Soils of the - Agriculture and Agri-Food Canada

areas have shallow groundwater tables . Sumas Lake, which was located just west of the presen t
Vedder Canal, was artificially drained in the 1920's .
Partially stratified, silty and clayey deposits are most common . These are stone-free and moderatel y
to slowly pervious . The surfaces in some areas have been modified by fluvial processes . West of th e
Vedder Canal, an extensive area of poorly drained lacustrine sand occurs, and scattered through th e
valley are small areas of stratified, sandy, raised spits, bars and beach ridges .
(8) Glaciolacustrine deposits occur north of Mission, near the south end of Coquitlam Lake and in th e
Statlu Creek valley. These deposits, laid down in temporary lakes during glacial time, range fro m
sandy to silty in texture and are moderately stratified and compact . Topography is mostly srongl y
undulating to strongly rolling due to post-depositional erosion . A silty eolian capping occurs on th e
deposits north of Mission .
(9) Eolian deposits have been briefly discussed in relation to other surficial deposits . These silty,
permeable deposits, usually less than 1 m thick, mantle most of the uplands and lower mountai n
slopes of the map area east of the Langley Valley and Haney. They appear to have originated from th e
extensive glacial outwash areas in the vicinity of, and south, from the Abbotsford Airport . Som e
volcanic ash may be incorporated in the eolian material since some soil properties are similar to thos e
of soils derived from volcanic ash elsewhere .
Near Abbotsford, several areas of sand dunes occur . These sandy, moderately to strongly rollin g
deposits are also capped by silty deposits .
10) Organic deposits occupy significant portions of the Langley-Vancouver map area, particularly on th e
lowlands of the Lower Fraser Valley. Organic deposits form when the rate of organic matter accumula -
tion exceeds the rate of decomposition . Two types of organic deposits occur .
(i) The first consists mainly of peat derived from accumulations of reeds, sedges and moss, in variou s
stages of decomposition . The accumulations are at least 40 cm thick and may range to as much a s
10 m deep but are usually less than 2 m thick . They contain at least 17 percent organic carbon .
These deposits are usually found in depressional or level areas which are poorly drained an d
subject to excess water for long periods . Most areas are associated with deltaic or floodplai n
deposits but some also occur on the uplands and a few in the mountains . In some areas a
proportion of mineral material is mixed with the organic, usually carried in and deposited durin g
flooding by adjacent water courses .
(ii) The second type of organic deposit occurs in forested areas and consists of freely draine d
accumulations of needles, leaves, twigs, moss and other forest floor material at least 10 cm thic k
overlying bedrock . These organic deposits are relatively common in the mountainous areas ,
particularly at the higher elevations on rocky hummocks, ridges and knobs devoid of mineral soil .
The previous descriptions of the surficial geologic materials (soil parent materials) have been both brief
and general . Readers wishing more detailed, specific information, particularly for the Lower Fraser Valle y
portion of the map area, are referred to several publications listed in "Selected Bibliography" at the end of thi s
report. These publications include maps showing the distribution and extent of the different deposits an d
therefore they are not reproduced here . The distribution of soil forming deposits in the mountainous portion o f
the map area, however, have been generally less well defined in publications . Figure 2 has therefore bee n
generalized from the soil maps in Volume 2 to show the general distribution and extent of the surficial deposits i n
the mountainous areas .
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