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The Mesoproterozoic Husky Creek Formation is an interlayered redbed and basalt package that overlies a ca. 2.5 km thick, regionally extensive basaltic plateau linked to the 1.27 Ga Mackenzie Large Igneous Province. This succession provides an opportunity to study the interaction between contemporaneous fluvial sedimentation and flood basalt volcanism. The Husky Creek Formation is approximately 1900 m thick, consisting predominantly of fluvial channel and subordinate floodplain and eolian strata dominated by lithic detritus intercalated with basalt flows. U–Pb dating of detrital zircon grains collected from four stratigraphic levels in the Husky Creek Formation reveals two main age groupings: (1) a 1270 Ma peak attributed to the Mackenzie Large Igneous Province; and (2) Pre-1.6 Ga detrital zircon ages, which reflect sources from a broad region of northwestern Laurentia and are interpreted to be recycled from underlying sedimentary rocks of the Hornby Bay Basin. An upsection decrease in the proportion of ca. 1270 Ma zircon grains, coupled with increasing sandstone compositional maturity, reflects the expansion of the drainage basin during burial of a volcanic pile, with recycling becoming more dominant as the Husky Creek Formation accumulated. The Husky Creek Formation was deposited in the waning stages of the Mackenzie Igneous Event by west-flowing rivers into a geographically restricted basin above an extensive mafic volcanic plateau. This paper provides insight into fluvial basin development during the aftermath of one of Earth's largest igneous events. [ABSTRACT FROM AUTHOR]

Detrital zircon from three coarse-grained marine siliciclastic rocks was analyzed for U–Pb, Lu–Hf, and trace element compositions to constrain the timing of deposition and sediment provenance of the Cunningham Lake formation (formerly siliciclastic unit of the Sitlika assemblage) in north-central British Columbia. This strategy tests previously proposed sedimentary linkages between the Cache Creek terrane and the westerly rocks of the Stikine terrane. All three samples indicate maximum depositional ages at ca. 205–202 Ma (Rhaetian). The samples contain a predominant ca. 225–215 Ma detrital population, sourced from proximal contemporaneous volcanic arcs, and minor Permian to Middle Triassic and Carboniferous arc-derived detrital populations. The absence of Precambrian grains is consistent with the strongly suprachondritic zircon compositions (εHf(t) = +7 to +20), and indicates exclusively juvenile sources for the Cunningham Lake formation. Late Triassic sources of zircon are not known in the Cache Creek terrane and, except within western Stikine terrane, are uncommon among the Intermontane terranes that amalgamated with the Cache Creek terrane during Late Triassic–Early Jurassic. The Stikine suite (ca. 230–214 Ma) and coeval volcanic rocks in western Stikinia are the most probable sources of Late Triassic detritus for the Cunningham Lake formation. Stikinia's Paleozoic basement is the probable source of Carboniferous detrital zircon. Volcanic arc–backarc complexes in the Cache Creek terrane are the most likely sources of Permian to Middle Triassic detritus in the Intermontane terranes. Accordingly, the siliciclastic rocks of the Cunningham Lake formation represent an overlap sedimentary succession that links Stikinia to the Cache Creek terrane by the latest Triassic. [ABSTRACT FROM AUTHOR]

Three Orosirian basins and associated foreland thrust-fold belts are preserved on the margins of the Slave craton. All three are related to orogenic belts where oceans opened and later closed, uniting new crustal partners. The Great Slave basin differs from the Kilhigok and Coronation basins in ways that have defied explanation. It lacks a passive margin sequence and hosts two discrete igneous suites, separated by large-scale thrusting, that occurred well after the adjacent paleocean had closed. Here we report U–Pb zircon geochronology by chemical abrasion isotope dilution thermal ionization mass spectrometry for a member of each suite to constrain the age and origin of postcollisional thrusting. A widespread pulse of mainly phreatic alkaline volcanism, coeval with renewed foredeep flexure, occurred at 1889.0 ± 0.7 Ma (2σ internal error). A quartz-monzodiorite body, one of a belt-parallel chain of laccoliths that postdate thrusting, was emplaced at 1866.9 ± 0.9 Ma. These ages bracket renewed foredeep sedimentation and thrusting that telescoped major facies zones and was rooted within the basin. The older age is 70 and 30−60 Myr younger than collision in the Thelon and Taltson orogens, respectively. We attribute postcollisional thrusting and foredeep subsidence to "eduction"—the upward and outward ejection of partly subducted crust—and postulate that the top of the ejected wedge was a normal-sense detachment fault projecting beneath the Nonacho basin. We infer that eduction was triggered by slab failure, producing alkaline volcanism, and ended with delamination and laccolith emplacement. Eduction was facilitated by tradewind-driven erosion. Delamination was enabled by crustal transfer to the educted wedge, reducing footwall buoyancy. Slab failure and/or delamination removed the passive margin. [ABSTRACT FROM AUTHOR]

The Mesoproterozoic Frontenac terrane in the southern Grenville Province of Ontario is separated by shear zones from the Composite Arc Belt to the west and the Adirondack Lowlands to the east. The majority of the terrane is made up of granulite-facies metasedimentary rocks that are the oldest lithologies recognized in the terrane. Five samples were selected for U–Pb geochronology to constrain (1) metamorphic age, (2) depositional age of sedimentary protoliths, and (3) source regions of detrital zircon. Two pelitic gneisses and a marble are dominated by metamorphic zircon, whereas two quartzites contain a diverse population of detrital zircon that are surrounded by metamorphic overgrowths. Metamorphic zircon have 206Pb/207Pb ages of 1.19–1.16 Ga, and a small population is 1.22 Ga. These ages correspond to the Shawinigan and Elzevirian orogenies and provide minimum ages for deposition. The youngest detrital grains with ages of 1.25–1.24 Ga provide maximum depositional ages. Quartzites (and pelitic gneisses) have a wide range of detrital zircon ages that reflect local Mesoproterozoic Grenville sources and Paleoproterzoic and Archean sources in the northern Grenville Province and elsewhere in Laurentia. Most notable is a large population of 1.9–1.8 Ga zircon, which points towards derivation from the Penokean orogen in the midcontinent or Makkovikian–Ketilidian orogen of Labrador and Greenland, indicating long sedimentary transport distances. The similarities in depositional ages and detrital zircon ages between Frontenac terrane and Adirondack metasedimentary rocks suggest a shared sedimentary history, which we interpret as deposition in the same Trans-Adirondack backarc basin at ca. 1.25 Ga. [ABSTRACT FROM AUTHOR]

The Laird Lake property, southwest Red Lake greenstone belt, straddles the contact between the Balmer (2.99–2.96 Ga) and the Confederation (2.74–2.73 Ga) assemblages. The property is 10 km along strike from the Madsen and Starrat–Olsen Au mines that are hosted near the contact. The Balmer assemblage consists of fine-grained, aphyric, locally pillowed mafic volcanic rocks, ultramafic intrusive and volcanic rocks with flow breccia textures hosting local spinifex-bearing clasts, and banded-iron formations. In contrast, the Confederation assemblage comprises porphyritic mafic volcanic rocks intercalated with intermediate to felsic volcanic rocks that include crystal lapilli tuffs, crystal tuffs, and tuffs. The Balmer assemblage is composed of tholeiitic mafic volcanic rocks with minor Al-undepleted komatiites, whereas the Confederation assemblage is calc–alkalic. Neodymium isotopes, in conjunction with trace element geochemistry, suggests that parts of the Balmer assemblage were weakly contaminated by an older intermediate basement. Both arc and back-arc volcanism occurs in the Confederation assemblage, with the arc rocks showing a stronger crustal component than the back-arc rocks. A maximum U–Pb age of 2741 ± 19 Ma for a crystal tuff and an age of 2737.68 ± 0.79 Ma for a diorite are consistent with a Confederation assemblage affinity for the intermediate calc–alkaline rocks south of the Au-bearing horizon. The Balmer assemblage represents an oceanic plateau formed by plume magmatism on the margins of the North Caribou Terrane, whereas the Confederation assemblage at Laird Lake formed in an oceanic arc setting where both arc and back-arc volcanism occurred simultaneously. [ABSTRACT FROM AUTHOR]

Igneous rocks of the Jurassic continental arc of southwest North American Cordillera crop out in the region between Cananea and Nacozari, in northeastern Sonora, Mexico. Contemporaneous igneous rocks occur farther south in the Nazas rift province; however, their tectonic affinity is debated between the southern extension of the Cordilleran arc and an origin associated with decompressive mantle melting during the Pangea breakup. We consider that the studied rocks represent the southernmost expression of the Jurassic continental arc. Four magmatic units are distinguished based on geology, U–Pb zircon geochronology, and geochemical composition. They comprise the Buenos Aires granite dated at 183.8 ± 1.1 Ma, the Mababi granite with ages of 175.5 ± 1.8, 173.5 ± 1.8, and 171.7 ± 1.0 Ma, the Elenita Formation volcanic rocks dated at 169.7 ± 1.7 Ma, and the Cerro Blanco granite dated at 162.3 ± 2.4 Ma. The studied samples correspond to highly differentiated rocks with high-silica contents (69–76 wt.%), low Mg# values (mostly <45), and alkali–calcic and peraluminous compositions suggesting crustal contamination. LREE-enriched normalized slopes with negative Eu anomalies and multielement plots characterized by well-developed negative anomalies of Nb–Ta, P, and Ti provide an unequivocal signal of the continental arc nature. In contrast to the Nazas province, where the Jurassic magmatism consists of discreet volcaniclastic sequences deposited in extensional basins with no evidence of plutonic rocks, the Jurassic continental arc of Arizona and northern Sonora forms a regionally coherent geological feature characterized by large exposures of volcanic and plutonic rocks. [ABSTRACT FROM AUTHOR]

The Huaduoshan Cu–Mo prospect is in the Duobaoshan orefield, northeast China. The Cu–Mo mineralization occurs in the granodiorites as veinlet-disseminated. The ore-forming process can be divided into four mineralization stages: (I) quartz–pyrite–magnetite; (II) quartz–pyrite–chalcopyrite ± molybdenite; (III) quartz–pyrite–molybdenite–chalcopyrite–sphalerite; and (IV) quartz–calcite–minor pyrite. Liquid-rich two-phase aqueous (L-type), vapour-rich aqueous (V-type) and daughter-minerals three-phase (S-type) fluid inclusions (FIs) were identified at Huaduoshan. The last two types of FIs are absent in stages III and IV. The homogenization temperatures of FIs from stages I to IV are 375–438, 335–378, 283–335, and 223–267 ℃, with corresponding salinities of 2.4–50.4, 2.1–44.9, 2.7–10.1, and 1.7–7.3 wt. % NaCl eqv., respectively. The H–O isotope data of quartz in stages I (δ18OH2O = 6.1–8.0‰, δDH2O = −102.4–−94.6‰) show a magmatic origin of ore-forming fluid; the decreasing δ18OH2O (−6.8–3.2‰) and δDH2O (−117.1–−98.5‰) values of quartz in stage II–IV show the fluid mixing with meteoric water. The S–Pb isotopic values (δ34S = −2.7–0.8; 206Pb/204Pb = 18.236–18.599; 207Pb/204 Pb = 15.504–15.557; 208Pb/204Pb = 37.816–38.629) of pyrites indicate that the ore-forming materials are of magmatic origin. Fluid boiling and mixing may be the major mechanisms of ore precipitation. Zircon U–Pb age (172.1 ± 0.5 Ma) and geochemical data indicate that the ore-related granodiorites are I-type rocks formed in the subduction setting of the Paleo-Pacific Ocean Plate in the Early–Middle Jurassic. In conclusion, we propose that the Huaduoshan Cu–Mo prospect is a porphyry deposit and has potential for further exploration of porphyry Cu–Mo prospecting. [ABSTRACT FROM AUTHOR]

The Yama fluorite deposit in the Qilian Orogen in NW China is characterized by predominant granitic magmatism and fluorite mineralization. The wall rocks hosting the fluorite–quartz veins in the Yama area consist of the Yama porphyritic syenogranite and the Wulandawu syenogranite. In this study, the major and trace element compositions, zircon U–Pb ages, and zircon Hf isotopes and trace element compositions were investigated. Two samples for the Yama porphyritic syenogranite yielded weighted mean 206Pb/238U zircon ages of 440.7 ± 4.8 and 447.9 ± 6.0 Ma, and one sample for the Wulandawu syenogranite yielded a weighted mean 206Pb/238U zircon age of 441.2 ± 5.0 Ma, all of which indicate a Late Ordovician to Early Silurian crystallization age. Geochemically, both syenogranites are peraluminous, with high alkali contents, low Zr + Nb + Ce + Y contents, relatively low (K2O + Na2O)/CaO ratios, and high Rb/Sr and Rb/Ba ratios, suggesting that they are fractionated S-type granites. They have zircon εHf(t) values of −14.9 to −4.4 and −12.2 to −4.5, respectively, suggesting that they were derived from the partial melting of pelitic-rich sources within the relatively shallow Paleoproterozoic reworked crust. The detailed geochronological and geochemical data suggest that the studied syenogranites were emplaced in a post-collisional setting related to the closure of the South Qilian Ocean. Finally, they have relatively low quantitative oxygen fugacity values, indicating relatively reduced redox states, but their very low zircon Ce4+/Ce3+ ratios, low whole-rock K/Rb ratios, relatively high Nb/Ta ratios, and low Zr/Hf ratios suggest that they are not likely to form important W–Sn deposits and related fluorite deposits. [ABSTRACT FROM AUTHOR]

The 100 m thick stratigraphic section exposed at Dinosaur Provincial Park (DPP; southern Alberta) contains bentonites that have been used for more than 30 years to date DPP's rocks and fossils using the K–Ar decay scheme. Limited reproducibility among different vintages of K–Ar and 40Ar/39Ar ages inhibited the development of a high-resolution chronostratigraphy. Here, we employ and further test a recently completed U–Pb geochronology and associated age-stratigraphy model to update temporal constraints on the Park's bentonites, formational contacts, and other markers. In turn, we document rock accumulation rates and calibrate ages and durations of informal megaherbivore dinosaur assemblage zones and other biozones. Weighted mean 206 Pb/238 U ages from five bentonites range from 76.718 ± 0.020 to 74.289 ± 0.014 Ma (2σ internal uncertainties) through an interval of 88.75 m, indicating a duration of ∼2.43 Myr and an overall rock accumulation rate of 3.65 ± 0.04 cm/ka. An increase in rate above the Oldman–Dinosaur Park formational contact conforms to a regionally expressed pattern of increased accommodation at ∼76.3 Ma across Alberta and Montana. Palynological biozone data suggest a condensed section/hiatus in the uppermost portion of the Oldman Formation. Dinosaur assemblage zones exhibit durations of ∼700–600 kyr and are significantly shorter than those in the overlying Horseshoe Canyon Formation. A decreased rate in dinosaur assemblage turnovers in the last eight million years of the Mesozoic in western Canada may be explained by withdrawal of the Western Interior Seaway and the expansion of ecologically homogenous lowlands in its wake. [ABSTRACT FROM AUTHOR]

The article focuses on the discussion of proposed revisions to the geological framework of the Fire Bay area in northern Ellesmere Island, Canada, specifically addressing changes to the Ordovician–Silurian stratigraphy and the interpretation of the "Fire Bay Fault." Topics include a review of the background geology established by Trettin in 1998, the proposed revisions by Koch et al. in 2022 based on new geochronology and biostratigraphy.

The Nemiscau subprovince is a metasedimentary rocks-dominated sequence of the Archean eastern Superior Province. It is bounded by the gneissic and tonalite-trondhjemite-granodiorite (TTG) rocks-dominated La Grande and Opatica subprovinces. The Nemiscau consists of variably migmatized metasedimentary rocks and felsic to intermediate gneisses and plutonic suites. Mafic-to-ultramafic metavolcanic rocks occur along its northern and southern boundaries. Previous structural and metamorphic studies suggested that it was the result of subduction-related, accretionary and collisional tectonics with adjacent plutonic terranes during the Kenorean orogeny. This study integrates various sets of structural, metamorphic, and U-Pb geochronological data suggesting a long-lasting tectonometamorphic evolution between ca. 2843 and 2598 Ma. Four tectonometamorphic events have been recognized. The first event (D1) is only locally preserved and occurred shortly after the deposition of the oldest volcanic sequences of the Nemiscau (ca. 2756–2736 Ma) under amphibolite facies metamorphic conditions (M1). The kinematic analysis of shear zones bounding the supracrustal sequences of both the Nemiscau and La Grande subprovinces suggests their relative crustal sinking as compared to TTG of the La Grande and Opatica subprovinces, shortly after deposition (at ≤2724 and ≤2706 Ma, respectively). Sedimentation was followed by regional dip-slip-dominated (D2) deformation between ca. 2704 and 2671 Ma, coeval with extensive high-grade granulite facies metamorphism (M2) and anatexis in the Nemiscau subprovince from ca. 2697 to 2685 Ma, followed by exhumation between ca. 2677 and 2671 Ma. This D2 event was followed by regional-scale dextral strike-slip shearing (D3) from ca. 2658 until 2621 Ma at amphibolite facies metamorphism (M3). The youngest deformation event, D4, was accompanied by strain localization along brittle-to-ductile conjugated shear zones and waning crustal cooling from amphibolite to greenschist facies conditions at ca. 2598 Ma and younger. It is suggested that the Nemiscau, La Grande, and Opatica subprovinces represent a single composite terrane, and that their mutual boundaries do not correspond to "collisional sutures" between different crustal blocks or microcontinents. The Nemiscau subprovince is interpreted as a sedimentary sequence unconformably overlying a ca. 2760–2756 Ma (and older) basement made up of volcanic and crosscutting TTG. In terms of tectonic evolution, the overall structural architecture and isotopic ages of the Nemiscau, La Grande, and Opatica subprovinces support a tectonic model in which the vertical transfer of crustal material occurred during the early stages (D2) of regional deformation, which evolved into a predominant lateral crustal flow of the ductile crust during later stages (D3–D4). A non-uniformitarian tectonic model for the Archean more adequately accounts for synchronous vertical and horizontal tectonism as preserved in the Nemiscau basin. [ABSTRACT FROM AUTHOR]

Petrological modeling and geochronology (Lu–Hf garnet, U–Pb monazite, zircon, and titanite) for seven mid-amphibolite to granulite-facies metamorphic rocks in the Thelon tectonic zone (Ttz) provide new insights into the evolution of this orogen. A Grt-Sp-Sil diatexite records 2.01–2.00 Ga garnet and monazite growth during >830 °C contact metamorphism associated with voluminous convergent margin plutonism. The most widespread, 1.96–1.90 Ga metamorphism is associated with clockwise pressure (P)–temperature (T) paths, indicating it was driven by crustal thickening. Earlier (1.96–1.92 Ga) and lower temperature (630 °C–730 °C; 6–8 kbar) metamorphism in the eastern Slave craton contrast with ∼860 °C (7.5 kbar), 1.91–1.90 Ga diatexites in the central, Paleoproterozoic plutonic rock-dominated, core of the Ttz. These differences are interpreted to reflect lower vs. upper plate settings, respectively. A contribution of mantle heat is suggested by the counter-clockwise P–T path and 885 °C (5.7 kbar) conditions recorded by diatexite associated with c. 1.9 Ga peraluminous leucogranite that dominates a corridor along the Ttz–Rae craton boundary. A tectonic model is proposed wherein the Ttz evolved at an accretionary margin after rifting of Ttz microcontinent (mTtz) off the Rae craton at c. 2.2–2.1 Ga. Voluminous plutonism at 2.01–1.98 Ga formed via east-dipping subduction under mTtz. Following 1.97 Ga collision of the Slave craton and mTtz, west-dipping subduction generated 1.96–1.95 Ga plutonism in the composite mTtz-Slave upper plate. Collision of Rae craton at 1.95–1.94 Ga led to crustal thickening, widespread 1.91–1.90 Ga high-grade metamorphism and extensive crustal melting in the central Ttz. [ABSTRACT FROM AUTHOR]

Mount Garibaldi Volcanic System (MGVS) is the southernmost member of Garibaldi Volcanic Belt (GVB), the northern (Canadian) segment of the Cascade Volcanic Arc. Temporally episodic explosive to effusive eruptions may be associated with peak ice unloading after glacial maxima. Rapid and widespread deglaciation of the overlying ice sheet, and glacial rebound, have altered the physical characteristics of the landscape whilst the system is thought to have been in long repose for over 10000 years. Over the last 60 years, the region has become heavily populated due to increased tourism and all-season recreation opportunities. MGVS poses the greatest volcanic threat to the human population and built infrastructure between Vancouver and the resort municipality of Whistler. We believe that this system is a priority for further scientific research, given that its already "very high" overall threat score would likely increase if there was a better understanding of its eruptive history and hazards. Using published and field evidence, we show that potential hazards, related to the volcanic environment of this system, to the settlement of Squamish include voluminous lava flows, pyroclastic density currents triggered by lava dome collapse, tephra fallout, debris flows, and lahars. As relatively few exposures in the system have been dated using modern geochronological techniques, we take this opportunity to (re)calibrate published radiocarbon ages of relatively recent eruptions in GVB. [ABSTRACT FROM AUTHOR]

This article presents a history of the development of U–Pb geochronology with emphasis on the role of Canadian researchers and some of its applications to Canadian geology. Modern U–Pb dating is the result of work by many individuals over the past 60 years, but the most important was Tom Krogh, who established methods that allowed determination of precise ages (<0.1% errors) on zircon using isotope dilution thermal ionization mass spectrometry. This was followed by the introduction of new analytical approaches by others, notably secondary ion mass spectrometry and laser ablation inductively coupled plasma mass spectrometry that allow intracrystal domains to be dated. U–Pb geochronology is now an indispensable tool for understanding the Earth. In collaboration with field mapping, it has vastly improved our understanding of the geological history of Canada as well as important geological events such as mass extinctions, secular changes in geological processes, and the birth of the solar system. [ABSTRACT FROM AUTHOR]

The area northeast of Sudbury, Ontario, is well known for hosting one of the largest unexplained geophysical anomalies in the Canadian Shield, the Temagami Anomaly. In search of a geological explanation for this anomaly, low-grade metamorphic ultrabasic dykes have been discovered in the overlying Huronian Supergroup sedimentary rocks, both in outcrop and in a deep drill core. Here, we report on the first geochemical and geochronological data obtained on these dykes and compare these data with known magmatic units in and around the 1850 Ma impact-generated Sudbury Igneous Complex (SIC). The NW-striking dykes, which cut across sedimentary rocks of the ca. 2.3 Ga Cobalt Group, and which are, in turn, crosscut by pseudotachylitic breccia, are characterized by distinctively high concentrations of Ti, P, Nb, and Zr, highly fractionated rare earth element patterns (La/YbN 7.6–15.5), and a lack of crustal contamination (Nb/Th > 10). Such features are typical of modern ocean island basalts but very different from Palaeoproterozoic rocks previously documented in the wider region. Multigrain U–Pb laser ablation inductively coupled plasma mass spectrometry analyses performed on magmatic titanite and apatite with high Th/U ratios yielded 1876.0 ± 8.7 and 1880.9 ± 8.3 Ma, respectively, which we interpret as the intrusion age of the dykes. This interpretation is supported by similar whole-rock Sm-Nd model ages of 1890–2000 Ma (initial εNd +2.5). This magmatic event in the footwall of the SIC shortly before the impact was coeval with, and likely genetically related to, the 1.88–1.87 Ga Circum-Superior Large Igneous Province. [ABSTRACT FROM AUTHOR]

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Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)