Surficial Material Terms and Symbols

Definition of Surficial Material Terms

• Applied to landfills, spoil heaps, tailings, and artificial islands; also used to describe excavation areas such as open-pit mines.
  
  
• Applied to archaeological sites such as middens and historical whale rendering sites.

Example:

a historic shelly midden

yAIt

• On-site symbols should be used for anthropogenic sites where the area of disturbance is too small to be mapped.
  
  
• Anthropogenic is not applied to urban areas where development has not modified the in situ material.

• Applied to unconsolidated materials that originate by disintegration of rock and have been moved by gravity. These include local bedrock-derived colluvial mantles, and deposits from specific mass wastage processes (see Subclasses for Mass Movement Processes). In general, these deposits are rubbly to blocky in texture and relatively easily identified (See Figure 5).

Example:

colluvial veneer derived from, and overlying, bedrock

• Colluvial veneers and blankets derived from, and overlying unconsolidated Quaternary sediments are only mapped if they are significantly dissimilar to the underlying material.

Examples:	colluvium derived from bedrock overlying till blanket
	weathered mantle of till overlying unweathered till	Mb

(a)

(b)

Figure 5. (a) Talus cones (map symbol: rCc-R) derived from the steep bedrock outcrops by rapid mass movement and gully processes (map symbol: Rs-R"V) (location of photo: Keremeos). (b) Fine-textured slump deposit (map symbol: zCh) derived from glaciolacustrine silts (location of photo: Spence's Bridge). (c) Angular, bedrock-derived colluvium deposited as a result of rapid mass movement processes in the form of a colluvial fan (map symbol: srCf-R) (location of photo: Port Alice, Vancouver Island).

• Clastic and/or organic deposits resulting from snow avalanches, landslide and rockfall debris, earthflows and debris-flows, are mapped as colluvium. These deposits typically occur as fans, cones, hummocks or irregular topography (Figure 5).

Examples:	talus slope	rCk
	debris-flow fan	mdCf
	slump-earthflow derived from glaciolacustrine silts	zChu

• Colluvium is considered to be a product of an active process unless there is evidence to the contrary. Most mass movement processes tend to be continuous or repetitive over time. Thus, it may be unwise to indicate a process has definitely ceased to occur. The map symbol "C^I" should only be used with great caution.

• Applied only to rock that has been sufficiently weathered so that properties related to its strength are significantly different from those of the equivalent unweathered rock.
  
  
• Applied to weathered bedrock that has not been subject to downslope movement due to gravity. Weathered bedrock may be distinguished from colluvium on gently sloping surfaces by the absence of features that result from downslope movement such as solifluction lobes, stone stripes and boulder streams. Includes blockfield, grus, and saprolite (Figure 6).

Examples:	blockfield	aDb
	thin veneer of weathered shale (in situ)	zDx

• Blockfields too small to be mapped as a terrain polygon may be indicated by an on-site symbol located in Periglacial Features.

Figure 6. Weathering of granodiorite produced this grus-covered area with rounded boulders and tors. If slope processes are not apparent, this terrain is mapped as weathered bedrock (map symbol: sDv). (Location of photo: Okanagan Range, south central British Columbia).

• Includes loess, dunes, veneers and blankets of sand and coarse silt.

Examples:	veneer of sandy silt on a river terrace
	active sand dune	sEAr

• Inactive or active dunes too small to be mapped may be indicated by an on-site symbol in Other Landforms and Features.

Materials transported and deposited by streams and rivers; synonymous with alluvial.

General Description:
Deposits generally consist of gravel and/or sand, and/or silt (and rarely, clay). Gravels are typically rounded and contain interstitial sand. Fluvial sediments are commonly moderately- to well-sorted, and display stratification, although massive, non-sorted fluvial deposits do occur.

Application and Examples:

• Applied to materials associated with floodplains, fluvial terraces and fans, and deltas.
  
  
• Floodplain deposits include channel deposits of relatively coarse gravel with weak to prominent stratification, and flood deposits (overbank sediments and levées) that may cover extensive areas away from the main channel and are composed of relatively finer sediments (commonly silt and sand).

Example:	floodplain consisting of channel gravels

• Fluvial terrace deposits consist of channel deposits that may include some overbank materials.

Example:	an inactive fluvial terrace composed of stratified sand and gravel	sgFt

• Fluvial materials that are likely to be affected by inundation or channel processes are considered to be active. This is indicated by the "active" process qualifier denoted by the superscript "A" (see Activity Qualifiers).

Example:	active floodplain made up of pebble-sized gravel in sands	psFAp

• Fans consisting of interbedded fluvial and colluvial sediments should be mapped as either fluvial "F" or colluvial "C" depending upon which type of material or process appears to be dominant.
  
  
• Deltas are mapped as fluvial materials because most delta surfaces are essentially the result of fluvial processes.

Materials that exhibit clear evidence of having been deposited by glacial meltwater streams either directly in front of, or in contact with, glacier ice.

General Description:
Glaciofluvial materials typically range from non-sorted and non-bedded gravel made up of a wide range of particle sizes, such as that resulting from very rapid aggradation at an ice front, to moderately- to well-sorted, stratified gravel; flow tills may occur in some deposits. Slump structures and/or their equivalent topographic expression, such as hummocky or irregular terrain may be present. These features are indicative of collapse of the material due to melting of supporting ice. Kettles may occur on the surface of these deposits; they result from the melting of buried or partially buried ice.

Application and Examples:

• Applied to materials that make up kettle or pitted outwash, kames and kame terraces, delta kames, eskers, and kame and kettle topography .

Examples:	kettled or pitted sandy gravel outwash plain	sgFGp-H
	eolian veneer of sandy silt overlying a gravel kame terrace

Figure 7. Cross-section through a hummock in kame and kettle topography that shows ice-contact gravels (map symbol: gF^Gh) (note: slump structures and rapid textural variations) and till (map symbol: Mh).

• Outwash deposits, such as plains and terraces, displaying none of the ice-contact features described above (e.g. kettles) may be mapped as glaciofluvial deposits if reconstruction of the geological history indicates a glacial source; otherwise, these deposits are mapped as fluvial material (F).
  
  
• Eskers and kettles too small to be mapped can be indicated by on-site symbols. Other glacial features that may be associated with glaciofluvial deposits and for which on-site symbols are available, are listed in Glacial Features.

Areas of snow and ice where evidence of active glacier movement is present.

Application and Examples:

• Glacier movement is indicated by features such as crevasses, supraglacial moraines, icefalls and ogives.
  
  
• Applied to all types of glaciers and associated permanent snowfields such as cirque glaciers, mountain icefields, and valley and piedmont glaciers.

Examples:	a valley glacier overlain by coarse, angular ablation moraine
	an icefield with nunataks	I//Rs

Sediments that have settled from suspension and underwater gravity flows, such as turbidity currents, in bodies of standing fresh water, or sediments that have accumulated at their margins through the action of waves.

General Description:
Sediments commonly consist of stratified fine sand, silt and/or clay deposited on the lake bed from suspension, or moderately- to well-sorted, stratified sand and coarser materials that are beach and other littoral sediments transported and deposited by wave action.

• Applied to Holocene lake basins that have either drained or infilled, and active or "raised" (inactive) shoreline deposits.

Examples:	drained lake floor	zLp
	modern beach along a lakeshore	sgLAj
	"raised" beach ridge	gLm

• May be applied to intermittently exposed sediments on the floors of seasonal lakes.

Example:

floor of shallow lake periodically inundated

zLAp-U

• Deltas are mapped as either fluvial or glaciofluvial materials.
  
  
• Raised shorelines too small to be mapped can be illustrated by the strandline on-site symbol (listed under Other Landforms and Features).
  
  
• Lacustrine materials of limited extent and overlain by younger surficial materials may be indicated by the on-site stratigraphic symbol. This is particularly useful because of the lacustrine materials' potential effects on slope stability and groundwater movement.

Lacustrine materials deposited in or along the margins of glacial (ice-dammed) lakes; includes sediments that were released by the melting of floating ice.

General Description:
Glaciolacustrine sediments include: 1) lake bed sediments consisting of stratified fine sand, silt and/or clay; they commonly contain ice-rafted stones and lenses of till and/or glaciofluvial material; slump structures and/or their topographic expression, such as hummocky or irregular terrain may be present and are indicative of collapse of the material due to melting of supporting ice; kettles may occur on the surface of these deposits, the result of the melting of buried or partially buried ice, and 2) moderately-sorted to well-sorted, stratified sand and coarser beach sediments transported and deposited by wave action along the margins of glacial lakes.

• Applied to lake sediments that display ice-contact features such as kettles, slump structures, and the inclusion of ice-rafted stones and other materials.

Examples:	Pitted or kettled terrace made up of glaciolacustrine silt	zLGt-H
	Escarpment composed of glaciolacustrine sand overlain by till

Figure 8. Fine-textured glaciolacustrine sediments exposed in a terrace; note the drop stone (arrow) and contorted bedding (map symbol: zLGt) (location of photo: Gold River, Vancouver Island).

• Most lacustrine sediments in British Columbia that lie at elevations above present valley floors were deposited in glacial lakes that have subsequently drained. If reconstruction of the former lake (elevation, extent and outlet location) indicates it was ice-dammed or blocked by other means peculiar to glaciation, the deposits are mapped as glaciolacustrine in origin. Otherwise, the deposit is mapped as lacustrine using the surficial material symbol "L".
  
  
• Relict shoreline deposits may be mapped by the strandline on-site symbol; glaciolacustrine materials of limited extent or overlain by younger surficial materials may be indicated by the on-site stratigraphic symbol listed in Point Observations. This is particularly useful because of the glaciolacustrine materials' potential effects on slope stability and groundwater movement. Other glacial features which may be associated with glaciolacustrine deposits and for which on-site symbols are available, are listed in List of On-Site Symbols.

Material deposited directly by glacier ice without modification by any other agent of transportation.

General Description:
Morainal material can be transported beneath, beside, on, within and in front of a glacier. The mineralogical, textural, structural and topographic characteristics of till deposits are highly variable and depend upon both the source of material incorporated by the glacier and the mode of deposition. In general, till consists of well-compacted to non-compacted material that is non-stratified and contains a heterogeneous mixture of particle sizes, often in a matrix of sand, silt and clay.

Application and Examples:

• Applied to all varieties of till, including basal till (ground moraine), lateral and terminal moraines, moraines of cirque glaciers, hummocky ice-disintegration moraine, Neoglacial (recent) moraines, and pre-existing unconsolidated sediments reworked by a glacier so that their original character (not necessarily texture) is largely or completely destroyed (See Figure 9).

Examples:	rolling till plain	mdMm
	moraine at terminus of modern glacier	xMAr
	hummocky ice-disintegration moraine	zsgMh

Figure 9. Bedrock slope mantled by till that is of uniform thickness greater than 1 metre (map symbol: Mb) and cross-section of a basal till (inset) illustrating a typical till texture made up of rock fragments of many sizes and shapes in a matrix of sand, silt and clay (location of photo: Ashnola River Valley).

• On-site symbols are available for a number of specific features which occur in morainal deposits and for morainal deposits of limited extent, including drumlins, crag and tail, moraine ridges (minor and major), and undifferentiated lineations and flutings (see Glacial Features). Other glacial features which may be associated with morainal deposits, for which on-site symbols are available, are listed under List of On-Site Symbols.

Sediments composed largely of organic materials resulting from the accumulation of vegetative matter. They contain at least 30% organic matter by weight (17% or more organic carbon).

General Description:
Two types of organic sediments are recognized. The first are commonly saturated with water and consist mainly of the accumulated remains of mosses, sedges, or other hydrophytic vegetation. The second are rarely saturated with water and consist typically of leaf litter, twigs, branches and mosses (folisols).

Application and Examples:

• Commonly saturated organic sediments include those deposits in bogs, fens and swamps.

Examples:	thick, level peat bog	eOp
	swamp muck overlying silty clay lacustrine sediments

• Rarely saturated organic sediments include those forest floor accumulations (duff) which directly overlie bedrock (defined below). Note: Duff or forest floor organic sediments overlying unconsolidated deposits are not mapped as organic deposits.

Examples:	thin (but more than 10 cm) layer of forest litter overlying undulating bedrock
	thick layer of forest litter overlying a gravelly sandy fluvial fan (litter layer not mapped)	gsFf

Bedrock outcrops and rock covered by a thin mantle (up to 10 cm thick) of unconsolidated or organic materials.

Application and Examples:

• Surface expression should be described for bedrock.

Examples:	steep rock scarp	Rs
	till of variable thickness overlying hummocky bedrock

• Bedrock escarpments of limited extent can be shown using the appropriate on-site symbol (see Other Landforms and Features).
  
  
• Bedrock type can be indicated where necessary, see Bedrock Subclasses.

Example:

bedrock ridge consisting of quartzite

qtRr

A layered sequence of more than three types of surficial material outcropping on a steep, erosional (scarp) slope.

Application and Examples:

• Applied to steep slopes where linear bands (in plan view) of different materials are so closely juxtaposed that they cannot be delimited separately at the scale of mapping (Figure 10).
  
  
• Texture symbols are not used to describe undifferentiated deposits. The symbol "U" may be used as part of a composite unit where a mapper judges it is necessary to indicate the presence of a specific member of the undifferentiated group.

Example:

scarp slope consisting of a layered sequence of several materials

Us

Figure 10. Steep slope or escarpment consisting of layers of till, glaciofluvial gravel, marine silt and fluvial gravel is mapped as "Us" (location of photo: Cowichan Head, Victoria).

Example:

as above, but the mapper wishes to indicate the presence of the glaciolacustrine silt and clay

Us/zcLGs

• The stratigraphic sequence that is represented by the symbol "U" may be indicated using the stratigraphic on-site symbol (see Point Observations).

Unconsolidated pyroclastic sediments.

General Description: Volcanic sediments consisting of ash, cinder lapilli and/or volcanic bombs and blocks.

Application and Examples:

• Generally applied to tephra (volcanic ash) and cinder deposits (Figure 11).

Example:

thick, sand-textured tephra over till

• In British Columbia, thin layers of volcanic ash buried by younger, non-volcanic sediments are generally less than 10 cm thick, and are not considered mappable units. If necessary, they can be shown by an on-site stratigraphic symbol (see Point Observations). Cinder cones of limited extent may be shown using the appropriate on-site symbol (see Other Landforms and Features).

Figure 11. A veneer of silt-size volcanic ash overlying rubbly, bedrock-derived colluvium (map symbol: ) (location of photo: Bridge River near Lillooet).

Sediments deposited in salt or brackish water bodies by settling from suspension and submarine gravity flows, or sediments that have accumulated in the littoral zone through shoreline processes such as wave action and longshore drift.

General Description:
Marine sediments deposited offshore generally consist of clay, silt, and sand that is well- to moderately well-sorted, and well-stratified to massive. Littoral marine sediments consist of well-sorted and well-rounded gravels and sand. Both sediments may contain shells and the remains of other marine organisms.

Application and Examples:

• Applied to all post-glacial marine sediments, including presently active shoreline deposits, and offshore and relict shoreline deposits which may have been elevated above present sea level due to isostatic or tectonic uplift (Figure 12).

Examples:	modern beach	gWAj
	elevated marine clay plain	cWp
	raised gravel beach overlying till

• Marine and lacustrine sediments have many characteristics in common. Deposits may be judged to be marine if they are located in an area that might reasonably have been covered by salt water at the time that the materials were formed. Shells or shell casts of marine origin may occur in these sediments; although their presence indicates marine origin, their absence cannot be interpreted to the contrary.

Figure 12. Raised, linear beach ridges made up of well-rounded pebble gravels (inset) with interstitial sand (map symbol: pWr) (location of photo: Queen Charlotte Islands).

• Deltas are mapped as fluvial materials, not marine sediments.
  
  
• Relict shoreline deposits can be indicated by the strandline on-site symbol; marine materials of limited extent or overlain by younger surficial materials may be indicated by the on-site stratigraphic symbol (see Point Observations). This is particularly useful because of the potential effects of marine materials on slope stability and groundwater movement.

Sediments of glacial origin laid down in a marine environment in close proximity to glacier ice. They include materials settling from suspension and from submarine gravity flows, and settled particles released by melting of both floating ice and ice shelves.

General Description:
Glaciomarine sediments range from massive diamictons to stratified, well-sorted sand, silt and/or clay. They commonly contain ice-rafted stones and lenses of till and/or glaciofluvial material. Abrupt changes in texture and distorted bedding are common. Marine shells, shell casts and the remains of other marine organisms may be present in the sediment.

Application and Examples:

• Applied to marine sediments that display abrupt textural changes, slump or collapse structures, and/or ice-rafted stones and other materials.

Example:	a silty clay glaciomarine plain with scattered boulders	zcWGp
	raised glaciomarine terrace	sgWGt

• In British Columbia, most of the marine sediments that lie at elevations above present sea level were deposited during deglaciation. If reconstruction of the local late-glacial history indicates the sediment was deposited in close proximity to glacier or floating ice, the deposits are mapped as glaciomarine "W^G" in origin. Otherwise, the deposits are mapped as marine using the surfical material symbol "W".
  
  
• Relict shoreline deposits may be mapped by the strandline on-site symbol; glaciomarine materials of limited extent or overlain by younger surficial materials may be indicated by the on-site stratigraphic symbol (see Point Observations). This is particularly useful because of the potential effects of glaciomarine materials on slope slope stability and groundwater movement. Other glacial features which may be associated with glaciomarine deposits and for which on-site symbols are available, are listed under List of On-Site Symbols.

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