The application of expert systems to the identification and use of microfossils in the petroleum industry

Development of an expert system for microfossil identification and their use in dating rocks demonstrates that such systems can be used in the evaluation and interpretation of basic geological data. Palaeontological data lends itself to this kind of approach because it is controlled to a greater extent than other geological data by internationally accepted rules and practice. Two fossil groups, planktonic foraminifera and conodonts, have been chosen for initial development, both groups having a long history of study.     

Volume integrals of the products of spherical harmonics and their application to viscous dissipation phenomena in fluids

The equations governing the conversion of kinetic energy into heat in moving viscous media are formulated as volume integrals of products of spherical harmonics. Although the formulation of the fundamental equations is classical, difficulties in the integration of certain products of generalized spherical harmonics over a sphere have permitted heretofore the treatment of only two cases. The closed, form evaluation of eight fundamental types of definite integrals of the product of spherical harmonics, some of them new, or at least missing in the literature, makes possible for the first time the evaluation of these volume integrals in closed form for arbitrary order and index. Explicit details are given for the rates of energy dissipation produced by viscous motions characterized by spheroidal as well as toroidal symmetry.     

Geochemical fingerprints of dolomitization in Bahamian carbonates: Evidence from sulphur,calcium, magnesium and clumped isotopes

In an effort to constrain the mechanism of dolomitization in Neogene dolomites in the Bahamas and improve understanding of the use of chemostratigraphic tracers in shallow‐water carbonate sediments the δ³⁴S, Δ₄₇, δ¹³C, δ¹⁸O, δ^44/40Ca and δ²⁶Mg values and Sr concentrations have been measured in dolomitized intervals from the Clino core, drilled on the margin of Great Bahama Bank and two other cores (Unda and San Salvador) in the Bahamas. The Unda and San Salvador cores have massively dolomitized intervals that have carbonate associated sulphate δ³⁴S values similar to those found in contemporaneous seawater and δ^44/40Ca, δ²⁶Mg values, Sr contents and Δ₄₇ temperatures (25 to 30°C) indicating relatively shallow dolomitization in a fluid‐buffered system. In contrast, dolomitized intervals in the Clino core have elevated values of carbonate associated sulphate δ³⁴S values indicating dolomitization in a more sediment‐buffered diagenetic system where bacterial sulphate reduction enriches the residual in ³⁴S, consistent with high sediment Sr concentrations and low δ^44/40Ca and high δ²⁶Mg values. Only dolomites associated with hardgrounds in the Clino core have carbonate associated δ³⁴S values similar to seawater, indicating continuous flushing of the upper layers of the sediment by seawater during sedimentary hiatuses. This interpretation is supported by changes to more positive δ^44/40Ca values at hardground surfaces. All dolomites, whether they formed in an open fluid‐buffered or closed sediment‐buffered diagenetic system have similar δ²⁶Mg values suggesting that the HMC transformed to dolomite. The clumped isotope derived temperatures in the dolomitized intervals in Clino yield temperatures that are higher than normal, possibly indicating a kinetic isotope effect on dolomite Δ₄₇ values associated with carbonate formation through bacterial sulphate reduction. The findings of this study highlight the utility of applying multiple geochemical proxies to disentangle the diagenetic history of shallow‐water carbonate sediments and caution against simple interpretations of stratigraphic variability in these geochemical proxies as indicating changes in the global geochemical cycling of these elements in seawater.     

The department of defense Selenodetic Control System and the force function of the moon

The figure of the moon as defined by the DOD-66 Selenodetic Control System is first studied. Then, using the derived equation for the surface and adopting the density law = _c + ^p , we have evaluated the volume integrals relating the form of the surface to the gravity harmonics.     

Some problems in planning the office economy in a third world city: the example of Tunis

While the office economy has been studied extensively in the advanced industrial nation, it has been overlooked in the context of the developing country. Based on a case-study of Tunis it is shown how the growth of office activities in the central area has exacerbated the planning problems of the city's core. Planning policies designed to control the rate of office growth in the central area and encourage its suburban decentralization have been introduced. However, achievements to date on either of these two aims have been limited, reflecting political, administrative and fiscal problems which limit the effectiveness of planning in the city as a whole.     

Human development is linked to multiple water body impairments along the California coast

To elucidate relationships between land cover and water quality along the central California coast, we collected monthly samples from 14 coastal waterway outlets representing various degrees of human development. Sites were distributed between three salinity categories, freshwater, estuarine, and marine, to better understand land cover-water quality relationships across a range of coastal aquatic ecosystems. Samples were analyzed for fecal indicator bacteria (FIB), dissolved nutrients, stable nitrogen isotopes in particulate organic matter, and chlorophylla (chla). Sediment samples from 11 sites were analyzed for the concentration of the anthropogenic organic contaminant perfluorooctane sulfonate and its precursors (ΣPFOS). While the data indicated impairment by nutrient, microbial, and organic contaminants at both agricultural and urban sites, the percentage of agricultural land cover was the most robust indicator of impairment, showing significant correlations (p<0.05) to FIB, nutrient, chla, and ΣPFOS levels. FIB densities were strongly influenced by salinity and were highest at sites dominated by agriculture and urbanization. Nutrient levels and chla correlated to both agricultural and urban land use metrics as well. Positive correlations among FIB, nutrients, chla, and ΣPFOS suggest a synergy between microbial, nutrient, and organic pollution. The results emphasize the importance of land management in protecting coastal water bodies and human health, and identify nutrient, microbial, and organic pollution as prevalent problems in coastal California water bodies.     

Three magmatic components in the 1973 eruption of Eldfell volcano,Iceland: Evidence from plagioclase crystal size distribution (CSD) and geochemistry

The 1973 eruption of Eldfell volcano, Iceland, appears to have been a short, simple event, but textural and geochemical evidence suggest that it may have had three different magmatic components. The first-erupted fissure magmas were chemically evolved, rich in plagioclase (∼ 18%) and had shallow, straight crystal size distribution (CSD) curves. The early lavas were less evolved chemically, had lower plagioclase contents (∼ 13%) and steeper, slightly concave up CSDs. The late lavas were chemically similar to the early lavas, but even richer in plagioclase than the initial magmas (∼ 24%) and had the steepest CSDs. There was no chemical evidence for plagioclase fractionation, but compositional diversity could be produced by clinopyroxene fractionation which must have occurred at depth. We propose that the eruption started with old, coarsened (Ostwald ripened) magma left over from a previous eruption, possibly that which produced Surtsey Island ten years earlier. The early flows may be mixtures of small amounts of this old magma with a new, low crystallinity, uncoarsened magma or a completely new magma. The late flows are another new magma from depth, chemically similar to the early flows, but which has grown plagioclase under increasing saturation (undercooling) perhaps during its ascent. All three magmatic components may have originated from the same parent, but had varying degrees of clinopyroxene fractionation, plagioclase nucleation and growth, and coarsening.     

Geochemistry of the early proterozoic metasedimentary rocks of the alligator rivers region,Northern Territory,Australia

The early Proterozoic metasedimentary sequence of the Alligator Rivers Region (a part of the Pine Creek Geosyncline) in the Northern Territory, Australia, overlies an Archaean granitoid basement. Early Proterozoic sedimentary sequences, in general, record important changes in the composition of the upper continental crust about the Archaean-Proterozoic boundary. However, the geochemistry of only a few of these sequences has been documented. The geochemistry of the early Proterozoic succession in the Alligator Rivers Region is reported here and the results are interpreted in terms of differences between the stratigraphic units, their provenance—particularly in relation to crustal evolution, and their subsequent metamorphism and weathering.Clastic metasedimentary rocks throughout the Alligator Rivers Region have a remarkably uniform major and trace element geochemistry. The Kakadu Group and upper member of the Cahill Formation are relatively more enriched in SiO₂ and correspondingly more depleted in Al₂O₃ than the rest of the sequence, reflecting the greater dominance of metapsammitic assemblages. The lower member of the Cahill Formation, which hosts the major U deposits of the Alligator Rivers Region, and the metasedimentary sequence in general, exhibit no significant enrichment in U above normal background values. Rare earth element (REE) concentrations in the metasedimentary units within the Alligator Rivers Region are uniform, though in detail there are some important differences within and between formations.The composition of the early Proterozoic clastic metasediments in the Alligator Rivers Region is consistent with the composition of similar material of the same age from other areas, and supports current ideas on crustal evolution. The Alligator Rivers metasediments are enriched in Si and K, and depleted in Mg, Ca, and Na relative to the Archaean average for clastic sedimentary rocks, and their REE geochemistry resembles typical post-Archaean sedimentary rocks having a light REE enriched pattern and a distinct Eu/Eu1 depletion compared to typical Archaean sediments. However, the REE data indicate that two compositionally distinct sources are involved in the provenance of the Kakadu Group, and possibly the lower member of the Cahill Formation, where two types of REE patterns can be distinguished on their HREE concentration and Eu/Eu1 anomaly.     

Fracture-frequency prediction from borehole wireline logs using artificial neural networks

Borehole-wall imaging is currently the most reliable means of mapping discontinuities within boreholes. As these imaging techniques are expensive and thus not always included in a logging run, a method of predicting fracture frequency directly from traditional logging tool responses would be very useful and cost effective. Artificial neural networks (ANNs) show great potential in this area. ANNs are computational systems that attempt to mimic natural biological neural networks. They have the ability to recognize patterns and develop their own generalizations about a given data set. Neural networks are trained on data sets for which the solution is known and tested on data not previously seen in order to validate the network result. We show that artificial neural networks, due to their pattern recognition capabilities, are able to assess the signal strength of fracture-related heterogeneity in a borehole log and thus fracture frequency within a borehole. A combination of wireline logs (neutron porosity, bulk density, P-sonic, S-sonic, deep resistivity and shallow resistivity) were used as input parameters to the ANN. Fracture frequency calculated from borehole televiewer data was used as the single output parameter. The ANN was trained using a back-propagation algorithm with a momentum learning function. In addition to fracture frequency within a single borehole, an ANN trained on a subset of boreholes in an area could be used for prediction over the entire set of boreholes, thus allowing the lateral correlation of fracture zones.