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| Range of values | |
|---|---|
| Minimum: | 0 |
| Maximum: | 14 |
| Range of values | |
|---|---|
| Minimum: | 1 |
| Maximum: | 16 |
| Value | Definition |
|---|---|
| A1 | Abbreviated symbol for A1 r_cgS where r = rippled, cgS = coarse-grained sand |
| 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 |
| K | Abbreviated symbol for K r_cgS where r = rippled, cgS = coarse-grained sand |
| L | Abbreviated symbol for L i_mfgS where i = immobile, m = muddy, fgS = fine-grained sand |
| P | Abbreviated symbol for P i_mfgS where i = immobile, m = muddy, fgS = fine-grained sand |
| R | Abbreviated symbol for R i_fgsM where i = immobile, fgS = fine-grained sand, M = mud |
| X | Abbreviated symbol for X i_fgS where i = immobile, fgS = fine-grained sand |
| Y | Abbreviated symbol for Y r_cgS where r = rippled, cgS = coarse-grained sand |
| Z | Abbreviated symbol for Z r_cgS where r = rippled, cgS = coarse-grained sand |
| AA | Abbreviated symbol for AA r_gcgS / i_pcG where r = rippled, g = gravelly, cgS = coarse-grained sand, / = overlying, or partial veneer over, i = immobile, p = pebble, c = cobble, G = gravel |
| AB | Abbreviated symbol for AB r_fgS where r = rippled, fgS = fine-grained sand |
| AC | Abbreviated symbol for AC r_cgS r = rippled, cgS = coarse-grained sand |
| AG | Abbreviated symbol for AG r_cgS where r = rippled, cgS = coarse-grained sand |
| Value | Definition |
|---|---|
| A1 r_cgS | Rippled, coarse-grained sand. Substrate A1 is a mobile, coarse-grained sand deposit that covers the southwestern part of Stellwagen Bank. Water depth range of the stations is 19 to 48 m and of the mapped substrate 19 to 55 m. A1 reaches its deepest depths of 55 m along the base of the slope below the bank's Southwest Corner. Mean weight percents of aggregates and composite grades: mud, <1; sand, 97 (fgS, 2; cgS, 95); gravel, 3 (G1, 3; G2, <1). Substrate A1 extends northward onto the crest and western flank of Stellwagen Bank in quadrangle 5 (fig. 1; Valentine and Cross, 2024), onto the eastern flank of the bank in quadrangle 6 (Valentine and Gallea, 2015), and onto the southeastern flank of the bank in quadrangle 3. The substrate 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 biological disturbance and flattened by bottom-tending fishing gear. Some samples of substrate A1 occur within the area occupied by substrate AA and are not mappable at the present scale and are represented on maps by a symbol (Map D Sheet 1, Valentine and Cross, 2024). 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 (16 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. Substrate A3 samples occur within the area occupied by substrate A1 and are not mappable as a coherent unit at the present scale and are represented on maps by a symbol (Map D Sheet 1, Valentine and Cross, 2024). Substrate A1 is similar texturally to substrate Z, also a rippled, coarse-grained sand; but they are separated geographically, as substrate Z lies south of Stellwagen Bank in deeper water depths in Race Point Channel. |
| A3 r_cgS | This is not mappable as a separate polygon but included because of references to the unit elsewhere in the document. Rippled, coarse-grained sand. Substrate A3 is a collection of mobile, coarse-grained sand deposits that lie chiefly on the southwestern part of Stellwagen Bank within the area occupied by substrate A1. Water depth range of stations is 19 to 59 m. Mean weight percents of aggregates and composite grades: mud, 1; sand, 99 (fgS, 16; cgS, 82); gravel, <1 (G1, <1; G2 0). Substrate A3 is also present within the area of substrate A1 on the crest and western flank of the bank in quadrangle 5 to the north (fig. 1; Valentine and Cross, 2024) and on the southeastern flank of the bank in quadrangle 3. Substrate A3 is similar to substrate A1 in being a rippled, coarse-grained sand and having a very low mud content. It differs from A1 in that samples of A3 generally contain 10 weight percent or more of fine-grained sand, 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 (fig. 1; Valentine and Gallea, 2015). They both contain more fine-grained sand than substrate A1, but A2 has less fine-grained sand than A3 and is immobile, and it lies at deeper water depths (53-77 m). As is the case in quadrangle 5 to the north, in quadrangle 2 substrate A3 is texturally equivalent to substrate K, but it is geographically separated from it by substrate H. The scattered deposits of substrate A3 in quadrangle 2 are not mappable as a coherent unit at the present scale. The locations of A3 sediment samples in areas occupied by substrates A1, AA, and AB not mappable as a coherent unit at the present scale and are represented on maps by a symbol (Map D Sheet 1, Valentine and Cross, 2024). |
| C i_cbG | Immobile, cobble, boulder gravel. Substrate C is a boulder ridge whose gravelly base is partially covered by a layer of rippled, coarse-grained sand. It occupies 0.4 km2 or 0.2 percent of quadrangle 2. This feature lies in the middle of Race Point Channel and is interpreted to be a boulder ridge based on multibeam topographic imagery. Water depth of the two stations is 58 m and of the mapped substrate 55 to <60 m. Weight percents of aggregates and composite grades of the single sample of sediment partial veneer overlying gravel at the base of the boulder ridge: mud, 1; sand, 88; (fgS, 15; cgS, 73); gravel, 10 (G1, 10; G2, 0). Substrate C is a linear feature oriented east-west; its eastern part is bounded by substrate Z and its western part by substrate Y. |
| H r_fgS | Rippled, fine-grained sand. Substrate H is a mobile, fine-grained sand deposit that lies on the southwestern flank of Stellwagen Bank. Water depth range of the stations is 39 to 42 m and of the mapped substrate 37 to 42 m. Mean weight percents of aggregates and composite grades: mud, 1; sand, 99 (fgS, 89; cgS, 10); gravel, 0 (G1, 0; G2, 0). Substrate H extends northward onto the lower western flank of the bank in quadrangle 5 (fig. 1; Valentine and Cross, 2024). The surface of the substrate is characterized by low, long-wavelength (approximately 40 to 50 m) ripples that are visible in multibeam topographic 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 K; it is likely that substrate H represents a fine-grained sand sheet that has moved downslope to override substrate K and now separates two coarse-grained sand substrates (A1 and K). This suggests that the long-wavelength ripples of the surface of substrate H are relict and that the substrate may or may not be mobile at present. The timing of such a mass movement event or events is not known. Substrate H texturally resembles substrate L, an immobile, muddy, fine-grained sand (which lies below substrate K on the western flank of the bank) in the ratio of fine- to coarse-grained sand content but substrate H contains less mud. |
| K r_cgS | Rippled, coarse-grained sand. Substrate K is a mobile, coarse-grained sand deposit that lies on the southwestern flank of Stellwagen Bank, northwest of its Southwest Corner. Water depth range of the stations is 41 to 56 m and of the mapped substrate 40 to 56 m. Mean weight percents of aggregates and composite grades: mud, 1; sand, 99; (fgS, 19; cgS, 80); gravel, 0 (G1, 0; G2, 0). Substrate K extends northward into quadrangle 5 (fig. 1; Valentine and Cross, 2024) onto the lower western flank of Stellwagen Bank near the eastern end of Southwestern Spur. The substrate is dominantly coarse-grained sand and is low in mud, but it contains an appreciable amount of fine-grained sand (and 3 phi sand is more abundant than 4 phi sand). As is the case in quadrangle 5 to the north, substrate K is texturally equivalent to substrate A3, which is represented by scattered deposits within the area occupied by substrate A1. To the east, upslope in shallower water, substrate K is bounded by the rippled, fine-grained sand of substrate H (which multibeam topographic imagery suggests has encroached upon substrate K) and by the rippled coarse-grained sand of substrate A1. To the west, in deeper water, substrate K is bounded by the immobile, muddy, fine-grained sands of substrates L and P. Thus, substrate K, a coarse-grained sand, lies between finer-grained substrates H (upslope) and L and P (downslope) indicating that K was not deposited by present-day sedimentary transport processes; its depositional history is unclear. Substrate K is bounded to the south by substrate X, an immobile, fine-grained sand that lies in a small valley that incises the bank adjacent to its Southwest Corner. |
| L i_mfgS | Immobile, muddy, fine-grained sand. Substrate L is an immobile, muddy, fine-grained sand deposit that lies on the lower, western flank of Stellwagen Bank. Water depth range of the stations is 50 to 58 m and of the mapped substrate 49 to 58 m. Mean weight percents of aggregates and composite grades: mud, 9; sand, 90 (fgS 75; cgS, 15); gravel, 0 (G1, 0; G2, 0). Substrate L extends northward into quadrangle 5 (fig. 1; Valentine and Cross, 2024) onto the lower western flank of Stellwagen Bank. It lies between substrate K (upslope; mud content 1 wt pct) and substrate P (downslope; mud 23 wt pct) in a region where mud content increases with increasing water depth from bank to basin. Note that substrate L is identified as a muddy, fine-grained sand even though the threshold of ≥10 wt pct mud is not met (Valentine, 2019). Justification for this is that substrate L extends northward into quadrangle 5 from quadrangle 2, where the mud criterion is met. As in quadrangle 5, substrate L in quadrangle 2 is texturally different from its bounding substrates K and P in mud, coarse-grained sand, 3-phi sand and 4-phi sand content, in topographic position, and in water depth. Substrate L in quadrangle 2 is texturally equivalent to substrate G1 that occurs off the eastern flank of Stellwagen Bank in quadrangle 6 (fig. 1; Valentine and Gallea, 2015) in much deeper water (85-171 m). Substrate L is similar texturally to substrates X and AB. |
| P i_mfgS | Immobile, muddy, fine-grained sand. Substrate P is an immobile, muddy, fine-grained sand deposit that lies in Stellwagen Basin and bounds the southwestern part of Stellwagen Bank; it extends into adjacent Little Stellwagen Basin at the western approach to Race Point Channel. Water depth range of the stations and the mapped substrate is 51 to 68. Mean weight percents of aggregates and composite grades: mud, 23; sand, 76 (fgS, 68; cgS, 8); gravel, <1 (G1, <1; G2, 0). Substrate P extends into quadrangle 5 to the north where it also lies in Stellwagen Basin (fig. 1; Valentine and Cross, 2024). In quadrangle 2, substrate P abuts several texturally varied substrates to the east along the topographic transition from Stellwagen Bank into Stellwagen Basin and Little Stellwagen Basin. These substrates, from north to south, are muddy, fine-grained sand (L), coarse-grained sand (K), fine-grained sand (X), coarse-grained sand, (A), fine-grained sand (AB), and coarse-grained sand (Y). To the west, in somewhat deeper water, lies the fine-grained sandy mud (substrate R) of Stellwagen Basin. |
| R i_fgsM | Immobile, fine-grained sandy mud. Substrate R is an immobile, fine-grained sandy mud deposit that occupies Stellwagen Basin in the southwestern part of quadrangle 2. Water depth range of the stations and the mapped substrate is 60 to 64 m. Mean weight percents of aggregates and composite grades: mud, 68; sand, 32 (fgS, 29; cgS, 3); gravel, <1 (G1, <1; G2, 0). Substrate R also is present in quadrangle 5 to the north (Valentine and Cross, 2024). It is bounded to the east by substrate P, a muddy, fine-grained sand with a lower mud content (23 wt pct). Substrate R is characterized by the presence of fish and crab burrows. |
| X i_fgS | Immobile, fine-grained sand. Substrate X is an immobile, fine-grained sand deposit that occupies a small valley located on the western flank of the bank’s southwest corner. Water depth range of the stations and the mapped substrate is 44 to 55 m. Mean weight percents of aggregates and composite grades: mud, 5; sand, 95 (fgS, 82; cgS, 13); gravel, <1 (G1, <1; G2, 0). It is bounded to the north by the rippled, coarse-grained sand of substrate K; and to the east at shallower depths by the rippled coarse-grained sand of substrate A1. Substrate X is bounded to the southwest at deeper depths by the muddy, fine-grained sand of substrate P in Stellwagen Basin. Substrate X is texturally similar to two other substrates (L, AB). They are separated geographically, but they all lie on the flank of Stellwagen Bank. Substrate L is a muddy, fine-grained sand (49-58 m) that is present north of substrate X on the western flank of the bank; substrate AB is a fine-grained sand (44-63 m) that is present on the southern flank of the bank facing Race Point Channel. |
| Y r_cgS | Rippled, coarse-grained sand. Substrate Y is a mobile, coarse-grained sand deposit lying in the western part of Race Point Channel between Stellwagen Bank to the north and Cape Cod to the south. Water depth range of the stations and mapped substrate is 54 to 64 m. Mean weight percents of aggregates and composite grades: mud, 4; sand, 95; (fgS, 36; cgS, 59); gravel, 1 (G1, 1; G2, 0). The northern part of substrate Y lies at somewhat shallower depths (≤60 m) than the southern part (>60 m). Substrate Y is bounded by the fine-grained sand of substrate AB to the north and coarse-grained sand of substrate Z to the east. To the west it abuts the muddy, fine-grained sand of substrate P in Stellwagen Basin and Little Stellwagen Basin. Substrate AC, interpreted to be an east-west aligned gravel ridge, extends westward from substrate Z into the area occupied by substrate Y. |
| Z r_cgS | Rippled, coarse-grained sand. Substrate Z is a mobile, coarse-grained sand deposit lying in Race Point Channel between Stellwagen Bank to the north and Cape Cod to the south. Water depth range of the stations is 51 to 56 m and of the mapped substrate 50 to 60 m. Mean weight percents of aggregates and composite grades: mud, 2; sand, 98; (fgS, 9; cgS, 89); gravel, 1 (G1, 1; G2, <1). Substrate Z is bounded to the north by mobile, fine-grained sand substrate AB, to the west and south by rippled, coarse-grained sand substrate Y, and to the east it extends out of the mapped area into quadrangle 3. Although substrates Y and Z both are coarse-grained sands, substrate Z lies at somewhat shallower depths and has a higher coarse-grained sand content (89 wt pct) than Y (59 wt pct), which lies at somewhat deeper depths near the western entrance of Race Point Channel. |
| AA r_gcgS / i_pcG | Rippled, gravelly, coarse-grained sand; partial veneer on immobile, pebble, cobble gravel. Substrate AA is a layered substrate of mobile sand that partially covers immobile, pebble, cobble gravel on the southwestern part of Stellwagen Bank, north of its Southwest Corner. Water depth range of the stations and mapped substrate is 27 to 35 m. Mean weight percents of aggregates and composite grades of the sediment partial veneer overlying gravel: mud, <1; sand, 55; (fgS, 6; cgS, 49); gravel, 45 (G1, 16; G2, 29). Substrate AA is surrounded by substrate A1. The area occupied by substrate AA includes deposits of substrates A1 and A3 as bedforms that are flattened by fishery trawling and dredging and subsequently reformed by storm currents; so that at times the seabed is gravel partially covered by sand and represents substrate AA, and at other times the seabed is totally covered by sand and represents substrates A1 and A3. The locations of A1 and A3 sediment samples in areas occupied by substrate AA are not mappable at the present scale and are represented on maps by a symbol (Map D Sheet 1, Valentine and Cross, 2024). |
| AB r_fgS | Rippled, fine-grained sand. Substrate AB is a mobile, fine-grained sand deposit that lies on the southern flank of Stellwagen Bank in the northern part of Race Point Channel. Water depth range of the stations and the mapped substrate is 44 to 63 m. Mean weight percents of aggregates and composite grades: mud, 4; sand, 96 (fgS, 71; cgS, 25); gravel, <1 (G1, <1; G2, 0). Substrate AB is bounded to the north by the rippled, coarse-grained sand of substrate A1 on Stellwagen Bank; to the south by the rippled, coarse-grained sands of substrates Y and Z in Race Point Channel; and to the west by the immobile, muddy, fine-grained sand of substrate P in Stellwagen Basin. Within the area occupied by substrate AB, deposits of two substrates occur that are represented by too few samples to be mappable as coherent units at the present scale. One of them, substrate AD, is a rippled, coarse-grained sand that overlies a series of nested, arcuate gravel ridges that are observed in multibeam topographic imagery and are interpreted to represent a glacial ice fall deposit at the foot of Stellwagen Bank. The other, substrate AE, is a rippled, coarse-grained sand that overlies a topographic feature interpreted to be a gravel ridge or moraine that lies south of the southwestern edge of Stellwagen Bank. Substrate AD contains more coarse-grained sand and less fine-grained sand than substrate AE. The locations of AD and AE sediment samples in the area occupied by substrate AB are not mappable at the present scale and are represented on maps by a symbol (Map D Sheet 1, Valentine and Cross, 2024). Substrate AB is similar texturally to substrates L and X. |
| AC r_cgS | Rippled, coarse-grained sand. Substrate AC is a mobile, coarse-grained sand deposit that lies in Race Point Channel in quadrangles 2 and 3. The largest portion of substrate AC lies in quadrangle 3 to the east. It occupies <0.1 km2 or <0.1 percent of quadrangle 2. Water depth of the mapped area in quadrangle 2 is ~60 m. No sediment samples were collected in quadrangle 2. Weight percents of aggregates and composite grades of the one sample from quadrangle 3: mud, 2; sand, 98 (fgS, 12; cgS, 86; gravel, <1 (G1, <1; G2, 0). Substrate AC is interpreted to be a rippled, coarse-grained sand because its surface displays large bedforms observable in multibeam topographic imagery in both quadrangles 2 and 3. They trend NW-SE, approximately normal to the trend of Race Point Channel. Although substrate AC was not sampled in quadrangle 2, it is mapped as extending a short distance into quadrangle 2 from quadrangle 3 based on the presence of its distinctive bedforms. |
| AD r_cgS | This is not mappable as a separate polygon but included because of references to the unit elsewhere in the document. Rippled, coarse-grained sand. Substrate AD is a collection of mobile, coarse-grained sand deposits that lie on several partly-buried, nested, arcuate gravel ridges that are interpreted from multibeam topographic imagery to represent a glacial ice fall deposit at the foot of the southern slope of Stellwagen Bank in the northern part of Race Point Channel. Water depth range of the stations is 44 to 45 m. Mean weight percents of aggregates and composite grades: mud, 1; sand, 92; (fgS, 10; cgS, 82); gravel, 6 (G1, 6; G2, 0). Substrate AD is not mappable as a coherent unit at the present scale. It is represented by 4 stations that lie in the area occupied by substrate AB. Substrate AD is texturally similar to AE, which also is an unmappable substrate lying within the area of substrate AB, but AD has a higher weight percent of coarse-grained sand. The locations of AD sediment samples in the area occupied by substrate AB are not mappable at the present scale and are represented on maps by a symbol (Map D Sheet 1, Valentine and Cross, 2024). |
| AE r_cgS | This is not mappable as a separate polygon but included because of references to the unit elsewhere in the document. Rippled, coarse-grained sand. Substrate AE is a collection of mobile, coarse-grained sand deposits that lie on a partly-buried feature that is interpreted from multibeam topographic imagery to be a gravel ridge or moraine that is located in the northern part of Race Point Channel near the southern margin of Stellwagen Bank. Water depth range of the stations is 49 to 54 m. Mean weight percents of aggregates and composite grades: mud, 3; sand, 95; (fgS, 34; cgS, 61); gravel, 2 (G1, 2; G2, <1). Substrate AE is not mappable as a coherent unit at the present scale. It is represented by 5 stations that lie in the area occupied by substrate AB. Substrate AE is texturally similar to substrate AD but AE has a lower weight percent of coarse-grained sand. The locations of AE sediment samples in the area occupied by substrate AB are not mappable at the present scale and are represented on maps by a symbol (Map D Sheet 1, Valentine and Cross, 2024). |
| AF r_fgS | This is not mappable as a separate polygon but included because of references to the unit elsewhere in the document. Rippled, fine-grained sand. Substrate AF is a collection of mobile, fine-grained sand deposits that lie at the western end of Race Point Channel in Little Stellwagen Basin. Water depth range of the stations is 62 to 64 m. Mean weight percents of aggregates and composite grades: mud, 4; sand, 95 (fgS, 62; cgS, 33); gravel, 1 (G1, 1; G2, 0). Substrate AF is not mappable as a coherent unit at the present scale. It is represented by 5 stations that lie in the area occupied by substrate P, an immobile, muddy, fine-grained sand. The substrate AF samples lie near the boundary of substrate P with substrate Y, a rippled, coarse-grained sand that lies to the east in Race Point Channel. The deposits of AF apparently represent a textural transition area between substrates P and Y. The locations of AF sediment samples in the area occupied by substrate P are not mappable at the present scale and are represented on maps by a symbol (Map D Sheet 1, Valentine and Cross, 2024). |
| AG r_cgS | Rippled, coarse-grained sand. Substrate AG is a mobile, coarse-grained sand deposit that lies on the south flank of Little Stellwagen Basin north of Cape Cod and extends eastward into quadrangle 3. It occupies 0.4 km2 or 0.2 percent of quadrangle 2. It is represented by two stations in quadrangle 2, one in the mapped area and one located nearby to the south in an unmapped area of quadrangle 2. Water depth range of the stations is 55 to 58 m and of the mapped substrate ~55 to ~60 m. Mean weight percents of aggregates and composite grades of two samples collected in quadrangle 2: mud, <1; sand, 100 (fgS, 5; cgS, 95); gravel, 0 (G1, 0; G2 0). The surface of substrate AG is covered with storm-generated sand ripples. The substrate likely extends southward into an unmapped area of shallowing water depths on the northern margin of Cape Cod. Interpretation of multibeam topographic and backscatter imagery indicates that substrate AG is a recognizable feature that extends eastward along the northern slope of Cape Cod into quadrangle 3 where it abuts substrate AQ, a fine-grained sand located in quadrangle 3. |
| AH r_cgS | This is not mappable as a separate polygon but included because of references to the unit elsewhere in the document. Rippled, coarse-grained sand. Substrate AH is a collection of mobile, coarse-grained sand deposits that lie on the south flank of Little Stellwagen Basin. It is represented by two stations. Water depth of the stations is 61 m. Mean weight percents of aggregates and composite grades: mud, <1; sand, 100 (fgS, 16; cgS, 84); gravel, 0 (G1, 0; G2 0). The substrate likely extends southward into an unmapped area in shallowing water depths on the northern margin of Cape Cod. Substrate AH is not mappable as a coherent unit at the present scale. two stations lie in and near the southern part of the area occupied by substrate Y. The surface of AH is covered with storm-generated sand ripples. The substrate has a lower mud content and a higher coarse-grained sand content than substrate Y. Substrate AH is texturally similar to substrate A3, but it is recognized as a separate substrate because it is separated geographically from deposits of A3 by Race Point Channel. The locations of AH sediment samples in the area occupied by substrate Y are not mappable at the present scale and are represented on maps by a symbol (Map D Sheet 1, Valentine and Cross, 2024). |
| Value | Definition |
|---|---|
| boulder ridges >=1 meter in height | Boulder ridges greater than or equal to 1 meter in height equivalent to substrate C. |
| immobile sediment | Fine-grained sand (substrate X), muddy fine-grained sand (substrates L, P), fine-grained sandy mud (substrate R) |
| mobile and immobile sediment | Rippled, gravelly, coarse-grained sand partial veneer on immobile pebble, cobble gravel |
| mobile sediment | Rippled, coarse-grained sand (equivalent to substrates A1, A3, K, Y, Z, AC, AD, AE, AG and AH) and rippled, fine-grained sand (equivalent to substrates H, AB and AF) |
| Value | Definition |
|---|---|
| boulder ridges >=1 meter in height | Boulder ridges greater than or equal to 1 meter in height equivalent to substrate C. |
| dominated by coarse-grained sand in the sand fraction | 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, K, Y, Z, AA, AC, AD, AE, AG, and AH. |
| 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, R, X, AB, and AF. |
| Value | Definition |
|---|---|
| < 1 | Mud content less than 1 mean weight percent; equivalent to substrates A1, AA, AG and AH. |
| 1 to <5 | Mud content 1 to less than 5 mean weight percent; equivalent to substrates A3, H, K, Y, Z, AB, AC, AD, AE, and AF. |
| 5 to <10 | Mud content 5 to less than 10 mean weight percent, equivalent to substrate X. |
| 10 to <20 | Mud content 10 to less than 20 mean weight percent; equivalent to substrate L. |
| 20 to <50 | Mud content 20 to less than 50 mean weight percent; equivalent to substrate P. |
| 50 to <90 | Mud content 50 to less than 90 mean weight percent; equivalent to substrate R. |
| 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; equivalent to substrate C. |
| Range of values | |
|---|---|
| Minimum: | 0.032939 |
| Maximum: | 76.1274 |
| Units: | square kilometers |
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The following information was used as guidelines to derive individual substrate 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 grain sizes; (5) significant phi grain sizes (greater than or equal to 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, 2018-2023, primarily 2022. 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: 0.5 |
|---|---|
| Network links: |
https://www.sciencebase.gov/catalog/file/get/644a7995d34ee8d4adee0435 https://www.sciencebase.gov/catalog/item/644a7995d34ee8d4adee0435 https://doi.org/10.5066/P9UL3LWN |
| Data format: | Web mapping service of the dataset. in format WMS (version 1.3.0) |
|---|---|
| Network links: |
https://www.sciencebase.gov/catalogMaps/mapping/ows/644a7995d34ee8d4adee0435?service=wms&request=getcapabilities&version=1.3.0 https://www.sciencebase.gov/catalog/item/644a7995d34ee8d4adee0435 https://doi.org/10.5066/P9UL3LWN |
| Data format: | Web feature service of the dataset. in format WFS (version 1.0.0) |
|---|---|
| Network links: |
https://www.sciencebase.gov/catalogMaps/mapping/ows/644a7995d34ee8d4adee0435?service=wfs&request=getcapabilities&version=1.0.0 https://www.sciencebase.gov/catalog/item/644a7995d34ee8d4adee0435 https://doi.org/10.5066/P9UL3LWN |
