Dolomite Petrography and Stable Isotope Geochemistry of the Bakken Formation, Southeastern Saskatchewan

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1 Dolomite Petrography and Stable Isotope Geochemistry of the Bakken Formation, Southeastern Saskatchewan Adam Staruiala 1, Hairuo Qing 1, Guoxiang Chi 1, Richard Stern 2, and Duane Petts 2 Staruiala, A., Qing, H., Chi, G., Stern, R., and Petts, D. (2013): Dolomite petrography and stable isotope geochemistry of the Bakken Formation, southeastern Saskatchewan; in Summary of Investigations 2013, Volume 1, Saskatchewan Geological Survey, Sask. Ministry of the Economy, Misc. Rep , Paper A-8, 10p. Abstract In southeastern Saskatchewan, strata of the Middle Bakken Member of the Bakken Formation are composed of mixed clastic and carbonate rocks with variable amounts of dolomite. Three dolomite phases have been identified based upon microscope petrography and backscattered scanning electron microscope images. Phase D dolomite is non-ferroan, has a rounded grain shape and occurs as cores that are overgrown by up to two other phases of dolomite; phase D dolomite also occurs as distinct grains that are not overgrown by later phases of dolomite. Phase 1 dolomite is non-ferroan, generally subhedral, locally euhedral, and is commonly surrounded by phase 2 dolomite. Phase 2 dolomite is ferroan, anhedral to euhedral, and commonly occurs as overgrowths on phase 1 dolomite. Monophase (aqueous liquid) fluid inclusions are found in phase 1 dolomite, whereas biphase (liquid and vapour) inclusions occur in phase 2 dolomite and have homogenization temperatures ranging from 74 C to 114 C. The average δ 18 O and δ 13 C values (VPDB), obtained through secondary ion mass spectrometry analysis, are and 0.47, respectively, for phase 1 dolomite, and and -0.24, respectively, for phase 2 dolomite. No oxygen or carbon isotope data were obtained for phase D dolomite. Phase D dolomite is interpreted as being detrital or mechanically reworked penecontemporaneous dolomite. The δ 18 O and δ 13 C values of the parent fluids, calculated from those of the dolomite and the fluid inclusion homogenization temperatures, suggest that phase 1 dolomite may have formed from Late Devonian seawater that was mixed with meteoric water, whereas phase 2 dolomite may have formed directly from water with an evaporitic signature under burial conditions; this interpretation assumes that the original isotopic values of dolomite were not modified during late diagenesis. Keywords: Bakken Formation, Williston Basin, dolomitization, stable isotopes, fluid inclusions. 1. Introduction The depositional environment and stratigraphic relationships of the Bakken Formation have received considerable attention in recent years. Several studies have utilized sedimentological and ichnological traits observed in core, as well as the geophysical log characteristics of these strata to determine depositional environments and stratigraphic relationships (e.g., Christopher, 1961; LeFever et al., 1991; Smith and Bustin, 1995, 1998, 2000; Kreis and Costa, 2005; Kreis et al., 2006; Angulo and Buatois, 2009a, 2009b, 2011, 2012a, 2012b; Kohlruss and Nickel, 2009). Of importance with respect to this study is the interpretation that the Middle Bakken Member was deposited during the Devonian to Mississippian transition, in late Famennian to Kinderhookian time (Karma, 1991; Angulo and Buatois, 2009b) (Figure 1). More recently, attention has been paid to carbonate phases in the Bakken Formation, including dolomites (Pitman et al., 2001; Imam et al., 2012; Staruiala et al., 2013). Because the occurrence and distribution of dolomite play an important role in the distribution of porosity in Bakken reservoirs, a petrographic, isotopic and fluid inclusion microthermometric investigation has been undertaken in this study in order to determine the nature of dolomite that is found within the Bakken Formation in southeastern Saskatchewan. 2. Study Area and Methods The study area in southeastern Saskatchewan encompasses Ranges 30W1 to 18W2 and Townships 1 to 15 (Figure 2). Thirty-two cores were logged in order to investigate lithology and stratigraphic relationships (see Staruiala et al., 2013). Ninety-two thin sections from a total of 11 cores (Figure 2) were sampled in order to analyze lithology, diagenesis, porosity, and permeability traits. Of these 11 cores, 10 contained appreciable amounts of dolomite (excluding well 191/ W2; 05I208). From these 10 cores, 15 samples were selected from a total of 8 wells for analysis of carbon and oxygen isotopes, and 12 samples were selected from 6 wells for fluid inclusion microthermometry. The results of these analyses were used in the interpretation of the timing and mechanisms of dolomitization in the Bakken Formation. Petrography in this study was accomplished using an Olympus BXI50 microscope as well as a Zeiss EVO 15 scanning electron microscope (SEM). The method used to analyze carbon and oxygen isotopic ratios was secondary ion mass spectrometry (SIMS) using a Cameca IMS1280 ion microprobe 1 Department of Geology, University of Regina, 3737 Wascana Parkway, Regina, SK S4S 0A2. 2 Department of Earth and Atmospheric Sciences, University of Alberta, 1-26 Earth Sciences Building, Edmonton, AB T6G 2E2. Saskatchewan Geological Survey 1 Summary of Investigations 2013, Volume 1

2 at the Canadian Centre for Isotopic Microanalysis (CCIM), University of Alberta. A total of 121 analyses of carbon and oxygen isotopes of two phases of dolomite were obtained. This technique allows the in situ analysis of individual grains at a 10 µm scale. Fluid inclusions were analyzed using a Linkham THMS600 heating and freezing stage. In the 12 samples and subsequent fluid inclusion thin sections, a total of 22 measurable fluid inclusions were found. More than 22 fluid inclusions were observed, but most were smaller than 1 µm too small to be analyzed microthemometrically. Only four homogenization temperatures were obtained, using the cycling technique (Haynes, 1985). However, no final ice-melting temperature could be measured, even with the cycling technique. Figure 1 Stratigraphic chart comparing the Exshaw Formation of Alberta with the Bakken Formation of Saskatchewan (after Angulo and Buatois, 2009b). The middle member of the Bakken Formation is interpreted as being deposited during both the late Famennian and the Kinderhookian ages, as determined through conodont biostratigraphy by Karma (1991). Figure 2 Left: base map of study area showing locations of cored wells included in this study. Blue dots represent wells in which both core and thin sections are available for the study. Red dots indicate wells in which only core is available. Yellow dots represent wells with core, thin sections and geochemical analyses. Right: area map illustrating in red the spatial distribution of the Bakken Formation in the Williston Basin (used with permission of Energy and Environmental Research Center, 2011). Saskatchewan Geological Survey 2 Summary of Investigations 2013, Volume 1

3 3. Results and Discussion a) Petrography Core examination and thin-section petrography of the Middle Bakken Member in southeastern Saskatchewan indicates that these rocks are composed of mixed clastic-carbonate lithofacies with variable amounts of dolomite (e.g., Imam et al., 2012; Staruiala et al., 2013). Based upon microscope petrography and backscattered SEM images of samples from the 10 cores that contained and were sampled for dolomite, three texturally different dolomite phases are recognized in the Middle Bakken: phase D, phase 1, and phase 2 dolomite. Phase D dolomite is characterized by its rounded grain texture (Figure 3), a grain size that ranges from 5 to 25 µm, the presence of abundant aqueous fluid inclusions that are monophase, its cloudy appearance in plane-polarized light, and dark colour in SEM backscattered images. Cleavage within these grains is usually not well developed (Figure 3) and the grains are non-ferroan in composition. Some of the phase D dolomite grains are found at the centre of larger dolomite rhombs in which phase 1 and phase 2 dolomite have locally overgrown phase D grains (Figure 3). As well, these grains are found sporadically throughout larger dolomite aggregates that contain both phase 1 and phase 2 dolomite, and as singular distinct grains. In nine of the cores, this phase of dolomite is present in very small quantities; visual estimations indicate this phase comprises less than 1% of the rocks. However, slightly higher proportions of phase D dolomite, up to 2%, are documented in well 101/ W2 (based upon visual estimation). Phase D dolomite is sporadically distributed throughout the Bakken Formation siltstones, while no evidence of phase D dolomite was found in the coarser sandstones or the lime grainstones. Phase 1 dolomite is non-ferroan and occurs as anhedral to euhedral crystals (Figure 4) with sizes from approximately 10 to 75 µm. These crystals are found as discrete crystals/grains, as cores in the centre of larger dolomite aggregates, and as the cores to overgrowths of phase 2 dolomite (Figures 3 and 4). Within the aggregates and the cores of larger overgrowth rhombs, phase 1 dolomite can show planar-e to planar-s growth bands (Figure 4). This phase of dolomite contains abundant monophase aqueous fluid inclusions, which are commonly oriented along growth zones within the crystals/grains. Under cross-polarized light microscopy, phase 1 dolomite exhibits a much more cloudy appearance than phase 2 dolomite (Figure 4). When viewed using SEM backscattered electron imaging, the grains have a dark grey colour as compared to a light grey to white colour for phase 2 dolomite (Figure 5). Phase 1 dolomite is found within all facies observed within the Bakken Formation. It is most prominent in the intervals below the sandstones and grainstones within the Middle Bakken Member. The grainstones and crossbedded sandstones are the only observed samples in this study that did not contain this phase of dolomite. Determining the proportion of dolomite that is phase 1 relative to phases D and 2 is difficult, as this requires the use of SEM techniques to differentiate the phases in most cases. Figure 3 Photomicrograph illustrating the three phases of dolomite found within the Bakken in this study. Phase D dolomite is non-ferroan and is characterized by a rounded, cloudy, inclusion-rich core and is overgrown by younger dolomite phases. Phase 1 dolomite is characterized by its non-ferroan composition and fewer inclusions relative to phase D. Phase 2 dolomite is characterized by ferroan composition and relatively inclusion-free appearance. Qtz = quartz. Sample location is well 101/ W2; 67I041; depth is m. Saskatchewan Geological Survey 3 Summary of Investigations 2013, Volume 1

4 Figure 4 Photomicrographs showing fluid inclusions found in different phases of dolomite. A) Biphase fluid inclusion (circled) in phase 2 dolomite versus monophase inclusions in phase 1 dolomite; Qtz = quartz. B) Biphase fluid inclusion in phase 2 dolomite (circled) versus densely populated inclusions (cloudy) in phase 1 dolomite; note fluid inclusions in phase 1 dolomite are too small to be discernible at the scale of this photomicrograph. Sample location is well 101/ W2; 67I041, core depth is m. Figure 5 Scanning electron microscope image (backscattered electron image) showing the relative location of the secondary ion mass spectrometry (SIMS) sampling spots (A). The two large crystals in the centre pore are phase 2 dolomite. The large macro pore in which these two crystals are found is interpreted as being created through dissolution. The very dark cores are phase 1 dolomite, which may be euhedral (B), subhedral (C), or subhedral to anhedral (D). Sample location is well 101/ W2; 67I041; core depth is m. Saskatchewan Geological Survey 4 Summary of Investigations 2013, Volume 1

5 Phase 2 dolomite is found as a pore-filling cement and as overgrowth cement that forms laminae over phase D and phase 1 dolomite within the Bakken Formation (Figures 3, 4, and 5). This phase of dolomite can be found as large (locally greater than 50 µm), euhedral to subhedral rhombs that infill open pore space, anhedral crystal aggregates, non-planar pore-filling cements, and planar overgrowths of previous generations of dolomite (Figures 3 and 4). These planar and non-planar overgrowths have variable thickness, and show relatively well-developed cleavage and compositional zoning under SEM backscattered electron imaging (Figure 5). Phase 2 dolomite contains biphase aqueous fluid inclusions (liquid and vapour; Figure 4). Oil and gas inclusions were not observed in phase 2 dolomite. Phase 2 dolomite was observed in all thin sections in this study. b) Isotopic and Fluid Inclusion Data Phase 1 and phase 2 dolomite were analyzed for oxygen and carbon isotopes and fluid inclusions. All inclusions were viewed under ultraviolet light using an Olympus BXI50 microscope to determine if oil inclusions were present. Phase D dolomite is found in very small quantities, and no isotopic or fluid inclusion microthermometry data for this phase of dolomite were collected. The oxygen and carbon isotopic compositions of phase 1 and phase 2 dolomite are summarized in Table 1 and plotted on Figure 6. The δ 18 O and δ 13 C values of phase 1 dolomite average Vienna Pee Dee Belemnite (VPDB) and 0.47 (VPDB), respectively. All the fluid inclusions in phase 1 dolomite are monophase (liquid-only) aqueous inclusions, and thus no homogenization temperatures can be measured. All these inclusions are non-fluorescent. The δ 18 O and δ 13 C values of phase 2 dolomite average (VPDB) and (VPDB), respectively. Many biphase (liquid + vapour) aqueous fluid inclusions are present in phase 2 dolomite. All of them are non-fluorescent. Most of these inclusions are too small to yield precise homogenization temperatures. Some fluid inclusions have abnormally large vapour bubbles (e.g., Figure 4A), possibly due to post-trapping stretching, and, therefore, the homogenization temperatures are not reliable. Four discrete fluid inclusions were measured for homogenization temperatures, yielding values of 74 C, 76 C, 110 C, and 114 C. These homogenization temperatures are reproducible using the cycling technique. However, no reproducible ice-melting temperatures have been obtained from these inclusions, due to the small size and low visibility of the inclusions in freezing runs. Unfortunately, homogenization temperatures from inclusions belonging to the same fluid inclusion assemblage were not obtained. Table 1 Sample location, licence #, core depth, average isotopic values per sample location and the number of crystals analyzed in each sample of phase 1 (top) and phase 2 dolomite (bottom). Average δ 18 O (VPDB), Number of Samples Average δ 13 C (VPDB), Number of Samples Well Location Licence # Depth (m) ± 1 σ ± 1 σ Phase 1 Dolomite 101/ W2 67I N/A N/A 0 111/ W2 08B / W2 06B / W2 08F / W2 08G / W2 81D / W2 81D Average Phase 2 Dolomite 101/ W2 67I / W2 08B / W2 06B / W2 08F / W2 08G / W2 81D N/A N/A 0 141/ W2 81D Average Saskatchewan Geological Survey 5 Summary of Investigations 2013, Volume 1

6 Figure 6 Cross plot of δ 18 O and δ 13 C values (, VPDB) for phase 1 and phase 2 dolomite. The black outlined box indicates expected values for dolomite derived from Late Devonian seawater (van Geldern et al., 2006). c) Interpretation and Discussion The Middle Bakken Member was deposited in late Famennian to Kinderhookian time (Karma, 1991). Placing this time boundary at a specific facies transition or location is problematic. Our interpretation is that the Middle Bakken Member is a progradational unit, which implies that the oldest sediments are nearest the basin margin and the youngest sediments were deposited nearest the basin depocentre. We, therefore, can assume that the actual time boundary crosses multiple facies and dips toward the basin centre. As our study area is relatively close to the northern and eastern margins of Bakken sedimentation (Figure 2; Kohlruss and Nichol, 2009), we interpret the Middle Bakken sediments in this study area to have been deposited during late Famennian time, with the transition to Kinderhookian time deposition occurring at some point south of the study area. This assumption is important because of the variance in carbon and oxygen isotopic ratios of seawater at the Devonian Mississippian transition (Veizer et al., 1999). Phase D dolomite is found only in small quantities throughout the study area (visually estimated to be less than 1% of the mineralogy observed under thin section). These grains are interpreted as being detrital in origin because the grains are rounded, locally overgrown by other phases of dolomite, and have a cloudy appearance relative to phase 1 and phase 2 dolomite. What is unclear is whether these grains are reworked penecontemporaneous dolomite or derived from erosion of pre-bakken dolomites. If the second interpretation is correct, it would be reasonable to assume that the likely source of these dolomite grains is the underlying Torquay Formation, though other stratigraphic units including the Birdbear and Duperow are also possible sources. Phase 1 dolomite is the second most abundant phase of dolomite observed in the study area. Crystals are both euhedral and anhedral in form (Figure 5). The euhedral crystals with well-developed crystal form and cleavage are interpreted as being formed in situ. The grains that are subhedral to anhedral with irregular grain boundaries have two possible sources. A first interpretation is that these anhedral and subhedral grains are potentially detrital in Saskatchewan Geological Survey 6 Summary of Investigations 2013, Volume 1

7 origin, which is similar to phase D dolomite. At this point, differentiation between anhedral phase 1 grains and phase D grains is difficult at best. The best examples of phase D grains are when three phases of dolomite are clearly seen, as in Figure 3. A second possible interpretation is that the grain texture is a result of dissolution of dolomite formed during deposition of the Bakken Formation by either direct precipitation from Late Devonian seawater or by dolomitization of depositional calcite. It is possible that a major dissolution event occurred between the formation of phase 1 and phase 2 dolomite (Figure 5). This dissolution could have locally removed dolomite and affected the crystal shape. The non-ferroan composition, monophase fluid inclusions and isotopic composition of phase 1 dolomite lead to the interpretation that this dolomite formed in syndepositional to very shallow burial conditions. The fact that the aqueous fluid inclusions in phase 1 dolomite are monophase suggests that the temperature of dolomitization may have been less than 50 C (Allan and Wiggins, 1993). Assuming that the temperature at time of formation of phase 1 dolomite was close to 25 C which would be more consistent with anticipated paleoclimate temperatures that were associated with a warm, tropical climate that included seasonal precipitation (Ettensohn et al., 1988; Smith and Bustin, 1998) and using the average δ 18 O value of (VPDB) for dolomite, the calculated δ 18 O values of the dolomitizing fluids is -7.7 (Vienna Standard Mean Ocean Water, VSMOW), based on the isotope fractionation equations for dolomite and calcite of Zheng (1999) (Eq. 1 below) and the VPDB VSMOW conversion equation of Friedman and O Neil (1977) (Eq. 2). However, if the temperature of dolomitizing fluids is assumed to be 50 C, then the calculated δ 18 O values of the dolomitizing fluids would be -0.3 (VSMOW) ln αα = DD (106 ) TT 2 + EE (103 ) TT + FF (Eq. 1) where T = assumed temperature ( C) and constants D, E, and F are as follows: D=4.060, E=-4.65, F=1.71 for dolomite, D=4.010, E=-4.66, F=1.71 for calcite, and αα DDDDDDDDDDDDDDDD oooo CCCCCCCCCCCCCC = (δδ18 OO DDDDDDDDDDDDDDDD oooo CCCCCCCCCCCCCC ) (δδ 18 OO LLLLLLLLLLLL ) δδ 18 OO VVVVVVVVVV = δδ 18 OO VVVVVVVV (Eq. 2) The interpretation of isotopic data measured from dolomite requires an estimation of isotopic composition of Late Devonian seawater. van Geldern et al. (2006) proposed that marine calcite derived from Late Devonian seawater would have δ 18 O values between -6.1 and -4.3 (VPDB). Assuming a 2.0 to 2.5 enrichment of δ 18 O in dolomite relative to calcite (Land, 1992), the expected δ 18 O values for dolomite derived from Late Devonian seawater would be between -4.1 to -1.8 (VPDB) (Figure 6). Using equations (1) and (2) above, and assuming a temperature of 25 C, the expected δ 18 O isotopic composition of Late Devonian seawater is between -7.1 and -5.3 (VSMOW). The calculated δ 18 O values of the dolomitizing fluids is -7.7 (VSMOW) for phase 1 dolomite, which is 0.6 to 2.4 lower than expected for Late Devonian seawater. Angulo and Buatois (2009a, 2009b, 2011) proposed that the Bakken Formation was deposited in brackish water to marine environments. The influx of meteoric water into the basin may have resulted in lower δ 18 O values. However, the lower δ 18 O values of phase 1 dolomite can also be explained by dolomitization from marine fluid at a temperature higher than 25 C (e.g., 50 C) under shallow burial conditions. Another possibility is that phase 1 dolomite may have been diagenetically altered during burial at higher temperatures and the isotopic composition is not indicative of the fluids that initially formed this dolomite. Phase 2 dolomite is volumetrically the most abundant phase of dolomite within the Bakken Formation. This phase of dolomite is a pore-filling cement, and in some samples can be up to 35% of rock volume based upon visual estimation, though this value is only approximate, as differentiation between phase 1 and phase 2 dolomite requires the use of SEM imagery. The interpretation of the phase 2 dolomite requires a good understanding of the formation temperature. This, however, is limited by the small number of fluid inclusions with measurable homogenization temperatures. The relatively high homogenization temperature values (112 and 114 C) may have resulted from posttrapping stretching or heterogeneous trapping, considering the observation that biphase aqueous inclusions with large vapour bubbles are present (Figure 4A). It is therefore tentatively interpreted that the fluid inclusions with the relatively low homogenization temperatures (74 and 76 C) represent the non-stretched, homogeneously trapped fluid inclusions, and a temperature of 75 C is used to represent the maximum formation temperature of phase 2 dolomite. Saskatchewan Geological Survey 7 Summary of Investigations 2013, Volume 1

8 The presence of iron in the composition of this phase of dolomite as well as moderate fluid inclusion temperatures are indicative of burial dolomite. Using equations (1) and (2), a temperature of 75 C, and an average δ 18 O value of (VPDB), the δ 18 O value of the parent fluid of phase 2 dolomite is calculated to be 5.94 (VSMOW). This elevated δ 18 O value is likely due at least in part to the formation fluids having an evaporitic origin, as this elevated level is higher than any observed period in the Phanerozoic secular isotope trend as proposed by Veizer et al. (1999). Phase 2 dolomite, therefore, may be interpreted to have formed from formation fluids containing heavy oxygen isotopes derived from dissolution of overlying or underlying evaporitic units under burial conditions. An alternative interpretation would be that phase 2 dolomite formed from normal seawater at much lower temperatures. However, based on the observation that biphase inclusions are developed only in phase 2 dolomite and not in phase 1 dolomite, the possibility is slim that all the biphase inclusions in phase 2 resulted from stretching of monophase inclusions. Therefore, the low homogenization temperatures (74 to 76 C) recorded by the biphase inclusions in phase 2 dolomite are likely valid, and evaporitic seawater was likely involved in the formation of phase 2 dolomite. 4. Conclusions Middle Bakken strata in southeastern Saskatchewan are composed of mixed clastic and carbonate rocks with variable amounts of dolomite. Three phases of dolomite are noted based upon microscope petrography and backscattered SEM images. Phase D dolomite is interpreted as being detrital or mechanically reworked contemporaneous Bakken dolomite, based on the rounded grain boundaries and overgrowths of phase 1 and phase 2 dolomite. Phase 1 dolomite has a mean δ 18 O value of (VPDB) and δ 13 C value of 0.47 (VPDB). Based on the observation that liquid-only monophase aqueous inclusions are developed in this phase of dolomite, the formation temperature is likely less than 50 C. Assuming a fluid temperature of 25 C, the calculated δ 18 O values of dolomitizing fluids is -7.7 (VSMOW), whereas assuming a temperature of 50 C would yield a δ 18 O value of -0.3 (VSMOW) for the dolomitizing fluids. The first result of -7.7 (VSMOW), which is lower than those expected for Late Devonian seawater, would suggest that phase 1 dolomite was formed from Late Devonian seawater that was mixed with meteoric water in a syndepositional environment, or at higher temperatures under shallow burial conditions. Alternatively, phase 1 dolomite could be related to normal Devonian seawater but its δ 18 O values may have been diagenetically altered during burial at higher temperatures. Phase 2 dolomite has a δ 18 O value of (VPDB) and δ 13 C values of (VPDB). Using a fluid inclusion homogenization temperature of 75 C, the δ 18 O fluid is calculated to be 5.94 (VSMOW), which is much higher than the estimated Devonian seawater value (Figure 6). It is therefore inferred that phase 2 dolomite may have formed from formation fluids containing heavy oxygen isotopes derived from dissolution of overlying or underlying evaporitic units that precipitated dolomite in pore space under burial conditions. 5. Acknowledgements This study was supported by the Saskatchewan Ministry of the Economy under the University Southern Geoscience Research Grants and Training Program. We thank the staff at the Subsurface Geological Laboratory in Regina for permission and assistance in the sampling and logging of cores. We are also very grateful for the financial support of the Petroleum Technology Research Centre (PTRC). Finally, we wish to thank: Qilong Fu, John Lake, Fran Haidl and Melinda Yurkowski for review, patience and insight in the review of this paper. 6. References Allan, J.R. and Wiggins, W.D. (1993): Dolomite Reservoirs: Geochemical Techniques for Evaluating Origin and Distribution; AAPG Continuing Education Course Note Series, No. 36, The American Association of Petroleum Geologists, Tulsa, Oklahoma, 129p. Angulo, S. and Buatois, L.A. (2009a): Sedimentological and ichnological aspects of a sandy low-energy coast: Upper Devonian Lower Mississippian Bakken Formation, Williston Basin, southeastern Saskatchewan, Canada; in Summary of Investigations 2009, Volume 1, Saskatchewan Geological Survey, Sask. Industry Resources, Misc. Rep , Paper A-5, 17p. Angulo, S. and Buatois, L.A. (2009b): Depositional setting of the Upper Devonian Lower Mississippian Bakken Formation of subsurface Saskatchewan: integrating sedimentologic and ichnologic data; in Proceedings of the Can. Soc. Petrol. Geol. / Can. Soc. Econ. Geol. / Can. Well Log Soc. Geoconvention 2009: Frontiers + Innovation, May 4 to 8, 2009, Calgary, Alberta, p Saskatchewan Geological Survey 8 Summary of Investigations 2013, Volume 1

9 Angulo, S. and Buatois, L.A. (2011): Petrophysical characterization of sedimentary facies from the Upper Devonian Lower Mississippian Bakken Formation in the Williston Basin, southeastern Saskatchewan; in Summary of Investigations 2011, Volume 1, Saskatchewan Geological Survey, Sask. Ministry of Energy and Resources, Misc. Rep , Paper A-6, 16p. Angulo, S. and Buatois, L.A. (2012a): Ichnology of a Late Devonian Early Carboniferous low-energy seaway: the Bakken Formation of subsurface Saskatchewan, Canada: assessing paleoenvironmental controls and biotic responses; Palaeogeography, Palaeoclimatology, Palaeoecology, v , p Angulo, S. and Buatois, L.A. (2012b): Integrating depositional models, ichnology, and sequence stratigraphy in reservoir characterization: the middle member of the Devonian Carboniferous Bakken Formation of subsurface southeastern Saskatchewan revisited; Amer. Assoc. Petrol. Geol., Bull., v96, p Christopher, J.E. (1961): Transitional Devonian Mississippian Formations of Southern Saskatchewan; Sask. Dept. Miner. Resour., Rep. 66, 103p. Energy and Environmental Research Center (2011): Bakken Decision Support System; Grand Forks, North Dakota, (accessed July 22, 2012). Ettensohn, F.R., Miller, M.L., Dillman, S.B., Elam, T.D., Geller, K.L., Swager, D.R., Markowitz, G., Woock, R.D., and Barron, L.S. (1988): Characterization and implications of the Devonian-Mississippian black shale sequence, eastern central Kentucky, U.S.A.: pycnoclines, transgression, regression and tectonism; in McMillan, N.J., Embry, A.F., and Glass, D.J. (eds.), Devonian of the World, Proceedings of the Second International Symposium on the Devonian System, Can. Soc. Petrol. Geol., Mem. 14, Vol. II, p Friedman, I. and O Neil, J.R. (1977): Compilation of stable isotope fractionation factors of geochemical interest; Chapter KK in Data of Geochemistry, Sixth Edition, Fleischer, M. (ed.), U.S. Geol. Surv., Prof. Pap. 440-KK, 117p. Haynes, F.M. (1985): Determination of fluid inclusion compositions by sequential freezing; Econ. Geol., v80, p Imam, B., Qing, H., and Chi, G. (2012): Petrographic study of the Middle Bakken Member, Viewfield area, southeastern Saskatchewan; in Summary of Investigations 2011, Volume 1, Saskatchewan Geological Survey, Sask. Ministry of Energy and Resources, Misc. Rep , Paper A-5, 9p. Karma, R. (1991): Conodonts of the Bakken Formation (Devonian - Mississippian) in Saskatchewan, northern Williston Basin; in Christopher, J.E. and Haidl, F. (eds.), Sixth International Williston Basin Symposium, Sask. Geol. Soc., Spec. Publ. No. 11, p Kohlruss, D. and Nickel, E. (2009): Facies analysis of the Upper Devonian Lower Mississippian Bakken Formation, southeastern Saskatchewan; in Summary of Investigations 2009, Volume 1, Saskatchewan Geological Survey, Sask. Ministry of Energy and Resources, Misc. Rep , Paper A-6, 11p. Kreis, L.K. and Costa, A. (2005): Hydrocarbon potential of the Bakken and Torquay formations, southeastern Saskatchewan; in Summary of Investigations 2005, Volume 1, Saskatchewan Geological Survey, Sask. Industry Resources, Misc. Rep , Paper A-10, 10p. Kreis, L.K., Costa, A.L., and Osadetz, K.G. (2006): Hydrocarbon potential of Bakken and Torquay formations, southeastern Saskatchewan; in Gilboy, C.F. and Whittaker, S.G. (eds.), Saskatchewan and Northern Plains Oil and Gas Symposium 2006, Sask. Geol. Soc., Spec. Publ. No. 19, p Land, L.S. (1992): The dolomite problem: stable and radiogenic isotope clues; in Clauer, N. and Chaudhuri, S. (eds.), Isotopic Signatures and Sedimentary Records, Lecture Notes in Earth Sciences, v43, Springer-Verlag, Springer Berlin Heidelberg, p LeFever, J.A., Martiniuk, C.D., Dancsok, E.F.R., and Mahnic, P.A. (1991): Petroleum potential of the middle member, Bakken Formation, Williston Basin; in Christopher, J.E. and Haidl, F. (eds.), Sixth International Williston Basin Symposium, Sask. Geol. Soc., Spec. Publ. No. 11, p Pitman, J.K., Price, L.C., and LeFever, J.A. (2001): Diagenesis and Fracture Development in the Bakken Formation, Williston Basin: Implications for Reservoir Quality in the Middle Member; U.S. Geol. Surv., Professional Paper 1653, 19p. Saskatchewan Geological Survey 9 Summary of Investigations 2013, Volume 1

10 Smith, M.G. and Bustin, R.M. (1995): Sedimentology of the Late Devonian and Early Mississippian Bakken Formation, Williston Basin; in Hunter, L.D.V. and Schalla, R.A. (eds.), Seventh International Williston Basin Symposium, Mont. Geol. Soc., p Smith, M.G. and Bustin, R.M. (1998): Production and preservation of organic matter during deposition of the Bakken Formation (Late Devonian and Early Mississippian), Williston Basin; Palaeogeography, Palaeoclimatology, Palaeoecology, v142, p Smith, M.G. and Bustin, R.M. (2000): Late Devonian and Early Mississippian Bakken and Exshaw black shale source rocks, Western Canada Sedimentary Basin: a sequence stratigraphic interpretation; Amer. Assoc. Petrol. Geol., Bull., v84, p Staruiala, A., Qing, H., and Chi, G. (2013): Preliminary analysis of lithology and facies in the Bakken Formation, southeastern Saskatchewan, Canada; in Summary of Investigations 2012, Volume 1, Saskatchewan Geological Survey, Sask. Ministry of the Economy, Misc. Rep , Paper A-6, 9p. van Geldern, R., Joachimski, M.M., Day, J., Jansen, U., Alvarez, F., Yolkin, E.A., and Ma, X.-P. (2006): Carbon, oxygen and strontium isotope records of Devonian brachiopod shell calcite; Palaeogeography, Palaeoclimatology, Palaeoecology, v240, p Veizer, J., Ala, D., Azmy, K., Bruckschen, P., Buhl, D., Bruhn, F., Carden, G.A.F., Diener, A., Ebneth, S., Godderis, Y., Jasper, T., Korte, C., Pawellek, F., Podlaha, O.G., and Strauss, H. (1999): 87 Sr/ 86 Sr, δ 13 C and δ 18 O evolution of Phanerozoic seawater; Chem. Geol., v161, p Zheng, Y.-F. (1999): Oxygen isotope fractionation in carbonate and sulfate minerals; Geochem. Jour., v33, p Saskatchewan Geological Survey 10 Summary of Investigations 2013, Volume 1