bluuebunny/crossref_metadata_2025 huggingface dataset:
A model for induced seismicity caused by hydrocarbon production in the Western Canada Sedimentary Basin
Authors: Baranova Valentina , Mustaqeem Azer , Bell Sebastian
Published: April 2011

Over the past three decades, a significant number of small-magnitude and shallow earthquakes have occurred in the Western Canada Sedimentary Basin and are located along its western flank near areas of oil and gas production. One of the better documented examples is the swarm of earthquakes associated with the Strachan field, in the Alberta foothills. A model based on Segall's poroelastic theory is developed to account for the occurrence of earthquakes below the Strachan reservoir. Using this methodology, we show that the earthquake of 19 October 1996, underneath the Strachan field, was most probably triggered by gas extraction. The numerical model also implies that gas extraction would cause subsidence and localized changes in in situ stress magnitudes. There is a strong correlation between rates of production and the number of seismic events, but the onset of major seismic activity postdates the commencement of production by approximately 5 years. Poroelastic modelling can account neatly for this observed delay. The modelled stress changes due to gas extraction point to a regime which favours reverse or thrust faulting that is compatible with stress magnitude measurements in the area. The proposed mechanism involves volume changes which decrease the vertical stress Sv and increase the larger horizontal stress SHmax. The mean stress increase beneath the reservoir appears to be small, but increasing the deviatoric stress permits Mohr-Coulomb failure. As a result, the initially high rate and long history of gas extraction appear likely to be the main trigger for the seismicity beneath the Strachan field.
Geology and U-Pb geochronology of rocks of the Eokuk Uplift: a pre-2.8 Ga basement inlier in the northwestern Slave Province, Nunavut, Canada
Authors: Emon K A , Jackson V A , Dunning G R
Published: April 2011

Rocks of the Eokuk Uplift have been mapped in detail along the coast of Coronation Gulf and 10 key units have been dated by U-Pb analysis of zircon, monazite, and titanite. The combined data indicate that this inlier of the Slave Province has a >3.2 Ga crustal component, evidence of a granulite-grade orogenic event predating 2.8 Ga and a lack of evidence for any significant orogenic activity corresponding to the 2.7-2.6 Ga events common in the rest of the Slave Province. The oldest rocks in the study area are a succession of granitoid and supracrustal gneisses that have been metamorphosed to amphibolite to granulite facies. From field relationships, the oldest rock is a granodiorite to tonalite orthogneiss, with a zircon crystallization age of 3254+13-6 Ma. A granite gneiss, which may be a small felsic intrusion or an anatectic melt of the tonalite gneiss, yields a zircon age of 3216+14-13 Ma. A K-feldspar megacrystic monzogranite gneiss contains old, discordant, possibly inherited zircons with 207Pb/206Pb ages ranging from 3103 to 3039 Ma, together with coexisting 2879 ± 3 Ma zircon and monazite. These high-grade gneisses are intruded by two megacrystic granite plutons, dated at 2887 ± 2 and 2881+4-3 Ma. The absence of extensive recrystallization and complex structures in these plutons indicates that this igneous event postdated the high-grade metamorphism. An amphibolite-grade synplutonic metamorphic event is dated at ~2880 Ma by new monazite in the older gneiss units. A series of variably deformed mafic to felsic dykes and pegmatites intrude both the granites and gneisses and constrain the end of penetrative deformation in the area. Of these, a boudinaged diorite dyke, with a strong internal foliation parallel to the regional fabric, is dated at 2877 ± 3 Ma. A younger granodiorite dyke that crosscuts the regional fabric at a high angle and has only a weak internal foliation yields an age of 2864+3-9 Ma. An undeformed syenogranite pegmatite, which represents a suite that intrudes all other units in the study area, has a combined zircon-monazite age of 2852 ± 3 Ma. The varying degrees of deformation in these minor intrusive rocks constrains the end of deformation in the study area to ca. 2850 Ma. This contrasts with data from the rest of the Slave Province, where the main phases of deformation, metamorphism, and synmetamorphic plutonism have been dated at ca. 2.62-2.59 Ga. Metamorphic titanite ages from the diorite and granodiorite dykes indicate two lower amphibolite to greenschist facies metamorphic events: one at ca. 2705 Ma and one at ca. 2646 Ma. The youngest Archean magmatic event in the area is represented by granite intrusions at 2594+3-2 Ma, coeval with crystallization of titanite at greenschist-grade conditions in some of the older gneissic and intrusive rocks.
Microvertebrate assemblages from the Upper Silurian of Cornwallis Island, Arctic Canada
Authors: Burrow Carole J , Vergoossen Jo MJ , Turner Susan , Uyeno Tom T , Thorsteinsson Ray
Published: April 2011

Microvertebrate assemblages from four Upper Silurian (?Ludlow-Pridoli) localities on Cornwallis Island, Arctic Canada, comprise mainly scales, plus dentition cones and jaw fragments from ischnacanthid acanthodians, with rare scales assigned to heterostracan Lepidaspis? sp., ?chondrichthyan Arauzia? sp., and Placodermi? gen. et sp. indet. Most of the scales in sample C-11460 are assigned to the poracanthodid acanthodian Poracanthodes canadensis sp.nov., which shows closest affinity to Poracanthodes punctatus Brotzen variants from the Baltic Pridoli. The flank scales of the new species resemble those of P. punctatus s.s. (Silurian variant; the zone fossil for the late Pridoli in the Standard Silurian microvertebrate scheme), with their superposed crown growth zones, rows of small pores aligned with the underlying zones, number of radial canals, and "arcade" canals connecting these radial canals. They differ in having numerous anterior crown riblets, "zig-zag" rather than straight crown pore rows, and V-shaped arcade canals.
Geological evolution of the Manitouwadge greenstone belt and Wawa-Quetico subprovince boundary, Superior Province, Ontario, constrained by U-Pb zircon dates of supracrustal and plutonic rocks
Authors: Zaleski Eva , van Breemen Otto , Peterson Virginia L
Published: April 2011

Fifty million years of Archean evolution is recorded in the Manitouwadge greenstone belt and the Wawa-Quetico boundary region, from ca. 2720 Ma volcanism and subvolcanic plutonism associated with massive sulphide deposits and hydrothermal alteration zones, to 2689-2687 Ma and 2680-2677 Ma synkinematic plutonism. In the greenstone belt, greywackes were deposited after 2693 Ma, post-dating local volcanism by at least 25 Ma, and requiring that the volcanic-sedimentary contact is an unconformity or a fault. In migmatitic greywackes in the Quetico subprovince, detrital zircons limit the depositional age to <2690 Ma, permitting correlation of greywackes across the Wawa-Quetico subprovince boundary. Upward-facing inclined F2 folds that deform the volcanic-sedimentary contact are bracketed by the 2687 ± 2 Ma Loken Lake pluton, which shows strong D2 fabrics, and by 2680+4-3 Ma foliated granite which cuts D2 fabrics. Dextral transpression producing regional F3 folds and the overall east-west trends of the Wawa-Quetico boundary region post-dated the 2680 ± 2 Ma Nama Creek pluton. Field relationships and isotopic ages support correlation of greywackes across the subprovince boundary, and demonstrate that most or all of the ductile deformation post-dated sedimentation. Ductile structures, especially those associated with dextral transpression, are not directly related to juxtaposition of the Wawa and Quetico subprovinces, as these were already contiguous, either through sedimentation on a volcanic substrate or as a result of earlier cryptic structures. Our results imply that the belt-like configuration of the subprovinces, emphasized in accretionary models of the Superior Province, is a relatively late feature that overprints older, tectonically significant structures.
Paleomagnetic and geobarometric study of the Late Cretaceous Mount Lorne stock, southern Yukon Territory
Authors: Harris M J , Symons DTA , Blackburn W H , Hart CJR
Published: April 2011

The ~75 Ma Mount Lorne monzodiorite stock has been studied paleomagnetically to estimate the tectonic motion of the northern Canadian Cordillera since the Late Cretaceous. The stock is one of several paleomagnetic studies currently underway at the University of Windsor Paleomagnetic Laboratory which are funded by the Lithoprobe - Slave northern Cordillera Lithospheric Evolution (SNORCLE) Project. Al-in-hornblende geobarometry and plagioclase-amphibole geothermometry data suggest that the stock has not been tilted since emplacement but does provide evidence that the stock has a normal fault trending north-south through its centre with the east side uplifted relatively by ~1000 m. Paleomagnetic measurements from 12 of 19 granitoid sites yield a well-defined characteristic remanent magnetization direction that is south-southwest and up, and a further six sites yield a direction that is north-northeast and down. Data from a mafic dike yield a negative contact test, suggesting that the dike is coeval with the stock. Combining the 18 granitic site mean characteristic remanent magnetization directions yields a paleopole at 69.1°W, 78.3°N (dp = 4.1°, dm = 4.5°) which suggests that the host Stikine Terrane has been translated poleward by 10.5 ± 3.5° (1170 ± 390 km) and rotated clockwise by 57 ± 11° relative to the North American craton between 75 and 50 Ma. Except for the estimate from the nearby coeval Carmacks Group volcanic rocks, the Mount Lorne estimate is consistent with all other paleomagnetic results within the Stikine Terrane. These latter estimates are also consistent with plate-tectonic models that suggest the Pacific oceanic plates had an increased velocity northwards during the Late Cretaceous.
The 1830 Ma Trans-Hudson hairpin from paleomagnetism of the Wapisu gneiss dome, Kisseynew Domain, Manitoba
Authors: Symons D TA , Harris M J
Published: April 2011

The Wapisu gneiss dome is located in the northeastern part of the Kisseynew Domain of the Trans-Hudson Orogen (THO) in north-central Manitoba. The dome is circular, about 6 km in diameter, with steeply-dipping flanks. It is composed of upper amphibolite-facies gneisses derived from turbiditic sediments, with leucogranitic sill-like intrusions that were metamorphosed, starting at about 1830 Ma. Alternating field and thermal step demagnetization of 153 specimens from 17 sites around the perimeter of the dome isolated a characteristic remanent magnetization (ChRM) direction of D = 346.6°, I = 78.9° (α95 = 5.3°, k = 46, N = 17) that gives a pole of 119.5° W, 75.8° N (dp = 9.5°, dm = 10.0°). Unblocking temperatures and saturation isothermal remanence analyses show that the ChRM resides mostly in single to pseudosingle domain magnetite or titanomagnetite, with minor hematite commonly present and with minor pyrrhotite present in the leucogranites. The ChRM is found to be postfolding with >>99.9% confidence, indicating acquisition on cooling from peak metamorphism at ~1810 ± 10 Ma. This Wapisu gneiss dome paleopole is the first from the Kisseynew Domain and the first from the 1830 to 1770 Ma interval in the THO. It indicates an ~90° bend or hairpin in the apparent polar wander path for the THO juvenile terranes and Superior craton. It is speculated that the hairpin marks the collisional impact of the Archean Sask craton and (or) Hearne craton, which drove the Paleoproterozoic Kisseynew Domain into the Archean Superior craton.
Upper Triassic Takla Group volcanic rocks, Stikine Terrane, north-central British Columbia: geochemistry, petrogenesis, and tectonic implications
Authors: Dostal J , Gale V , Church B N
Published: April 2011

The Upper Triassic Takla Group volcano-sedimentary assemblage is part of the Stikine Terrane of the Intermontane Belt in the Canadian Cordillera and covers an area of more than 30 000 km2 in a belt up to 50 km wide and more than 800 km long. In the McConnell Creek area of north-central British Columbia, the assemblage consists of plagioclase-clinopyroxene-phyric, dominantly basaltic to andesitic flows and pyroclastic rocks, interlayered with volcanogenic sedimentary rocks. Compositionally, the volcanic rocks are intermediate between tholeiitic and calc-alkaline. Their mantle-normalized trace element patterns are characterized by a moderate large-ion lithophile element enrichment and Nb and Ti depletion, suggesting that magmatism occurred in a volcanic-arc setting. Flat, heavy rare earth element chondrite-normalized patterns with (La/Yb)n ratios from 2 to 4.5 suggest that the parent magma was produced by mantle melting in the spinel stability field. The low Sr isotopic ratios (87Sr/86Sri approximately equal to 0.7033-0.7043) and positive εNd values (~ +7) indicate that an older sialic crust was not involved in their genesis. A coeval and compositionally similar volcano-sedimentary assemblage, also of the Takla Group, occurs in the adjacent Quesnel Terrane, in fault contact with the Stikinian Takla Group. Chemical resemblances between the Takla Groups of the Stikine and Quesnel terranes suggest that the volcanic assemblages may have had similar source compositions and melt histories. These results emphasize larger scale similarities between the Stikine and Quesnel terranes and suggest the Upper Triassic volcanic suites represent different fragments of the same early Mesozoic arc system.
Geochronology of Neogene alkaline volcanic rocks (Miles Canyon basalt), southern Yukon Territory, Canada: the relative effectiveness of laser 40Ar/39Ar and K-Ar geochronology
Authors: Hart Craig JR , Villeneuve Mike
Published: April 2011

Miles Canyon basalt is an informal term used to describe numerous exposures of young alkaline olivine basalt flows in southern Yukon. The volcanic rocks are part of the Northern Cordilleran volcanic province. K-Ar and Ar-Ar whole-rock dates indicate that the Miles Canyon succession of flows at the Whitehorse Rapids are clearly Late Miocene in age (ca. 8.4 Ma). The largest exposure of the Miles Canyon basalt occurs at the Alligator Lake volcanic complex where two nearly concordant Pliocene Ar-Ar dates indicate eruption at ca. 3.2 Ma. K-Ar analyses from other sites yield dates of 2.4 and 7.1 Ma and indicate an episodic Neogene volcanic history for the region. There is no evidence of Quaternary or postglacial volcanism. The dates are older than assumed by previous workers, and in some cases the K-Ar dates are strongly discordant from Ar-Ar determinations. More accurate Ar-Ar determinations may result from the method's ability to select smaller amounts of better material for analysis. Excess 40Ar was not encountered. As a result, the accuracy of any single or several discordant K-Ar determinations for Neogene subaerial volcanic rocks, particularly low-K rocks such as basalts, should be questioned and resulting interpretations made with caution. Models accounting for the eruption of the Northern Cordilleran volcanic province lavas have typically relied upon extension along north-trending faults that were generated by stresses along the continental margin. However, we consider a slab window model which better accounts for the initiation and distribution of northern Cordilleran Neogene volcanic activity.
Were Jurassic tholeiitic lavas originally widespread in southeastern Canada?: a test of the broad terrane hypothesis
Authors: Pe-Piper Georgia , Piper David JW
Published: April 2011

Two competing models have been proposed for Early Jurassic magmatism on the eastern North American margin. The "broad terrane" hypothesis argues that tholeiitic lavas were extruded over a large area and later eroded. Alternatively, the lavas were extruded only in the basins in which they now outcrop. We compare the stratigraphy and geochemistry of the tholeiitic lavas and dykes from Atlantic Canada with those of the type section of the Newark basin and use this correlation to test these two models. The earliest high-Ti quartz tholeiites in the type section are represented by lavas in the Fundy basin (North Mountain Basalt), Scotian basin, and eastern Grand Banks and by the Shelburne and Ministers Island dykes. Spatial and temporal geochemical variations in the North Mountain Basalt are mirrored by the Shelburne dyke, strengthening the case that the two were geochemically related. Basalts in Grand Manan Island, on the footwall of the Grand Manan fault that bounds the Fundy basin, are geochemically similar to the lowest North Mountain Basalt flow. These observations suggest that the earliest basalt flows were originally more extensive and have become restricted by later uplift and erosion. However, younger magmas in the Newark basin are represented only by the Caraquet, Anticosti, and Avalon dykes in Atlantic Canada, and corresponding lavas were never deposited in the Fundy basin or eastern Grand Banks. Thus, Jurassic tholeiitic lava distribution lies in between the predictions of the "broad terrane" and the "restricted basin" models.
Crustal models of the eastern Superior Province, Quebec, derived from new gravity data
Authors: Telmat Hamid , Mareschal Jean-Claude , Gariépy Clément , David Jean , Antonuk Caroline N
Published: April 2011

New gravity data were collected in the Nemiscau and La Grande subprovinces of the Superior Province. This ~350 km gravity profile follows the Matagami-Radisson road and extends northward the gravity transect along the ~260 km long Lithoprobe seismic line 48, across the northern Abitibi and Opatica subprovinces. For the Abitibi-Opatica segment, the interpretation is consistent with the Lithoprobe seismic profile. It calls for crustal thickening near the boundary between the Abitibi and Opatica belts, where the Moho is ~5 km deeper than in the Abitibi subprovince and ~8 km deeper than in the northern Opatica subprovince. The gravity model complements the seismic reflection data and provides information on the uppermost supracrustal sequences poorly imaged in the seismic profile. Most of the intrusive rocks in the Opatica Belt appear as thin (<5 km) bodies. Across the Nemiscau and La Grande subprovinces, the Bouguer anomalies are of short wavelengths and their sources lie in the upper crust. The crustal thickness is constant from the northern Opatica Belt throughout the southern part of the Nemiscau subprovince. Density measurements indicate that the upper crustal density is higher in the Nemiscau and La Grande subprovinces than in the Abitibi and Opatica belts. There is some crustal thickening beneath the La Grande subprovince, and a gravity high at the northern end of the subprovince is related to the occurrence of mafic supracrustal sequences. The gravity anomaly signature associated with the lateral density variation and field evidence indicate that the main tectonic boundaries dip to the north.
New data from Halifax Harbour: paleoenvironment and a new Holocene sea-level curve for the inner Scotian Shelf
Authors: Edgecombe Roger B , Scott David B , Fader Gordon BJ
Published: April 2011

Two vibracores collected from Halifax Harbour allow reevaluation of the early postglacial history and part of a new sea-level curve for eastern Nova Scotia. An acoustically distinct seismic unit found throughout Halifax Harbour, but never previously sampled, occurs in the base of one core. Analysis of foraminiferal assemblages within this unit suggests estuarine conditions, not lacustrine as previously suggested. An in situ peat sample from the second core yields a date of 7770 ± 260 BP, and, based on the marsh foraminifera present, provides a sea-level point at -26.1 m. The foraminifera from the estuarine deposit yielded a date of 8480 ± 60 BP. The estuarine sediments are reddish, have a low organic content, and are very different from present-day estuarine sediments in this area, providing us a rare glimpse at early postglacial estuarine environments. This estuarine deposit represents deeper water than does the peat and indicates that sea level was higher prior to 7770 BP. Earlier papers suggested that sea level had been higher before 7000 BP, but the points presented here are the first data from this interval providing both spatial and temporal control on this critical interval of sea-level history. The new sea-level curve presented in this study, together with another recently published curve, shows two periods of emergence, one prior to 11 000 BP and another between 8000 and 7000 BP. The earlier emergence was probably the initial elastic rebound following ice removal; the second one may be the passage of the glacial forebulge predicted by theoretical models.
A seismic-based cross-section of the Grenville Orogen in southern Ontario and western Quebec
Authors: White D J , Forsyth D A , Asudeh I , Carr S D , Wu H , Easton R M , Mereu R F
Published: April 2011

A schematic crustal cross-section is presented for the southwestern Grenville Province based on reprocessed Lithoprobe near-vertical incidence seismic reflection data and compiled seismic refraction - wide-angle velocity models interpreted with geological constraints. The schematic crustal architecture of the southwest Grenville Province from southeast to northwest comprises allochthonous crustal elements (Frontenac-Adirondack Belt and Composite Arc Belt) that were assembled prior to ca. 1160 Ma, and then deformed and transported northwest over reworked rocks of pre-Grenvillian Laurentia and the Laurentian margin primarily between 1120 and 980 Ma. Reworked pre-Grenvillian Laurentia and Laurentian margin rocks are interpreted to extend at least 350 km southeast of the Grenville Front beneath all of the Composite Arc Belt. Three major structural boundary zones (the Grenville Front and adjacent Grenville Front Tectonic Zone, the Central Metasedimentary Belt boundary thrust zone, and the Elzevir-Frontenac boundary zone) have been identified across the region of the cross-section based on their prominent geophysical signatures comprising broad zones of southeast-dipping reflections and shallowing of mid-crustal velocity contours by 12-15 km. The structural boundary zones accommodated southeast over northwest crustal stacking at successively earlier times during orogeny (ca. 1010-980 Ma, 1080-1060 Ma, and 1170-1160 Ma, respectively). These shear zones root within an interpreted gently southeast-dipping regional décollement at a depth of 25-30 km corresponding to the top of a high-velocity lower crustal layer.
Insolitignum n.gen. and Palaeoephippium Goodbody 1986 (Radiolaria) from the Lower Silurian of the Cape Phillips Formation, Arctic Canada
Authors: MacDonald Eugene W
Published: April 2011

Radiolaria of the family Palaeoscenidiidae were recovered from two bedded-limestone and two limestone-concretion samples from the upper Llandovery of the Cape Phillips Formation, Cornwallis Island, Arctic Canada. The new genus Insolitignum is defined by two apical rays, three basal rays, and a principal ray in an intermediate position. The principal ray distinguishes this genus from Palaeoephippium. Insolitignum dissimile, the type species of the new genus, was previously placed in Palaeoephippium. New species described here are Insolitignum peranima, Insolitignum vivanima, and Palaeoephippium adraini.
Amia cf. pattersoni from the Paleocene Paskapoo Formation of Alberta
Authors: Grande Lance , Guo-Qing Li , Wilson Mark VH
Published: April 2011

A well-prepared anterior half of an amiid skull from the Late Paleocene Paskapoo Formation of south-central Alberta is described. The specimen is either very closely related to, or conspecific with, Amia pattersoni Grande and Bemis, 1998, from the Early Eocene Green River Formation of Wyoming. We leave the specimen as Amia cf. pattersoni until additional material is found to further clarify its relationships. Amia cf. pattersoni is the oldest known specimen clearly identifiable as belonging to the genus Amia (sensu Grande and Bemis, 1998), and the Paskapoo species extends the known geographic range of Amia both northward and westward. The fish assemblage of the Paskapoo Formation represents the most diverse freshwater Paleocene fish fauna known from North America. Based on comparisons of sample size and relative taxonomic diversity to the better known Green River Formation localities of Wyoming, we predict that further collecting will substantially increase the known diversity of the Paskapoo fauna. The Paskapoo Formation, therefore, has great potential to continue adding to the meager knowledge of pre-Eocene freshwater teleost diversity in North America.
Geoelectric response and crustal electrical-conductivity structure of the Flin Flon Belt, Trans-Hudson Orogen, Canada
Authors: Ferguson I J , Jones Alan G , Sheng Yu , Wu X , Shiozaki I
Published: April 2011

A Lithoprobe magnetotelluric survey across the Palaeoproterozoic Trans-Hudson Orogen included 34 sites within the Flin Flon Belt and adjacent geological domains. The magnetotelluric impedance tensors and geomagnetic induction vectors reveal four distinct geoelectric zones along this segment of the Lithoprobe transect. In the east and west, the geoelectric responses are dominated by the contrast between intrusive rocks and more conductive ocean-floor assemblages. A significant characteristic of the responses throughout the Flin Flon Belt is the very strong galvanic distortion of the electric field, which reflects the complexity of the upper crustal geological structure in the greenstone belt, requiring careful application of distortion removal methods. The responses at sites near the north of the Flin Flon Belt are related to the boundary with the southern flank of the Kisseynew gneiss belt. To the south, at sites near Athapapuskow Lake, the responses are dominated by a strong upper-crustal conductor. The magnetotelluric observations show that the Athapapuskow Lake conductivity anomaly extends for at least 40 km along strike (~N36°E), and is roughly two-dimensional in form. Numerical modelling shows that the top of the body dips southeast at 20-50° from a western edge coincident with the Athapapuskow Lake shear zone. The conductor lies in the eastern part of the Namew gneiss complex. The magnetotelluric method cannot resolve the exact spatial distribution of conductive rocks but it is probable that the anomaly is caused by a series of isolated conductors (with resistivity <1 Ω·m) associated with subordinate graphitic and sulphidic supracrustal gneisses.
Meiotic behavior in progeny of tissue culture regenerated oat plants (Avena sativa L.) carrying near-telocentric chromosomes
Authors: Johnson S. S. , Phillips R. L. , Rines H. W.
Published: April 2011

Meiotic behavior was analyzed in 69 progeny of two regenerated oat plants (Avena sativa L.) containing different heteromorphic pairs of chromosomes to evaluate the behavior of the altered chromosomes in succeeding generations after regeneration from tissue culture. Heteromorphic bivalents separated prematurely and lagged during anaphase I in about 9% of the cells. Univalents often divided equationally during the first division, were usually not included in the telophase nuclei during the second meiotic division, and ultimately resulted in micronuclei at the quartet stage. Heteromorphic pairs were found in some progeny plants that behaved either more stably or less stably than the progenitor heteromorphic pairs. These variants may have been due to changes in the deficient chromosomes, which possibly arose from bridges during the previous meiosis. Higher than normal frequencies of bridges were seen at anaphase I in microsporocytes of plants containing heteromorphic pairs. Meiotic behavior of heteromorphic pairs involving a SAT chromosome was compared with that of the respective monosome that had been recovered in progeny of a plant carrying the heteromorphic pair. Quartet micronuclei frequencies indicated that chromosomes from the heteromorphic bivalent were included in microspores at a much higher rate than was the respective monosome.

Key words: meiotic behavior, heteromorphic chromosome pair, oats, tissue culture, telocentric chromosomes, variation.
Meiotic behavior of a tiny fragment chromosome that carries a transposed centromere
Authors: Maguire Majorie P.
Published: April 2011

A supernumerary, tiny chromosome with a transposed centromere, in an apparently normal maize background, was observed through meiotic stages from pachytene through anaphase II. Departures from normal meiotic chromosome behavior were noted for this tiny chromosome. These included failure of the usual degree of condensation at pachytene, failure of synapsis, and most strikingly the ability of sister centromeres to interact with the spindle on schedule with the normal dyads at anaphase I, so that monads were commonly distributed to the poles for telophase I and then often lagged at anaphase II. Possible significance of the unusual behavior is discussed.

Key words: meiosis, fragment, centromere.
The effects of heterozygous inversions on crossing-over in Drosophila ananassae
Authors: Singh B. N. , Singh A. K.
Published: April 2011

Crossing-over was studied in females of Drosophila ananassae under different karyotypic combinations to detect the effects of heterozygous inversions by utilizing three recessive markers of the second chromosome. Because of the presence of a subterminal inversion (2L) in the heterozygous condition, crossing-over between the cu and b genes is completely eliminated. However, 2L heterozygosity enhances the level of recombination between the b and se genes. Furthermore, two third chromosome inversions when heterozygous also exert an enhancing effect on crossing-over in the second chromosome. These results provide evidence for the existence of intra- and inter-chromosomal effects of inversions on crossing-over in D. ananassae.

Key words: Drosophila ananassae, crossing-over, inversions, intrachromosomal effects, interchromosomal effects.
Transcription analysis of alcohol dehydrogenase null alleles from natural populations of Drosophila melanogaster
Authors: Freeth Allan L. , Gibson John B. , Wilks Ann V.
Published: April 2011

Southern analysis of 19 Adh null activity alleles isolated from Tasmanian populations of Drosophila melanogaster have shown that there are no detectable insertions or deletions in an 11.8-kb region that contains the gene. Northern blot analyses of the null alleles have shown that they all produce a transcript about 100 bases longer than that produced by the normal allele and they accumulate a precursor of 1800 bases. The amount of the major transcript produced by the null alleles is about 10% of that produced by normal alleles. The molecular properties of the null alleles suggest that they share a common origin.Key words: alcoahol dehydrogenase, null alleles, mRNA, Drosophila melanogaster.
Meiotic analyses of tall fescue somaclones
Authors: Eizenga G. C.
Published: April 2011

Genetic studies of open-pollinated, hexaploid tall fescue (Festuca arundinacea Schreb., 2n = 6x = 42) would be enhanced by having aneuploids in a homogeneous background. Regeneration of plants from tissue culture was one possible method of obtaining aneuploids. 'Kenwell' tall fescue was developed from S2 and S3 clones and thus should be more homogeneous than many tall fescue varieties. The somaclones were derived from calli of in vitro cultured mature embryos. Meiotic analyses of 15 parental clones showed mostly ring bivalent pairing and 76.2–98.2% pollen stainability. Of the 166 somaclones analyzed meiotically, there were 99 euploids, 59 aneuploids (2n = 38, 39, 40, and 41), and 8 of higher ploidy (2n = 56, 70, 78, and 80). The somaclones were grouped according to chromosome number (ranging from 38 to 42), meiotic behavior (0–2 vs. 3 or more multivalents), and pollen stainability (more or less than 20%). Also observed were anaphase bridges, heteromorphic bivalents, and centric fragments. The meiotic changes were best explained by the hypothesis that there was perturbation in the replication of heterochromatic regions during tissue culture. Breakage and possible rejoining most likely involved chromosome arms with heterochromatic regions, which resulted in translocations, deficiencies, deletions, and telosomes.Key words: Festuca arundinacea, aneuploids, tissue culture, somaclonal variation.
Mitotic blocking agents for suspension cultures of maize 'Black Mexican Sweet' cell lines
Authors: Stadler J. , Phillips R. , Leonard M.
Published: April 2011

Good metaphase arrest (25% mitotic index) in maize (Zea mays L.) 'Black Mexican Sweet' suspension cultures can be obtained with colchicine treatment alone, but only if very high concentrations (0.5%; 12.5 mM) are used. This colchicine concentration is 5- to 10-fold greater than that required for optimum mitotic arrest in cell cultures of other plant species. In contrast, we report that the herbicide amiprophos methyl (APM) is a much more efficient metaphase inhibitor for 'Black Mexican Sweet' suspension cultures than colchicine. Low concentrations (50 μm) of APM applied for 21–28 h produce a similar 25% mitotic index, and the growth-inhibiting effects of this treatment are undetectable 24 h after the removal of APM from the culture medium, APM, therefore, may be a useful agent for mitotic arrest in experiments which require survival of the treated cells. Another antitubulin herbicide, trifuralin, also was tested for ability to promote metaphase arrest in 'Black Mexican Sweet' cultures, but it proved to be ineffective.Key words: mitotic arrest, colchicine, phosphoric amide herbicide.
Effect of freeze-thaw cycles on the bond durability between fibre reinforced polymer plate reinforcement and concrete
Authors: Green Mark F , Bisby Luke A , Beaudoin Yves , Labossière Pierre
Published: April 2011

Deterioration of infrastructure is one of the most pressing concerns facing today's civil engineering community. As a result, new rehabilitation techniques, such as the external bonding of fibre reinforced polymer (FRP) plates and sheets, are being developed. To apply these rehabilitation methods in Canada, the durability of the rehabilitated structures in cold regions must be assessed. This paper examines the effects of freeze-thaw cycling on the bond between FRP and concrete. An experimental investigation was conducted using both single lap pull-off and bond beam specimens. Only uniaxial carbon FRP strips were considered. The specimens were exposed to up to 300 freeze-thaw cycles consisting of 16 h of freezing and 8 h of thawing in a water bath. After exposure, the specimens were tested to failure. The development of strain along the bond length and the failure mode are presented for both types of specimens. Load deflection curves are presented for the beam specimens. The results indicate that the bond between carbon FRP strips and concrete is not significantly damaged by up to 300 freeze-thaw cycles.Key words: reinforced concrete, repair, rehabilitation, strengthening, fibre reinforced polymers, freeze-thaw, bond damage.
Dowel bars corrosion in concrete pavement
Authors: Abo-Qudais Saad A , Al-Qadi Imad L
Published: April 2011

To study the effectiveness of sealants in reducing chlorides and water intrusion into pavement joint openings, nine 122 × 91 × 20 cm concrete slabs were fabricated. One slab was cast without a joint and was used as a control, two were cast with non-sealed joints, and the other six were cast with joints that were sealed, after the slabs were cured, with either type A (low modulus silicone) or type B (polyurethane) sealant, which are one-component rigid pavement joint sealants. Three dowel bars, used for load transfer, were installed below the joint at the mid-thickness of each slab. Two types of dowels were used: epoxy-coated and uncoated. A joint and crack beneath it were formed at the middle of the slab to simulate field conditions. To accelerate dowel bar corrosion and to examine pavement joint sealant effectiveness in abating chloride intrusion, the slabs were exposed to alternate ponding cycles of 6% sodium chloride solution (3 days of ponding and 4 days of drying). The corrosion progress was monitored by measuring corrosion current density using a three-electrode linear polarization device. Also, chloride contamination was measured by collecting powdered concrete samples from each slab at four different depths to determine the chloride concentration profile. The corrosion current density and chloride contents over a period of 18 months were analyzed. The results show that the unjointed slab has a higher resistance to chloride penetration, followed by jointed slabs sealed with type A sealant, then jointed slabs sealed with type B sealant. In addition, the performance of epoxy-coated dowel bars in abating corrosion was better than that of uncoated dowels.Key words: sealant, rigid pavement, concrete, chloride intrusion, corrosion, dowels.
D-CRANE: a database system for utilization of cranes
Authors: Al-Hussein Mohamed , Alkass Sabah , Moselhi Osama
Published: April 2011

Crane selection is a time consuming process that involves extensive data manipulation. Several systems have been developed to assist in selecting cranes and in planning their lifts. These systems lack the support of a comprehensive database to provide information about crane configurations, their lift capacity settings, and rigging equipment. Although crane manufacturers provide data for their cranes, these data are not always consistent and do not follow a standard format. This creates frequent problems for crane users, especially when interpolating the load charts. This requires the users to make decisions based on job conditions and categories of cranes, which can lead to costly mistakes. This paper describes the development of a comprehensive database (called D-CRANE) designed to support efficient selection of cranes. D-CRANE has been developed in collaboration with an industrial partner. It includes operational information about crane geometry, lift configurations, lift capacity settings, accessories, and attachments. D-CRANE has a number of interesting features: (i) powerful graphics capabilities, featuring a multimedia environment and a practical user-friendly interface; (ii) capacity to accommodate different types of commercially available cranes; (iii) powerful storage, sorting, and query routines; (iv) flexibility in using metric and empirical units; (v) capability of operating in a network environment, and (vi) minimum disk storage space. D-CRANE is a relational database designed using entity relation diagram and is implemented using MS-Access database management system. A case example is presented to demonstrate the use and capabilities of D-CRANE.Key words: database management system, crane selection, planning critical and heavy lift.
Étude de la pénétrabilité du coulis de ciment microfin sous pression dans les structures de maçonnerie dégradées à caractère historique : effet d'un agent colloïdal
Authors: Palardy Danielle , Perret Stéphanie , Ballivy Gérard , Laporte Robert
Published: April 2011

Several masonry structures, built over the past centuries, have to be restored to ensure their structural integrity and their conservation. Important research and development projects have been initiated by Public Works and Government Services Canada to rehabilitate some of these structures, such as the Rideau canal locks, by using a cement-based grouting technique. By following grouting pressures and flow rates, the stability of the structure is protected and the efficiency to fill openings is assured by using microfine cement-based grouts with admixtures. However, cement grout penetration cannot be observed with precision during the injection. The project described in this paper presents the grouting treatment of a Rideau canal lock sill wall that had to be demolished and reconstructed. The penetration of two different grout mixes was observed by removing the front row of blocks, piece by piece. A second phase of this study was conducted in the laboratory to compare the penetration of different grouts in a reconstructed granular material which simulated the lock's interior walls.Key words: restoration, masonry, grouting, groutability, cement grout, colloidal agent.
Design and evaluation of a wedge-type anchor for fibre reinforced polymer tendons
Authors: Campbell T I , Shrive N G , Soudki K A , Al-Mayah A , Keatley J P , Reda M M
Published: April 2011

The development of a wedge-type anchorage system for fibre reinforced polymer (FRP) tendons, as part of an overall corrosion-free post-tensioning system, is outlined in this paper. A stainless steel anchor is described, and results from numerical models and load tests to evaluate its behaviour under loads from anchor set, as well as static and repeated tendon tension, are presented. An alternative wedge-type anchorage system made from ultra-high performance concrete is also described. It is shown that, although significant progress has been made in development of the anchorage, further work is required to make it more robust.Key words: FRP tendons, post-tensioning, anchorage, corrosion-free, mathematical models, load tests, concrete.
A fuzzy expert system for design performance prediction and evaluation
Authors: Fayek Aminah Robinson , Sun Zhuo
Published: April 2011

This paper describes a fuzzy expert system for design project performance evaluation and prediction. It presents a comprehensive framework of factors that impact design performance and factors used to measure performance. A new approach to generating membership functions based on objective data is presented. This approach provides for membership functions that are widely applicable in a given context and can be calibrated to suit different contexts. A method of generating expert rules to relate factors impacting design performance is presented. A survey was conducted to collect data to develop and test the proposed methods. These methods were used in developing the fuzzy expert system. Based on validation of the system, the fuzzy expert system provides accurate linguistic predictions of design performance parameters. The methods presented in this paper are useful and realistic in modeling design performance and in capturing the inherent subjectivity involved.Key words: construction, design, evaluation, expert systems, fuzzy logic, performance, prediction, productivity.
Analysis of time-dependent effects in concrete structures using conventional linear computer programs
Authors: Elbadry Mamdouh M , Ghali Amin
Published: April 2011

Analysis of the time-dependent changes in displacements, internal forces, and reactions at the supports in continuous reinforced concrete structures cast, prestressed, and loaded at different stages is frequently needed in design to satisfy the serviceability requirements. The time-dependent parameters considered in the analysis are creep and shrinkage of concrete, relaxation of prestressed steel, sequence of construction, and changes in structural system and support conditions. A procedure of analysis is presented using conventional linear analysis computer programs. The analysis procedure is explained through examples to demonstrate its simplicity and applicability.Key words: analysis, computer program, creep, displacement, frames, precast concrete, prestressed concrete, relaxation, shrinkage, time-dependent.
Automated vehicle monitoring and audit system for administering partnership haul agreements
Authors: Berthelot Curtis , Lang Angela , Burns Norm , Taylor Brian , Hanson Randy
Published: April 2011

Saskatchewan Department of Highways and Transportation has been a leader in road and short-rail transportation initiatives that facilitate efficient commercial transportation to remote northern and rural areas. A recent initiative undertaken by Saskatchewan Department of Highways and Transportation is a public-private partnership with commercial carriers to allow larger truck configurations to haul primary weights on select secondary rural roads if the carrier deploys road friendly vehicle technologies, such as air-spring suspension and central tire inflation. The pilot partnership haul program has resulted in haul cost savings of between 20% and 50%, generating approximately four million dollars per year in total, which is subsequently shared between the carrier and Saskatchewan Department of Highways and Transportation. At the present time, equitable distribution of partnership haul cost savings and compliance audits are determined manually based on submitted logbooks and waybills. Because this manual system is labor intensive and prone to accounting errors, the administration of the partnership haul program is only tenable for larger carriers with semi-automated administration systems. As a result, a system that automatically allocates partnership haul cost savings and performs compliance audits is the enabling technology to expand the partnership program to small and mid-size carriers. International Road Dynamics Inc. proposed and developed an automated vehicle monitoring and audit system that is designed to facilitate the Saskatchewan partnership program. This paper discusses the Saskatchewan partnership program and describes the technological features and advantages of the automated vehicle monitoring and audit system. This paper also discusses other potential applications of the automated vehicle monitoring and audit system.Key words: commercial vehicle operations, automated vehicle monitoring system, central tire inflation, geographic information systems, global positioning systems, transportation sustainability, road preservation, intelligent transportation systems, rural road management.
Les prévisions des brèches de rupture des barrages en terre restent difficiles
Authors: Zerrouk N E , Marche C
Published: April 2011

The validity of dam failure studies is based on the appropriateness of the expected failure mode. Failures of earth-fill structures show the importance of the choice of breach parameters for failure evaluation and consequences. This paper summarizes the state of the possibilities for forecasting the breach and the resulting hydrograph in the downstream valley. It describes the most current methods, applies them on a failure case observed in the Saguenay region, Province of Québec, and compares the results. Considering the large uncertainty margin on the results, the paper allows one to understand why breach forecasting must not, in the current state of knowledge, be part of the safety study process, and that it is preferable to stay with a definition for breach based on a rule intelligently applied with respect to the case, the structure, and its composition.Key words: dam failure, dam breach, erosion, forecasting, flood of failure, earth-fill dam.[Journal translation]
Bolted woodsteel and woodsteelwood connections: verification of a new design approach
Authors: Mohammad M , Quenneville J HP
Published: April 2011

This paper covers the verification tests carried out at the Royal Military College of Canada on woodsteelwood and woodsteel bolted connections. Thirty groups of specimens were tested. Specimen configurations were selected in such a way to include fundamental brittle and ductile failure mode cases. Comparisons between experimental results and predictions from proposed equations developed from steelwoodsteel bolted connections are given. Proposed design equations were found to provide better predictions of the ultimate loads than current CSA Standard O86.1 design procedures especially for bearing. However, row shear-out predictions seem to overestimate the strength. An adjustment using the reduced (effective) thickness concept is therefore proposed. Experimental observations on specimens that failed in row shear-out indicated that shear failure occurred over a reduced thickness. Stress analysis confirms findings on the reduced thickness. The research program is described in this paper along with the results and the proposed design equations for woodsteelwood and woodsteel bolted connections loaded parallel-to-grain.Key words: woodsteelwood, woodsteel, bolt, connection, strength, failure, design, thickness.