国际古植物学1989年研究进展

古植物学是一个日新月异发展着的学科。每年,都有一些新的方法问世,它们结合地质学和生物学方法来研究地史时期植物的生活。其研究广度可以从1989年7月在美国首都华盛顿召开的第28届国际地质大会上明显看出。古植物学家们报告了他们关于“古气候”、“前寒武纪/寒武纪的过渡”、“泥炭和煤的来源”、“适应辐射”、“埋藏过程”、“特异埋藏”及南极地质等方面的研究成果;关于晚石炭世植物群的生物地理方面的文章也很多。 由Gastaldo(1989)编辑的《植物埋藏学——有机沉积过程》论文专辑是将更多的地质     

A rapid-response 2-D drag anemometer for atmospheric turbulence measurements

A rapid response drag anemometer for measuring streamwise and lateral components of horizontal windspeed is described. Theory of operation, design and calibration are discussed with emphasis on the electronic preconditioning of signals and problems associated with using a mechanically resonant system as a sensor. Field comparisons showed half-hourly means and standard deviations of the streamwise component to be within 8% and 5% of respective values obtained from a 3-dimensional sonic anemometer. The lateral component from the drag anemometer was significantly more noisy than that from the 3-D sonic due to induced oscillations arising from vortex shedding. After mechanical and electronic filtering, half-hourly standard deviation comparisons agreed to within 6% for this component. Friction velocities obtained from the drag anemometer in combination with a 1-D sonic, agreed with measurements from the 3-D sonic anemometer to within 4% over a measured range of 0.05 to 1.2 m s^-1     

A water column sampler for invertebrates in salt-marsh tidal pools

A column sampler for use in shallow (1 m) pools is described. The apparatus is a 10-cm diameter PVC pipe mounted on a base plate. A sliding trap on the base plate is attached to a cable which runs over a pulley to the upper part of the sampler. A whole water column of 78 cm² is sampled and 1–2 cm of substrate can be included as desired. The sampler has been used successfully in salt marsh pools to census gastropods, amphipods, and copepods.     

Zircon saturation revisited: temperature and composition effects in a variety of crustal magma types

Hydrothermal experiments in the temperature range 750–1020°C have defined the saturation behavior of zircon in crustal anatectic melts as a function of both temperature and composition. The results provide a model of zircon solubility given by: In D_Zr^zircon/melt= ?3.80?[0.85(M?1)]+12900/T where D_Zr^zircon/melt is the concentration ratio of Zr in the stoichiometric zircon to that in the melt, T is the absolute temperature, and M is the cation ratio (Na + K + 2Ca)/(Al · Si). This solubility model is based principally upon experiments at 860°, 930°, and 1020°C, but has also been confirmed at temperatures up to 1500°C for M = 1.3. The lowest temperature experiments (750° and 800°C) yielded relatively imprecise, low solubilities, but the measured values (with assigned errors) are nevertheless in agreement with the predictions of the model.For M = 1.3 (a normal peraluminous granite), these results predict zircon solubilities ranging from ～ 100 ppm dissolved Zr at 750°C to 1330 ppm at 1020°C. Thus, in view of the substantial range of bulk Zr concentrations observed in crustal granitoids (～ 50–350 ppm), it is clear that anatectic magmas can show contrasting behavior toward zircon in the source rock. Those melts containing insufficient Zr for saturation in zircon during melting can have achieved that condition only by consuming all zircon in the source. On the other hand, melts with higher Zr contents (appropriate to saturation in zircon) must be regarded as incapable of dissolving additional zircon, whether it be located in the residual rocks or as crystals entrained in the departing melt fraction. This latter possibility is particularly interesting, inasmuch as the inability of a melt to consume zircon means that critical geochemical “indicators” contained in the undissolved zircon (e.g. heavy rare earths, Hf, U, Th, and radiogenic Pb) can equilibrate with the contacting melt only by solid-state diffusion, which may be slow relative to the time scale of the melting event.     

A model for earth science data structures designed to promote generalization of earth science data processing systems

During the past 15 years earth science survey data compilation has gradually changed from a manual process to one almost entirely computer automated. Computer methods were at first an optional means for improvement of the speed and efficiency of certain phases of the work. They eventually became mandatory as in-flight digital acquisition devices were introduced and rates of data acquisition increased to the point where manual methods became totally inadequate. As a consequence of the phased replacement of manual systems with digital ones, and the pressing need to avoid interruptions to the work, the resulting software is highly specialized. Software systems are incompatible between different organizations compiling the same kind of data and even between systems for different kinds of data within one organization. The result is wastage of manpower in maintaining, learning to use, and improving the great variety of existing systems, and wastage of man and computer time in converting data to a form compatible with the peculiarities of each particular system. Comparative analysis of highly specialized compilation systems form several different earth science disciplines reveals that processes do exist at the fundamental level which are generally applicable to a range of disciplines. Hence a generalized compilation system capable of eradicating the problems inherent in multiple specialized systems is at least conceptually feasible. The most serious obstacle to its realization however, is the diversity of data content and structure among the various disciplines. To surmount this obstacle, a system with a great degree of physical and logical independence of data from software will be necessary. Existing methods of achieving such independence within data base management systems are found to be largely inapplicable to earth science survey compilation, the principle reasons being the very large quantities of data involved and significant differences between the data retrieval requirements of compilation systems and data base management systems. It is found that, although the data contents and structures vary greatly between the various compilation systems examined, a general abstract model can be constructed which adequately represents all of them and which incorporates the means for achievement of data independence. The logical data structures of current data base management systems are based variously on relational calculus, set theory, and graph theory. The compilation data structure model is based on simple algebra with the addition of some components of vector algebra. It is further found that simple algebraic manipulation of the model expressions faith-fully simulates the actual data manipulation processes which are applied by the various compilation systems. Furthermore, unlike the logical models of the data base management systems, the logical structure of the compilation data model also represents the actual physical structure exhibited by the data in its most common, sequential form.