Current Research (2003) Newfoundland Department of Mines and Energy Geological Survey, Report 03-1, pages 127-136 ORDOVICIAN GASTROPODS FROM WESTERN NEWFOUNDLAND D.M. Rohr, W.D. Boyce1 and I. Knight 1 Sul Ross State University, Alpine, TX ABSTRACT Lower and Middle Ordovician gastropods from the Peabody Museum, Yale University, are described and illustrated to supplement the material previously known from western Newfoundland. Lower Ordovician Lecanospira compacta (Salter, 1859) and Euconia etna (Billings, 1865) are described and placed in their current stratigraphic context. The common but poorly known Lytospira (=Ecculiomphalus) distans (Billings, 1865), from the Cow Head Breccia is redescribed. The genus Subulties Emmons, 1842, is described for the first time from the Upper Ordovician of Newfoundland. INTRODUCTION LITHOSTRATIGRAPHY Beginning in 1910, C. Schuchert, W.H. Twenhofel and AUTOCHTHONOUS ROCKS C.O. Dunbar conducted field work in western Newfound- land. Large collections of Cambrian and Ordovician fossils The St. George Group is a 500-m-thick succession of were brought back to Yale University’s Peabody Museum, subtidal and peritidal limestone and dolostone, widely where they reside today. The results of the stratigraphic exposed in western Newfoundland (Figure 1). It is divided research on the areas were summarized in Schuchert and into the Watts Bight, Boat Harbour, Catoche and Aguathuna Dunbar (1934). The diverse Ordovician gastropod fauna formations (Knight and James, 1987, 1988 - see Figure 2). was being prepared as part of a doctoral dissertation by E.I. The Barbace Cove Member of the Boat Harbour Formation, Leith (Schuchert and Dunbar, 1934), but it was not com- the Catoche Formation and the Aguathuna Formation of the pleted. Part of the collection is described and illustrated St. George Group form an unconformity-bounded, late here. This complements our previous work on the gas- Canadian to Whiterockian sequence. tropods of western Newfoundland (Rohr et al., 2000, 2001, 2002; Rohr and Measures, 2001), part of a continuing study The Table Head Formation (Figure 2)was originally supported by the Geological Survey of Newfoundland and established by Schuchert and Dunbar (1934). Klappa et al. Labrador, National Geographic Society Committee for (1980) elevated the Table Head to group status, and the Research and Exploration and Sul Ross State University. lower 250 m of predominantly carbonate rocks were named the Table Point Formation. The Table Point Formation con- The Ordovican gastropods in the Peabody collections sists mostly of thick to massive, bioclastic limestone, but are from both the autochthonous and allochthonous Ordovi- includes lesser algal sponge wackestone to packstone, and cian sequences of the outer domain of the Humber algal oncolitic wackestone (Stenzel et al., 1990). The (tectonostratigraphic) Zone in western Newfoundland. They upward-deepening environments of deposition include tidal include many of the same taxa described and illustrated by flat, lagoon, shoal, and sponge bioherms (Klappa et al., Billings (1865), but there are also some other and better pre- 1980). Ross and James (1987) established the Spring Inlet served taxa. Member for the lower 10 to 40 m of peritidal carbonate rocks of the formation, and they concluded that the forma- The Peabody Museum specimens discussed here are tion is within the Anomalorthis brachiopod zone. The Spring from Port au Port Peninsula, the Cow Head area and south Inlet Member (in fact, the bulk of the Table Point Forma- of Port au Choix Peninsula (see Figure 1 and Appendix). tion) lies within the Histiodella tableheadensis conodont 1 Regional Geology Section 127 CURRENT RESEARCH, REPORT 03-1 OI OI OI OI OI 59 00 58 00 57 00 56 00 52 00 Belle Isle LOCATION OF Carboniferous MAP AREA basins É y a B Taconian t QU BEC le allochthons LABRADOR sle to I is e P ell Proterozioc B basement + f o supracrustal it ra T cover St L U A F Hare Bay KE LA OI 51 00 OI 51 00 E IL M 050 100 150 km N E B1946 T Canada Bay Two Hill SYMBOLS Point IF Thrust contact ................................... S S Structural base of Taconian B3849, A M allochthon ......................................... B3971 Fault .................................................. Lower E Basal Cambrian unconformity ............. Head G N A Carboniferous unconformity .............. R OI OI 50 00 50 00 GA - Goose Arm G WG - Weasel Group N O PL - Pinchgut Lake Formation L Bonne Bay WG LEGEND Bay of Islands GA CARBONIFEROUS Sedimentary rocks OI OI 49 00 B3951 SILURIAN-DEVONIAN 49 00 Long Point Granites PL ORDOVICIAN-DEVONIAN Sedimentary and volcanic rocks Port au Port Peninsula CAMBRIAN-ORDOVICIAN ALLOCHTHON Ophiolite complexes Sedimentary rocks/mé lange B3890 Weasel Group Green Head Platformal rocks including Reluctant Head Formation AUTOCHTHON OI 0 25 50 Platformal rocks OI 48 00 48 00 km CAMBRIAN-PROTEROZIOC Metasedimentary rocks PROTEROZOIC Crystalline basement OI OI OI OI 59 00 58 00 57 00 56 00 Figure 1. Geological terranes in western Newfoundland. Arrows indicate areas sampled for gastropod fossils. 128 D.M. ROHR, W.D. BOYCE AND I. KNIGHT HIATUS Misty Point fm. 500 metres Caradoc Winterhouse Fm. Long Point Gp. 0 Lourdes Fm. Humber Arm Allochthon American Tickle & Mainland Sandstone fms. ORDOVICIAN Llanvirn Gp. Goose Tickle Cape Cormorant Fm. Black Cove Fm. Table Cove Fm. Table Head Gp. Table Point Fm. Aguathuna Fm. Arenig Catoche Fm. Gp. Boat Harbour Fm. Tremadoc St. George St. Watts Bight Fm. Figure 2. Stratigraphic column of Ordovician formations in western Newfoundland (modified from Williams et al., 2001). zone of Stouge (1984). The uppermost 16 m of the Table form, shelf–slope carbonates. It consists of massive lime- Point Formation and the lower 70 m of the Table Cove For- stone conglomerate and breccia intercalated with ribbon mation lie within the Histiodella kristinae conodont zone limestone, grainstone and shale, transported into deep water (Stouge, 1984, page 19, Figure 18). by a variety of gravity processes. At Lower Head (Figure 1), in Gros Morne National Park, spectacular conglomerates are Schuchert and Dunbar (1934) established the Long exposed; these are correlative with bed 14 of the Factory Point series, which is now the Long Point Group. Most Cove Member of the Shallow Bay Formation on the Cow recently it has been subdivided into three formations by Head Peninsula (James and Stevens, 1986). The Lower Quinn et al. (1999) – in ascending order, the Lourdes, Win- Head conglomerates contain several large fossiliferous terhouse and Misty Point formations (Figure 2). Schuchert blocks of Middle Ordovician light-coloured limestone. and Dunbar (1934, page 70) collected Subulites and Maclu- These blocks, which are of shallow-water origin and contain rites from bed 3 of their Long Point series. Locality B3951 gastropods, are assigned to the Whiterockian-age Orthidiel- (see Figure 1 and Appendix) is located north of Long Point la brachiopod zone (Ross and James, 1987). lighthouse at the north tip of Long Point. This bed is proba- bly part of what is now the Winterhouse Formation of SYSTEMATIC PALEONTOLOGY Bergström et al., (1974), which is middle to late Caradoc in age (Quinn et al., 1999). REPOSITORY OF ILLUSTRATED MATERIAL ALLOCHTHONOUS ROCKS The specimens illustrated in this report are housed in the Invertebrate Paleontology Division, Peabody Museum The tectonically allochthonous Cow Head Group (Mid- of Natural History, Yale University, New Haven, Connecti- dle Cambrian to Whiterockian) is a succession of periplat- cut, USA. 129 CURRENT RESEARCH, REPORT 03-1 Systematic Descriptions Figured specimens. YPM 3450, 35912. Superfamily EUOMPHALOIDEA de Koninck, 1881 Genus Lecanospira Butts, 1926 Family EUOMPHALIDAE de Koninck, 1881 Genus Lytospira Koken, 1896 Type species. Ophileta compacta Salter, 1859, from the Beauharnois Formation (Beekmantown Group) of Type species. Euomphalus angelini Lindström, 1884, from Beauharnois, Québec. the Orthoceras Limestone (Middle Ordovician) of Sweden. Lecanospira compacta (Salter, 1859) Lytospira distans (Billings, 1865) Plate 3 Plate 1-1, 1-2; Plate 2-1, 2-2 For complete synonymy see Desbiens et al., 1996. 1865 Ecculiomphalus distans (n. sp.) Billings, pages 249-250, Figure 235. Description. Discoidal shell with slightly concave base, 2001 Lytospira angelini (Lindström, 1884); Rohr and concave top. Internal mold with some shell material remain- Measures, page 291, figures 7, 8.9-8.19. ing. Whorl crest on internal mold sharp; growth lines curing sharply back from suture; base of whorl rounded Description. Large (up to 13 cm in diameter), discoidal shell having whorls widely out of contact, coiled in a regular spi- Discussion. Lecanospira Butts, 1926, is a common genus in ral curve; spacing between whorls about twice the width of the Lower Ordovician rocks of eastern North America, the previous whorl; round cross section with a slightly flat- being found in Texas, Missouri, Alabama, Virginia, Mary- tened base and inner whorl and angular crest located at mid- land, Pennsylvania, New York, Québec and Newfoundland. dle or slightly outward of top surface; whorl width increas- It has been used as a biostratigraphic zone within the Cana- es about four times with each volution. Coarse lamella indi- dian Series (Yochelson and Copeland, 1974). The oldest cate a broad, deep sinus at crest of whorl. Growth lines con- occurrences of the genus are from the early Tremadoc (Early cave-forward on base and sweeping back convexly on both Canadian Series, Gasconadian Stage)