Canadian Journal of Earth Sciences Geomorphic diversity and complexity of the inner shelf, Canadian Arctic Archipelago, based on LiDAR and multibeam sonar surveys. Journal: Canadian Journal of Earth Sciences Manuscript ID cjes-2018-0312.R1 Manuscript Type: Article Date Submitted by the 12-Feb-2019 Author: Complete List of Authors: Shaw, John ; Natural Resources Canada Potter, D. Patrick; Natural Resources Canada, Geological Survey of Canada (Atlantic) Wu, Yongsheng;Draft Fisheries and Oceans Canada, Bedford Institute of Oceanography Keyword: Canadian Arctic Archipelago, LiDAR, Multibeam sonar, Littoral zone Is the invited manuscript for consideration in a Special Not applicable (regular submission) Issue? : https://mc06.manuscriptcentral.com/cjes-pubs Page 1 of 42 Canadian Journal of Earth Sciences 1 Geomorphic diversity and complexity of the inner shelf, Canadian Arctic 2 Archipelago, based on LiDAR and multibeam sonar surveys. 3 4 John Shaw1, D. Patrick Potter2, and Yongsheng Wu3 5 6 1Geological Survey of Canada (Atlantic), Bedford Institute of Oceanography, 1 7 Challenger Drive, Dartmouth, Nova Scotia, B2Y 4A2, Canada. E-mail: 8 [email protected] 9 2Geological Survey of Canada (Atlantic), Bedford Institute of Oceanography, 1 10 Challenger Drive, Dartmouth, Nova Scotia, B2Y 4A2, Canada. E-mail: 11 [email protected] Draft 12 3Ocean and Ecosystem Sciences Division, Fisheries and Oceans Canada, Bedford 13 Institute of Oceanography, Dartmouth, Nova Scotia, B2Y 4A2, Canada. E-mail: 14 [email protected] 15 Corresponding author: Dr. John Shaw, Geological Survey of Canada (Atlantic), Bedford 16 Institute of Oceanography, 1 Challenger Drive, Dartmouth, Nova Scotia, B2Y 4A2, 17 Canada. Tel: 902 426 6204. E-mail: [email protected] 18 19 1 https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 2 of 42 21 22 Abstract: Data from two surveys by multibeam sonar and two by marine/terrestrial 23 LiDAR are used to evaluate the geomorphology of the seafloor in littoral areas of the 24 Canadian Arctic Channels, near King William Island, Nunavut. Submarine terrains show 25 well-preserved glacial landforms (drumlins, mega-scale glacial lineations, iceberg- 26 turbated terrain, recessional moraines, and glaciofluvial landforms) with only slight 27 modification by modern processes (wave action and sea-ice activity). At Gjoa Haven the 28 seafloor is imprinted by fields of pits 2 m-wide and 0.15 m-deep. They may result from 29 gas hydrate dissolution triggered by falling relative sea levels. The Arctic Archipelago 30 displays what might be termed “inverted terrains”: marine terrains, chiefly beach ridge 31 complexes, exist above modern seaDraft level and well-preserved glacial terrains are present 32 below modern sea level. This is the inverse of the submerging regimes of Atlantic 33 Canada, where glacial terrains exist on land, but below sea level they have been effaced 34 and modified by marine processes down to the lowstand depth. 35 36 Key words: Canadian Arctic Archipelago, LiDAR, multibeam sonar, littoral zone. 2 https://mc06.manuscriptcentral.com/cjes-pubs Page 3 of 42 Canadian Journal of Earth Sciences 38 39 40 41 Introduction 42 43 Since 2003 the Ocean Mapping Group, University of New Brunswick, has been 44 collecting depth, backscatter, and sub-bottom data from the Canadian Arctic Archipelago 45 using the CCGS Amundsen. These data have been highly valuable in providing 46 information on the marine geology of the Arctic seafloor (e.g., see Bennett et al. 2016; 47 MacLean et al. 2010, 2016a,b). However, since the passage of the survey vessel has been 48 mainly through the middle of poorly-chartedDraft channels, analyses of the data arguably 49 provide a non-representative view of the Arctic seafloor. The channels have been the 50 conduits for major ice streams (Clark and Stokes, 2001; Margold et al., 2015) and thus 51 the multibeam imagery tends to show deep-water glacial lineations created by fast- 52 flowing grounded ice (MacLean et al., 2010), or ice-stream convergence zones 53 (Dowdeswell et al., 2016). 54 In this paper we offer a differing (and complementary) view of the Arctic Channels 55 seafloor, based primarily on analysis of multibeam sonar and marine/terrestrial LiDAR 56 data collected by the Canadian Hydrographic Service (CHS) in four coastal areas. We 57 have no ground-truthing information (cores, bottom photographs, grab samples) and 58 unlike the CCGS Amundsen surveys, 3.5 kHz sub-bottom profile data are not available. 59 Nevertheless these new data provide intriguing and sometimes enigmatic glimpses of the 3 https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 4 of 42 60 seafloor in the littoral portions of the channels that dissect the Canadian Arctic 61 Archipelago. 62 63 Using four data sets, our goals are to: 64 65 Demonstrate the complexity of the seafloor at the four sites, and also explore the 66 differences between them. 67 Report on the glacial landforms that dominate the submarine landscapes, and link 68 them with known processes (e.g., ice streaming events). 69 Describe enigmatic seafloor features at one of the study areas (Gjoa Haven). 70 Demonstrate that the dominantDraft submarine morphology in this emergent region is 71 glacial in origin, in contrast with the submerging littoral zones of Atlantic 72 Canada, where glacial landforms have been effaced during the postglacial 73 transgression. 74 75 Geological setting 76 77 The study consists of the southwestern part of the Canadian Arctic Channels (Fig. 1), 78 in the vicinity of King William Island and the Boothia Peninsula. King William Island is 79 composed entirely of Late Cambrian to Ludlow Arctic Platform rocks: dolostone, 80 dolomitic limestone, limestone, etc. (Harrison et al., 2015). The study sites fall within the 81 area glaciated by the Laurentide Ice Sheet (Dyke and Prest, 1987; Dyke et al., 2002). The 82 most recent authors describe the glacial history from a terrestrial perspective, with an 4 https://mc06.manuscriptcentral.com/cjes-pubs Page 5 of 42 Canadian Journal of Earth Sciences 83 emphasis on the role of ice streaming (Clark and Stokes, 2001; De Angelis, H. 2007; 84 Margold et al., 2015, 2018; Tremblay, 2017). The M’Clintock Ice Stream is a dominant 85 feature in reconstructions, and while it is strongest north of the study area, Queen Maud 86 Gulf and northern King William Island fall within its catchment. Eastern King William 87 Island is likely within the catchment of an ice stream that drained northeast into the Gulf 88 of Boothia (see Fig. 3, Margold et al., 2015). These ice-stream events represent single 89 phases in the life of the ice sheet, and terrestrial evidence shows evidence of many flow 90 directions (De Angelis and Kleman, 2005; Dyke et al., 1991; Tremblay, 2017). 91 As a result of glacial isostasy, the lateness of deglaciation, as well as tectonism on the 92 Boothia Peninsula, relative sea-level histories in the region are dominated by emergence. 93 King William Island was deglaciatedDraft about 8.8 to 8.6 14C yrs ka (~9.6–9.9 cal yrs BP) 94 (Dyke and Prest, 1987) and the entire island is below marine limit. Dyke et al. (1991) 95 stated that relative sea level was higher than the highest land at 120 m, and data from the 96 adjacent mainland suggests it was probably at 180 m. More recent work on King 97 William Island (Dyke and Savelle, 2009) shows that relative sea level was +55 m at 6 ka, 98 and fell rapidly, reaching +20 m at 3.5 ka and +5 m at 1 ka. The chief geomorphic 99 effect of this sea-level regime was the creation of raised beaches that yield information 100 not only on relative sea-level history (Dyke et al., 1991) but also archaeology (Dyke and 101 Savelle, 2009). 102 Data from multibeam sonar surveys in the Arctic Channels, available online 103 (University of New Brunswick, 2019), provide some information on the nature of the sea 104 floor. Within the study region data have been collected in multiple years along two 105 routes, Franklin Strait and M’Clintock Channel, that converge in Victoria Strait. Thus, 5 https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 6 of 42 106 MacLean et al. (2016c) show mega-scale glacial lineations (MSGL) on the floor of 107 Franklin Strait, between Prince of Wales Island and the Boothia Peninsula. This was an 108 area in which the merged routes provide extensive coverage. Surveys closer to the study 109 area (in Victoria Strait) are narrow strips that are difficult to decipher—they show an 110 irregular sea floor with variable sediment thickness, possible iceberg furrows and 111 possible streamlined glacial landforms. 112 Most of the area is ice free from 20th August until 8th October (Canadian Ice Service, 113 2019). Oceanographic modeling (Chen et al., 2003) shows that maximum bottom tidal 114 currents (Fig. 1b) are relatively low (0.05 m sec-1) throughout the region, but much higher 115 at straits. Thus maximum bottom currents at Alexandra Strait (site 3, Fig. 1) attain 0.4 m 116 sec-1. Significant wave heights (Fig.Draft 1c) show a different spatial distribution from 117 currents. Wave height is low in Victoria Strait, but at Hat Island (site 1, Fig. 1), in the 118 large fetch area of Queen Maud Gulf, the maximum wave height reaches 3–4m. At James 119 Ross Strait (site 2) and Gjoa Haven (site 3) wave heights are < 1 m, likely due to short 120 fetches which constrain wave development. 121 122 Methods 123 Four data sets were collected during surveys commissioned by the Canadian 124 Hydrographic Service, Central and Arctic Region. 125 126 1) Hat Island – marine/terrestrial LiDAR.