Geologic Unconsolidated Mineral Substrates with less than 50% cover of Consolidated Mineral Substrate where the Unconsolidated Mineral Substrate surface is greater than or equal to than 5% Gravel (particles 2 millimeters to < 4,096 millimeters in diameter).

Attribute Change (Unit Type change)

Name change

Change in level up (Subclass to Class)

Editorial Change (defintion re-worded)

S

The CMECS Coarse, Mixed, and Fine Unconsolidated Mineral Substrate Classes and subordinate units use Folk (1954) terminology to describe particle sizes of loose mineral substrates as shown in the ternary diagram in Figure 7.2 . Units with bracketed letters, e.g., [G], [(g)sM], correspond to the labeled polygons in Figure 7.2, using conventions from Folk (1954).

Getting Started - If Gravel particles make up > 80% of the substrate, continue classifying using the Gravel Substrate subclass units. - If Gravel particles make up greater than or equal to 5% but < 80%, continue classifying using the Mixed Gravel subclass units. - If Gravel particles make up 0.01% to < 5% continue classifying using the Trace Gravel subclass within the Fine Unconsolidated Mineral Substrate class.

When classifying Mixes, or when there is a need to identify specific particle sizes beyond the Subgroup definitions, the Subgroup terms for the Gravel Group (Boulder, Cobble, Pebble, Granule), Sand Group (Very Coarse Sand, Coarse Sand, Medium Sand, Fine, Sand, Very Fine Sand), and Mud Group (Silt, Silt-Clay, Clay) may optionally be substituted for the Group term. Examples: Muddy Sandy Gravel -> Silty Sandy Gravel, Slightly Gravelly Sandy Mud -> Slightly Gravelly Sandy Clay, Gravelly Muddy Sand -> Gravelly Muddy Coarse Sand, Slightly Gravelly Sand -> Slightly Gravelly Medium Sand

Due to the importance of different particle sizes of Gravel as habitat for many organisms, Gravel subgroup particle sizes (Boulder, Cobble, Pebble, Granule) must be identified whenever particle sizes are known or can be estimated within any mix and at any level of classification. Examples: Gravel Mixes -> Pebble Mixes, Muddy Sandy Gravel -> Muddy Sandy Cobble, Gravelly Sand -> Bouldery Sand

See also: implementation guidance for all Substrate Component units

When classifying mixes of two different Gravel Subgroup particle sizes, use combinations of the Subgroup unit names with the overall dominant size first. Examples: Boulder-Cobble, Cobble-Boulder, Cobble-Granule, Pebble-Granule, Granule-Boulder.

Depending on the sampling method used and scale of the observational unit, classifying larger features may require extrapolating information from surrounding observations or additional studies. The Geoform Component may also be used to extend the substrate classification for such features (p. 227, FGDC-STD-018-2012).

Coarse Unconsolidated Mineral Substrate

cmecs:CMECS_00000167

Coarse Unconsolidated Mineral Substrate

Anthropogenic Impact, aRPD and RPD Depth, Benthic Depth Zones, Co-Occurring Elements, Coral Reef Zone, Energy Intensity, Induration, Percent Cover (Fine), Mineral Precipitate, Percent Cover (Coarse), Seafloor Rugosity, Small-Scale Slope, Substrate Descriptor, Substrate Layering, Surface Pattern, Temporal Persistence

1.3

Derived Unit

CMECS Substrate Component: Class