Bathymetry of

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76 32'W 76 30'W 76 28'W 76 26.4' 44 4.2' 44 04'N 4 ATMOSP 44 04'N ND HE T OF C Small Rounded Basin at Charity Shoal A RI N O IC C E M N A M M A D T 0 E M R E C I N A R O I S P C 10 L T A E E R

N A D A small equidimensional circular depression 1000 meters in

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U I C e 20 T I . E S C E R 44 30'N . feature referred to as Charity Shoal on nautical charts. An D R D E 44 30'N E E 10 P M CIRES S M p A M RT O T A MENT OF C ATES O F elongated extends southwest from the feature, resembling the tail of a crag-and-tail feature common to some fields. t 15 National Geophysical Data Center Nautical Charting Division Cooperative Institute for Research in Environmental Sciences U.S. Department of Commerce The basin is slightly deeper than 18 meters and the rim rises to h National Environmental Satellite, Data, and Information Service Canadian Hydrographic Service University of Colorado National Oceanic and Atmospheric Administration depths of 2-6 meters. The origin of the feature remains unknown. 20 2 10 Boulder, Colorado Department of Fisheries and Oceans Boulder, Colorado Although a sinkhole in the terrane is a possibility, an i 18 , Ontario, origin related to a meteor crater, that was subsequently glaciated, 4 n 25 Great Environmental Research Laboratory seems more likely. Aeromagnetic mapping by the Geological 44 02'N 40 44 02'N Office of Oceanic and Atmospheric Research Survey of Canada revealed a negative magnetic anomaly over 30 6 Ann Arbor, Charity Shoal, which is a characteristic feature of simple impact M 20 craters (Pilkington and Grieve, 1992). e 35 W.T. Virden, CIRES, University of Colorado, Boulder, CO 80303 t km r e 40 J. S. Warren, Canadian Hydrographic Service, Ottawa, ONT., K1AOE6 Rive 0 5 t r 30 n 45 44 0.498' T.L. Holcombe, NOAA/National Geophysical Data Center, Boulder, CO 80303 re Scale 1:65,000 s World Data Center for Marine Geology and Geophysics, Boulder, CO, Report MGG-15 T 76 31.998' 1999 Transverse Mercator 50 D.F. Reid, 50 Published by the National Geophysical Data Center NOAA/ Environmental Research Laboratory, Ann Arbor, MI, 48105 Projection http://www.ngdc.noaa.gov/mgg/greatlakes/greatlakes.html 44 00'N 44 00'N T.L. Berggren, Geological Society of America, Boulder, CO 80303 76 32'W 76 30'W 76 28'W This map is intended to depict lake floor topography, and is not to be used for navigation. Lake floor feature names have been approved by the U.S. Board on Geographic Names. e k Kingston NGDC wishes to thank the following individuals for reviewing this poster: a r L ive Depth in Meters Bruce Sanford, Geological Survey of Canada (retired), Nepean, ONT. K2G5J4 R e Scotch Bonnet and Point Petre ce Mike Lewis, Geological Survey of Canada (Atlantic), Dartmouth, N.S. B2Y4A2 ic te en n 20 . r i I

Seismic sections show that the Scotch Bonnet and Point Petre Ridges u e o Wolfe w 0 12 24 36 48 60 72 84 96 108 120 132 144 156 168 180 192 204 216 228 240 252 John Coakley, Canadian Centre for Inland Waters, Burlington, ONT. L7R4A6 R Q c a f m are underlain by bedrock highs; at one location the Scotch Bonnet Ridge is d i L o n S Island . sla t bounded on the northwest by a 25 meters (Anderson and Lewis, ay t I S km B rs Recommended citation: 1975; Forsyth, et al., 1994). Valleys also interpreted as bedrock features extend he 0 30 m Scale 1:275,000 Virden, W.T.,  J.S. Warren, T.L. Holcombe, D.F. Reid, and T.L. Berggren, 1999, Bathymetry NE-SW, paralleling the two main ridges and lying between and adjacent to these A Transverse Mercator Projection of , National Geophysical Data Center, World Data Center for Marine Geology ridges (Hutchinson, et al., 1993). These features are lineated in the same direction as Trenton 30 2 meter contour intervals and Geophysics, Boulder, CO, Report MGG-15, scale 1:275,000 poster. faults and bedrock lineations occurring to the northeast in Ontario in the distinct NE-SW fabric of the Grenville basement rocks (Forsyth, et al, 1994). The Scotch Bonnet Ridge lies on the northward extension of the Clarendon-Lynden Fault system in 40 l e (Hutchinson, et al., 1979). A channel (Scotch Bonnet Gap) which breaches the West and East Kingston, Galloo, and Stony Basins 10 n Charity n Scotch Bonnet Ridge connects the and Genesee Basins near l Shoal ana a y C Lake Margin Topography rra h the deep axis of the lake. Deep connections also occur between the Mu Several small shallow basins with intervening ridges occur West C l Niagara and Mississauga Basins and the Genesee and in the northeastern extremity of Lake Ontario, all having e Around the perimeter of the lakefloor, the high energy of water circulation has evidently prevented the deposition of postglacial Rochester Basins (Genesee Gap). 30 Kingston d n depths of generally less than 40 meters. The bathymetry n 44 00'N n 20 10 44 00'N Basin a 30 muds, except in sheltered areas (Thomas et al., 1972). Strongly linear bathymetric features displaying the imprint of exhibits a preferred orientation of NE-SW, and appears to be largely a l a s h glaciation, or of exhumation of bedrock topography and structure, occur at intervals along almost all of the water-covered extension of the topography occurring northeast of the lake. I C Galloo lakeshore. Study of bottom sediment types off the western lakeshore between Niagara and The basins were probably produced by glaciation followed by some East e e revealed that extensive areas of exposed bedrock, boulder pavement, sand deposits, and glacial sedimentary infilling and topographic smoothing. Bedrock, consisting of o c Basin Kingston c n 10 drift occur here (Rukavina, 1969; Rukavina, 1976). Apparently in most areas around the lake Port Hope Ordovician and e Basin m n 20 t i r i l perimeter, Quaternary sediments are relatively thin or absent, and bedrock exposures are shales, lies at or near the oin s e 30 d P S M w a ar B n w ai common, possibly reflecting the effects of subglacial erosion and subsequent abrasion 30 surface beneath the ridges Ed n a n ce Duck I. . y a Prin L I n h by lacustrine waves and currents. 40 and shoals separating the o o I. t llo t y C 50 n a S n r 10 basins. (Sly and Prior, 1984). i G to e Scotch Bonnet Island a S v S i int R Po e Whitby Oshawa n tr Duc k Ledges and Channels in the Mississauga Basin 60 o e k-G c lm P a Stony Sa t llo a in o l Point o R B P id In the deep axis of the Mississauga Basin from 146-182 meters depth, there are several ledges of a few meters relief, ge ork separated by scarplets that trend north to south. These features step down from west to east toward the deepest 20 Y 20 point in the basin. Although the origin of the ledges is not known, they might have formed on the eroded edges 70 Ontariow of a succession of gently dipping strata which are characterized by bed-to-bed variation in resistance to erosion. 40 Ne 40 Rudimentary valleys and channels of only a few meters relief are superimposed on the ledges 80

and appear to represent a drainage pattern. Formation of the ledges could have been 60 90 e 30 20 40 10 the result of the erosional action of Wisconsin glaciation and/or subglacial meltwater , 100 g 60 acting against the differential resistance to erosion and layered aspect of the 110 d 50 80 i 60 sedimentary strata (probably Trenton Limestone; Sanford and Baer, 1981) 120 e 80 70 underlying the lake floor. R g 80 130 d t i 100 90 140 e R 100 110 n e 100 r t 130 120 150 n e 140 160 o 150 B 120 P 120 Ontario t 160 170 New York in h 180 170 c 140 o t P 180 o 190 140 c Mississauga S 160 200 160 Mississauga 190 Genesee Niagara Whitby-Olcott Basin e 180 Genese Gap Rochester Ridge Scotch Bonnet Basin 170 43 30'N Basin140 43 30'N 170 Gap Duck-Galloo Ridge, Channel, 160 Basin Channel, and Black River Channel 150 210

140 At the southern rim of the East Kingston, Galloo, and Stony Basins Oswego 130 130 120 there occurs a series of broad low ridges which individually trend 100 110 90 NE-SW, but which coalesce to form a complex ridge extending 1 80 20 from the west near Prince Edward Point, Ontario to the east near 120 70 110 60 Stony Point, New York. This feature has a relief ranging from 20-30 50 160 40 120 meters and is asymmetrical, with steep northeast facing scarps, 140 100 30 and gently sloping surfaces facing southwest toward the main basin 10 20 0 10 100 of Lake Ontario. The cuesta features seen here are gently rounded 90 80 80 80 to flat on top, and several are capped by islands, the principal of

7 which are Main Duck, Galloo, and Stony Islands. The Simcoe Island, 0 60 6 60 0 50 Basin Bathymetry of Lake Ontario Saint Lawrence, and Black River Channels are incised through the 40 Olcott 40 Duck-Galloo Ridge and extend NE-SW across the above mentioned 20 40 10 30 Fan New bathymetry has revealed the presence of a small basin between the Mississauga and Rochester Basins and we have given it basins. All three channels broaden out at the southern margin of the 20 ra 2 a 0 ag 2 Duck-Galloo Ridge. This was probably the location of the Lake Ni the new name, Genesee Basin. The four axial basins, separated by three ridges, occupying the floor of Lake Ontario are from west to east the Niagara, 0 Mississauga, Genesee, and Rochester Basins. North of the mouth and to the west, in the subtly defined Niagara Basin (which barely exhibits topographic Ontario shoreline in early postglacial time, and the three channels 1 were probably the main outflow channels for the lake at this time 0 closure), the deep axis of the lake is about midway between north and south shores. Farther east, the axial depths of the other three basins lie well toward the southern edge of Hamilton the lake, giving the lake a distinct asymmetry in its north-south profile. This asymmetry is related to the bedrock configuration underneath the lake floor, and its differential resistance to glacial Sodus (Anderson and Lewis, 1985). Niagara-on-the-Lake N Bay erosion (Hutchinson, et al., 1993). Gently southward dipping, erosion-susceptible shales and redbeds of the Middle and Upper Ordovician Utica Formation, Lorraine Group (Blue Mountain and r i a e v i l g Formations in Ontario), and , overlie southward-dipping erosion-resistant limestones of the Middle Ordovician Trenton Group (Cobourg and Lindsay Formations in Ontario).

a a R n Irondequoit a r e C a 77 05'W 76 55'W 76 50'W e 77 00'W

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e n v Preparation and Supporting Data of the New Bathymetry e W

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r G This poster is the third in a series of five depicting the bathymetry of the Great Lakes - the other two being (1996) and (1998). Preparation of Lake Erie and Lake Ontario bathymetry was a collaborative effort between scientists at the NOAA National Geophysical Data Center (NGDC), the NOAA Great Lakes Environmental Research Laboratory, the Canadian Rochester Hydrographic Service, the University of Colorado Cooperative Institute for Research in Environmental Sciences, and the University 43 35'N 43 35'N of Michigan Cooperative Institute for Limnology and Ecosystems Research. A CD-ROM containing Lake Ontario bathymetry, with formats compatible with various computing systems and geographic information systems, includes screen imagery and a summary of geomorphology. 170 190

The entire historic hydrographic sounding data base from the U.S. and Canada, originally collected for nautical charting purposes, Sculptured Parallel Ridges in the Rochester Basin 180 References and For Further Reading was used to create a complete and accurate representation of Lake Ontario bathymetry. The U.S. data primarily came from the NOS Hydrographic Survey Data, U.S. Coastal Waters CD-ROM Set (Version 4.0, Data Announcement 98-MGG-03) referred to Anderson, T. W., and C. F. M. Lewis, 1975, Acoustic Profiling and Sediment Coring in Lake Ontario, Lake Erie, and Georgian Bay, in Geological Survey of Canada Report of Activities: part A, paper 75-1, p. 373-376. as the NOS -digital- data in the map below. This and other bathymetric sounding data collected by the U.S. National Ocean A series of distinct NE-SW ridges occupy the floor of Lake Ontario's deepest basin, Service's (NOS) Coast Survey and the U. S. Army Corps of Engineers was employed to construct bathymetric contours at 1 the Rochester Basin. These ridges, having a relief of 15-25 meters and a natural Anderson, T.W., and C. F. M. Lewis, 1985, Postglacial Water Level History of the Lake Ontario Basin, in Karrow, P. F. and P. E. Calkin (eds.), QUATERNARY EVOLUTION OF THE GREAT LAKES, Geological Association of Canada Special Paper 200 30, p. 231-253. meter intervals from 1-10 meters depth and 2 meter intervals at depths greater than 10 meters. Compilation scales ranged from spacing of 250-1000 meters, are remarkable in their linear aspect and uniform width. 1:10,000 to 1:50,000. Bathymetric sounding data collected by the Canadian Hydrographic Service (CHS) were employed to Bloom, A. L., 1991, GEOMORPHOLOGY: A SYSTEMATIC ANALYSIS OF LATE CENOZOIC LANDFORMS, Englewood Cliffs NJ, Prentice Hall, 532p. Most have relatively flat tops with steep side slopes, some of which are steeper to 100 construct bathymetric contours at 1 meter intervals and compilation scales ranging from 1:1,000 to 1:30,000. Digitization of the D 43 00'N the northwest, others to the southeast, and some are symmetrical in cross-profile. 43 00'N Chapman, L. J., and D. F. Putnam, 1951, THE PHYSIOGRAPHY OF , Press, 284p., maps. bathymetric contours, merging of the bathymetric contour data sets, poster construction, and 110

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U Seismic and sediment core data suggest that many of the ridges coincide with the

O preparation of a CD-ROM, were accomplished at the NGDC. Multibeam bathymetric data

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Clark, J. A., M. Hendriks, T. J. Timmermans, C. Struck, and K. J. Hilverda, 1994, Glacial Isostatic Deformation of the Great Lakes , GEOLOGICAL SOCIETY OF AMERICA BULLETIN, v. 106, p. 19-31. G G

O University of New Brunswick's Ocean Mapping Group (UNB-OMG)

I L collected by the , with C underlying relief of glacial landforms beneath the lake sediment (Hutchinson, et al.,

O A p L É G Geological Survey of Canada (GSC) S support of the and the CHS, were kindly made available 130 U N Delorme, L. D., R. L. Thomas, and P. F. Karrow, 1990, Quaternary Geology, Waterloo/ Burlington and Lake Ontario, in McKenzie, D. I. (ed.), QUATERNARY ENVIRONS OF LAKES ERIE AND ONTARIO, A FIELD GUIDE PREPARED FOR THE R O 1993). Resemblance exists between these features and grooved topography occurring I V S E Y IS FIRST JOINT MEETING OF THE CANADIAN QUATERNARY ASSOCIATION AND THE AMERICAN QUATERNARY ASSOCIATION, WATERLOO, ONTARIO, CANADA, p. 142-162. - C O M M in gridded form. In the two areas where multibeam bathymetric data were available, no other t in onshore drumlin fields north of the lake, as noted by Lewis (1997). Some of the 140 bathymetric data were used in the compilations. In some areas all available Canadian and U. S. Forsyth, D. A., B. Milkereit, C. A. Zelt, D. J. White, R. M. Easton, and D. R. Hutchinson, 1994, Deep Structure Beneath Lake Ontario: Crustal Scale Grenville Subdivisions, CANADIAN JOURNAL OF EARTH SCIENCES, v.31, p. 255-270. Rochester Basin ridges are also abruptly truncated on their rounded northeastern bathymetric sounding data, collected at different times on different survey expeditions, were used to derive the contours. h 150 ends, opposing the direction of ice advance, a distinct feature observed in drumlin Hutchinson, D. R., P. W. Pomeroy, R. J. Wold, and H. C. Halls, 1979, A Geophysical Investigation Concerning the Continuation of the Clarendon-Linden Fault Across Lake Ontario, GEOLOGY, v. 7, p. 206-210. The U.S. coastline used was primarily the GLERL Medium Resolution Vector Shoreline dataset (Lee, 1998). Where needed for fields. An alternate interpretation has been proposed for the ridges, namely, that the 160 Hutchinson, D. R., C. F. M. Lewis, and G. E. Hund, 1993, Regional Stratigraphic Framework of Surficial Sediments and Bedrock Beneath Lake Ontario, GEOGRAPHIE PHYSIQUE ET QUATERNAIRE, v. 47, no. 3, p. 337-352. more coverage, the NOS Medium Resolution Vector Shoreline for the Conterminous U.S. (1994) dataset was used. Coastlines side slopes of the ridges have resulted from faulting (Thomas, et al., 1993). The 210 i 170 from the CHS bathymetric sounding data field sheets were used to complete the Canadian coastline. Kemp, A. L. W., T. W. Anderson, R. L. Thomas, and A. Mudrochova, 1974, Sedimentation Rates and Recent Sedimentary History of Lakes Ontario, Erie, and Huron, JOURNAL OF SEDIMENTARY PETROLOGY, v. 44, no. 1, p. 207-218. parallel ridges of the Rochester Basin trace an arc from NE-SW to nearly east-west, n 180 Kemp, A. L. W., and N. S. Harper, 1976, Sedimentation Rates and a Sediment Budget for Lake Ontario, JOURNAL OF GREAT LAKES RESEARCH, v. 2, no. 2, p. 324-340. As seen in the diagram below, the density of data varies greatly from one region to another. The areas with 650 meters track which suggests they were formed by subglacial flow following the changing trend of spacing or more contain low data density, and areas with track spacing of 300 meters or less contain high data density. The the southern side of the basin, as if flow was deflected westward by the massive bulk 190 Lee, D. H., C. Morse, and D. Bandhu, 1998, Great Lakes and St. Lawrence River Medium Resolution Vector Shoreline Data, NOAA Technical Memorandum NOAA ERL GLERL-104. 230 multibeam bathymetric data are of very high data density, and the NOS nautical chart data have very low data density. More of the Allegheny Plateau to the south. The relative roles of ice and meltwater floods 200 220 244 M Lewis, C. F. M., and P. G. Sly, 1971, Seismic Profiling and Geology of the Area of Lake Ontario, PROCEEDINGS OF THE 14TH CONFERENCE ON GREAT LAKES RESEARCH, International Association of Great Lakes data in the present low data density areas would not only better verify existing contours but also show more details of bottom in forming these ridges is a topic of continuing research. 220 210 Research, p. 303-354. topography (as illustrated on the main map if high data density and low data density areas are compared). 43 30'N 43 30'N e Lewis, C. F. M., L. A. Mayer, G. D. Cameron, and B. J. Todd, 1997, in Lake Ontario, in T. Davies, et al., (eds.), GLACIATED CONTINENTAL MARGINS: AN ATLAS OF ACOUSTIC IMAGES, Chapman and Hall, London, p. 48-49. t 220 DATA COVERAGE Martini, I. P., and J. R. Bowlby, 1991, Geology of the Lake Ontario Basin: A Review and Outlook, CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES, v. 48, p. 1503-1516. e 230 Muller, E. H., and D. L. Pair, 1992, Comment and Reply on: "Evidence for Large-Scale Subglacial Meltwater Events in Southern Ontario and Northern New York State," GEOLOGY, v. 20, p. 90-91. 240 80 00'W 00'W 79 30'W 79 00'W 78 30'W 78 00'W 77 30'W 77 00'W 76 30'W 76 77 1.002' r Pilkington, M., and R. A. F. Grieve, 1992, The Geophysical Signature of Terrestrial Impact Craters, REVIEWS OF GEOPHYSICS, v. 30, no. 2, p. 161-181. 210 250 CHS data with track spacing in meters NOS data with track spacing in meters 43 34.998' s Rukavina, N. A., 1969, Nearshore Sediment Survey of Western Lake Ontario, Methods and Preliminary Results, PROCEEDINGS OF THE 12TH CONFERENCE ON GREAT LAKES RESEARCH, International Association of Great Lakes (depth dependance) (depth dependance) Research, p. 317-324. 1000 3500 -digital- 60-300 -digital- 4 Rukavina, N. A., 1976, Nearshore Sediments of Lakes Ontario and Erie, GEOSCIENCE CANADA, v. 3, no. 3, p.185-190. 4 00'N 125 (< 30m depth) 150 (< 10m depth) 44 00'N km 200 and 250 (> 30m depth) 650 (> 10m depth) Sanford, B. V., and A. J. Baer, 1981, Geological Map of Southern Ontario, GEOLOGICAL ATLAS 1:1,000,000 (R. J. W. Douglas, coordinator), Geological Survey of Canada, map 1335A, sheet 30S. 125 (< 20m depth) 0 4 200 (> 20m depth) Shaw, J., and R. Gilbert, 1990, Evidence for Large-Scale Subglacial Meltwater Flood Events in Southern Ontario and Northern New York State, GEOLOGY, v. 18, p.1169-1172. 5-90 200 150 (small areas) Sly, P. G., and J. W. Prior, 1984, Late Glacial and Postglacial Geology in the Lake Ontario Basin, CANADIAN JOURNAL OF EARTH SCIENCES, v. 21, p. 802-821. Scale 1:75,000 100 190 Sly, P. G., 1984, Sedimentology and Geochemistry of Modern Sediments in the Kingston Basin of Lake Ontario, JOURNAL OF GREAT LAKES RESEARCH, v. 10, no. 4, p. 358-374. Transverse Mercator 43 30'N 5-90 43 30'N Teller, J. T., 1987, Proglacial Lakes and the Southern Margin of the , in W. F. Ruddiman and H. E. Wright Jr., eds., AND ADJACENT OCEANS DURING THE LAST DEGLACIATION, Decade of North Projection 170 American Geology, Geological Society of America, v. K-3, p. 39-70. NOS and CHS data, track spacing 100-150 meters Thomas, R. L., A. L. W. Kemp, and C. F. M. Lewis, 1972, Distribution, Composition, and Characteristics of the Surficial Sediments of Lake Ontario, JOURNAL OF SEDIMENTARY PETROLOGY, v. 42, p. 66-84. km 43 30' Thomas, R. L., J. L. Wallach, R. K. McMillan, J. R. Bowlby, S. K. Frape, D. L. Keyes, and A. A. Mohjaer, 1993, Recent Deformation in the Bottom Sediments of Western and Southeastern Lake Ontario and its Association with Major Structures 15, 45, and 90 meter grids, derived from NOS nautical and Seismicity, GEOGRAPHIE PHYSIQUE ET QUATERNAIRE, v. 47, p. 325-335. 0 50 UNB-OMG, GSC, and CHS multibeam bathymetry 180 chart data 76 54'

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