"Seismic Investigations of Glaciers on Axel Heiberg Island" Submitted to the Graduate Faculty in Partial Fulfillment of the Requirements for the Master of Science Degree B. B. Redpath McGill University Department of Geology August 1964 TABLE OF CONTENTS Page ACKNOWLEDGMENTS 1 INTRODUCTION 2 GEOGRAPHY AND GEOLOGY OF AXEL HEIBERG ISLAND AND EXPEDITION AREA 3 REFRACTION ME THODS 10 REFLECTION METHODS 24 CONCLUSIONS 42 APPENDIX A - INSTRUMENTS 44 APPENDIX B - LOGISTICS 48 BIBLIOGRAPHY 52 1 ACKNOWLEDGMENTS The author wishes to thank Dr. Fritz Müller, leader of the Arctic Research Expedition to Axel Heiberg Island, for his leadership in the field and his encouragement during the writing of this paper. Gratitude is also expressed towards Dr. Vincent Saull for initially suggesting the project and for his continuing interest and many helpful suggestions. The author also wishes to thank Keith Smith, who provided valuable assistance in the field; Alex Becker, whose help in the field and gravity data were greatly appreciated; Colleen Doyle, who assisted with much of the drafting and preparation; the Carnegie Institute, which provided financial assistance for the project; and the Physics Department of the University of British Columbia which made the seismic equipment avail­ able on loan. Grateful thanks are also expressed to many other in­ dividuals who, by their contribution of time, effort and needed advice, all helped in the execution of this phase of the Arctic Research Expedition to Axel Heiberg Island .. 2 INTRODUCTION The work outlined in this the sis was a part of the pro gram of glacial studies undertaken by the Arctic Research Expedition to Axel Heiberg Island, N. W. T. , during the summer of 1960. The expedition was organized for the purpose of investigating the fields of glaciology, geol­ ogy, meteorology, bot an y and other closely related subjects as they applied to Axel Heiberg Island. An undertaking of this nature does not set a precedent in the broad field of Arctic studies: there is a rather extensive history of high latitude studies to r r to. It is felt, however, that this expedition differs from many other s in that the re was a conscious effort t o integrate and cor relate the various field sciences in or der to effect more efficient field operations and achieve a more comprehensive and unified result. The use of seismic methods to investigate glaciers is a fairly well established field technique. Seismic investigations have been carried out on almost every large body of ice in the world; there is no claim to originality in either application or method of seismic sounding. The purpose of the seismic work was to establish ice depths to be used in the study of the glaciological regime of Axel Heiberg, as well as to provide control for the gravity survey which was carried out concurrently. 3 GEOLOGYandGEOGRAPHY of AXEL HEIBERG ISLAND and EXPEDITION AREA Axel Heiberg Island is a remote and fairly inaccessible region of the Canadian arctic. The island forms a single geographical unit with Ellesmere Island, from which it is separated only by the narrow waters of Eureka Sound. Its area is sorne 15, 000 square miles, about the size of Swit­ zerland; it is the fourth large st of the Que en Elizabeth Islands. Axel Heiberg was discovered in 1899 by a sledging party of Sverdrup 1 s 1898 - 1902 expedition. Fig. 1 shows the location of Axel rg Island and the primary transport routes. The island can be roughly divided into three topographie regions: a central mountain region, large1y covered by ice; a smooth1y sloping area in the east; and a generally hilly region in the west. (Dunbar, 1956). Aerial views of portions of the central region are shown in Fig. 2. A brief comment on the geology of the expedition area is quoted from Kranck, 1961: "The central parts of the island around Strand Fiord and Expedition Fiord consist of highly folded Jurassic and Cretaceous sediments intersected by basic igneous rocks forming flows and sills. The olde st sediments visible are quartzitic sandstones with a few plant fossils (Jurassic}. On top of this very thick horizon follows soft carbon rich 4. Map 1 LOCATION OF HEIBERG ISLAND, N.W.T. WITH TRANSPORT ROUTES . Air Routes lee Breoker Route l' '\ 1 ' ' ' ' ' ··-....... .. ' \ ~ ··- ··-··...j-----r-·····~--- ' _--=:..... -r··- \ i ~ ' 1 CHURCHILL . ..1 1 i '!:~........... \. ... 'f\\.:. 1 ·.......... .) 1 1 1 ~ -·-·- WINNIPEG __._b:::---+----- ·-. ...r._ ·-·-·- Fig. 1. 5 Pig. 2a Fig. 2b. Fig. 2. Topography of Central Region of Axel Heiberg Island 1. 6 black shales and thereafter a few hundred metres of mixed strata of shales and sandstone. These strata are comformably overlaid by volcanic lava ( Cretaceous ), with beds of columnar ba salt alternating with highly vesicular and tuffitic material. They form a very striking horizon in the landscape as erosion has usually reached clown to the level of the main basalt, which, therefore, often forms the crest of the mountains. Particularly in synclines younger sediments are found on top of the lava. The other main factor controlling the topography is gypsum which occurs in enormous quantities, mainly in the centre of each anticline. In the central parts of the island it is everwhere in allochthonous position, intruded in the sediments as diapirs. The original age is probably Pennsylvanian. 11 The two glaciers which were surveyed by geophysical methods are described by MÜller as follows: "The White Glacier is a medium size ice stream with a well defined accumulation basin ..... this north-south running, alpine type, valley glacier measure s 14. 5 km. in length, having a width of 5 km. in the accumulation basin and averaging l km. in width in the ablation zone ..... the surface of the White Glacier drops in three gentle steps in the accumulation are a and in four steps, which have almost the char­ acter of ice falls, in the ablation zone. The gradient for the whole glacier ave rages 10 per cent. n 7 ''The Thompson Glacier is one of the largest outlet glaciers from the 7250 square kilometres of highland ice, the northern or 1 McGill lee 1 Cap • The glacier measures 35 km. in length from the ice divide, ~!< >:;:: which is at an elevation of approximately 1600 m. , to its terminus The gradient averages about 4 per cent. for the whole glacier, but only about one per cent. for its lower half. The width varies between 3 and 5 km. 11 (Müller, 1961 ). The expedition area is shown in Fig. 3; a more detailed map of the southern portion of the expedition area is shown in Fig. 4. >:~The name 11 McGill lee Cap" has been changed to 11 Akaioa lee Cap. 11 *~:<This elevation has since been corrected to approximately 1450 m. 8 ARC71C .,.,. OCEAN ~ Camp of 80 /P.olar Continenta \~) /Shelf Project MEIGH~N ~fd· {ISLANDv ISACHSEN -10 miles lee covered Expedition Areo ( aeneo lltrlcto ) ~ Greater Expedition Areas Permanent ond • Semi • permanent Stations Grovity Meosurements • Outside Expedition Areo Camps Outside Expedition Area * + Gloclology • Geology 78°N l:t. Geomorphology 0 Botany Fig. 3. - e N ~ t ;) ~gitudlnol Beover ?r ~ .. · ~··1 ...0 + Tonou• Check Pointa d Tongue Levelllno Profile tee Fr" LoneS Accumutotton a Flood PhJin Ab1etlcm Stall:ee water wtttl loe Floes tnnrted 11168 Morolnlo Moter,at o in..,.te4 1aeo seieMic a oravlt~ •+ atotlona IIUIO compa • • arovlt~ etottona uaeo saae Cami) oQhte prof1le 1980 Form hnea in m&tres ( oppr-oaJ ---~2"-- 4 !5 kM. Baud on tormlm• mqp • N R C.• ottawa 1aeo SOUTHERN PART OF EXPEDITION AREA AXEL HEIBERG ISLAND • N.W.T. Fig. 4. 10 REFRACTION METHODS Three refraction lines were shot during the course of the field work; one at Beaver Profile (730 m. long) in the accumulation zone of White Glacier; one at Moraine Profile (710 m. long) near the equilibrium zone of White Glacier; and one at Upper lee Profile (1925 m. long) on the Akaioa lee Cap. The primary purpose of these surveys was to determine longitudinal wave velocities, although the refraction line on the ice cap was also in­ tended to provide a positive value of the depth of rock, since reflections in this area were either not obtained or were somewhat indefinite. A detailed description of the seismograph and the function of its various components will be found in Appendix A; Fig. 11 shows the instruments mounted on a small tobboggan. Comments on transportation of personnel and equipment in the field will be found in Appendix B. The seismograph was operated without filtering or AGC for all of the re­ fraction work. The blaster unit was connected to the camera by means of wire wound on a commutated reel. As a result of experience with this method, radio communication, including transmission of the shot break, is recommended for this type of operation since it permits a much greater degree of freedom in movement, and allows long, detailed reversed re­ fraction lines to be run without being hampered by long lengths of 1phone wire.. ll A geophone spacing of 15 meters was employed on all refraction lines, this spacing being the largest that could be obtained with the seismic cable used. A larger spacing would have been an advantage on the ice cap. Charge sizes ranged from approximately 500 gms. to 15 kg, depend­ ing on the shot distance. The seismic stations were surveyed with a Wild TO theodolite, a light weight and rugged instrument well suited for this type of work. Distances were measured by stadia. The initial portions of each of the three travel-time curves are shown in Fig. 5. The similarity between the curves for Beaver and Moraine Profiles was not expected; surface conditions were quite different in the two zones; Beaver Profile is four km.