Abstracts of Student Theses
Lower Palaeozoic rocks of the Meguma terrane were extensively deformed and metamorphosed
during the Devonian Acadian orogeny, which resulted from oblique collision with the
Neoproterozoic Avalon terrane. In the Yarmouth area of southwest Nova Scotia, the
Cambrian-Ordovician Goldenville and Halifax (HF) Formations are overlain by the Silurian White
Rock Formation (WRF), which forms the core of an axially-stretched, SW-plunging Acadian (D1)
syncline. Acadian structures are well-preserved in the core of the syncline, which is
dominated by mafic volcanogenic rocks. On the steep limbs, D1 structures in dominantly
metasedimentary outer parts of the WRF and underlying HF are overprinted in broad shear zones,
previously recognised as manifestations of the Carboniferous Alleghanian orogeny (D2).
D2 shear zones are wide (3-5 km), strike-parallel regions of pervasive, greenschist-facies,
polyphase ductile strain, with foliation (S2) sub-parallel to their boundaries. The Cranberry
Point Shear Zone (CPSZ), on the SE-dipping, NW limb of the Yarmouth syncline is
characterised by pitching lineations and flattening strain, compatible with triclinic
transpression. Kinematic indicators are largely absent from central regions of the CPSZ, but
indicate a component of (shear zone) centre-side-up on each of its margins. The Chebogue
Point Shear Zone, on the opposite limb of the syncline, is similar to the CPSZ in many
respects, but is poorly exposed. A component of NW-side-up is indicated on its SE margin.
Although D2 deformation was concentrated on steep limbs, pelitic rocks in the core of the
syncline were also affected.
Metamorphic grade ranges from biotite zone in the Goldenville Formation and central
parts of the WRF to staurolite-andalusite zone within each of the D2 shear zones. P-T
estimates obtained using conventional and multi-equilibrium thermobarometric techniques,
together with constraints from petrogenetic grids, suggest peak M1 conditions of
550-600 °C and approximately 4 kb in outer parts of the WRF and HF. Peak metamorphism
was contemporaneous with the latter stages of D1 deformation, ca. 380 Ma. M2
retrograde metamorphism accompanied D2 deformation at a temperature of approximately
400 °C. Ubiquitous ca. 325 Ma laserprobe and step-heating
40Ar/39Ar muscovite ages record syn/post-M2 cooling. Older ages
obtained from the central parts of pegmatitic muscovite record fractional
40Ar loss and place
a minimum age of 360 Ma on post-M1 cooling below approximately 350 ºC.
The presence of higher-grade rocks within Alleghanian shear zones is interpreted to reflect
differential exhumation of M1 assemblages, possibly as a result of variable flattening during D2
(325 Ma) transpression. This suggestion is supported by kinematic indicators on shear zone margins.
Supervisor: Rebecca Jamiesom
Marine carbonate mud mounds occur 5km northwest of Bay St. Lawrence, Cape Breton Island,
on a 160 210m ridge before the upper margin of the Laurentian Channel. The marine carbonate mounds
occur subsurface of the Holocene siliciclastic sediments and are thought to be a recent formation.
Samples from these < 1m high mounds are of three textural varieties: (1) knobby popcorn clustered,
(2) muddy, (3) and erosional. All varieties are highly porous with numerous small pore holes
(< 3mm). Internally, the mounds are a low Mg muddy micrite with no lamination. Concentrically banded
acicular and radial sparite occurs in pore spaces. They have comparable characteristics with many
cold water and marine carbonate formations, but the absence of an abundant biological component and
the uncommon internal structure make these marine carbonate mounds unique. Formation of the marine
carbonate mounds may originate from hydrocarbon fluid seepage, seawater geochemistry at the sediment
interface, the circulation of various pore waters, or the biological activity of various marine biotas.
Supervisor: Petter Wallace
Fluid inclusions in garnet have recently been discovered in migmatitic paragneisses in the polycyclic
Algonquin domain (McClintock subdomain), Central Gneiss Belt, Grenville Province, Ontario. The host
rocks are metapelitic migmatitic garnet bearing gneisses; the fluid inclusions occur in garnet. Two
kinds of fluid inclusions are recognized: GSI a, monophase negative crystal shaped inclusions of
pure or near pure CO2; and GSI b, two phase (liquid vapour), aqueous carbonic inclusions. Inclusions
may represent end members of an evolving fluid. GSI a inclusions have densities ranging ca. 0.9
1.05 g/cm3. Isochores plotted from GSI a inclusions give P T estimates of approximately 6 kbars
at 700oC. An independent P T estimates from local metapelites gives 726oC and 7.6 kbars. Monazite
age constraints on garnet growth limit the age of the inclusions to sometime after ca. 1474 Ma. The
fluid inclusions represent the evolution of fluid in the Algonquin domain trapped at various stages
during high-T decompression, ca. 1080 Ma. Other evidence of low aH2O Grenvillian fluids in the region
can be found in the migmatites and granulites of the Muskoka domain.
Polygonal features of diameter 20B200 m, recently identified at mid high latitudes of Mars in high resolution (1.5 13 m/pixel) digital images, are visually similar to ice wedge patterns that form by seasonal cooling of ice rich permafrost in Earth's arctic regions. Other hypotheses for Mars networks include desiccation, structural bending, or deep climatic cooling. Here I investigate hypotheses by applying quantitative comparisons of Mars= networks from Utopia Planitia (43.5 N, 269.3 W) with terrestrial ice wedge patterns located at the mouth of the Sagavanirktok River, near Prudhoe Bay, Alaska (701N,1471W), as well as with experimental desiccation fracture patterns. Statistical metrics include intersection types, polygon size, relative orientation between neighbouring fracture segments, and degree of orderliness. I find that Utopia Planitia networks a) are qualitatively similar to terrestrial ice wedge networks with respect to intersection types and degree of orderliness, but have larger spacing; b) are distinctively different from fracture patterns that form by a single fracture event, such as desiccation patterns in mud; and c) display strong north northeast orientation over large regions, approximately parallel to the regional topographic slope into the Utopia basin. I conclude that Mars networks formed by recent and multiple fracture events, likely caused by seasonal cooling similar to terrestrial permafrost patterns, and not by other proposed mechanisms.
Circular to elliptical depressions connected by troughs, visible in Mars Orbiter
Camera images, occur in association with small scale polygons in Utopia
Planitia. Possible terrestrial analogues Bchains of depressions that
occur in high latitude lowlandsB are the result of thaw derived subsidence
over ice wedges, especially at wedge intersections, linked by straight
or angular water courses that follow ice wedge troughs. The similar
plan view shape and apparent connectivity between depressions support
the hypothesis that Utopia patterns also may form by interactions between
patterned ground, ice rich sediment and flowing surface water. Alternatively,
depressions might form by localized subsidence from sublimation of water
or CO2 ice that initiates randomly or randomly along troughs.
To investigate hypotheses for the origin and patterning of depressions,
I compare their distribution in Utopia to remote sensing data on topography,
thermal inertia and hydrogen content of the shallow subsurface. In addition,
the spacing and connectivity along troughs of 24 Mars patterns, each
characterized by hundreds to thousands of individual depressions, are
tested against three synthetic patterns in which depressions were distributed
randomly and randomly along troughs. Mars depressions have diameter
4 100 m and broadly variably separation distances of 5 300 m, compared
to ranges of 1 50 m and 5 50 m for beaded depression patterns in northern
Alaska. Principally occurring along the SW margin of Utopia (280oW
40oN, 280oW 55oN, 260oW
40oN and 260oW 55oN) on surfaces of
Hesperian age, Mars patterns occur in regolith classified as fine grained
loose material with dispersed rocks and/or bedrock outcrops. Water ice
content of the upper metre of regolith is low, < 5% by weight. In comparison,
fine grained perennially frozen soils in terrestrial settings typically
contain 30 70% water ice, but this may be topped by a drier seasonally
frozen layer. Mars features principally occur on shallow slopes, < 1deg,
with broad SE exposure. The crisp morphology of meter scale depressions
suggests recent or ongoing formation. Comparisons with synthetic terrains
indicate that depressions are not uniformly distributed across polygonal
patterns, but instead preferentially occur along down sloping troughs,
consistent with a surface flow or subterranean pipeflow connection between
Ungulates in the wild are normally free from periodontal disease. Yet, Cape Breton Highland (CBH) moose (Alces alces andersoni) of Nova Scotia have displayed an increased incidence of incisoform macro and micro fractures, which may have an effect on moose longevity. This condition appears to be rare, as it has only been formally documented in Alaskan (1990) moose (Alces alces gigas) and in Manitoban moose (Alces alces andersoni), and remains unexplained.
We have selected suites of broken and healthy teeth from the CBH and compared them with moose teeth from Shelburne County, NS, where no incidence of broken incisorform teeth has been documented. Fracture patterns in teeth, and especially tooth enamel (hydroxyapatite) were studied under the petrographic microscope and the electron microprobe. Enamel was carefully isolated from 25 representative samples of teeth from both the CBH and the control area and analyzed chemically by Inductively Coupled Plasma Mass Spectrometry (ICP MS).
Samples from the problematic CBH area are significantly depleted in Barium, Lead, Strontium, Cobalt and Tin in comparison with those of the control area, and some of these deficiencies have been associated with dental disease in animals elsewhere. Samples from the CBH were divided arbitrarily into two groups: A) those collected north of the CBH National Park, and B) those collected south of the Park. In each case, they were separated with respect of their perceived low, medium and high degree of fracturing.
Correlation trends based on Breakage score and elemental concentration Within the CBH the results are not always consistent. A) North of the Park increased degree of fracturing correlates positively with contents of Cd, Mn, Nb, Rb, Sr, Y, Sn and Bi, and negatively with Al, Cu, Ti, Zn, Mg, As, Th and U. B) South of the Park increased degree of fracturing correlates positively with Ba, Mn, Sr, Mg, Se, As, Y, Th and U, and negatively with Al, Cr, Cu, Ga and Sn. Undoubtedly the number of samples is so far insufficient to draw useful conclusions, yet these are the first data available for moose teeth in the region, and raise interesting questions.
Based on results for tin, where higher concentrations are found within the control group, and the geology of the control area characterized by natural concentrations of tin, it is possible to determine the origin (where a moose lived) based on tooth geochemistry.
The physical disturbance of the sulphide bearing rocks of the Meguma Group can lead to oxidation of the sulphides and possibly generate Acid Rock Drainage (ARD). ARD is a well known, and costly problem associated with the Meguma Group in the Halifax region of Nova Scotia, Canada. Finding the ideal site for waste rock disposal is not always easy, and it has been proposed that dumping waste acid generating materials into salt water of the Bedford Basin is a possible solution. This study focuses on the survival and geomicrobiological interactions of Acidithiobacillus ferrooxidans, and the behaviour of the Halifax slates and the Goldenville Halifax transition zone (GHT) in fresh and saline waters.
This study examines pH changes in both rock types in fresh and salt water static tests. Rocks from both the GHT and Halifax slate were crushed into several size fractions for the pH experiments, and one size fraction for the control and cycling experiments. Data collected over a period of 5 weeks indicate that for all size fractions, and for both the fresh and salt water samples, an initial dramatic drop of pH is followed by an apparent levelling off in pH, producing an exponential curve of pH versus time (days). This trend is evident for the Halifax slate with an initial average fresh water pH of 5.6 (range 5.3 6.1), and an average final pH of 3.2 (range 3.1 3.5). The salt water samples of Halifax slate had an average initial pH of 6.71 (range 6.3 B 7.0), and an average final pH of 4.03 (range 3.6 5.5). The trend of the GHT data is similar; however the salt water pH drop is not as dramatic as the drop in pH of the fresh water. The average initial pH of GHT fresh water samples is 7.1 (range 6.9 B 7.4), and an average final pH of 4.7 (range 3.8 B 5.5). The GHT salt water average initial pH is 7.23 (range 7.1 B 7.4), and the average final pH is 6.31 (range 5.4 7.0). The addition of bacteria to samples of both rock types in fresh and salt water did not effect the final pH. The cycling of fresh water resulted in a similar trend in pH: the pH decrease was approximately the same amount at the end of each day before the fresh water change. Microprobe analysis confirms the dominance of pyrrhotite in the GHT and Halifax slates in the Beaverbank area. Acid prediction tests confirm the ability of the rocks to produce ARD. The SEM studies examined un inoculated and inoculated samples of both rock types in salt water to observe possible attachment to the rock surface. SEM confirmed bacterial survival and attachment to the rock surface of both rock types in salt water.
Implications from this study show that although the pH change is somewhat small in salt water, the drop is not insignificant, and indicates the continuing oxidization of sulphide minerals. Care should be taken when disposing of waste acid rock in any aquatic environments. Concentration of biological matter does not effect the rate of ARD production in a sample in both fresh and salt water.
The Petermann Glacier of Northern Greenland has been associated with producing large, flat, low profile and tabular icebergs in the north Atlantic. The glacier is speculated to have produced a rock loaded, neutrally buoyant iceberg, which was encountered by the CCGS Louis S. St Laurent in the Kane Basin between Ellesmere Island and Greenland on August 17, 2001 during the Canadian German Nares Strait Geo Cruise.
Rock eval analysis of bituminous ice rafted debris (IRD) revealed Kerogen types II III with a peak thermal maturity (T max) range between 385 450 C and a max total organic carbon content (TOC) of 1.28 mg HC/g rock. Thermal maturation combined with petrographic and rock descriptions of the IRD are compatible with mature and postmature occurrences expected along North Greenland. Silurian aged marginal marine to open shelf dolostone, bioclastic debris and skeletal wackestones prevail across southern Hall Land and Washington Land near the Petermann Glacier, NW Greenland and are suspected as the source area for the debris.
The massive floating ice tongue of the Petermann Glacier is flanked by valley walls exceeding 500 m providing increased chance for supraglacial rock accumulation.
Because of their tabular shape, high stability and low profile on the water, these neutral buoyancy icebergs pose a serious threat to navigation in northern waters. This research has revealed recent sightings of similar rock loaded icebergs of a similar source as far south as the offshore petroleum producing areas of Atlantic Canada, emphasizing that they pose a more significant threat than initially assumed.
It is speculated that warm summer temperatures and a record breaking amount of precipitation, leading to unprecedented flooding and closure of the Thule airport in July 2001, may have facilitated mass wasting and possibly glacial surging which resulted in the production of the debris loaded iceberg encountered in August 2001.
Ice contact volcanism, and specifically subglacial volcanism, can provide information about paleo environments such as the extent and thickness of former glaciers and ice sheets. In southwest Iceland, approximately 30 km southeast of Reykjavík on the Reykjanes Peninsula, the regions of Northern Bláfjöll, Vífilsfell, and Arnarþúfur contain structures associated with Pleistocene ice contact volcanism. This study combines remote sensing classification of multispectral satellite imagery, field observations, and geochemical analysis to determine the relationship between these features. Remote sensing classification of SPOT 5 imagery using Geographic Information Systems (GIS) generates 16 significant spectral clusters. Determination of significant clusters and their spatial distribution facilitates subsequent field investigations. Ground truthing of Northern Bláfjöll reveals a flat topped volcano with steep sides that consists of basal pillow lavas, pillow breccia, altered hyaloclastite (palagonite), flow foot breccia, welded scoria, and superincumbent subaerial lava flows. Vífilsfell directly overlies Northern BláfjÖll and encompasses a conical mound of palagonite with isolated welded scoria, volcanic bombs, dykes with pillowed surfaces, and peripheral slump deposits. Arnarþúfur comprises a series of linearly oriented discrete mounds with rhythmically layered fine grained palagonite and clast supported beds that include varying proportions of armoured lapilli. Beds typically contain flow indicators such as climbing ripples, cross beds, and flutes. Electron microprobe analysis of major element concentrations in volcanic glass reveals that Northern Bláfjöll, Vífilsfell, and Arnarþúfur have indistinguishable olivine normative tholeiite compositions. Northern Bláfjöll is a tuya that emerged from a deep englacial melt water lake with a surrounding ice thickness exceeding 400 m, according to the passage zone elevation above the surrounding plain. Vífilsfell is a subglacial mound that formed beneath thin ice conditions with episodic melt water drainage during its emplacement. Arnarþúfur is an ice confined hyaloclastite flow deposit that combines characteristics of pyroclastic density currents, turbidites, and eskers. Statigraphic relationships suggest that Arnarþúfur formed in association with the Vífilsfell eruption as a result of gravity controlled mobilization of unconsolidated volcaniclastic material into an ice confined melt water drainage system. The chemical homogeneity of Northern Bláfjöll, Vífilsfell, and Arnarþúfur suggest a common magma source and rapid emplacement of the volcanic deposits relative to the evolution of the melt.
The Ravn River Valley in Northern Baffin Island, Nunavut, contained a proglacial ice damned lake during the Holocene recession of the Paleo Barnes Ice Cap. The style of deglaciation was complicated. A series of sublacustrine cross valley moraines and both lateral meltwater channels and delta foresets that dip up valley, indicate that initial ice marginal retreat was southward across the west east trending valley. Raised deltas, kame deltas, spillways and paleo lake shorelines in the Ravn River Valley indicate that this ice damned lake had two stillstand lake levels; ~268 m and ~300 320 m throughout its duration. Lake level elevations were controlled by a prominent spillway at the valley head and by contemporaneous glacial ice that was retreating downvalley to the south southwest.
The intimate relationship between lake levels and the receding ice permits a chronology of raised deltas to yield both the lake history and the timing of systematic retreat of the Paleo Barnes Ice Cap. The rate of 46 m of incision into the bedrock spillway will also be able to be calculated. Cosmogenic 10Be as measured to date the two lake levels and one tributary lake by sampling eight raised deltas. A boulder was sampled on one of the surfaces. The remaining samples were topset sands collected from 30 cm depth, below a zone of post depositional mixing due to cryoturbation and bioturbation. The results indicate that the tributary valley near the valley head spillway was deglaciated at 8.3 " 0.3 ka (uncertainty is 1s precision of measurement). Exposure ages from the other 7 samples, including the boulder, range from 37.1 " 1.0 ka to 21.7 " 0.7 ka. Based on the preservation of the glacial and glaciolacustrine features, the relative lack of soil development, and chronology of deglacial events elsewhere on Baffin Island, these 7 ages are considered to be too old. The probable explanations for this disparity are (1) that there was a systematic error in the chemistry during sample preparation, or (2) that the samples all contained a concentration of 10Be that was inherited from exposure prior to final deposition in the deltas. If the latter case is correct, the inheritance would indicate that the long term average steady state erosion rate of the upland plateaus (the source of the deltaic sands) ranged from 38 to 91 m/Myr. This erosion rate is reasonable for bedrock that is affected by zones of wet based (erosive) and cold based (non erosive) ice as has been well established for Baffin Island. Using the tributary delta exposure age, the minimum rate of spillway incision was 5.5 m/ka.
There is currently insufficient information regarding topographic changes in the southern Andes from 32o to 39o S. Mean elevation north of 35o S is 430.7 m, from 35o to 36o elevation is decreasing with a mean 207.8 m and south of 39o the mean 189.2 m. The object of this thesis is to shed some light on other geomorphic indices and determine whether there are other means of quantifying these three zones. A digital elevation map (DEM) was acquired for the study area, and was analyzed using RiverTools software for river network and topography analysis, and ArcMap. In a geomorphometric analysis of any kind, it is important to measure a variety of parameters to establish trends in uplift, erosion and mountain front stability. Analysis of basin relief, stream concavity, hypsometry, tributary asymmetry and mountain front sinuosity found various trends. From north to south, basin relief decreased and hypsometric integral and slope both decreased. Mountain front sinuosity increased moving south, indicating more rounded and mature mountains. Tributary asymmetry suggested differential uplift patterns in the study area, with uplift occurring in the north and in the south east. Stream concavity showed no conclusive pattern. Using these metrics, it was possible to distinguish the zones of high tectonic activity in the area the Liquine Ofqui fault and the Aconcagua fold and thrust zone. Tests of mountain front sinuosity of the range and hypsometry of the basins showed that the southern mountains are more glaciated than other regions. Uplift determined by tributary asymmetry and mountain front sinuosity in the area surrounding the longitudinal valley between 32o and 34o S helped confirm that present day uplift of the valley has taken place since the Late Miocene. Based on these measurements of the topography, I concluded that zones of quantifiably different topography do not exist however the geomorphometrics successfully identified many structural and surficial features of the study area.
Open Limestone Channels are a passive method of treating acid rock drainage, by allowing acid rock drainage to flow through limestone, initiating a neutralizing chemical reaction. Acid rock drainage is a by product of sulphide minerals oxidizing. Any metals in solution precipitate out and form an armored coating on the limestone, decreasing efficiency. There are many ways to treat acid rock drainage; the focus of this project is open limestone channels. Limestone neutralizes acid by reacting calcite, CaCO3, with the acid to produce calcium in solution and carbonic acid. Several experiments were performed to try to determine the key parameters which govern the working of an open limestone channel such as dissolution rate, time, pH, mass loss and mineral content. Basic set up included a storage container for the prepared acid rock solution, a catching container for the treated solution to drip into, and the channel. This set up allowed the acid rock drainage solution to drip steadily into the limestone channel, and allowed for ease of measurements. Results showed trends of what influences the dissolution rates. Major influences are the pH of the solution, the time the solution is in contact with the limestone and the concentration of any metals in solution. Future studies in experiments with open limestone channels should try to narrow the focus of the experiments.
Since the first Nova Scotian gold rush in the early 1860s, gold mining and milling processes have generated tailings piles containing mercury, arsenic, cyanide, and other potentially toxic elements. Most of the gold deposits occur in the Cambro Ordovician Meguma Group of southern Nova Scotia, and mining has been carried out at more than 60 formal gold districts for a total production of 47 t of gold. The Cochrane Hill gold deposit is located in Guysborough County, approximately 15 km north of Sherbrooke. The host rocks consist of amphibolite facies quartzites and slates, and most of the gold is associated with quartz veins that intrude slates rich in arsenopyrite. Mining and milling of gold ore at Cochrane Hill took place from 1877 to 1928, and again from 1981 to 1988, resulting in two separate tailings piles. During the first period of operation, stamp milling and mercury amalgamation were used to extract gold from the ore, and the tailings were slurried into a local drainage. In the 1980s, ball milling and cyanidation were used to process the ore, and the tailings were deposited into an on site impoundment. The main objectives of this study are to: (1) characterize the mineralogy and metal concentrations in the two tailings piles; (2) assess the relative reactivity of metals and metalloids in the amalgamation versus cyanidation tailings; and (3) examine the downstream impacts of drainage from the tailings piles. Forty five samples of tailings were collected from 16 different sites at Cochrane Hill in September 2003, and water samples were collected at 12 locations within and downstream of the tailings in November 2003. Efflorescent salts were also collected from the surface of the cyanidation tailings, and stream sediments were collected to determine the distance that tailings have been transported downsteam. X ray diffraction, scanning electron microscopy and electron microprobe analyses have been completed on select tailings samples. The primary mineralogy of the tailings includes muscovite, biotite, staurolite, quartz, anorthite, and actinolite/tremolite. Secondary mineralogy includes ferric hydroxide, basaluminite, gypsum and turnbull=s blue. Geochemical results show that the amalgamation tailings contain significantly higher Hg concentrations (21 63,000 ppb) than the cyanidation tailings (< 5 25 ppb). Both tailings piles also contain high concentrations of As (280 41,000 ppm), which occurs naturally in the ore. There is a strong correlation present in the amalgamation tailings between Hg, Au, and Ag indicating that there is amalgam present. In the cyanidation there are high concentrations of Zn and Ca that would have been lost during the cyanidation process. There are elevated concentrations of Al, Mn, Ni, Zn, Pb, and S found in the waters at the mine site. The tailings are having a direct effect on the chemistry of the waters close to the mine site but this effect is diminished downstream.
The Greater Himalayan Sequence (GHS) is the metamorphic core of the Himalaya bounded by the Main Central Thrust (MCT) in the south and the extensional South Tibetan Detachment (STD) in the north. The GHS of the Bhutan Himalaya also contains the out of sequence Kakhtang Thrust and several sedimentary klippen associated with the STD. The dominant metamorphic feature of the GHS is an inverted metamorphic sequence that occurs from the MCT (amphibolite facies) with higher metamorphic grades (up to granulite facies with associated migmatites and leucogranites) occurring towards the north. In Bhutan, this inverted metamorphic sequence is repeated several times within the GHS, with lower grade metamorphic assemblages (garnet staurolite conditions) occurring in several locations B near the MCT, at the base of the klippen, and in footwall of Kakhtang Thrust.
A comparison of the deformational and metamorphic history of garnet staurolite biotite schists from the sole and roof of the GHS provides insight on the tectonic history of the GHS as a whole and in relation to the other structural units of the Bhutan Himalaya.
Geothermobarometry results of the garnet staurolite schists show that just below the MCT peak metamorphic conditions occurred at 611"27 1C and 10.2"1.0 kbar, contemporaneous to dominant flattening combined with top to the south shearing. The Paro metasediments in the Paro region of eastern Bhutan show a peak metamorphic temperature of 702"43 1C and pressure of 9.8"1.6 kbar. This unit, previously described as either part of the LHS or of the GHS, is reinterpreted as a window to the Lesser Himalayan Sequence because it is bounded by opposite dipping normal faults and has metamorphic conditions compatible with that structural level. Pressure conditions decrease above the STD with an increase in structural level, whereas the temperature conditions range from 608"251C to 715"501C. These garnet staurolite schists of the Chekha Formation exhibit a dominant deformation of vertical shortening, overprinted by north to northwest normal fault kinematics as expected in the STD shear zone. A garnet staurolite schist of the footwall of the Kakhtang Thrust is petrographically equivalent to those of the Chekha Formation and exhibits the same dominant pure shear flattening, with P T conditions of 654"261C and 8.2"1.2 kbar similar to those in the klippen. This unit, the Naspe Formation, can be thus correlated as part of the Chekha Formation.
The metamorphic data obtained here combined with published data indicate that the peak temperature increases in the northwards towards higher structural levels, and then above the STD progressively decreases. At the same time, the pressure at peak temperature progressively decreases from ca. 10 kbar at the base of the GHS to approximately 8 kbar in the roof of the GHS. This relatively simple P T pattern has been subsequently overprinted and repeated by later faulting and thrusting. This P T pattern in the GHS provides an important constraint for models of Himalayan tectonics.
Found mainly within the Carboniferous basins of Nova Scotia, onshore Cretaceous deposits provide a glimpse into the environment, structural and stratigraphic setting of the Atlantic Cretaceous. Previously unknown deposits of probable Cretaceous age have been discovered at Avondale, Mantua (Fundy Gypsum Bailey Quarry), and Wentworth Road (Fundy Gypsum Wentworth Dark Quarry). Five new sites have been uncovered, one at Avondale (1.5x4m), four in Bailey Quarry (from 3m to 6x15m), and one in Wentworth Dark Quarry (1x3m). Additionally, a drill core, between the Bailey Quarry and Millers Creek Quarry (Mantua) penetrated >40m of probable Cretaceous material in a narrow karstic Atrench@. Although small, these occurrences (attributed to the Chaswood Formation) have considerable significance in linking the Cretaceous catchment area with thick, hydrocarbon-prone deltaic and marine deposits of the Scotian Shelf.
The deposits consist of sand, lignite, clay and quartz-rich gravel, resting unconformably on gypsum of the Windsor Group. The Cretaceous materials mainly occupy fractures, sinkholes and depressions within the gypsum, with especially clear relationships to gypsum karst at Avondale where sands have penetrated fractures in the gypsum for several meters. The sand and gravel are fluvial in origin, and some thick clay with lignite may record associated lakes. Palynological studies at two localities confirm an age of Aptian-Albian. Samples of charcoal from Bailey Quarry site BQ 4 near Mantua represent ginkgo, conifer and angiosperm wood, supporting a Mesozoic age, possibly Aptian-Maastrichtian.
Large gypsum crystals, confirmed using XRD, locally cement the quartz-rich gravel and sand. Other constituents include patches of clay and iron oxide matrix, some feldspars (K-feldspar (microcline), plagioclase), and small amounts of muscovite, biotite and heavy minerals (rutile, ilmenite, staurolite, and zircon in order of abundance). The feldspars are strongly altered, suggesting extensive weathering of the source area, and the sands are classified as quartz-arenite to subarkose. The Meguma and the South Mountain Batholith are the likely sources for much of the material. Recycling from Carboniferous clastic strata is also likely.
Although water occupies 70% of the earth's surface, we know more about the moon and Mars than we do
about the depths of our own oceans. This has become even more apparent with the recent discovery of
deep-sea coral on the Scotian Margin. Despite inadvertently hauling up coral caught in fishing gear
for the past two centuries, it was less than a decade ago that reductions in fishing quotas prompted
a fisherman to bring a coral sample to scientists' attention.
Nine deep-sea coral specimens of the tree-like coral Primnoa resedaeformis from water depths between 300-500m in the Northeast Channel were analyzed to identify the associate foraminiferal assemblage. A total of 29 foraminiferal species have been found attached to the coral, two of which may be used to indicate coral distribution on the margin from sediment samples.
The presence of one of these indicator species, Discanomalina semipunctata in abundances of 5% or greater has been used along with Detrended Correspondance Analysis to identify past coral locations from 89 sediment samples. Thirty sites have been identified as having higher potential for present and past deep-sea coral occurrences. The discovery of these coral associated foraminifera provides a cost effective means and more accurate way of mapping both paleo-coral and coral distribution. The remnant foraminifera found in the sediment record provide a proxy for the paleo-coral distribution, thus providing a basis for sustainable conservation practices.
The high abundance of planktonic foraminifera attached to the coral specimens has many potential indications; a previously unknown life stage within a planktonic foraminifera's life cycle or evolutionary response to changing environmental parameters. This may also affect the accuracy of derived paleo-sea surface temperatures that unknowingly used these 'pseudo-planktonics' in their analyses.
Coastal exposures of the Sydney Mines Formation (Westphalian D) at Morien Bay, Nova Scotia record
stacked high-frequency sequences 11-38m thick of fluvial and restricted marine strata with economic
coals. The cliffs at Morien Bay are among the world's best continuous Carboniferous coal measure
exposures. Sections 75 - 160 m thick at Schooner Pond, Long Beach, and Morien South provide a ~10km
downdip direction traverse that encompasses the McRury to Bouthillier coal seam interval. The dominant
facies assemblage represents a poorly drained coastal plain and comprises grey sandstone and shale,
hydromorphic paleosols, thick coals and distributary channel bodies. The coals are sulphur-rich,
suggesting a marine influence, and are up to 2.8 m thick. A second facies assemblage represents a well
drained alluvial plain and comprises red mudstone, nodular calcrete, vertic red and grey paleosols,
and dryland channel bodies; it predominates at Morien South. Repetition of these facies assemblages
represents cycles of relative sea level change, probably linked to glacioeustasy which is inferred to
have dominated the formation's stratal architecture.
Applying a sequence stratigraphic framework, marine flooding surfaces are recognized by thick,
extensive coal seams or thin coal or coaly shale. Maximum flooding surfaces can be represented
by faunal-concentrate limestones rich in bivalves and ostracods and form excellent regional
stratigraphic markers. Three main types of sequence boundary are (a) single well-defined
calcretes with minimal sedimentation for long periods, (b) sequence boundary zones of
vertisol-type paleosols several metres thick in areas of higher sedimentation, and (c)
sequence boundary zones of small paleovalley fills or larger dryland channel bodies in
association with paleosols. Some calcretes can be correlated between sections and across the
basin. The vertisol-type paleosols are also widespread but more difficult to correlate.
Within seven stacked sequences, wetland facies and economic coals are well represented within
the Transgressive and Highstand Systems Tracts. 'Dry' and 'wet' subdivisions of the Highstand
Systems Tract reflect upward passage into red and grey dryland facies which may represent
falling sea level prior to the formation of the sequence boundary. Systems tract terminology
could not always be applied to the alluvial plain strata.
Stratal packages thicken in Morien Bay when compared to sections in the western part of the
Sydney Basin, due to increased subsidence. Particularly at Morien South, increased amount of
red floodplain material suggests a more proximal and well-drained region towards the southern
limb of the Morien Syncline. Unidirectional paleocurrent data from channel bodies yields an
overall paleoflow direction of 347o (NNW) with vector means of paleocurrent measurements of
029o (ENE), 001o (N), and 334o (NNW) at Schooner Pond, Long Beach and Morien South,
respectively. This suggests a local source to the south of Morien Bay, probably the Proterozoic
rocks of the Scatarie Ridge and regional sources within the northern Appalachian Mountains.
Some channel bodies with NE paleoflow indicate a subsidiary mode sub-parallel to the axis of
the Morien Syncline.
An abundant paleobotanical record in grey, coal-bearing strata comprises erect lycopsids,
prostrate logs and abundant compression flora. Thirty lycopsid trees in growth position had
trunk diameters from 0.25-0.6 m. Lepidodendron sp. and Sigillaria sp. are the two main lycopsids
identified. Compression flora consists of pteridosperms (Alethopteris sp. and
Neuropteris sp.), marattialean tree-ferns (Pecopteris sp.), sphenophytes (Sphenophyllum sp.),
Cordaites, and Calamites. Few plant specimens were recovered from redbed intervals. A rare,
well-preserved tetrapod trackway with 18 tracks is provisionally attributed to Baropezia
sydnensis, a temnospondyl amphibian.
Textural and chemical characterization, and U-Th-Pb chemical dating were carried on monazites from upper greenschist to granulite facies rocks belonging to the Paleoproterozoic (ca. 1.8-1.9 Ga) Longstaff Bluff Formation (LBF) using an electron-microprobe (EMP).
In the LBF, monazite appears early in the prograde metamorphic sequence. Upper greenschist rocks contain small but widespread metamorphic monazite. Abundance and size of LBF monazite constantly increase with metamorphic grade. Transition from the Sil-Kfs zone to the migmatite zone coincides with a significant increase in size and abundance of monazite. Chemical zoning is generally weak in low- to medium grade samples. Monazites from migmatitic samples are the most abundant and they are commonly zoned in U, Th and Y.
Chemical data show that metamorphic grade has a strong influence on monazite composition. HREE, Ca, Si, Th, U, and Y increase with metamorphic grade, while LREE abundance decreases. Spread in values at higher grade suggests that factors other than metamorphic grade also exert control on monazite chemical composition. Sharp changes in monazite composition are observed at the transition from the Sil-Kfs zone to the migmatite zone, notably a steep increase in Y content. Highly resorbed garnets are reported from this transition.
Electron microprobe U-Th-Pb chemical dating of monazite allowed recognition of 6 different age populations within the LBF monazites. Results correlate very well with available U-Pb isotopic ages. Detrital grains were identified. Episodes of metamorphic monazite growth were dated at ca. 1880 Ma (E1), 1850 Ma (E2), 1830 Ma (E3), 1800 Ma (E4) and 1770 Ma (E5). Chemical age data suggest the existence of a northward younging age gradient for E2 and E3 events. These two events are mainly recorded in the southernmost transects. E4 is synchronously recorded throughout the field area and E5 is mainly recorded in the northern part of the study area. Constraints from petrological setting of monazite grains and chemical mapping were used to interpret the ages.
Supervisor: Rebecca Jamiesom
Alexander (Sandy) Grist
Subsidence and sedimentation in offshore basins at rifted continental margins are intimately related to the uplift and exhumation of the sediment source areas. An understanding of the regional and temporal distribution of onshore denudation is critical in the evaluation of models of rifted margin development. Offshore strata are often inaccessible and can only be studied in samples obtained from wells, and the loss of the onshore geological record through erosion requires that estimates of regional denudation of near-surface rocks in these environments be obtained by other means. Through the application of low-temperature thermochronometry we can elucidate the time-temperature histories recorded in the extant strata, and provide quantitative constraints on the development of these coupled margin - source region systems. In this thesis apatite fission track (FT) and (U-Th)/He thermochronology and vitrinite reflectance are used to obtain estimates of cooling and inferred denudation for 3 onshore areas; 1) the Triassic - Early Jurassic Fundy Basin, a failed rift that was subsequently inverted and exhumed as part of the onshore of the southern Canadian Atlantic margin; 2) the Sverdrup Basin, a Late Paleozoic - Mesozoic intracratonic basin and failed rift in the Canadian Arctic Archipelago that developed following the Ellesmerian Orogeny, and was subsequently inverted during the Paleogene Eurekan Orogeny; 3) the Nares Strait - Kane Basin - Smith Sound region of eastern Ellesmere Island and western Greenland, which was exhumed during Late Paleozoic and Mesozoic time as a sediment source region for the Sverdrup Basin, and was also affected by the Eurekan Orogeny. Geologically constrained FT inverse and (U-Th)/He forward thermal models for the southern Canadian Atlantic onshore margin demonstrate that most rift-related exhumation likely occurred during the rift-drift transition in Early Jurassic time. These models also suggest that significant (ca. 25 oC) post-Paleocene cooling has occurred that can be explained by a combination of limited exhumational cooling related to decreased eustatic sea level, and the propagation to depth of decreased paleo-mean annual surface temperatures. FT modelling of the Sverdrup Basin demonstrates that basin inversion was initiated during latest Cretaceous - Early Paleocene time. Cooling is greatest in the hanging walls of thrust faults, and significant thermal history discontinuities occur across faults, suggesting these structures were active during the Eurekan Orogeny, and are therefore likely to be poor traps for hydrocarbons generated during Mesozoic burial heating. Thermal modelling of the Nares Strait - Kane Basin - Smith Sound region are consistent with at least two phases of denudational exhumation that are likely related to Sverdrup Basin subsidence, one during early rifting and widespread clastic sedimentation in Late Paleozoic time, and one during a period of increased subsidence rates and high sediment supply during Triassic time. FT and (U-Th)/He data for the Nares Strait region reflect relative plate movements between Ellesmere Island and Greenland during the Eurekan Orogeny, including mafic volcanism and exhumation cooling following flank uplift, or transpression, and minor thrust exhumation. The data also suggest only minor thermal effects from this tectonism along the strait, indicating that it may have been partitioned into a broad belt across Ellesmere Island.
Supervisor: Marcos Zentilli