpine collision directly driven by Africa-Europe convergence, to the onset of westward escape into the Western Alpine arc. This Oligocene change in the collisional regime is recorded in the whole Alpine realm, and led to the activation of the Insubric line. The last event (D4) is late Miocene in age and coeval with the final uplift of the Grandes Rousses and Belledonne external massifs. It produced strike-slip faulting and local rotations that significantly deformed earlier Alpine folds and thrusts, Tethyan fault blocks and Hercynian structures. 3D modelling of an initially horizontal surface, the interface between basement and Mesozoic cover, highlights large-scale basement involved asymmetric folding that is also detected using structural analysis. Both, Jurassic block faulting and basement fold-and-thrust shortening were strongly dependent on the orientation of Tethyan extension and Alpine shortening relative to the late Hercynian fabric. The latter’s reactivation in response to oblique Jurassic extension produced an en-échelon syn-rift fault pattern, best developed in the western, strongly foliated basement units. Its Alpine reactivation occurred with maximum efficiency during the early stages of lateral escape, with tectonic transport in the overlying units being sub-perpendicular to it.     

Inundation,sea-level rise and transition from Neolithic to Bronze Age cultures,Yangtze Delta,China

Petrological, faunal and floral information derived from a new drill core taken in the Yangtze delta, coupled with data from borings recovered earlier, record a marked transition to warmer, wetter conditions which resulted in widespread inundation of the delta about 4000 years ago. Also identified for that time on the delta plain is a major discontinuity between the Neolithic Liangzhu and Bronze age Maqiao cultures. The cultural discontinuity is indicated by: (1) absence of in situ material between the two at ∼4000 yr B.P.; (2) missing Maqiao material in strata above many Liangzhu sites; (3) less sophisticated Maqiao material than in the older Neolithic phase; and (4) notably fewer Maqiao sites in more restricted areas of the delta plain. It is of note that the change from the Liangzhu to the younger Maqiao does not show an increasingly complex cultural advancement of the type generally associated with the foundation of Chinese civilization. We propose that this cultural discontinuity was caused by the interplay of increased environmental stress and new population migrations into the delta. © 1999 John Wiley & Sons, Inc.     

Mapping dune dynamics by InSAR coherence

It is generally held that subtle changes in sandy environments are very difficult to detect in imagery. Nonetheless, this study demonstrates how synthetic aperture radar (SAR) interferometric decorrelation can be used to identify changes in individual sand dunes. The use of coherence maps over time facilitates the analysis of dune dynamics, both temporally and spatially. The Ashdod‐Nizzanim coastal dunes, along the southern coastal plain of Israel, were chosen as an illustrative example of the analysis of dune dynamics. High‐resolution TerraSAR‐X (TSX) radar images covering the entire research area were acquired for the period February to July 2012, together with meteorology data (wind and rain) for the area. The coherence results enabled the stability of individual dunes to be described as a function of time. It was found that the dune crests were more stable than the windward slopes and that the degree of stability was dependent on the distance of the dune from the sea. The results of this study show the potential of using interferometric synthetic aperture radar (InSAR) decorrelation for aeolian studies, even in areas characterized by low coherence. Copyright © 2017 John Wiley & Sons, Ltd.     

Fourier transform infrared microspectroscopic characterization of Neoproterozoic organic microfossils from the Fifteenmile Group in Yukon,Canada

Conventional and synchrotron radiation‐based (SR) Fourier transform infrared microspectroscopies (micro‐FTIR) were applied to four types of ~ 810 Ma organic‐walled microfossils together with diffuse organic matter (OM) and one irregularly shaped structure from the Fifteenmile Group, in Yukon, Canada, for their chemical characterization. The microfossils comprised one filamentous type and three coccoidal types. Micro‐FTIR mapping analysis revealed the micrometer‐scale, spatial distribution of organic components (aliphatic C‐H bonds) and carbonate in the microfossils. Based on comparisons of CH₃/CH₂ peak height ratios (R_3/2) and morphologies of the microfossils (without the diffuse OM) to those of previously described Proterozoic microfossils, possible affinities of the microfossils are suggested, as follows. Palaeolyngbya? and Glenobotrydion belong to bacteria. Myxococcoides is not clearly characterized due to the significant mixing with diffuse OM containing abundant aliphatic C‐H groups. The irregularly shaped structure may represent a eukaryote. The diffuse OM may represent a mixture of decomposed microbial cells and extracellular polymeric substances (EPS). SR micro‐FTIR measurements of two coccoid types (Glenobotrydion and Unnamed Coccoid Form D) revealed that the R_3/2 values of the internal spots with wall structures are similar to those without wall structures in Glenobotrydion: those values from Unnamed Coccoid Form D were different. The results suggest that these two coccoids are different chemically as well as morphologically. Micro‐FTIR characterization of the organic‐walled microfossils together with morphological analysis provides new insight into their biological affinities.