Joggins,Nova Scotia

Joggins is a famous fossil locality in Nova Scotia, Canada. Hewn by some of the world's highest tides on the Bay of Fundy, these crumbling cliffs shed light on the life and environments of the Carboniferous Coal Age, 315 million years ago. The site has been a magnet for geologists since the early nineteenth century. Charles Lyell described it as the world's best coal‐bearing section and together with his colleague, William Dawson, reported amazing fossil forests and a rich terrestrial fauna. Since that golden age, the rate of new fossil discoveries has hardly diminished and in recognition of its importance, the Joggins Fossil Cliffs was awarded UNESCO World Heritage Status in 2008. Even after many years of study, it remains a tremendous thrill for us to explore this ‘classic locality’ in far‐flung Nova Scotia. Each winter storm, rock fall, and tide brings with it the tantalizing possibility of new fossils and new scientific insights. In this article we share something of our excitement for Joggins and provide an up to date field guide for those wishing to unlock its secrets.     

Biogeochemical prospecting for uranium in Nova Scotia

Ashed twigs of Picea rubens (red spruce) collected over an area of uranium mineralization in central Nova Scotia were analyzed for uranium in the course of biogeochemical prospecting for this element. Uranium levels in background samples were significantly lower than in those collected from areas with mineralization either at depth or on the surface. Scintillometric data were useful only to differentiate background and surface mineralization. Uranium levels in soils showed no correlation whatsoever with mineralization or with radiometry. There was a very high degree of correlation between the scintillometric data and uranium concentrations in ashed twigs and it is considered that twigs of Picea rubens might be successfully used for biogeochemical prospecting for uranium in this area.     

The distribution of trace metals in the western North Atlantic off Nova Scotia

The distributions of Fe, Mn, Zn, Cu, Ni, Cd and Co have been determined in a section across the Scotian Shelf into the Atlantic Slope water. Significant differences in concentration exist for most of the trace metals between the four water masses in the section. Depletions of trace metal concentration in the highly productive Atlantic Slope water relative to the underlying Central Atlantic water are thought to be due to biological activity.The distributions of Fe and Mn are strongly related to the distribution of suspended particulate matter. The concentrations of Fe and Mn, extracted from the suspended matter on the Scotian Shelf, are considerably higher than those in the non-detrital fraction of the underlying sediments. This suggests that post-depositional changes cause the loss of both elements from the non-detrital fraction of the particles. Whereas Mn shows major nearshore increases in concentration related to continental runoff, nearshore Fe concentrations are largely controlled by particulate matter distribution. Continental runoff does not appear to have much influence upon the distributions of the other trace metals.     

Low pressure cordierite-bearing migmatites from Kelly's Mountain,Nova Scotia

The Kelly's Mountain gneiss complex of Cape Breton Island, Nova Scotia, is a migmatitic paragneiss dominated by biotite- and cordierite-bearing assemblages. Metamorphic grade throughout the complex is in the upper amphibolite facies, with garnet absent and only retrograde muscovite present. In the high grade core of the complex the reaction biotite+andalusite+quartz=cordierite+K-feldspar+sillimanite+ilmenite+H₂O is preserved. The pelitic migmatites contain cordierite- and K-feldspar-rich leucosomes and biotite-rich melanosomes. Minor clinopyroxene-bearing amphibolite in the complex does not show migmatitic textures. The migmatites are interpreted as in situ peraluminous partial melts on the basis of phase relations and textural criteria. Retrograde metamorphism under conditions of high fluid pressure locally produced muscovite after K-feldspar and muscovite+green biotite+chlorite after cordierite in paragneiss, and sphene after ilmenite in amphibolite. Peak metamorphic conditions of 1–3.5 kb and 580–700° C are estimated. The high geothermal gradient inferred from these conditions was probably caused by the intrusion of diorites associated with the gneiss complex. The Kelly's Mountain complex represents a rare example of migmatites formed in the low-pressure facies series, and illustrates some of the reactions involving melting in high grade pelitic rocks.     

Magmatic andalusite from the South Mountain batholith,Nova Scotia

Accessory andalusite has been found in some late-stage granitic differentiates of the South Mountain batholith. The andalusite is petrographically distinct from the andalusite of the thermal aureole, and it occurs in regions of the batholith which show little evidence of contamination by the country rocks. Analyses of biotites from andalusite-bearing and andalusite-free phases suggest that those coexisting with andalusite actually grew in equilibrium with the andalusite. It is concluded that magmatic andalusite must be confined mainly to water-saturated, peraluminous, epizonal granites, and some possible P-T paths for the crystallization of magmatic andalusite are considered.     

Thermal maturity of the lower carboniferous Horton group, Nova Scotia

The Thermal Alteration Index (TAI) obtained from spore colouration is a useful maturity indicator that may be obtained from palynological preparations. Thermal maturity is an important parameter in determining the hydrocarbon potential of the Lower Carboniferous lacustrine and fluviatile sediments of the Horton Group, and coeval rocks, of Nova Scotia. Samples studied from fifty-two separate localities indicate a wide range in thermal maturity from low (TAI 2 to 3) to high (TAI 4 to 5?). Variation in depth of burial was probably the main factor responsible for the regional differences in thermal maturity. The thickness of Horton sedimentation varied considerably in a series of half grabens, as did the overburden of post-Tournaisian Lower Carboniferous, Upper Carboniferous, Permian and possibly Triassic rocks.The organic matter in most samples is composed of exinous (Type II) and woody and coaly material (Types III and IV). Locally in a few localities amorphous algal material (Type I) consisting of Botryococcus sp. is common. The composition of the organic matter and the thermal maturity data suggest that in most of the study area rocks of the Horton Group are in the dry gas generation zone, although in some areas oil generation may have taken place; in a few localities where the thermal maturity is high the organic matter has been altered beyond the dry gas preservation limit.     

Strontium isotope geology of the South Mountain batholith,Nova Scotia

The South Mountain batholith of southwestern Nova Scotia is a large, peraluminous, granodiorite-granite complex which intrudes mainly greenschist facies metasediments of the Cambro-Ordovician Meguma Group. Using Rb-Sr isochrons constructed from whole rocks and mineral separates, the present study shows a variation in age and initial ratios of the intrusive phases of the batholith as follows: biotite granodiorite (371.8 ± 2.2 Ma, (${}^{87}\text{Sr}{}^{86}\text{Sr}\text{)}{}_{\mathrm{i}}$ ranges from 0.7076 ± 0.0003 to 0.7090 ± 0.0003, with the average = 0.7081); adamellite (364.3 ± 1.3 Ma, $\text{(}{}^{87}\text{Sr}{}^{86}\text{Sr}\text{)}{}_{\mathrm{i}}\text{= 0.70942 ± 35}$); porphyry (361.2 ± 1.4 Ma, $\text{(}{}^{87}\text{Sr}{}^{86}\text{Sr}\text{)}{}_{\mathrm{i}}\text{= 0.71021 ± 119}$); using λ⁸⁷Rb = 1.42 × 10^?11yr^?1.A suite of Meguma country rock samples showed a variation of ${}^{87}\text{Sr}{}^{86}\text{Sr}\text{= 0.7113?0.7177}$ at the time of intrusion of the batholith. A number of xenoliths of this material occurring in the marginal granodiorite had partially equilibrated isotopically with the granodiorite at a higher ${}^{87}\text{Sr}{}^{86}\text{Sr}$ ratio than elsewhere in the granodiorites. This evidence demonstrates that isotopic (and probably some accompanying bulk chemical) contamination by the Meguma rocks has been an important factor in determining the ultimate chemical composition and mineralogy of the South Mountain batholith.The $\text{(}{}^{87}\text{Sr}{}^{86}\text{Sr}\text{)}{}_{372}\text{= 0.7081}$ of the early granodiorites indicates that the parent magma of the South Mountain batholith was derived from a source unlike the Meguma Group. The precise nature of the source region cannot be determined by Rb-Sr work unless the degree of contamination with Megumalike material is known.     

海南岛西部戈枕含金剪切带及其金矿成矿系列

古生代以来，海南西部戈沈含金剪切带至少经历了三次类型不同的构造变形，并发生了三次相关的金矿化。该剪切带的构造变形，在加里东旋回发生于抱板群矿源层下构造层次，表现为韧性剪切，其晚期形成含金长英质脉；在海西－印支旋回发生于中构造层次，表现为韧－脆性变形，形成糜棱岩型和石英脉型金矿床。     

Wisconsinan Late-glacial environmental change in Nova Scotia: A regional synthesis

A synthesis of the interpreted vegetational and climatic history of Nova Scotia during the Wisconsinan Late-glacial period (14-9 ka BP) is presented and described in 500-year intervals. The concomitant regional deglaciation history of the region is also described. A synthesis chart is provided which includes a qualitative curve of temperature reconstructions for the Lateglacial period.     

Feature: UNESCO World Heritage and the Joggins cliffs of Nova Scotia

UNESCO World Heritage status is the highest honour that may be bestowed on a palaeontological site. In addition to heightening conservation status, it confers international recognition of a locality's 'outstanding universal value' and often triggers the release of substantial regional development funds. Despite these incentives it is, perhaps, not surprising that only a handful of fossil sites have successfully navigated the World Heritage selection process. In this feature, we draw on our recent experience of developing a World Heritage bid for the Pennsylvanian 'Coal Age' locality of Joggins, Nova Scotia. As well as demonstrating the huge significance of Joggins, we hope that our findings will provide valuable guidelines for the assessment of World Heritage fossil sites in general.     

Geochemistry of the tonalitic and granitic rocks of the Nova Scotia southern plutons

In southern Nova Scotia, tonalite, trondhjemite, granodiorite and granite intruded metasedimentary rocks of the Appalachian belt during the Acadian orogeny. The mineral assemblages of these metasedimentary rocks define the staurolite-in (or staurolite + cordierite-in) isograd of the amphibolite facies of the low-pressure, intermediate-type of regional metamorphism.The chemical compositions of these tonalitic to granitic rocks indicate that the magmas before and possibly during crystallization were under relatively high pressures (3.5–6.5 kbar) and at temperatures above ‘minimum melt’ temperatures, possibly in the range 670–730°C, with exception of the tonalitic magma for which a higher temperature of formation is required.These rocks show many geochemical affinities such as relatively high Na/K ratios and similar K/Rb ratios and REE abundances. The REE patterns are moderately fractionated, with a negative Eu anomaly.An origin by partial melting of the metasedimentary rocks of the orogenic belt is postulated for these rocks in the light of the geochemical evidence. This hypothesis has been tested by application of a quantitative model of equilibrium between granitic melts and probable residual material.     

Environmental status of several Shubenacadie River headwater lakes,Nova Scotia,Canada

The Shubenacadie River basin is the largest watershed in Nova Scotia, Canada, encompassing an area of approximately 2,800 km² and supporting one of the most rapidly expanding populations in Atlantic Canada. A comprehensive study was carried out to assess the effect of recent development in the basin on the headwater lakes. Information on the environmental status of the lakes can be further used in the development of a management framework for the basin with respect to water quality and quantity objectives.Water and sediment quality were investigated in four of the Shubenacadie River headwater lakes. In addition, trophic status of the lakes was assessed by using dissolved phosphorus and oxygen concentrations. The surface area and mean depth of the lakes ranged from 0.83 to 1.13 km² and 4.3 to 6.6 m, respectively. Three of the studied lakes were thermally stratified during the summer. The concentration of dissolved oxygen decreased significantly in the hypolimnion during the stratification period, although the lakes were generally classified as oligotrophic. The water quality is typical for lakes of the area. The pH of the water ranged between 6.1 and 7.3 during the study period. Major ions were chloride, sodium, and sulphate. A significant increase of As, Hg, Zn, Pb, Cu, Ni and Co was found in surface sediments in all four lakes. However, the concentration of these elements in lake water was lower than recommended guidelines for aquatic life and human consumption.     

Leucogranites from the Eastern Part of the South Mountain Batholith, Nova Scotia

The South Mountain Batholith is a peraluminous granitic complexranging in composition from biotite granodiorite to muscovite-topaz‘leucogranite’. Leucogranitic rocks (with generally<2% biotite) form a minor part ({small tilde}1•5%) ofthe batholith, and are of two types: (1) ‘associated leucogranites’occurring as relatively small zones in fine-grained leucomonzogranites;and (2) ‘independent leucogranites’ forming generallylarger bodies having no particular spatial association withother rock types. Mean chemical compositions of these two typesof leucogranite are as follows (associated, independent): Na₂O(3•46,3•83),K₂O(4•40,4•09),andP₂O₅ (0•26, 0•45)in wt.%;Li(149, 281), F(1199, 2712),Rb (393, 725), U (7•4, 4•4), Nb (12•8, 23•4),Ta (2•9, 7•1), and Zr (52, 31) in ppm. Rare earthelements also differ between the two types (associated, independent):REE (34•1 ppm, 19•9 ppm); and in the degree and variabilityof heavy REE fractionation (Gd_N/Yb_N=4•62•2, 2•00•7).In addition, associated leucogranite has REE compositions similarto those of its host rocks. Mean ¹⁸O values (associated +ll•21•2,independent +ll•40•5; relative to SMOW) are comparablewith the mean for the entire South Mountain Batholith (+l0•80•7).Radiometric dating (⁴⁰Ar/³⁹Ar on muscovite) shows that bothtypes of leucogranite have identical ages of 3723 Ma, equivalentto ages determined by other techniques for granodiorite andmonzogranite samples elsewhere in the batholith. Field relationsand geochemistry suggest that the associated leucogranite resultsfrom an open-system interaction between a fluid and its hostleucomonzogranite, whereas the independent leucogranite bodiesare discrete intrusions of highly fractionated melts that underwentclosed-system, late-magmatic to post-magmatic fluid alteration.Where mineralized, the associated leucogranite characteristicallyhosts greisen-type or disseminated polymetallic mineralization,whereas the independent leucogranite hosts pegmatitic or disseminatedpolymetallic mineralization.     

An investigation of cathodoluminescence in albite from the A-type Georgeville granite,Nova Scotia

Cathodoluminescence (CL) reveals red and blue colors within single, non-turbid albite (Ab_98–99) grains from the Georgeville granite, Nova Scotia. A 720 nm X-ray excited optical luminescence (XEOL) peak characterizes red CL regions, while a 280 nm XEOL feature dominates blue CL regions. Synchrotron X-ray fluorescence results indicate that red CL and the 720 nm XEOL peak intensities relate to total Fe concentrations. The relationship between red CL and Fe content is confirmed by electron microprobe (EMPA) and laser ablation-inductively coupled mass spectrometry (LA-ICP-MS). The XEOL technique is used to exclude the Fe K-edge as the cause of red CL. X-ray absorption spectroscopy results indicate that Fe in both the red and blue CL regions is Fe³⁺, and that red CL activation may relate to the Si–Al order of the feldspar and to the distribution of Fe on tetrahedral sites. The CL textures, combined with EMPA and LA-ICPMS analyses, indicate that blue CL albite (Ab₉₈) regions contain higher concentrations of Ca, Ti, Pb and rare earth elements, and were replaced, in part, by a more Fe-rich, trace element depleted albite (Ab₉₉) which displays red CL. Complex diffraction contrasts and amorphous deposits identified in transmission electron microscope images suggest that aqueous fluids have reacted with both red and blue CL regions. Fluid inclusion homogenization temperatures of up to 430 °C provide a lower estimate of the fluid temperature.     

Tin-bearing potential of some Devonian granitic rocks in S.W. Nova Scotia

Petrological indices and major element chemistry may be used to select individual plutons within a batholith which are most likely to be tin bearing. The origin and evolution of only the selected individual plutons may be assessed using trace elemental contents and dispersions, (Rb, Ba, Pb, Zn, Mo, Li, Be, F, and W) and selected elemental ratios, K/Na, Ba/Rb, (Li × 1000)/K, Li/Zn, and F/Li. This information may also be used to assess the ore bearing potential of the plutons. The method has been applied to three plutons within the South Mountain Batholith of Nova Scotia, using 75 whole rock major and trace element analyses. The results suggest that only the New Ross Pluton, in which several tin prospects are known, might be ore bearing. All the plutons are considered to be deeply eroded and any economic cassiterite deposits have probably been removed by erosion.     

Microstructure, metamorphism and tectonics of the western Cape Breton Highlands, Nova Scotia

ABSTRACT Microstructural and petrological data from the Jumping Brook metamorphic suite, western Cape Breton Highlands, suggest that a single episode of syntectonic prograde metamorphism, followed by uplift, cooling and associated retrogression, affected these rocks during mid-Palaeozoic times. Microstructures indicative of progressive crenulation foliation development can be traced from low-grade (chlorite zone) through high-grade (kyanite zone) rocks, allowing a clear sequence of porphyroblast growth to be established. Metamorphic reactions and P-T calculations suggest metamorphic conditions of 700-750°C at 8-10 kbar were achieved in kyanite zone rocks. Although a complete P-T-t path was not defined, combined petrological and geochronological data can be used to constrain computed P-T-t models. These models suggest that a component of post-metamorphic tectonic exhumation is required to explain the observed times of cooling and uplift. The microstructural and petrological data to not support the interpretation that the high-grade rocks represent pre-existing crystalline basement. Indeed, the metamorphic history, geochronology and computed tectonic models all point to a single, short-lived episode of Silurian-Devonian volcanism, intrusion, convergence, regional metamorphism and uplift, probably resulting from collision tectonics at an irregular continental margin.     

Thermoluminescence dating of St. Croix ceramics: Chronology building in Southwestern Nova Scotia

Using the classic thermoluminescence (TL) dating technique for fired ceramic materials, we have obtained the first direct ages for five ceramic artifacts recovered from BfDa-1, a prehistoric archaeological site located in St. Croix, southcentral Nova Scotia. BfDa-1 is the only archaeological site in Nova Scotia to produce the full range of ceramic styles associated with the Woodland or Ceramic Period (c. 1050 B.C. to A.D. 1500); thus our new chronology can be used to revise the current local and regional ceramic chronologies. The five sherds from the St. Croix site yielded absolute gas of 1.15 ± 0.15 ka to 2.62 ± 0.29 ka (1 ka = 1000 years). The oldest of these TL ages was obtained on a sherd decorated with a pseudoscallop shell design and is in excellent agreement with a ¹⁴C date of 2500 ± 120 B.P. associated with Early Ceramic artifacts at this site. The other TL ages are in agreement with the relative ceramic chronology deduced from their decorative attributes. All five TL dates are in the correct depth-age order. This demonstrates that the recent excavations explored a part of the site which remained undisturbed in spite of extensive agricultural and horticultural activities in the vicinity in recent centuries. The dates also indicate a high degree of compression for the cultural remains at the site. They suggest a sediment deposition rate of 1.3 cm/100 yr during the early stages of the occupation period (2000–2600 yr B.P.), and a decrease in the deposition rate to 0.5 cm/100 yr during the last 2000 years. These dates provide the first successful application of TL dating to ceramics of the Minas Basin area. They confirm an initial hypothesis based on the stylistic attributes of ceramics recovered from BfDa-1, that human occupation at the site must have been of long duration. The excellent quality of the analytical data indicates that the TL dating technique should be well suited to the study of ceramic technology in other parts of the province, and that local mineralogy is suitable for optical dating of sediments at the site and elsewhere in Nova Scotia. © 1997 John Wiley & Sons, Inc.