chronology of late wisconsinan glaciation in middle north america abstract we propose a chronology of late wisconsinan glacial fluctuations in middle north america from alberta to wisconsin based on radiocarbon dates derived solely from wood previous chronologies of the southwestern margin of the north american continental ice sheet have depended to a considerable degree on radiocarbon dates from fine grained organic sediment this material is commonly contaminated with older carbon resulting in chronologic confusion by using only dates from wood much of the confusion disappears however because of the scarcity of wood dates only four of the sixteen identified fluctuations are accurately dated an advance into iowa about 14 000 to 13 500 bp an advance into south dakota and iowa about 12 300 bp an advance into the lake michigan basin about 11 700 bp and an advance into the lake superior basin about 9900 bp in addition the beginning of late wisconsinan glaciation before 20 000 bp is fairly well documented none of the fluctuations in the western part of the region are accurately dated

field criteria for the recognition of till or tillite abstract till is a highly variable sediment it is formed and deposited by primary glacial and also by closely associated penecontemporaneous secondary non glacial processes therefore the range of the criteria useful for the recognition of till or tillite is very broad and some of the characteristics are restricted to certain varieties of till only consequently no single descriptive characteristic would apply to all tills various site specific petrographic characteristics of tills and also regional indicators of the presence of a glacier in the area investigated are discussed by combining these multiple criteria a sediment may be identified or rejected as till with a greater certainty than by applying only one or another set of the above criteria most of the characteristics of till or of the glacial environment can be identified in the field and a regional study must supplement detailed site investigations

geology and quaternary environments of the first preglacial palaeolithic sites found in alberta canada abstract a pebble tool industry including two chronologically different stone artifact assemblages reminiscent of the eurasian palaeolithic has been recorded in late pleistocene sections at two locations in the bow river valley southwestern alberta authenticity and provenance of the deeply buried archaeological record is evidenced by culture diagnostic percussion flaked artifacts incorporated in preglacial fluvial gravels and overlying glacial diamictons and by identical textural patterns on stone tools found in and eroded from the exposures geological context suggests a fluctuating braided river setting during the earlier occupation discarded lower series quartzite and hard carbonate rock artifacts subglacially entrained into the cordilleran bow valley till document distortion of the earlier site silver springs by a valley glacier emerging from the rocky mountain ice lobe following the valley deglaciation a later occupation episode is manifested by a formally analogous flaked lithic assemblage excavated in situ on top of the till at a nearby site varsity estates this more recent occupation surface was subsequently buried under 24 m of glaciolacustrine sediments after submergence of the river valley by a proglacial lake glacial lake calgary dammed by the laurentide ice advance into the eastern calgary area implying a minimum early late wisconsinan age ca 21 000 bp for the lithic industry the presence of the later upper series artifact assemblage and the associated palynological data do not support the view that envisages an extremely cold inhospitable glacial environment on the eastern slopes of the canadian rocky mountains throughout the late wisconsinan their stratigraphic position also indicates temporal asynchroneity between cordilleran and laurentide ice during the last glacial maximum in the bow river valley the area of presumed coalescence of the two ice masses although a more rapid response of the western mountain glacier to climatic change is evident the apparent absence of pedogenic alteration of the till surface and the fresh appearance of the excavated stone artifacts suggest that a short time span separated the two glacial events the archaeological record provides evidence of an earlier palaeo american peopling of western interior canada long before the emergence of the final pleistocene palaeoindian cultures characterized by elaborate bifacial stone projectile point flaking technologies traditionally regarded as the earliest cultural manifestations in north america silver springs is the first early site on the continent found below glacial deposits realization that other american palaeolithic sites potentially of considerable antiquity should be recognized in similar geological settings and introduction of adequate geoarchaeological site survey techniques have crucial relevance for elucidation of the earliest new world prehistory

remote sensing and petroleum seepage a review and case study when reservoirs leak varying quantities of oil and gas migrate to the surface as macroseeps which are visible and microseeps which are invisible this review article describes the mechanisms of seepage and the resulting surface manifestations in relation to optical high resolution remote sensing data oil pools and tar deposits macroseeps often can be detected directly by remote sensing microseeps are more difficult to study using remote sensing but they give rise to vegetation stress and cause geochemical alterations in soil and rocks which can be studied indirectly using hyperspectral sensors an integrated methodology is presented to combine various geoscience and remote sensing datasets for seepage detection a combination of red edge modelling algorithms and spectral matching tools is identified that provides a validated technique for onshore microseepage detection these remote sensing tools are not only important for petroleum exploration but also have environmental implications because seeps emit greenhouse gases a statistical data integration approach was developed based on bayesian assumptions which can be used to integrate hyperspectral remote sensing data other satellite remote sensing data and ancillary field geological and geochemical datasets for modelling microseepage in a case study from the ventura basin santa barbara in southern california probe 1 data from the 1998 geosat group shoot are integrated with field and subsurface geological and geochemical data to predict possible sites of hydrocarbon microseepage

emergence of the canadian rockies and adjacent plains a comparison of physiography between end of laramide time and the present day abstract the landscape of the canadian rockies in southern alberta is not a direct result of constructional processes that is the ridges and peaks have not been pushed into the positions in which we see them today tectonic activity provided original elevation but not mountains at the end of laramide time what are now the front ranges and foothills of the rockies comprised a high elevation upland of relatively low relief the present mountain physiography is the result of 55 60 million years of post orogenic differential erosion in which more resistant rocks have been left at higher elevations than less resistant rocks the canadian rockies and the foothills are developed in a thin skinned thrust and fold belt created during the laramide orogeny the adjacent interior plains cut across foreland basin sediments derived from the mountains the mountains currently consist of large parts of ridges of well indurated paleozoic and locally proterozoic rock alternating with valleys developed in soft mesozoic clastic rock in the foothills where the soft mesozoic rock is at the surface relief is subdued but ridges of more resistant sandstone rise above shaley lowlands the plains are relatively flat but also contain erosional outliers of higher paleo plains surfaces numerous lines of evidence suggest that the mountains and foothills have lost several kilometers of overburden since the end of the laramide orogeny while the western plains have lost at least 2 km requiring that the local relief of the mountains and foothills that we see is erosional in origin local physiography is adjusted to lithology the mountains have high relief because the exposed sub mesozoic rocks can hold up high steep slopes whereas the foothills have low relief because the underlying cretaceous rocks cannot hold up high steep slopes the east facing escarpment at the mountain front is a fault line scarp along a low angle thrust mesozoic rocks involved in the deformation originally extended all the way across the thrust and fold belt and physiography of the belt at the end of laramide time 60 55 ma depended mainly on whether mesozoic or paleozoic proterozoic rocks were exposed at the surface at that time a reconstruction using critical taper theory generally agrees with reconstructions from earlier stratigraphic and paleothermometry studies what are now the front ranges at the eastern edge of the rocky mountains were mostly or perhaps entirely covered with mesozoic rocks and despite that high elevation had a hilly not mountainous character the main ranges in the central rocky mountains were in part stripped of mesozoic cover by then and more mountainous treeline was higher then and the thrust belt may have been largely or entirely vegetated generation of modern relief in the front ranges including the escarpment at the mountain front had to await stripping of mesozoic rocks and incision of rivers into harder substrates in post laramide time the interior plains are an erosional surface that was cut 1 to 3 km below the aggradational top of the foreland basin sediments although some of the present low local relief of the plains results from weakness of underlying cretaceous tertiary rocks the low relief is probably largely related to the process of denudation

archaeological constraints on some geological interpretations of a late wisconsinan site at varsity estates calgary alberta abstract late glacial history in western alberta has been a subject of debate as this area lies in the zone of assumed contact of the cordilleran glaciers and laurentide ice shield the geographic limits and timing of the coalescence of the two ice masses however are not clear except for the west central part of the province with the documented merger in the athabasca valley recently arguments for a complete late wisconsinan coalescence in the prairies all along the rocky mountain foothills have been presented based on 14c dates 21 ka and cosmogenic 36cl dates

clastic facies models and facies analysis summary the term facies is used either descriptively for a certain volume of sediment or interpretatively for the inferred depositional environment of that sediment facies models are intellectual aids to the understanding of sedimentary environments and the origin of ancient sedimentary rocks many different models can be constructed to explain a given set of data depending on which aspect of the facies requires the most illumination and on the types of techniques used in the analysis when dealing with ancient rocks facies modelling is the last stage in the process of facies analysis which consists of the detailed description of exposed or cored sediments their classification into objectively defined facies the compilation of the characteristics of each facies the deduction of the processes of deposition of each facies the examination of the spatial relationships between facies and the recognition of facies associations the interpretation of the overall depositional environment of the association and the detailed interpretation and modelling of individual facies short cuts can lead to fallacious interpretations reliable facies models cannot be produced without careful facies analysis a facies model may be plausible yet totally inapplicable to the facies from which it was supposedly derived

thermal effects and timing of thrusting in the moine thrust zone illite crystallinity studies in the foreland to the moine thrust belt show a widespread heating event which is interpreted as a thermal response to thrust sheet emplacement temperatures reached 275 c approximately 24 ma after the main thrusting events based on the relationships between syn thrusting intrusions and the thrust planes combined with radiometric dates from the moine sheet it is argued that movement on the moine thrust started between 440 and 430 ma ago contractional slip in the moine thrust belt ceased at about 425 ma ago and it is proposed that illite metamorphism attained temperatures of 275 c at about 408 ma ago

a single late wisconsin laurentide glaciation edmonton area and southwestern alberta the absence of igneous and metamorphic clasts of canadian shield origin in the saskatchewan gravels and sands preglacial valley fills in seven active gravel pits studied over a 5 yr period coupled with 29 radiocarbon dates 21 300 42 910 yr b p suggest that laurentide glaciation prior to the late wisconsin did not reach the edmonton area on the basis of edmonton9s elevation 670 m above sea level asl compared to higher regional elevations to the south calgary 1060 m asl and maps of the retreat pattern of late wisconsin laurentide ice which we equate approximately with advance pattern it is likely that large areas of higher elevation in alberta south and west of edmonton only underwent the late wisconsin event not multiple glaciations

geologic constraints on archeological interpretations of a late wisconsinan site at varsity estates calgary alberta abstract a corollary of j chlachula s interpretation that chipped quartzite cobbles at the contact of lake calgary sediments and underlying till represent an early late wisconsinan lithics industry is the conclusion that laurentide and cordilleran ice did not coalesce in late wisconsinan time contrary to that conclusion are 1 nw se oriented streamlined landforms in the foothills area which could have been created only by coalescent ice flow along with numerous radiocarbon dates which indicate that laurentide ice did not advance to central and western alberta before late wisconsinan time 2 cosmogenic 36 cl dates of 12 17 ka on the foothills erratics train indicating late wisconsinan coalescence 3 an estimated thickness of 1000 m or more of late wisconsinan coalesced ice in western calgary based on mapped laurentide limits 100 km south of calgary furthermore recently discovered rare shield clasts in the till at the varsity estates and silver springs sites suggest that the till was deposited by ice at least partly of laurentide origin as laurentide ice retreated lake calgary would have immediately inundated the site allowing no time or space for human cobble chipping paleomagnetism indicates that the lake sediments at the varsity estates site rotated 25 degrees to the nw after deposition presumably by rotational slumping slumping may have been syndepositional or due to channel cutting during periods of lake drainage and refilling neither scenario either supports or contradicts the archeological interpretation it is possible that the broken and chipped clasts interpreted to be artifacts were created by natural processes

summary of quaternary stratigraphy and history eastern canada deposits of three wisconsinan substages sangamonian stage and older quaternary stratigraphic units are recognized in eastern canada the age assignment of these units is based on radiocarbon dating and correlation of events quaternary deposits older than sangamonian are recognized locally in eastern canada in southern ontario glacial deposits directly underlie sangamonian sediments and are referred to as illinoian in age in other areas the ages of older sediments are largely unknown offshore core stratigraphy suggests that a major glaciation took place about 436 ka and that the illinoian oxygen isotope stage 6 was also a time of extensive glaciation in this report sangamonian is used as the name for the chronostratigraphic stage that includes all of deep sea oxygen isotope stage 5 and consequently on a regional basis it includes warm interglacial deposits glacial deposits and cool interglacial deposits in southern ontario the warm interglacial deposits are represented by the don formation the stadial deposits by the scarborough formation and the cool interglacial deposits by the pottery road formation warm interglacial deposits have not been recognized in quebec unless they are part of the pre johnville sediments the becancour till is included as glacial sangamonian sediments and the st pierre sediments are recognized as cool interglacial sediments the early wisconsinan appears to have been the time of maximum wisconsinan glaciation in eastern canada with ice moving south of the international boundary and well out onto the continental shelf the middle wisconsinan was primarily a nonglacial period in southern ontario and a glacial stade elsewhere in eastern canada in southern ontario the middle wisconsinan record has been subdivided into two interstades port talbot and plum point separated by a stade cherrytree the port talbot interstade began before the limit of radiocarbon dating before 48 ka and ended about 40 ka glacial or near glacial conditions of the cherrytree stage lasted from about 40 to 35 ka ago and the plum point interstade was from about 35 to 23 ka ago central st lawrence lowland was occupied by ice throughout the middle wisconsinan but southeastern quebec and the montreal area were briefly deglaciated scattered evidence in atlantic canada suggests local deglaciation of coastal areas during middle wisconsinan but extensive ice remained on the continental shelf and ice from centres located on the shelf flowed onto land in at least two areas glacial conditions predominated throughout eastern canada during the late wisconsinan at the late wisconsinan maximum through moving ice deposited the catfish creek drift in southern ontario but ice lobes which developed in the basins of the great lakes after 15 5 ka controlled ice flow during a period of ice margin oscillation and retreat a calving bay developed in lower st lawrence valley after the late wisconsinan maximum causing a reversal of flow on the south shore of the st lawrence and replacing ice in the valley with the champlain sea about 12 ka late wisconsinan glaciers were largely limited to land areas in atlantic canada local ice caps dominated with complicated patterns of flow and retreat developing as centres of accumulation shifted and competing ice centres achieved dominance the period of late wisconsinan retreat in atlantic canada appears to have lasted from about 14 to 10 ka

pleistocene mammals of the edmonton area alberta part i the carnivores late pleistocene fossils have been recovered sporadically in the edmonton area in central alberta for many years but there has been little work in determining their age fossils from quarries in north saskatchewan river terraces and buried valley gravels are recognized as late pleistocene mid wisconsinan and early holocene taxa and numerous 14c dates on mammalian remains now support the assessment the mammalian fauna consists of at least 16 taxa including mostly grazing herbivores but also three carnivores canis cf canis lupus gray wolf arctodus simus giant short faced bear and panthera leo atrox pleistocene lion the carnivores are first records for the region and arctodus is a first record for alberta

mid wisconsinan vertebrates and their environment from january cave alberta canada abstract january cave in the rocky mountains of southwestern alberta has yielded vertebrate remains from a coprocenosis of mid wisconsinan age taphonomic analysis indicates accumulation by raptors mostly owls and mammalian carnivores the vertebrate record together with pollen analysis indicates that cool dry conditions prevailed in an extensive tundra like environment with prairie elements in the valleys below thirty four mammalian taxa have been recovered from january cave today some of these species e g lemmus sibiricus and dicrostonyx torquatus do not coexist with others e g cynomys sp mustela nigripes vulpes velox and lagurus curtatus therefore the january cave local fauna represents a nonanalog mammalian community characteristic of the late pleistocene it suggests that the region enjoyed an equable climate with reduced climatic extremes but still cool further supporting a mid wisconsinan age estimate for the fauna it is the first major small vertebrate fauna of its age to be reported from alberta

paraglacial origin for terraced river sediments in bow valley alberta fluvial terraces flank the course of the bow river for 100 km from the eastern margin of the rocky mountain front ranges to calgary and beyond the terraces are cut predominantly in gravel fill which ranges in thickness from approximately 10 m in the calgary area to 30 m near the mountain front sedimentary structures in the gravels indicate a braided stream sedimentary environment in contrast to the present quasi stable sinuous single channel form of the bow river radiocarbon dates on ungulate remains from the gravels indicate the main period of fill occurred ca 11 500 10 000 rcybp radiocarbon years before present previous workers have postulated that the gravels originated directly as outwash from a glacial advance to or beyond the mountain front this explanation has been refuted by recent stratigraphic and palynological investigations a complex nonglaciofluvial origin is proposed for these terraces and the sediments that form them the last glacial advance to reach the mountain front was well

late quaternary stratigraphy sedimentology and history of the jasper townsite area alberta canada geomorphic stratigraphic and sedimentologic evidence obtained from quaternary sediments near jasper alberta is used to reconstruct depositional environments in the vicinity of two former confluent valley glaciers sedimentation occurred mainly in the valley centre in a pre existing river channel lateral ice marginal sedimentation along the inset valley walls was important during both the advance and the retreat stages prior to and during glacial advance horizontally stratified gravels sands and silts were deposited in a braided stream near the valley bottom diamictons containing trough shaped sand lenses were deposited by subsequent proglacial debris flows and intermittent fluvial activity at higher stratigraphic positions outwash deposits confined to the valley wide are unconformably overlain by massive diamicton interpreted as subglacial till deposited as ice began to override the area the diamicton grades towards the valley side into ice contact debris deposited at the margins of the ex

geologic evidence for age of deposits at hueyatlaco archeological site vasequillo mexico direct tracing of beds during excavation in may 1973 confirmed that the artifact bearing layers at hueyatlaco underlie 10 m of fine grained water laid deposits that constitute part of the wide spread valsequillo gravels dissection of these deposits by the adjacent rio atoyac has reached a depth of 50 m the stratigraphic section at hueyatlaco includes four distinctive tephra units the oldest one occupies a small channel in a series of cut and fill stream deposits that have yielded bifacial tools it lies more than a meter above flat lying fine grained beds from which edge retouched tools have been recovered the three other tephra units occur higher in the section fission track ages on zircon phenocrysts from two of the younger tephra layers 370 000 200 000 and 600 000 340 000 yr 2 agree with concordant uranium series dates for a camel pelvis that was found associated with bifacial tools at hueyatlaco 245 000 40 000 yr by 230th and 180 000 yr by 231pa these dates are compatible with the depth of burial and subsequent dissection of the hueyatlaco deposits as well as with the degree of hydration of volcanic glass shards and with the extent of etching of heavy mineral phenocrysts from within the tephra layers these findings suggest to us that further search for archaeological remains in deposits as old as those at hueyatlaco would be warranted

mapping hydrocarbon induced mineralogical alteration in the northern tian shan using aster multispectral data seepage from hydrocarbon reservoirs can cause a number of chemical and or mineralogical changes in overlying rocks and soils these surface changes can be detected by remote sensing imaging systems the advanced spaceborne thermal emission and reflection radiometer aster is an advanced multispectral imaging system in the visible and near infrared vnir to shortwave infrared swir region band ratios of aster vnir and swir data to detect red bed bleaching and secondary carbonate formation induced by hydrocarbon seepage are proposed through analysis of the spectral properties of rock samples results show that aster band ratios of 2 1 and 4 8 can discriminate bleached red beds and secondary carbonate minerals due to hydrocarbon seepage in the northern tian shan they are in good agreement with mineral identification using x ray diffraction the ratio technique derived from aster data may provide a potential approach for hydrocarbon exploration in areas with sparse vegetation cover

laurentide glaciation in west central alberta a single late wisconsinan event the grande prairie region in west central alberta shows evidence of late wisconsinan laurentide glaciation in the form of a widespread till containing abundant erratic clasts derived from the canadian shield two sections located on the smoky river at watino and on the simonette river 80 km to the southwest expose sediment lying stratigraphically below the till a similar sequence is exposed in both localities 5 10 m of coarse quartzite gravel overlain by a thick sequence of sand and silt the gravel contains no laurentide erratics and is thus preglacial the contact between the basal gravel and the overlying sand and silt is sharp and conformable 14c dates from the base of the simonette section and throughout the watino section suggest a middle wisconsinan age thus the sediment exposed is interpreted as a conformable middle wisconsinan sequence the sedimentary sequences were deposited in a moderate to low energy braided stream system flowing towards the north the general fining up trend in the

sedimentology stratigraphy and geomorphology of glacial lake calgary at cochrane alberta canada stratigraphic and sedimentologic field data in the cochrane alberta area demonstrate that glaciolacustrine sediment comprising the calgary formation underlies glaciofluvial and fluvial sediment o

subglacial tunnel channels porcupine hills southwest alberta canada abstract at some time close to the last glacial maximum lgm high energy subglacial laurentide meltwater flows eroded a series of discontinuous tunnel channels into the northeastern flanks of the porcupine hills and adjacent parts of the high plains near nanton stavely and claresholm discrete channel segments kilometers long up to about 1 km wide and 100 m deep were carved into paleocene sandstone and shale of the porcupine hills formation floors of pine boneyard and crocodile channels all occur at elevations between 1050 and 1175 m a s l and share the characteristic of strongly convex up long profiles intrachannel drainage divides on each channel floor are tens of meters above the water entry and exit points formative flows therefore must have been pressurized in the subglacial nye channels prominent scour holes at some major bends in the channels now host ephemeral ponds or lakes during the channel erosion the overlying laurentide ice surface was probably close to its local lgm maximum elevation of ca 1400 1500 m a s l misfit modern streams now drain in opposite directions within the tunnel channels and there are only minor local distal accumulations of sediment derived from the tunnel channel erosion

stratigraphy and correlation of the glacial deposits on the montana plains till units representing at least three pre illinoian continental glaciations at least one illinoian glaciation and a late wisconsin glaciation have been identified on the montana plains early wisconsin or middle wisconsin till units have not been identified the southernmost limit of late wisconsin glaciation is in montana more than 170 km south of the lethbridge moraine in alberta canada figs 1 and 2 an interpretation that the lethbridge moraine is the limit of late wisconsin glaciation stalker 1977 1980 1983b stalker and harrison 1977 rutter 1980 1981 jackson 1983 is incompatible with stratigraphic and morphologic evidence from montana

late pleistocene glacial geomorphology and environment of the hand hills region and southern alberta related to middle wisconsin fossil prairie dog sites ichnofossils burrow casts and fossils from an extinct form of prairie dog cynomys niobrarius churcherii in the hand hills of south central alberta have provided an important late pleistocene stratigraphic marker the marker fossils provide relative and chronostratigraphic radiocarbon ages for nonglacial periglacial glacial and glaciotectonic events and environments in the region the high elevation hilltop position of the fossil sites 200 m above the surrounding plains permits reliable extrapolations of glacial environments to the surrounding region the burrow casts were preserved by infilling from surrounding and overlying sediments through processes of inwashing and animal activity three thousand bones primarily of the extinct prairie dog cynomys niobrarius churcherii were recovered from one site and several hundred more from other locations accelerator radiocarbon dates ams on bone collagen show that the prairie dogs lived in the area from at least 33 000 bp to around 22 000 bp p

preglacial archaeological evidence at grimshaw the peace river area alberta reply an assemblage of quartzite cobbles with attributes of cultural flaking and utilization has been recorded at the base of a laurentide till at the contact with underlying fluvial gravels in a section face of a gravel pit near grimshaw in the course of quaternary geology mapping of the peace river area the geological context with secondarily redeposited stone artifacts documents distortion of an early prehistoric site located in a nonglacial riverine setting by the expanding late wisconsinan continental ice from the north the lithic assemblage provides further evidence for an earlier pre last glacial occupation of north america predating the earliest postglacial 11 500 bp palaeoindian cultures traditionally regarded as the hallmark of peopling of the new world