Core Sample Data Research Articles

Origin, development and evolutionary model of shelf desertization environment in late stage of Upper Pleistocene

Based on the study of palaeo-environmental evolution in the shelves of the Eastern China Seas, the concept of “shelf desertization” in the late stage of Upper Pleistocene is defined; the environmental background and evolutionary process of shelf desertization are analysed. Study on the records of subbottom profiling and the data of core samples from shelf areas revealed that during low sea-level stages, the sedimentary environment in the exposed shelf plains was dominated by aeolian depositional process under cold and dry climatic conditions, i.e. under the action of strong winter-monsoon winds. Parts of the exposed marine strata were disintegrated, and aeolian sand dunes were formed on the disintegrated marine deposits, from which the finer sediment grains were blown away by wind and deposited in the downwind areas to form the derivative loess deposits. Thus a desertization environmental system was formed in the exposed shelf plains of the Eastern China Seas.

Acoustic Logging Based on Wellbore Resonance

Summary Wellbore resonance phenomena are the basis for a new acoustic logging method, the Stimulated Mode Acoustic Log (SMAL). The SMAL method stimulates a particular mode of wellbore vibration by exciting a resonance for that mode. Specific resonances are excited by driving an acoustic transmitter with a short tone burst of appropriate frequency. SMAL benefits include signal enhancement under adverse conditions, avoiding dispersion effects, propagating formation waves through cased and slotted liner completions, generating steady-state phase and amplitude data, and providing formation Q logs. All of these applications have arisen from studies of wellbore resonance phenomena through well logging and laboratory experiments. One means of study has been the wellbore excitation log, which shows the foot-by foot response of the wellbore to swept-frequency excitation across the acoustic band. Excitation logs show that resonances are sensitive to lithology and formation saturation conditions. Additional insight has been provided by generating standing waves under resonance conditions. This approach has led to a means of estimating a formation Q from the decay of standing tube waves. Q data, generated in this way, are consistent with laboratory data for core and quarry samples. A Q log, run through the gas, oil, and water legs of a thick Gulf Coast sand, is consistent with lab data for cores. Laboratory experiments in thick-wall pipe models have been another means of study. These field and laboratory investigations indicate that the combination of wellbore and logging tool behave somewhat like a resonance cavity for pressure waves in the wellbore fluid. Tool elements, especially the two ends, act as reflectors of fluid wave energy, giving rise to resonances and standing wave phenomena. The resonance characteristics of this cavity are dominated by the properties of the formation wall material and the coupling between the fluid and borehole wall. Other factors, such as fluid column and source resonances, play secondary roles. It is the strong dependence of resonances on formation properties that makes SMAL a valuable logging concept.

Geoacoustic seafloor exploration with a towed array in a shallow water area of the Strait of Sicily

Acoustic propagation in shallow water is greatly dependent on the geoacoustic properties of the seabottom. This paper exploits this dependence for estimating geoacoustic sediment properties from the bottom acoustic returns of known signals received on a hydrophone line array. There are two major issues in this approach: one is the feasibility of acoustic inversion with a limited aperture line array, the other is related to the knowledge of the geometry of the experimental configuration. To test the feasibility of this approach, a 40-hydrophone-4-m spaced towed array together with a low-frequency acoustic source, was operated at a shallow water site in the Strait of Sicily. In order to estimate the array deformation in real time, it has been equipped with a set of nonacoustic positioning sensors (compasses, tilt-meters, pressure gauges). The acoustic data were inverted using two complementary approaches: a genetic algorithm (GA) like approach and a radial basis functions (RBF) inversion scheme. More traditional methods, based on core sampling, seismic survey and geophone data, together with Hamilton's regression curves, have also been employed on the same tracks, in order to provide a ground truth reference environment. The results of the experiment, can be summarized as follows: 1) the towed array movement is not negligible for the application considered and the use of positioning sensors are essential for a proper acoustic inversion, 2) the inversion with GA and RBF are in good qualitative agreement with the ground truth model, and 3) the GA scheme tends to have better stability properties. On the other hand, repeated in version of successive field measurements requires much less computational effort with RBF.

Simulating vegetation dynamics and land use in a mire landscape using a Markov model

The paper consists of a dynamical approach to mire-related vegetation and land use development. Investigations were carried out on two different study levels. First, successions of mire plant communities (community or C-level), based on stratigraphical core sample data, and, second, dynamics of plant cover and land use (PC&LU) types of mire landscapes (landscape or L-level), based on sequential aerial photographs (AP), were studied.The first reveals mainly autogenic successions of plant communities over several thousand years, the second, natural and anthropogenic successions of PC&LU types over a 30 year time span.The source data for the quantitative analysis on the basis of Markov model (MM) were provided by 17 peat types as the representatives of corresponding plant communities, taken from cores through the genetic centres of mires (C-level). Nineteen PC&LU types as the representatives of hybrid systems, were deduced from AP of three time periods (L-level).The first order MM, mainly used in ecological modelling, was also applied in addition to the C-level treatment, to a more complicated investigation, i.e. L-level.As an extension of the first order MM, second order effects were modelled. For ease of analysis of three-dimensional matrices, three states of succession (after reduction 17- and 19-element classification schemes to 3 element) only were used.The treatment represented has been used to reconstruct historical development of mire plant communities and PC&LU types in mire landscapes and analyse the future development of the corresponding types. The analysis of the first and second order models and predictions made on this basis are given.

Crescent‐shaped slab slides in a submarine canyon system, Arequipa fore‐arc basin, off southern Peru

SeaMARC II side‐scan imagery and bathymetry, seismic reflection, and free‐fall core sampling data reveal the morphology, structure, and hydrology controls on the formation and development of a series of crescent‐shaped slab slides along the submarine canyon walls in the Arequipa fore‐arc basin off southern Peru. The crescent‐shaped slab slides occur in a segment of an approximately 25‐km‐long canyon course and generally accord with the meandering of the canyon course. Most of the slab slides commonly consist of four distinctive zones: the fissured zone, scarp zone, voided zone, and frontal zone. The fissured zone is developed on the crown of the sliding walls; the scarp zone is marked by scars with crescent‐shaped slip surfaces and throws ranging from 50 to 120 m. The voided zone is characterized by 1–3 km wide terraces resulting from slab‐type excavating of the seafloor. The frontal zone is normally comprised of debris materials distributed on the seafloor near the canyon thalweg; however, there is lack ...

The Reservoir Potential of the Zechstein-3 Carbonate Member (Platten), Offshore Netherlands

The Platten has been examined from 31 released and nonreleased wells, dominantly from northern P and Q quadrants, Dutch North Sea, and including a limited number of adjacent onshore wells. Wireline log interpretations have been allied with available core log, sidewall core, and ditch sample data. This has allowed a division into four broad facies associations: lower ramp, shoal shoreface, lagoonal, and the dominantly siliciclastic peritidal. Primary porosity is concentrated in ooid grainstones of the shoal/shoreface facies association. Diagenesis has also been examined. While the Platten has been broadly affected by early dolomitization, which generally occluded porosity, later diagenesis was more selective and had a significant control on porosity creation more selective and has a significant control on porosity creation as well as occlusion. Location of Platten reservoir potential is shown by facies association, diagenetic texture, and percentage porosity maps. The best reservoir conditions in the Platten exist where the shoal/shoreface facies association coincides with faults and with diagenesis associated with fluid movements through fractures. Low-temperature hydrothermal fluids are shown in this study to be the most important control on the hydrocarbon potential of the Platten in much of the P and Q quadrants.

Application of Line-Length Related Interpolation Methods to Problems in Coal Preparation—III: Two Dimensional Washability Data Interpolation

The first paper in this series' presented the mathematical basis and computational procedures for problems of interpolation of sizing and density data commonly encountered in coal preparation problems. Robust methods having the desirable property that the interpolations reduce exactly to the original data were developed. This work discusses the application of the method to two-dimensional interpolation of size-by-size density and ash data. The primary application of the method is in consistently recalculating washability information to some chosen set of size and density intervals, given sets of data defined on a different set of intervals. Such a problem occurs when preparing drill core or bulk sample data for washery calculations. No ‘model’ of coal properties or assumptions regarding the forms of the mass or ash distribution are involved. The method is consistent, objective and computationally robust.coal preparation, Coal, density distribution, interpolation, size distribution, washability.

Core sampling versus field-measured data for modeling drainage in field soils: validity of the equivalent media approach

Natural or field soils are characterized, in general, by the existence of macropores. Two approaches to modeling flow in such soils can be identified in the literature. The first describes the flow in two distinct domains: one in the soil and another in macropores, with appropriate interaction between the two systems. The second treats the whole system as a continuum with properties that are averaged over a representative control volume. This study is aimed at assessing the success of both field- and laboratory-based soil-data in representing the behavior of field soils under drainage, within a Darcian, continuum framework. Based on available data, three approaches to defining the hydraulic properties are adopted. The first two models represent closely data from undisturbed core-samples that were obtained independently from drainage measurements. The third is an approximate data model with parameters that are determined from field-measured tensiometric data during drainage. For each data model, available data are used to their fullest extent without any adjustment. The approximate data model represents best the behavior of the field soil under drainage conditions. The laboratory-based hydraulic functions, although estimated from undisturbed samples, are less successful in representing the behavior of such soils. When compared to elaborated sampling and laboratory analyses, estimating the hydraulic properties from in-situ measured tensiometric data is not only more convenient, but can also be more accurate. The study concludes that the equivalent porous-media approach is valid for modeling drainage in well-drained field soils.

Root turnover as determinant of the cycling of C, N, and P in a dry heathland ecosystem

Root production and turnover were studied using sequential core sampling and observations in permanent minirhizotrons in the field in three dry heathland stands dominated by the evergreen dwarfshrub Calluna vulgaris and the grasses Deschampsia flexuosa and Molinia caerulea, respectively. Root biomass production, estimated by core sampling, amounted to 160 (Calluna), 180 (Deschampsia) and 1380 (Molinia) g m-2 yr-1, respectively. Root biomass turnover rate in Calluna (0.64 yr-1) was lower compared with the grasses (Deschampsia: 0.96 yr-1; Molinia 1.68yr-1)). Root length turnover rate was 0.75–0.77 yr-1 (Deschampsia) and 1.17–1.49 yr-1 (Molinia), respectively. No resorption of N and P from senescing roots was observed in either species. Input of organic N into the soil due to root turnover, estimated using the core sampling data, amounted to 1.8 g N m-2 yr-1(Calluna), 1.7 g N m-2 yr-1 (Deschampsia) and 19.7 g N m-2 yr-1 (Molinia), respectively. The organic P input was 0.05, 0.07 and 0.55 g P M-2 yr-1, respectively. Using the minirhizotron turnover estimates these values were20–22% (Deschampsia) and 11–30% (Molinia) lower.

Improved Data-Analysis Method Determines Archie Parameters From Core Data (includes associated paper 24964 )

Summary. We present a data analysis approach to determine Archie parameters m and n from standard resistivity measurements on core samples. The analysis method, core Archie-parameter estimation (CAPE), results in computed water saturations that agree well with core-measured saturations. CAPE determines m and n by minimizing the error between computed and measured water saturations. The conventional method minimizes the error in nonphysical quantities. Also, CAPE provides a natural, physically meaningful method of "averaging" Archie parameters, and with an error statistic, aids in zonation of a well or reservoir into different sets of Archie parameters. Finally, we show that the Archie constant a is a weak-fitting parameter, with no physical significance, that can generally be set to unity. Introduction The conventional data-analysis method for determining the Archie parameters m and n was first presented by Archie when he introduced the Archie equation. The conventional method has remained largely unchanged, except that sometimes a constant a is added to the formation factor equation. The constant a is conventionally determined with Archie's original procedure for determining m, the only difference being that the line is not constrained to go through F = 1 when = 1. Conventional Determination of n. The conventional determination of n is based on rearranging Archie's equation. The clinical Archie equation is Sw = ...................(1) Archie did not use the constant a in his expression, but others have since added it. a is commonly used and is often referred to as part of Archie's equation, though strictly speaking it is not. In the conventional determination of n, Eq. 1 is rearranged as log(Rt)= -n log(Sw) +log(aRw/m). ...................(2) The laboratory-measured Rt and Sw points for a single core sample are plotted on loglog graph paper (Fig. 1), and a least-squares fit of log(Rt) vs. log(Sw) is made, n is obtained from the negative of the slope of the least-squares fit. Terms on both sides of the equal sign in Eq. 2 can be combined to yield log(I R) = -n log(Sw),.............(3) where I R = resistivity index (Rt/Ro), and Ro - aRw/m......................(4) Sometimes data are plotted as log(I R) vs. log(Sw). This form is mathematically equivalent to a plot of log(Rt) vs. log(Sw) and yields the same value for n. Data for several core samples are sometimes plotted as log(I R)vs. log(Sw) and a single least-squares fit is obtained. Conventional Determination of m and a. The equation assumed is the form of the formation factor traditionally associated with Archie's equation: F = a/m = Ro/Rw,................(5) where F = formation factor found from Ro/Rw, Ro = resistivity when the sample is fully water saturated (Sw = 100%), and Rw = water resistivity. Eq. 5 is rewritten as log(F) = -m log () + log(a)......(6) All core samples are used simultaneously in the plot. A least-squares fit is made of log(F) vs. log() (Fig. 2). a is sometimes fixed to unity and sometimes used as a variable to be determined. m is determined from the least-squares fit, as is a if it is not fixed at unity. Note that only points for which Sw = 1 are used, and all other points are ignored. Thus, Sw = 1 points are required for the conventional method. If Sw = 1 points are not measured directly, they are sometimes approximated by extrapolating plots of Sw vs. Rt for individual core samples. Comments on Conventional Determination of m, n, and a. The conventional method treated the determination of n as a problem independent from the determination of m and a. Thus it ignored a great deal of data in the determination of m and a namely, all points for which Sw less than 100%. We have developed a data-analysis method to determine Archie's parameters m, n, and optionally a, using standard resistivity measurements on core samples. CAPE is a mathematical procedure that does not address the physics of Archie's equation or attempt to discriminate between valid and invalid input data. Thus, poor input data will result in suspect output. Additionally, CAPE does not address the question as to whether Archie's equation is valid for the data. What CAPE does is determine the set of Archie parameters that minimizes the error in computed water saturation. Benefits from the new CAPE method are listed below. 1. CAPE-computed water saturations agree better with core-measured saturations than those conventionally computed. JPT P. 103⁁

Reservoir Delineation and Estimation of Producibility of Hydrocarbons by Organic Geochemical Logging: ABSTRACT

In highly fractured heterogeneous reservoirs, such as found in the Monterey Formation of California, routine logging runs are commonly inconclusive as to delineation of the hydrocarbon-bearing reservoir intervals. Organic geochemical well logging provides a means to identify and estimate the producibility of such intervals throughout the penetrated section. Various geochemical indices used in source rock assessment can be used to identify the presence of anomalously high levels of free hydrocarbons downhole. Many can be derived from Rock-Eval pyrolysis data of cuttings and core samples which is traditionally used as a screening tool for source rock assessment. The data from Rock-Eval can be used to identify potentially productive horizons. Well profiles of the S{sub 1}/TOC and KTR ratios highlight intervals that contain reservoired hydrocarbons, while depressed values of T{sub max} can be used to indicate high concentrations of asphaltenes. Estimations of the producibility (API gravity) of the reservoired crude may also be made by analyzing the cuttings samples using a modified pyrolysis gas chromatographic technique. Resolution of oils with API gravities of approximately 20-25{degree} or less is possible. The recognition of these heavy and extra-heavy oils prior to drill-stem testing is economically important. The application of these techniques to studies frommore » offshore California will be presented.« less

Geochemical exploration for deeply hidden ore in southeastern Hubei Province

The application of geochemical rock core sampling in the search for deeply buried or blind ore deposits is described. Several case histories are given, including: (1) tracing new blind ores below known ore bodies by studying the geometry or morphology of primary halos around the known ore bodies; (2) the discovery of deeply buried ore bodies under heavy transported overburden by utilizing the analytical data of past core samples taken on the deeply buried bedrock surface: (3) predicting the extension of ore bodies by utilizing the geochemical zoning characteristics of the ore elements; and (4) sensing the possible existence of a nearby ore body by utilizing the core analysis data of a single drill hole.

能登半島南部邑知低地帯周辺の重力構造

A detailed gravity survey was carried out over the Ochi depression, the sothern part of the Noto peninsula in central Japan. The depression is supposed to have been formed by faulting or flexure of strata. An earthquake (Nanao earthquake M=6.0) occurred around it in 1933.Terrain corrected Bouguer anomalies are calculated assuming a mean density of 2.67g/cm3. The gravity system is based on IGSN 71. The distribution of gravity anomaly shows remarkably lower gravity anomaly of about 10 mgal within the depression.The analysis of gravity anomaly by using Talwani's two dimensional method clarifies that subsurface structure under the Ochi depression can be understood as a graben structure, as suggested by geological studies. Using geological evidence and available core sample data, the depth to the per-Tertiary basement is estimated to be more than 800m in southwest region and more than 400m in northeast one.

Survey of hydrothermally-generated petroleums from the Guaymas Basin spreading center

The Guaymas Basin spreading center and hydrothermal system are generating an assortment of petroleum-like bitumens by pyrolysis of organic matter in the overlying uncosolidated sediments. Samples collected by D.S.V. Alvin from hydrothermal fields in the Southern Trough exhibit large variations in the quantities and character of the solvent-soluble organic materials. Various pyrolytic regimes combined with fluctuating thermal gradients and migration velocities may impart a compositional fractionation, possibly by differential gaseous solubilization and hydrodynamic alteration of the multi-component fluids. The data suggest that differential condensation/solidification, biodegradation, and water-washing cause selective removal of components at the seabed. Many hydrothermal oils are unlike normal reservoir petroleums, because they contain significant concentrations of polar material, due to their rapid genesis and transport and probable solubilization or advection of polar, immature components. The biomarker distributions confirm high-temperature pyrolysis at depth with variable entrainment of less thermally-mature bitumens during transport. Data for shallow core samples from the Northern Trough indicate that those locations experienced variable influx (predominantly volatiles) of a low-temperature pyrolysate.

Distributed parameter modeling of a producing vapor‐dominated geothermal reservoir: Serrazzano, Italy

The simulator SHAFT79 of Lawrence Berkeley Laboratory has been applied to a field‐wide distributed parameter simulation of the vapor‐dominated geothermal reservoir at Serrazzano, Italy. Using a three‐dimensional geologically accurate mesh and detailed flow rate data from 19 producing wells, a period of 15.5 years (from 1959 to 1975) has been simulated. The reservoir model used is based on field measurements of temperatures and pressures, laboratory data for core samples, and available geological and hydrological information. The main parameters determined (adjusted) during development of the simulation are permeabilities and much of the initial conditions. Simulated patterns of pressure decline show semiquantitative agreement with field observations. Field pressures decline overall somewhat more rapidly than predicted in the simulation. It is concluded that (1) the interface between overlying steam cap and deeper boiling aquifer remains stationary during exploitation and (2) the aquifer boils approximately uniformly throughout in response to production. Furthermore, the simulation suggests that some steam flowing to the main well field originates from deep fractures rather than from boiling in the two‐phase zones modeled. Effects of cold recharge, incomplete thermal equilibration between rock and fluid, and different assumptions regarding the depth of the steam/two‐phase interface are investigated. The reservoir model is used to extrapolate (forecast) production rates on a well‐by‐well basis through 1990. Injection of spent condensate is briefly examined, and negligible impact on field performance is predicted. Simulation methodology and ambiguity of parameter determination are discussed.

A comparison of measured and predicted compressional wave attenuation in ocean sediments

Propagation losses off the Jacksonville, Florida coast due to sedimentation volume attenuation are analyzed over a frequency range of 40 to 800 Hz and compared with the attenuation predicted by the sediment models of Biot [M. A. Biot, J. Acoust. Soc. Am. 34, 1254–1204 (1962)] and Hamilton [E. L. Hamilton, “Geoacoustic Models of the Sea Floor,” in Physics of Sound in Marine Sediments, edited by Lloyd Hampton (Plenum, New York, 1974), pp. 181–221]. A model of the bottom is first established through short range (35 to 100 m) seismic refraction measurements, and then confirmed by a low-frequency dispersion analysis of water-borne signals. Propagation losses over a range of 20 to 95 km are corrected for attenuation due to cylindrical spreading and conversion to shear waves at the water-sediment interface. Bottom attenuation coefficients due to compressional wave volume attenuation in the sediment are then calculated. Core and grab sample data are used in the sediment models of Biot and Hamilton to predict compressional wave bottom attenuation coefficients for comparison with the experimental results.

Some Aspects of Polymer Retention in Porous Media Using a C14-Tagged Hydrolyzed Polyacrylamide

Abstract Numerous single-phase flow and oil-recovery tests were carried out in unconsolidated sands and Berea sandstone cores using C14-tagged, hydrolyzed polyacrylamide solutions. The polymer-retention polyacrylamide solutions. The polymer-retention data from these flow tests are compared with data obtained from static adsorption tests. Polymer concentrations in produced water in Polymer-flooding tests were studied using various Polymer-flooding tests were studied using various polymer concentrations, slug sizes, salt polymer concentrations, slug sizes, salt concentrations, and different permeability sands. Results show that polymer retention by mechanical entrapment had a dominant role in determining the total polymer retention in short sand packs. However, the role of mechanical entrapment was less in the large-surface-area Berea cores. In oil-recovery tests, high polymer concentrations were noted at water breakthrough in sand-pack experiments, an indication that the irreducible water was not displaced effectively ahead of the polymer slug. However, in similar tests with Berea cores, a denuded zone developed at the leading edge of the polymer slug. polymer slug. The existence of inaccessible pore volume to polymer flow is shown both in sand packs and in polymer flow is shown both in sand packs and in sandstone cores. Absolute polymer-retention values show an almost linear dependency on polymer concentration. The effect of polymer slug size on absolute polymer retention is also discussed. Distribution of retained polymer in sand packs showed an exponential decline with distance. The "dynamic polymer-retention" values in short sand packs showed much higher vales than the ‘static packs showed much higher vales than the’ static polymer-adsorption" values caused by mechanical polymer-adsorption" values caused by mechanical entrapment. The mechanism of polymer retention in silica sands and sandstones is described, based on the observed phenomenon. Introduction It is widely recognized that, as polymer solution flows in a porous medium, a portion of the polymer is retained. It is evident that both physical adsorption and mechanical entrapment contribute to polymer retention. The question of the relative importance of these retention mechanisms has not been studied adequately. The effect of residual oil saturation on polymer retention and the polymer retention during the displacement of oil from porous media has also been studied inadequately. Mungen et al. have reported a few data on polymer concentration in produced water in oil-recovery tests. However, no produced water in oil-recovery tests. However, no comparison was made between polymer retention at 100-percent water saturation and at partial oil saturation. It has been shown that the actual size of the flowing polymer molecules, with the associated water, can approach the dimensions of certain smaller pores found in porous media. Therefore, an inaccessible pore volume exists in which no polymer flow occurs. In this study, the existence polymer flow occurs. In this study, the existence of inaccessible pore volume is shown clearly, both in sand and sandstone. Although polymer-retention values have been reported for various conditions, correlation is difficult because of the differing conditions of measurements. The effect of slug size, polymer concentration, salinity, and type of porous media on polymer retention has not been systematically studied. The purpose of this study was to develop answers to these questions, rather than to provide adsorption data for actual field core samples. For this reason, unconsolidated silica sands were used in most of the experiments reported. This permitted identical, uniform single-layer and multilayer porous media to be constructed for repeated experiments under varying test conditions. Some experiments were also carried out in Berea sandstone cores to determine whether sand-pack results can be extrapolated to consolidated sandstones. Using a C 14-tagged polymer provided a very rapid, simple, and accurate polymer-concentration determination technique. SPEJ P. 323

A STUDY OF THE SOIL FAUNA IN A MATURE STAND OF RED SPRUCE (PICEA RUBENS) IN THE UNIVERSITY OF NEW BRUNSWICK FOREST

AbstractThis investigation was concerned with fauna above and within the litter, fermentation, and humus layers of the soil in a mature stand of red spruce (Picea rubensSarg.). The following six microsites were designated for sampling: "open" and "closed" hollows, flats, and hummocks. "Open" and "closed" referred to the space among the tree crowns directly above the microsites. Three sampling techniques, namely core samplers, pitfalls and Tullgren funnels, were employed. Samples were collected weekly from spring to winter in 1966 and 1967 by all methods except that in 1966 Tullgren funnel samples were collectell biweekly. Collected fauna comprised five Phyla, 11 classes, 28 orders, and approximately 124 families. The transformed core sample and Tullgren funnel data were analyzed using an ANOVA (2-way classification) procedure. Transformed pitfall data required an ANOVA (2-way classification, with sampling) procedure. The core sample and Tullgren funnel methods indicated a significant difference (α = 0.10) among microsites based on total weekly (or biweekly) faunal catches in all but one case (which approached significance). In 1966 there were no significant differences (α = 0.10) among the pitfall microsites but in 1967 there were. In all cases there were significant differences (α = 0.10) in the total weekly or biweekly catches of fauna from the various microsites.

A Virtual Guide to Rocks, Fossils and Geology

Geological interpretation and comprehension is optimally achieved with first hand access and exposure to data and materials. However, there are many scenarios where immediate access to meso-scale (<m) and macro-scale (>km) data is unattainable. This is particularly evident for remote regions and educational environments where field visits are often limited. In order to augment conventional geological investigations, we propose the use of 3D digital data of Earth materials, e.g. rocks, fossils, minerals and core samples. The approach followed will facilitate the preservation and global sharing of meso-scale samples in a manner that links and visualizes referential connections, presents the dynamic and interactive nature of geology and promotes transformations between 2D and 3D. The objective of this research is to optimize the data collection process of a 3D close-range (desktop) laser scanner for a variety of meso-scale samples of rocks and fossils used for geological applications. The ultimate goal is to embed the meso-scale samples in an interactive macro-scale environment (GIS). The optimization process for the desktop laser scanner is not trivial as it must be evaluated on a sample-by-sample basis until a sufficiently heterogeneous and significant database of samples is acquired. This work focuses on comparing true samples with digitized models and modifying the scanning process and post-processing to achieve realistic and repeatable models. Parameters tested include target-sensor baselines, resolution of scanned samples and integration into an immersive 3D geospatial environment.

FACTORS INFLUENCING THE PORE VOLUME OF FINE‐GRAINED SEDIMENTS UNDER LOW‐TO‐MODERATE OVERBURDEN LOADS1

An anomalous increase of pore volume with increasing depth in the range 0—1,900 ft. occurs in fine‐grained sediments along the east side of the San Joaquin Valley of Cali‐ fornia. Several possible causes for the anomaly were inferred from a literature search and from study of the core samples. Statistical analyses of the core sample data suggest the principle causes to be variations in particle size, the diatom‐skeleton content, and the type of exchangeable cation adsorbed by the clay‐mineral constituents of the sediments.