Milk River Research Articles

81Kr and 85Kr in groundwater, Milk River aquifer, Alberta, Canada

The 85Kr activity of well No. 9 is (2.1 ± 0.3) mBq/cm 3 STP ofKr or ≈0.3% of the modern atmospheric activity indicating that no young water component is present in this groundwater and that no contamination occurred in extracting a Kr gas sample for 81Kr analysis. The 81Kr concentration was measured by laser resonance ionization spectroscopy to be 82 ± 18% of the modern atmospheric concentration. Only 5000 atoms of 81Kr were used in the final analytical step which represent ≈7% of the initial number present in a water sample of 50 1. An upper limit of 140 ka is calculated for the age of the water from a simple 81Kr decay model. Of key importance for the future use of a 81Kr dating technique is the conclusion that subsurface production of 81Kr appears to be unimportant.

Dissolved gases in the Milk River aquifer, Alberta, Canada

Geochemical relations between the noble gases, 40Ar/ 36Ar ratio, N 2 and CH 4 contents of groundwaters from the Milk River aquifer, Albert, Canada, have been investigated. The CH 4 contents for many of the groundwaters are several times their N 2 contents and cause degassing to occur as the hydrostatic pressure decreases during their ascent in the wells. Recharge temperatures, derived for those groundwaters that were not degassed, indicate that the youngest groundwaters were recharged under cooler climatic conditions than prevailed during earlier recharge. This conclusion is supported by the stable isotope compositions of the groundwater. The 4He concentration in the groundwater varies with depth according to the theoretical concentration/depth profile for accumulated radiogenic 4He in the aquifer and its adjacent shales. The corresponding flux of 4He to the atmosphere is <2% of the total crustal 4He production rate. Excess radiogenic 40Ar is associated with CH 4 and both gases originated within the adjacent shales. The CH 4 is biogenic and was produced in an aqueous environment which ranged from marine to freshwater as the connate fluids in these marine shales were replaced. The degassing process has been modelled to explain the residual dissolved gas contents of the groundwater and to show that the CH 4/N 2 ratio in situ was ∼12.

Application of isotopic methods to dating of very old groundwaters: Milk River aquifer, Alberta, Canada

The aim of this joint project was to evaluate the usefulness of available geochemical and isotope techniques for dating very old groundwater. This paper represents a synthesis of an IAEA sponsored study for which purpose the Milk River aquifer groundwaters were sampled from 16 wells during 1985 and subsequent years for the following measurements: 2H, 3H, 13C, 18O, 14C, 39Ar, 81Kr, 85Kr, noble gases including 222Rn, 36Cl, 129I and U isotopes. The Milk River aquifer was selected for this study because several preceding investigations had established that this groundwater system contains waters whose ages range from recent to 1Ma. The present study has established that the Milk River aquifer system is very complex both in terms of groundwater origin and in terms of the evolution of its chemical and isotopic contents. However, this apparent complexity proved to be an interesting challenge with respect to the use of different and complementary approaches to interpretation of the geochemical and isotope data in terms of groundwater residence time. Thus, the groundwater ages based on the hydrodynamic model should be considered as a lower limit of the average groundwater age in the Milk River aquifer (∼0.25Ma) while those based on the 36Cl/Cl data uncorrected for any dilution by dead Cl should be considered as an upper limit (<2Ma). The Milk River Aquifer International Project is an excellent illustration of the variety of insight and increased confidence possible in flow-system analysis when multiple, independent dating methods are combined with detailed hydrogeological studies. The conclusion of the present study is that the potential for dating of very old groundwaters by a variety of isotope techniques is very high, provided a combination of methods is applied (never a simple method by itself).

Radiocarbon and stable isotopes in water and dissolved constituents, Milk River aquifer, Alberta, Canada

Origin and age of groundwater in the Milk River aquifer (Alberta, Canada) was the focal point of the present study. To answer related questions, wells in this aquifer were sampled and 2H and 18O in water, 13C and 2H in methane, 34S and 18O in SO 4, 13C and 14C in dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC), and tritium contents determined. Stable isotope analyses on ground-water permitted the recognition of at least three different zones within the aquifer: starting at the recharge zone modern-type groundwaters are encountered for the first few kilometers. These are followed by groundwater with slightly higher 18O and 2H contents, i.e. waters which do not show a glacial signature and were probably recharged under warmer climatic conditions. Groundwater in the third zone is characterized by higher salinities and a pronounced oxygen isotope shift. They show the gradual admixture of far more saline formation waters from the Alberta Basin. Sulphate-S and sulphate-O isotope values indicate a till source for the SO 4. However, SO 4 in wells close to the area where SO 4 virtually disappears show isotopic values which suggest that SO 4-reduction is occurring, although other studies could not find bacterial populations of SO 4 reducers. Methane is present in most wells and, based on C and H isotope data, has a biogenic origin. Methane production occurs close to some wells and/or it diffuses from the confining shales into the aquifer. Radiocarbon is measurable only in the first 20 km from the recharge zone, however, transformation of measured concentrations to “water ages” is very difficult because of the complexity of the geochemical system. Comparison with 14C data on DOC was, therefore, very interesting and this new technique may complement the DIC radiocarbon dating. Two wells near the recharge zone yielded DIC, DOC-High Molecular Weight (HMW) and DOC-Low Molecular Weight (LMW) results. The DIC dates were much older than DOC dates but the differenve in years between the wells for all three types of C were within 1000 a of each other. The DOC dates led to the conclusion that the initial DIC radiocarbon content was as low as 30% modern when the water entered the aquifer. The age of the water 20 km from the recharge zone was assessed at ∼20,000 a, resulting in a velocity of ∼1 m/a. This result is much higher than estimates by other techniques.

Underground production of radionuclides in the Milk River aquifer, Alberta, Canada

Most cosmogenic radionuclides that may be used to estimate groundwater ages in excess of 100 ka are also produced underground by in situ nuclear reactions. Radioactive equilibrium between in situ production and decay would be approached within such long residence times. Radionuclide production by in situ nuclear reactions within the groundwater and within its host rock has been calculated theoretically and compared with some measured radionuclide contents of the groundwater. The fractional transfer of in situ produced 37Ar, 39Ar and 222Rn from rock to groundwater necessary to account for the total measured groundwater contents were found to be similar, although site specific. The implications for radionuclide release mechanisms and for groundwater dating by the use of cosmogenic radionuclides, including those which are applicable for very old groundwaters ( 36Cl, 81Kr, 129I), are discussed.

36Cl measurements and dating of groundwater samples from the Milk River aquifer

36 Cl Cl ratios of twelve groundwater samples from the Milk River aquifer were determined by accelerator mass spectrometry at the Munich accelerator laboratory. 36Cl concentrations were deduced. Approximately linear relations were observed between the logarithm of the 36Cl concentration, the chloride concentration and the distance from the recharge area for two flow paths. These observed relations are discussed in a rather model-independent interpretation without and with in situ production of 36Cl. Flow velocities between 0.04 and 0.11 m/yr, and ages of the groundwater between 0.8 and 2 million years are obtained at the end of the aquifer 80 km from the recharge area.

Cretaceous mammals of southern Utah. II. Marsupials and marsupial-like mammals from the Wahweap Formation (early Campanian)

The Wahweap Formation of southern Utah is probably early Campanian in age. Its mammalian fauna is generally similar to that of the Aquilan upper Milk River Formation, Alberta, but differs substanti...

Cretaceous mammals of southern Utah. I. Marsupials from the Kaiparowits Formation (Judithian)

ABSTRACT Marsupial mammals are herein described from the Kaiparowits Formation of southcentral Utah, of probable Judithian (Campanian, Late Cretaceous) age. New materials of Iqualadelphis lactea, previously described from the upper Milk River Formation of Alberta, support the hypothesis that the species is the most primitive known marsupial. A new species, intermediate in morphology between the Aquilan “Alphadon” creber and the Judithian to Lancian “A” lulli, is described, and the three are removed to a new genus, Protalphadon. Two new species closely similar to Judithian “Alphadon” russelli and “A” praesagus, respectively, are described; these, together with the Lancian “A” rhaister share derived morphology not found in other North American Cretaceous peradectids, and are placed in the new genus Turgidodon. New materials of the Judithian Alphadon halleyi and A. sahnii support the distinction of these closely similar species. Knowledge of the diminutive Alphadon attaragos, described on the basis of an isolated lower molar, is improved by molars representing several upper and lower loci. Marsupials of the Kaiparowits Formation are most closely similar to those previously reported from the Judithian, although the relative primitiveness of several Utah species and the presence of a taxon otherwise restricted to the Aquilan suggests that assemblages from the lower Kaiparowits Formation, at least, may be somewhat older than typical Judithian faunas. It is also likely that the distinctiveness of the Kaiparowits taxa from those represented in more northerly faunas is, in part, due to Zoogeographic differentiation among North American Cretaceous terrestrial vertebrates. Pediomyid and stagodontid marsupials, for instance, are important elements of most known assemblages from the north-central Rocky Mountain region; these are rare or absent in the Kaiparowits Formation.

Reply [to “Comment on ‘An alternative view on the origin of chemical and isotopic patterns in groundwater from the Milk River Aquifer, Canada’ by M. J. Hendry and F. W. Schwartz”

Reply [to “Comment on ‘An alternative view on the origin of chemical and isotopic patterns in groundwater from the Milk River Aquifer, Canada’ by M. J. Hendry and F. W. Schwartz”

Comment on “An alternative view on the origin of chemical and isotopic patterns in groundwater from the Milk River Aquifer, Canada” by M. J. Hendry and F. W. Schwartz

Water Resources ResearchVolume 26, Issue 7 p. 1693-1698 Free Access Comment on “An alternative view on the origin of chemical and isotopic patterns in groundwater from the Milk River Aquifer, Canada” by M. J. Hendry and F. W. Schwartz Fred M. Phillips, Fred M. PhillipsSearch for more papers by this authorRobert G. Knowlton, Robert G. KnowltonSearch for more papers by this authorHarold W. Bentley, Harold W. BentleySearch for more papers by this author Fred M. Phillips, Fred M. PhillipsSearch for more papers by this authorRobert G. Knowlton, Robert G. KnowltonSearch for more papers by this authorHarold W. Bentley, Harold W. BentleySearch for more papers by this author First published: July 1990 https://doi.org/10.1029/WR026i007p01693Citations: 2AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume26, Issue7July 1990Pages 1693-1698 ReferencesRelatedInformation

Accelerator mass spectrometry with fully stripped 26Al, 63Cl, 41Ca and (su59)Ni ions

The detection system of accelerator mass spectrometry (AMS) with completely stripped ions of 26Al, 36Cl, 41Ca and 59Ni at the Munich accelerator laboratory and measurements with these ions are presented. Detection limits are given. The presented applications are: dating of groundwater of the Milk River aquifer and deduction of the neutron fluence and spectrum of the Hiroshima A-bomb.

The Chemical Evolution of Ground Water in the Milk River Aquifer, Canada

AbstractWell‐defined trends are observed in the ion composition of ground water from the Milk River aquifer. Ground water from the area of the subcrop has higher concentrations of Na+, SO42‐, Ca2+, and Mg2+ than immediately downgradient. Away from the area of subcrop, Na+, Cl‐, HCO3‐ + CO32‐, and CH4 concentrations increase systematically with increased residence time, pH decreases, and Mg2+ and Ca2+ concentrations are typically low (less than 0.1 mmol/1). Geologic changes play an important role in producing these chemical patterns. The first major geologic change was the erosion of the overlying confining beds in the recharge area about 5 × 105 years ago, enabling meteoric water with low concentrations of Na+ and Cl‐ to enter the aquifer and displace preexisting water. The second major change was the deposition of glacial till in the area of the Milk River about 30,000 to 40,000 years ago. Water recharging through the till to the aquifer developed characteristically high concentrations of Na+, SO42‐, Ca2+, and Mg2+. Downgradient of the area of subcrop, the trends in Na+ and Cl‐ are controlled by diffusion from the underlying confining shale. Analyses of ground‐water and gas samples for sulfate reducers and ground‐water and gas samples for sulfide and H2S, respectively, suggest that SO42‐ reduction is not a major process. Geochemical modeling suggests that CO2 gas is added to the ground water with increased residence time in the aquifer. The increase in CO2, CH4, and dissolved inorganic carbon can be attributed to methane fermentation. Geochemical modeling suggests that cation exchange plays a minor role in the chemical evolution of the ground waters.

A tidal‐inlet complex in the Cretaceous epeiric sea of North America: Virgelle Member, Milk River Formation, southern Alberta, Canada

ABSTRACTThe upper portion of the Virgelle Member (Upper Cretaceous Milk River Formation) at Writing‐on‐Stone Provincial Park of southern Alberta preserves evidence of tidal processes along an otherwise wave‐dominated, progradational shoreline in the Cretaceous Interior Seaway of North America. The upper Virgelle Member is underlain by offshore transition to lower shoreface deposits of the Telegraph Creek Member and the lower Virgelle Member, respectively, and is overlain by the non‐marine shales and sandstones of the Deadhorse Coulee Member. The sediments of the upper Virgelle Member were deposited along a prograding shoreline and are interpreted here as those of a tidal‐inlet complex. Most inlet sections consist of an erosional base overlain by a shale‐pebble conglomerate, followed by cross‐bedded sandstones which become finer‐grained and decrease in scale upwards. Indicators of tidal processes include palaeocurrent distributions, mud couplets, tidal bundles, re‐activation surfaces and herringbone cross‐beds. The sequence through the tidal‐inlet complex can be differentiated, according to prevalent palaeoflow directions and sedimentary structures, as ebb‐dominated, flood‐dominated, or mixed‐tidal influence. Ebb‐dominated sections commonly contain lateral accretion surfaces whereas flood‐dominated sections contain tidal‐ramp deposits. Back‐barrier lagoon deposits are dominated by sandstones of an extensive flood‐tidal delta with only thin shales preserved locally at the top of the inlet complex. Deposits of ebb‐tidal deltas are absent, presumably due to the effective sediment dispersal by waves and wave‐induced longshore currents acting on the regionally wave‐dominated shoreline.

Comment on "An alternative view on the origin of chemical and isotopic patterns in groundwater from the Milk River aquifer, Canada" by M. J. Hendry and F. W. Schwartz (WRR 1988, 24(10), 1747-1763)

Comment on "An alternative view on the origin of chemical and isotopic patterns in groundwater from the Milk River aquifer, Canada" by M. J. Hendry and F. W. Schwartz (WRR 1988, 24(10), 1747-1763)

Reply to comment on "an alternative view on the origin of chemical and isotopic patterns in groundwater from the Milk River aquifer, Canada" by M. J. Hendry and F. W. Schwartz

Reply to comment on "an alternative view on the origin of chemical and isotopic patterns in groundwater from the Milk River aquifer, Canada" by M. J. Hendry and F. W. Schwartz

Correction to "Characterization and isotopic composition of organic and inorganic carbon in the Milk River aquifer" (WRR 25(8), 1893-1905, August 1989)

Correction to "Characterization and isotopic composition of organic and inorganic carbon in the Milk River aquifer" (WRR 25(8), 1893-1905, August 1989)

Correction to “Characterization and isotopic composition of organic and inorganic carbon in the Milk River Aquifer” by Ellyn M. Murphy, Stanley N. Davis, Austin Long, Douglas Donahue, and A. J. Timothy Jull

Correction to “Characterization and isotopic composition of organic and inorganic carbon in the Milk River Aquifer” by Ellyn M. Murphy, Stanley N. Davis, Austin Long, Douglas Donahue, and A. J. Timothy Jull

Morphologically distinct populations of the shorthead sculpin, Cottus confusus, and mottled sculpin, Cottus bairdi (Pisces, Cottidae), near the western border of Canada and the United States

Previously known within Canada from the Flathead River, nominal Cottus confusus also occur in the Kettle, Columbia, and Slocan rivers of British Columbia. The latter populations are similar to those from Washington, and possess a post-maxillary pore, lower numbers of pectoral rays, prickles behind the pectoral fin, and a smooth head. They are sympatric with nominal Cottus bairdi, with some individuals morphologically intermediate between the two species. Flathead River samples of nominal C. confusus differ from Columbia River populations in absence of the pore and prickles, higher fin ray counts, and larger head papillae. Specimens of nominal C. bairdi previously reported from the St. Mary River (Saskatchewan and Nelson drainages) and Milk River (Missouri River drainage) of Alberta are similar to Flathead River C. confusus, with others intermediate between Flathead River C. confusus and Columbia River populations of C. bairdi and C. confusus. Differences between Flathead River and Columbia River samples suggest that these populations require separate status in Canada. Similkameen River samples of C. bairdi are morphologically variable, individuals from upstream populations having some characters similar to those of C. confusus. A thorough study of C. bairdi and C. confusus in the United States is needed to redefine species limits.

Characterization and isotopic composition of organic and inorganic carbon in the Milk River Aquifer

Carbon isotope analyses were performed by accelerator mass spectrometry on fractions of dissolved organic carbon (DOC) in groundwater from the Milk River aquifer, Alberta, Canada. The DOC was separated into high molecular weight (HMW) and low molecular weight (LMW) fractions for analysis. Characterization information and 14C activities suggest that the HMW fractions (primarily humic substances) originate in the interstitial waters of the soil zone in the area of recharge and are transported through the porous media of the aquifer. Transformations of HMW fractions down the flow path, including an increase in carbon, decrease in oxygen, and a pronounced increase in the aliphatic nature of this fraction, are consistent with decreasing 14C activity. The LMW fractions show a dominant kerogen origin. This fraction of the DOC has low 14C activities (generally &lt;1 percent modern carbon), and gas chromatograph/mass spectrometry analyses identified a homologous series of substituted alkanes, further evidence that these compounds may have originated from organic‐rich shales in the aquifer and/or confining beds. Geochemical and stable isotope measurements of the dissolved inorganic carbon (DIC) indicate that microbial activity is occurring in the Milk River aquifer. The alteration of these DIC δ13C ratios by microbial activity render corrections for groundwater age in this aquifer difficult, if not impossible. Although 14C analyses of DOC fractions will not replace other groundwater dating techniques, these analyses do provide additional information on groundwater age and perhaps a more complete interpretation of groundwater age than DIC alone.

14C in fractions of dissolved organic carbon in ground water

Fundamental information is lacking on the natural dissolved organic carbon in ground water, information both necessary to understand pollutant transport and degradation and pertinent to isotope dating of ground water and reconstructions of groundwater history. Here we report, for the first time, carbon isotope ratios of fractions of natural organic compounds in ground waters iso-lated from the Stripa mine (Sweden) and the Milk River aquifer (Alberta, Canada). High-molecular-weight and low-molecular-weight fractions of the organic carbon were characterized and these, along with dissolved inorganic carbon, were analysed for δ13C and 14C. The 14C results suggest that the dissolved organic carbon originates from a combination of soil organic matter and kerogen in the aquifer matrix. The high-molecular-weight fractions show a predominant soil origin, whereas the low-molecular-weight fractions are often strongly influenced by kerogen. In both systems studied, groundwater dating by traditional 14C analyses of the dissolved inorganic carbon is difficult1–3. The 14C activities of the high-molecular-weight fractions, which were identified as fulvic acids, follow trends consistent with 14C dissolved-inorganic-carbon analyses and, in some cases, provide additional information on groundwater age.