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| Range of values | |
|---|---|
| Minimum: | 1 |
| Maximum: | 73 |
| Value | Definition |
|---|---|
| A1 | Abbreviated symbol for A1 r_cgS where r = rippled, cgS = coarse-grained sand |
| A3 | Abbreviated symbol for A3 r_cgS where r = rippled, cgS = coarse-grained sand |
| B | Abbreviated symbol for B r_cgS / i_cbG where r = rippled, cgS = coarse-grained sand, / = overlying, or partial veener over, i = immobile, c = cobble, b = boulder, G = gravel |
| C | Abbreviated symbol for C i_cbG where i = immobile, c = cobble, b = boulder, G = gravel |
| H | Abbreviated symbol for H r_fgS where r = rippled, fgS = fine-grained sand |
| I | Abbreviated symbol for I i_fgcgS where i = immobile, fgcgS = fine- and coarse-grained sand |
| J | Abbreviated symbol for J r_cgfgS / i_pcbG where r = rippled, cgfgS = coarase- and fine-grained sand, / = overlying, or partial veener over, i = immobile, p = pebble, c = cobble, b = boulder, G = gravel |
| K | Abbreviated symbol for K r_cgS where r = rippled, cg = coarse-grained, s = sand |
| L | Abbreviated symbol for L i_mfgS where i = immobile, m = muddy, fgS = fine-grained sand |
| M | Abbreviated symbol for M i_mcgS / pcbG where i = immobile, m = muddy, cgS = coarse-grained sand, / = overlying, or partial veener over, p = pebble, c = cobble, b = boulder, G = gravel |
| P | Abbreviated symbol for P i_mfgS where i = immobile, m = muddy, fgS = fine-grained sand |
| Q | Abbreviated symbol for Q i_mfgS / pcbG where i = immobile, m = muddy, fgS = fine-grained sand, / = overlying, or partial veener over, p = pebble, c = cobble, b = boulder, G = gravel |
| R | Abbreviated symbol for R i_fgsM where i = immobile, fgS = fine-grained sand, M = mud |
| S | Abbreviated symbol for S i_M where i = immobile, M = mud |
| T | Abbreviated symbol for T i_mcgS / pcbG where i = immobile, m = muddy, cgS = coarse-grained sand, / = overlying, or partial veener over, p = pebble, c = cobble, b = boulder, G = gravel |
| U | Abbreviated symbol for U i_pcG where i = immobile, p = pebble, c = cobble, G = gravel |
| V | Abbreviated symbol for V i_fgsM / cbG where i = immobile, fgS = fine-grained sandy, M = mud, / = overlying, or partial veener over, c = cobble, b = boulder, G = gravel |
| Value | Definition |
|---|---|
| A1 r_cgS | Rippled, coarse-grained sand. Substrate A1 is a mobile, coarse-grained sand deposit that lies on the crest and upper western flank of Stellwagen Bank in quadrangle 5. Substrate A1 is very widespread on the bank. It also occurs on the eastern flank of the bank in quadrangle 6 (Valentine and Gallea, 2015) to the east and on the southwestern and southeastern flanks of the bank in quadrangle 2 and quadrangle 3, respectively. The irregular, digitated margin of the downslope edge of A1 in quadrangle 5 suggests that the substrate there represents a sheet of sand that was transported westward onto the western flank from the bank crest. The nature of transport is not known. Water depth range of the stations is 24 to 53 m and of the mapped substrate 24 to 55 m. Substrate A1 is equivalent to the upper mobile layer of substrate B which lies within the region occupied by substrate A1. Grain-size analyses of all samples identified as substrate A1 were used to calculate the mean weight percents of aggregates and composite grades: mud, less than 1; sand, 94 (fgS, 3; cgS, 90); gravel, 6 (G1, 5; G2, 1). Substrate A1 is dominantly coarse-grained sand and is very low in mud and fine-grained sand content. Its surface is covered with storm-generated sand ripples with wavelengths of 0.5 to 1.0 m, and the orientation of ripple crests varies from N-S to NW-SE. The ripples are symmetrical and well-shaped (sometimes with narrow, sharply-defined crests and sometimes with broad crests hosting secondary ripples) when first formed by storm wave currents, but subsequently are rounded by faunal disturbance and flattened by bottom-tending fishing gear such as dredges and trawls. These relatively large bedforms are not discernible in multibeam topographic imagery. Substrate A1 is similar to substrate A3 in its mud and sand content and lies at similar water depths. However, substrate A3 contains much more fine-grained sand (22 weight percent). Each sample from A3 generally contains 10 weight percent or more of fine-grained sand, mostly as 3 phi sand, and its surface is covered with smaller ripples. |
| A3 r_cgS | Rippled, coarse-grained sand. Substrate A3 is a collection of mobile, coarse-grained sand deposits that lies on the crest and upper western flank of Stellwagen Bank. Water depth range of the stations is 23 to 53 m. Grain-size analyses of all samples identified as A3 were used to calculate the mean weight percents of aggregates and composite grades: mud, less than 1; sand, 98 (fgS, 22; cgS, 76); gravel, 1 (G1, 1; G2 <1). Substrate A3 is similar to substrate A1 in being a coarse-grained sand and having a very low mud content. It differs from A1 in having much more fine-grained sand (22 weight percent), mostly as 3 phi sand, and its surface ripples are much smaller, with wavelengths of 10 to 20 cm. Substrate A3 is also similar to substrate A2, which lies on the far eastern flank of the bank in quadrangle 6 (Valentine and Gallea, 2015). They both contain more fine-grained sand than substrate A1, but A2 is immobile and has less fine-grained sand than A3, and it lies at deeper water depths (53-77 m). In quadrangle 5, substrate A3 occurs in large and small deposits, and most are not mappable as coherent units at the present scale. Some form irregular hummocks that are visible in bathymetric imagery; and deposits of substrate A1 occur between the hummocks. Deposits of substrate A3 also occur intermittently along the deep western edge of substrate A1. Substrate A3 deposits are texturally equivalent to substrate K, which lies at deeper depths, but A3 deposits are geographically separated from substrate K by substrate H. The largest deposit of A3 occurs in an area of hummocky seabed (observed in multibeam topographic imagery) on the bank crest within a provisional, straight-sided polygon. Some stations that represent substrate A1 occur within this A3 polygon. |
| B r_cgS / i_cbG | Rippled, coarse-grained sand; partial veneer on immobile cobble, boulder gravel. Substrate B is a layered substrate of mobile, coarse-grained sand partially overlying the margins of immobile cobble, boulder gravel features (gravel mounds, boulder ridges) in small areas surrounded by substrate A1 on the crest and upper eastern flank of Stellwagen Bank. Sixteen provisional, straight-sided polygons centered on gravel features show the approximate distribution of substrate B. Water depth range of the mapped substrate is 30 to 44 m. The rippled, coarse-grained sand upper layer of substrate B is equivalent to substrate A1. For mean weight percents of aggregates and composite grades of this upper layer of substrate B, see substrate A1. The substrate also occurs on the eastern flank of the bank in adjacent quadrangle 6 (Valentine and Gallea, 2015). The gravel features of substrate B are identified based on multibeam topographic imagery and video and photographic imagery. |
| 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. Water depth range of the mapped substrate is 30 to 65 m. It is identified on the basis of video and photographic images of mapped topographic ridges (Valentine, 2005) and is shown as boulder ridges less than 1 m and ≥1 m high. It is present in three areas in quadrangle 5: on the upper eastern flank and crest of Stellwagen Bank where it occurs with substrate B; on Western Spur where it occurs with substrate L; and on Southwestern Spur where it occurs with substrate Q. Substrate C occurs more commonly in adjacent quadrangle 6 on the eastern flank of Stellwagen Bank and on the tops of the Ninety Meter Banks (Valentine and Gallea, 2015). |
| H r_fgS | Rippled, fine-grained sand. Substrate H is a mobile, fine-grained sand deposit that lies on the lower western flank of Stellwagen Bank in the southern part of quadrangle 5. Water depth range of the stations is 38 to 52 m and of the mapped substrate 35 to 52 m. Mean weight percents of aggregates and composite grades: mud, 2; sand, 98 (fgS, 83; cgS, 15); gravel, less than 1 (G1, <1; G2, 0). Substrate H extends southward into quadrangle 2. The surface of substrate H is characterized by low, long-wavelength (approximately 40 to 50 m) ripples that are visible in bathymetric imagery and as depicted by 1-m contours; shell deposits are present in ripple troughs. Because this rippled, fine-grained sand substrate is bounded upslope to the east by the rippled, coarse-grained sand of substrate A1 (which appears to override it from the east) and downslope to the west by rippled, coarse-grained sand of substrate K; and because substrate H has an irregular southwestern edge where it abuts substrate K; it is likely that substrate H represents a fine-grained sand sheet that has moved downslope and overridden the upslope part of K. Substrate H now separates two coarse-grained sand substrates (A1 and K). This suggests that the long-wavelength ripples that form the surface of substrate H are relict and that the substrate may not be mobile at present. The timing of these postulated mass movements is not known. Part of substrate H is bounded downslope to the west by substrate L, which it resembles in the ratio of fine- to coarse-grained sand content, but H contains less mud L. Some stations that occur in the area occupied by substrate H represent deposits of substrate A1 that are not mappable at the present scale and are shown by a symbol and the number 0. |
| I i_fgcgS | Immobile, fine- and coarse-grained sand. Substrate I is an immobile fine- and coarse-grained sand deposit. It forms a hummocky surface on the lower western flank of Stellwagen Bank. Water depth range of the stations is 44 to 71 m and of the mapped substrate 40 to 75 m. Mean weight percents of aggregates and composite grades: mud, 7; sand, 92 (fgS, 42; cgS, 49); gravel, 1 (G1, 1; G2, <1). It is bounded to the east in shallower water by substrate A1, to the south by substrates H and L, to the north by substrate L, and to the west by substrate R. Substrate I is similar in grain-size content to the upper layer of substrate J, which it surrounds. The hummocky surface of substrate I is visible in multibeam topographic imagery and as depicted by 1-m contours, and its digitated southwestern margin is similar to the topography of the adjacent western margin of substrate A1. These features suggest that substrate I represents an older coarse-grained sand sheet (not unlike A1) now overlain by a thin layer of fine-grained sand not unlike adjacent substrates H and L. |
| J r_cgfgS / i_pcbG | Rippled, coarse- and fine-grained sand; partial veneer on immobile pebble, cobble, boulder gravel. Substrate J is a layered substrate of mobile, coarse- and fine-grained sand that partially covers immobile pebble, cobble, boulder gravel in a depression surrounded by substrate I on the lower western flank of Stellwagen Bank. Water depth range of the stations is 48 to 55 m and of the mapped substrate 46 to 59. Mean weight percents of aggregates and composite grades of the sediment partial veneer overlying gravel: mud, 4; sand, 92 (fgS, 47; cgS, 45); gravel, 4 (G1, 2; G2, 2). Substrate J lies in an area of multibeam high backscatter values centered on ~42 degrees 15.5 minutes North and ~70 degrees 19.6 minutes West. The upper layer of substrate J is similar to substrate I in mud, sand, and gravel content. |
| K r_cgS | Rippled, coarse-grained sand. Substrate K is a mobile, coarse-grained sand deposit that lies on the lower flank of Stellwagen Bank southeast of the eastern end of Southwestern Spur. Water depth range of the stations is 42 to 50 m and of the mapped substrate 40 to 50 m. Mean weight percents of aggregates and composite grades: mud, 1; sand, 98; (fgS, 24; cgS, 75); gravel, less than 1 (G1, <1; G2, 0). Substrate K is dominantly coarse-grained sand and is low in mud, but it contains an appreciable amount of fine-grained sand (3 phi sand is more abundant than 4 phi sand). It is texturally equivalent to substrate A3. To the northeast and east, substrate K is bounded by substrate H, whose digitated boundary, based on multibeam topographic imagery, suggests it has encroached upon substrate K during a mass movement event. To the west, in deeper water, substrate K is bounded by substrate L. Thus, substrate K, a coarse-grained sand, lies between fine-grained sand substrates H and L, indicating that K was not deposited by present-day sedimentary transport processes, and its depositional history is unclear. |
| L i_mfgS | Immobile, muddy, fine-grained sand. Substrate L is an immobile, muddy, fine-grained sand deposit that is present in three areas on the lowermost western flank of Stellwagen Bank and on the eastern part of Western Spur. Water depth range of the stations is 50 to 77 m and of the mapped substrate 44 to 77m. Mean weight percents of aggregates and composite grades: mud, 10; sand, 89 (fgS 73; cgS, 17); gravel, 1 (G1, 1; G2, 0). It lies in a region where mud content (range 2-33 weight percent) increases with increase in water depth from bank to basin. Substrate L in quadrangle 5 is texturally equivalent to substrate G1 that occurs off the eastern flank of Stellwagen Bank in quadrangle 6 (Valentine and Gallea, 2015), but substrate G1 lies in much deeper water (85-171 m). Some stations that occur in the areas occupied by substrate L represent substrates that are not mappable at the present scale and are represented on maps by a symbol. See Valentine and Cross, 2024 for additional description of this unit. |
| M i_mcgS / pcbG | Immobile, muddy, coarse-grained sand; partial veneer on pebble, cobble, boulder gravel. Substrate M is a layered substrate of immobile, muddy, coarse-grained sand that partially covers pebble, cobble, boulder gravel. It forms the hummocky surface of the western part of Western Spur, a westward extension of Stellwagen Bank into Stellwagen Basin. Water depth range of the stations is 59 to 68 m and of the mapped substrate 56 to 69 m. Mean weight percents of aggregates and composite grades of the sediment partial veneer overlying gravel: mud, 22; sand, 73 (fgS, 13; cgS, 60); gravel, 5 (G1, 4; G2, 1). The upper layer of substrate M is dominantly coarse-grained sand with less fine-grained sand (3 phi sand is greater than 4 phi sand) and mud. The irregular surface of the substrate indicates the presence of partially-buried gravel features that are visible in multibeam topographic imagery and as depicted by 1-m contours. The upper layer of substrate M resembles somewhat the upper layer of substrate Q, which forms the hummocky surface of Southwestern Spur to the south. The upper layer of substrate Q has a similar mud content (24 weight percent), but unlike substrate M, it is a muddy, fine-grained sand. Substrate M is bounded in shallower water to the east by substrate L (mud content 10 weight percent) and in deeper water to the west by substrate T (mud content 34 weight percent) on the flank of Western Spur. |
| N i_mcgS | Immobile, muddy, coarse-grained sand. Substrate N is an immobile, muddy, coarse-grained sand deposit that is associated with substrates L and O in an area of hummocky topography east of the scarp that separates the base of Stellwagen Bank from Stellwagen Basin. Water depth range of the stations is 58 to 65 m. Grain-size analyses of all samples identified as N were used to calculate the mean weight percents of aggregates and composite grades: mud, 11; sand, 73 (fgS, 10; cgS, 63); gravel, 15 (G1, 10; G2, 5). See the description of substrate L with which both substrates N and O are associated. Stations identified as deposits of substrate N occur in the area occupied by substrate L, but they are not mappable as a coherent unit at the present scale so not present as a separate polygon. |
| O i_mfgcgS | Immobile, muddy, fine- and coarse-grained sand. Substrate O is an immobile, muddy, fine- and coarse-grained sand deposit that is associated with substrates L and N in an area of hummocky topography east of the scarp that separates the base of Stellwagen Bank from Stellwagen Basin. Water depth range of the stations is 55 to 64 m. Grain-size analyses of all samples identified as O were used to calculate the mean weight percents of aggregates and composite grades: mud, 15; sand, 82 (fgS, 41; cgS, 41); gravel, 4 (G1, 4; G2, 0). Substrate O likely is a mixture of substrates L and N. See the description of substrate L with which both substrates N and O are associated. Stations identified as deposits of substrate O occur in the area occupied by substrate L, but they are not mappable as a coherent unit at the present scale so not present as a separate polygon. |
| P i_mfgS | Immobile, muddy, fine-grained sand. Substrate P is an immobile, muddy, fine-grained sand deposit that lies at the base of Stellwagen Bank in two areas of Stellwagen Basin, north and south of Southwestern Spur. Water depth range of the stations and the mapped substrate is 59 to 69 m. Mean weight percents of aggregates and composite grades: mud, 29; sand, 69 (fgS, 60; cgS, 10); gravel, 1 (G1, 1; G2, <1). The two areas of substrate P are separated by substrate Q, a layered, muddy, fine-grained sand that partially covers pebble, cobble, and boulder gravel on Southwestern Spur. Substrate P (mud content 29 weight percent) is very similar texturally to the upper layer of substrate Q (mud content 24 weight percent). Although mud content of both is almost equal, and both are dominated by fine-grained sand, the upper layer of Q overlies gravel and contains more coarse-grained sand than P. Substrate P has a greater mud content than substrate L (10 weight percent) that lies in shallower water to the east but much less than substrate R (58 weight percent) that lies in deeper water to the west. As mud content increases westward from substrates L to P to R (from the base of the bank into the basin), fine-grained sand content decreases, especially the 3-phi sand. The somewhat hummocky surface of substrate P, as observed in multibeam topographic imagery, where it borders Southwestern Spur indicates the presence of buried gravel features that are exposed in substrate Q on the spur. |
| Q i_mfgS / pcbG | Immobile, muddy, fine-grained sand; partial veneer on pebble, cobble, boulder gravel. Substrate Q is a layered substrate of immobile, muddy, fine-grained sand that partially covers pebble, cobble, boulder gravel. It forms the hummocky surface of Southwestern Spur, an elongate feature that extends northwestward into Stellwagen Basin from the lower southwestern flank of Stellwagen Bank. Water depth range of the stations is 54 to 73 m and the substrate 49 to 81 m. Mean weight percents of aggregates and composite grades of the sediment partial veneer overlying gravel: mud, 24; sand, 69 (fgS, 42; cgS, 26); gravel, 7 (G1, 4; G2, 3). The deeper parts of substrate Q in the west are bounded by mud substrates S (mud content 94 weight percent) and R (mud content 58 weight percent), while the shallower parts in the east are bounded by substrates L (mud content 10 weight percent) and P (mud content 29 weight percent). The upper layer of substrate Q is dominantly fine-grained sand (3 phi sand is greater than 4 phi sand); mud and coarse-grained sand are present in equal amounts. The irregular surface of boulder ridges and of partly-buried gravel features is visible in multibeam topographic imagery and as depicted by 1-m contours. |
| R i_fgsM | Immobile, fine-grained sandy mud. Substrate R is an immobile, fine-grained sandy mud deposit that occupies two areas in Stellwagen Basin: one adjacent to the southern margin of Southwestern Spur, and the other along the base of the western flank of Stellwagen. Water depth range of the stations is 71 to 88 m and the mapped substrate 67 to 88 m. Substrate R is equivalent to the upper layer of substrate V, which it surrounds. Mean weight percents of aggregates and composite grades of the fine-grained sandy mud: mud, 58; sand, 42 (fgS, 38; cgS, 3); gravel, less than 1 (G1, <1; G2, 0). Substrate R is bounded by sand substrates with lower mud content (I, L, P, and Q) that lie in shallower water on the lower western flank of Stellwagen Bank and on the flanks of Southwestern Spur and Western Spur. It is bounded in a deeper part of Stellwagen Basin by substrate S with a higher mud content. Substrate R is characterized by the presence of fish and crab burrows. |
| S i_M | Immobile mud. Substrate S is an immobile mud deposit that occupies much of Stellwagen Basin. Water depth range of the stations is 82 to 103 m and the mapped substrate 82 to 105 m. Mean weight percents of aggregates and composite grades: mud, 94; sand, 6 (fgS, 5; cgS 1); gravel, 0. Substrate S is bounded to the east along the basin margin by substrate R (mud content 58 weight percent). Elsewhere, substrate S is bounded to the south by substrate Q (upper layer mud content 24 weight percent) on Southwestern Spur, and to the north by substrate T (upper layer mud content 34 weight percent) on the flanks of Fifteen Bank and Western Spur. Substrate S is characterized by the presence of fish and crab burrows. |
| T i_mcgS / pcbG | Immobile, muddy, coarse-grained sand; partial veneer on pebble, cobble, boulder gravel. Substrate T is a layered substrate of immobile, muddy, coarse-grained sand that partially covers pebble, cobble, boulder gravel. It forms a somewhat hummocky seabed on the top and flanks of Fifteen Bank and on the westward-facing flank of the adjacent Western Spur. Water depth range of the stations and the mapped substrate is 70 to 103 m. Mean weight percents of aggregates and composite grades of the sediment partial veneer overlying gravel: mud, 34; sand, 52 (fgS, 14; cgS, 37); gravel, 14 (G1, 10; G2, 4). The substrate resembles substrate M, but substrate T has a somewhat higher mud content. |
| U i_pcG | Immobile, pebble, cobble gravel. Substrate U is an immobile, gravel pavement. Video imagery revealed it to be closely-packed pebbles and cobbles with little or no sand veneer that lies on the Western Edge of Stellwagen Bank. Water depth of the single station is 62 m. Weight percents of aggregates and composite grades collected from this station: mud, 10; sand, 44 (fgS, 11; cgS, 33); gravel, 46 (G1, 10; G2, 36). The sample is a mixture of the gravel pavement that forms the seabed (cobbles were observed but not collected) and the underlying sandy sediment. Based on multibeam topographic and backscatter imagery, the substrate extends northward along the Western Edge into the southern part of quadrangle 8. A station identified as a deposit of substrate U (1646, 35 m) in the area occupied by substrate A1 is not mappable as a coherent unit at the present scale; it lies in an area of high backscatter values centered on ~42 degrees 19.3 minutes North and ~70 degrees 18.6 minutes West that likely represents a gravel pavement. |
| V i_fgsM / cbG | Immobile, fine-grained sandy mud; partial veneer on cobble, boulder gravel. Substrate V is a layered substrate of immobile, fine-grained sandy mud that partially covers cobble, boulder gravel that is surrounded by substrate R in two areas in Stellwagen Basin. Water depth range of the stations and the mapped substrate is 72 to 82 m. The upper layer of substrate V is texturally equivalent to substrate R. Mean weight percents of aggregates and composite grades of the sediment partial veneer overlying gravel: mud, 68; sand, 32 (fgS, 30; cgS, 2); gravel, 0 (G1, 0; G2, 0). The underlying cobbles and boulders represent the tops of almost-buried mounds of gravel that produce a hummocky surface that is visible in multibeam topographic imagery and as depicted by 1-m contours. The cobbles and boulders are exposed in depressions that are interpreted to be formed by the scouring activities of large fish observed to occupy them in video imagery. |
| W r_cgS / i_scM | Rippled, coarse-grained sand; partial veneer on immobile, semiconsolidated mud. Substrate W is a layered substrate of rippled, coarse-grained sand that partially covers outcrops of semiconsolidated mud that occurs in the area occupied by substrate A1. It was observed at 3 locations on the bank crest in quadrangle 5. Water depth range of the stations is 31 to 35 m. Grain-size analyses of all samples identified as W were used to calculate the mean weight percents of aggregates and composite grades of the sediment partial veneer overlying semiconsolidated mud: mud, less than 1; sand, 88 (fgS, 10; cgS, 78); gravel, 12 (G1, 11; G2, 1). Visual analysis of video imagery revealed the lower substrate to be an irregular, burrowed and fragment-strewn surface. It is interpreted to represent an outcrop of semiconsolidated mud that has been burrowed by benthic organisms. The rippled, coarse-grained sand partial upper layer was collected without disturbing the lower clay layer and is texturally very similar to substrates A1 and A3. Stations identified as deposits of substrate W in the area occupied by substrate A1 are not mappable as a coherent unit at the present scale so not present as a separate polygon. |
| Value | Definition |
|---|---|
| boulder ridges <1 meter in height | Ridges less than 1 meter in height equivalent to substrate C. |
| boulder ridges >=1 meter in height | Ridges greater than or =1 meter in height equivalent to substrate C. |
| immobile sediment | Sand (substrate I), muddy sand (substrates L, N, O and P), sandy mud (substrate R), mud (substrate S), muddy sand partial veneer on gravel (substrates M, Q, and T), sandy mud partial veneer on gravel (substrate V), and gravel pavement (substrate U) |
| mobile and immobile sediment | Rippled sand partial veneer on immobile pebble, cobble and boulder gravel (substrates B and J), and rippled sand partial veneer on immobile semiconsolidated mud (substrate W) |
| mobile sediment | Rippled sand; equivalent to substrates A1, A3, H, and K. |
| Value | Definition |
|---|---|
| boulder ridges <1 meter in height | Boulder ridges <1 meter in height equivalent to substrate C. |
| boulder ridges >=1 meter in height | Boulder ridges >=1 meter in height equivalent to substrate C. |
| dominated by coarse-grained sand in the sand fraction | Coarse-grained sand and muddy coarse-grained sand in which coarse-grained sand (0, 1, and 2 phi combined) constitutes the largest portion of the sand fraction; equivalent to substrates A1, A3, B, K, M, N, T and W. |
| dominated by fine-grained sand in the sand fraction | Fine-grained sand, muddy fine-grained sand, and fine-grained sandy mud in which fine-grained sand (3 and 4 phi combined) constitutes the largest portion of the sand fraction; equivalent to substrates H, L, P, Q, R and V. |
| dominated by mud with a low weight percent sand | Sediment which is 94 weight percent mud (>4 phi), 5 percent fine-grained sand, and 1 percent coarse-grained sand; equivalent to substrate S. |
| gravel pavement | Gravel pavement; equivalent to substrate U. |
| fine- and coarse-grained sand | Sediment in which fine- and coarse-grained sand contents differ by <=7 weight percent; equivalent to substrates I, J, and O. |
| Value | Definition |
|---|---|
| < 1 | Mud content < 1 mean weight percent; equivalent to substrates A1, A3, B and W. |
| 1 to <5 | Mud content 1 to less than 5 mean weight percent; equivalent to substrate I. |
| 5 to <10 | Mud content 5 to less than 10 mean weight percent, equivalent to substrate I. |
| 10 to <20 | Mud content 10 to less than 20 mean weight percent; equivalent to substrates L, N and O. |
| 20 to <50 | Mud content 20 to less than 50 mean weight percent; equivalent to substrates M, P, Q and T. |
| 50 to <90 | Mud content 50 to less than 90 mean weight percent; equivalent to substrates R and V. |
| >90 | Mud content greater than 90 mean weight percent; equivalent to substrate S. |
| boulder ridges <1 meter in height | Boulder ridges were never sampled due to the nature of the ridges, so are not represented by a measured mud weight percent. |
| boulder ridges >=1 meter in height | Boulder ridges were never sampled due to the nature of the ridges, so are not represented by a measured mud weight percent. |
| gravel pavement | Equivalent to substrate U. The mud content is likely part of the mixed sediment underlying the gravel, and therefore the substrate is mapped as a gravel pavement and is not assigned to a mud content category |
| Range of values | |
|---|---|
| Minimum: | 0.001435 |
| Maximum: | 97.424322 |
| Units: | square kilometers |
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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) mud, sand, and gravel weight percents; (2) sand fraction subdivided into a fine-grained sand composite, fgS (3 and 4 phi), and a coarse-grained sand composite, cgS (0, 1, and 2 phi), in weight percents; (3) fine-grained sand fraction subdivided into 3 phi sand and 4 phi sand, in weight percents; (4) weight percent of phi (φ) grain sizes; (5) significant phi grain sizes (≥10 weight percent of the sample); (6) gravel fraction (granules and pebbles only) subdivided into G1 (–1, and –2 phi), and G2 (–3, –4, and –5 phi), in weight percents;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 was an iterative process that took place over a number of years, 2015-2022, primarily 2015-2019. Person who carried out this activity:
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| Access_Constraints | None. |
|---|---|
| Use_Constraints | The interpretation was completed at a map scale of 1:25,000 and may not be appropriate for use at other scales. |
| Data format: | This zip file contains the shapefile, browse graphic, and associated FGDC CSDGM metadata. Additionally, ArcGIS 10.8.1 layer files are included for each variation of the mapping units. in format Shapefile (version ArcGIS 10.8.1) Size: 1 |
|---|---|
| Network links: |
https://www.sciencebase.gov/catalog/file/get/63a09167d34e0de3a1f27731 https://www.sciencebase.gov/catalog/item/63a09167d34e0de3a1f27731 https://doi.org/10.5066/P9W9BN3S |
| Data format: | Web mapping service of the dataset. in format WMS (version 1.3.0) |
|---|---|
| Network links: |
https://www.sciencebase.gov/catalogMaps/mapping/ows/63a09167d34e0de3a1f27731?service=wms&request=getcapabilities&version=1.3.0 https://www.sciencebase.gov/catalog/item/63a09167d34e0de3a1f27731 https://doi.org/10.5066/P9W9BN3S |
| Data format: | Web feature service of the dataset. in format WFS (version 1.0.0) |
|---|---|
| Network links: |
https://www.sciencebase.gov/catalogMaps/mapping/ows/63a09167d34e0de3a1f27731?service=wfs&request=getcapabilities&version=1.0.0 https://www.sciencebase.gov/catalog/item/63a09167d34e0de3a1f27731 https://doi.org/10.5066/P9W9BN3S |
