206
8.2.1 Gravel-Bed Braided River
with Sediment-Gravity-Flow Deposits
Many basin margins are characterized by wedges of
gravel deposits. Commonly, these are deposited by
distributary fluvial systems that form the coneshaped deposits of alluvial fans. Two fluvial styles
are typical, one the subject of this section, in which
sediment-gravity-flow deposits (element SG), related deposits of high-energy stream flow, and their
winnowed derivatives make up the successions, and
EXPLANATION
Probable debfls-flnw lobu
MATERIAL SIZE (mo�. nile pteaent)
Pebboe- to cabble·sl�ed molerial
Clay· to p�bbto-uized matoliol
All other material I� cobble·
to boulllet-�l�cd
Fluvial Styles and Facies Models
one (described in Sect. 8.2.2) in which sedimentgravity flows are rare or absent, with sedimentation
dominated by element GB (the role of depositional
processes and their deposits in the classification of
alluvial fans is discussed in Sect. 8.3). In both cases,
minor thicknesses of sand and fine-grained deposits
(elements SB, OF) represent low-water and overbank sedimentation, respectively. Both types of fluvial style may occur in the same basin, with the
frequency of debris flows and other sediment-graw
vity flows dependent on the geology and climate of
AGE OF MATERIAL
Pe Ptesent channel
Ove Overllow chaMel
Ore Older chanMI material
Ole Olo"�sl channel motedol
Yf Youn�et fan surface
Of Older lon su
Contact botwuan units distinguished by
n : ot ? tlol whore �
IOP<)�tophy or matotial size,
d�Sto�et ovetlopponq
opproxim
Contcureo" port of map by plane
table mothods. Conlral on
remainder by air phologropho
Contout lntervel 30 feat.
Eroskmol banks
Fig. 8.9. Surface of the Trollheim fan> Death Valley, California> showing the distribution of the major types of
fluvial deposit, and the position of the modern fan channel
(Hooke 1967). This fan is dominated by sediment-gravityflow processes (Blair and McPherson 1992), but other fans
where this type of fl ow is important may also be strongly
influenced by traction currents and their deposits
8.2.1 Gravel-Bed Braided River
with Sediment-Gravity-Flow Deposits
Many basin margins are characterized by wedges of
gravel deposits. Commonly, these are deposited by
distributary fluvial systems that form the coneshaped deposits of alluvial fans. Two fluvial styles
are typical, one the subject of this section, in which
sediment-gravity-flow deposits (element SG), related deposits of high-energy stream flow, and their
winnowed derivatives make up the successions, and
EXPLANATION
Probable debfls-flnw lobu
MATERIAL SIZE (mo�. nile pteaent)
Pebboe- to cabble·sl�ed molerial
Clay· to p�bbto-uized matoliol
All other material I� cobble·
to boulllet-�l�cd
Fluvial Styles and Facies Models
one (described in Sect. 8.2.2) in which sedimentgravity flows are rare or absent, with sedimentation
dominated by element GB (the role of depositional
processes and their deposits in the classification of
alluvial fans is discussed in Sect. 8.3). In both cases,
minor thicknesses of sand and fine-grained deposits
(elements SB, OF) represent low-water and overbank sedimentation, respectively. Both types of fluvial style may occur in the same basin, with the
frequency of debris flows and other sediment-graw
vity flows dependent on the geology and climate of
AGE OF MATERIAL
Pe Ptesent channel
Ove Overllow chaMel
Ore Older chanMI material
Ole Olo"�sl channel motedol
Yf Youn�et fan surface
Of Older lon su
Contact botwuan units distinguished by
n : ot ? tlol whore �
IOP<)�tophy or matotial size,
d�Sto�et ovetlopponq
opproxim
Contcureo" port of map by plane
table mothods. Conlral on
remainder by air phologropho
Contout lntervel 30 feat.
Eroskmol banks
Fig. 8.9. Surface of the Trollheim fan> Death Valley, California> showing the distribution of the major types of
fluvial deposit, and the position of the modern fan channel
(Hooke 1967). This fan is dominated by sediment-gravityflow processes (Blair and McPherson 1992), but other fans
where this type of fl ow is important may also be strongly
influenced by traction currents and their deposits