TITLE FOR BINDING - SPINE LATE QUATE~~ARY SEDIMENTARY ENVIRONMENTS, SEPT-ILES, P.Q. LATE-QUATE~~ARY SEDDŒNTARY ENVIRONME~~S, SEPT-ILES, QUEBEC by Lynda A. Dredge ABSTRACT The thesis presents the results of a geomorphological investigation at Sept-Iles, Quebec. Six sedimentary environments are identified, described, and arranged into a stratigraphie column: till, outwash, offshore and nearshore deposits, fluvial accretions, and peat. Landscape development is th en explained by incorporating the environments into a late- and post-glacial framework. An uplift curve generated from stratigraphie evidence and two radiocarbon dates indicates that the final deglaciation, synchronous with the marine limit at 128 m asl, occurred at about 9,300 years BP. Although no breaks in the late-Quaternary sedimentary sequence have be(::i'1 detected, the slope of the uplift curve suggests that a non-glacial phase ::-Uij· ha~e occurred at about 12,500 BP. :~.:)c. '!"hesis :x:?ar::::c:1: of Gcogra?h:; ~cGil1 [:1i~ersit~ ~o:1=real 110. ?Q. LES HILIEUX SEDU-Œ~'TAlRES DU TARDI-QUATERNAIRE SEPT-ILES, QUEBEC par Lynda A. Dredge RESUHE Le mémoire de recherche présente certaines interprétations géomorphologiques de la région des Sept-Iles au Québec. L'auteur y reconnalt six milieux sédÜDentaires qui sont décrits et classifiés en une séquence stratigraphique; ce sont le till, les dépôts de dé­ lavage, les dépôts d'avant-côte, les formations littorales et para­ littorales, les accumulations fluviatiles et la tourbe. Le façonne• ment et l'évolution morphologique du paysage s'expliquent ensuite en insérant ces traits du milieu dans le cadre du post- et du tardi­ Glaciaire. La stratigraphie et deux dates déterminées au radiocarbone nous permettent de tracer une courbe du soulèvement isostatique. Cette courbe indique que la fin de la déglaciation associée à la limite marine sise maintenant à 128 m se produisit il y a environ 9300 ans. Enfin, même si l'auteur n'a pu déceler aucune interruption à ~ra·.. ers la séquence s~dL"':lentaire du Quaternaire récent, la pente de la courbe du soulè:vc::Jent isostatique nous per::let de penser qu'une ?hasc ~on glaciaire a pu survenir il a environ 12,500 ans. LATE -QUATERNARY SEDIMENTARY ENVIRONMENTS, SEPT-ILES, QUEBEC Lynda A. Dredge A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfilment of the requirements for the degree of Master of Science :)c?a:-:::-.c:;: 0: Gcol;rap:,:: ~cGill ~ni~crsit~ ~onacal 110. :'.Q. ';-'Jl::, 1<:171 . JO· ~: -_.# . PREFACE The thesis presents the results of a geomorphological investigation conducted in the Sept-Iles area. It attempts to describe and explain the characteristics of the present landscape in terms of a sequence of sedtmentary environments produced during the late Quaternary. The information provides a model for deglaciation aiong the central portion of the North Shore. Since many of the descrip­ tions allude to conditions of slope failure, sources of construction materials, drainage problems, and land-use potential, the geomorph­ ological report may also assist those concerned with the proper economic development of the region. The writer wishes to express particular thanks to Dr. R.W. Pryer and Mr. F. Guerre of the Quebec North Shore and Labrador Rail­ way for their constant co-operation and for lending maps, borehole records and photographs; to the Iron Ore Company of Canada for financial assistance; and to the Geological Survey of Canada for financial support and for the radiocarbon dating of shell and wood sacples. - i - TABLE OF CONTENTS Page PREFACE. • . i TABLE OF CONTENTS........................................... i i LIST OF FIGURES ............................................. iii LIST OF PHOTOGRAPHS..... • . • . i v SECTION l INTRODUCTION 1.1 General Physiography.......... .....•.. ........ l 1.2 Bedrock Geology........... • . 6 1.3 Previous Work................................. 7 1.4 The Present S tudy. • . • . 7 II SEDIMENTARY ENVIRONMENTS 2.1 "Sedimentary Environments"................ .... 9 2.2 Till.......................................... 12 2.3 Glacial-fluvial Outwash....................... 17 2.4 Estuarine Sediments.................. • . 22 2.5 Coas tal Depos i t9 . 30 2.6 Fluvial Accretions... ...........•..•.......... 39 2. 7 Organic Accumulations. 45 2.8 Modification Morphology.. ..... .............•.. 50 aeol1an modification. .. .•..... .• . .•. .. 50 soHs development........................... 51 mass movement. • . • . • . • . • . 52 III THE EVOLUTION OF THE LANDSCAPE 3.1 Post-glacial Uplift.. .......... ............... 56 3.2 Stratigraphie Suumary......................... 66 3.3 Orientation of the Landscape Model: Correlations................................ 74 IV CONCLUSIONS 4.1 An Evaluation of the Study........... ......... 83 4.2 ProposaIs..................................... 85 \' APPENDICES 5.1 Faunal Assemblages...... ...................... 88 5.2 Ste. ~rguerite River Terraees........ ........ 89 5.3 Additionsl Stratigraphie Sections. ....... ..... 89 5.4 Granulometrie Analyses. '. .. ... ... ... .. 94 r L RE FERENCES - i i - LIST OF FIGURES Page 1. Reference locations.................................... 2 2. The location of cross-sections.. ........ ... ............ 3 3. General physiography...... ......... ... ........... ...... 4 4. A model for sedtmentary environments.......... ..•...... 10 5. Borehole at the docking facilities..................... 14 Q. Granulometric characteristics of till........ .•........ 16 7. Granulometric characteristics of outwash: changes with dis tance. • . • . • . • . • . • . • . • . • . 21 8. Vieux post section: size and sorting differences.. ..... 23 9. Granulometric characteristics in the estuarine sequence 28 10. The deep borehole at Sept-Iles. ........... ...•.... ..... 29 11. Texturai changes along a set of prograding beach ridges 33 12. Granulometric characteristics of beach sands........... 34 13. Macrotopography and stratigraphy of the forcl~nd....... 36 14. Macrotopography and stratigraphy of the clay fIat. ..... 37 15. Reworking of the exposed delta surface................. 41 16. Texturai changes in a point bar deposit.......... ...... 42 17. River terraces..................... .•.................. 44 18. Pollen profiles for Matamek............................ 49 19. Calculation of the uplift curve........................ 60 20. Uplift and emergence curves for Sept-Iles.............. 63 21. The pattern of emergence.......... ..................... 64 22. The stratigraphie column............................... 67 23. Geomorphology. • . 73 24. The correlative problern: elimination of multiple hypotheses............................................. 75 25. List of oolluscs collected...... ... ....... ............. 88 26. Additional alti::letric tra"Jerses........................ ~o 27. The sievc colu::II1....................................... ':15 - i:: - LIST OF PHOTOGRAPHS Page 1. Daigle till: type section.............................. 15 2. Crest of the south end moraine.............. ..... ... ... 15 3. Rapides reworked till: structures in the upper metre... 15 4. Daigle channel: a rock-eut channel filled with glacio- fluvial outwash........................................ 20 5. Longitudinal section illustrating structures in the Daigle outwash plain.. • .. .. • . 20 6. Type deposits at milepost 10: banded silty c1ays....... 27 7. The Airport section: beach sands overlying restructur- ed fine sands.......................................... 27 8. The lower boundary of unit 2....... .•...•.............. 27 9. Beach bedding at the marine limit, 128 m asl........... 32 10. Beach structures, type section at Mile 3....... ........ 32 Il. Cross-section of a beach ridge at Mile 3... .......•.... 32 12. The foreland........................................... 40 13. Cross-section of an interdistributary channel...... .... 40 14. Draped structures in an aeolian dune................... 40 15. Macrotopographyof the scarp-foot bog: subdued relief.. 48 16. Microtopography: string and desiccated pool.... ........ 48 17. Restricted basal drainage.............................. 48 18. Vieux Post section..................................... 54 19. The gully flow, 1966................................... 54 - 1 - SECTION l INTRODUCTION Sept-Iles is located on the northern shore of eastern Quebec (Figure 1). Along much of this portion of the coast, the St. Lawrence estuary is flanked by an abruptly rising escarpment which defines the southern boundary of Bostock's Laurentian Highland Division of the Canadian Shield. A series of rivers flow southwards from the Shie1d into the St. Lawrence. Many have a postglacial origin; the largest, however, flow through deeply incised channels which predate the last glaciation. In the bays and inlets associated with these major rivers aprons of recent sediments form coastal terraces. The Sept-Iles region is one of these areas which is dominated by an extensive sandy plain. 1.1 General Physiographv Carl Faessler (1942a, 1942b, 1945, 1948) has divided the area into two major physiographic units, the Laurentian foreland and the Champlain plaiT.1. A well-defined escarpment, about 65 metres high, separates the two zones. The upland is a prominent chain of low hills, having a mean elevation of about 150 metres. Large quantities of sandy till and out­ .... 3sh were deposited bl' glaciers which over-rode the area. These sedi­ cents have infilled former valleys and hillsides, producing a surface of subdued relief. Tnc lo.er surface is a sand and clay plain built by