REPORT No. 52 The Faunas OF THE Lower Palaeozoic Carbonate Rocks in the Subsurface of Saskatchewan by JOHN E. BRINDLE 1960 I DEPARTMENT OF MINERAL RESOURCES Petroleum and Natural Gas Branch Geology Division HON. J. H. BROCKELBANK J. T, CAWLEY Min lat• Deputy Mlnlat• PROVINCE OF SASKATCHEWAN ABSTRACT The fossils studied in this report (over 80 species, principally coelenterates and brachiopods) were obtained from all well cores taken in the Lower Palaeozoic carbonate rocks of Sask, atchewan (Ordovician Bighorn and Silurian Interlake groups ) available to the writer to the end of September, 1959. The fauna! assemblage is presented from, and an age ascribed to each of the stratigraphic units in this succession. The Bighorn group appears to be of Upper Ordovician age for most of its thickness. The Ordovician,Silurian boundary may occur within the Stone, wall formation, the uppermost unit of the Bighorn group. The Interlake group appears to include both Lower and Middle Silurian strata. There is no evidence of angular unconformities or erosional gaps within or between the Ordovician and Silurian strata. Correlations are proposed between the Ordovician and Silurian carbonate rocks of Saskatchewan and those of eastern Montana, northern Wyoming and the outcrop areas of Man, itoba. The correlations of Porter and Fuller (1959, Amer. Assoc. Petrol. Geol., Bull., vol. 43, No. 1 ), and Ross (1957, U.S. Geol. Surv., Bull. 1021,M), are reinforced. The fossils are illustrated by photographs wherever possible. CONTENTS Page I .- INTRODUCTION.... ... .............. ·········································· ................................ .... ..... 7 I I .-ACKNOWLEDGMENTS ............... ················· ................................... .......... ··········· ........... ············ 8 III.- STRATIGRAPHY, SuccEss10N AND NOMENCLATURE..................................... 9 (a ) General... ....................................................................... ............................ ... ...... 9 (b ) Ordovician...................... ........... ........... ..... ..... .... ............ 11 (c ) Silurian..................................................................................... ... ........ 12 IV.- PALAEONTOLOGY, CORRELATION AND AcE............. ........................................... 12 A. ORDOVICIAN......... ........................ ····································· .................... ······ .................. 12 ( i ) Yeoman Beds .. ........................................................... ................................ 12 (ii) Herald Beds ....................................................................................................... 16 (iii) Stoughton Beds....... .......... ..................................................................... 17 (iv) Gunton Beds...................................................... ................................................... 18 (v) Stonewall Beds ................................................................................... 18 (vi) Age of the Ordovician Strata ............................................................ 19 B. SILURIAN .. ··· ··················································· ············· ·················· ...... 19 (i ) Rupert Beds. ..................................... ........... .......................... 19 (ii) Hanson Beds ......... ......... ................................................ 20 (iii) Risser Beds........................ ..................................................................... 22 (iv) Age of the Silurian Strata.................................................................. 22 Bibliography............... ... ............ ......... ........... ......... ... ....... ..... ... ...... ... ...... .... ...... ... ........... .... 23 Appendix.. ............................................................................................................ ............... .............................. 24 ILLUSTRATIONS Page PLATES-Plates I to VIII with explanations follow... ............................................. 29 FIGURES }.-Location Map ............................................................................................................... 9 2.-Characteristic Gamma Ray;Neutron well;log of the Lower Palaeozoic carbonate rocks of southeastern Saskatchewan............ IO 3.-Age and Correlation Chart of the Lower Palaeozoic rocks of Saskatchewan...................................................................................... .................................. 14 TABLE !.-Vertical Distribution of Species in the Lower Palaeozoic Carbonate Rocks in the Subsurface of Saskatchewan ......... 15; 16 I. INTRODUCTION The material on which this study is based consists of a collection of Lower Palaeozoic fossils from well cores taken in the Ordovician and Silurian carbonate rocks in the subsurface of the Province of Saskatchewan. The report is intended to supplement the available accounts of the stratigraphy of these rocks, notably those of the Saskatchewan Geological Society (1958 ), Porter and Fuller (1959 ), and Kent (1960 ), by pre~ senting an account of the faunal assemblages so far obtained from each of the stratigraphic subdivisions of these rocks in the subsurface of Saskatchewan. Correlations with adjacent areas based on these faunas agree with those already produced relying on "non~sequential" arenaceous and argillaceous "marker beds" within the carbonate succession (Saskatchewan Geological Society 1958, Cumming, Fuller and Porter, 1959 ). Fossils were collected from all cores taken in the Ordovician and Silurian carbonate rocks of Saskatchewan available to September 1959. 7 I I. ACKNOWLEDGMENTS The writer wishes tQ acknowledge the assistance and co­ operation of his colleagues in the Department of Mineral Resources during the course of this study. 8 III. STRATIGRAPHY, SUCCESSION AND NOMENCLATURE (a) GENERAL For detailed accounts of the stratigraphy of the Lower Palaeozoic rocks of Saskatchewan and adjacent areas the reader is referred to Porter and Fuller (1959 ), Saskatchewan Geological Society (1958 ), Kent (1960 ), Andrichuk (1959), Kupsch (1953 ), Stearn (1956), and Baillie (1951, 1952 ). In brief: Ordovician and Silurian carbonate rocks are present through, out the whole of the northern part of the Williston Basin and adjacent shelf areas south of the Canadian Shield in Saskatchewan and Manitoba, outcropping in southern and west-central Manitoba and east-central Saskatchewan. Figure 1 shows the erosional edges of the Ordovician and --~· ... BELT Mrs ' ~ ELE CQICSNOWY NA MfS. MONTANA PIER At Aleo •i1h,n which foult, wert colltcttd from well corn. Erost()rw,I ede;t of Ordovicion corbonolt 1troto. Ero,lonol edge ot Silurion stro10 . SC.IL[ IN WILCS ,oo $0 0 200 t-, ·t:::, t=::::1 • Fig. I- Location Map Silurian carbonate rocks in Saskatchewan and Manitoba. In Saskatche... wan these rocks reach a total maximum remaining thickness of some 1350 feet on the International Boundary in the southeast of the Province, the thickness decreasing northward to the erosional edge. 9 Over eastern Saskatchewan the lowest Ordovician carbonates (Yeo; man Beds) overlie the sandstones, silts tones and shales of the Winnipeg formation, also of Ordovician age, with apparent conformity. However, over part of western Saskatchewan the Winnipeg formation seems to be absent, and here the Ordovician carbonates appear to lie unconformably on the Cambrian and lower Ordovician sandstones and shales of the Dead; z W<l IMPERIAL HERALD No. l-31 52 Ls d. l-31-l-20W2 Q~ >:.a. 2276' ::;;w 0 ASHERN FORMATION NEUTRON RISSER BEDS 000 z <{ Q. ii: ::::, HANSON 9000 ::> 0 _j a: BEDS u'i (!) w w ::.:'.: Ji.. ..['IQ!.kl! _ _j <( 0 _J ,100 0 a: w :!E zt-- SIZOO RUPER T BEDS z a:: <l ~ii: •noo :3~(/) STONEWALL ------- BEDS -- :=:,.. t•oo GUNTON BEDS (/) ..,0 CD ,~oo Q. ::::, z 0 <{ a: 0 (!) z 0> a: KOO 0 (/) 0 I 0 a: (!) w 0 ai m a:: a: w w ~ a... a:: '700 a... YEOMAN ::> 0 w BEDS a:: ... HOO r WINNIPEG FORMATION to. 9941' Fig. 2- Characterlstlc Gamma Ray-Neutron well-log of the Lower Palaeo­ zoic carbonate rocks in southeastern Saskatchewan. 10 wood formation. Except for a small area in east;central Saskatchewan where Cretaceous rocks form the overlying deposits, the Silurian strata (Interlake group) of the Province are unconformably overlain by rocks of Middle Devonian age. The nomenclature used in this report for the Lower Palaeozoic car; bonate rocks in subsurface sections is shown in Figure 2, together with a typical gamma ray;neutron well;log. The nomenclature is that of the Saskatchewan Geological Society's Lower Palaeozoic Names and Corre; lations Committee (Saskatchewan Geological Society, 1958 ), except that the term Bighorn group has been substituted for Tyndall group as being more widely acceptable. The Rupert, Hanson and Risser Beds equate with the Lower, Middle and Upper Interlake Beds, respectively, of Porter and Fuller (1959). The use of the term "Beds" by a number of authors in this area (Saskatchewan Geological Society 1956, 1958; Porter and Fuller, 1959; Cumming, Fuller and Porter, 1959; Brindle, 1960) for para; time, marker;defined, stratigraphic units is retained here. The succession is divided into units using thin, "non;sequential" , elastic (argillaceous and arenaceous) "marker beds" of great extent, which represent very widespread temporary interruptions in the carbon; ate sedimentation. The units are believed to be para;time;rock units, or sedimentary stages (Saskatchewan Geological Society 1956, 1958; Porter