Abstract/Résume ................................................. 1
Summary/Sommaire ................................................ 2
Introduction ................................................... 10
Setting ..................................................... 10
Historical changes .......................................... 12
Waste-water disposal systems ................................ 13
Report layout ............................................... 14
Database ....................................................... 14
Geological surveys .......................................... 14
Sediment samples ............................................ 14
Subsurface samples .......................................... 15
General methodology ......................................... 16
High-resolution seismic-reflection systems ............... 16
Sidescan sonar ........................................... 17
Data analyses ............................................ 18
Multibeam bathymetry ........................................ 19
Previous research .............................................. 21
Physiography ................................................... 23
Physiographic setting ....................................... 23
Harbour geographic divisions ................................ 25
Bathymetry .................................................. 25
Multibeam bathymetry ..................................... 25
Bedford Basin ............................................ 25
Bedford Bay ........................................... 27
Inner harbour ............................................ 28
The Narrows ........................................... 28
Northern inner harbour ................................ 28
Southern inner harbour ................................ 29
Northwest Arm ......................................... 29
Eastern Passage ....................................... 30
Outer harbour ............................................ 30
Approaches to Halifax Harbour ............................ 30
Regional setting ............................................... 31
Onshore bedrock geology ..................................... 31
Offshore bedrock geology .................................... 33
Onshore surficial geology ................................... 34
Offshore surficial geology .................................. 37
Regional onshore terrain .................................... 38
Oceanography ................................................... 39
Relative sea-level history .................................. 40
Harbour circulation ......................................... 40
Current variability ......................................... 40
Tides ....................................................... 41
Currents and particle transport ............................. 41
Sediment history and oceanography ........................... 41
Bedrock geology ................................................ 43
Seismostratigraphy .......................................... 43
Bedrock distribution ........................................ 43
Borehole results ............................................ 47
Faulting .................................................... 47
Surficial geology .............................................. 52
Introduction ................................................ 52
Surficial formations ........................................ 53
Previous research on sediment distributions ................. 54
Scotian Shelf Drift ......................................... 56
Seismostratigraphy ....................................... 56
Lithology ................................................ 56
Distribution and thickness ............................... 57
Morphology ............................................... 58
Depositional processes ................................... 59
Lacustrine sediments ........................................ 62
Seismostratigraphy ....................................... 62
Lithology ................................................ 62
Depositional environment ................................. 62
Distribution ............................................. 65
Estuarine sediments ......................................... 65
Seismostratigraphy ....................................... 66
Lithology ................................................ 66
Depositional environment and discussion .................. 66
Sable Island Sand and Gravel ................................ 66
Seismostratigraphy ....................................... 66
Lithology ................................................ 70
Distribution ............................................. 72
Benthic biology .......................................... 78
Depositional processes ................................... 78
LaHave Clay ................................................. 83
Seismostratigraphy ....................................... 83
Lithology ................................................ 86
Benthic biology .......................................... 91
Distribution ............................................. 91
Thickness ................................................ 99
Gas charging ............................................ 100
Pockmarks ............................................... 103
Depositional history .................................... 104
Depositional style ...................................... 106
Sediment transport and erosion ................................ 107
Bed forms .................................................. 107
Noncohesive sediment bed forms .......................... 107
Sand ribbons ......................................... 107
Megaripples .......................................... 108
Ripples in gravel .................................... 108
Gravel circles ....................................... 110
Cohesive sediment bed forms ............................. 110
Sedimentary furrows .................................. 110
Furrow processes ..................................... 112
Moats: erosional and nondepositional ................. 114
Georges Island moat ............................... 114
Regional scoured depressions ............................ 117
'Bottle collector hole' .............................. 117
Anthropogenic scoured depressions ....................... 117
Sediment drifts ...................................... 117
Other sediment-transport indicators ..................... 118
Discussion .............................................. 118
Anthropogenic features ........................................ 119
Antisubmarine net marks .................................... 119
Obstacle-induced scours .................................... 119
Anchor marks ............................................... 119
Anchor pits, anchor-drag marks, and anchor-chain and
anchor-chain-link marks ................................. 124
Distribution of anchor marks ............................ 124
Anchor marks and sediment transport ..................... 125
Borrow pits ................................................ 125
Dredge spoils .............................................. 126
Shipwrecks ................................................. 128
Ship-related seabed impressions ............................ 131
Spud-can pits ........................................... 131
Oil-rig pontoon marks ................................... 131
Ship-hull grounding marks ............................... 134
Propeller scour marks ................................... 134
Dredged and blasted areas .................................. 134
The Narrows' bridges ....................................... 135
Unidentified debris ........................................ 137
Mottled seabed ............................................. 137
Ship moorings .............................................. 137
Trawl marks ................................................ 137
Cables ..................................................... 137
Water intakes and discharges ............................... 141
Sewage banks ............................................... 141
Airplanes .................................................. 141
Automobiles ................................................ 143
Cribwork ................................................... 143
Geochemistry .................................................. 143
Geology and geochemistry ................................... 143
Sediment geochemistry ...................................... 143
Geochemical synthesis ...................................... 143
Historical contamination record ............................ 146
Geochemical evidence for sediment transport ................ 146
Geological history ............................................ 146
Preglacial bedrock origin of the harbour ................... 146
Glacial history ............................................ 147
Glacial control on harbour morphology ...................... 148
Wisconsinan Glaciation ..................................... 151
Postglacial history ........................................ 153
Recent changes ............................................. 155
Applications .................................................. 156
Marine outfalls ............................................ 156
Waste-water facility operation and monitoring .............. 156
Cable routing and seabed hazards ........................... 156
Marine aggregates .......................................... 156
Archaeology ................................................ 156
Fishing .................................................... 156
Research ................................................... 157
Effects of Hurricane Juan ..................................... 157
Acknowledgments ............................................... 157
References .................................................... 158
Figures
1. Geographic divisions of Halifax Harbour ................... 11
2. Index of place names and features used in this report ..... 12
3. Index of figures in this report ........................... 13
4. Ships' tracks of data collected during the four major
cruises ................................................... 15
5. Locations of seabed samples and observations .............. 16
6. Sun-illuminated seabed morphology, Bedford Bay to
Chebucto Head, Halifax Harbour ................... (on CD-ROM)
7. Seismic-reflection systems used during the study .......... 18
8. Backscatter map of a section of the outer harbour ......... 19
9. Sun-illuminated seabed morphology, Halifax Harbour
and the adjacent inner Scotian Shelf ............. (on CD-ROM)
10. A multibeam-bathymetric image from Bedford Basin .......... 20
11. A multibeam-bathymetric image of Northwest Arm ............ 21
12. Sun-illuminated seabed slope, Bedford Bay to Chebucto
Head, Halifax Harbour ............................ (on CD-ROM)
13. Interpretation of seabed morphology, features, and
processes, inner Halifax Harbour ................. (on CD-ROM)
14. Physiographic provinces of Atlantic Canada ................ 23
15. A shaded-relief topographic map of the area of Halifax
Regional Municipality ..................................... 24
16. Contoured bathymetry of Halifax Harbour ................... 26
17. Multibeam-bathymetric map of outer Halifax Harbour ........ 27
18. Interpretation of seabed morphology, features, and
processes, Bedford Basin, Halifax Harbour ........ (on CD-ROM)
19. A perspective shaded-relief colour multibeam image of
The Narrows ............................................... 28
20. Multibeam-bathymetric map of the harbour south of
Halifax ................................................... 29
21. Surficial geology, Bedford Bay to Chebucto Head, Halifax
Harbour .......................................... (on CD-ROM)
22. Interpretation of multibeam bathymetry at the approaches
to Halifax Harbour ........................................ 31
23. Major terranes of Nova Scotia and their dominant
bedrock types ............................................. 32
24. Map of major anticlines and synclines ..................... 32
25. A map of an early interpretation of faulting in
the harbour ............................................... 33
26. A shaded total-magnetic-field compilation ................. 34
27. A bedrock map of Halifax Harbour and the adjacent inner
Scotian Shelf ............................................. 35
28. Surficial geology and bathymetry of the Halifax Harbour
area ...................................................... 36
29. A map of the surficial geology of the inner
Scotian Shelf ............................................. 38
30. A shaded relief digital terrain model for an area of
central Nova Scotia ....................................... 39
31. A simplified cross-sectional model of water circulation
in Halifax Harbour ........................................ 40
32. Sidescan sonogram from the west side of The Narrows ....... 41
33. A sidescan sonogram of the seabed between Bedford Bay
and Bedford Basin ......................................... 44
34. Bottom photographs of bedrock ............................. 44
35. A sidescan sonogram from the inner harbour near
the Dartmouth shore over Halifax Formation slate .......... 45
36. A sidescan sonogram across granite bedrock outcrop ........ 45
37. Detailed multibeam-bathymetric image from The Narrows ..... 46
38. Sidescan sonogram from Northwest Arm ...................... 46
39. Borehole 3 log from The Narrows ........................... 48
40. Borehole 2 log in an area between Ives Point
and Halifax ............................................... 48
41. Borehole 4 log from the entrance to Eastern Passage ....... 49
42. Borehole 1 log from the entrance to Eastern Passage ....... 50
43. Borehole DF-1 log from a proposed diffuser location
in Halifax Harbour ........................................ 51
44. Borehole DF-2 log from a proposed diffuser location
in Halifax Harbour ........................................ 51
45. Borehole DF-8 log from a proposed diffuser location
in Halifax Harbour ........................................ 52
46. Seismic-reflection profile in an area of multiple till
sequences in the outer harbour ............................ 55
47. Interpreted cross-section and plan view from southwest
to northeast across The Narrows ........................... 56
48. A seismic-reflection profile extending from Pier 9 to
the Angus L. Macdonald Bridge ............................. 57
49. A seismic-reflection profile south of McNabs Island ....... 58
50. A seismic-reflection profile southeast of Chebucto Head ... 59
51. Seismic-reflection profile over Jonquiere Bank ............ 60
52. Seismic-reflection profiles, and interpretation from
the eastern side of the inner harbour ..................... 60
53. A seismic-reflection profile from Bedford Bay,
Bedford Basin ............................................. 61
54. Seismic-reflection profile from the inner harbour
northeast of Georges Island ............................... 63
55. Vibrocore logs from samples collected near Georges
Island .................................................... 64
56. Distribution of lacustrine sediments buried in isolated
basins throughout Halifax Harbour ......................... 65
57. Seismic-reflection profile of the Sable Island Sand
and Gravel from the outer harbour ......................... 67
58. Seismic-reflection profile of the Sable Island Sand
and Gravel from the outer harbour ......................... 68
59. A seismic-reflection profile north of McNabs Island
off Ives Point showing relict gravel ridges ............... 69
60. A sidescan sonogram of the Sable Island Sand and Gravel
from The Narrows .......................................... 70
61. A sidescan sonogram of gravel ripples and sand patches
in the outer harbour ...................................... 71
62. A seismic-reflection profile from the inner harbour
showing a small, buried channel ........................... 72
63. Bottom photographs of the Sable Island Sand and Gravel .... 73
64. Map showing the distribution of boulders in the
outer harbour ............................................. 74
65. Sidescan sonograms from the outer harbour showing the
transition from shallow water bedrock to deep-water
flat sand ................................................. 75
66. A sidescan sonogram showing large featureless sand
patches ................................................... 76
67. A seismic-reflection profile showing the stratigraphy
adjacent to Georges Island ................................ 77
68. A sidescan sonogram from The Narrows ...................... 78
69. A sidescan sonogram across Jonquiere Bank ................. 79
70. A map of boulder berms in Bedford Basin ................... 80
71. A 3-D perspective view of the western area of
Bedford Basin ............................................. 80
72. A 3-D perspective view of the northwestern area of
Bedford Basin ............................................. 81
73. A sidescan sonogram from Bedford Basin showing two
boulder berms ............................................. 81
74. Multibeam-bathymetric image showing boulder berms
between Pleasant Shoal and McNabs Island .................. 82
75. Sidescan sonogram of mined trenches and pits .............. 82
76. A seismic-reflection profile of LaHave Clay onlapping
till ...................................................... 83
77. A seismic-reflection profile north of Georges Island
showing the LaHave Clay ................................... 84
78. A seismic-reflection profile from Dartmouth Cove .......... 85
79. A section of a sidescan-sonar mosaic from the
inner harbour ............................................. 86
80. Core logs of silt and clay content through LaHave Clay .... 87
81. Bottom photograph of LaHave Clay from Bedford Bay ......... 91
82. A seismic-reflection profile from the northwestern flank
of Bedford Basin .......................................... 92
83. A seismic-reflection profile from the southern area
of Bedford Bay ............................................ 93
84. A sidescan sonogram of the southern area of The Narrows ... 94
85. Seismic-reflection profiles comparing and contrasting
the relationship between LaHave Clay and the Sable
Island Sand and Gravel .................................... 95
86. Sidescan sonograms of waste-water outfalls ................ 96
87. A seismic-reflection profile and a sidescan sonogram
from south of Georges Island .............................. 97
88. A seismic-reflection profile from Northwest Arm adjacent
to Sir Sandford Fleming Park .............................. 98
89. Isopach map of the LaHave Clay for the area south of The
Narrows ................................................... 99
90. A seismic-reflection profile of an isolated deposit of
LaHave Clay north of eastern Pleasant Shoal .............. 101
91. Seismic-reflection profiles from a variety of systems
of gas-charged sediments in areas of Halifax Harbour ..... 102
92. Distribution of gas-charged sediment in
Halifax Harbour .......................................... 103
93. A seismic-reflection profile from Bedford Basin showing
the gas-charged reflector within LaHave Clay ............. 104
94. Sidescan sonograms and multibeam-bathymetric image of
pockmarks at the entrance to Northwest Arm ............... 105
95. Sidescan sonogram and seismic-reflection profile over
a dredge spoil ........................................... 106
96. A sidescan sonogram illustrating sand ribbons on
the seabed ............................................... 107
97. Classification and distribution of bed forms in
the outer harbour ........................................ 108
98. A sidescan sonogram of degraded megaripples northeast
of Mars Rock and Sandwich Point .......................... 109
99. A sidescan sonogram illustrating megaripples in sand
of the Sable Island Sand and Gravel in the outer
harbour .................................................. 109
100. Sidescan sonograms from an area of gravel circles ........ 111
101. Bottom photographs of gravel circles adjacent to
Bear Cove Shoal .......................................... 112
102. A multibeam-bathymetric image of sedimentary furrows ..... 113
103. Interpretation of seabed morphology, features, and
processes, Northwest Arm, Halifax Harbour ........ (on CD-ROM)
104. Sidescan sonograms and a seismic-reflection profile of
sedimentary furrows from the western side of the
harbour .................................................. 113
105. A diagrammatic model for the formation of sedimentary
furrows .................................................. 114
106. Seismic-reflection profile from the inner harbour
showing a moat ........................................... 115
107. A seismic-reflection profile across the Georges
Island moat .............................................. 116
108. A multibeam-bathymetric image showing bedrock,
current-scoured depressions, and erosional remnants
of LaHave Clay ........................................... 117
109. A sidescan sonogram of a scoured, 2 m deep, linear
depression in LaHave Clay ................................ 120
110. A sidescan sonogram east of Middle Ground showing an
area of thin LaHave Clay with scouring around large
boulders ................................................. 120
111. A composite of sidescan sonograms of several of the
shipwrecks of Halifax Harbour ............................ 121
112. A multibeam-bathymetric image adjacent to Ives Knoll
over an area termed the 'fisherman hole' ................. 122
113. Sidescan sonograms of anchor-related marks on the
seabed of Halifax Harbour ................................ 123
114. The distribution and density of anchor marks in the
inner harbour and Bedford Basin .......................... 125
115. Sidescan sonogram from central Bedford Basin showing
types of anchor marks at the seabed ...................... 126
116. Sidescan sonograms of dredge spoils ...................... 127
117. A sidescan sonogram of linear dredge spoils from the
inner harbour ............................................ 128
118. A sidescan sonogram, artists reconstruction,
seismic-reflection profile, bottom photograph, and
photograph of clinkers of the 'Trongate depression' ...... 130
119. A multibeam-bafhymetric image looking across the seabed
from a position northeast of Georges Island .............. 131
120. A multibeam-bathymetric image from Eastern Passage
showing mud berms ........................................ 131
121. A sidescan sonogram of southern Thrumcap Shoal showing
acoustic targets at the location of the grounding of
the vessel H.M.S. Tribune in 1769 ........................ 132
122. A sidescan sonogram of jack-up oil-rig spud-can marks
on the seabed of Halifax Harbour ......................... 133
123. A sidescan sonogram of semisubmersible, oil-drilling-
rig pontoon marks on the seabed of Halifax Harbour ....... 133
124. A sidescan sonogram of the seabed and photograph of
the grounded container ship Concert Express .............. 134
125. A sidescan sonogram of propeller scours on the seabed
of Halifax Harbour ....................................... 135
126. A sidescan sonogram of a dredged drumlin in inner
Halifax Harbour .......................................... 136
127. A sidescan sonogram of a blasted and dredged, shallow
bedrock area in The Narrows .............................. 136
128. Sidescan sonograms of the seabed of The Narrows .......... 138
129. A sidescan sonogram from The Narrows showing large logs
on the seabed ............................................ 139
130. A sidescan sonogram showing circular, medium-intensity
backscatter features ..................................... 139
131. A sidescan sonogram and multibeam-bathymetric image of
seabed moorings from Northwest Arm ....................... 140
132. A sidescan sonogram illustrating a cable on the seabed
of the outer harbour ..................................... 141
133. A sidescan sonogram off Purdy's Wharf, showing a water
intake for building cooling .............................. 142
134. A sidescan sonogram of northeast Bedford Basin and a
sonar target interpreted as the tail section of a
Havoc airplane ........................................... 142
135. A sidescan sonogram of approximately 25 Volvo
automobiles on the bottom of Bedford Basin ............... 144
136. A sidescan sonogram of a large cribwork on the seabed
off Black Rock Beach in south Halifax .................... 144
137. A map showing the distribution of the clay content in
sediments of Halifax Harbour ............................. 144
138. A map showing the distribution of organic carbon in
sediments of Halifax Harbour ............................. 145
139. A factor map showing areas dominated by contamination
processes and source areas ............................... 145
140. A map of the distribution of mercury anomalies in
seabed sediments ......................................... 146
141. Regional bathymetry of the inner Scotian Shelf off
Halifax Harbour showing the major topographic
elements that controlled the direction of glacial-ice
movement ................................................. 147
142. Interpreted pathway of the 'ancient Sackville River'
in Halifax Harbour ....................................... 148
143. A seismic-reflection profile between Georges Island
and the adjacent Halifax shoreline ....................... 149
144. A seismic-reflection profile at the mouth of Halifax
Harbour .................................................. 150
145. A paleogeographic reconstruction of Bedford Basin at
approximately 6000 BP .................................... 151
146. A multibeam-bathymetric image of an end moraine from
the inner area of Northwest Arm .......................... 152
147. A Holocene relative sea-level curve for Halifax
Harbour .................................................. 153
Table caption
1. Table of formations for the bedrock and surficial
sediments in Halifax Harbour ................................ 53
|
