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| Value | Definition |
|---|---|
| A1 | Abbreviated symbol for A1 r_cgS |
| A2 | Abbreviated symbol for A2 i_cgS |
| B | Abbreviated symbol for B r_cgS / i_cbG |
| C | Abbreviated symbol for C i_cbG |
| D1 | Abbreviated symbol for D1 i_cgS / pbcG |
| D2 | Abbreviated symbol for D2 i_mcgS / pcbG |
| E | Abbreviated symbol for E i_cgS |
| F | Abbreviated symbol for F i_cgS / pbcG |
| G1 | Abbreviated symbol for G1 i_mfgS |
| G2 | Abbreviated symbol for G2 i_mfgS |
| Value | Definition |
|---|---|
| A1 r_cgS | Rippled, coarse-grained sand. Substrate A1 is a mobile sand deposit on the upper flank of Stellwagen Bank. Depth range is 30 to 56 m. Mean weight percents per grain-size category: mud <1; sand 90 (fgS, 3; cgS, 88); gravel 9 (G1, 8; G2, 1). Substrate A1 is equivalent to the mobile portion of adjacent substrate B; and it is similar to adjacent immobile substrate A2 which lies at deeper depths (53 to 77 m) on the lower flank of Stellwagen Bank and contains more fine-grained sand (11 weight percent). |
| A2 i_cgS | Immobile, coarse-grained sand. Substrate A2 is an immobile sand deposit on the lower flank of Stellwagen Bank. Depth range is 53 to 77 m. Mean weight percents per grain-size category: mud 1; sand 83 (fgS, 11; cgS, 72); gravel, 16 (G1, 11; G2, 5). Substrate A2 is similar to adjacent mobile substrate A1 which lies at shallower depths (30 to 56 m) and contains less fine-grained sand (3 weight percent). It contains less mud and fine-grained sand than substrate E. |
| B r_cgS / i_cbG | Rippled, coarse-grained sand; partial veneer on immobile, cobble, boulder gravel. Substrate B is a layered substrate of mobile sand overlying immobile gravel on the shallow flank of Stellwagen Bank. Depth range is 36 to 58 m. Mean weight percents per grain-size category: mud, <1; sand, 92 (fgS, 5; cgS, 86); gravel, 8 (G1, 7; G2, 1). Cobbles and boulders are identified on the basis of video and photographic imagery. Boulder ridges (substrate C) are present. The mobile sand layer of substrate B is equivalent to adjacent mobile substrate A1. |
| C i_cbG | Immobile, cobble, boulder gravel. Substrate C is immobile gravel that forms topographic ridges where cobbles and boulders are piled upon one another and are separated by voids. It is identified on the basis of video and photographic images of mapped topographic ridges. It is present on the flank of Stellwagen Bank where it is associated with substrate B (36 to 58 m) and substrate D1 (50 to 83 m), and on the tops of North, East, and Middle Ninety Banks where it is associated with substrate D2 (87 to 105 m). It is equivalent to boulder ridges <1 m and >=1m on Maps A, E, F, and G. |
| D1 i_cgS / pcbG | Immobile, coarse-grained sand; partial veneer on pebble, cobble, boulder gravel. Substrate D1 is a layered substrate of immobile sand overlying immobile gravel on the flank of Stellwagen Bank. Depth range is 50 to 83 m. Mean weight percents per grain-size category: mud, 4; sand, 50 (fgS, 16; cgS, 34); gravel, 45 (G1, 11; G2, 34). Pebbles, cobbles, and boulders are identified on the basis of video and photographic imagery. Boulder ridges (substrate C) are present. Substrate D1 is similar to substrate D2 which lies at deeper depths (87 to 105 m) on the tops of North, East, and Middle Ninety Banks and has higher mud content (12 weight percent). |
| D2 i_mcgS / pcbG | Immobile, muddy, coarse-grained sand; partial veneer on pebble, cobble, boulder gravel. Substrate D2 is a layered substrate of immobile sand overlying immobile gravel on the tops of North, East, and Middle Ninety Banks. Depth range is 87 to 105 m. Mean weight percents per grain-size category: mud, 12; sand, 76 (fgS, 22; cgS, 55); gravel, 12 (G1, 8; G2, 4). Pebbles, cobbles, and boulders are identified on the basis of video and photographic imagery. Boulder ridges (substrate C) are present. Substrate D2 is similar to substrate D1 which lies at shallower depths (50 to 83 m) on the flank of Stellwagen Bank and has lower mud content (4 weight percent). |
| E i_cgS | Immobile, coarse-grained sand. Substrate E is an immobile sand deposit on the lower flank of Stellwagen Bank. Depth range is 66 to 122 m. Mean weight percents per grain-size category: mud 4; sand, 82 (fgS, 18; cgS, 64); gravel, 14(G1, 9; G2, 5). Boulder ridges are absent. Substrate E is similar in mud content to substrate D1 and contains more mud and fine-grained sand than substrate A2. |
| F i_cgS / pcbG | Immobile, coarse-grained sand; partial veneer on pebble, cobble, boulder gravel. Substrate F is a layered substrate of immobile sand overlying immobile gravel on the flanks of the Ninety Meter Banks. Depth range is 90 to 148 m. Mean weight percents per grain-size category: mud, 9; sand, 69 (fgS, 25; cgS, 44); gravel, 22 (G1, 13; G2, 9). Pebbles, cobbles, and boulders are identified on the basis of video and photographic imagery. Boulder ridges are absent. Substrate F is similar to substrates D1 and D2, except that F lies at deeper depths, and the partial veneer of coarse grained sand on the gravel is more extensive. |
| G1 i_mfgS | Immobile, muddy, fine-grained sand. Substrate G1 is an immobile muddy sand deposit in valleys between Stellwagen Bank and the Ninety Meter Banks. Depth range is 85 to 171 m. Mean weight percents per grain-size category: mud, 10; sand, 88 (fgS, 78; cgS, 10); gravel, 1 (G1, 1; G2, 1). Substrate G1 is similar to substrate G2 which lies at deeper depths (125 to 185 m) and has higher 4 phi sand (58 weight percent) and higher mud content (23 weight percent). |
| G2 i_mfgS | Immobile, muddy, fine-grained sand. Substrate G2 is an immobile muddy sand deposit in deep parts of valleys lying between the Ninety Meter Banks. Depth range is 125 to 185 m. Mean weight percents per grain-size category: mud, 23; sand, 77 (fgs, 77; cgS, 1); gravel, 0. Substrate G2 has the highest mud content of all substrates in quadrangle 6. |
| Value | Definition |
|---|---|
| mobile sediment | Rippled sand; equivalent to substrate A1. |
| mobile and immobile sediment | Rippled sand overlying immobile cobble and boulder gravel; equivalent to substrate B. |
| immobile sediment | Sand, sand partial veneer on gravel, and muddy sand; equivalent to substrates A2, D1, D2, E, F, G1, and G2. |
| boulder ridges <1 meter in height | Ridges <1 meter in height equivalent to substrate C. |
| boulder ridges >=1 meter in height | Ridges >=1 meter in height equivalent to substrate C. |
| Value | Definition |
|---|---|
| fine-grained substrate | Muddy sand in which fine-grained sand (3 and 4 phi combined) constitutes > 50 mean weight percent of the sand fraction; equivalent to substrates G1 and G2. |
| coarse-grained substrate | Sand and sand partial veneer on gravel in which coarse-grained sand (2, 1, and 0 phi combined) constitutes > 50 mean weight percent of the sand fraction; equivalent to substrates A1, A2, B, D1, D2, E, and F. |
| boulder ridges <1 meter in height | Ridges <1 meter in height equivalent to substrate C. |
| boulder ridges >=1 meter in height | Ridges >=1 meter in height equivalent to substrate C. |
| Value | Definition |
|---|---|
| <= 1 | mud content <= 1 mean weight percent, equivalent to substrates A1, A2, and B. |
| >1 to 5 | mud content >1 to 5 mean weight percent, equivalent to substrates D1 and E. |
| >5 to 10 | mud content >5 to 10 mean weight percent, equivalent to substrates F and G1. |
| >10 to 20 | mud content >10 to 20 mean weight percent, equivalent to substrate D2. |
| >20 to 50 | mud content >20 to 50 mean weight percent, equivalent to substrate G2. |
| boulder ridges <1 meter in height | Ridges <1 meter in height equivalent to substrate C. |
| boulder ridges >=1 meter in height | Ridges >=1 meter in height equivalent to substrate C. |
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The following information was used as guidelines to derive individual units.
Individual sediment samples were aggregated into substrate types by comparing their textural composition, with special emphasis placed on:
(1) mean grain size in phi units; (2) standard deviation from the mean of grain size distribution (degree of sorting) in phi units; (3) significant grain size(s) in phi units; (4) mud, sand and gravel contents in weight percents of the sample; (5) sand fraction subdivided into fine grained sand (3 and 4 phi) and coarse grained sand (0, 1, and 2 phi) in weight percents of the sample; (6) gravel fraction subdivided into G1 (-1 and -2 phi) and G2 (-3, -4, and -5 phi) in weight percents of the sample.Gravel pebbles larger than -5 phi (6.4 cm) were not collected in this study, although larger pebbles, cobbles, and boulders were observed in seabed imagery.
Mobility of sediments was determined by the presence or absence of sand ripples, as viewed in video and photographic imagery.
Substrate layering was determined by the presence of a layer of finer sediment overlying (but not completely covering) coarser sediment, as viewed in video and photographic imagery.
This process took place over a number of years, 2005-2010. Data sources used in this process:
Online Links:
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| Access_Constraints | None |
|---|---|
| Use_Constraints | The interpretation was completed at a map scale of 1:25,000. |
| Data format: | This WinZip (version 14.0) contains the shapefile, browse graphic, and associated metadata. Additionally, ArcGIS 9.3.1 layer files are included for each variation of the mapping units. in format Shapefile (version ArcGIS 9.3.1) Size: 0.62 |
|---|---|
| Network links: |
https://pubs.usgs.gov/sim/3341/data/SIM3341_geologic_interp.zip |
