ERCB/AGS Open File Report 2011-07 Measured Outcrop Section T27-R17W4-01 of the Bearpaw and Horseshoe Canyon Formations, Dorothy, Red Deer River Valley, Southern Alberta (NTS 82P/08) ERCB/AGS Open File Report 2011-07 Measured Outcrop Section T27-R17W4-01 of the Bearpaw and Horseshoe Canyon Formations, Dorothy, Red Deer River Valley, Southern Alberta (NTS 82P/08) B. Hathway, C.J. Banks, D.C. Hay, G.J. Prior, S. Mei, D. Chen and J.A. Weiss Energy Resources Conservation Board Alberta Geological Survey June 2011 ©Her Majesty the Queen in Right of Alberta, 2011 ISBN 978-0-7785-8648-7 The Energy Resources Conservation Board/Alberta Geological Survey (ERCB/AGS), its employees and contractors make no warranty, guarantee or representation, express or implied, or assume any legal liability regarding the correctness, accuracy, completeness or reliability of this publication. Any reference to proprietary software and/or any use of proprietary data formats do not constitute endorsement by ERCB/AGS of any manufacturer's product. If you use information from this publication in other publications or presentations, please acknowledge the ERCB/AGS. We recommend the following reference format: Hathway, B., Banks, C.J., Hay, D.C., Prior, G.J., Mei, S., Chen, D. and Weiss. J.A. (2011): Measured outcrop section T27-R17W4-01 of the Bearpaw and Horseshoe Canyon formations, Dorothy, Red Deer River valley, southern Alberta (NTS 8 2P/08); Energy Resources Conservation Board, ERCB/AGS Open File Report 2011-07, 16 p. Published June 2011 by: Energy Resources Conservation Board Alberta Geological Survey 4th Floor, Twin Atria Building 4999 – 98th Avenue Edmonton, AB T6B 2X3 Canada Tel: 780.422.1927 Fax: 780.422.1918 E-mail: [email protected] Website: www.ags.gov.ab.ca ERCB/AGS Open File Report 2011-07 (June 2011) • iii Contents Acknowledgments.........................................................................................................................................v Abstract........................................................................................................................................................vi 1 Introduction ............................................................................................................................................1 2 Location..................................................................................................................................................1 3 Description .............................................................................................................................................1 3.1 0 to 2.5 m: Bearpaw Formation – Dorothy Sandstone ..................................................................1 3.2 2.5 to 17.6 m: Bearpaw Formation Mudstone...............................................................................1 3.3 17.6 to 29.5 m: Bearpaw Formation – Dorothy Bentonite............................................................1 3.4 29.5 to 78.0 m: Bearpaw Formation Mudstone and Sandstone.....................................................7 3.5 78.0 to 87.5 m: Horseshoe Canyon Formation Sandstone ............................................................9 4 Gamma-Ray Data.................................................................................................................................10 5 Summary ..............................................................................................................................................12 6 References ............................................................................................................................................13 Appendix 1 – GPS Location Data for Measured Outcrop Section T27-R17W4-01...................................14 Appendix 2 – Graphic Log of Measured Outcrop Section T27-R17W4-01 (Southern Alberta) with Outcrop Gamma-Ray Curve. Large-Format Version of Figure 3 with Descriptive Notes...................15 Appendix 3 – Outcrop Gamma-Ray Methodology.....................................................................................16 GR-135 Specifications .........................................................................................................................16 Figures Figure 1. Simplified geological map (modified from Hamilton et al., 1999) showing the distribution of Bearpaw and Horseshoe Canyon formations and surrounding rocks in Alberta and the location of measured section T27-R17W4-01..........................................................................................2 Figure 2. Location of measured section T27-R17W4-01 (southern Alberta) plotted on 1 m resolution orthorectified airphoto base with 1 km grid (UTM Zone 12, NAD 83). ....................................3 Figure 3. Graphic log of measured section T27-R17W4-01 (southern Alberta) with outcrop gamma-ray curve.. .........................................................................................................................................4 Figure 4. Panoramic view looking northwest (viewpoint at 407750E, 5680360N, UTM Zone 12, NAD 83) toward middle and upper part of measured section T27-R17W4-01 (above the lateral shift at the base of the Dorothy bentonite)..............................................................................................5 Figure 5. Dorothy sandstone exposed on the southwest bank of the Red Deer River. .................................6 Figure 6. Erosionally based swale truncating horizontal planar stratification in the uppermost part of the Dorothy sandstone at 2 m in measured section T27-R17W4-01 (southern Alberta)..................6 Figure 7. Bioturbated contact between the Dorothy sandstone and overlying mudstone at 2.5 m in measured section T27-R17W4-01 (southern Alberta)................................................................7 Figure 8. Upper part of coarsening- and thickening-upward mudstone and sandstone package extending up to 69.6 m (at the level of the top of the bluff in the photo) in measured section T27- R17W4-01 (southern Alberta). ...................................................................................................8 Figure 9. Detail of sandstone units in upper part of Figure 8 (measured section T27-R17W4-01, southern Alberta).......................................................................................................................................8 Figure 10. Hummocky cross-stratification in fine-grained sandstone bed. Base of unit (indicated by arrow) at 66.6 m in measured section T27-R17W4-01 (southern Alberta). ...............................9 Figure 11. Ball-and-pillow soft-sediment deformation in sandstone at top of coarsening- and thickening- upward package... .....................................................................................................................10 Figure 12. Amalgamated, erosionally based, swaley cross-stratified, fine-grained sandstone units in the basal Horseshoe Canyon Formation ‘Appaloosa sandstone’ interval of measured section T27- R17W4-01 (southern Alberta). .................................................................................................11 ERCB/AGS Open File Report 2011-07 (June 2011) • iv Acknowledgments We are grateful to D. Hodgson (landowner) for permission to work on his property. J. Dawson is thanked for careful technical editing. ERCB/AGS Open File Report 2011-07 (June 2011) • v Abstract Measured outcrop section T27-R17W4-01, located 34 km southeast of Drumheller on the southwest side of the Red Deer River valley opposite the village of Dorothy, includes the upper part of the Bearpaw Formation and the lowermost part of the Horseshoe Canyon Formation. This report includes a graphic log of the measured section with an outcrop gamma-ray curve and a detailed description of the section (avoiding lithofacies interpretation but detailing stratigraphic context where appropriate) with selected photos. The Bearpaw Formation interval includes the upper part of the Dorothy sandstone at the base of the section and the Dorothy bentonite. The bioturbated contact of the Dorothy sandstone with overlying mudstone is marked by the most pronounced increase in gamma-ray counts in the measured section. Gamma-ray counts and observed lithofacies for the Bearpaw Formation interval above the Dorothy sandstone define a series of coarsening-upward packages. Mean gamma-ray counts for the basal part of each coarsening-upward cycle become progressively lower up through the section. In the two best-defined cycles, grey-brown mudstone passes gradationally up into intervals dominated by hummocky cross- stratified, fine-grained sandstone units. The 11.9 m thick Dorothy bentonite shows relatively uniform gamma-ray counts in the middle range of values for the measured section. The base of the Horseshoe Canyon Formation is placed at the base of a thick (9.5 m exposed) swaley cross-stratified sandstone interval at the top of the measured section. ERCB/AGS Open File Report 2011-07 (June 2011) • vi 1 Introduction Measured outcrop section T27-R17W4-01, located in the Red Deer River valley, 34 km southeast of Drumheller (Figures 1 and 2), includes the upper part of the Bearpaw Formation and the lowermost part of the Horseshoe Canyon Formation. The Bearpaw Formation interval includes the upper part of the ‘Dorothy sandstone’ and the ‘Dorothy bentonite’ of Given and Wall (1971). This report includes a graphic log of the measured section with an outcrop gamma-ray curve and a detailed description of the section (avoiding lithofacies