Table 7 (cont'd).
Geomorphic unit
Description
Headwater
Small, shallow deposits formed in the low overbank environment in proximity to the channels of
Floodplain, Steep
steep headwater streams in upland areas. Sediments typically are composed of silts and fine sands
Active-floodplain
and have a laminar, interbedded structure. Frequent deposition prevents organic matter accumula-
Cover Deposit
tion. Fine-grained material must be >40 cm thick and organic layers are less than 10% of the
(Fhsca)
thickness. Permafrost is absent.
Headwater
Small, shallow deposits formed in higher overbank environments in proximity to the channels
Floodplain, Steep
of steep headwater streams in upland areas. Sediments typically are composed of interbedded
Inactive-floodplain
organic material, silts, and fine sands. Cover material is >40 cm thick and organic layers occupy 10
Cover Deposit
90% of the thickness. Permafrost is absent.
(Fhsci)
Headwater
Small, shallow deposits formed in distal overbank environments associated with the channels of
Stream, Steep
steep headwater streams in upland areas where flooding is rare. Surface materials include a mixture
Abandoned
of fluvial and organic materials, but typically are highly organic. The deposit is >40 cm thick and
Floodplain
organic layers compose >90% of the top 40 cm. Permafrost usually is present.
(Fhscb)
Alluvial Fan
Similar to above but flooding and deposition are infrequent. Deposits include organic matter at the
Inactive-riverbed
surface and vegetation is present. Permafrost usually is absent.
Deposit (Ffri)
Alluvial Fan
Similar to above, except flooding is rare. Thus, gravelly deposits have thick (>20 cm) organic layers
Abandoned
at the surface or well developed A horizons, indicating a long period since last depositional event.
Riverbed (Ffrb)
Permafrost usually is absent.
Lowland
Fine-grained, organic-rich materials moved downslope by slopewash, solifluction, and in some
Retransported
cases, piping and, thus, influenced by both fluvial and gravity processes. Loess also may be
Deposits (Fsl)
incorporated in these deposits. The surface has a dendritic, feathery pattern indicative of small-scale
fluvial processes. The material generally is frozen and ice rich. This unit usually occurs on the toe
slopes in upland areas.
Hilly
Areas with gentle hill and swale topography in lowland areas. Deposits generally include silty to
Retransported
sandy material with occasional gravel-sized fragments that occur in horizontally stratified deposits
Deposits (Fsu)
indicative of fluvial origin. The topography may have resulted from ice aggradation and thermokarst
processes or from underlying highly eroded unconsolidated material.
Glaciofluvial
Undifferentiated deposits that have been transported by glacial meltwater streams that flow within or
Deposit (GF)
beyond the terminal margin of an ice-sheet or glacier. Class is used to characterize subsurface
deposits.
Glaciovluvial
Sediments that have been deposited by glacial meltwater streams beyond the terminal glacial
Outwash Active-
margin. The proglacial drift includes outwash fans, deltas, aprons, valley trains, and both pitted and
riverbed Deposit
nonpitted outwash plains. Sediments are composed of moderately to well-sorted, clean-washed
bedload sand and gravel with some boulders. Outwash leads to an active glacial front. Braided
processes and deposition are so active that vegetation is absent on interfluve bars. Permafrost is
absent.
Glaciofluvial
Similar to above, except that deposits occur adjacent to active channel where flooding and sedimen-
Outwash Inactive- tation are infrequent. Vegetation is present and thin layers (<20 cm) of organic matter have
riverbed Deposit
accumulated at the surface. Permafrost is absent.
Glaciofluvial
Deposits formed by meltwater streams beyond the terminal glacial margin. They lack significant
Outwash Aband.
accumulations of fine-grained cover deposits but have thick layers (>20 cm) of organic matter at the
Riverbed (GForb)
surface or have well developed A horizons in the coarse-grained soils. Permafrost is absent.
Glaciofluvial
Fine-grained material deposited by overbank flooding events on glaciofluvial outwash deposits.
Outwash, Inactive
Sediments range from sandy silts to clay material deposited in slackwater environments. Cover
Cov. Dep. (GFoci)
material is >40 cm thick and organic layers compose 1090% of the thickness. Permafrost is absent.
Glaciofluvial
Fine-grained material deposited by overbank flooding events on glaciofluvial outwash deposits.
Outwash
Sediments range from sandy silts to clay material deposited in slackwater environments. Surface
Abandoned Cover
materials also have incorporated substantial amounts of wind-blown silt and organic matter.
(GFocb)
Permafrost usually is present. Groundwater seeps and linear headwater streams form a dense
fluvial pattern on the surface.
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