Lithological Profiles Research Articles

Paleomagnetic excursions recorded in the Yanchi Playa in middle hexi corridor, NW China since the last interglacial

Paleomagnetic determinations on lithological profiles of two paralleled long drilling cores covering the past 130 kyr B.P., GT40 and GT60, from the Yanchi Playa in the arid Northwestern China, indicate that a series of pronounced paleomagnetic excursions have been documented. By correlating our results with published regional and worldwide reports, 4 excursion events out of 10 apparent reversal signals (labeled from GT-1 to GT-10) were identified as excursion events coeval with the Mono Lake Event (28.4 kyr–25.8 kyr), Laschamp Event (43.3 kyr–40.5 kyr), Gaotai Event (82.8 kyr–72.4 kyr) and the Blake Event (127.4 kyr–113.3 kyr), respectively. GT-9 correlates with the above-mentioned Gaotai Event, GT-7 and GT-6 correspond to two stages of the Laschamp Event and GT-5 to the Mono Lake Event. It is noteworthy that the so-called Gaotai Event has not been reported as a pronounced paleomagnetic excursion in the Northwestern China. Every magnetic excursion event corresponds to paleointensity minima, anteceding those established abrupt paleoclimatic change events, such as the Younger Drays and the Heinrich Events (H1–H6). Here, we tentatively propose that these geomagnetic excursions/reversals can be viewed as precursors to climate abruptness. During the transitional stages when the earth’s magnetic field shifted between a temporal normal and a negative period, the earth’s magnetic paleointensity fell correspondingly to a pair of minima. Although more precise chronology and more convincing rock magnetic parameter determinations are essentially required for further interpretation of their intricate coupling mechanism, these results may have revealed, to some extent, that the earth’s incessantly changing magnetic field exerts an strong influence on the onset of saw-tooth shaped abrupt climate oscillations through certain feedback chains in arid Central Asia or even North Hemispheric high latitude regions.

Volcanic stratigraphy of DSDP/ODP Hole 395A: An interpretation using well-logging data

Deep Sea Drilling Project/Ocean Drilling Program Hole 395A was drilled approximately 500 m deep into young oceanic crust west of the Mid-Atlantic Ridge. Core recovery is very poor in this hole and therefore continuous downhole measurements are important to understand the drilled lithology. Geophysical downhole measurements were carried out during several cruises. A new set of logs was recorded during Leg 174B in summer 1997. The new logging data show a significant improvement in data quality compared to older measurements from Leg 109. The lithostratigraphy established from cores gives only limited information because of the poor core recovery in this hole. The gaps in the core lithostratigraphy are filled by reconstructing a synthetic lithological profile using the standard well-logging data. Three types of lava morphologies, massive basalts, altered lava flows, and pillow basalts, may be distinguished using the logs because the lava morphologies show differences in their physical properties due to differences in fracturing and alteration. The synthetic lithological profile gives a more detailed and precise vertical definition of single layers than the core profile. The integration of further logging and core data enables a detailed reconstruction of the accretion history at the drill site. Cyclic, upward decreasing trends in the resistivity logs were already observed during earlier cruises and were referred to magmatic cycles. Similar trends occur in the density log and, inversely, in the total gamma ray log. The trends reflect gradual changes in fracturing, porosity, permeability, and alteration and cover depth intervals of several tens of meters. Boundaries between cycles are interpreted to correspond to periods of volcanic quiescence. Two types of boundaries may be identified. Boundaries correlating with reversals in the magnetic field and/or changes in the geochemical composition of the basalts are interpreted as long pauses. Basalts separated by these boundaries were probably fed by separate magma reservoirs. Boundaries identified only by changes in alteration but not in geochemistry are interpreted to represent shorter pauses. They separate basalts that were probably fed by the same magma chamber.

Ultralow‐radiation‐intensity spectrometric probe for orebody delineation and grade control of zinc‐lead ore

A fully spectrometric gamma—gamma probe using an ultralow‐activity gamma‐ray source (i.e., <2 MBq) has been developed. The prototype low‐radiation‐intensity probe was tested at a zinc‐lead deposit in Queensland, Australia. The probe showed an excellent capability for orebody delineation. Lithological profiles derived from logging data showed sharp anomalies both in selected spectral regions and in spectral ratios during probe transition from orebody to barren rock, or vice versa. In comparison to standard geochemical analysis, the instrument demonstrated good potential for quantitative determination of lead and zinc content in ore with rms error of 0.3% and 2.4%, respectively. Delineation of nonlithological boundaries, through an application of a cutoff‐grade algorithm, has been demonstrated as a practical stand‐alone mine control tool.

Hydrogeological characterization of the onshore Quaternary sediments at Sellafield using the concept of domains

As part of an assessment of the performance of a potential deep repository for intermediate- and some low-level radioactive wastes at Sellafield, numerical models of the regional scale groundwater flow were built. Quaternary sediments play an important role in the flow because they control recharge to the deeper groundwater system. This paper outlines research carried out under the Nirex Quaternary Characterization programme at Sellafield and shows how lithological and structural characterization of the sediments has enabled the development of Quaternary Hydrogeological Domains which have been used in the regional groundwater models. The Quaternary sediments in the Sellafield area are very varied and result from more than one ice advance. Sediments include glaciogenic diamictons, coarse glaciofluvial gravels probably deposited as sandar and silts of probable glaciolacustrine origin. These sediments are locally glacitectonically deformed. Recent alluvial, marine and lacustrine sediments are also present. The lateral extent of many of the sediment bodies is expected to be small, and therefore their complete characterization by the traditional approach of interpolating between measurements in boreholes and at outcrop is likely to be difficult, without an impracticably large number of boreholes. Thus the hydrogeology was characterized on the basis of the geology, supported by a relatively small number of boreholes and hydraulic measurements. Quaternary Geological Domains defined by distinctive landform-sediment associations and structural characteristics were mapped. Distinctive vertical profiles of sediments were identified from subsurface data (e.g. borehole data). This enabled the Geological Domains to be refined to Hydrogeological Domains. The overall performance of the system can be confirmed by reference to detailed field scale measurements in specific areas. The behaviour varies between providing little impediment to recharge to, or discharge from, the underlying strata of the Sherwood Sandstone Group over most of the area, but with local areas where recharge or discharge is considerably impeded. Locally, the Quaternary deposits contribute a significant part of the transmissivity of the regional aquifer. The hydraulic characteristics of individual sediment types are known from laboratory data and limited field data. These data have been integrated and upscaled using analytic calculations based on the lithological profiles recognized in the Hydrogeological Domains. This has enabled the derivation of effective properties, which were used in the regional-scale flow models. The resulting parameter values are consistent with those independently derived from regional aquifer modelling.

Environmental assessment: contamination of phreatic aquifer in areas impacted by waste from coal processing activities

The objective of the present work was to evaluate the degree of contamination of groundwater in areas under influence of inadequate disposal of residues from coal-processing activities. Charqueadas and São Jerônimo Counties were selected for the study. The contamination of groundwater from the phreatic aquifer was evaluated in a sequence of steps: initially, the target area was selected; then, the piezometers were installed and groundwater was sampled. The location of piezometers was based on the results obtained from the mapping of pollution sources, geophysical and hydrogeological studies. The results showed that the groundwater (phreatic aquifer) from the region studied is influenced, in variables degrees of intensity, by the type and characteristics of residues, the lithological profile of the site and the distance from the pollution sources. Physical and chemical characterization revealed that coal waste influenced more significantly groundwater contamination, evidenced by acidic pH values, as well as high values of conductivity, total dissolved solids (TDS), sulfates, ferrous iron and metals (Ni, Fe, Co, Cr and Mn). The statistical analysis applied to the variables studied gave a General Groundwater Index for each well. By the application of this index, it was possible to highlight the kind of residues and variables that are affecting the groundwater quality.

The application of glacial dispersal models to the interpretation of till geochemistry in Labrador, Canada

In western Labrador, Canada, bedrock composition and glacial history are both reflected in till geochemistry. There, compositional contrasts between igneous and metamorphic bedrock of the Canadian Shield and comparatively unmetamorphosed bedrock of the Labrador Trough allow regional-scale (100s of km) definition of glacial dispersal trends through lithological and geochemical analyses. Compared to till derived from shield terrane, Labrador Trough till is depleted in chromium, but enriched in zinc, iron, and manganese. Further, the study area is situated near one or more dispersal centers of the Laurentide Ice Sheet and has been subjected to a complex sequence of ice flow, defined by striations and indicator erratic distributions. Three glacial events serve as the principal controls on drift composition, although their relative significance varies. Compositional profiles along the axis of two glacial dispersal trends show systematic changes in indicator erratic concentrations with distance along the path of ice flow. In the profile having one prominent glacial transport direction, indicator concentrations decrease exponentially with increasing distance of glacial transport. From dispersal models, Renewal Distances representing the compositional `half-life' tend to increase with decrease in grain size, i.e. 15 to 25 km for pebbles, and 30 to 40 km, or more, in silt- and finer-sized fractions. The differences between geochemical and lithological profiles reflect differences in: (1) the intensity or duration of subglacial process affecting the milling of indicator detritus to finer fractions; and (2) the physical and chemical properties of the rocks and minerals hosting the trace metals. Where regional glacial dispersal trains extend across contrasting geological terranes, indicator properties can be used to resolve till composition into `local' and `transported' components, providing a better approximation of bedrock composition for mineral exploration. The compositional expression of bedrock can be masked by transported overburden, with the extent of masking dependent on the trace metal examined. Linear relations between metals (Cr, Zn) and lithophile elements (e.g. K, Mg) indicate that Mg-bearing minerals, likely phyllosilicates, have a strong mineralogical control on till geochemistry, and metal : lithophile element ratios can be used to distinguish bedrock provenance in glacially transported materials of western Labrador.

The geometry of the Rupelian and Chattian depositional bodies in the Lower Rhine district and its border area: implications for Oligocene lithostratigraphy

Three profiles are constructed through the Oligocene succession of the borderland between Belgium, Germany and the Netherlands. The profiles illustrate the geometric relationships between Rupelian and Chattian successions and the lateral and vertical variations within the Rupelian and Chattian deposits. The end-Rupelian profile between Central Belgium and the Achterhoek area in the Netherlands shows a rather uniform thickness distribution. This is in sharp contrast to the fault controlled sedimentation during the Chattian as represented on an end-Chattian profile between the same areas. Within the Chattian succession several lithostratigraphic units can be identified and correlated using a dense net of geophysical well logs. Remarkably similar subdivisions are found in the different tectonic blocks, suggesting eustatic sea-level fluctuations. In the central part of the subsiding area the Chattian deposits are largely continental to deltaic. Laterally,these deposits developed into marine glauconitic sediments. The end-Chattian profile between Bonn and Asten in the Netherlands runs approximately parallel with the subsidence axis. The cyclicity expressed by facies alternations due to a periodically shifting coastline can be correlated over the different blocks again suggesting the involvement of eustatic controls. On this last profile, an anomalous geometry is due to SE-NW stress-induced movements along the Variscan Aachen overthrust.The three lithological profiles are meant to represent a frame for formal stratigraphic subdivisions and nomenclature.

A combined hillslope hydrology/stability model for low-gradient clay slopes in the Italian Dolomites

The temporal trend of displacement of a landslide on a low-gradient clay slope in the Italian Dolomites as a function of precipitation was simulated with a combined hydrological-slope stability model based on groundwater and surficial displacement observations. Piezometric records and lithological profiles from boreholes suggest the occurrence of preferential groundwater flow through a very permeable top layer of about 1 m thickness, which overlies a less permeable, compact clay layer penetrated by dead-end cracks. To simulate groundwater levels in this system, a linear reservoir model with two outlets was applied, where the upper outlet drains the permeable top layer, and the lower outlet drains the dead-end cracks in the clay layer. The reservoir was assigned a bottom boundary level varying in time. This was done to represent an inferred yearly fluctuation of a matric groundwater level due to regional flow, which controls the thickness of the unsaturated part of the clay layer absorbing water from the cracks. Groundwater output from the model was used in a visco-plastic stability model to simulate the velocity of landslide movement, taking into account a phenomenon of strength regain that occurs in the clays along the slip surfaces. Calibration and validation on 3 years of groundwater and displacement data showed that both models yield good results. Thus, good estimates of cumulative landslide displacement were obtained as a function of precipitation. The general concepts underlying the models offer possibilities for regionalization because from a geological point of view, this landslide is typical of many others in the Dolomites.

Integrated log interpretation in the German Continental Deep Drilling Program: Lithology, porosity, and fracture zones

Well logs, aquired in the two scientific drill holes of the German Continental Deep Drilling Program (KTB), provide continuous records of physical and chemical data of the metamorphic rocks penetrated. The 4‐km‐deep pilot hole was almost completely cored, enabling the well logs to be calibrated with regard to rock composition and structural features derived from laboratory analysis of cores. The observed relationships were transferred to the 9101 m deep, nearly uncored, main hole to reproduce in detail the lithology and to estimate physical properties from the logs. Synthetic lithological profiles were constructed for the pilot hole and the main hole by applying the electrofacies concept adapted to the crystalline environment. These profiles provide information on lithostratigraphy, alteration, cataclastic overprint, and petrogenetic features. Cross‐hole correlations of these profiles reveal identical rock sequences for large sections of the drilled, metamorphic basement in both holes, in which the primary differences between the protoliths are largely preserved. Multivariate statistical methods were used to determine porosity depth functions from log responses. Linear as well as multilinear regression yielded continuous porosity profiles for both boreholes. Factor analysis was used to extract a parameter interpreted as a fluid and fracture indicator. Comparison of the porosity profiles with lithological information from log, core, and cuttings data revealed two different origins of increased porosity. Rock porosity and permeability are not only related to discrete planar discontinuities such as faults and fractures but also to more extensive zones of intense rock alteration where considerable matrix porosity occurs.

Strontium isotope systematics of conodonts: Middle Devonian, Eifel Mountains, Germany

The Eifel Mountains lithological profile, the stratotype for the Middle Devonian, was densely sampled for conodonts to delineate the Sr isotopic evolution of coeval sea water. The 87Sr/86Sr curve obtained shows oscillations around a mean of about 0.7078 that have a frequency in the 105–106 yr range and an amplitude in the 10−5–10−4 range. These oscillations mimic those obtained on coeval brachiopods (Diener et al., 1996), but are shifted into more radiogenic domains by up to 10−4. Model calculations suggest that the shift is due to partial (30–40%) early diagenetic equilibration of conodonts with their enclosing bulk-rock matrix. The reality of partial recrystallisation is supported by visible neoformed blocky apatite crystals on the surface of the conodonts, despite their otherwise apparently excellent preservation, with CAI values of 1.5–2.5. We therefore suggest that studies anticipating use of conodonts as a recorder of paleoceanographic events should be confined to specimens embedded in a relatively `clean' matrix, such as pure limestone. Even these results should be cross-checked by comparison with data on coeval low-Mg shells, such as brachiopods or belemnites.

The nature and diversity of pressure transition zones

Pressure transition zones occur where the rate of pressure increase or decrease exceeds a fluid gradient. Transition zones are found between intervals of permeable rock and, in each case, fluid movement is impeded by a 'seal', which acts as a temporary barrier over geological time. The composite profile of pressure vs. depth is a function of three phenomena: (1) the mechanism responsible for abnormal pressure, (2) redistribution of pressure due to fluid movement during and after the mechanism is occurring, and (3) the lithological profile of the rock succession. Pressure profiles in some overpressured systems can reveal which of the mechanisms is causing the overpressure. Once overpressure has been created, pressure decay and transference away from the interval of generation can strongly influence the nature of transition zones. Transition zones are controlled in a fundamental way by the permeability of the rocks in which the abnormal pressure is found.

Constructional features of Troodos type oceanic crust: Relationships between dike density, alteration, magnetization, and ore body distribution and their implications for in situ oceanic crust

Quantitative relationships are demonstrated between dike density and hydrothermal alteration, magnetization, location of volcanic massive sulfide (VMS) ore bodies and a number of other properties in a 40 by 15 km segment of the Extrusive Series of the Troodos Ophiolite. Low‐temperature alteration extends from the sediment‐extrusive interface to close to the 25% dike density surface, while the onset of greenstone type alteration is closely associated with the 50% dike density surface. These associations are explained in terms of the regional scale variations in the dike density contour surfaces following the form of the top of the gabbroic layer of the ophiolite. An upper magnetic zone, characterized by stable high remanence, terminates just below the 25% dike density surface. A deeper magnetic zone, characterized by high induced magnetization, straddles the top of the Sheeted Complex. Volcanic massive sulfide bodies are concentrated in a narrow depth range centered about 0.1 km above the 25% dike density surface. A model for the postridge crest evolution of ore bodies accounts for this optimum depth range for preservation. Physical property changes with dike density, and the depth distribution of VMS ore bodies and prospects for the ophiolite as a whole support this model. Similar relationships appear to be present in the Samail, Macquarie Island, Newfoundland and Chilean ophiolites and Icelandic crust. As a result of relationships found in the Troodos ophiolite, an alternative is proposed to the current lithologic profile for Ocean Drilling Program Hole 504B.

Seismic models of a prograding carbonate platform: Vercors, south-east France

The southern Vercors area (south-east France) displays superb exposures of a Lower Cretaceous prograding carbonate platform. These exposures allow a geometrical sequence analysis to be combined with detailed outcrop observations. Two-dimensional seismic modelling techniques were used to determine the seismic response of three of these exposures: the Montagnette, the Archiane Valley and the Rocher de Combau. The outcrops display prograding and retreating series of clinoforms interfingering with fine-grained basinal sediments. Photographs from different angles of view, combined with detailed field observations, were used to construct lithological profiles with a resolution of f few metres. P-wave velocities and bulk densities were measured from cored hand specimens and selected values were assigned to lithostratigraphic units in each profile. The vertical incidence modelling technique was then used to compute migrated time sections of reflectivity. These were convolved with source wavelets of different frequencies to produce the final synthetic seismic profiles. None of the modelled outcrop geometries is correctly portrayed seismically at 25–50 Hz frequencies. Not only do the synthetic seismic profiles show less detail, they also show misleading geometries. In most seismic models, for instance, pseudo-unconformities are present that correspond to rapid changes in dip and in facies in outcrop. Furthermore, the seismic tool is not able to resolve between stratal patterns punctuated by unconformities and those with gradual shifts in facies belts accompanied by complex interfingering relationships. This implies that an unconformity recognized on a real seismic line should not automatically be assumed to represent a true stratal unconformity. Large outcrops are often used to show the validity of sequence stratigraphy, a concept mainly based on the analysis of seismic lines. This study, however, shows that there is no one to one relationship between geometries observed in outcrop and in seismic lines. Seismic modelling of outcrops therefore provides a means for evaluating outcrop geometries in terms of seismic stratigraphy.

Neural Networks: Prediction of Carbonate Lithology and Permeability from Wireline Logs in a Miocene Buildup, Offshore Sarawak: ABSTRACT

A gas-bearing Miocene carbonate field is used as a case study to demonstrate the impact of neural network technology (nonlinear complex-pattern recognition) in carbonate reservoir modeling. In the Sarawak Miocene buildups, as in many carbonate reservoirs, most porosity is of diagenetic origin, and poroperm character is determined by dominant pore type (i.e., moldic, intergranular, intercrystalline). A fundamental prerequisite to modeling geometries of depositional/diagenetic bodies in 3-D is the ability to recognize these lithofacies (and their permeability values) from wireline logs in wells where core is unavailable; a task that has often proved elusive, as in this case, using conventional programming techniques. Neural networks appear to have solved these problems by their ability to [open quotes]learn[close quotes] the relationship between the core-defined lithofacies and permeability measurements from conventional petrophysical log suites. Neural networks can recognize nonlinear relationships, and they do not rely on predefined algorithms, thereby avoiding the limitation of fitting scattered data to linear trends. On this Miocene training set, lithofacies classifications were [open quotes]learnt[close quotes] to an accuracy of over 90%. The neural network solution for permeability prediction from logs halved the root-mean square error of the predictions obtained by conventional techniques. These results were obtained using standard logmore » suites, making the technique especially suited to field reviews and regional studies. Application of the trained networks to log suites of noncored wells in the field gives geological control by providing lithology and permeability profiles. This allows detailed interwell correlation of diagenetic rock types and their lateral porosity-permeability trends, forming the basis for 3-D reservoir modeling.« less

High-Sulfur Coals in the Eastern Kentucky Coal Field

The Eastern Kentucky coal field is notable for relatively low-sulfur, [open quotes]compliance[close quotes] coals. Virtually all of the major coals in this area do have regions in which higher sulfur lithotypes are common, if not dominant, within the lithologic profile. Three Middle Pennsylvanian coals, each representing a major resource, exemplify this. The Clintwood coal bed is the stratigraphically lowest coal bed mined throughout the coal field. In Whitley County, the sulfur content increase from 0.6% at the base to nearly 12% in the top lithotype. Pyrite in the high-sulfur lithotype is a complex mixture of sub- to few-micron syngenetic forms and massive epigenetic growths. The stratigraphically higher Pond Creek coal bed is extensively mined in portions of the coal field. Although generally low in sulfur, in northern Pike and southern Martin counties the top one-third can have up to 6% sulfur. Uniformly low-sulfur profiles can occur within a few hundred meters of high-sulfur coal. Pyrite occurs as 10-50 [mu]m euhedra and coarser massive forms. In this case, sulfur distribution may have been controlled by sandstone channels in the overlying sediments. High-sulfur zones in the lower bench of the Fire Clay coal bed, the stratigraphically highest coal bed considered here, aremore » more problematical. The lower bench, which is of highly variable thickness and quality, generally is overlain by a kaolinitic flint clay, the consequence of a volcanic ash fall into the peat swamp. In southern Perry and Letcher counties, a black, illite-chlorite clay directly overlies the lower bench. General lack of lateral continuity of lithotypes in the lower bench suggests that the precursor swamp consisted of discontinuous peat-forming environments that were spatially variable and regularly inundated by sediments. Some of the peat-forming areas may have been marshlike in character.« less

Morphology and facies of the alluvial-fan sedimentation in the Kangra Valley, Himachal Himalaya

A number of alluvial fans, having an average width (E-W) of 10–15 km and length (N-S) of 8–15 km, have been mapped using the LANDSAT TM imageries on 1:250,000 scale in the Kangra Valley of Himachal Himalaya. This important geomorphic zone of alluvial fans is confined between the foot of the Dhauladhar Range and the Siwalik ridges. These fans are gently sloping from north to south and are slightly dissected having distinct horizons of glacial, glacio-fluvial, fluvial, lacustrine and loessic sediments derived from the Dhauladhar granitic complex, Dharamsala and Siwalik Formations during the glacial and interglacial climatic stages of the Quaternary period. The vertical lithological profiles of these fans show a dominance of gravelly (nearly 60%) facies along with other lithofacies associations representing a braided-river depositional environment. In general, the thickness of fan sediments ranges between 90 and 120 m. The vertical facies are subdivided into three main facies, i.e. lower-, middle- and upper-fan facies, showing distinct sediment characteristics. The presence of glacial moraines and clay-rich debris-flow deposits is significant in the upper-fan facies. The middle-fan facies is gravel-dominated along with some interbedded sandy channel-fill deposits, whereas the lower-fan facies is composed of sand, silt and mud. The genesis of these three fan facies is closely related with the uplift of the source area and climatic changes during the Pleistocene period.

British Geological Survey thematic geology maps of Quaternary deposits in Scotland

Abstract This paper describes the portrayal of the surface distribution of Quaternary deposits (drift) in a range of maps prepared by the Geological Survey (Scotland). It considers three methods of classification involving the use of 1. the familiar BGS symbol scheme, 2. the descriptive lithological codes of thematic map packages and 3. an alphabetical Classification adopted in a recent thematic study of the Clyde valley. The three dimensional distribution of Quaternary deposits has rarely been portrayed in map form. A lithological profile scheme, also prepared as part of the Clyde valley project, is advocated as an appropriate method of representing the third dimension in complex sequences.

Basaltic replenishment of the Rhum magma chamber: evidence from unit 14

A detailed geochemical and lithological profile through unit 14 of the Rhum Eastern Layered Series is presented and interpreted to trace the evolution of this cyclic peridotite-troctolite unit. The lower 15.5 m of the unit are peridotite which has an abrupt contact with the upper 35.5 m of troctolite. Numerous thin subsidiary peridotites occur within the troctolite. Variation in the modes, whole rock 87 Sr/ 86 Sr ratios, and Ni and Fo in olivine provide most information about the evolution of the unit. Discontinuities in these parameters divide the unit into six subunits: (I) the lower peridotite, (II) the middle main peridotite, (III) the upper main peridotite and lowermost troctolite, (IV) the middle troctolite, (V) the upper troctolite and (VI) the disturbed troctolite. These subunits are interpreted as the result of magma replenishment by picritic and by basaltic magmas. Field evidence suggests that the subsidiary peridotites are later sills intruded into solid or semi-consolidated troctolite. The olivine Fo and Ni values are similar to those of surrounding troctolite suggesting either re-equilibration with, or assimilation of, the troctolite. Comparison with unit 10 shows that the unit 14 resident basaltic liquid was more mafic than that of unit 10. This factor, along with the basaltic replenishment, can explain many of the differences in geochemical and lithological variation between the two units.

Analysis of variance in investigations on anisotropy of Cu ore deposits

The problem of variability of copper grades and ore thickness in the Lubin copper ore deposit in southwestern Poland is presented. Results of statistical analysis of variations of ledge parameters carried out for three exploited regions of the mine, representing different types of lithological profile show considerable differences. Variability of copper grades occurs in vertical profiles, as well as on extension of field (the copper-bearing series). Against the background of a complex, well-substantiated description of the spatial variability in the Lubin deposit, a methodology is presented that has been applied for the determination of homogeneous ore blocks. The method is a two-factorial (cross) analysis of variance with the special tests of Tukey, Scheffe and Duncan. Blocks of homogeneous sandstone ore have dimensions of up to 160,000 m2 and 60,000 m2 in the case of the Cu content parameter and 200,000 m2 and 10,000 m2 for the thickness parameter.

Ein geochemisches Profil durch den Lias alpha (zur Frage der Entstehung des Erdöls)

A systematic study of trace elements and isotopes in lithological profiles and connected oils might lead to the determination of source rocks. This paper is a first attempt in this line; results will be conclusive only after a study of the whole stratigraphical sequence has been completed. There is practically no difference between the ratio 12C: 18C in bituminous shales and oils from the Lias alpha. It seems that during bituminization and oil-forming the ratio is changed as little as in the forming of coals. No connexion was found between degree of salinity of sedimentational environment, and 12C: 13C ratio of oils present in such sediments. Of trace metals, oils contain notably less Cr than the shales of their vicinity; the same relationship is observed between tars (“oils”) and their parent oil shales.