Document généré le 26 sept. 2021 12:17 Atlantic Geology Foraminiferal Study of the Magdalen Shallows, Gulf of St. Lawrence G. Vilks Volume 4, numéro 1, april 1968 URI : https://id.erudit.org/iderudit/ageo04_1rep05 Aller au sommaire du numéro Éditeur(s) Maritime Sediments Editorial Board ISSN 0843-5561 (imprimé) 1718-7885 (numérique) Découvrir la revue Citer cet article Vilks, G. (1968). Foraminiferal Study of the Magdalen Shallows, Gulf of St. Lawrence. Atlantic Geology, 4(1), 14–21. All rights reserved © Maritime Sediments, 1968 Ce document est protégé par la loi sur le droit d’auteur. L’utilisation des services d’Érudit (y compris la reproduction) est assujettie à sa politique d’utilisation que vous pouvez consulter en ligne. https://apropos.erudit.org/fr/usagers/politique-dutilisation/ Cet article est diffusé et préservé par Érudit. Érudit est un consortium interuniversitaire sans but lucratif composé de l’Université de Montréal, l’Université Laval et l’Université du Québec à Montréal. Il a pour mission la promotion et la valorisation de la recherche. https://www.erudit.org/fr/ Maritime Sediments, Vol. 4, No. 1, April 1968, pp. 4-6. Reports 14 Foraminiferal Study of the Magdalen Shallows, Gulf of St. Lawrence* G. VILKS Atlantic Oceanographic Laboratory, Bedford Institute, Dartmouth, N. S. Introduction This is a preliminary report on studies of Foraminifera taken from bottom sediments in the Magdalen Shallows (see Fig. 1). The purpose of the study is to compare Foraminifera found in the Gulf of St. Lawrence, the Arctic, and North Atlantic waters. The field program was carried out during late August of 1963 in cooperation with the Fisheries Research Board of Canada. Samples of bottom sediment were taken aboard CNAV "Sackville", Cruise S-75, with a modified Van Veen bottom grabber and processed at the Bedford Institute, using the conventional methods (Vilks, 1964). Grateful acknowledgement is extended to Dr. D. H. Loring of the Fisheries Research Board of Canada for cooperation and help given during the sampling, to Dr. G. A. Bartlett for much helpful auvice during the study, and to N. W. Fowler for assistance in the field and laboratory. Previous Work Literature used in the present study consists primarily of publications discussing Foraminifera from the Arctic (Loeblich and Tappan, 1953, Cushman, 1948, Phleger, 1952) and the Gulf of Maine (Parker, 1952a, b). Studies of Foraminifera in the Gulf of St. Lawrence are few. Dawson (1870) gave a faunal list and a few illustrations of Foraminifera from the Gaspe region. Sproule (1961) discussed distribution of benthonic Foraminifera taken from-the Magdalen Shallows and the Laurentian Channel. His report includes a faunal list but lacks illustrations of species. Bartlett (1965, 1966) described nearshore Foraminifera from the Miramichi Estuary and Tracadie Bay and Schafer (1967) reported on sampling problems of nearshore sediments. Physical Environment Bottom conditions on the Magdalen Shallows are characterized by low water temperatures, coarse sediment and relatively featureless submarine topography. According to Lauzier (1957), the waters of the Gulf of St. Lawrence are stratified in layers that have different temperature and salinity characteristics. Mainly three layers are recognized: the warm surface, the cold intermediate and the warmer layer below the intermediate. Over the Magdalen Shallows only two layers are present which vary in time and space. During the late summer the temperature of the surface layer is relatively high and may reach 16-17°C, but decreases sharply below a depth of approximately 10 metres. At approximately 50 metres it is 0. 0°C both in early spring and late summer. The sharp thermocline loses its identity in the autumn as the surface layer becomes thicker and cooler. In winter the whole area over the Magdalen Shallows is uniformly cold. The bottom temperature in the Gulf of St. Lawrence is, therefore, a function of bathymetry and the time of year. The range of depth over the central part of the Magdalen Shallows is between 40 arid 90 metres and is within the cold intermediate layer with small seasonal changes in temperature taking place. The shallower nearshore localities are within, or close to, the surface layer and are exposed to drastic changes in seasonal temperature. The nearshore localities are also exposed, to lower salinities with respect to the central part of the Shallows. During the cruise, salinities at the bottom were recorded from 30. 784 to 32. 383 parts per thousand with the lesser values at the nearshore stations. The bottom sediment collected consists chiefly of reddish-brown sand. In addition to the sand a number of samples contain pebbles and cobbles of red sandstone. In the vicinity of the Magdalen Islands the bottom is dominated by clean and well-sorted sand, but in the vicinity of Prince Edward Island the sediment is less well-sorted and contains mud in addition to pebbles mixed with the sand. Discussion of Species The relatively small foraminiferal population of the Magdalen Shallows is dominated by arenaceous species, (See Table I). In this report the more abundant species are treated in some ^Manuscript received May 24, 1968; Bedford Institute Contribution No. 123. Reports 15 GULF OF ST LAWRENCE O SAMPLING STATION SCALE OF MILES 0 50 O 34 Q32 037 039 041 024 Q43 MA6DALEN 019 045 044 ISLANDS Q52 053 054 058 057 056 060 085 Figure 1 Location of sampling stations in Magdalen Shallows, TABLE I. Relative percentages of Foraminifera. Actual number of species in parentheses if less than one test per 10 grams of sample. Station Number 24 19 66 65 64 63 43 52 41 61 54 60 58 53 44 85 39 37 34 56 57 45 32 Depth in Metres 13 37 37 40 42 46 51 55 55 55 58 60 60 60 60 60 60 60 64 64 64 68 77 Tests per gm of Sample 1 35 18 22 28 1 63 7 15 20 25 31 U 19 19 16 13 35 50 8L 13 38 Total Foraminifera 28 1358 1178 1315 1321 58 2308 436 965 1001 696 1334 613 316 410 486 576 1223 906 1936 ZOO 810 Adercotrvma slomer^tum (1) (4) (3) (2) {1) (1) 9. 0 2. 5 1. 0 0. 3 2. 8 0. 8 Ammotium cas^jp (I) (3) (I) (2) (2) 0) 0. 2 Anguloeerina angulosa (1) (1) Asterellina pulchnllR. (1) (5) (1) (5) 1.1 2.1 (2) (6) (3) Astrononion eallowavi (1) Bieenerina arctlca 5.2 14. .4 20. 2 4.1 25. 6 6. 9 4. 6 28. 2 0. 9 25.1 5. 6 10. 8 8.1 1. 8 10. 5 5.1 1.9 6. 2 16. 7 Bolivina oseudooun<;t^ta (4) Buccella frigid^ 2. 3 0. 9 1. 2 (1) 0. 3 1. 4 2. 6 0. 8 12. 9 2. 5 5. 0 5. 4 3. 8 9. 5 14. 7 Buliminft 0.4 B, marginata 0. 5 (3) 2.1 0. 2 Cibicides lobatulus (3) (1) (3) (2) Cribrostomoides bra^yi (1) (I) C. crassimargo 0. 4 (I) 4. 3 1. 2 (1) 1.1 (21 (6) 2. 8 6.9 2. 4 2. 4 (I) (2) C. ieffrevsi (1) (2) C. sube;lobosum (1) 0. 2 Eggerella ad vena 96. 4 89. 6 70. 8 58. 5 73. 0 77. 6 8. 9 76. 7 63. 0 43. 6 13. 5 17.9 24.1 48. 8 29. 3 11. 4 2.1 1. 6 16. 4 18. 3 (1) Elphidium bartletti 0. 5 (2) (2) (4) (1) I. 3 1. 9 0. 6 E. incertum 0. 4 (4) 1. 4 26. 6 6. 8 4.1 2. 5 15. 3 43. 9 3. 4 3. 2 21. 2 7. 9 E. subarcticum (2) 0. 6 I. 3 Globigerina sp. (4) Glomospira qordialis (I) (1) (2) 0. 9 (3) 1.1 (1) (3) 0. 5 0. 7 (2) Hippocrepina indivisa (1) Hyperammina sp. (I) Islandiella islandica (I) (2) 1. 2 0. 7 3. 9 (1) 3. 0 2. 9 (3) 6. 5 7. 3 4. 4 I. norcrosai (I) 0. 7 I, teretis (1) (2) 2. 7 0. 5 2.1 (1) (1) 3. 2 19. 2 5. 0 4. 3 6, 3 0) 10. 3 Lapena mollis (1) Miliammina fusca (1) (2) 1.1 0. 7 Nonionella auricula (I) 1. 5 2. 5 (2) 2. 7 I. 7 2. 4 (3) 1. 0 0.9 2. 5 2. 8 (3) Nonionellina labradorica (1) (I) (4) 0. 5 (1) (5) 0. 5 0. 5 0) 2. 9 0. 6 5.1 2. 3 0. 6 I. 7 o. Oolina scalariforme-sulcata (0 Protelphidium orbiculare 2.1 (I) (D 0. 6 (1) (2) I. 6 0. 4 (U 0. 2 Proteonina atlantica (1) (2) (3) 0. 6 (0 (4) 0. 6 (I) (11 Pseudopolvmorphina novaneliae U) Recurvoides turbinatus (1) 2. 0 (2) 1.1 (I) 10. 3 I. 1 3. 0 3. 3 1. 8 2. 7 2. 4 1. 4 I. 5 5. 5 6. 7 2. 7 Reophax curtus (4) (1) (1) (1) 0. 5 U) (3) 2. 8 (1) 0. 7 2. 1 1. 3 0. 8 3. 9 (D 2. 8 R. scotti 6. 2 (I) I. 6 (1) (1) 34. 1 61. 5 24. 3 Spiroplectammina biformis (3) 6. 2 13. 0 15. 0 8. 6 38. 6 (3) 17. 7 19. 7 11. 6 27. 8 31. 2 12. 7 20. 7 14. 6 36. 3 14. 5 Textularia torquata I. 5 1.1 5. 8 5.1 21.1 4.1 6. 8 3. 4 7. 3 U. 9 9.6 1. 9 8.1 9.1 13.