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7.7.2| DETAILED DESCRIPTION

In document GEOPHYSICAL SURVEY REPORT (Sider 131-147)

7.4| DESCRIPTION OF DATA INTERPRETATION

7.7.2| DETAILED DESCRIPTION

A detailed presentation of the conditions and features on Route 4 are shown in Table 31.

Table 31 Route 4 seabed details.

KP ASSOCIATED CHART DESCRIPTION

(INCLUDING MIN/MAX DEPTH BSB TO BASE OF UNIT)

REMARK

Undulating dune system between KP 0.000 and crest of dune at KP 0.134. Dune very steeply descends from 19.16 m to 2.11 m at KP 0.205. Beach gently slopes to surf zone at 1.26 m at KP 0.245.

Maximum Elevation +19.16 at KP 0.134 Minimum Elevation +1.26 m at KP 0.245

Moderately deepening seafloor from landfall westward with sandwaves and channels.

Minimum depth -3.75 m at KP 0.477.

Maximum depth -22.02 m at KP 11.721.

Some evidence of boulder scattering at KP 1.900 and KP 4.000.

Sandwaves and channels evident (Figure 90).

Total elevation/depth range = 41.18 m

Maximum slope on landfall of 43.0° at KP 0.167.

Maximum slope sub-sea of 7.9° at KP 1.305.

Surficial geology:

SSS coverage starts at KP 0.427.

This section is dominated by SAND.

Adjacent to the landfall, patches of gravelly SAND to sandy GRAVEL and GRAVEL is occasionally observed. DIAMICTON is also present as scattered, discrete patches up until KP 4.523.

The patches of DIAMICTON are often associated with surrounding occasional boulders fields.

An area of sandwaves are present near the shore line at KP 0.427 to KP 0.685. A further, isolated sandwave crest crosses the survey corridor at KP 8.590.

Fields of occasional boulders crossing the route between:

 KP 1.765 and KP 1.863

 KP 1.910 and KP 1.929

 KP 1.943 and KP 2.003

Fields of numerous boulders crossing the route between:

 KP 3.794 and KP 3.799

PAGE | 133 KP ASSOCIATED CHART DESCRIPTION

(INCLUDING MIN/MAX DEPTH BSB TO BASE OF UNIT)

REMARK

A large area of depressions are present in the latter parts of the section, crossing the survey route between KP 10.635 and KP 11.367.

Area of depression crossing the route between:

 KP 10.541 and KP 11.368

Shallow Geology:

SBP coverage begins at KP 0.477.

KP 0.477 to KP 0.828: SAND, fine to coarse (0.8 – 3.0 m BSB) with internals of gravels overlaying either channel infills, silty SAND (1.2 – 5.1 m BSB) or silty sandy CLAY.

KP 0.828 to KP 1.302: SAND, fine to coarse (0.2 – 1.4 m BSB) with internals of gravels overlaying silty sandy CLAY.

KP 1.302 to KP 1.319: Sandy gravelly CLAY outcrops at seabed.

KP 1.319 to KP 1.843: SAND, fine to coarse (0.3 – 1.0 m BSB) with internals of gravels overlaying sandy gravelly CLAY.

KP 1.843 to KP 1.889: Sandy gravelly CLAY outcrops at seabed.

KP 1.889 to KP 4.330: Silty SAND (0.3 – 1.9 m BSB) with internals of GRAVEL overlaying silty sandy CLAY.

Channel infills (1.2 – 3.1 m BSB) with silty SAND were observed between KP 3.835 to KP 4.022.

KP 4.330 to KP 4.338: Sandy gravelly CLAY outcrops at seabed.

KP 4.338 to KP 4.410: A thin layer of gravelly SAND (0.2 – 0.7 m BSB) overlaying silty sandy CLAY.

(Figure 97), (Figure 98), (Figure 99), (Figure 100), (Figure 101) and (Figure 102)

KP ASSOCIATED CHART DESCRIPTION

(INCLUDING MIN/MAX DEPTH BSB TO BASE OF UNIT)

REMARK

KP 4.410 to KP 4.424: Sandy gravelly CLAY outcrops at seabed.

KP 4.424 to KP 4.494: A thin layer of gravelly SAND (0.2 – 0.7 m BSB) overlaying silty sandy CLAY.

KP 4.494 to KP 4.528: Sandy gravelly CLAY outcrops at seabed.

KP 4.528 to KP 7.568: Silty SAND (0.3 – 2.3 m BSB) with internals of GRAVEL overlaying silty sandy CLAY.

KP 7.568 to KP 11.734: Silty SAND (0.7 – 2.7 m BSB) with internals of GRAVEL overlaying either channel infills, Sandy CLAY (2.6 – 7.7 m BSB) or silty sandy CLAY.

The seabed undulates within this section as the route crosses erosion channels and occasional sandwaves.

Minimum depth -20.00 m at KP 12.851.

Maximum depth -25.79 m at KP 16.945.

Very gentle to moderate slopes.

Depths range = 5.8 m.

Maximum slope of 3.9° at KP 16.943.

Surficial Geology:

The surface geology is dominated by SAND associated with a large area of depressions (Figure 91).

Areas of depressions crossing the route between:

 KP 13.204 and KP 14.461

 KP 14.655 and KP 16.732 Shallow Geology:

KP 11.734 to KP 11.873: Silty SAND (0.4 – 0.9 m BSB) with internals of GRAVEL overlaying silty SAND.

KP 11.873 to KP 11.917: Fine silty SAND outcrops at seabed.

(Figure 103), (Figure 104)

PAGE | 135 KP ASSOCIATED CHART DESCRIPTION

(INCLUDING MIN/MAX DEPTH BSB TO BASE OF UNIT)

REMARK

KP 12.066 to KP 12.251: Silty sandy CLAY outcrops at seabed.

KP 12.251 to KP 16.958: Silty gravelly SAND (0.3 – 2.7 m BSB) overlaying channel infills, silty clayey SAND (0.8 – 4.9 m BSB).

16.958 – 17.485

103282-ENN-MMT-SUR-DWG-ALR40003

Bathymetry:

The seabed is broadly flat and smooth with occasional erosional channels.

Minimum depth -24.90 m at KP 17.215.

Maximum depth -26.24 m at KP 17.149.

Very gentle to gentle slopes.

Depths range = 1.3 m.

Maximum slope of 6.0° at KP 17.155 Surficial Geology:

Complex area with surface geology mainly composed of GRAVEL and gravelly SAND to sandy GRAVEL associated with occasional and numerous boulders and ripples (Figure 92).

DIAMICTON is also present in the southern part of the corridor.

(Figure 92).

Fields of occasional boulders cross the route between:

 KP 16.958 and KP 16.976

 KP 16.976 and KP 17.010

 KP 17.010 and KP 17.044

 KP 17.044 and KP 17.099

 KP 17.111 and KP 17.149

Fields of numerous boulders cross the route between

 KP 17.149 and KP 17.227

 KP 17.227 and KP 17.485 Shallow Geology:

KP 16.958 to KP 17.485: Silty gravelly CLAY outcrops at seabed.

The seabed deepens gently becoming more increasingly textured with ripples, occasional and numerous boulder fields.

Minimum depth -22.40 m at KP 18.163.

Maximum depth -29.67 m at KP 24.207.

Very gentle to gentle.

Depth range =7.3 m.

Maximum slope of 4.7° at KP 17.875

Surficial Geology: Area of depression crossing the route between:

KP ASSOCIATED CHART DESCRIPTION

(INCLUDING MIN/MAX DEPTH BSB TO BASE OF UNIT)

REMARK

The section is dominated by SAND

Gravelly SAND to Sandy GRAVEL are frequently observed at the start of the section but become sparse towards the end of the route at KP 24.335. These coarse sediment areas are sometimes associated with ripples and numerous or occasional boulder fields.

A discreet area of sandwaves are observed adjacent to the southern boundary of the survey corridor between KP 18.148 to KP 18.939 (sediment transport direction South).

A large area of depressions is present in the latter part of the section (Figure 93).

 KP 22.240 and KP 23.002

Shallow Geology:

KP 17.485 to KP 18.000: Silty SAND (0.4 – 1.6 m BSB) with internals of GRAVEL overlaying channel infills, silty gravelly CLAY (1.1 – 2.2 m BSB).

KP 18.000 to KP 18.025: Silty gravelly CLAY outcrops at seabed. The base of the channel infills is at 2.6 m BSB.

KP 18.025 to KP 23.206: Silty SAND (0.3 – 1.8 m BSB) with internals of GRAVEL overlaying either channel infills, silty SAND (1.4 – 3.9 m BSB) through Sandy gravelly CLAY.

KP 23.206 to KP 23.311: A thin layer of gravelly SAND (0.2 – 0.5 m BSB) overlaying channel infills, silty sandy CLAY (1.1 – 1.5 m BSB). Overlies silty SAND.

KP 23.311 to KP 24.235: Silty SAND (0.3 – 0.8 m BSB) with internals of GRAVEL overlaying channel infills, silty SAND (0.6 –

(Figure 105), (Figure 106), (Figure 107) and (Figure 108)

PAGE | 137 KP ASSOCIATED CHART DESCRIPTION

(INCLUDING MIN/MAX DEPTH BSB TO BASE OF UNIT)

REMARK

KP 24.235 to KP 24.401: A thin layer of gravelly SAND (0.5 m BSB) overlaying channel infills, silty SAND (0.6 – 1.4 m BSB).

Overlies silty Clayey gravelly SAND.

Figure 90 Sandwave and shallow channel at KP 8.225 to KP 11.148.

Depth convention in NaviModel is positive down; vertical exaggeration of profile x100.

PAGE | 139

Figure 92 Overview of surficial geology from KP 16.5 to KP 18.3 as seen on SSS.

The gap is due to fishing equipment that required a deviation by the survey vessel to avoid entanglement.

Figure 93 Overview of surficial geology from KP 21.9 to KP 23.6 as seen on SSS..

Figure 94 Side scan sonar image illustrating a sandwave crossing survey corridor at KP 8.588.

Figure 95 MBES image KP 8.311 (DCC 104.55)

PAGE | 141 Figure 96 Side scan sonar image KP 8.311, (DCC 104.55) Possible fishing gear with the rope still attached on SAND.

Figure 97 Innomar SBP data example from KP 0.497 (E) to KP 1.544 (W).

Showing SAND overlying channel infills, silty SAND. Silty sandy CLAY outcrops at seabed.

Figure 98 Innomar SBP data example from KP 2.461 (E) to KP 3.674 (W).

Showing silty SAND with internals of GRAVEL overlying silty sandy CLAY.

Figure 99 Innomar SBP data example from KP 3.670 (E) to KP 4.338 (W).

Showing silty SAND overlying channel infills, silty SAND. Silty sandy CLAY outcrops at seabed.

PAGE | 143

Figure 100 Innomar SBP data example from KP 5.922 (E) to KP 7.299 (W).

Showing silty SAND with internals of GRAVEL overlying silty sandy CLAY.

Figure 101 Innomar SBP data example from KP 8.525 (E) to KP 9.911 (W).

Showing silty gravelly SAND overlying silty sandy CLAY.

Figure 102 Innomar SBP data example from KP 10.173 (E) to KP 11.695 (W).

Showing silty gravelly SAND with internals of GRAVEL overlying channel infills, silty SAND.

Figure 103 Innomar SBP data example from KP 11.152 (E) to KP 12.544 (W).

Showing silty gravelly SAND with internals of GRAVEL overlying channel infills, silty SAND. Silty SAND outcrops at seabed.

PAGE | 145

Figure 104 Innomar SBP data example from KP 12.826 (E) to KP 14.244 (W).

Showing silty SAND with internals of GRAVEL overlying either channel infills, silty SAND or silty sandy CLAY.

Figure 105 Innomar SBP data example from KP 16.841 (E) to KP 18.262 (W).

Showing silty SAND with internals of GRAVEL overlying channel infills, silty gravelly CLAY. Silty gravelly CLAY outcrops at seabed.

Figure 106 Innomar SBP data example from KP 21.331 (E) to KP 22.791 (W).

Showing silty SAND with internals of GRAVEL overlying either channel infills, silty SAND or silty gravelly CLAY.

Figure 107 Innomar SBP data example from KP 22.498 (E) to KP 24.000 (W).

Showing silty SAND with internals of GRAVEL overlying channel infills, sandy gravelly CLAY. Overlies silty SAND.

PAGE | 147

Figure 108 Innomar SBP data example from KP 23.948 (E) to KP 24.401 (W).

Showing silty SAND with internals of GRAVEL and gravelly SAND overlying channel infills, silty SAND. Overlies clayey gravelly SAND.

In document GEOPHYSICAL SURVEY REPORT (Sider 131-147)