late precambrian u pb ages for the brookville gneiss southern new brunswick tonalitic orthogneiss from the brookville gneiss in southern new brunswick has an igneous protolith age of 605 pm 3 ma based on u pb dating of zircon metamorphic titanite from the same sample gives a minimum age of 564 pm 6 ma for upper amphibolite facies metamorphism of the unit based on u pb analyses of single detrital zircons a maximum sedimentary protolith age of about 641 ma is suggested for associated paragneiss these ages indicate that the igneous protolith of the orthogneiss was at most 35 ma younger than the sedimentary rocks it intruded and that the brookville gneiss is younger than the green head group to which it was previously considered basement both orthogneiss and paragneiss in the brookville gneiss contain proterozoic and archean detrital zircon grains suggesting an old heterogeneous continental source we conclude that the brookville gneiss does not represent the basement to the avalon terrane

structural setting and age of the partridge island block southern new brunswick canada a link to the cobequid highlands of northern mainland nova scotia the partridge island block is a newly identified tectonic element in the saint john area of southern new brunswick located south of and in faulted contact with proterozoic and cambrian rocks of the ganderian brookville and avalonian caledonia terranes it includes the lorneville group and tiner point complex the lorneville group consists of interbedded volcanic and sedimentary rocks subdivided into the taylors island formation west of saint john harbour and west beach formation east of saint john harbour a sample from thin rhyolite layers interbedded with basaltic flows of the taylors island formation at sheldon point yielded a late devonian early carboniferous u pb zircon age of 358 9 6 5 ma petrological similarities indicate that all of the basaltic rocks of the taylors island and west beach formations are of similar age and formed in a continental within plate tectonic setting west of saint john harbour basaltic and sedimentary rocks of the taylors island formation are increasingly deformed and mylonitic to the south and in part tectonically interlayered with mylonitic granitoid rocks and minor metasedimentary rocks of the tiner point complex based on magnetic signatures the deformed rocks of the tiner point complex can be traced through partridge island to the eastern side of saint john harbour where together with the west beach formation they occupy a thrust sheet above a redbed sequence of the mid carboniferous balls lake formation the tiner point complex includes leucotonalite and aegirine bearing alkali feldspar granite with a type chemical affinity and early carboniferous u pb zircon ages of 353 6 5 7 and 346 4 0 7 ma respectively based on similarities in age petrological characteristics alteration iron oxide copper gold iocg type mineralization and deformation style the partridge island block is correlated with late devonian early carboniferous volcanic sedimentary plutonic rocks of the cobequid highlands in northern mainland nova scotia deformation was likely a result of dextral transpression along the cobequid chedabucto fault zone during juxtaposition of the meguma terrane

minas fault zone late paleozoic history of an intra continental orogenic transform fault in the canadian appalachians abstract the minas fault zone mfz defines the boundary between the avalon and meguma terranes in the canadian appalachians and is exposed in mainland nova scotia and southern new brunswick these terranes originated along the gondwanan margin but had accreted to laurentia by the middle devonian the surface trace of the mfz is adjacent to the southern margin of the latedevonian permian maritimes basin the late devonian late carboniferous evolution of the mfz involves several episodes of oblique dextral shear that resulted in basin formation and inversion and at various times the zone was the focus of magmatism regional fluid flow and mineralization in the late devonian early carboniferous asymmetric rifting accompanied by dextral shear produced two coeval sequences the horton group which is dominated by continental clastic strata and the fountain lake group which consists predominantly of bimodal volcanic rocks that overlie high level plutons emplaced along active shear zones the overall tectonic environment may have been dominated by dextral transtension along the southern margin of laurentia which corresponded with the northern flank of the rheic ocean a major change in the evolution of the minas fault zone occurred in the late mississippian early pennsylvanian and produced the e w chedabucto fault clockwise rotation of pre existing structures local zones of transtension and transpression as well as regional fluid flow and extensive mineralization this major change may reflect the onset of laurentia gondwana oblique collision the effects of which continued into the latest carboniferous with coeval development of flower structures and pull apart basins in zones of local transpression and transtension

structural geology of the penobsquis salt structure late bashkirian inversion tectonics in the moncton basin new brunswick eastern canada this study uses new information acquired from field mapping mineral exploration boreholes and seismic reflection profiles to constrain the structural geology deformation mechanisms and timing of the penobsquis salt structure this information is used to place the development of the salt structure into the context of the tectonic evolution of the moncton basin the penobsquis salt structure is an elongate salt wall separated from underlying rocks by a mylonitic detachment horizon it may be divided into two segments a southwestern asymmetric southeast verging structure and a northeastern strongly asymmetric to overturned southeast verging structure associated with the penobsquis fault an initial low amplitude salt anticline formed during deposition of the mabou group serpukhovian time the salt anticline was modified into a high amplitude salt wall after deposition of cumberland group sediments early bashkirian or later the sense of asymmetry of the penobsquis salt structure the presence of thrust faults within the structure the spatial association of the structure with a major reverse fault in the salt cover and the temporal association of salt movement and compressional tectonic events suggest that the salt structure developed in response to tectonic contraction during inversion of the moncton basin

reconstructing the avalon continent marginal to inner platform transition in the cambrian of southern new brunswick a west to east marginal to inner avalonian platform transition comparable to that in southeast newfoundland and southern britain is present in the cambrian of southern new brunswick the saint john caton s island hanford brook area lay on the marginal platform and its thick uppermost precambrian lower lower cambrian is unconformably overlain by trilobite bearing upper lower cambrian an inner platform remnant is preserved in the cradle brook outlier 60 km northeast of saint john in contrast to the marginal platform sequences the cradle brook outlier has a very thin lower lower cambrian and has middle lower cambrian strata bonavista group not present on the marginal platform the cradle brook lower cambrian closely resembles inner platform successions in eastern massachusetts and trinity and placentia bays southeast newfoundland a limestone with camenella baltica zone fossils on cradle brook seems to be the peritidal limestone cap of the subtrilobitic lower cambrian known in avalonian north ame

basin evolution within and adjacent to the tien shan range nw china two late palaeozoic collisions produced the ancestral tien shan range extension following the younger collision preceded a phase of thermal subsidence associated with fluvial and lacustrine sedimentation throughout the jurassic cretaceous and early tertiary this thermal subsidence was interrupted by renewed movement on palaeozoic reverse faults caused by the mesozoic collisions at the southern margin of asia the india asia collision in the early tertiary has produced widespread thrusting in the tien shan which in turn is responsible for the formation of active foreland basins at the southern and northern margins of the range and similar basins within the range itself this compression produced uplift and relief and consequent erosion gave rise to alluvial fans braidplains and ephemeral lakes in an extremely arid environment

planktic foraminiferal sedimentation and the marine calcite budget 1 the vertical flux and sedimentation rate of planktic foraminiferal tests are quantified and a global planktic foraminiferal cac0 3 budget is presented test and calcite flux rates are calculated according to the distribution of species obtained from multinet and sediment trap samples modern planktic foraminiferal population dynamics are discussed as a prerequisite for the quantification of the calcite budget highlighting the importance of ecological autecological e g reproduction and biogeochemical conditions that determine the presence or absence of species to complete the open marine particulate caco 3 inventory the contribution of coccolithophores pteropods and calcareous dinophytes is discussed based on the studied regions the global planktic foraminiferal calcite flux rate at 100 m depth amounts to 1 3 3 2 gt yr 1 equivalent to 23 56 of the total open marine caco 3 flux the preservation of tests varies on a regional and temporal scale and is affected by local hydrography and dissolution during most of the year off peak periods many tests dissolve above 700 m water depth while settling through the water column with on average only 1 3 of the initially exported caco 3 reaching the deep seafloor pulsed flux events mass dumps of fast settling particles yield a major contribution of tests to the formation of deep sea sediments on average 25 of the initially produced planktic foraminiferal test cac0 3 settles on the seafloor the total planktic foraminiferal contribution of caco 3 to global surface sediments amounts to 0 36 0 88 gt yr 1 32 80 of the total deep marine calcite budget

subsidence in late paleozoic basins in the northern appalachians during the interval between continental collision in the devonian and continental breakup in the triassic the northern appalachians became the site of a wide plate boundary zone of dominantly right lateral strike slip as is typical of intracontinental transforms tectonism was both diachronous and rapidly variable along strike through regimes of pure strike slip transpressional deformation and rapid subsidence of extensional basins up to 9 km of mainly nonmarine clastic sediments accumulated in these local depocenters which subsided episodically in two stages 1 an initial phase of stretching and thinning of the lithosphere when subsidence was rapid fault controlled and often accompanied by volcanism and 2 a subsequent phase of gradual thermal subsidence during which the depositional basins expanded to bury the earlier border faults and progressively younger sedimentary units onlapped basement the largest depocenter the magdalen basin opened as a pull apart between strike slip faults in newfoundland and new brunswick from late devonian to early carboniferous subsequent thermal subsidence affected a large area during medial and late carboniferous a phenomenon that is well recorded to the north and west where no later tectonism occurred in areas to the south and east of the basin strike slip on other faults continued into the time of thermal subsidence introducing complications such as localized transpressional deformation and rapid subsidence in smaller pull aparts

40ar 39ar ages of detrital muscovite within early paleozoic overstep sequences avalon composite terrane southern new brunswick implications for extent of late paleozoic tectonothermal overprint concentrates of coarse grained detrital muscovite from the ratcliffe brook formation lowermost cambrian display internally discordant 40ar 39ar age spectra gas fractions evolved at intermediate and high experimental temperatures record apparent ages of ca 610 620 ma these are interpreted as dating initial cooling through temperatures appropriate for intracrystalline retention of 40ar and may indicate derivation from mylonite zones developed within proximal late precambrian granitic rocks gas fractions evolved at lower experimental temperatures record patterns of spectra discordance that suggest the constituent grains experienced partial intracrystalline diffusive loss of 40ar during a late paleozoic low grade thermal overprint a muscovite concentrate from pelitic schist beneath the allochthonous latest precambrian cranberry head granite records a 40ar 39ar plateau age of 318 1 ma this is interpreted as closely dating late carboniferous thrust emplacement of the allochthon

magmatic history of the avalon terrane of southern new brunswick canada based on u pb zircon geochronology u pb zircon dates from volcanic and plutonic units confirm that igneous activity throughout the caledonian highlands of southern new brunswick occurred in two main episodes ca 620 ma and ca 560 550 ma the ca 620 ma episode is represented by mainly metatuffaceous rocks of the broad river group and associated dioritic to granitic plutons that form most of the eastern highlands igneous rocks of similar age and type have been documented in avalonian areas throughout the northern appalachian orogen and are interpreted generally to have formed during subduction at a continental margin in contrast the ca 560 550 ma igneous episode may be unique to the caledonian highlands it is represented by tuffs and bimodal flows of the coldbrook group and co genetic gabbroic and granitic plutons that occur mainly in the western highlands this voluminous magmatism may have taken place in a volcanic arc and intra arc extensional setting perhaps like that represented by older but lithologically similar rocks of th

junggar turfan and alakol basins as late permian to early triassic extensional structures in a sinistral shear zone in the altaid orogenic collage central asia the junggar turfan and alakol basins in northwestern china and kazakhstan formed as late permian to early triassic extensional structures in a broad sinistral shear zone between large strike slip faults that separate two main domains of the altaid orogenic collage this extension was in response to an inferred large l000 km sinistral motion of the east european craton with respect to the angaran craton during this time deformation associated with the formation of the basins was taken up in part by counter clockwise rotations of crustal blocks with respect to the altaid orogenic collage and to the angaran craton this event is the only important phase of extension in a region otherwise dominated by compressional tectonics throughout the phanerozoic the basement rocks of these basins formed by altaid subduction accretion through the latter half of the palaeozoic and the region was subsequently thrown into compression again during the mesozoic cimmeride and cenozoic alpide evolution

palaeoenvironments and palaeoecology of the early pennsylvanian lancaster formation fern ledges of saint john new brunswick canada the pennsylvanian lancaster formation fern ledges of saint john new brunswick canada contains a world famous fossil biota largely unstudied since the works of hartt dawson matthew and stopes in the mid nineteenth to early twentieth century we present new data concerning biostratigraphy taxonomy palaeoenvironments and palaeoecology megafloral assemblages suggest a mid to late langsettian age for the succession making it approximately coeval with the classic joggins formation of nearby nova scotia facies analysis suggests deposition on a tectonically influenced coastal plain whose braided channels drained into a shallow brackish gulf most of the historical fossil collections are derived from flooding surfaces formed by abrupt subsidence events along the coastline three communities are recognized phoronids crustaceans and xiphosurans lived in brackish coastal waters a lowland community of gastropods insects arachnids and myriapods inhabited coastal forests coastal vegetation was dominated by shrubby cordaitaleans and pteridosperms whereas ferns sphenopsids and lycopsids were rare an upland or dryland community discernible from allochthonous assemblages comprised forests of giant cordaitaleans archaic pteridosperms and plants of uncertain affinity

response of planktic foraminiferal size to late quaternary climate change 1 geographical size distribution within entire holocene foraminiferal assemblages is related to global environmental gradients such as temperature primary productivity and environmental variability this study demonstrates that these correlations are also recognizable in late quaternary assemblages from three locations in the south atlantic on temporal and latitudinal scales the size response to temporal paleoenvironmental changes during glacial interglacial cycles mimics the geographic holocene size variability the amplitude of size variability is directly related to the amplitude of the climatic fluctuations as shown by the stable size temperature relationship over time the documented changes in the assemblage size are caused by species replacement and intraspecific size variability the relative importance of these processes depends on the environmental setting species have been shown to reach their maximum size and abundance under certain optimum conditions and decrease in size if environmental conditions differ from these optima we confirm that late quaternary species sizes were largest at paleotemperatures identical to holocene ones

lithostratigraphy of the cambrian lower ordovician saint john group southern new brunswick the cambrian lower ordovician saint john group of the saint john area southern new brunswick has historically been subdivided into 11 formations the existing scheme is inappropriate however as many of the supposed formations particularly those of middle cambrian early ordovician age were distinguished on a biostratigraphic rather than lithostratigraphic basis we suggest the sequence can be more appropriately subdivided into seven formations each of which can be clearly and easily identified by the field geologist lower cambrian formations comprise from base to top the ratcliffe brook glen falls and hanford brook formations all of which are retained from the previous nomenclature middle cambrian strata comprise the forest hills formation to replace the fossil brook and porter road formations and upper cambrian strata the king square formation to replace the hastings cove and agnostus cove formations and silver falls formation to replace the black shale brook and narrows formations

structural and sedimentary history of the quaco head area southern new brunswick remapping of the quaco head area of southern new brunswick has revealed a more complex structure than had been previously documented the structure is dominated by two major thrust faults that dip to the south and southeast at between 35 and 45 the lower younger thrust emplaces precambrian basalts and tuffaceous siltstones coldbrook group over alluvial sediments of the boss point and tynemouth creek formations westphalian a b resting unconformably on the upper surface of the basalt is a thin layer 10 m of marine basal windsor group limestone disconformably overlain by alluvial conglomerates of inferred hopewell group age this sequence is truncated by an older southeast dipping thrust fault to the southeast of which lie hopewell conglomerates overturned towards the west and northwest the latter sequence probably forms the lower limb of a large recumbent fold folding and thrusting in the quaco head area may have begun during westphalian b times although major movement was probably post westphalian c and occurred contemporaneously with dextral strike slip movement on the minas geofracture following this alleghenian variscan deformation the area underwent deep erosion prior to the deposition of a thick sequence of triassic alluvial sediments the more southerly reverse fault was reactivated as a normal fault during a phase of late triassic or jurassic faulting along the bay of fundy that was probably related to early atlantic rifting

possible earthquake induced soft sediment faulting and remobilization in pennsylvanian alluvial strata southern new brunswick canada braided river sheetflood and playa lake sediments of the tynemouth creek formation lower pennsylvanian show superficial synsedimentary faulting and subsurface post depositional sediment remobilization a prominent palaeosol has been offset 90 cm on two faults movement on which clearly preceded deposition of the overlying beds seventeen to 25 m below this horizon large load structures upward branching siltstone intrusions and three types of sandstone dike are recognised intrusion occurred on several occasions at different depths of burial and was the result of rapid probably earthquake induced dewatering this interpretation is supported by the location of the study area only a few kilometres to the north of the cobequid chedabucto fault on which major strike slip movement occurred during the pennsylvanian

biogeography and evolution of body size in marine plankton body size is a central feature of any organism reflecting its physiology ecology and evolutionary history marine microplankton are major contributors to the particulate inorganic carbonate foraminifers and coccolithophorids and opal flux radiolaria and diatoms in the ocean and hence size changes in these organisms can influence global biogeochemical cycles this paper is discussing abiotic influences on micro and macroecological size changes among major marine plankton groups linking these to evolutionary size changes during the neogene we review the patterns and outline the causes of size changes geographically and through time in coccolithophorids foraminifers and radiolarians the main feature of the neogene size record is a dramatic size increase in foraminifers a similarly dramatic reduction in the size range of coccolithophorids and highly variable size patterns in radiolarians we argue that the observed pattern is too complex to be explained by a simple common forcing and propose that speculations on the response of oceanic biomineralisation to global warming have to consider the scales at which marine plankton evolve

suspect terranes and accretionary history of the appalachian orogen the north american connection or the grenvillian continental crust that separated from eastern north america during the initiation of the appalachian orogenic cycle is poorly defined within the present orogen a variety of terranes occur outboard of the north american miogeocline all structurally uncoupled and therefore suspect stratigraphic analysis indicates that appalachian accretion progressed from the miogeocline outward the boundaries of the earliest accreted western terranes are marked by melange and ophiolite complexes later boundaries between eastern terranes are steep mylonitic zones and brittle faults accretionary events defined by stratigraphic analysis correspond to times of major deformation plutonism and metamorphism in the history of the orogen

late paleozoic strike slip faults in maritime canada and their role in the reconfiguration of the northern appalachian orogen major late paleozoic faults many with documented strike slip motion have dissected the ordovician devonian appalachian orogen in the maritime provinces of atlantic canada activity alternated between east west faults minas trend and ne sw faults appalachian trend nw se faults canso trend were probably conjugate to minas trend faults major dextral movement on faults with appalachian trend in total between 200 and 300 km began in the late devonian this movement initiated the maritimes basin in a transtensional environment at a releasing bend formed around a promontory in the laurentian margin and thinned the crust accounting for the major subsidence of the basin appalachian trend strike slip continued in the mississippian but was accompanied by major movement on e w minas trend faults culminating around the mississippian pennsylvanian boundary juxtaposing the meguma and avalon terranes of the appalachians close to their present day configuration however strike slip continued during the pennsylvanian permian interval resulting in transpressional deformation that reactivated and inverted earlier extensional faults a final major episode of transtension mainly sinistral occurred during the mesozoic opening of the atlantic ocean restoration of movements on these faults amounting to several hundred kilometers of slip explains anomalies in the present day distribution of terranes amalgamated during early paleozoic appalachian tectonism in the restored geometry the nashoba and ellsworth terranes of ganderia are adjacent to one another and the meguma terrane lies clearly outboard of avalonia a restored post acadian paleogeography not the present day geometry of the orogen should be used as a basis for reconstructions of its earlier paleozoic history

effect of the formation of the isthmus of panama on atlantic ocean thermohaline circulation the late cenozoic closure of the seaway between the north andsouth american continents is thought to have caused extensive changes in ocean circulation and northern hemisphere climate1 2 but the timing and consequences of the emergence of the isthmus of panama which closed the seaway remain controversial1 2 3 4 5 here we present stable isotope and carbonate sand fraction records from caribbean sediments which when compared to atlantic and pacific palaeoceanographic records indicate that the closure caused a marked reorganization of ocean circulation starting 4 6 million years ago shallowing of the seaway intensified the gulf stream and introduced warm and saline water masses to high northern latitudes these changes strengthened deep water formation in the labrador sea over the next million years as indicated by an increased deep water ventilation and carbonate preservation in the caribbean sea and favoured early pliocene warming of the northern hemisphere the evaporative cooling of surface waters during north atlantic deep water formation would have introduced moisture to the northern hemisphere although the pronounced intensification of northern hemisphere glaciation between 3 1 and 2 5 million years ago substantially lagged the full development of north atlantic deep water formation we propose that the increased atmospheric moisture content was a necessary precondition for ice sheet growth which was then triggered by the incremental changes in the earth s orbital obliquity