late silurian volcanism in coastal maine the cranberry island series the cranberry island series is a silurian 424 1 ma volcanic succession that crops out on three islands along the southeastern coast of maine it is part of the coastal maine magmatic province and represents bimodal magmatism that occurred on a composite crustal block before or during accretion to laurentia the series consists of 1 8 km of felsic pyroclastic rocks and felsic lava flows overlain by 0 8 km of basaltic tuffs and basaltic lava flows the lower and upper members of the cranberry island series are interpreted respectively as 1 felsic pyroclastic rocks and lavas erupted from a mingled felsic and mafic magma reservoir and 2 phreatomagmatic basaltic rocks overlain by effusive basaltic flows some of the basaltic inclusions hosted by the felsic pyroclastic rocks may be chilled magmatic enclaves suggesting that droplets of basaltic magma were entrained by felsic magma prior to eruption the compositionally layered plutons of the cadillac mountain intrusive complex to the north are likely candidates in both age and composition for the magma bodies from which the cranberry island series erupted mafic rocks of the cranberry island series do not show the enrichment in large ion lithophile elements and the depletion in high field strength elements diagnostic of subduction related magmas the bimodal character of magmatism the lack of strong arc geochemical signature and the rarity of andesites in the cranberry island series and throughout the coastal maine volcanic belt argue against an origin in a compressional setting alternative settings for magmatism include 1 backarc extension 2 crustal extension associated with large scale transcurrent faulting and 3 extension related magmatism associated with rifting of the coastal maine volcanic belt from another continental margin

silurian orogenesis in the western penobscot bay region maine new 40ar 39ar mineral ages from rocks collected west of penobscot bay maine indicate this region was regionally deformed metamorphosed to amphibolite facies conditions and intruded by plutons in silurian times rather than in the devonian as previously assumed disturbed hornblende age spectra along with the presence of some devonian felsic plutons and extensive retrograde metamorphic textures do suggest however that these rocks were subsequently affected by low grade devonian thermal events in sharp contrast rocks west of the sennebec pond thrust fault a major tectono stratigraphic boundary in this region lack a significant silurian tectono thermal signature and instead record the effects of intense devonian deformation and high grade regional metamorphism the data suggest the two regions experienced very different pre devonian histories and were most likely juxtaposed by the sennebec pond thrust fault in latest silurian to early devonian time rocks now exposed east of the sennebec pond faul

model for the precambrian evolution of the avalon terrane in southern new brunswick canada the tectonostratigraphic record of the avalon terrane in southern new brunswick is interpreted as that of a wilson cycle that followed the grenvillian and preceded the opening of lapetus development of a late precambrian continental shelf is attributed to the cadomian ocean whose initial subduction at 800 ma led to platform collapse regional metamorphism and minor mafic to ultramafic plutonism in response to back arc extension and crustal separation oblique subduction of the resulting back arc basin at 600 630 ma produced calcalkaline plutonism and cogenetic volcanism that ended in dextral transtension and the emplacement of a bimodal dike complex initial rifting of lapetus which isolated this record from cratonic north america is recorded in eocambrian redbeds and bimodal volcanics and produced a cambro ordovician overlap sequence bearing acado baltic fauna

petrology age and tectonic setting of the white rock formation meguma terrane nova scotia evidence for silurian continental rifting the white rock formation in the yarmouth area of the meguma terrane of southern nova scotia consists mainly of mafic tuffaceous rocks with less abundant mafic flows epiclastic and clastic sedimentary rocks and minor intermediate and felsic crystal tuff it is divided into seven map units that appear to young from west to east inconsistent with a previously assumed synclinal structure the white rock formation is flanked on both northwest and southeast by mainly the cambrian to lower ordovician halifax formation the western contact is interpreted to be a sheared disconformity whereas the eastern contact appears to be a major brittle fault and shear zone that juxtaposes different crustal levels the granitic brenton pluton forms a faulted lens within the eastern shear zone a felsic tuff from the upper part of the white rock formation yielded a u pb zircon age of 438 3 2 ma identical within error to published ages for the brenton pluton and felsic volcanic rocks near the base of the white rock formati

geochemical and isotopic characteristics of granitoids of the avalon zone southern new brunswick possible evidence for repeated delamination events nd o and pb isotope data from southern new brunswick suggest that 625 to 360 ma granitoid plutons contain a major juvenile component and small amounts of middle proterozoic or older crustal material plutons fall into four major age groups 600 630 540 560 422 430 and 367 396 ma the first and third groups can be related to subduction in other parts of the appalachian orogen but most of the second and fourth magmatic pulses have lithologic associations and chemistry not readily reconciled to subduction the timing and volume of magmatism presence of mafic end members and juvenile signatures in the plutons suggest that crustal delamination may have been involved little evidence exists for extensive middle proterozoic or older continental crust beneath the avalon zone which consists mainly of late proterozoic continental margin arc material intruded by younger granitoid plutons that include a major mantle component this differs from contiguous gander and meguma zones in which plutons contain a ma

the position and nature of the gander avalon boundary southern new brunswick based on geochemical and isotopic data from granitoid rocks in southern new brunswick the gander avalon boundary is obscured by boundary parallel faults and various cover sequences siluro devonian granites which intrude unequivocal gander or avalon rocks display exclusively negative 1 9 1 0 and positive 1 9 0 7 end t signatures respectively such contrasting nd isotopic signatures combined with other geochemical differences between plutons are potentially valuable tools for terrane analysis nine small devonian plutons intruding the boundary zone fall into contrasting geochemical groups with la lu n 4 the former are topaz bearing granites while the latter are volcanic arc type granites except for one pluton with an end t signature of 2 0 end t values range from 0 4 to 0 7 spanning the gap between type avalon and type gander plutons these results suggest the plutons sampled either i stratigraphically overlapping or tectonically interleaved gander and avalon basement rocks or ii a distinct basement source beneath the b

the kingston terrane southern new brunswick canada evidence for an early silurian volcanic arc the fault bounded kingston terrane of southern new brunswick consists of felsic and less abundant mafic volcaniclastic rocks and flows and minor interbedded sedimentary rocks of the kingston group intruded by mainly granitic plutons and abundant younger mafic sheets the granitic plutons form about half of the terrane and are characterized by fine grain size and typically granophyric and porphyritic textures indicative of high level emplacement mafic sheets were emplaced in the granitic plutons and parallel to primary layering in the kingston group which is typically steeply dipping and trends northeast to north northeast hence in contrast to some earlier interpretations the kingston terrane does not consist of a bimodal dike complex the kingston group granitic rocks and mafic sheets contain mineral assemblages consistent with metamorphism to upper greenschist lower amphibolite facies new u pb zircon ages of 442 6 ma from a dacitic tuff unit and 437 10 ma from a granitic pluton corroborate previous u pb dates that had suggested that the volcanic and granitic rocks in the kingston terrane are early silurian rather than precambrian as had been earlier assumed the felsic volcanic and granitic rocks are interpreted to be comagmatic on the basis of their field relationships and similar u pb ages and chemical character compositions of both the felsic rocks and less abundant mafic and intermediate and mafic rocks are consistent with calc alkalic affinity and emplacement in a continental margin volcanic arc herein termed the kingston arc a u pb date of 435 5 ma was also obtained from compositionally similar granite that forms a dike in an adjacent fault bounded amphibolite facies metasedimentary unit the similarity in age and composition of the granite dike suggests a link between these metasedimentary rocks and the kingston terrane possibly as part of an accretionary complex if so its location southeast of the kingston terrane indicates that subduction was to the present northwest mafic sheets in the kingston terrane are tholeiitic but have some arc like characteristics consistent with their origin in a former arc setting but the sheets were likely emplaced in a subsequent extensional setting the compositional similarity of the mafic sheets to late silurian mafic volcanic rocks and plutons of the coastal maine magmatic province suggests that they may be related a possible model for evolution of the kingston terrane is proposed wherein the kingston group and related granite formed in an early silurian arc on the margin of ganderia as represented by the new river terrane of late precambrian and early paleozoic age northwestward subduction culminated in collision between the kingston arc and a continental block now represented by the brookville terrane to the southeast subsequent transpressive mo tions in the late silurian may have been responsible for the crustal scale extensional environment in which the coastal maine magmatic province was formed including emplacement of mafic dikes into the deformed former kingston arc transpressive motions related to juxtaposition of the avalon and meguma terranes with the previously accreted more inboard terranes continued through the devonian and into the carboniferous

superposed neoproterozoic and silurian magmatic arcs in central cape breton island canada geochemical and geochronological constraints isotopic and geochemical data indicate that intrusions in the eastern creignish hills of central cape breton island canada represent the roots of arcs active at 540 585 ma and 440 ma times of intrusion are closely dated by 1 a nearly concordant u pb zircon age of 553 2 ma in diorites of the creignish hills pluton 2 a lower intercept u pb zircon age of 540 3 ma that is within analytical error of 40 ar 39 ar hornblende plateau isotope correlation ages of 545 and 550 7 ma in the river denys diorite and 3 an upper intercept u pb zircon age of 586 2 ma in the melford granitic stock on the other hand 441 455 ma 40 ar 39 ar muscovite plateau ages in the host rock adjacent to the skye mountain granite provide the best estimate of the time of intrusion and are consistent with the presence of granitic dykes cutting the skye mountain gabbro diorite previously dated at 438 2 ma all the intrusions are calc alkaline the skye mountain granite is peraluminous trace element abundances and nb and ti depletions of the intrusive rocks are characteristic of subduction related rocks the 540 585 ma intrusions form part of an extensive belt running across central cape breton island and represent the youngest neoproterozoic arc magmas in this part of avalonia nearby they are overlain by middle cambrian units containing rift related volcanic rocks which bracket the transition from convergence to extension between 540 and 505 520 ma this transition varies along the avalon arc 590 ma in southern new england 560 538 ma in southern new brunswick and 570 ma in eastern newfoundland the bi directional diachronism in this transition is attributed to northwestward subduction of two mid ocean ridges bordering an oceanic plate and the migration of two ridge trench transform triple points following complete subduction of the ridges remnant mantle upwelling along the subducted ridges produced uplift gravitational collapse and the high temperature low pressure metamorphism in the arc in both southern new brunswick and central cape breton island the 440 ma arc magmatism in the creignish hills extends through the cape breton highlands and into southern newfoundland and has recently been attributed to northwesterly subduction along the northern margin of the rheic ocean

440 ma igneous activity in the meguma terrane nova scotia canada part of the appalachian overstep sequence abraded zircons from the basal rhyolitic tuff member of the white rock formation which disconformably overlies the cambrian early ordovician meguma group have yielded a nearly concordant u pb age of 442 or 4 ma interpreted as the age of extrusion this age straddles the approximately 443 ma ordovician silurian boundary abraded zircons from the brenton granite lie on a chord with an upper intercept age of 439 4 3 ma which is interpreted to be the age of intrusion thus supporting its inferred subvolcanic nature on the other hand monazite from the brenton pluton yielded a nearly concordant analysis with a 207 pb 206 pb age of 380 or 3 ma which is interpreted to be the time of the low pressure high temperature metamorphism using these new data the following observations suggest that the meguma and avalon terranes were neighbors during the silurian early devonian 1 both have latest ordovician earliest silurian bimodal subaerial alkalic tholeiitic rift related volcanic rocks with nd signatures indicating a similar continental basement source 2 both show a similar progression of depositional environments subaerial in the earliest silurian progressively deeper water marine strata in the llandovery and wenlock switching to gradually shallowing marine environments in the ludlow and reverting to subaerial in the pragian and 3 both contain rhenish bohemian early devonian fauna furthermore the southeast to northwest transition from an offshore sandbar to a beach sand in the silurian white rock formation suggests the presence of land to the north now recognized as avalonia these conclusions support published suggestions that the siluro devonian successions in the meguma and avalon terranes form part of the overstep sequence that extends across most of the northern appalachians published data indicate that avalonia was adjacent to gondwana in the neoproterozoic that it separated from gondwana in the early ordovician and was accreted to eastern laurentia in the late ordovician early silurian on the basis of the data and correlations presented here we suggest that the meguma terrane travelled with avalonia this is consistent with the absence of a phase of deformation between the cambro ordovician meguma group and the silurian white rock formation

tectonic setting and regional correlation of ordovician silurian rocks of the aspy terrane cape breton island nova scotia interlayered mafic and felsic metavolcanic rocks and metasedimentary rocks of ordovician to silurian age are characteristic of the aspy terrane of northwestern cape breton island these rocks were affected by medium to high grade metamorphism and were intruded by synkinematic granitoid orthogneisses during late silurian to early devonian times they were intruded by posttectonic devonian granitic plutons and experienced rapid devonian decompression and cooling the chemical characteristics of the mafic metavolcanic rocks indicate that they are tholeiites formed in a volcanic arc setting the volcanic rocks of the aspy terrane differ from many other silurian and silurian devonian successions in atlantic canada which have chemical and stratigraphic characteristics of volcanic rocks formed in extensional within plate settings and are somewhat younger than the aspy terrane sequences aspy terrane units are most similar to ordovician silurian volcanic and metamorphic units in southwestern newfoundland incl

u pb geochronological constraints on the timing of plutonism volcanism and sedimentation jersey channel islands uk uranium lead dates for single and small multiple grain zircon separates are presented for the main geological units from jersey british channel islands a turbiditic sandstone from the jersey shale formation brioverian supergroup contains detrital zircons of a variety of ages ranging from c 2 6 to 0 6 ga the youngest zircons yielded nearly concordant u pb dates of 586 7 3 0 ma and 587 1 2 7 ma providing a maximum depositional age for the unit zircons from overlying volcanic rocks anne port rhyolite give an upper intercept date of 582 8 3 2 7 ma considered to be the age of eruption the undeformed sw jersey granite which intrudes and locally thermally metamorphoses the folded jersey shale formation is dated at 580 2 3 1 6 ma these dates constrain tightly the timing of deposition of the jersey shale formation and the age of deformation on jersey and indicate a dynamic arc environment during the late neoproterozoic zircons from the nw jersey granite define an upper intercept date of 482 7 1 6 ma similar to the previously reported 40 ar 39 ar hornblende date of c 473 ma confirming a renewed pulse of magmatism during the ordovician in this sector of cadomia

geological correlations between cape breton island and newfoundland northern appalachian orogen geological correlations between cape breton island and newfoundland are apparent both in surface geology and at deeper crustal levels based on similarities in sm nd isotopic signatures the mira terrane of southeastern cape breton island is part of the avalon terrane sensu stricto and is composed of neoproterozoic volcanic sedimentary plutonic belts and overlying cambrian rocks directly comparable to those in the western part of the newfoundland avalon terrane the bras d or terrane is also mainly of neoproterozoic age but shows lithological and isotopic contrasts with the mira terrane small areas of similar neoproterozoic rocks occur in southern newfoundland and to the north as inliers in the exploits terrane the bras d or terrane and similar rocks in newfoundland are interpreted to represent a peri gondwanan terrane where rocks of the gander terrane were later formed hence this area is part of the central mobile belt and distinct from avalon terrane sensu stricto the aspy terrane is a complex area

measurements of transient ground movements below a ballasted railway line this paper presents the results of a detailed investigation into the ground deformations that occur under a railway line during the passage of a train four horizontal boreholes were installed at different depths below a ballasted railway track ground deformations were measured using geophones at set distances from the centreline of the track within each borehole the results show vertical displacements reducing with depth from a maximum at the sleeper sleeper displacements are dominated by pairs of bogies at the ends of adjacent wagons which have a frequency of loading 1 hz although the effects of individual bogies 2 hz and axles 6 hz are also apparent higher loading frequencies attenuate with depth so that at a depth of 0 780 m below the sleeper soffit no axles are visible within the displacement data and by a depth of 1 98 m only the combined effect of pairs of adjacent bogies is apparent in contrast longitudinal horizontal motion is greatest at a depth of 0 78 m below the sleeper soffit

u pb geochronological constraints on precambrian stratified units in the avalon composite terrane of nova scotia canada tectonic implications concordant u pb ages of detrital zircons in several proterozoic units in the avalon composite terrane of nova scotia along with previously published data indicate that deposition of low and high grade stratified units in the cobequid highlands gamble brook formation and central cape breton island variously assigned to the george river group or george river metamorphic suite and the bras d or gneiss started after 977 ma extended through a period of volcanic activity between 694 and 637 ma and ended before the 629 612 600 ma volcanic activity associated with deposition of the georgeville and jeffers groups in the antigonish and cobequid highlands and the east bay hills and coxheath groups in southern cape breton island these age data along with u pb analyses of metamorphic and igneous zircon and monazite also constrain three late proterozoic tectonothermal events i oblique sinistral ductile shear deformation and greenschist amphibolite facies metamorphism probably occurred between 694 an

40 ar 39 ar amphibole ages from the kingston complex new brunswick evidence for silurian devonian tectonothermal activity and implications for the accretion of the avalon composite terrane the kingston complex of southern new brunswick canada is a regional ne trending belt of mafic and felsic dikes bordered by dextral ductile shear zones the complex separates two contrasting late precambrian early paleozoic tectonostratigraphic assemblages near the nw margin of the avalon composite terrane rhyolitic dikes within the complex record an early silurian crystallization age dike orientations suggest that emplacement of the complex accompanied sinistral movement interpreted to reflect accretion of the avalon composite terrane to cratonic north america mafic dikes within the complex display greenschist to epidote amphibolite facies metamorphic assemblages that developed during dextral transpression amphibole concentrates from seven metamorphosed mafic dikes record late silurian to early devonian ca 416 390 ma 36 ar 40 ar vs 39 ar 40 ar isotope correlation ages interpreted to date closely the dextral transpressive deformation together with other recent age data the 40 a

geometry and kinematics of a major crustal shear zone segment in the appalachians of southern new brunswick in southern new brunswick the kennebecasis fault follows the northern boundary of a crystalline portion of the late precambrian cambrian avalon terrane this low grade crystalline complex forms the basement to a series of carboniferous through triassic basins this complex also contains a major shear zone relic that is largely flat lying but upturned adjacent to the fault and that with it defines the pocologan kennebecasis fault zone the orientation of the main composite foliation s1 and the included mineral stretching lineation l1 indicate that this geometry is a primary feature of the shear zone representing a linked pair of horizontal and vertical detachments bounding an allochthonous unit kinematic indicators show that this allochthon moved parallel to the strike of the north appalachian orogen with top towards the west or west southwest the bounding shear zone is not uniform but consists of a mylonite phyllonite adjacent to the detachment the upturned segment of the shear zone has bee

interannual to decadal changes in the western boundary circulation in the atlantic at 11 s the western boundary current system off brazil is a key region for diagnosing variations of the atlantic meridional overturning circulation amoc and the southern subtropical cell in july 2013 a mooring array was installed off the coast at 11 s similar to an array installed between 2000 and 2004 at the same location here we present results from two research cruises and the first 10 5 months of moored observations in comparison to the observations a decade ago average transports of the north brazil undercurrent and the deep western boundary current dwbc have not changed between the observational periods dwbc eddies that are predicted to disappear with a weakening amoc are still present upper layer changes in salinity and oxygen within the last decade are consistent with an increased agulhas leakage while at depths water mass changes are likely related to changes in the north atlantic as well as tropical circulation changes

geochemistry of late proterozoic basaltic rocks from southeastern new brunswick canada late proterozoic volcanic rocks of the coldbrook group 630 600 ma from the avalon zone of the appalachians in southeastern new brunswick canada are predominantly bimodal and occur in three belts fault blocks eastern central and western the basaltic rocks were emplaced in a convergent plate margin setting and range from incompatible element depleted island arc tholeiites in the eastern belt to calc alkalic types of the western belt the distinct compositional zonation of the basaltic rocks resembles the across arc variation observed in recent volcanic arc systems the trends include an increase of the lile and hfse abundances and the zr sio2 th sio2 la yb th nb th hf and zr y ratios from the eastern belt in the southeast through the central belt to the western belt in the northwest the zonation of the coldbrook group is attributed to a northwest dipping subduction zone during late proterozoic time it is suggested that some of the late proterozoic basins in the avalon zone of the northern appalachians reached a stage of oceanization

palaeozoic within plate volcanic rocks in nova scotia canada reinterpreted isotopic constraints on magmatic source and palaeocontinental reconstructions palaeozoic volcanism in the avalon terrane of northern nova scotia occurred during three time intervals cambrian early ordovician late ordovician early silurian and middle late devonian in the meguma terrane of southern nova scotia palaeozoic volcanism is limited to the middle ordovician geochemical data show that most of these volcanic rocks are bimodal within plate suites initial e nd signa tures range from 5 4 to 1 9 in the rhyolites and 6 8 to 2 7 in the basalts a difference attributable to the absence or presence respectively of a significant crustal component the data and regional tectonic settings of the avalon and meguma terranes suggest that the volcanism was generated in three different within plate settings 1 cambrian early ordovician volcanism related to thermal decay of late proterozoic arc magma tism during transtensional deformation 2 middle ordovician early silurian volcanism during sinistral tele scoping between laurentia and gondwana where extensional bends in the appalachians produced rifting and 3 devonian volcanism resulting from lithospheric delamination during dextral transpression and tele scoping in each setting active faults served as conduits for the magmas nd isotopic data indicate that the source of the palaeozoic felsic volcanic rocks is isotopically indistinguishable beneath southern and northern nova scotia and did not substantially change with time this crustal source appears to have separated from the mantle during the proterozoic a conclusion consistent with the hypothesis that the palaeozoic rocks in nova scotia were deposited upon a late proterozoic oceanic cratonic volcanic arc terrane the nd data when combined with published faunal palaeomagnetic and u pb isotopic data suggest that the avalon terrane was peripheral to gondwana off northwestern south america during neoproterozoic and early palaeozoic times

evidence for silurian sinistral accretion of avalon composite terrane in canada the kingston dyke complex forms a regionally developed belt of sheeted bimodal dykes within the avalon composite terrane of southern new brunswick canada dyke orientation relative to the belt suggests their injection accompanied sinistral movement and the belt has previously been attributed to transform activity within the late precambrian magmatic arc regime typical of the avalon composite terrane in the northern appalachians however rhyolite dykes of the sheeted complex yield a u pb age of 435 5 1 5 ma that is interpreted to date their emplacement the complex therefore provides evidence of early silurian sinistral displacement in the northern appalachians such movement is suggested by palaeomagnetic data and may record the accretion of the avalon composite terrane to cratonic north america

the massabesic gneiss complex new hampshire a study of a portion of the avalon terrane geochemical data from the 625 ma massabesic gneiss complex of southern new hampshire show strong affinities for other avalonian rocks of southern new england and suggest continental rifting in the late proterozoic migmatized paragneiss the dominant rock type in the complex has major and trace element compositions that are compatible with graywackes from continental arcs the para gneiss also has strong lithologic metamorphic and isotopic similarities to the rocks of the hope valley zone of connecticut avalon suggesting a possible hope valley massabesic correlation at 625 ma the paragneiss end values are similar to avalonian crust in other locations of the orogen two types of amphibolite are present in minor amounts in the paragneiss of the massabesic gneiss complex the first type is a paramphibolite and consists of calc silicate layers in the massabesic paragneiss the second type is metaigneous major and trace element abundances reveal that the protoliths of the orthoamphibolites range from continental rift alkaline basalts and tholeiites to n type morbs orthoam phibolite end 625 ma values range from 2 4 to 4 as expected of rift related magmas derived from partial melting of a depleted mantle source and have the same values as iapetus ocean floor rocks of similar age orthoamphibolite major and trace element geochemical characteristics overlap those of the middlesex fells amphibolites of the esmond dedham zone of eastern massachusetts avalon which range from alkaline to transitional basalts erupted in a continental rift setting the compositions of orthoam phibolites define a potential magmatic continuum produced by batch partial melting of the mantle initiated during continental rifting and proceeded to ocean basin forma tion the inferred continuity of mafic magmatism from the esmond dedham mid dlesex fells formation to the massabesic gneiss complex and hope valley zone suggests that these zones are not distinct lithotectonic zones but are parts of a single landmass massachusetts avalon esmond dedham represents the continental section of avalon where the alkaline to transitional magmas of the early rifting stages are preserved according to our tectonic reconstruction the massabesic gneiss complex is the oceanward continental margin represented by volcanoclastic sediments with the morbs representing the initiation of ocean basin development the leading edge of this landmass of which the massabesic gneiss complex is the only observable remnant collided with laurentia during the acadian orogeny the inboard thicker more continental trailing edge that is platform avalon esmond dedham collided later during the alleghanian orogeny

nd isotopic characteristics of terranes within the avalon zone southern new brunswick nd isotopic data are presented for rock units in four terranes within the traditional avalon zone of southern new brunswick initial end values for igneous rocks within the caledonia terrane range from 1 6 to 4 6 whereas values for sedimentary rocks range from 8 4 to 3 6 a granite within the kingston terrane has end 438 ma 4 0 nd isotopic compositions for the kingston and caledonia terranes are similar to those of the mira terrane in cape breton island the antigonish highlands of nova scotia and plutonic rocks of eastern newfoundland each of these regions may be a dismembered part of a single terrane the avalon terrane sensu stricto initial end values for rocks from the brookville terrane range from 1 3 to 2 8 the coverdale anorthosite within the brookville terrane has a present day end value of 12 1 and a depleted mantle model age of 1 3 ga similar to mesoproterozoic anorthosites in laurentia clastic sedimentary rocks in the green head group have end 750 ma values of 2 0 and 10 9