quantification of tsunamigenic earthquakes by the mt scale abstract a magnitude scale m t previously defined by the author is unique among the many scales in seismology because it is based on the instrumental amplitude of tsunami waves its level being adjusted to agree with moment magnitude despite the simple definition the m t scale reliably measures the seismic moment of an earthquake as well as the overall physical size of the source of the tsunami in reality the seismic moment estimated from m t for 39 events around japan is found to be essentially equivalent to that estimated from seismic waves with an uncertainty factor of two on average the m t scale is useful for a quantitative discrimination of tsunami earthquakes that generate anomalously large tsunamis for their magnitude of 97 tsunamigenic events that occurred around japan during the period 1894 to 1985 at least eight tsunami earthquakes are identified from the m t vs m s relation

geochemical evolution of clay pore water as an indicator for palaeoenvironmental variability in the hebei plain northern china in order to elaborate geochemical evolution of clay pore water cpw and associated palaeoenvironment in hengshui where there is shallow saline water in the area of hebei plain a borehole with a depth of 130 m was drilled in august 2013 in hengshui city q4 sediments occurred above 35 m and q3 mainly at depth of 130 35 m sediment particle size geochemistry and deuterium and oxygen isotopes of cpw were analyzed the cpw was generally of meteoric origin and was influenced by evaporation total dissolved solids tds in pore water were high which was mainly controlled by na mg2 so4 2 and cl ratios of rna rca of cpw were mostly larger than 1 indicating the missing of ca2 as a result of evaporation and cation exchange at depths of 20 10 m ratios of rna rcl were larger than 1 reflecting the accumulation of na during the continent salinization process the tds and 18o values of cpw above 6 m demonstrated that cpw was primarily affected by human irrigation as well as by atmospheric precipitation the mean 18o values of cpw were 11 5 12 1 and 10 6 at depths of 130 90 65 29 and 23 0 m respectively which were lower than the 18o values of groundwater at depths of 90 65 m 9 8 and 29 23 m 8 2 the depletion in 18o of cpw suggested that the cpw saved the palaeoenvironment media at depths below 6 m the 18o of cpw indicated that the temperature decreased at the depths from 130 to 90 m and the climate became colder at depths of 65 29 m but evolved to be warm in holocene at depths of 23 0 m

isotopic composition of old ground water from lake agassiz implications for late pleistocene climate a uniform oxygen isotope value of 25 per mil was obtained from old ground water at depths of 20 to 30 meters in a thick deposit of clay in the southern part of the glacial lake agassiz basin the lake occupied parts of north dakota and southern manitoba at the end of the last glacial maximum and received water from the ice margin and the interior plains region of canada ground water from thick late pleistocene age clay deposits elsewhere a till in southern saskatchewan and a glaciolacustrine deposit in northern ontario show the same value at similar depths these sites are at about 50 n latitude span a distance of 2000 kilometers and like the lake agassiz sites have a ground water velocity of less than a few millimeters per year the value of 25 per mil is characteristic of meltwater impounded in the southern basin of lake agassiz this value corresponds to an estimated air temperature of 16 c compared with the modern temperature of 0 c for this area

tsunami from the mariana earthquake of april 5 1990 its abnormal propagation and implications for tsunami potential from outer rise earthquakes the tsunami generated by the mariana earthquake of april 5 1990 was observed on the japanese and pacific islands as far as hawaii the observed tsunami amplitudes are not a simple function of distance from the source but vary with large scale bathymetry numerical computations of tsunami propagation are made for actual bathymetry and the computed amplitudes are compared with the observations from the comparisons the seismic moment is estimated to be 1 4 1020nm very similar to that from seismic waves and indicates that the seismic waves and tsunami are equally excited the numerical computations also show that the tsunami propagated toward the japanese coast through two different paths one is through the trench system with high velocity and small amplitude the other along the ridge system with low velocity but large amplitude the two kinds of tsunami are identified on recently installed ocean bottom pressure gauges since the mariana earthquake was an outer rise earthquake in a weakly coupled subduction zone where the size of outer rise event is larger than underthrusting events it is possible that even larger earthquakes occur in this region the tsunami potential from such events must be considered including the unusual tsunami propagation

the tectonic evolution of the south atlantic from late jurassic to present an improved tectonic database for the south atlantic has been compiled by combining magnetic anomaly geosat altimetry and onshore geologic data we used this database to obtain a revised plate kinematic model starting with a new fit reconstruction for the continents around the south atlantic we present a high resolution isochron map from chron m4 to present fit reconstructions of south america and africa that require rigid continental plates result in substantial misfits either in the southern south atlantic or in the equatorial atlantic to achieve a fit without gaps we assume a combination of complex rift and strike slip movements 1 along the south american parana chacos basin deformation zone 2 within marginal basins in south america salado colorado basin and 3 along the benue trough niger rift system in africa these faults are presumed to have been active before or during the breakup of the continents our model describes a successive unzipping of rift zones starting in the southern south atlantic between 150 ma tithonian and approximately 130 ma hauterivian rifting propagated to 38 s causing tectonic movements within the colorado and salado basins subsequently between 130 ma and chron m4 126 5 ma the tip of the south atlantic rift moved to 28 s resulting in intracontinental deformation along the parana chacos basin deformation zone between chron m4 and chron mo 118 7 ma rifting propagated into the benue trough and niger rift inducing rift and strike slip motion after chron mo the equatorial atlantic began to open while rifting and strike slip motion still occurred in the benue trough and niger rift since chron 34 84 ma the opening of the south atlantic is characterized by simple divergence of two rigid continental plates

comparing vertical profiles of natural tracers in the williston basin to estimate the onset of deep aquifer activation comparing high resolution depth profiles of different naturally occurring environmental tracers in aquitards should yield consistent and perhaps complementary information about solute transport mechanisms and the timing of major hydrogeological and climatological events this study evaluated whether deep continuous profiles of aquitard pore water chloride concentration could provide further insight into the paleohydrology of the williston basin canada than possible using high resolution depth profiles of stable h o isotopes of water 18o 2h pore water samples were obtained from extracts of cores taken over 392 m of the thick cretaceous shale aquitard water samples were also collected from wells installed in the underlying regional sandy aquifer mannville group 93 m thick and from seepage inflows into potash mine shafts to 825 m below ground numerical modeling of the 1 d vertical cl profile supported diffusion dominated solute transport in the shales the modeling also showed a similar time frame for development of the cl profile prior to activation of the aquifer as determined from the 18o profile 20 25 ma however it provided a significantly longer and potentially better constrained time frame for evolution of the profile during the activation phase of the aquifer 0 5 1 ma the dominant paleoevent reflected in present day profiles of both tracers is the introduction of glaciogenic meteoric water to the mannville aquifer underlying the shale during the pleistocene the source area of this water remains to be determined

geochemical and scintillometric characterization and correlation of amethyst geode bearing parana lavas from the quarai and los catalanes districts brazil and uruguay geochemical studies of the six lowermost lava flows of the cretaceous serra geral formation parana volcanic province in quarai brazil and artigas uruguay were combined with flow by flow field studies of structures and scintillometric profiles to establish a consistent regional stratigraphic framework over at least 100 km this greatly improves exploration capability for amethyst and agate geodes a basalt colada mata olho alegrete facies serra geral formation was the first lava to flow over the ancient botucatu desert in the region but an andesite colada catalan overstepped this basalt in many places perhaps palaeohighs four basaltic andesites complete the lava stratigraphy in this formation adding up to 300 m of lavas the stratigraphic sequence of contrasting lava compositions is 51 0 wt sio 2 in the first lava followed by 57 5 52 5 56 0 53 0 and finally 54 5 wt sio 2 overall mgo variation is between 2 and 7 wt all lavas in the two districts are low ti 2 of the gramado type the characteristic contents of most major and trace elements 124 rock samples analysed allow the ready identification of each lava contrasting rock chemistry also results in strong variation in scintillometric values 270 points measured in the field and nineteen continuous borehole profiles from bottom to top of the stratigraphy the cps values are 49 3 2 123 10 3 62 4 7 94 4 6 45 and 85 colada catalan has the structure of aa lava particularly the contorted igneous banding and autobreccias in the upper and lower crusts in some places a 2 m thick silicified sandstone layer lies on top of some coladas and silicified sandstone forms breccias with volcanic rocks geochemistry of the six lavas indicates complex evolution involving melting of lithospheric mantle injection into the crust and assimilation of crust followed by fractional crystallization this study indicates the possibility of world class deposits of amethyst geodes on the brazilian side of the border with uruguay

sources of tsunami and tsunamigenic earthquakes in subduction zones we classified tsunamigenic earthquakes in subduction zones into three types earth quakes at the plate interface typical interplate events earthquakes at the outer rise within the subducting slab or overlying crust intraplate events and tsunami earthquakes that generate considerably larger tsunamis than expected from seismic waves the depth range of a typical interplate earthquake source is 10 40km controlled by temperature and other geological parameters the slip distribution varies both with depth and along strike recent examples show very different temporal change of slip distribution in the aleutians and the japan trench the tsunamigenic coseismic slip of the 1957 aleutian earthquake was concentrated on an asperity located in the western half of an aftershock zone 1200km long this asperity ruptured again in the 1986 andreanof islands and 1996 delarof islands earthquakes by contrast the source of the 1994 sanriku oki earthquake corresponds to the low slip region of the previous interplate event the 1968 tokachi oki earthquake tsunamis from intraplate earthquakes within the subducting slab can be at least as large as those from interplate earthquakes tsunami hazard assessments must include such events similarity in macroseismic data from two southern kuril earthquakes illustrates difficulty in distinguishing interplate and slab events on the basis of historical data such as felt reports and tsunami heights most moment release of tsunami earthquakes occurs in a narrow region near the trench and the concentrated slip is responsible for the large tsunami numerical modeling of the 1996 peru earthquake confirms this model which has been proposed for other tsunami earthquakes including 1896 sanriku 1946 aleutian and 1992 nicaragua

ice age paleotopography a gravitationally self consistent theory of postglacial relative sea level change is used to infer the variation of surface ice and water cover since the last glacial maximum lgm the results show that lgm ice volume was approximately 35 percent lower than suggested by the climap reconstruction and the maximum heights of the main laurentian and fennoscandian ice complexes are inferred to have been commensurately lower with respect to sea level use of these ice age boundary conditions in atmospheric general circulation models will yield climates that differ significantly from those previously inferred on the basis of the climap data set

basalt magmatism along the passive continental margin of se brazil campos basin the se brazil passive continental margin is characterized by tholeiitic magmatism that is particularly widespread in the marginal campos basin facing the inland flood basalts of the adjacent parana basin campos magmatism is represented by early cretaceous ec 134 122 ma flood basalts and minor upper cretaceous early tertiary basalt flows and intrusives which were emplaced in a basin with attenuated crustal thickness 20 km petrography mineral chemistry wholerock geochemistry and sr nd isotope composition emphasize that the ec campos basalts have suffered extensive seawater interaction which caused enrichment in mgo feo total k2o rb and ba and depletion in sio2 and cao while zr nb y and ree remained virtually constant in samples with loss on ignition values less than 4 wt in general campos basalts have bulkrock chemistry similar to those of the inland parana tholeiites 140 130 ma with relatively low concentrations of incompatible elements and tio2 16 morb mid ocean ridge basalt mantle in simple binary mixing models on the whole the early cretaceous campos basalts appear as an easterly younger extension of the northern parana volcanism and probably erupted during early stages of the major riftingprocesses which caused continental thinning it is notable that in the campos marginal basin both the basalt magmatism contemporaneous with the continental break up as well as that which occurred after the s america africa separation appears substantially related to subcontinental lithosphere and a dupal like oib ocean island basalt e g tristan da cunha source components

synthesis and model of formation water flow alberta basin canada based on a large amount of publicly available data several studies have previously examined the flow of formation waters in different parts of the alberta basin offering various interpretations as to the causes of the observed pressure regime and flow pattern however there has been no synthesis of these diverse studies on a basin wide basis accordingly these studies are critically reviewed in this paper and synthesized in a new basin scale model of the flow of formation waters in the alberta basin the proposed regional scale model has significant implications for understanding hydrocarbon migration pathways ore genesis the geothermal regime and deep waste disposal in the alberta basin several flow systems each one driven by a different mechanism are identified together with the main processes leading to the nonhydrostatic pressures observed in the basin two megahydrostratigraphic successions and associated flow systems are recognized the first succession corresponds to the pre cretaceous passive margin stage of basin development and consists of thick carbonate dominated aquifer systems separated by shaly aquitards and evaporitic aquicludes a northeastward basin scale flow system is driven by basin topography with recharge in montana and discharge in northeastern alberta southwest to northeast regional scale flow adjacent to the fold and thrust belt is probably the result of past tectonic processes the salinity of formation water in pre cretaceous aquifers is high and generally increases both northward and with depth this variability is the result of increased water rock reactions mineral solubility with increased temperatu e and of incomplete flushing by meteoric water as a result of salinity variations flow retarding buoyancy effects can be important the second megahydrostratigraphic succession corresponds to the post jurassic foreland stage of basin evolution and consists of thick shaly aquitard systems and relatively thin sandstone aquifers in the southwestern part of the basin flow in isolated aquifers is driven southwestward by erosional rebound in the thick intervening shales downdip toward the fold and thrust belt the salinity of formation waters in the post jurassic aquifers is low mixing of waters and interference between the major flow systems takes place along the pre cretaceous unconformity where successively older pre cretaceous aquifers subcrop from west to east flow in shallow lo al systems at the top of the sedimentary succession is driven by local topography

controls on the long term downward transport of δ h of water in a regionally extensive two layered aquitard system 1 seven high resolution 0 3 0 6 m depth intervals 1 d vertical profiles of the h of pore water were collected across a 300 km2 study area in southern saskatchewan canada to define the vertical controls on solute transport in a 120 m thick two layered aquitard system the 1 d profiles were augmented with an existing h profile collected from a previous study the surficial aquitard in the area consists of quaternary deposits either glacial till or lacustrine deposits 13 to 128 m thick underlain by an upper cretaceous claystone aquitard 80 110 m thick the shape of the individual h profiles and associated 1 d transport modeling suggest diffusion is the regionally dominant vertical transport mechanism across the aquitards the profile shape is controlled by the thickness of the quaternary deposit and the h value at the upper boundary which coincides with the depth of the water table the upper boundary h value varies considerably across the area 149 to 101 perhaps due to differences in local hydrological conditions e g slope aspect infiltration across the landscape modeling of all profiles shows the timing for till deposition and the timing of climate change during the holocene are consistent across the area 30 ka and 7 10 ka before the present respectively corroborating other studies this study provides insights into the hydrogeologic controls on solute transport in an aquitard system and associated geologic and climatic changes for a prairie region over the past 30 ka and improves our understanding of initial and time dependent transport boundary conditions for the study of aquitards

the diffusive tortuosity of fine grained unlithified sediments abstract use of fick s first law to estimate solute fluxes is arguably the most common and important calculation related to the geochemistry and environmental chemistry of fine grained unlithified sediments in such porous media the diffusion coefficient in this law must be reduced by the square of the tortuosity to account for the longer diffusive paths experimental methods to estimate tortuosity are specialized or time consuming and not routinely done an analysis of available data shows that tortuosity is accurately correlated to readily measured porosity values through the simple relation 2 1 l n 2

late pleistocene precipitation δ18o interpolated across the global landmass global water cycles ecosystem assemblages and weathering rates were impacted by the 4 c of global warming that took place over the course of the last glacial termination fossil groundwaters can be useful indicators of late pleistocene precipitation isotope compositions which in turn can help to test hypotheses about the drivers and impacts of glacial interglacial climate changes here a global catalog of 126 fossil groundwater records is used to interpolate late pleistocene precipitation 18o across the global landmass the interpolated data show that extratropical late pleistocene terrestrial precipitation was near uniformly depleted in 18o relative to the late holocene by contrast tropical 18o responses to deglacial warming diverged late pleistocene 18o was higher than modern across india and south china but lower than modern throughout much of northern and southern africa groundwaters that recharged beneath large northern hemisphere ice sheets have different holocene pleistocene 18o relationships than paleowaters that recharged subaerially potentially aiding reconstructions of englacial transport in paleo ice sheets global terrestrial late pleistocene precipitation 18o maps may help to determine 3 d groundwater age distributions constrain pleistocene mammal movements and better understand glacial climate dynamics

on the mechanical role of smectite in subduction zones smectites a group of hydrated phyllosilicate minerals are often a main component of sediments entering a subduction zone they are common in hemipelagic sediments and consist of an authigenetic component that arises from the alteration of volcanic ash intercalated in the sediment and a detrital component smectite rich strata are structurally weak retain water and are highly porous a review of sediment lithology in subduction zones around the world suggests that decollement zones may preferentially form in smectite rich horizons one consequence of this observation is that the assignment of high frictional resistance to materials in a decollement may be unwarranted at deeper structural levels smectite is transformed to illite a mechanically stronger mineral estimates of the depth of this transition coincide with the depth at which earthquakes are first detected along plate interfaces i speculate that the smectite illite transition in subduction zones may be an important component of sediment consolidation processes that trigger interplate seismicity

pleistocene stratigraphy of the saskatoon area saskatchewan canada an update pleistocene deposits in the saskatoon area are divided into the sutherland and saskatoon groups the sutherland group is divided into the mennon dundurn and warman formations and the saskatoon group is divided into the floral and battleford formations the floral formation is subdivided into the lower till the riddell member and the upper till each formation is composed of a sequence of deposits including basal proglacial sediment till upper proglacial sediment and nonglacial sediment each formation is defined primarily on the basis of carbonate content and stratigraphic position of its till and commonly it is bounded by weathered zones and or nonglacial sediments the sutherland group is pre illinoian in age and the lower till of the floral formation is illinoian in age the riddell member between the lower and upper tills of the floral formation is late rancholabrean probably sangamon in age radiocarbon ages of sediments lying between the upper till of the floral formation early wis

modelling of the hydro mechanical response of sedimentary rocks of southern ontario to past glaciations abstract glaciation is considered as one of the main natural processes that can have a significant impact on the long term performance of a deep geological nuclear waste repository dgr located in the northern hemisphere the northern part of the american continent has been subjected to a series of strong glaciation and deglaciation events over the past million years the last glacial cycle in the northern hemisphere started approximately 110 000 year ago during that cycle southern ontario was buried under a continental ice sheet with a maximum thickness of up to 3000 m at about 20 000 years ago the ice cap retreated approximately 10 000 years ago however field data from deep boreholes in sedimentary rocks of southern ontario show anomalous pore water pressure including underpressure and overpressure zones in this paper a large scale coupled hydro mechanical hm model is developed to investigate the hydro mechanical hm response of the sedimentary rocks of southern ontario to past glacial cycles particular emphasis has been placed on the evolution of pore water pressures and surface displacements the hm model is verified using analytical solutions the results of the large scale hm modeling study shows that the past glaciation particularly the second cycle 22 000 apb had significant impact on the pore water pressure gradient and effective stress distribution in the sedimentary rocks of southern ontario furthermore good agreement between the large scale modeling results and anomalous pressures leads us to the conclusion that these anomalies could be glacially induced the results of this research can provide information that will contribute to a better understanding of the impact of future glaciations on the long term performance of drgs in sedimentary rocks

chemical stratigraphy of the parana lavas south america classification of magma types and their spatial distribution a new classification scheme has been developed to assign the lava flows of the parana continental flood basalt province south america into geochemically distinct magma types with six basaltic major and trace element abundances and or ratios by mapping out the spatial distribution of these magma types within the lava sequences it has been possible to determine the internal stratigraphy of the lava pile on a regional scale previous studies on road profiles traversing the well exposed coastal serra geral escarpment of southern brazil are summarised together with results from some new sampled sections more widespread stratigraphical investigations of the parana lavas have been hampered by the lack of sufficient topographic relief and the cover of sedimentary rocks however access to drill core chippings from nine boreholes in the central parana region has provided a unique opportunity to investigate the stratigraphy of the otherwise inaccessible deeper levels of the lava pile and to map out stratigraphic variations in three dimensions the borehole samples have indicated cated a stacking of units of different magma types all overlapping towards the north which suggests that the main locus of magmatism moved northwards with time within the parana basin this migration could be related to the northward propagation of rifting during the initiation of the south atlantic ocean maps of the surface distribution of samples of each magma type show a pattern consistent with the stratigraphy inferred from the boreholes although suggesting that the shift in magmatism may have been towards the northwest on the basis of geochemical similarities between magma types and their inferred stratigraphical relationships it is proposed that the parana can be divided into two principal magmatic centres 1 an older one in the south comprising the gramado esmeralda and urubici magma types and 2 a younger one developed about 750 km to the north formed by the pitanga paranapanema and ribeira magma types

mantle plumes and flood basalt stratigraphy in the parana south america geochemical studies of the parana continental flood basalts in brazil have led to the recognition of distinct magma types which have been used to infer the internal stratigraphy of the lava pile the overstepping of stratigraphic units toward the north and a similar compositional change in sills within the underlying parana basin sedimentary rocks imply that the site of magnatism migrated 750 km toward the north during this volcanic event this has important implications for recent plume related models that have argued whether fithospheric rifting must accompany the presence of a mantle plume in order to generate continental flood basalt magmatism it is difficult to ascribe the magnitude and direction of the shift in the locus of the parana magmatism to movement of the brazilian lithosphere relative to the underlying tristan mantle plume instead it is suggested that the observed lava distribution and internal structure of the parana etendeka flood basalt province were imposed by the intracacies of the rifting process during the initial opening of the south atlantic ocean

partial melting of mantle wedge and evolution of island arc crust evolution of the crust in the northeast honshu arc is discussed on the basis of the melting experiments of a peridotite under hydrous conditions and the crustal compositions estimated from deep crustal xenoliths and seismic velocity data the chemical compositions of melts formed by partial melting of a hydrous peridotite within the pressure temperature conditions for shallow parts of the mantle wedge 1 2 2 0 gpa have been experimentally determined with the sandwich experiment technique the melts range from olivine tholeiitic to magnesian andesitic compositions sio2 48 56 wt mgo 9 14 wt beneath the volcanic front in the northeast honshu arc and are slightly less silicic beneath the coast of the sea of japan the crustal compositions of the volcanic zone in the northeast honshu arc estimated from deep seated crustal inclusions in volcanic rocks and the velocity structures of the crust are andesitic in the central zone and high alumina basaltic near the coast of the sea of japan the compositions of possible primary melts formed in the mantle wedge are significantly more mafic than these crustal compositions consequently if the major part of the crustal materials in the volcanic zone was formed by magmas generated in the mantle wedge thick up to 30 km ultramafic cumulates including olivine pyroxenite must have been formed beneath moho during fractional crystallization and would constitute the upper part of the mantle wedge the volume of the mantle wedge consisting entirely of even fertile peridotite was not sufficient to produce crustal materials and cumulates in the volcanic zone by such processes in the northeast honshu arc a static mantle wedge model is therefore not satisfactory for the growth of the crust in northeast honshu arc a dynamic model is suggested in which the mantle materials have been supplied into the mantle wedge from the back arc side by a convective flow

the impact of early cretaceous gateway evolution on ocean circulation and organic carbon burial in the emerging south atlantic and southern ocean basins abstract organic carbon burial is an important driver of carbon cycle and climate dynamics on geological and shorter time scales ocean basins emerging during the early cretaceous break up of gondwana were primary sites of organic carbon burial implying that their tectonic and oceanographic evolution may have affected trends and perturbations in global climate via changes in local organic carbon burial assessing the role of individual ocean basins in the global carbon climate context requires a sound understanding of the processes that induced large scale changes in carbon burial and the timing of these changes here we reconstruct the oceanographic evolution and its links to organic carbon burial in the barremian to albian south atlantic and southern ocean basins which may have acted as carbon sinks of global importance our reconstruction is based on combined seawater neodymium isotope and sedimentological records obtained from multiple deep sea drill sites and a new general circulation model deep water circulation within and between those basins was primarily controlled by the opening of the shallow falkland plateau gateway between 118 ma and 113 ma and the deep georgia basin gateway by 110 ma for which we provide new age constraints based on biostratigraphic and carbon isotope data the opening of these gateways was accompanied by local to basin wide decreases in organic carbon burial suggesting that ocean circulation affected the oxygenation state via changes in deep water ventilation although our data do not provide quantitative information on the impact of changes in regional organic carbon burial on the global carbon cycle the synchronicity between the reduction of organic carbon burial in the south atlantic basin and global warming during the early albian points to a strong causal relationship

using regional datasets of isotope geochemistry to resolve complex groundwater flow and formation connectivity in northeastern alberta canada abstract in the southern athabasca oil sands saos region located in alberta canada individual in situ oil sands operators have conducted local geochemical and isotope groundwater studies to establish baseline characteristics and to improve understanding of the connectivity of water supply and disposal formations within individual leases canada s oil sands innovation alliance cosia initiated this study to combine the data from these individual studies along with public information into a comprehensive unified dataset to evaluate conceptual models of regional groundwater flow and the degree of interaction and separation between important water supply and disposal aquifers the unified dataset comprised over 293 groundwater samples from the main water source and disposal hydrostratigraphic units and included geochemical and isotopic tracers that can be used to identify sources 18o and 2h and age of water 3h and associated solutes 14cdic 36cl as well as the sources of salinity and diagenetic processes 13cdic 34sso4 87sr 86sr 11b 37cl and 81br and dissolved organics 13cdoc the tds and stable isotope composition 18o and 2h of groundwater from several cretaceous formations were used to identify three main mixing controls i areas where locally recharged groundwater mixes with glaciogenic water were identified by lower 18o and 18o values high tds cl br and 34sso4 87sr 86sr and 37cl values consistent with dissolution of evaporites these areas were situated where vertical pathways through otherwise competent formations are likely to occur ii mixing with paleo waters characterized by high tds and higher 18o and 2h signatures indicating groundwater recharged under warmer climate periods and or evaporative enrichment were identified in the south and southwestern portions of the study area the presence of these paleo waters indicate slow moving groundwater zones with limited lateral and vertical connectivity iii areas with potential connectivity to shallow aquifers were identified by their lower tds values modern meteoric 18o and 2h signatures hco3 type waters and 34s so4 and 87sr 86sr signatures consistent with weathering of shallow aquifer material geochemical and isotopic indicators suggest that in areas where the colorado group aquitard is thin or absent there is greater connectivity between the grand rapids formation and the shallower aquifers interpretation of the new unified dataset has improved understanding of the extent that glacial recharge had on devonian aquifers and overlying cretaceous formations and identified zones with relatively stagnant groundwater flow both of which have implications for regional groundwater resource development monitoring and potential wastewater disposal

chemostratigraphy of the neoproterozoic alona bay lavas ontario a basal sequence of flood basalt lavas associated with the neoproterozoic midcontinent rift system crops out in alona bay along the southeastern shore of lake superior in ontario the alona bay lava succession is about 1200 m thick and lies just north of the well studied contemporaneous mamainse point formation detailed chemostratigraphy of the alona bay lavas suggests they are grossly correlative with the basal portion of the mamainse point formation for instance like the basal part of mamainse point formation the alona bay section contains numerous high mgo lavas and can be subdivided into 4 5 groups with distinct chemical characteristics chemical variations within the alona bay groups are largely the result of fractional crystallization likely at moderate pressures one small group of alona bay lavas also carries the compositional imprint of crustal contamination the remaining inter group chemical distinctions at alona bay are the consequence of temporal changes in partial melting and source ch

the isotopic composition of the laurentide ice sheet and fossil groundwater stable isotopes have been used to study large scale changes in hydrology during the pleistocene epoch many of these efforts have required an estimate of the 18o value of runoff generated by melting ice sheets there is no consensus on representative values here we examine 18o values from fossil groundwater samples and isotope enabled general circulation models gcms to better understand the isotopic composition of the laurentide ice sheet lis groundwater 18o values ranged from 12 5 to 25 3 and tended to increase southward the 18o precipitation values predicted by gcms follow a similar trend but increase more steeply southward the difference in groundwater and gcm output can be explained by invoking movement of glacial ice and meltwater along with mixing within groundwater systems most groundwater 18o values are higher than an average lis 18o value of 25 4 2 5 calculated based on estimated ice sheet volumes and sea level data

the timing of crustal extension and the eruption of continental flood basalts the association between mantle plumes continental flood basalt eruption and the extension and rifting of the crust is well recognized1 3 but there has always been controversy as to whether the plume or the rifting was the initiating factor4 5 was rifting triggered by doming above the thermal plume2 3 6 or was rifting the driving force preceding the associated volcanicity7 8 here i show that recent flow by flow mapping of two continental flood basalt provinces the columbia river basalt group and the deccan basalt group allows one to infer the relative timing of volcanicity and crustal extension in both provinces eruption of the main tholeiitic phase preceded significant extension and crustal thinning this suggests that the primary event in the formation of these provinces was the upwelling of a mantle plume and that the subsequent crustal extension rifting and decompression was in part a consequence of the initiation of that plume

remobilisation of the continental lithosphere by a mantle plume major trace element and sr nd and pb isotope evidence from picritic and tholeiitic lavas of the noril sk district siberian trap russia the late permian to early triassic siberian traps have been sampled by drill core core sg 9 and from surface exposure section 1f in the noril sk region of the siberian platform russia combined major trace element and nd sr and pb isotope data on selected samples through the siberia trap offer new chemostratigraphic criteria for the identification and characterisation of two fundamentally different magma types and 9 of the 11 formations of lava developed near noril sk a lower sequence of sub alkalic basalts tholeiites and picritic basalts upwards these are the ivakinsky syverminsky and gudchichinsky formations are overlain by an upper sequence of picritic basalts and tholeiites interbedded with tuffs upwards these are the khakanchansky tuklonsky nadezhdinsky morongovsky mokulaevsky and kharayelakhsky formations the gudchichinsky and tuklonsky formations contain both picritic and tholeiitic lavas the tuklonsky formation tholeiites and picrites have moderate gd yb 1 6 1 8 low tio2 0 45 0 95 wt a significant negative ta and nb anomaly nb la 0 42 0 57 and unradiogenic nd nd chur to 4 6 in contrast both the gudchichinsky formation tholeiites and picrites have high gd yb 2 3 3 1 and tio2 1 2 2 3 wt no significant nb or ta anomaly nb la 0 8 1 1 and radiogenic nd nd chur to 7 3 the low ti and nb la high la sm and unradiogenic nd isotope signatures of the picritic tuklonsky formation lavas and the tholeiitic lavas of the upper sequence are characteristic of magmas strongly influenced by material from the continental lithosphere whereas the high ti and nb la low la sm and radiogenic nd isotope signatures of the lower sequence are more comparable to deeper asthenospheric mantle plume generated lavas similar to oceanic island basalts the lavas overlying the tuklonsky formation have mg numbers of 0 63 to 0 68 and are more evolved than the tuklonsky mg number 0 62 and have more radiogenic nd chur tuklonsky 0 03 to 4 66 mokulaevsky 0 60 to 1 61 but have many of the incompatible trace element features of the tuklonsky sky type magma these lavas show a progressive upwards decline in sio2 55 49 wt la sm 4 6 2 0 and ur sr 67 to 13 which has previously been attributed to a decrease in the proportion of crustal material contributed to the magma this paper explores and alternative model where a component of the crustal contribution might be derived from within an ancient region of the mantle lithosphere as recycled sediment rather than from the overlying continental crust

linear and nonlinear computations of the 1992 nicaragua earthquake tsunami numerical computations of tsunamis are made for the 1992 nicaragua earthquake using different governing equations bottom frictional values and bathymetry data the results are compared with each other as well as with the observations both tide gauge records and runup heights comparison of the observed and computed tsunami waveforms indicates that the use of detailed bathymetry data with a small grid size is more effective than to include nonlinear terms in tsunami computation linear computation overestimates the amplitude for the later phase than the first arrival particularly when the amplitude becomes large the computed amplitudes along the coast from nonlinear computation are much smaller than the observed tsunami runup heights the average ratio or the amplification factor is estimated to be 3 in the present case when the grid size of 1 minute is used the factor however may depend on the grid size for the computation

inversion of long period p waves from great earthquakes along subduction zones abstract long period p waves from subduction zone earthquakes in the moment range from 7 1027to 8 1029dyn cm are analyzed using an iterative deconvolution method in addition to discrete subevents which effectively contribute to the observed seismograms the long period component of the moment rate function is derived with the constraint that the total seismic moment is equal to the moment determined from long period surface waves it is shown that great earthquakes can be described by several subevents with a duration of about 10 s which changes little from earthquake to earthquake in the above moment range the long period component of the moment rate function becomes larger for a greater earthquake the greatest earthquakes of mw 9 additionally involve subevents with another duration scale much longer than 10 s it is also shown that the local stress drop is 1 order of magnitude larger than the stress drop averaged over the entire fault plane the constancy of the local stress drop as well as the average stress drop holds among various magnitudes of earthquakes these observations suggest an essential similarity in the mode of dislocation distribution

geochemistry and petrogenesis of the proterozoic bandal mafic rocks himachal pradesh nw himalaya the proterozoic bandal mafic rocks exposed in kullu rampur window lesser himalaya himachal pradesh indicate two distinct high ti and low ti magma types the high ti basalts are characterised by high tio2 2 wt ti y ti zr tio2 k2o and low rb sr ratios they are enriched in high field strength hfs elements nb zr ti relative to low field strength lfs incompatible elements k rb the low ti basalts are charactersied by low tio2 2 wt ti y ti zr and high rb sr and rb ba ratios quartz normative composition continental tholeiite characteristics with nb la less than 1 are some of the common factors of the two groups of the bandal mafic rocks the trace element concentrations and their ratios of the two groups of the basalts indicate that they have been derived from the asthenosphere at different depths low ti at shallow and high ti at deeper levels some of the chemical features like low mg cr ni high incompatible element concentrations especially ba light rare earth element lree enriched patterns point towards assimilation and fractional crystallisation afc process which may have played a significant role in the generation of these basalts furthermore the bandal mafic rocks apart from field settings are geochemically similar to other proterozoic mafic bodies like the rampur volcanics mandi darla volcanics garhwal volcanics and bhimtal bhowlai volcanics of the lesser himalaya this widespread proterozoic continental tholeiitic magmatism over an area of 170 000 km2 in the lesser himalaya provides an evidence of plume activity in the region

shifts in the source of the parana basalts through time magmatism occurred intermittently in the parana region of south america between 240 50 ma with the peak of magmatic activity between 138 126 ma comprising the parana continental flood basalts cfb detailed chemical subdivision of the parana basalts into six units allowed stratigraphic correlations to be made implying a northward migration of magmatism following the rifting of the south atlantic however 40ar 39ar ages do not uphold the chronostratigraphic nature of such magmatic units instead they indicate a southeastwards migration major elements extrapolated to 8 wt mgo are used to investigate changes in magma type with time and are interpreted in terms of parameters such as pressure depth of melting and the nature of the source region fertile refractory and water content the oldest parana unit originated by melting at the greatest depths 90 120 km shifting to shallow levels 30 60 km for the younger units accompanying this decrease in pressure the source material undergoing partial melting became progressively more refractory in major elements and also more hydrous this hydrous metasomatism occurred after major element depletion of the lithosphere at shallow levels the data is consistent with conductive heating of a stratified source region inferred to lie within the lithospheric mantle which is relatively fertile but anhydrous at depth and also appears to be younger in age than the relatively major element refractory hydrous lithosphere at shallower depths thus the interaction of asthenosphere and lithosphere can be determined within an integrated age tectonic and thermal framework

a new technique for obtaining high resolution pore pressure records in thick claystone aquitards and its use to determine in situ compressibility 1 laboratory tests are commonly used to determine properties vertical compressibility specific storage ss and vertical hydraulic conductivity kv of claystone aquitards however whether data representative of in situ conditions can be obtained from disturbed samples is questionable here we present a method to determine the in situ and ss of a thick sequence of cretaceous aged claystone by estimating the loading efficiency of a formation from pore pressure responses to barometric pressure fluctuations we installed 10 vibrating wire pressure transducers at different depths 25 325 m below ground in a thick claystone aquitard by placing them directly within the cement bentonite grout two years of continuous transducer records using this method appeared to provide pore pressure data with a resolution of better than one part in 105 equivalent to millimeter of hydraulic head change pore pressure responses to barometric pressure changes earth tides and precipitation events can be clearly identified and the barometric responses can be easily analyzed the resulting values of 0 6 0 93 2 5 10 7 to 2 2 10 6 kpa 1 and ss 2 6 10 5 to 4 5 10 6 m 1 all decrease with depth the results are comparable with the limited existing data for in situ estimates of ss and are as much as an order of magnitude smaller than laboratory estimates of ss for similar aquitard deposits our findings suggest that the fully grouted transducer method can provide an accurate and reliable means to monitor pore pressure changes and to determine in situ parameters for bedrock aquitard systems

role of subaerial volcanic rocks and mantle plumes in creation of south atlantic margins implications for salt tectonics and source rocks abstract seaward dipping reflectors sdrs represent flood basalts rapidly extruded during either rifting or initially subaerial sea floor spreading evaporites can form on this basaltic proto oceanic crust as in the afar triangle today evidence for sdrs in south atlantic deep water regions comes from proximity to the uniquely large parana etendeka volcanic province onshore the tristan and gough hot spots drilled volcanic rocks and seismic profiles showing sdr provinces more than 100 km wide as much as 7 km thick and thousands of kilometers long sdrs are clearest adjoining the aptian salt basins however we speculate that sdrs are also present but seismically obscured below the salt basins we argue that the conjugate aptian salt basins are post breakup not pre breakup they were separated from the start by a mid oceanic ridge distal salt accumulated on proto oceanic crust not rift basins this hypothesis is supported by seismic stratigraphy and structure magnetic anomalies plate reconstructions and hydrothermal potash evaporites an important implication for exploration is that thick basalts rather than rift age source rocks may underlie distal parts of the salt basins

alkaline rocks from continental brazil abstract the present literature review on brazilian alkaline rocks stresses mainly the petrographic and geologic aspects at least eight different rock associations are represented agewise four groups are found among southern brazilian outcrops an older one about 240 m y only that is still poorly known the massifs clustered around jacupiranga about 130 m y old a few occurrences 100 110 m y old tunas itapirapua and the youngest and most important one with an age spread from about 80 m y to about 53 m y recent research shows a clear tectonic control both on local and on regional scales of alkaline occurrences in southern brazil alkaline magmatism was set off by pre drift and drift activity and is at its onset geologically related to basaltic activity emplacement of many massifs is also locally controlled by old lineaments e g in the minas gerais goias belt as is emphasized by geophysical data on a petrographic and chronologic basis several alkaline provinces are distinguished in southern brazil preliminary data on the cambrian precambrian rocks from southern bahia state a province with undersaturated syenites and litchfieldites and from cratonic areas in northern brazil are also presented

fate and transport of dissolved methane and ethane in cretaceous shales of the williston basin canada baseline characteristics of dissolved methane ch4 and ethane c2h6 and their stable isotopes in thick low hydraulic conductivity cretaceous shales were determined using high resolution core profiling at four sites in the williston basin wb canada positive correlations with the conservative natural tracer cl reflected a lack of measureable production or consumption of gases in the shale to the depth investigated 150 m below ground bg and suggest ch4 and c2h6 concentrations near the interface with overlying quaternary sediments are controlled by lateral migration and dilution in permeable zones curvilinear increasing concentrations with depth in the shale at all sites coupled with 1 d solute transport modelling suggest long term over millions of years upward diffusion of ch4 and c2h6 from deeper wb sources likely the second white speckled shale formation swss 790 m bg 13c ch4 profiles in the shale are consistent with upward diffusional fractionation of isotopes from the swss distinct ch4 and c2h6 isotope values of gases in the shales vs 13c enriched thermogenic isotopic signatures of ch4 and c2h6 in deeper oil producing wb intervals could be used to identify fugitive gases originating deeper in the basin this article is protected by copyright all rights reserved

the radial diffusion method 1 using intact cores to determine isotopic composition chemistry and effective porosities for groundwater in aquitards a new method is described for the determination of the isotopic composition and chemistry of groundwater in aquitards the effective porosities for each component can be determined concurrently the method is based on diffusive exchange of water and solutes between groundwater in a cylindrical core of aquitard material and water in a reservoir placed along the axis of the cylinder the method was tested for 2h cl and so4in an aquitard consisting of clay rich glacial till the 2h in aquitard core samples as determined by radial diffusion agreed closely with 2h in groundwater obtained from corresponding piezometers installed in the aquitard for the concentrations of cl and so4 the agreement was less close but still satisfactory the effective porosities were equal to the total porosities for 2h and were less than the total porosities for cl and so4 ions

age petrogenesis and tectonic setting of the thessalon volcanic rocks huronian supergroup canada abstract the 2 5 ga huronian supergroup volcanic rocks in northern ontario represent one of the better preserved paleoproterozoic continental flood basalt sequences on earth the youngest age of huronian supergroup volcanism is refined to 2452 5 6 2 ma based on new u pb zircon analyses of the copper cliff rhyolite recent mapping and geochemical analyses of thessalon formation volcanic rocks define a well developed chemostratigraphy a lower series consisting of four geochemically distinct mafic lava sequences and an upper basalt andesite volcanic series these two mafic volcanic series are separated by felsic volcanic rocks rhyolite and dacite the mafic lavas are low ti tholeiites dominated by basalt and andesite and are characterized by enriched light rare earth element profiles and high th contents up to 12 ppm most basalt andesite sequences show some internal geochemical variation reflecting a combination of fractional crystallization and in some cases limited crustal contamination but each sequence represents a discrete magma batch derived by different degrees of partial melting in the subcontinental lithospheric mantle all magma batches display prominent negative nb ta and ti anomalies on primitive mantle normalized multi element diagrams interpreted to reflect melting of a heterogeneous and previously metasomatized garnet lherzolite that acquired some chemical characteristics of a source typical of subduction zone magmatism at least three distinct mantle source compositions are required to explain the range in the observed lava compositions the most unusual of these reservoirs has a number of geochemical features akin to upper continental crust and is characterized by high th yb 10 and low zr nb 11 this reservoir is interpreted to be peridotite modified through metasomatism and entrapment of arc magmas during northward neoarchean subduction along the southern superior craton margin

secondary rock structures and the regional hydrogeology of claystone rich cretaceous strata williston basin saskatchewan canada the geometry and spatial distribution of a polygonal fault system pfs and collapse features within cretaceous strata predominantly mudstones and claystones were investigated using three high resolution three dimensional seismic datasets of the williston basin saskatchewan canada mapping of the planform geometry and fault throw distributions throw depth t z profiling shows that the pfs present in the colorado group and pierre fm has a vertical extent of 200 330 m variation in the lateral planform geometry is attributed to the relative rates of stress accumulation during early development of the planar faults and is constrained using sequence stratigraphic principles the mean fault dip is 60 12 number of measurements n 225 the t z profiles appear as partial c type profiles demonstrating that at least half of the total height of the pfs was removed during post cretaceous erosion the presence of polygonal faults in equivalent strata of the western interior sedimentary basin wisb sug

coal quality coal rank variation and its relation to reconstructed overburden upper cretaceous and tertiary plains coals alberta canada near surface coals in the alberta plains occur in upper cretaceous and tertiary sediments the former represented by the belly river group horseshoe canyon formation and wapiti formation and the latter by the scollard member of the paskapoo formation statistical techniques were used to document both the distribution of and the interrelationships among the components of proximate and ultimate analysis and calorific value determinations the coals discussed range in rank from subbituminous c to high volatile bituminous c these coals are variable in ash content and low in sulfur content the relationships among calorific value dry basis in kj kg and ash dry basis in and calorific value moist mineral matter free basis in kj kg and equilibrium moisture meq in were determined to be cvd 29 677 315 17 ashd and cvmmmf 31 816 442 05 meq respectively the maximum depth of coal seam burial dob in m was reconstructed on the basis of previously published graphs relating the equilibrium moisture loss to depth of coal seam burial using the relationship log10meq 1 865 0 000416 dob a least squares regression analysis of calorific value mmmf basis in k kg on the calculated depth of burial dob in m yielded the equation cvmmmf 14 748 6 25 dob indicating a coalification gradient determined on the reconstructed overburden of 6 25 kj kg m 0 82 btu lb ft of depth or overburden near surface coals in the alberta plains increase in rank toward the west southwest toward the foothills and mountains region because of progressively greater amounts of overburden that existed in that direction during the tertiary erosion has since removed between 900 and 1 900 m 3 000 and 6 200 ft of sediment with the greatest amount of removal occurring in a west southwest direction

numerical studies of vertical cl δ2h and δ18o profiles in the aquifer aquitard system in the pearl river delta china sedimentation may have a significant effect on the transport of solutes and environmental isotopes in sediment the depth profiles of the cl 2h and 18o in a borehole in the aquifer aquitard system in the pearl river delta prd china were obtained by centrifuging the core sediment samples a one dimensional model based on the sedimentation and sea level changes of the prd during the holocene was built to investigate numerically the transport mechanisms of cl 2h and 18o the sedimentation process was modelled as a moving boundary problem with the moving rate equal to the sedimentation rate the model was calibrated and the parameters were obtained by comparing simulated and measured data very good agreement between all the three observed profiles and the simulated ones demonstrates the reliability of the model and the parameters simulation results show that the shapes of the curves are controlled by the combination of sedimentation and upper boundary conditions diffusion solely is adequate to reconstruct the observed profiles which indicates that diffusion is the dominant vertical transport mechanism the effective diffusion coefficients of the aquitard and the aquifer equal to 5 0 10 11 and 2 0 10 10 m2 s respectively the results of this study will help in understanding the transport mechanisms of solutes and environmental tracers in deltas with geology and hydrogeology similar to the prd copyright 2015 john wiley sons ltd

regional hydrogeochemistry of the carbonate rock aquifer southern manitoba middle ordovician to middle devonian carbonates in the manitoba lowlands form an extensive aquifer system along the eastern edge of the williston basin the aquifer is divided into fresh and saline portions by a series of topographic lows defined by major river systems and lakes that create a north south trending hydraulic divide east of this divide ca mg hco3 fresh waters are derived by active modern day recharge focused in the sandilands and interlake regions stable isotope and geochemical data indicate that na cl saline waters west of the divide are a mixture of original basin brines and glacial melt water pushed into the basin during pleistocene glaciation high na cl and cl br ratios are consistent with significant salt dissolution by glacial melt water

sm nd isotopic investigation of neoproterozoic and cretaceous igneous rocks from southern brazil a study of magmatic processes abstract nd evolutionary paths for diversified igneous suites from southern brazil are here re evaluated using published results we interpret the end paths considering the secondary fractionation of 147sm 144nd due to major petrogenetic processes the inclusion of nd isotopes and geochemical data for precambrian and mesozoic basic rocks allow improving the discussion on the subcontinental lithosphere beneath southern brazil late neoproterozoic rocks mostly granitoids are exposed in two regions of the southern brazilian shield an eastern collisional belt and a western foreland the latter included two geotectonic domains amalgamated at this time the sao gabriel arc 900 700 ma and the taquarembo cratonic block magma genesis mainly involved mixture of crustal and incompatible element enriched mantle components both with a long residence time continental segments are the neoarchaean paleoproterozoic lower crust ca 2 55 ga in the western foreland and paleoproterozoic neoproterozoic recycled crust 2 1 0 8 ga in the collisional belt granitoids with a single crustal derivation are limited in the southern brazilian shield mixing processes are well registered in the western foreland where the re enriched old mantle was probably mixed with a 900 700 ma old subducted lithosphere and a 2 55 ga old lower crust the contribution of the latter increased from the early 605 580 ma to the later 575 550 ma neoproterozoic events which may be due either to crustal thickening or to delamination of the lithosphere magma sources were diversified in the 660 630 ma collisional belt initially they involved the mixing between two components with similar nd isotopic ratios a 2 1 0 8 ga old recycled crust and a subduction processed old mantle regional heating and abundant production of granitic melts with diversified contribution of enriched mantle components mark the end of the collisional period at 630 580 ma we can also attribute this to the delamination of the lithosphere so that the same geodynamic process may explain the magmatism in the whole shield at the end of the dom feliciano orogeny mesozoic rocks include flood basalts from the cretaceous parana province and sub coeval alkalic suites multiple processes of metasomatism affected the lithospheric mantle resulting in some complexity but they mainly register two enriched mantle components both generated during neoarchaean paleoproterozoic events one end member has a more pronounced subduction signature the other one probably resulted from the re enrichment of the first component at the end of the camboriu collisional orogeny 2 0 ga

predicted tortuosity of muds tortuosity figures prominently in geochemical hydrological and geophysical calculations concerned with sediments but it is a difficult parameter to measure past theoretical models for predicting the tortuosity from porosity data do not work with marine muds and scientists and engineers have had to resort to entirely empirical models without a mechanistic explanation and with unknown predictive power we offer the first geometric model for the dependence of tortuosity on porosity in marine muds the model is based on the tortuosity of separated layers of nonoverlapping disks the fitted geometric constant in this model indicates that natural marine sediments act as if their fabric were made of disks with thickness diameter ratios very close to 1 2 which indicates a blocklike fabric with respect to diffusion the model was also applied to predict the tortuosity of a variety of sediments and soils not in the original database and it provides a satisfactory prediction of the mean trend in these data

shallow faults upper cretaceous clinoforms and the colonsay collapse saskatchewan reflection seismic data in the vicinity of the colonsay potash mine near saskatoon saskatchewan reveal numerous shallow normal faults with vertical displacements of as much as 25 m the faults cut the glacial deposits and upper cretaceous rocks to a maximum depth of about 400 m horizontal length ranges from a few hundred to a few thousand metres similar faults are also exposed in several widely separated open pit coal mines of southern saskatchewan and may be common elsewhere in the prairies such faulting is considered to be a result of tertiary to quaternary extensional tectonics and may have been aided in this region by the melting of gas hydrates the study area includes the east flank of the colonsay collapse a subsidence structure caused by dissolution and removal of salt in the 200 m thick devonian prairie evaporite formation salt was removed in two stages prior to or during early glacial time and in late glacial time subsidence was gradual with no observable faulting a complex of clinofor

evidence of magmatic activity related to middle jurassic and lower cretaceous rifting from northeastern brazil ceara mirim k ar age palaeomagnetism petrology and sr 1bnd isotope characteristics the mesozoic magmatic activity in the easternmost part of ne brazil ceara mirim is mainly represented by two pyroxene tholeiitic dykes only few dykes have alkaline character k ar ages and palaeomagnetism data indicate that ceara mirim dykes are of middle jurassic 175 160 ma and early cretaceous 140 130 ma age both middle jurassic and lower cretaceous dykes have high incompatible element concentrations and tio2 with the lower contents generally confined to the middle jurassic dykes rare tholeiitic dykes low in tio2 and incompatible elements are present sr 1bnd isotopic and other chemical data do not support appreciable crustal contamination and in a 87sr86sr vs 143nd144nd diagram almost all the dykes plot in a narrow area of the enriched quadrant of the mantle array tholeiitic and alkaline ceara mirim dykes are related to different parent magmas probably originating by different degrees of melting of garnet peridotite mantle sources characterized by distinct sr 1bnd isotope compositions and small scale chemical heterogeneities ceara mirim tholeiitic dykes show close mineralogical chemical and isotopic similarities with the lower cretaceous high tio2 tholeiites from maranhao sardinha intrusives and parana northern province basins in general chemical and sr 1bnd isotope data for high and low tio2 brazilian mesozoic tholeiites appear to be related to time integrated enriched and depleted mantle components respectively subcontinental mantle heterogeneity is believed to be due to variable enriched components related to metasomatic processes the ceara mirim jurassic dykes correlate well in terms of composition and tectonic setting with the analogue tholeiitic dyke swarms from the benue trough and can be related to the opening of the central atlantic ocean the lower cretaceous ceara mirim magmatic activity corresponds to the coeval one of the benue trough and can be related to the early rifting events responsible for the opening of the equatorial domain of the south atlantic whose oceanic crust formed between 120 and 100 ma

precambrian iron formations from the cauvery suture zone southern india implications for sub marine hydrothermal origin in neoarchean and neoproterozoic convergent margin settings abstract thick horizons of iron formations including banded iron formations bifs and banded silicate formations bsfs occur as e w trending bands in the eastern part of cauvery suture zone csz in the sothern granulite terrane of india some of these occur in close association with the neoarchean neoproterozoic suprasubduction zone complexes where as some others are associated with metamorphosed accretionary sequences including pyroxene granulites and other high grade rocks the iron formations are highly deformed and metamorphosed under amphibolite to granulite facies conditions and are composed of quartz magnetite hematite goethite garnet pyrite together with grunerite and pyroxene here we report the geochemical characteristics of twenty representative samples from the iron formations that reveal a widely varying composition with fe 2 o 3 t 22 65 wt as total iron total fe 2 o 3 tio 2 205 6532 mno tio 2 0 25 12 66 and sio 2 33 85 wt broadly representing the two types of iron formations these formations also show very low al al fe mn ratio 0 001 0 01 al 2 o 3 0 07 0 76 wt al 2 o 3 tio 2 ratio 2 7 21 mgo 0 01 4 41 wt cao 0 1 1 24 wt na 2 o 0 01 0 05 wt and k 2 o 0 01 wt together with low total ree 3 38 31 63 ppm the trace and ree elemental distributions show wide variation with high ni 274 ppm and zn contents up to 87 ppm when compared to mafic volcanics of the adjoining areas tectonic discrimination plots indicate that the iron formations of the cauvery suture zone are of hydrothermal origin their chondrite normalized patterns show slight positive eu anomaly eu eu up to 1 77 and relatively less fractionation of ree with slight lree enrichment compared to hree however the paas post archean average of australian sediments normalized ree patterns display significant positive eu anomaly eu eu up to 2 32 with well represented negative ce anomalies ce ce 0 66 1 28 the above results together with petrological characteristics and available geochronology of the associated lithologies suggest that the iron formations can be correlated to algoma type the fe and si were largely supplied by medium to high temperature sub marine hydrothermal systems in neoarchean and neoproterozoic convergent margin settings

economic geology of southern saskatchewan potash mines abstract canadian commercial potash deposits are located in the southern saskatchewan area of a middle devonian evaporite basin that extends across western canada and into adjacent areas of northeastern montana and western north dakota there are eleven mines in saskatchewan that annually produce approximately 23 mt of kcl from halite sylvite ore associated with the 60 m thick upper interval of the prairie evaporite formation of these eight mines are conventional underground operations at 900 1100 m depths solution mining is used at three sites where the ore is buried to 1500 m depth or where this methodology was a necessary remedial action responding to flooding of an underground dry mine two new underground mines are currently under construction the prairie evaporite formation accumulated during the middle devonian along an evaporating equatorial inland sea that extended onto the laurentia paleocontinent development of a 400 km long reef at the northern seaward end barred the basin permitting accumulation of up to 200 m of halite dominated evaporite beds across north central alberta southern saskatchewan and into adjacent areas of the united states late cycle potassium rich brines concentrated within the southern saskatchewan sub basin resulting in accumulation of potash ore zones as the uppermost interval of the 100 200 m thick halite anhydrite deposit early diagenetic processes resulted in widespread concentration of sylvite rich beds upon leaching of mg chloride from carnallite rich deposits resulting in commercially attractive potash ore subsequent post burial dissolution of halite dominated beds occurred across large areas of alberta and southern saskatchewan including portions of the potash mining districts natural dissolution collapse subsidence structures up to 10 s km long may have permitted some mining areas to be in contact with basin brines brines may have also mixed with descending groundwater sourced from cretaceous strata up section if the carbonate seals of the overlying dawson bay formation were compromised by fracturing mining methodologies are designed to minimize the mine scale subsidence upon ore removal and limit potential fracturing of overlying dawson bay limestone beds brine seeps into the underground mines vary from controllable nuisances to catastrophic flooding of underground workings remedial actions such as grouting generally control the seeps but uncontrollable ingress has resulted in one underground operation being converted into a solution mine

physical and chemical constraints on the evolution of the columbia river basalt physical and chemical constraints require that columbia river basalt flows were fed from a large 700 km 3 magma reservoir near the crust mantle boundary and prohibit significant crystal fractionation or crustal assimilation between reservoir and surface demonstrable fractionation of plagioclase olivine pyroxene in the reservoir largely obviates the need for an unusual iron rich pyroxenite source variation of sr and nd isotope ratios with age in the main series of columbia river basalt and variation in such incompatible trace element ratios as ba p suggest lower crustal assimilation at the top of the reservoir combined with crystal fractionation however decoupling between isotope ratios and incompatible element ratios implies two separate processes in addition to crystal fractionation of which lower crustal assimilation may be one the other process may involve the participation of a vertically heterogeneous mantle resulting from metasomatism in the continental lithosphere

chloride and chlorine isotopes 36cl and δ37cl as tracers of solute migration in a thick clay rich aquitard system detailed vertical profiles of dissolved cl and its isotopes 36cl and 37cl provided new information on the origin and systematics of this conservative tracer in pore waters of a thick aquitard system the aquitard system consists of surficial quaternary clay rich till 80 m thick deposited 30 20 kyr b p overlying cretaceous marine clay 76 m thick deposited 71 ma the distribution of cl 37cl and br showed the presence of five distinct end members for cl the top of the unoxidized till a regional aquifer underlying the cretaceous clay two localized geological heterogeneities sand streaks in the till and glacial meltwater emplaced with the till and still present at depths of between 36 and 60 m numerical simulations of the transport of cl from the sand streaks indicated that this geochemical profile has been developing throughout most of the holocene the 36cl measurements showed that the age of the dissolved cl in the upper cretaceous clay is likely between 0 75 and 1 9 myr the 36cl measurements further suggested that the dissolved cl in the till was not directly derived from the underlying cretaceous clay finally it was not possible to quantify the effects of isotopic fractionation of 37cl relative to 35cl because of diffusion in this aquitard system

numerical reconstruction of a soft bedded laurentide ice sheet during the last glacial maximum we used a numerical ice sheet model to reconstruct the north american laurentide ice sheet during the last glacial maximum our model simulates ice sheet conditions that can be specified experimentally as either a rigid substrate hard bed or a wet deformable till soft bed basal sliding is excluded we use geologic records of former basal ice sheet processes to prescribe the distribution of hard and soft beds our reconstruction of the laurentide ice sheet is significantly lower in ice surface height and contains less ice volume than the climap maximum reconstruction in contrast our reconstruction agrees well with the ice 4g reconstruction both in height and volume because the ice 4g reconstruction is based on the inversion of relative sea level data whereas our reconstruction is based on glacial geology and ice mechanics this agreement suggests that soft beds provide a glaciological mechanism to explain the shape and volume of the laurentide ice sheet that is most consistent with observations of relative sea level change and other geodynamic considerations

geochronology of age progressive volcanism of the oregon high lava plains implications for the plume interpretation of yellowstone 1 the high lava plains province hlp is a late cenozoic bimodal volcanic field at the northern margin of the basin and range province in southeastern oregon that hosts a westward younging trend of silicic volcanism that crudely mirrors northeastward migration of silicic volcanism along the yellowstone snake river plain ysrp trend we present 40ar 39ar ages for 19 rhyolite domes 5 rhyolite ash flow tuffs and 34 basaltic lavas from the hlp the previously identified trend of westward migration of hlp rhyolites is confirmed the rate of propagation is 33 km m y from 10 to 5 ma slowing to 13 km m y after 5 ma the duration of silicic volcanism at any locus is 2 m y three older hlp dacite domes yielded ages of 15 5 ma basalts are not age progressive we identify several episodes of increased basaltic activity at 7 5 7 8 5 3 5 9 and 2 3 ma with the younger episode likely continuing into the recent the hlp and ysrp trends emerged from the axis of middle miocene basaltic volcanism of the columbia river and steens basalts we propose a model in which 1 miocene flood basalts and widespread silicic rocks are the result of emplacement of a plume head near the craton margin enhanced by flow up a topographic gradient along the base of the lithosphere at the craton margin 2 the hlp trend is the result of westward flow originating at the craton margin and 3 the ysrp trend is the trace of the motion of the north american plate over the tail of the plume

reversal of the regional scale flow system of the williston basin in response to pleistocene glaciation low 18o values of formation waters collapse structures related to salt dissolution hydrodynamic blowout structures and biodegradation of oils all suggest a significant influx of fresh water into the williston basin along the outcrop belt in southern and central manitoba during pleistocene glaciation the thickness of the continental ice sheet over manitoba would have provided sufficient potentiometric drive to reverse the regional scale flow system of the williston basin the dynamic nature of the flow system suggests that modern day pressure distributions may not be good proxies for ancient petroleum migration pathways as is commonly assumed

an inversion approach to assimilation and fractional crystallisation processes a numerical inversion program has been developed to investigate isotope and trace element variations in suites of related rocks in terms of assimilation and fractional crystallisation processes major element compositions constrain the degree of fractionation and the program may be used to calculate the isotope and trace element composition of either the crustal contaminant or of the parental magmas once the contaminant is known the ratio of the rate of assimilation to the rate of fractional crystallisation and the bulk partition coefficients can be varied with changes in magma composition the approach is illustrated with a suite of calc alkaline rocks from the cerro galan centre in nw argentina and a suite of continental flood basalts from the southern parana in brazil both exhibit striking increases in 87sr 86sr with increasing sio2 consistent with progressive contamination during differentiation within the continental crust in detail both suites contain a subset of samples which have undergone relatively little contamination and a subset characterised by relatively high sio2 and 87sr 86sr reflecting larger crustal contributions individual samples within the more contaminated subset can be modelled in terms of assimilation with fractional crystallisation afc processes although no clear progressively contaminated liquid lines of descent are preserved at both cerro galan and the southern parana the associated dacites and rhyodacites appear to have similar compositions to the crustal contaminants thus the inversion program has been used to investigate the amount of contamination the relationship between the amount of contamination and the amount of crystals removed by fractional crystallisation and the isotope and trace element contents of the parental magmas prior to afc the latter are estimated to have had 87sr 86sr 0 7055 and 143nd 144nd 0 51256 at cerro galan and 0 7090 and 0 51226 respectively in the southern parana

geochemical modeling of the madison aquifer in parts of montana wyoming and south dakota stable isotope data for dissolved carbonate sulfate and sulfide are combined with water compo sition data to construct geochemical reaction models along eight flow paths in the madison aquifer in parts of wyoming montana and south dakota the sulfur isotope data are treated as an isotope dilution problem whereas the carbon isotope data are treated as rayleigh distillations all reaction models reproduce the observed chemical and carbon and sulfur isotopic composition of the final waters and are partially validated by predicting the observed carbon and sulfur isotopic compositions of dolomite and anhydrite from the madison limestone the geochemical reaction models indicate that the dominant groundwater reaction in the madison aquifer is dedolomitization calcite precipita tion and dolomite dissolution driven by anhydrite dissolution sulfate reduction ca mg2 ina cation exchange and halite dissolution are locally important particularly in central montana the groundwater system is treated as closed to c02 gas from external sources such as the soil zone or cross formational leakage but open to c02 from oxidation of organic matter coupled with sulfate reduction and other redox processes occurring within the aquifer the computed mineral mass transfers and modeled sulfur isotopic composition of madison anhydrites are mapped throughout the study area carbon 14 groundwater ages adjusted for the modeled carbon mass transfer range from modem to about 23 000 years b p and indicate flow velocities of 7 7 ftlyr 2 1 26 5 rnlyr most horizontal hydraulic conductivities calculated from darcy s law using the average 14 c flow velocities are within a factor of 5 of those based on digital simulation the calculated mineral mass transfer and adjusted 14 c groundwater ages permit determination of apparent rates of reaction in the aquifer the apparent rate of organic matter oxidation is typically 0 12 jlidol uyr sulfate and to a lesser extent ferric iron are the predominant electron acceptors the kinetic biochemical fractionation of 34 s between sulfate and hydrogen sulfide is approximately 44 o at 25 c with a temperature variation of

the 1992 nicaragua earthquake a slow tsunami earthquake associated with subducted sediments the 1992 nicaragua earthquake was a tsunami earthquake that is it generated tsunamis disproportionately large for its surface wave magnitude m s the moment magnitude m w determined from long period 250 s surface waves was 7 6 significantly larger than the 20 s m s of 7 this m s m w disparity is also characteristic of tsunami earthquakes the nicaragua earthquake is the first tsunami earthquake to be captured by modern broadband seismic networks allowing us to present here seismograms of sufficiently high quality to make inferences about the rupture mechanisms we conclude that the nicaragua earthquake was a slow thrust earthquake which occurred on the subduction interface between the cocos and north american plates and because of the absence of sediments on the trench floor offshore of nicaragua the slip propagated up dip all the way to the ocean bottom exciting large tsunamis the occurrence of slip on a plate interface filled with soft subducted sediments caused the rupture process to be slower than in ordinary subduction zone thrust earthquakes our results reinforce the idea that tsunami warning systems using long period 100 s waves are necessary to reduce the hazard from this type of earthquake

magmatism and continental break up in the south atlantic high precision40ar 39ar geochronology abstract a detailed ar ar study of the parana etendeka continental flood basalts cfb has been undertaken using laser spot analysis data provide information not only on the age of the samples but also on the variability of the non radiogenic ar component and state of alteration the results indicate the parana etendeka cfb were erupted over 10 million years between 137 and 127 ma providing a minimum overall eruption rate of 0 1 km3 yr 1 this is an order of magnitude less than that previously proposed for this the deccan and siberian cfb provinces but it is similar to estimates for hawaii iceland and the columbia river cfb in detail the new ar ar analyses indicate that magmatism within the parana etendeka province migrated from nw to se prior to and during the opening of the south atlantic providing an explanation for the asymmetry of the cfb lavas about the south atlantic moreover chemically defined magma types were erupted at different times in different places and so within the paranathey may not be used as reliable chronostratigraphic units rather such magmatic units may reflect the extent of compositionally distinct source regions in the uppermost mantle and indicate that partial melting took place over a wide area under the paranabasin the nw se migration of the onset of magmatism might be interpreted as a plume trace but the inferred rate of movement is 3 times faster than that inferred from subsequent magmatism on the rio grande rise it is argued that the onset of magmatism reflected extensional tectonics normal to the ponta grossa dyke swarm given that magmatism preceded the main phase of rifting and that extension across the ponta grossa was moderate current plume models have difficulty in predicting sufficient melting within the asthenosphere

origin age and movement of pore water in argillaceous quaternary deposits at four sites in southwestern ontario hydrogeologic information in the form of textural properties field and laboratory determined hydraulic conductivity values vertical hydraulic gradients from piezometer nests and major ion and isotopic contents 18o 2h 3h 13c 14c was obtained from four sites located in southwestern ontario on thick deposits of clayey till and glaciolacustrine clay at each site the piezometers were installed from the water table zone situated 1 4 m below the surface to a maximum depth between 20 and 35 m below the surface values of hydraulic conductivity determined in the laboratory by consolidometer and triaxial methods are in the order of 10 8 10 7 cm s and are similar to values calculated from rates of water level rise in piezometers mean values of average vertical groundwater velocity calculated with the measured values of hydraulic conductivity porosity and hydraulic gradient using the darcy equation for a saturated non fractured porous medium range from 0 13 to 0 26 cm yr tritiated pore waters only occur within 3 6 m of ground surface thereby indicating that groundwaters below this depth recharged prior to at least 1952 18o in the pore waters exhibit a distinctive regular shift with depth from water table values of 9 to 10 smow characteristic of present day precipitation to values between 14 and 17 at depths of 20 40 m which are characteristic of much cooler waters corrected 14c ages of the groundwater are greater than 8000 yr b p thereby suggesting that the groundwaters at depth entered these deposits during or after the formation of these deposits approximately 11 000 to 14 000 yr ago 18o 2h and cl concentration profiles were simulated with a one dimensional model for transport by advection and diffusion in a saturated porous medium reasonable agreement between the model and the field profiles was obtained with values of effective diffusion coefficients of 3 0 10 6 cm2 s for 18o 2h and cl and with groundwater velocities between 0 03 to 0 05 cm yr based on these results it is concluded that the pore water in these deposits is a mixture of late pleistocene and modern waters and that the distribution of 18c 2h and cl in these deposits is influenced predominantly by molecular diffusion apparently more so than by hydraulic flow

the petrogenesis of brines in devonian potash deposits of western canada abstract recent mine level floods in some potash mines in the elk point basin of saskatchewan canada have demonstrated the need to identify accurately the source of water leaks so as to assist in remedial or preventative action most chemical constituents of the waters are inadequate tracers of the origin of these leaks because the concentrations of most elements change substantially during migration of the fluids to the mining level in marked contrast to most of the chemical constituents dissolved in the water oxygen and hydrogen isotopes are conservative elements of the water within the elk point basin d and 18 o values of basinal waters normally increase with depth because of mixing between trapped formation waters and local surface waters such that the water in each aquifer within the basin generally has a unique isotopic composition floodwaters in the potash mines of saskatchewan have chemical and stable isotopic compositions that indicate three different origins for mine level fluids 1 halite and sylvite saturated basinal brines from devonian formations directly above the deposits which are predominantly connate waters 2 undersaturated waters of predominantly meteoric origin from stratigraphically higher aquifers such as the cretaceous mannville group and 3 ca rich brines that may represent devonian fluids associated with recrystallization of the evaporites the salt undersaturated formation waters most likely are directed to lower stratigraphic units through collapse structures or related features which may be reactivated through mining

circum pacific seismic potential 1989 1999 the seismic potential for 96 segments of simple plate boundaries around the circum pacific region is presented in terms of the conditional probability for the occurrence of either large or great interplate earthquakes during the next 5 10 and 20 years i e 1989 1994 1989 1999 and 1989 2009 this study represents the first probabilistic summary of seismic potential on this scale and involves the comparison of plate boundary segments that exhibit varying recurrence times magnitudes and tectonic regimes presenting these data in a probabilistic framework provides a basis for the uniform comparison of seismic hazard between these differing fault segments as well as accounting for individual variations in recurrence time along a specific fault segment and uncertainties in the determination of the average recurrence time

natural tracer profiles across argillaceous formations argillaceous formations generally act as aquitards because of their low hydraulic conductivities this property together with the large retention capacity of clays for cationic contaminants has brought argillaceous formations into focus as potential host rocks for the geological disposal of radioactive and other waste in several countries programmes are under way to characterise the detailed transport properties of such formations at depth in this context the interpretation of profiles of natural tracers in pore waters across the formations can give valuable information about the large scale and long term transport behaviour of these formations here tracer profile data obtained by various methods of pore water extraction for nine sites in central europe are compiled data at each site comprise some or all of the conservative tracers anions cl br water isotopes delta 18 o delta 2 h and noble gases mainly he based on a careful evaluation of the palaeo hydrogeological evolution at each site model scenarios are derived for initial and boundary pore water compositions and an attempt is made to numerically reproduce the observed tracer distributions in a consistent way for all tracers and sites using transport parameters derived from laboratory or in situ tests the comprehensive results from this project have been reported in mazurek et al 2009 here the results for three sites are presented in detail but the conclusions are based on model interpretations of the entire data set in essentially all cases the shapes of the profiles can be explained by diffusion acting as the dominant transport process over periods of several thousands to several millions of years and at the length scales of the profiles transport by advection has a negligible influence on the observed profiles at most sites as can be shown by estimating the maximum advection velocities that still give acceptable fits of the model with the data the advantages and disadvantages of different conservative tracers are also assessed the anion cl is well suited as a natural tracer in aquitards because its concentration varies considerably in environmental waters it can easily be measured although the uncertainty regarding the fraction of the pore space that is accessible to anions in clays remains an issue the stable water isotopes are also well suited but they are more difficult to measure and their values generally exhibit a smaller relative range of variation chlorine isotopes delta 37 cl and he are more difficult to interpret because initial and boundary conditions cannot easily be constrained by independent evidence it is also shown that the existence of perturbing events such as the activation of aquifers due to uplift and erosion leading to relatively sharp changes of boundary conditions can be considered as a pre requisite to obtain well interpretable tracer signatures on the other hand gradual changes of boundary conditions are more difficult to parameterise and so may preclude a clear interpretation

3 d 40ar39ar geochronology in the parana continental flood basalt province new 40ar39ar analyses of borehole samples from the parana etendeka continental flood basalt province provide critical evidence of eruption rates in unexposed regions when combined with surface samples the new data clarify the duration of this major volcanic province new ages from both surface and borehole samples confirm a 10 12 million year duration of magmatism which post dates the tithonian mass extinction and provide a unique 3 dimensional picture of the spatial and temporal eruption of the lava pile chemically defined magma types are diachronous and the onset of magmatism occurred 500 1000 km inland migrating southeast towards the incipient south atlantic ocean calculated eruption rates increased from 0 03 km3 yr 1 between 138 and 135 ma through 0 13 km3 yr 1 between 135 and 133 ma to 0 21 km3 yr 1 between 133 and 131 ma supporting the notion that the rate of magmatism increased with time and proximity to the developing south atlantic after 131 ma the continental eruption rates dropped dramatically to 0 01 km3 yr 1 presumably because rifting had occurred and eruption centred in the oceanic rio grande rise with eruption rates of around 0 3 0 5 km3 yr 1 given the available constraints on the potential temperature of the plume thickness of the continental lithosphere and degrees of extension through time predicted melt production rates within the plume seriously underestimate the calculated eruption rates on the continent however the eruption rates can be reconciled if melting occurred by conductive heating of volatile enriched mantle the diachronous nature of the magma types supports the idea that melting occurred over a wide area and that the different magma types reflect different source regions rather than the temporal evolution of magmas from a single source given that 10 million years is appropriate to the timescales for conductive heating above the mantle plume it is suggested that these distinct source regions were located within the lithospheric mantle consistent with geochemical studies

a study of clay pore water and sporopollens for characterizing paleoenvironments in the hebei plain northern china abstract we developed a clay pore water cpw isotopic method for tracing paleoenvironments characterized by sporopollens the thick clayey layers have the advantage of preserving pore water regardless of whether the water is inherent in the clayey layers or not therefore the clayey layers are a suitable target from which paleoenvironmental information can be extracted sediment sporopollens as well as cpw deuterium and oxygen isotopes were investigated in drilling cores obtained from a 130 m borehole at a field site in hengshui in the north china plain our interpretation of 18 o in cpw was consistent with sporopollens climate indices indicating that cpw was an effective proxy for obtaining paleoenvironmental information sporopollens species were abundant in the cores but the quantity of each species was low furthermore mean annual temperature and precipitation curves were established using a pollen climatic response surface model the results indicated two warm humid periods 5 2 0 m 22 6 11 m and one cold dry period 8 8 6 4 m in the holocene as well as two warm humid periods 90 6 83 m 110 6 108 2 m and three cold dry periods approximately 40 m 66 4 56 8 m approximately 100 m in the late pleistocene data derived from the sporopollens and cpw cumulatively elucidate the environmental change in northern china

mantle hotspots plumes and regional tectonics as causes of intraplate magmatism in continental areas it is often difficult to determine the cause of intraplate magmatism large volumes of magma high eruption rates and the presence of a hotspot trace on the adjacent ocean floor are all evidence for the presence of an anomalously hot mantle however in many continental magmas there are chemical variations with time which are inferred to reflect changes from asthenospheric to predominantly lithospheric source regions or vice versa it is argued that these chemical characteristics constrain whether magmatism was triggered by the emplacement of a mantle plume or by lithospheric extension

paleohydrogeology of the cretaceous sediments of the williston basin using stable isotopes of water 1 hydraulic and isotopic data collected from aquifers are routinely used to characterize hydrogeological conditions within sedimentary basins but similar data from confining units are generally not collected despite their ability to provide insights on important water solute transport controls we characterized paleogroundwater flow and solute transport mechanisms across 384 m of cretaceous shale aquitard in the williston basin canada using high resolution depth profiles of water isotopes 18o 2h water samples were also collected from wells installed in the underlying regional sandy aquifer mannville fm 93 m thick and from seepage inflows into potash mine shafts to 825 m below ground the 1 d numerical transport modeling of 18o profiles provided insight into large scale long term solute transport in both cretaceous sediments and the basin despite the potential for significant advective migration during glaciations molecular diffusion appears to be the dominant solute transport mechanism through the aquitard simulations suggest average vertical groundwater velocities of 0 05 m 10 ka and an average excess hydraulic head of 10 m these values are much less than anticipated by successive glaciations the dominant paleoevent reflected in present day profiles is introduction during the pleistocene of glaciogenic meteoric water to the aquifer underlying the shale likely along an aquifer outcrop area east of the site or through local vertical conduits simulations suggest these recharge events occurred during one or more glacial periods the isotopic profile over the upper 25 m of pleistocene till and shale is consistent with glacial deposition and transport processes within these units over the holocene past 10 ka

subglacial recharge into the western canada sedimentary basin impact of pleistocene glaciation on basin hydrodynamics brine springs discharging from devonian carbonates of the western canada sedimentary basin have distinct water chemistry from brines in laterally equivalent units deeper in the basin stable isotope data suggest that the brine springs originated as pleistocene meltwater these waters are interpreted to originate as an influx of subglacial meltwater related to a reversal of the basin scale flow system caused by the overriding ice sheet esker distribution shows a notable relationship between shield and sedimentary rocks an integrated sedimentary basin ice sheet model supports the interpretation that high permeability carbonate units acted as preferential subglacial drains that in turn affected esker development the fluid flow history of the western canada sedimentary basin is characterized by back and forth movement through geological time in response to changing boundary conditions modern day flow systems may not then be indicative of historic movement of economic fluids through the basin

geochemical evolution and residence time of porewater in low permeability rocks of the michigan basin southwest ontario abstract drill cores collected from an 860 m thick paleozoic cambrian to devonian sedimentary sequence of the michigan basin in southwest ontario canada were used to develop vertical profiles of natural tracers in porewater from the sedimentary sequence and build a conceptual model regarding processes and timing of solute migration in this paper the conceptual model is quantitatively assessed with numerical simulations of diffusion dominated solute transport cl and 18o the conceptual model suggests that the tracer profiles result from mixing between a deep shield brine with isotopic characteristics consistent with water rock interaction over a long period of geologic time ordovician seawater at intermediate depth and an overlying hypersaline brine formed by evaporation of seawater in a restricted basin during the silurian between the peak of basin consolidation at 300 ma bp and the pleistocene 2 6 ma bp salinity and isotopic concentration gradients are thought to have driven mixing dominantly by diffusion water isotope data indicate that in the pleistocene melt water infiltrated to a maximum depth of 330 m in the silurian salina formation likely in response to transient glacial loading and elevated sub glacial hydraulic pressures also in the pleistocene over pressured conditions in deep regions of the basin drove high salinity brine eastward in the basal cambrian aquifer interrupting pre existing tracer diffusion profiles a base case set of boundary and initial conditions provides a good fit between simulated and measured tracer profiles but requires effective diffusion coefficients de in the ordovician limestones that are lower than the average values obtained in laboratory measurements by as much as a factor of 10 the base case values are still within the overall range of measured values at the formation scale relatively low in situ de values are attributed to the intermittent occurrence of gas and liquid hydrocarbons in the ordovician carbonate units and the effect of lithostatic confining pressure neither of which are accounted for in the laboratory measurements but both would have the effect of decreasing de for aqueous solutes the numerical model is most sensitive to the formation specific de values and geologically reasonable variations in initial and boundary conditions have a relatively small influence on the results additional simulations indicate that hydraulic disturbance and ingress of meltwater during the pleistocene can explain second order features observed in the measured tracer profiles this work provides supporting evidence for previous research indicating that the porewater residence time in the ordovician sequence approaches the age of the rocks

the extent and chronology of cenozoic global glaciation abstract the quaternary is synonymous with extensive glaciation of earth s mid and high latitudes although there were local precursors significant glaciation began in the latest eocene ca 35 ma in eastern antarctica it was followed by glaciation in mountain areas through the miocene in alaska greenland iceland and patagonia later in the pliocene e g in the bolivian andes and possibly in tasmania and in the earliest pleistocene e g in the alps new zealand iceland and greenland today evidence from both the land and the ocean floors demonstrates that the major continental glaciations outside the polar regions rather than occurring throughout the 2 6 ma of the quaternary were markedly restricted to the last 1 ma 800 ka or less marine isotope stage mis 22 ca 870 880 ka included the first of the major worldwide events with substantial ice volumes that typify the later pleistocene glaciations i e mis 16 12 10 6 4 2

pleistocene hydrology of north america the role of ice sheets in reorganizing groundwater flow systems 1 while the geomorphic consequences of pleistocene megafloods have been known for some time it has been only in the past 2 decades that hydrogeologists and glaciologists alike have begun to appreciate the important impact that ice sheet aquifer interactions have had in controlling subsurface flow patterns recharge rates and the distribution of fresh water in confined aquifer systems across north america in this paper we document the numerous lines of geochemical isotopic and geomechanical evidence of ice sheet hydrogeology across north america we also review the mechanical thermal and hydrologic processes that control subsurface fluid migration beneath ice sheets finite element models of subsurface fluid flow permafrost formation and ice sheet loading are presented to investigate the coupled nature of transport processes during glaciation deglaciation these indicate that recharge rates as high as 10 times modern values occurred as the laurentide ice sheet overran the margins of sedimentary basins the effects of ice sheet loading and permafrost formation result in complex transient flow patterns within aquifers and confining units alike using geochemical and environmental isotopic data we estimate that the volume of glacial meltwater emplaced at the margins of sedimentary basins overrun by the laurentide ice sheet totals about 3 7 104 km3 which is about 0 2 of the volume of the laurentide ice sheet subglacial infiltration estimates based on continental scale hydrologic models are even higher 5 10 of meltwater generated these studies in sum call into question the widely held notion that groundwater flow patterns within confined aquifer systems are controlled primarily by the water table configuration during the pleistocene rather groundwater flow patterns were likely much more complex and transient in nature than has previously been thought because pleistocene recharge rates are believed to be highly variable these studies have profound implications for water resource managers charged with determining sustainable pumping rates from confined aquifers that host ice sheet meltwater

volumetrically significant recharge of pleistocene glacial meltwaters into epicratonic basins constraints imposed by solute mass balances melting of kilometer thick continental ice sheets during pleistocene glaciation profoundly altered regional scale groundwater flow in the low lying stable interior of the north american craton in this paper we show that large volumes of glacial meltwater penetrated to great depths in underlying sedimentary basins through regionally extensive silurian devonian carbonate aquifers disrupting relatively stagnant saline fluids and creating a strong disequilibrium pattern in fluid salinity these dilute isotopically light meteoric waters migrated into overlying fractured organic rich upper devonian shales and significantly enhanced microbial methanogenesis generating a unique class of natural gas deposits along the shallow basin margins new data on formation water chemistry of upper devonian antrim shale gas wells along the northern and western margins of the michigan basin were integrated with previously published shale data and brines in subjacent silurian devonian carbonates this comprehensive database provides important constraints on fluid and solute transport and makes a compelling case for the reorganization of drinking water resources and salinity structures along the shallow basin margins by pleistocene glaciation na ca cl br relations and mass balance calculations were used to determine the relative volume of meteoric waters and sources of salinity in antrim shale fluids the majority of shale formation waters contain greater than 50 meteoric water with most containing over 80 meteoric water up to 300 m beneath the shale subcrop despite the presence of a strong salinity gradient meteoric water recharge dissolved variable amounts of halite from evaporite bearing silurian devonian carbonates along the flow path into the shale and displaced highly saline nacacl remnant marine brines the majority of antrim shale fluids owe greater than 60 of their salinity to halite dissolution while less than 40 of cl is from mixing with brines in silurian devonian strata oxygen and hydrogen isotope chemistry and carbon 14 age dating indicate these nacl brines were likely generated since the late pleistocene our conceptual model of fluid flow along the michigan basin margins and its role in generation of microbial gas were extrapolated to the larger glaciated midcontinent region where the silurian devonian carbonate subcrop is continuous along the illinois michigan and appalachian basin margins and is overlain by upper devonian black shales major differences in the hydrostratigraphy and fluid salinity of the epicratonic basins controlled the extent of meteoric water invasion and generation of microbial methane increased hydraulic gradients from melting of the continental ice sheets greatly enhanced recharge of dilute waters into deep silurian devonian aquifers and overlying fractured shales reversing regional scale groundwater flow and altering the major ion composition these fluid migration events occurred over relatively short time scales thousands of years compared to well documented basinal scale fluid migration events driven by tectonics and sediment compaction over millions of years understanding the hydrogeochemistry of the saline meteoric water mixing zones and the sources of salinity in sedimentary basins are both important for constraining fluid and solute transport chemical evolution of basinal fluids and physical stability of brines during meteoric water invasion

mantle plumes continental magmatism and asymmetry in the south atlantic melt production rates are estimated along the ocean tracks rio grande rise walvis ridge and the onshore parana etendeka flood basalt province for the mantle plume currently associated with tristan da cunha in the south atlantic assuming that the volcanic edifice is locally compensated with a thickened crust the maximum oceanic rate 0 3 km3 a 1 is similar to the value for the continental flood basalt calculated using the surface volume of lava and a duration of 5 m y however this latter estimate is conservative and the appropriate rate is probably at least a factor of 5 higher the maximum mantle potential temperature for the ocean plume tracks is estimated to have been 1450 1540 c assuming a dry peridotite source using a similar model temperatures in excess of 1600 c are required to explain the observed magma volumes onshore this is because there is no significant extension in the region where the oldest lavas occur it is argued that the observed volumes of melt can be generated with small amounts of extension and with plume temperatures of 1500 c if melting in the lithosphere is strongly influenced by the relative enrichment of volatiles moreover the model predicts the inferred change to an asthenosphere dominated source when significant extension occurs recent geochonological data have shown that the continental volcanics are 138 ma in the northwest of the parana province and become progressively younger to the southeast oceanic melt production rates decrease by a factor of 3 5 towards the mid ocean ridge tristan da cunha intriguingly melt production rates on the rio grande rise vary to more than twice that of the walvis ridge for oceanic crust of similar age this asymmetry is also seen in the continental regions most obviously in the preserved volume of lava in the parana and etendeka but also in the topography of the underplated continental margin and the orientation of dykes and oblique extension structures these observations reflect the combined roles of the plume temperature lithospheric thickness crustal tectonics and magma source region composition during the evolution of the south atlantic over the last 150 ma