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The AAPG/Datapages Combined Publications Database

CSPG Bulletin

Abstract


Bulletin of Canadian Petroleum Geology
Vol. 12 (1964), No. 1. (March), Pages 1-100

Facies Analysis of the Redwater Reef Complex, Alberta, Canada

John Edward-Klovan

CONTENTS

  • ABSTRACT, Page 2
  • INTRODUCTION, Page 3
  • ACKNOWLEDGMENTS, Page 3
  • REGIONAL SETTING, Page 4
  • UPPER DEVONIAN STRATIGRAPHY, Page 4
  • METHOD OF INVESTIGATION, Page 9
  • REEF DEFINITION AND RECOGNITION, Page 10
  • CORE AS SAMPLES OF REEF LITHOLOGY, Page 11
  • GEOMETRY AND PALEOTOPOGRAPHY OF REDWATER REEF COMPLEX, Page 14
  • PETROGRAPHY, Page 20
    • Classification of Carbonate Particles, Page 20
    • Constituent Grains, Page 24
    • Discrimination of Matrix: Diagenesis, Page 29
  • DISTRIBUTION OF FOSSIL ORGANISMS, Page 29
  • ECOLOGICAL SIGNIFICANCE OF REDWATER FOSSILS, Page 34
  • ANALYSIS OF UPPER LEDUC, Page 44
  • UPPER LEDUC REEF DEVELOPMENT, Page 54
  • ANALYSIS OF COOKING LAKE EQUIVALENT AND MIDDLE LEDUC, Page 62
  • DEVELOPMENT OF REDWATER REEF COMPLEX, Page 71
  • CONCLUSIONS, Page 78
  • REFERENCES CITED

TABLES

  1. List of wells examined in the present study, Page 9
  2. Quantative analysis of Belgian reef limestones, Page 15
  3. Carbonate particle classification, Page 21
  4. Check list and distribution of fauna in Redwater reef complex, Page 30
  5. Distribution of major faunal taxa in upper 150 feet of Redwater reef complex, Page 33
  6. Facies analysis data sheet, Page 45
  7. Summary of Upper Leduc rock types, Page 47
  8. Summary of major rock types in Redwater reef complex, Page 64

FIGURES

  1. Location map of Redwater reef complex, Page 5
  2. Upper Devonian stratigraphic section in central Alberta, Page 6
  3. Late Cooking Lake shoals in central Alberta, Page 7
  4. Distribution of Woodbend reefs in Alberta, Page 8
  5. Structure contours on restored top of Leduc Formation, Page 17
  6. Topographic cross-section of Redwater reef, Page 18
  7. Topographic cross-sections normal to eastern margin of Redwater reef, Page 19
End_Page 1--------------------------
  1. Subdivisions of Leduc Formation, Page 32
  2. Bathymetric zonation of stromatoroids and corals, Page 37
  3. Distribution of organisms, Upper Redwater reef complex, Page 53
  4. Composite cross-section of Upper Leduc, Page 55
  5. Cross-section of Upper Leduc, through Egremont sector, Page 56
  6. Cross-section of Upper Leduc, through Amelia sector, Page 57
  7. Cross-section of Upper Leduc, through Simmons sector, Page 58
  8. Facies distribution in Upper Leduc, Page 59
  9. Percent organic-reef facies in Upper Leduc, Page 60
  10. North-south cross-section of Redwater reef complex, Page 73
  11. Distribution of major fossil types, Page 75
  12. Distribution of Duernay type sediments, Page 76
  13. Stages in development of Redwater reef complex, Page 79

PLATES

  • 1. Random sections through colonial organisms, Page 23
  • 2. Brachiopods from Redwater reef complex, Page 83
  • 3. Corals from Redwater reef complex, Page 85
  • 4. Corals from Redwater reef complex, Page 87
  • 5. Miscellaneous fossils from Redwater reef complex, Page 89
  • 6-9. Redwater rock types, Page 91

ABSTRACT

In this study of the Upper Devonian Redwater reef complex, cores from 37 wells were examined petrologically and paleontologically to classify the carbonate rocks. By grouping the data statistically, by means of an electronic digital computer, and visually, mappable facies were delineated within the upper 150 feet of the Redwater complex. From basin across the reef to lagoon these are:

  1. Megalodon facies--occurring along the outer edge of the complex.
  2. Tabular stromatoporoid facies--immediately reefward from the outer edge of the complex.
  3. Organic-reef facies.
  4. Massive stromatoporoid detritus facies--located lagoonward from the organic-reef.
  5. Skeletal calcarenite facies--intimately associated with the organic-reef facies.
  6. Back-reef facies--making up the bulk of the complex.
  7. Amphipora facies--occurring in the central part of the complex. Most of the rock types are illustrated.

Due to a lack of core control, the lower parts of the reef complex are not fully understood. The Beaverhill Lake sediments--argillaceous lime muds deposited in quiet water--form the reef foundation. These are followed by a carbonate shoal. (L. Leduc, Cooking Lake Formation) whose sediments and fossils indicate deposition under both highly turbulent and quiet-water conditions. The next two types of sedimentation resulted from a rapid increase in this shoal's rate of subsidence. The dark, argillaceous limestones of the Duvernay Formation were deposited in deep, quiet, restricted waters, while organic activity was accelerated in certain favored locations. This led to the development of organic-reef, not in the surf zone but in relatively deeper waters. These organic-reefs are characterized by tabular stromatoporoids. As the rate of subsidence slowed, the organic-reef was able to grow into relatively shallow waters, and its diagnostic fauna then became dominated by massive stromatoporoids.

The shallow-water organic-reefs restricted water movement on the complex so that islands and tidal flats developed behind them. These back-reef areas, characterized by non-skeletal sediments and a sparse fauna, actually formed the crest of the reef complex. In the interior parts of the complex a shallow, restricted lagoon developed in which the aberrant stromatoporoid genus Amphipora flourished.

End_Page 2--------------------------

Most of the common fossil organisms found in the carbonate rocks of the Redwater reef complex are illustrated. The study describes their distribution in the complex and discusses their ecological significance. This leads to a conclusion of major importance; that massive stromatoporoids indicate shallow-water, turbulent deposition, while tabular stromatoporoids characterize sediments laid down in deeper and quieter waters.


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