Post Compaction Research Articles

#38 : Maternal Age Affects Morula Compaction and Cell Polarity of Human Embryos

Background and Aims: With the exception of chromosome segregation errors, the molecular and biochemical mechanisms responsible for advanced maternal age (AMA)-related reduced embryo developmental competence remain unclear. In women of AMA, the blastocyst formation rate has been reported to decline due to an increase in embryo arrest at the morula stage. Therefore, we aimed to reveal the impact of AMA on cellular events during compaction, as assessed using morphokinetic analysis. We also assessed the possible influence of AMA on the expression of cell polarity markers, yes-associated protein (YAP) and protein kinase C-[Formula: see text] (PKC[Formula: see text]), during blastomere compaction. Method: We retrospectively analysed 2,058 fertilized oocytes, which were stratified by maternal age according to the Society for Assisted Reproductive Technology classification (< 35, 35-37, 38–40, 41–42, and > 42 years). The effects of AMA were assessed in relation to embryo morphokinetics and morphological alterations. Furthermore, 20 voluntarily donated human embryos were used for immunofluorescence staining of YAP and PKC-[Formula: see text]. Results: Delayed embryonic compaction and an increased number of extruded blastomeres post compaction were observed in the > 42-year group. The time interval from the eight-cell stage to compaction initiation was prolonged with increasing age. The number of YAP-positive cells in the outer cells of the morulae was significantly higher in the young age group than in the AMA groups. The PKC[Formula: see text] fluorescence intensity in the cortical region of the morulae was significantly lower in the AMA groups than in the young age groups. Conclusion: Delayed compaction and blastomere extrusion occur more frequently in embryos from women of AMA due to insufficient regulation of cell polarity, which may lead to morula arrest. Further research is required to reveal the impacts of AMA on the mechanism underlying the expression of cell polarity factors and develop methods to avoid AMA-associated morula arrest.

Metabolic Activity of Human Embryos after Thawing Differs in Atmosphere with Different Oxygen Concentrations.

The vitrification of human embryos is more and more frequently being utilized as a method of assisted reproduction. For this technique, gentle treatment of the embryos after thawing is crucial. In this study, the balance of amino acids released to/consumed from the cultivation media surrounding the warmed embryos was observed in the context of a cultivation environment, which was with the atmospheric oxygen concentration ≈20% or with a regulated oxygen level—hysiological (5%). It is the first time that total amino acid turnover in human embryos after their freezing at post compaction stages has been evaluated. During this study, progressive embryos (developed to blastocyst stage) and stagnant embryos (without developmental progression) were analyzed. It was observed that the embryos cultivated in conditions of physiological oxygen levels (5% oxygen) showed a significantly lower consumption of amino acids from the cultivation media. Progressively developing embryos also had significantly lower total amino acid turnovers (consumption and production of amino acids) when cultured in conditions with physiological oxygen levels. Based on these results it seems that a cultivation environment with a reduced oxygen concentration decreases the risk of degenerative changes in the embryos after thawing. Therefore, the cultivation of thawed embryos in an environment with physiological oxygen levels may preclude embryonal stagnation, and can support the further development of human embryos after their thawing.

Lamination of biconvex tablets: Numerical and experimental study

Capping and lamination are common industrial problems during the manufacturing of pharmaceutical tablets. Even if they are commonly treated together, these phenomena correspond to different failure patterns of the tablet and, as a consequence, to different mechanisms of cracking. In this work, a specific case of lamination of biconvex tablets was studied. It corresponds to a breakage into two parts of the tablets along a failure plan normal to the compression direction and located approximately at the center of the tablet band.Simulation with finite element method made it possible to propose that this kind of failure is promoted by tensile stresses localized at the center of the tablet that are induced by the residual die wall pressure and the tablet shape. Moreover, these stresses are favored by a small band thickness. Experimental results confirmed these hypotheses and also showed that this kind of lamination was favored by a high compaction pressure.As the crack is formed at the center of the tablet, it may not propagate until the tablet band. Failure may thus remain undetected by external visual examination. X-ray tomography made it possible to observe central cracks inside the tablet without tablet breakage. The possibility to have such cracks inside the tablet must be considered during tablet development as, even if not detected just after compression, they could lead to tablet failure during post compaction events.

Assessment of soil compaction properties based on surface wave techniques

Soil compaction plays an important role in every construction activities to reduce risks of any damage. Traditionally, methods of assessing compaction include field tests and invasive penetration tests for compacted areas have great limitations, which caused time-consuming in evaluating large areas. Thus, this study proposed the possibility of using non-invasive surface wave method like Multi-channel Analysis of Surface Wave (MASW) as a useful tool for assessing soil compaction. The aim of this study was to determine the shear wave velocity profiles and field density of compacted soils under varying compaction efforts by using MASW method. Pre and post compaction of MASW survey were conducted at Pauh Campus, UniMAP after applying rolling compaction with variation of passes (2, 6 and 10). Each seismic data was recorded by GEODE seismograph. Sand replacement test was conducted for each survey line to obtain the field density data. All seismic data were processed using SeisImager/SW software. The results show the shear wave velocity profiles increase with the number of passes from 0 to 6 passes, but decrease after 10 passes. This method could attract the interest of geotechnical community, as it can be an alternative tool to the standard test for assessing of soil compaction in the field operation.

Laboratory evaluation of rutting and moisture damage resistance of glass fiber modified warm mix asphalt incorporating high RAP proportion

In one hand, increasing pollution and global warming as one of the most important environmental concerns, increasing the price of asphalt, and on the other hand, the introduction of the transportation industry as one of the most common contaminant of environment raise the popularity of the use of warm mix asphalt (WMA) mixtures containing high percent of recycle asphalt pavement (RAP) in the construction of the asphalt pavement. This paper describes a laboratory effort that studied glass fiber modified warm mix asphalt mixtures with RAP contents of 0, 20, 40 and 50% to enhance resistance of mixture to rutting and moisture susceptibility. Parameters obtained from KNTU Wheel track test including the post compaction, stripping inflection point, dynamic stability and final cycles for 20mm and 12.5mm rutting depth were employed to evaluate rutting resistance and moisture sensitivity of the aged as well as the unaged samples. The results showed the improving impact of glass fiber and RAP percent on the performance of the WMA mixture.

Influence of Post Compaction on the Moisture Sensitive Resilient Modulus of Unbound Granular Materials

The impact of moisture on the resilient modulus (MR) of unbound granular materials (UGMs) was investigated based on repeated load triaxial (RLT) tests and considering the effect of post compaction (PC) from cyclic loading. Results showed that although MR decreases with increased moisture, it may appear to increase with increased moisture if the PC process is aided by moisture for a relatively large number of load applications. When limited PC was involved, the parameter k1 of the k-θ model decreased with increased moisture while the parameter k2 was unaffected. On the other hand, when significant amount of PC took place, k2 increased with increased moisture. The mechanistic-empirical pavement design guide (MEPDG) model worked well to capture the influence of moisture on the stiffness when MR decreased with increased moisture. However, it did not work when MR increased with increased moisture due to the PC effect. On the other hand, an alternative approach expressing k1 and k2 as functions of moisture worked well for both situations. Generally, this study suggested that the effect of PC should be considered in modelling the impact of moisture on MR for better accuracy.

Moisture influence on the resilient deformation behaviour of unbound granular materials

The influence of moisture on the resilient deformation properties of unbound granular materials was investigated based on repeated load triaxial tests. Results showed that the resilient modulus (MR) decreased with increasing moisture for a relatively low number of load cycles (N) where the deformation behaviour was mostly resilient with a negligible amount of associated accumulated permanent deformation (PD). Modelling attempts on this behaviour were quite satisfactory. Furthermore, the MR showed an increasing trend with increasing moisture, up to the optimum, when the N was relatively large with a significant amount of accumulated PD. Above the optimum, the MR generally decreased. Further investigation suggested that moisture aided the post-compaction (PC) and possible particle rearrangement that resulted in the increased PD and increased MR. The existing model did not work in this case indicating that the effect of PC on MR should be considered in modelling.

174. ATMOSPHERIC OXYGEN ALTERS THE EMBRYONIC METABOLOME AS QUANTIFIED BY CARBOHYDRATE UPTAKE AND AMINO ACID UTILISATION

Oxygen regulates embryo development at both the cleavage and post compaction stages. In this study we investigated the effects of atmospheric oxygen during the preimplantation stages, on the post-compaction embryonic metabolome through quantification of glucose consumption and amino acid utilization. Zygotes obtained from F1 hybrid mice (C57BLxCBA) were randomly allocated to either 5 or 20% oxygen. In the first experiment, following the first 48 h of culture, embryos were cultured individually in 1 μL drops of modified G2 medium (0.5 mM glucose) and moved to fresh drops of medium every 24 h. The glucose concentration in the spent media samples, including controls containing no embryo, was determined by microfluorimetry. In the second experiment, embryos which had developed to the early blastocyst stage after 72 h were cultured for a further 24 h in groups of 10 in 2 μL drops of G2. Analysis of amino acid utilization was performed using liquid chromatography-triple quadrupole mass spectrometry. Glucose consumption by embryos cultured in 5% oxygen was significantly greater on day 4 and day 5 (4.89 ± 0.29 and 6.13 ± 0.41 pmol/embryo/h) compared to embryos cultured in 20% oxygen (2.59 ± 0.40 and 5.09 ± 0.28 pmol/embryo/h; P < 0.05). In contrast amino acid utilisation by embryos cultured in 5% oxygen was significantly less than embryos cultured in 20% oxygen (P < 0.05). The data generated will help to determine the aetiology of oxygen toxicity to the preimplantation embryo. Higher glucose utilisation by embryos in 5% oxygen is consistent with their improved development. Conversely, the increased utilisation of amino acids by blastocysts in 20% oxygen may reflect an adaptation to increased oxidative stress as a result of culture in a non-physiological oxygen concentration. This study demonstrates that atmospheric oxygen during the preimplantation period perturbs the embryonic metabolome which results in a compensatory increase in amino acid utilisation.

Liquisolid Systems to Improve the Dissolution of Furosemide

A liquisolid system has the ability to improve the dissolution properties of poorly water soluble drugs. Liquisolid compacts are flowing and compactable powdered forms of liquid medications. The aim of this study was to enhance the in vitro dissolution properties of the practically water insoluble loop diuretic furosemide, by utilising liquisolid technique. Several liquisolid tablets were prepared using microcrystalline cellulose (Avicel® pH-101) and fumed silica (Cab-O-Sil® M-5) as the carrier and coating materials, respectively. Polyoxy-ethylene-polyoxypropylene-polyoxyethylene block copolymer (Synperonic® PE/L 81); 1,2,3-propanetriol, homopolymer, (9Z)-9-octadecenoate (Caprol® PGE-860) and polyethylene glycol 400 (PEG 400) were used as non- volatile water-miscible liquid vehicles. The liquid loading factors for such liquid vehicles were calculated to obtain the optimum amounts of carrier and coating materials necessary to produce acceptable flowing and compactible powder admixtures viable to produce compacts. The ratio of carrier to coating material was kept constant in all formulations at 20 to 1. The formulated liquisolid tablets were evaluated for post compaction parameters such as weight variation, hardness, drug content uniformity, percentage friability and disintegration time. The in-vitro release characteristics of the drug from tablets formulated by direct compression (as reference) and liquisolid technique, were studied in two different dissolution media. Differential scanning calorimetry (DSC) and Fourier-Transform infrared spectroscopy (FT-IR) were performed. The results showed that all formulations exhibited higher percentage of drug dissolved in water (pH 6.4–6.6) compared to that at acidic medium (pH 1.2). Liquisolid compacts containing Synperonic® PE/L 81 demonstrated higher release rate at the different pH values. Formulations with PEG 400 displayed lower drug release rate, compared to conventional and liquisolid tablets. DSC and FT-IR indicated a possible interaction between furosemide and tablet excipients that could explain the dissolution results. Caprol® PGE-860, as a liquid vehicle, failed to produce furosemide liquisolid compacts.

The Effect of Post Hot Compaction on Crystallinity and Thermal Behavior of Ultra-High Molecular Weight Polyethylene Fiber Laminates

Thermal compacting of previously prepared ultra-high molecular weight polyethylene (UHMWPE) fiber laminates can raise its melting temperature and crystallinity. In this article, thermal shrinkage and the effect of post hot compaction on a commercial UHMWPE fiber laminate at various temperatures was investigated. The temperature range of post hot compaction was between 115 and 145°C, while other processing parameters like pressure, time, and cooling rate were kept constant during compaction. The shrinkage of the fiber laminates increased slowly up to 138°C; as soon as the temperature passed 140°C, the shrinkage increased rapidly and reached its maximum value very quickly. The crystallinity of the fiber laminates increased with rising temperature up to 135°C, then decreased at 145°C.

Coaxial Shear Test and Wheel Tracking Tests for Determining Porous Asphalt Mechanical Properties

ABSTRACT Performance oriented test procedures are compared and discussed with respect to their suitability for porous asphalt optimization and for development of improved mix design. Coaxial shear tests and wheel tracking tests were carried out in order to compare the properties of both theoretically and empirically designed porous asphalt specimens. The specimens were produced using an improved theoretical mix design approach for porous asphalt. This method is based on a packing theory for aggregate grading optimization, reducing the post compaction effects on the pavement under traffic. The problems with porous asphalt arise from premature aging and therefore laboratory aging of the mix was used for the simulation of in-situ condition. As presented in this paper the test results vary significantly with aging as seen in the rutting behavior and shear modulus. The packing theory leads, in many cases, to porous asphalt mixes with superior quality as compared to traditional standard mixes provided that the influence of the binder is considered accordingly.

238.Determination of differentially displayed oxygen-sensitive genes in bovine blastocysts

Oxygen-regulated gene expression in the bovine embryo contrasts markedly with that observed in the mouse. Under low (2%) oxygen moderate changes in gene expression are observed in the bovine blastocyst, compared with 3- to 4-fold increases in the mouse. We have determined that these moderate gene expression changes are most likely regulated by Hypoxia-Inducible Factor (HIF)-2 transcription factor activity in the bovine, in the absence of HIF1, although HIF2 target genes are largely unknown. The aim of this study was to screen, by differential display RT-PCR, for putative oxygen-regulated transcripts that might confer developmental competence in blastocysts cultured under varying oxygen atmospheres post compaction. In vitro-produced bovine blastocysts were generated using standard protocols. Compact morulae were randomly allocated to treatments under either 2%, 7% or 20% oxygen for 72 h from Day 5. Blastocyst RNA was isolated using TriReagent and samples were reverse transcribed using Superscript II. cDNA was amplified using 10-mer primers in reactions containing 32Pα-labelled dCTP. Resulting bands were detected by autoradiography, excised, purified and ligated into pGEMT vectors for transformation and sequencing. Seven clones were identified as having high homology with known sequences in GenBank. Real-time PCR was undertaken to confirm oxygen-regulation using Sybr green master mix. Myotrophin mRNA was significantly increased following 2% oxygen culture, compared with 20% cultured blastocysts (P�<�0.01), as was GLUT1 (P�<�0.01). The expression of anaphase-promoting complex showed a significant association with oxygen, being higher in 2% cultured blastocysts (P�<�0.05). Acetyl-coA-acetyltransferase I, chronic myelogenous leukemia tumor antigen (CML66), cyclin I, NADH dehydrogenase subunit 2 and ribonucleotide reductase M1, genes identified using differential display, were not altered by post compaction oxygen concentration. This study has identified potentially HIF2-specific regulated genes, and supports the hypothesis that reduced oxygen concentrations post-compaction may influence bovine embryo development through oxygen-regulated changes in gene expression.

Effect of the oxidative phosphorylation uncoupler 2,4-dinitrophenol on hypoxia-inducible factor-regulated gene expression in bovine blastocysts

In cattle embryos, development to the blastocyst stage is improved in the presence of 10 micro;m 2,4-dinitrophenol (DNP), an uncoupler of oxidative phosphorylation, coincident with an increase in glycolytic activity following embryonic genome activation. The present study examined redox-sensitive gene expression and embryo development in response to the addition of DNP post-compaction. 2,4-Dinitrophenol increased the expression of hypoxia-inducible factor 1alpha and 2alpha (HIF1alpha, HIF2alpha) mRNA. Although HIF1alpha protein remained undetectable in bovine blastocysts, HIF2alpha protein was localised within the nucleus of trophectoderm and inner cell mass (ICM) cells of blastocysts cultured in the presence or absence of DNP, with a slight increase in staining evident within the ICM in blastocysts cultured in the presence of DNP. However, the expression of GLUT1 and VEGF mRNA, genes known to be regulated by HIFs, was unaffected by the addition of DNP to the culture. Although the development of Grade 1 and 2 blastocysts was unaltered by the addition of DNP post compaction in the present study, a significant increase in the proportion of ICM cells was observed. Results indicate that 10 microm DNP improves the quality of bovine embryos, coincident with increased HIF2alpha protein localisation within ICM cells and increased HIFalpha mRNA levels. Therefore, the results demonstrate redox-regulated expression of HIF2.

012.Metabolic determinants of implantation success and programming long term viability in embryos

It has long been recognised that energy substrate supply and metabolism are key determinants of early embryo development during in vitro culture. Recently it has been revealed that exposure to suboptimal metabolic environments during early embryo development can 'programme' subsequent development, leading to perturbed fetal development. For example, amino acid uptake profiles during early cleavage have been found to predict subsequent embryo development and potentially implantation success. However, the by-product of amino acid metabolism, ammonium, has also been found to significantly alter development, possibly through perturbed methylation of imprinted genes. Our own work has focussed on the role of oxygen availability and subsequent embryo development. Somatic cells respond to changing oxygen concentration by altering intracellular REDOX state (the balance between oxidative and reductive power within a cell), which in turn can alter transcription via REDOX-sensitive transcription factor activity. Furthermore, oxygen is known to have direct effects on transcriptional activity via the hypoxia-inducible factors (HIFs), transcription factors whose stability and DNA-binding activity are directly regulated by pO2, in particular under hypoxic conditions. Using a mouse model, we have demonstrated that reducing pO2 from 50�mmHg to 15�mmHg during the compaction and blastulation periods alone significantly alters expression patterns of oxygen-sensitive genes (such as glucose transporters), without significantly altering developmental progression to the blastocyst stage. Following transfer, embryos cultured under 15�mmHg O2, despite similar implantation rates, produced fewer viable and lighter fetuses than in vivo-derived control embryos or those cultured in either atmospheric or 50�mmHg pO2. This demonstrates that mouse embryos are sensitive to changes in their metabolic state during the post compaction period and that operating through causal pathways, the environment during this period of development can significantly affect subsequent developmental potential. Ironically, bovine embryo development appears to benefit under a low O2 concentration. Furthermore, HIF protein stability appears to differ between the two species, which may be the underlying cause for the differences in gene expression and developmental competence.

Trial Program Study of Dynamic Compaction Earth Work in Taiwan

A thermal power plant is planned to be built at Taichung Harbor area, and the construction site is located on a hydraulic fill. The medium-to-fine, loose [ N value of the Standard Penetration Test (SPT), < 10] sand deposits on the hydraulic fill will be subject to liquefaction, and because of this, soil improvement is required. Dynamic compaction is thus far considered one of the most appropriate methods used to solve liquefaction, and therefore, a trial program was initiated to obtain ongoing construction details for the whole construction site. The trial area was divided into three sections (Sections A, B, and C) to carry out three different trials. For Section A, the drop weight is 18 Mg, the drop height is 22 m, the grid spacing is 4 m, and the drop number is 8. For Sections B and C, the drop weights are 25 Mg, the drop heights are 25 m, grid spacings are 5 and 6 m, respectively, and drop numbers are 10 and 40, respectively. To achieve a better result in densifying the ground surface, a post-compaction program is introduced into this project before roller compaction is performed. During the post compaction, all trials have drop weights of 13.88 Mg, drop heights of 10 m, and a grid spacing of 2 by 3 m for Section A and a grid spacing of 3 by 3 m for Sections B and C. Results of improvement are expressed as the N value of SPT (SPT- N) and cone resistance, qc. In addition, the excess pore water pressure was also investigated during compaction. Findings indicated that either the SPT- N or the Cone Penetration Test qc improved about 1.5 to 2.0 times. Satisfactory results were also detected for the post compaction. Comparison and analysis showed that the program used for the Section B trial, that is, the trial program with application of medium energy, is the most effective program for use in the whole project. In addition, the soil particle velocity caused by tamping is found to be less than 30 mm/s and will cause no tangible effect on adjacent structures.

Effect of moisture sorption on tabletting characteristics of spray dried (15% amorphous) lactose.

Spray dried (15% amorphous) lactose absorbs moisture when exposed to humidity. At 57% relative humidity (RH), the moisture uptake was 1.5%. It is suggested that the moisture is preferentially taken up in the amorphous regions, thereby increasing the actual moisture content in the amorphous parts up to 10%. The moisture uptake reduced the glass transition temperature below the operating temperature and thereby transformed the amorphous regions from a glassy to a rubbery state, setting up conditions for crystallisation of the lactose. Compaction of dry spray dried lactose led to a relatively low initial tablet strength. However, when pre-exposed to 57% RH for a short time period (2 to 4 hours) before compaction, the initial tablet strength increased markedly. This was due to moisture uptake which resulted in a higher molecular mobility of the amorphous spray dried lactose, and to an increase in plastic flow. Post compaction storage of tablets containing amorphous regions of spray dried lactose at 57% RH resulted in an increased tablet strength after 4 hours due to crystallisation. Spray dried lactose exposed to 57% RH for more than 6 hours before compaction led to the lowest initial tablet strength. Crystallisation of the amorphous regions of the spray dried lactose occurred before tabletting. No increase in tablet strength was noted on post compaction storage for these tablets.

Moisture adsorption and tabletting. III. Effect on tablet strenght-post compaction storage time profiles

The effect of air humidity on the post compaction changes in tensile strength of tablets of three test materials, saccharose, sodium chloride and dicalcium hydrogen phosphate dihydrate, was assessed during storage of the tablets for up to 168 h. For saccharose and sodium chloride also the changes in tablet permeametry surface area at storage times up to 24 h was measured. For tablets of saccharose and sodium chloride, the tablet strength increased generally during the storage. An increased air humidity increased both the rate and the degree of the increase in tablet strength, i.e., the storage time after which measurements of tablet data are performed is of importance when the compactibility of a material is evaluated. However, when tablets were stored at or above the critical relative humidity, the tablet strength decreased after a few hours storage. For tablets of dicalcium hydrogen phosphate dihydrate, the tablet strength did not vary with time or storage condition. For tablets of saccharose and sodium chloride, the surface area generally decreased with storage time and the effect was more pronounced with increased storage humidity. Hence, a relationship between the tablet strength and tablet surface area was found. Thus, the changes in tablet strength during storage are probably a result of a rearrangement of solid material within the tablet which is mediated or facilitated by sorbed water.

Jurassic Subsurface Calcite Cementation, Central Gulf of Mexico: ABSTRACT

Calcite cements of subsurface origin have received increased notice in the past several years, particularly in Jurassic Smackover sequences o f the Central Gulf by Moore and Druckman in 1981. Initially, documentation of the subsurface origin of these cements centered about petrographic evidence: fractured grains encased in poikilitic cements as well as pressure dissolved grains covered with cement. Although petrographic data did indicate some burial prior to cement precipitation, burial depth at the time of cementation remained uncertain because of our general lack of knowledge relative to the failure of carbonate grains under confining pressure, elevated temperatures, and changing fluid compositions. Subsequently, study by Klosterman in 1981 and Moore and Druckman in 198 of the two phase fluid inclusions common to these cements indicated that elevated temperatures (85 to 112°C; 185 to 234°F) and saline brines similar to present Smackover fluids may have been present at the time of cement formation. If indeed the precipitation fluids were similar to present Smackover brines (ten times more saline than seawater with a ^dgr18O composition near +5), the -6.5 ^dgr18O composition of most of these cements is compatible with a temperature of 90°C (194°F) because of the strong temperature dependence of oxygen isotope fractionation. Final confirmation of the deep subsurface origin of many of these cements may well rest with their apparent equilibrium with present Smackover brines relative to radiogenic strontium. Most Sma kover brines and associated post composition poikilitic calcite cements analyzed to date show an enrichment in radiogenic strontium well above Jurassic seawater values, whereas adjacent grains have radiogenic strontium compositions near that of Jurassic seawaters. Trace element composition of these deep subsurface cements, particularly relative to total strontium, present an enigma. Although present Smackover fluids have a high Sr/Ca ratio (almost four times greater than seawater), the late subsurface cements that have presumably been derived from these fluids have Sr compositions averaging only 200 ppm, well below the values predicted by using Katz et al's 1972 distribution coefficient (1,350 ppm) or Kinsman's 1969 distribution coefficient (3,000 ppm). These discrepancies certainly indi ate that kinetic and compositional controls over trace element distribution coefficients must be reassessed for the carbonate system in the subsurface environment. The most common subsurface cement (demonstrably post compaction, coarse, clear, single unzoned crystals of a poikilitic habit) generally represents a very late stage diagenetic event. A second type subsurface cement, much less common than the first, that generally consists of an interlocked mosaic of coarse crystals, usually fills large sheltered voids, such as gastropod molds, that exhibit a complex iron zonation as seen by staining or cathodoluminescence. Isotopic composition of these zoned calcites consistently show a progressive depletion of ^dgr18O of some 4 per mil, from center to crystal termination. The lightest composition overlaps the -6.5 ^dgr18O of the late stage unzoned poikilitic cements described. These calcites, based on petrography and stable iso opic composition, seem to represent an intermediate stage of diagenesis and burial. Dissolution associated with progressive pressure solution during the first stages of burial is the most logical source of the carbonate needed for the calcite precipitation of the zoned cements. A potential source for the carbonate needed to form the late stage poikilitic calcites is deep subsurface calcite End_Page 518------------------------------ dissolution associated with hydrocarbon maturation-migration. The understanding of these subsurface cements helps decipher the diagenetic history of carbonate rock sequences during progressive burial and can be particularly helpful in timing hydrocarbon migration. End_of_Article - Last_Page 519------------

Application of Strontium Isotopes to Origin of Smackover Brines and Diagenetic Phases, Southern Arkansas: ABSTRACT

The abundance of the isotope 87Sr is variable in nature, as it is the radiogenic product of 87Rb decay. The relative amount of this Sr isotope that is dissolved in a brine, as expressed by the 87Sr/86Sr ratio, might be used as a tracer of the origin and subsequent history of the brine, including its diagenetic effects in petroleum reservoirs. Strontium isotopic analyses of 40 brines from oil fields in southern Arkansas have been conducted to investigate the sources of the dissolved Sr, the pathways of brine migration, and the relationship between the brines and diagenetic phases in the Jurassic upper Smackover Formation. The 87Sr/86Sr ratios of 33 brines from the upper Smackover lime-grainstone range from 0 7071 to 0.7101; seven brines from formations stratigraphically above the Smackover range from 0.7090 to 0.7112. Thus the Sr in these brines is variably more radiogenic than Jurassic sea water End_Page 553------------------------------ (~0.7070). The brines are from 15 oil fields within an area of approximately 2,000 mi2 (5,200 km2); the isotopic variability shows no geographic pattern in the study area. The variation in 87Sr/86Sr ratios of brines occurs to a lesser degree within individual oil fields. For example, over a distance of about 10 mi (16 km) at Walker Creek, the isotopic ratios of 11 Smackover brines range from 0.7080 in the east to 0.7086 in the west. The observation that Smackover brines are variably more radiogenic than Jurassic seawater is important because it indicates that a significant proportion of the Sr dissolved in these brines has been acquired from a source material that has not formed wholly by precipitation from Jurassic seawater. That is, some radiogenic Sr must have been added to the brines from a detrital source material. The nature and distribution pattern of the 87Sr/86Sr ratios indicate the acquisition of variable amounts of radiogenic Sr on a local basis. If the Smackover brines originated in the Louann Salt, with 87Sr/86Sr equivalent to that of Jurassic seawater, their present isotopic compositions may be the result of varying degrees of subsequent interaction with d trital sediments or they may have been produced by mixing in variable proportions with solutions containing more radiogenic Sr. Potential sources of the radiogenic Sr are the Norphlet Formation and the lower Smackover argillaceous lime-mudstone, both of which lie stratigraphically between the Louann salt and the upper Smackover, as well as the Bossier shale which interfingers with the upper Smackover in the North Louisiana salt basin. Anhydrites from the Werner and Buckner formations and from northern Louisiana salt domes, which constitute additional potential sources of brine Sr, yield 87Sr/86Sr ratios equivalent to those of Jurassic seawater. Diagenetic phases of the upper Smackover, such as post compaction calcspar cement and baroque dolomite, have 87Sr/86Sr ratios more radiogenic than Jurassic seawater, suggesting their subsurface precipitation in Sr isotopic equilibrium with Smackover brines. However, ooids and oncolites from the upper Smackover lime-grainstone yield 87Sr/86Sr ratios indicating isotopic equilibrium with Jurassic seawater. End_of_Article - Last_Page 554------------