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EXPLANATION OF MAP UNITS
<br />GLACIAL DEPOSITS
<br />O9dy Toun er fats al deposits (late Pleistocene ?) - unsorted. to
<br />poorly sp reed, su bangular, unconso idated, pebble to
<br />boulder -size detritus 1n a fine- grained matrix. These
<br />deposits form a hummocky topography generally only Pound
<br />above 7500 ft. may be nodtfiod by mass- wasting processes,
<br />and are potentially unstable especially when underlain
<br />by the Wasatch Formation.
<br />Ogdm Ml idle facial de�sits ( iddle PleistocL_7): unsorted,
<br />- summa ngu ar, poor y cOnso�iEated, Eouldery APtrITUS.
<br />ih ese "Posit usually have a greater amount of
<br />weathered Igneous -rock fragments and form a more
<br />subdued topography than the younger glacial deposits.
<br />O gdo Older 9l�acial� ddee�ositss (middle Pleistocene?): onsorted,
<br />du bangular, Pouriy consolidated, pebble to boulders
<br />size detritus. These deposits are exposed only In the
<br />northern part of the Bowie Quadrangle.
<br />ALLUVIAL DEPOSITS
<br />Oal Flood- l� {n a11,yium (Holocene): Mixtures of silt,
<br />sand, pe bb e7-s, a3 c.FF es recently deposited and/
<br />or reworked by fluvial processes. These deposits
<br />form the physiographic flood plains of the modern
<br />drainage system and are a potential source of sand,
<br />gravel, and crushed -rock aggregate.
<br />Oat Stream - terrace alluvium (Holocene): poorly sorted
<br />E
<br />depos rts of silt, sand, pebbles and cobbles. These
<br />deposits form small terraces that are adjacent to
<br />the Streams and are less than 10 ft (3 m) above them.
<br />Ord Valley -fill deposits (Holocene to late Pleistocene)- - s-tlneg�alned material, pS�ly epdosited by heet
<br />flow
<br />or mudflow processes. These deposits, including
<br />alluvial fan I"dforms generally form gently sloping
<br />surfaces which are incised by the modern streams.
<br />Largely derived from Mantis Shale, these deposits may
<br />be Subject to elpansfan or hydrocompacti.n upon
<br />we may contain currosire water, and are prone
<br />to sheet flood erosion and modfloe deposition.
<br />Oas Slope -wash debris (Holocene It late Pleistocene):
<br />generally fine- 5ra(ned Soil anJ rock detritus
<br />transported and deposited by running water that is
<br />not confined to channels. These deposits form a
<br />relatively thin veneer over older surffcial deposits
<br />or bedrock, may include some wind -blom (eolian)
<br />material, and may be easily eroded if protective
<br />vegetation Is removed.
<br />Oagy Younger alluvial qra vets (late Plel stocene ?): poorly
<br />sorted, mended co subrounded, unconso idated pebbles
<br />and cobbles In a matrix of sand and sill. These
<br />gravels nary greatly in composition because of local
<br />condlH Ons and they cap the first well- defined terrace
<br />above modern streams. Sheet flooding, erosion, and local
<br />swelling Soils are important geologic conditions
<br />associated with these gravels.
<br />Agin Middle alluvial gravels (middle Pleistocene ?): panel
<br />sorted, rounded to subrounded, poorly consolidated y
<br />gravels In a Tine - grained matrix. These gravels have
<br />a better developed soil profile and a greater amount
<br />of weathered igrrcouS -rock fragments than the younger
<br />all sal gra refs. Middle gravels, Including alluvial -
<br />fan and rl rer- terrace materials, form really planar
<br />surfaces situated at two or more levels and are
<br />subject to sheet flooding and erasion.
<br />D
<br />�l
<br />OTa
<br />SCALE 124000
<br />Older alluvial gravels (middle Pleistocene?), poorly
<br />sorted, rounded to subrounded, poor y consolidated
<br />gravels in a fine- grained matrix. These older gravels
<br />have a slight increase In consolidation, slightly
<br />greater weathering of igneous detritus, and a greater
<br />accumulation of caleiav carbonate fn the C horizon
<br />than the younger gravels. The deposits are subject to
<br />sheet flooding and erosion.
<br />P ediagnt 9 orals (early Pleistocene): poorly sorted
<br />,,u" rgl �arels depos Tted on a nearb
<br />lee et be tlro ck surface. These deposits haven aGundant
<br />carbonate accumulation in the C horizon and a higher
<br />Percentage of weathered igneous -rock fragments than
<br />the younger gravels. These gravels are subject to
<br />sheet flooding and erosion.
<br />Hi °h -level alluvium (Oua -,,a /Te rtfar ): bculde ry,
<br />poorT ?art —ems, aTl bola rposlis t at farm nearly
<br />planar, gently stn ping surfaces high above modern
<br />streams. S1m17ari.y to deposits previously mapped
<br />by Tweto and others (1976) suggest formation during
<br />the Tertiary or early Quaternary. These deposits are
<br />Subject to sheet flooding and erosion.
<br />I MILE
<br />1000 b 1000 2000 -- - -_ --
<br />_ 30(V .o00 5000 6000 7000 r[El
<br />5
<br />0 1 KILOMETER
<br />CONTOUR INIMAL 40 FEEL
<br />ha1.IM .0 Mix. "a Ill"',
<br />COLLUVIA_ L DEPOSITS
<br />Olt landslide de osits (Holocene to late Pie{s[ocenp ): a
<br />0 3 heterogeneous as sev6Tage of unconsoT-, ar 5 p'i an
<br />0 rock farmed by slow [o rapid downward and outward
<br />movement of the material. ':here de mass
<br />earthflpws, usually form an Irregu lar,shuvmwhich Include
<br />and may Aare an assoc sated lead scar _ y topography
<br />of deposits is. noted by subscripts 1 is Relative age
<br />Olds deposfts most likely were PtS.(I dunthe youngest).
<br />an Qls and Qis deposits In part were Tornedhtluringcene
<br />the late Pleistocene.
<br />Oml Mud— prow dPosits (Holocene)-
<br />material tth associated) dominantly fine - grained
<br />dpwnslope me.cass[ roc: fragments farmed by the
<br />ruck material. of wet Hscoos sasses of soil and
<br />topography with These deposi is have a gently undulating
<br />With decreasen an ine lsed, braided drainage network.
<br />grade to flue sal vsediments dar dnrf�hvioarea the
<br />grade to slow - moving earthflors. g viscosity
<br />Odle Debris flow de osits (Holocene to late Pleistocene):
<br />Odly unsorted, unconsolidated de rfs o� soft, rock, and
<br />displaced vegetation deE spped .here the stream gradient
<br />decreases. This gradient dFc rease most commonly occurs
<br />near the confluence of a tributary Stream with a larger
<br />drainage. These deposits result from the rapid movement
<br />and deposition of solid material during Intense rainfall
<br />or snowmelt runoff. Qdf deposits probably formed
<br />during the Holocene- Qdf deposits may have been
<br />deposited during the late Pleistocene,
<br />Ome S017- creep de oslts (Holocene
<br />sand, silt, and clay with same large, l of
<br />uck fragment,
<br />formed by Slow, down -slope movementsof near-surface
<br />materials. These deposits, characterized by surface
<br />of Sm11 S-ales and ridges perpendicular to thesdirec-
<br />"On of movement, generally are active and Indicate'
<br />areas with unstable slope conditions.
<br />Oda Debris- avalanche deposits (Holocene): unsorted mixtures
<br />Of loll and rock aterial (armed b the den and rapid downslope moremrn[ of the debrlslmaisud-
<br />usually formed during Periods of the " debris
<br />rainfall, these
<br />deposits produce a relatively small, elongate rise that
<br />may extend to gently sloping areas below the steep
<br />slopes from which the materials Originate.
<br />Oatc S�loQ�e- failure - compIS, d! Posits (HOloc ene to late
<br />etcz Pl eisto�ene: unsorted nxtures of So 1 --T rock sec matena formed by various miss-wasting Including landslides, earthfiss -w asting processes soil creep, and
<br />deb r7i avalanches. Not all of these processes form
<br />a specific deposit and the age of movement may vary
<br />within a particular area. The general age of the unit
<br />Is noted by subscripts (L Is youngest).
<br />Olm Talus /Scree de os(tz (Holocene to late Pleistocene):
<br />angu aq unT.rte , pee bTe to 6auTder -s ze ragments
<br />that mantle mountain slopes or accumulate at the base
<br />of a Darren -rock mass. These deposfts usually form
<br />steep. concave slopes and Include talus cones and
<br />lobate or tongue - shaped rock glaciers. Mass - wasting
<br />Processes usually are currently active In the forma-
<br />tion of these deposits.
<br />Ocw [ °fluvial- r�edg�e doe sits Nolncene to late Pleistocene)-
<br />unconsolidated, heter.g�neous soiima[eria an roc
<br />fragments found near the base cf the slope. Formed by
<br />gravity- dominated processes the deposits may be Sub -
<br />aect to continued sass - wasting.
<br />BEDROCK UNITS
<br />Kmv Mesaverde Formation (i er Cretaceous): brown, ra ,
<br />and light gray to white sandstone Interbedded wftn IIIIIII IIIIII VIII IIIIII VIII VIIIIIII IIII
<br />dark gray shale. These sedimentary reeks generally
<br />form very steep slopes which may be subject to rock-
<br />falls and other mass - wasting p; ocesses. Co®prclally
<br />Important coal beds occur in the lower part of the
<br />formation. / / tC -1 / ( Ll c
<br />Aepekkil 1 i I
<br />Figure H5
<br />AREA GEOLOGY FROM
<br />SURFICIAL GEOLOGY OF THE
<br />SOMERSET QUADRANGLE
<br />by Walter R. Junge, 1978
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<br />EXPLANATION OF MAP UNITS
<br />GLACIAL DEPOSITS
<br />O9dy Toun er fats al deposits (late Pleistocene ?) - unsorted. to
<br />poorly sp reed, su bangular, unconso idated, pebble to
<br />boulder -size detritus 1n a fine- grained matrix. These
<br />deposits form a hummocky topography generally only Pound
<br />above 7500 ft. may be nodtfiod by mass- wasting processes,
<br />and are potentially unstable especially when underlain
<br />by the Wasatch Formation.
<br />Ogdm Ml idle facial de�sits ( iddle PleistocL_7): unsorted,
<br />- summa ngu ar, poor y cOnso�iEated, Eouldery APtrITUS.
<br />ih ese "Posit usually have a greater amount of
<br />weathered Igneous -rock fragments and form a more
<br />subdued topography than the younger glacial deposits.
<br />O gdo Older 9l�acial� ddee�ositss (middle Pleistocene?): onsorted,
<br />du bangular, Pouriy consolidated, pebble to boulders
<br />size detritus. These deposits are exposed only In the
<br />northern part of the Bowie Quadrangle.
<br />ALLUVIAL DEPOSITS
<br />Oal Flood- l� {n a11,yium (Holocene): Mixtures of silt,
<br />sand, pe bb e7-s, a3 c.FF es recently deposited and/
<br />or reworked by fluvial processes. These deposits
<br />form the physiographic flood plains of the modern
<br />drainage system and are a potential source of sand,
<br />gravel, and crushed -rock aggregate.
<br />Oat Stream - terrace alluvium (Holocene): poorly sorted
<br />E
<br />depos rts of silt, sand, pebbles and cobbles. These
<br />deposits form small terraces that are adjacent to
<br />the Streams and are less than 10 ft (3 m) above them.
<br />Ord Valley -fill deposits (Holocene to late Pleistocene)- - s-tlneg�alned material, pS�ly epdosited by heet
<br />flow
<br />or mudflow processes. These deposits, including
<br />alluvial fan I"dforms generally form gently sloping
<br />surfaces which are incised by the modern streams.
<br />Largely derived from Mantis Shale, these deposits may
<br />be Subject to elpansfan or hydrocompacti.n upon
<br />we may contain currosire water, and are prone
<br />to sheet flood erosion and modfloe deposition.
<br />Oas Slope -wash debris (Holocene It late Pleistocene):
<br />generally fine- 5ra(ned Soil anJ rock detritus
<br />transported and deposited by running water that is
<br />not confined to channels. These deposits form a
<br />relatively thin veneer over older surffcial deposits
<br />or bedrock, may include some wind -blom (eolian)
<br />material, and may be easily eroded if protective
<br />vegetation Is removed.
<br />Oagy Younger alluvial qra vets (late Plel stocene ?): poorly
<br />sorted, mended co subrounded, unconso idated pebbles
<br />and cobbles In a matrix of sand and sill. These
<br />gravels nary greatly in composition because of local
<br />condlH Ons and they cap the first well- defined terrace
<br />above modern streams. Sheet flooding, erosion, and local
<br />swelling Soils are important geologic conditions
<br />associated with these gravels.
<br />Agin Middle alluvial gravels (middle Pleistocene ?): panel
<br />sorted, rounded to subrounded, poorly consolidated y
<br />gravels In a Tine - grained matrix. These gravels have
<br />a better developed soil profile and a greater amount
<br />of weathered igrrcouS -rock fragments than the younger
<br />all sal gra refs. Middle gravels, Including alluvial -
<br />fan and rl rer- terrace materials, form really planar
<br />surfaces situated at two or more levels and are
<br />subject to sheet flooding and erasion.
<br />D
<br />�l
<br />OTa
<br />SCALE 124000
<br />Older alluvial gravels (middle Pleistocene?), poorly
<br />sorted, rounded to subrounded, poor y consolidated
<br />gravels in a fine- grained matrix. These older gravels
<br />have a slight increase In consolidation, slightly
<br />greater weathering of igneous detritus, and a greater
<br />accumulation of caleiav carbonate fn the C horizon
<br />than the younger gravels. The deposits are subject to
<br />sheet flooding and erosion.
<br />P ediagnt 9 orals (early Pleistocene): poorly sorted
<br />,,u" rgl �arels depos Tted on a nearb
<br />lee et be tlro ck surface. These deposits haven aGundant
<br />carbonate accumulation in the C horizon and a higher
<br />Percentage of weathered igneous -rock fragments than
<br />the younger gravels. These gravels are subject to
<br />sheet flooding and erosion.
<br />Hi °h -level alluvium (Oua -,,a /Te rtfar ): bculde ry,
<br />poorT ?art —ems, aTl bola rposlis t at farm nearly
<br />planar, gently stn ping surfaces high above modern
<br />streams. S1m17ari.y to deposits previously mapped
<br />by Tweto and others (1976) suggest formation during
<br />the Tertiary or early Quaternary. These deposits are
<br />Subject to sheet flooding and erosion.
<br />I MILE
<br />1000 b 1000 2000 -- - -_ --
<br />_ 30(V .o00 5000 6000 7000 r[El
<br />5
<br />0 1 KILOMETER
<br />CONTOUR INIMAL 40 FEEL
<br />ha1.IM .0 Mix. "a Ill"',
<br />COLLUVIA_ L DEPOSITS
<br />Olt landslide de osits (Holocene to late Pie{s[ocenp ): a
<br />0 3 heterogeneous as sev6Tage of unconsoT-, ar 5 p'i an
<br />0 rock farmed by slow [o rapid downward and outward
<br />movement of the material. ':here de mass
<br />earthflpws, usually form an Irregu lar,shuvmwhich Include
<br />and may Aare an assoc sated lead scar _ y topography
<br />of deposits is. noted by subscripts 1 is Relative age
<br />Olds deposfts most likely were PtS.(I dunthe youngest).
<br />an Qls and Qis deposits In part were Tornedhtluringcene
<br />the late Pleistocene.
<br />Oml Mud— prow dPosits (Holocene)-
<br />material tth associated) dominantly fine - grained
<br />dpwnslope me.cass[ roc: fragments farmed by the
<br />ruck material. of wet Hscoos sasses of soil and
<br />topography with These deposi is have a gently undulating
<br />With decreasen an ine lsed, braided drainage network.
<br />grade to flue sal vsediments dar dnrf�hvioarea the
<br />grade to slow - moving earthflors. g viscosity
<br />Odle Debris flow de osits (Holocene to late Pleistocene):
<br />Odly unsorted, unconsolidated de rfs o� soft, rock, and
<br />displaced vegetation deE spped .here the stream gradient
<br />decreases. This gradient dFc rease most commonly occurs
<br />near the confluence of a tributary Stream with a larger
<br />drainage. These deposits result from the rapid movement
<br />and deposition of solid material during Intense rainfall
<br />or snowmelt runoff. Qdf deposits probably formed
<br />during the Holocene- Qdf deposits may have been
<br />deposited during the late Pleistocene,
<br />Ome S017- creep de oslts (Holocene
<br />sand, silt, and clay with same large, l of
<br />uck fragment,
<br />formed by Slow, down -slope movementsof near-surface
<br />materials. These deposits, characterized by surface
<br />of Sm11 S-ales and ridges perpendicular to thesdirec-
<br />"On of movement, generally are active and Indicate'
<br />areas with unstable slope conditions.
<br />Oda Debris- avalanche deposits (Holocene): unsorted mixtures
<br />Of loll and rock aterial (armed b the den and rapid downslope moremrn[ of the debrlslmaisud-
<br />usually formed during Periods of the " debris
<br />rainfall, these
<br />deposits produce a relatively small, elongate rise that
<br />may extend to gently sloping areas below the steep
<br />slopes from which the materials Originate.
<br />Oatc S�loQ�e- failure - compIS, d! Posits (HOloc ene to late
<br />etcz Pl eisto�ene: unsorted nxtures of So 1 --T rock sec matena formed by various miss-wasting Including landslides, earthfiss -w asting processes soil creep, and
<br />deb r7i avalanches. Not all of these processes form
<br />a specific deposit and the age of movement may vary
<br />within a particular area. The general age of the unit
<br />Is noted by subscripts (L Is youngest).
<br />Olm Talus /Scree de os(tz (Holocene to late Pleistocene):
<br />angu aq unT.rte , pee bTe to 6auTder -s ze ragments
<br />that mantle mountain slopes or accumulate at the base
<br />of a Darren -rock mass. These deposfts usually form
<br />steep. concave slopes and Include talus cones and
<br />lobate or tongue - shaped rock glaciers. Mass - wasting
<br />Processes usually are currently active In the forma-
<br />tion of these deposits.
<br />Ocw [ °fluvial- r�edg�e doe sits Nolncene to late Pleistocene)-
<br />unconsolidated, heter.g�neous soiima[eria an roc
<br />fragments found near the base cf the slope. Formed by
<br />gravity- dominated processes the deposits may be Sub -
<br />aect to continued sass - wasting.
<br />BEDROCK UNITS
<br />Kmv Mesaverde Formation (i er Cretaceous): brown, ra ,
<br />and light gray to white sandstone Interbedded wftn IIIIIII IIIIII VIII IIIIII VIII VIIIIIII IIII
<br />dark gray shale. These sedimentary reeks generally
<br />form very steep slopes which may be subject to rock-
<br />falls and other mass - wasting p; ocesses. Co®prclally
<br />Important coal beds occur in the lower part of the
<br />formation. / / tC -1 / ( Ll c
<br />Aepekkil 1 i I
<br />Figure H5
<br />AREA GEOLOGY FROM
<br />SURFICIAL GEOLOGY OF THE
<br />SOMERSET QUADRANGLE
<br />by Walter R. Junge, 1978
<br />
|