crustal structure and surface zonation of the canadian appalachians implications of deep seismic reflection data in 1986 1181 km of marine seismic reflection data was collected to 18 20 s of two way traveltime in the gulf of st lawrence area the seismic profiles sample all major surface tectono stratigraphic zones of the canadian appalachians they complement the 1984 deep reflection survey northeast of newfoundland together the seismic profiles reveal the regional three dimensional geometry of the orogen three lower crustal blocks are distinguished on the seismic data they are referred to as the grenville central and avalon blocks from west to east the grenville block is wedge shaped in section and its subsurface edge follows the form of the appalachian structural front the grenville block abuts the central block at mid crustal to mantle depths the avalon block meets the central block at a steep junction that penetrates the entire crust consistent differences in the seismic character of the moho help identify boundaries of the deep crustal blocks the moho signature varies from uniform over extended di

hydrocarbon composition of authigenic inclusions application to elucidation of petroleum reservoir filling history abstract geochemical analysis of petroleum inclusions trapped in authigenic feldspar and quartz in the ula formation in the north sea ula oil field revealed a petroleum of markedly different composition than the oil presently in the reservoir using microthermometry and the burial history as a dating tools it is concluded that the petroleum in the k feldspar inclusions was present in the more porous and permeable parts of the ula formation as early as 45 75 my bp when the field was at a depth of about 1 0 1 5 km as compared with the current depth of 3 4 km this early petroleum which was trapped as inclusions in authigenic k feldspar shows a distinctly different distribution of tricyclic terpanes and pentacyclic triterpanes from that of the current petroleum charge in the ula formation which was derived from the mandal formation source rock in late neogene time molecular parameters show that the oil in the k feldspar inclusions is significantly less mature than the crude oil in the present reservoir the approximate 90 c temperature increase occurring after entrapment of the early petroleum in kfeldspar the field is currently at 143 c appears not to have reset the low maturity signature of the oil in the k feldspar inclusions this could suggest that the temperature in the inclusions is too low for isomerization selective thermal degradation to occur lack of catalysts or that there are other controls on the ratio of some of these parameters still parameters like the ratio of c21 to c28 triaromatic steroids and those based on dimethyl and trimethyl naphthalenes are comparatively similar in both the inclusions and in the reservoir crude the oil inclusions in authigenic quartz and albite formed from about 10 my bp burial depth 2 5 km until the present burial depth 3 4 km are interpreted as representing a palaeo petroleum charge having a composition intermediate between the oil found in k feldspar inclusions and the oil charge in the present reservoir our data suggest strongly that the petroleum trapped in the inclusions in quartz and plagioclase represents progressive dilution of the early reservoired oil now found only in k feldspar inclusions with oil from the mandal formation analysis of solution gas in these inclusions suggests that the first petroleum associated gas to arrive at the trap from the progressively maturing mandal formation had a much wetter composition than the current reservoir solution gas to explain the present comparatively drier and isotopically lighter reservoir solution gas composition the inference is made that there has been a recent during formation of k feldspar inclusions 45 75 my bp maturation of the upper jurassic mandal formation the main source rock in this region was limited possibly to the graben axis this suggests that the petroleum found in the k feldspar inclusions was most likely derived from a deeper post caledonian palaeozoic formation

exceptionally preserved soft bodied assemblage in ordovician carbonates of anticosti island eastern canada abstract a diverse benthic fauna containing exceptionally preserved soft bodied organisms is described from the new vaureal konservat lagerstatte from the upper ordovician vaureal formation katian of anticosti island canada these fossils occur as pyritic or goethitic if weathered calcitic aggregates or sediment filled voids on micritic bedding planes of a marlstone limestone alternation originated on a shallow tropical carbonate ramp many organisms are preserved in association with their traces e g burrows trails whose changing shapes indicate increasing cohesiveness of the substrate rapid burial obrution under dysoxic bottom conditions must have favoured exceptional preservation although anatomical details of the organisms are often lacking due to recrystallization members of different groups of organisms could be interpreted based on their shape and other characteristic features including those of which represent their oldest fossil record i e acoelomorpha turbellaria nemertea nematoda beside polychaeta sipuncula ostracoda and other arthropoda in parallel with molecular data which recently have changed the phylogenetic status of some clades this soft bodied fauna and their traces not only record their appearance but add to the understanding of their body plan and behaviour the new konservat lagerstatte provides important information about a diverse benthic community in the late ordovician after the great ordovician biodiversification event gobe and represents a calibration point for comparison across the late ordovician mass extinction moreover comparable fossil lagerstatten are probably more common in shallow marine carbonates than currently known but might have been simply overlooked

stratigraphie framework for the cambrian ordovician rift and passive margin successions from southern quebec to western newfoundland the taconian humber zone stretches from western newfoundland to southern quebec the early cambrian slope succession in newfoundland is found in the curling group whereas in quebec various units were deposited during that first time slice biostratigraphic data allow correlation of the curling group with the labrador group in newfoundland and with the newly time constrained slope succession in quebec the end of the rift drift transition is marked by a sea level lowstand at the end of the early cambrian the middle cambrian to latest early ordovician passive margin history recorded five cyclic sea level fluctuations three of these cycles are recorded in the shallow marine middle to late cambrian platform port au port group and slope sediments preserved in the cow head and northern head groups in newfoundland the biostratigraphic information assists correlation with cambrian passive margin units in quebec major sea level lowstands are recognized along the continental margin in early middle late camb

paleogeography and tectono sedimentary history at the margin of laurentia during silurian to earliest devonian time the gaspe belt quebec the silurian lower devonian sequence of the gaspe belt at the laurentia margin south of the quebec reentrant and st lawrence promontory was deposited during the period between the two main orogenies that created the northern appalachians the late ordovician taconian and the middle devonian acadian orogenies although this sequence is traditionally considered to have been deposited during a period of quiescence between both orogenies significant tectonic activity attributed to the salinic disturbance began during late llandoverian telychian time and persisted until the acadian orogeny this tectonic activity has profoundly influenced the composition and distribution of the silurian earliest devonian sedimentary facies the shelf and shelf edge history at the laurentia margin along the quebec reentrant st lawrence promontory is summarized according to four broad phases phase 1 is a llandoverian wenlockian regressive phase r1 related to post taconian successor basin filling that culminated with extensive carbonate platform development phase 2 is a late wenlockian ludlovian transgressive phase t1 phase 3 corresponds to a later ludlovian pridolian second regressive phase r2 phases 2 and 3 were accompanied by extensional tectonics that produced shelf faulting and block tilting on top of which block reefs and reef complexes settled and built a reef tract all the way along the gaspe temiscouata shelf phase 4 is an early devonian phase of accelerated subsidence transgression t2 affecting the northwestern part of the segment quebec reentrant area while the southeastern part st lawrence promontory area was already uplifted due to the ongoing collision between laurentia and the western margin of gondwana related terranes to the south composition and distribution of sedimentary facies were controlled by the interaction of tectonics sediment influx and sea level fluctuations construction of a post taconian pre acadian palinspastic map to plot facies has proven to be basic to obtaining a realistic picture of the paleogeography of the shelf and shelf edge of the gaspe temiscouata segment at the margin of the laurentia craton during the silurian earliest devonian time interval

bathymetric and isotopic evidence for a short lived late ordovician glaciation in a greenhouse period the end ordovician glaciation is distinct among phanerozoic glaciations in that co 2 levels were generally high yet major continental ice sheets accumulated on the gondwana supercontinent new oxygen isotopic data indicate substantial changes in sea water temperatures and ice volume coinciding with glacio eustatic changes in sea level reflecting the growth and decay of the gondwana ice cap major glaciation was apparently confined to the hirnantian and was 0 5 1 m y long rather than the 35 m y of earlier estimates carbon isotope values indicate significant changes in carbon cycling as the oceans changed from a state with warm saline bottom waters to a state with cold deep water circulation and then back again we believe that the changes in the carbon cycle effected a reduction in p co 2 levels in the oceans and atmosphere and thus promoted glaciation but were unable to sustain icehouse conditions in a greenhouse world

age and composition of the ruisseau isabelle melange along the shickshock sud fault zone constraints on the timing of melanges formation in the gaspe appalachians melanges are common in the humber and dunnage zones of the quebec appalachians humber zone melanges are spatially associated with taconian nappes and believed to be of tectonic origin dunnage zone melanges are interpreted as relicts of an ordovician accretionary prism the ruisseau isabelle melange rim in the gaspe ap palachians was first interpreted as a dunnage zone melange because of its tectonic position along the baie verte brompton line and lithological components such as dark mudstone blocks of ultramafic rocks and greenish chromite bearing sandstone the rim comprises sedimentary rock assemblages composite shale black shale and chromite bearing sandstone assemblages an exotic block a pebbly mudstone assemblage and slivers of serpentinized peridotite and metamorphic tectonite most melanges of the dunnage zone in the quebec appalachians contain partly similar rocks but their age is not well constrained recent work on the rim and cap chat melange of the humber zone and new fossil finds in the rim rock assemblages allow us to conclude that previous distinction between melanges of the dunnage and humber zones on the basis of rock type associations is not valid according to the age of the rim rock assemblages melanges in the northern gaspe appalachians continued forming after the mid caradocian later than the dunnage zone melanges of southern gaspe appalachians the juxtaposition and structural features of the rim rock assemblages result from repeated faulting along the shickshock sud fault from late ordovi cian to middle devonian

biostratigraphic paleogeographic and tectonic implications of late ordovician conodonts from the grog brook group northwestern new brunswick diverse conodont faunas recovered from the grog brook group in northwestern new brunswick indicate a late ordovician probably gamachian age the conodonts are of mixed provincial affinity including components of the north atlantic province e g hamarodus icriodella periodon and protopanderodus and taxa representing shallow e g rhipidognathus to deeper water environments e g phragmodus in the midcontinent province elements of amorphognathus ordovicicus branson and mehl numerically dominate the faunas that together with sparse representatives of gamachignathus ensifer mccracken nowlan and barnes suggest a latest ordovician age the beds from which the conodont faunas have been recovered are interpreted as distal debris flows that originated at the basin margin and brought midcontinent province conodonts down the slope to mix with indigenous north atlantic province faunas the faunas are correlative with those from the matapedia group previously thought to overlie the grog brook group and

regional metamorphism of the appalachian humber zone of gaspe peninsula 40ar 39ar evidence for crustal thickening during the taconian orogeny geochronological studies on the timing of deformation and metamorphism along the laurentian margin have shown that the ages of metamorphic events change along strike within the newfoundland southern quebec segment of the canadian appalachians the gaspe peninsula is located at mid point of the two extremities of this segment new single grain laser 40ar 39ar plateau ages solely reflect latest middle late ordovician metamorphism samples taken within the internal humber zone in the shickshock group rocks yield 40ar 39ar muscovite and hornblende ages ranging from 457 to 454 ma samples from the amphibolite du diable the metamorphic sole of the mont albert ophiolite yield 40ar 39ar muscovite and hornblende ages ranging from 459 to 457 ma ordovician ages of the internal humber zone are consistent with 40ar 39ar ages from southern quebec and are interpreted as the result of the emplacement onto the margin of both the ophiolite and its metamorphic sole

ordovician arc collision and foredeep evolution in the gaspe peninsula quebec the taconic orogeny in canada and its bearing on the grampian orogeny in scotland the middle to upper ordovician deslandes cloridorme and garin formations in the eastern gaspe peninsula quebec are some of the most extensively exposed foredeep successions along the northern appalachian portion of the taconic caledonian orogen their depositional and biostratigraphic frameworks n gracilis to c spiniferus zones approximate correlatives to the n gracilis to d clingani british zones indicate that foredeep evolution spanned c 10 ma and was essentially synchronous with the convergence and accretion of the popelogan arc to the laurentian margin during the caradoc c 458 449 ma these results when combined with metamorphic and radiometric age data synthesized from across the laurentian segments of the northern appalachian and northwestern ireland taconic caledonian orogen further substantiate that orogenesis consisted of several short lived c 10 20 ma deformational episodes confined to arenig through ashgill time c 485 440 ma this indicates that the total duration of orogeny as recorded by arc magmatism metamorphism and laurentian foredeep development spanned no more than c 45 ma in that the scottish caledonides are a consanguineous part of this orogen their tectonostratigraphic evolution i e grampian orogeny should be similar accordingly the results detailed above are geodynamically compatible with and thereby support tectonic models that define the grampian orogeny in scotland as a mostly early to mid ordovician c 480 460 ma tectonic episode of short rather than long duration

stratigraphy and tectono sedimentary evolution of the late ordovician to middle devonian gaspe belt in northern new brunswick evidence from the restigouche area the gaspe belt in the restigouche area comprises three successions separated by a late silurian salinic disconformity and an early devonian angular unconformity the lower upper ordovician to lower silurian sequence consists of siliciclastic turbidites of the boland brook and whites brook formations grog brook group overlain by calcareous turbidites of the pabos and white head formations matapedia group and slope and shelf deposits of the upsalquitch and limestone point formations lower chaleurs group above the salinic disconformity the upper chaleurs group and the dalhousie group record a transgressive regressive cycle the former comprises pridolian carbonate rocks of the west point formation and overlying pridolian to lochkovian sedimentary rocks of the indian point formation the chaleurs group is conformably overlain by lochkovian to early emsian subaerial volcanic rocks of the dalhousie group val d amour formation which is unconformably overlain by alluvial lacustrine deposits of the late emsian campbellton formation acadian orogenesis began during the emsian and is characterized by open to closed folding heterogenous cleavage development and reverse and strike slip faults the salinic orogeny is manifested in extensional block faulting within plate volcanism and uplift and deep erosion of early silurian strata early devonian high level intrusion of the matapedia group white head clasts in indian point conglomerate and thermal maturation data all indicate an extended period of late silurian early devonian uplift in parts of the restigouche area thermal maturities of west point and indian point strata are within the oil and condensate windows and suggest potential for hydrocarbons in the study area

paleogeography of the matapedia basin in the gaspe appalachians initiation of the gaspe belt successor basin the matapedia basin consists of the uppermost ordovician lowermost silurian deep water fine grained carbonate siliciclastic rocks of the honorat garin formation and matapedia groups pabos and white head formations the lower rock assemblage of the gaspe belt in the gaspe appalachians paleogeographic maps of eight time slices from the caradocian to the llandoverian are presented to better understand the tectonosedimentary evolution of the matapedia basin deposition evolved from siliciclastic garin fm to argillaceous limestones pabos fm to limestones white head fm the overall change from terrigenous garin fm to limestone facies white head fm reflects a change in the source area paleocurrent directions and composition of sandstones indicate an orogenic source area to the south for the garin formation which is believed to be the inliers of the humber and dunnage zones in the southern gaspe and new brunswick appalachians lime muds deposited by turbidity currents coming from the nor

a reevaluation of the position of the baie verte brompton line in the quebec appalachians the influence of middle devonian strike slip faulting in gaspe peninsula the baie verte brompton line bbl the surface expression of the taconian suture in the canadian appalachian orogen extends from southern quebec to the northeast end of newfoundland in the que

tempestite frequency curves a key to late ordovician and early silurian subsidence sea level change and orbital forcing in the anticosti foreland basin quebec canada following partial closure of the northern iapetus ocean along the newfoundland segment of the st lawrence promontory subsidence along the anticosti platform was influenced by residual thermal subsidence renewed tectonic loading by thrust sheets to the south and sediment loading basement subsidence calculated by removing the effects of sediment loading was between 2 and 5 cm ka in the caradocian increasing to 8 6 cm ka in the pusgillian and cautleyan and reaching a maximum of 17 7 cm ka in the rawtheyan during deposition of the princeton lake and vaureal formations a marked decline in subsidence beginning in the hirnantian and continuing into the early silurian may reflect decoupling of thrust loads to the south although a further stage of thrust loading may have occurred in the aeronian during deposition of the lower part of the jupiter formation storm frequency curves produced using tempestite abundance thickness and grain size through more than a kilometre of carbonate strata on antico

a stratigraphical and faunal revision of the ordovician silurian strata of the perce area quebec the ordovician silurian strata of the perce area are assigned to the matapedia group they occur in a southwestern monoclinal sequence unconformably overlying cambrian strata and are assigned to the pabos and white head formations the pabos formation is preponderantly a terrigenous sequence whereas the white head is preponderantly a carbonate sequence the pabos strata of this area are included in the new rouge member in which four brachiopod dominated communities are recognized the dalmanella catazyga sowerbyella and epitomyonia communities within which trilobites occur sporadically the white head formation is divided into three new limestone members and a new mudstone member the basal burmingham member has yielded a catazyga community and a sowerbyella like community the cote de la surprise member is composed of mudstones with the previously described hirnantia community the rouge burmingham and cote de la surprise members are ashgillian upper ordovician but the uppermost two members

stratigraphy of the aroostook perce anticlinorium in the gaspe peninsula quebec in quebec the aroostook perce anticlinorium exposes two stratigraphic groups the honorat and the matapedia the terrigenous units of the honorat group form the core of the anticlinorium and are overlain by the carbonate sequence of the matapedia group each group comprises two formations the honorat is herein divided into two new formations the arsenault and the garin which are defined for the first time the matapedia group includes the pabos and white head formations the pabos formation a transitional unit between the noncalcareous strata of the honorat group and the carbonate facies of the white head formation is here redefined the white head formation comprises four members these two groups represent continuous sedimentation from the late ordovician caradocian to the early silurian llandoverian the lithostratigraphy of the type areas of the honorat group honorat township region and pabos formation chandler region are fully described whereas the lithostratigraphy of the type area of

palinspastic restoration of a post taconian successor basin deformed within a transpressive regime northern appalachians restoration of transpressional orogens requires a three dimensional analysis of the strain state in order to take into account both the pure shear and simple shear components of the deformation and assess their relative contribution throughout the deformation history restoration of the post taconian successor basin the gaspe belt located within the external part of the acadian orogen in the canadian appalachians was performed by using a step by step method based on the successive removal of strain increments the pure shear component contributed 70 of the total strain during the first stages of the deformation whereas the simple shear component contributed 30 of the total strain during the last stages three retrodeformation steps are defined starting with restoration of the last deformation stage and working back to the first deformation stage the first step is to restore slip along acadian strike slip faults the second step is to restore shortening related to the horizontal extension during the acadian regional simple shear event finally the third step is to restore vertical extension related to the pure shear event by removing slip along the reverse faults unfolding and removing internal strain associated with cleavage development retrodeformation of the simple shear component of the transpressive deformation during the first two steps is performed on a horizontal view of the gaspe belt basin which contains the horizontal extension direction and which is perpendicular to the acadian nw se directed compression likewise restoration of the pure shear component is performed in vertical sections which contain the vertical extension and which are perpendicular to the acadian nw se directed compression the palinspastic map presented here is a much more appropriate base map for the basin and allows for a more realistic paleogeographic interpretation of the gaspe belt

late pleistocene human occupation of the hyperarid core in the atacama desert northern chile abstract few archeological sites in south america contain uncontroversial evidence for when the first peopling of the continent occurred largely ignored in this debate extreme environments are assumed either as barriers to this early wave of migration or without potential for past habitability here we report on a rare 12 13 ka human occupation from quebrada mani site qm12 a plantless near rainless landscape 1240 m asl and 85 km from the pacific ocean located in the hyperarid core of the atacama desert this location harbored wetlands and riparian woodlands that were fed by increased rainfall further east in the central andes during the latest pleistocene excavations at qm12 yielded a diverse cultural assemblage of lithics burned and cut bones marine gastropods pigments plant fibers and wooden artifacts alongside a prepared fireplace sixteen radiocarbon dates from site qm12 on charcoal marine shells animal dung plant remains and wood reveal that the occupation took place between 12 8 and 11 7 ka these results demonstrate that the atacama desert was not a barrier to early american settlement and dispersal and provide new clues for understanding the cultural complexity and diversity of the peopling of south america during the last glacial interglacial transition

age and correlation of the honorat group southern gaspe peninsula the honorat group of southern gaspe consists of two formations the arsenault and the garin the arsenault formation heretofore considered barren has yielded a graptolite faunule indicative of a llanvirn llandeilo age early middle ordovician suggesting a correlation with the lower mictaw group of gaspe as revised by de broucker a hiatus of indeterminate magnitude corresponding to the taconic unconformity probably separates the arsenault formation from the overlying garin formation the garin has yielded graptolites ranging from the upper climacograptus spiniferus zone to the paraclimatograptus manitoulinensis zone late middle to early late ordovician the c spiniferus zone graptolites are identical to those of the upper sequence of the cloridorme formation of northern gaspe and the blind brook formation of the munsungun anticlinorium of maine but differ somewhat from those from the upper tetagouche group of new brunswick which are closer to those from the summerford and exploits groups of no

diagenetic and low grade metamorphic terranes of gaspe peninsula related to the geological structure of the taconian and acadian orogenic belts quebec appalachians illite crystallinity ic measurements determination of the proportion of 2m mica polytypes and organic matter reflectance measurements establish regional diagenetic low grade metamorphic trends for the taconian and acadian belts of gaspe peninsula ic varies as a function of many factors besides maximum burial temperature and heating time correlation between ic and 2m illite polytypes for the fortin group and temiscouata formation suggests i that the amount of high grade detrital mica in the samples is low and ii that ic can be used with some confidence as an estimator of regional thermal maturation levels correlation of these parameters with available organic reflectance values further supports this assumption the illites of the temiscouata and western fortin groups are mostly phengitic in composition whereas in the eastern outcrop belt they are more mg and fe rich celadonitic but generally also of lower grade and lower 2m content the d 060 values for illites measured on the unorientated 2 m fraction of samples fall between 1 502 and 1 503 a range 1 500 1 504 a indicating relatively low octahedral occupancy by mg and fe between one fifth and one third of the available spaces pyrophyllite and paragonite were not detected chlorites are fe rich and ripidolitic the ic map for the acadian belt of the peninsula displays general congruence between ic contours 2200 sample points and structural trends for the 27 000 km2 area the highest grades anchimetamorphic are associated with the oldest rocks honorat and matapedia groups exposed in the cores of major anticlines anchimetamorphic grades associated with the western outcrop belt of the lower devonian fortin group require 7 8 km of subsidence to accommodate sufficient thickness of overlying younger rocks on top of 4 5 km of fortin group deep water clastics to explain the grades in terms of burial metamorphism assuming a geothermal gradient of 30 c km 1 the lowest grade diagenetic rocks occupy a large area in the northeastern part of the peninsula smaller areas in the northwestern part of the acadian belt in the centre of chaleurs bay synclinorium and in the ordovician mictaw group the contact between the taconian and acadian belt is marked by a distinct maturation discontinuity the grand pabos fault juxtaposes rocks of contrasting maturation levels matapedia group against fortin group in the west but shows no maturation offset further east in the honorat group the fault zone limiting the fortin group in the north is also associated with a major ic jump

along strike acadian structural variations in the quebec appalachians consequence of a collision along an irregular margin the quebec appalachians have been shaped by two major orogenies the middle to late ordovician taconian and the middle devonian acadian thrust faults and nappe structures characterized the taconian deformation throughout the quebec appalachians whereas structural styles pertaining to the acadian orogeny differ from southern quebec to the gaspe peninsula structural analysis of late ordovician to middle devonian supracrustal rocks shows two different acadian deformational regimes strike slip tectonics in the gaspe peninsula and thrust or dip slip tectonics in southern quebec in southern quebec acadian regional deformation produced folds which vary from upright to overturned and tight to isoclinal from the nw to the se major faults e g la guadeloupe are northwestward directed thrust faults marked by highly ductile shear zones outlined by mylonite in the gaspe peninsula structural trend is ne and major e w dextral strike slip faults transect this trend folds are open and upright inclined and tighter near the major faults where they have a clockwise rotation like the regional cleavage major faults e g grand pabos follow corridors delimiting high strain zones where the fabrics developed are indicative of a ductilebrittle regime of deformation in the temiscouata region major structural features of both southern quebec and the gaspe peninsula are recognized structures of this region consist of ene trending dextral strike slip faults and high angle wnw verging reverse faults parallel to major nne folds these structures reflect the transition from purely horizontal movement along major strike slip faults of the gaspe peninsula to vertical movement along thrust faults in southern quebec acadian structural variations within the quebec appalachians are interpreted in terms of a continental collision of gondwana along the irregular margin of laurentian and its taconian accreted terranes