Classification of Arch itectural Elements
93
Ta ble 4.3. Arch itectu ral elements in fluvial deposits. (Modified from Miall 1985)
Element
Symbol
Channels
CH
Gravel ba rs and bedfo rms
GB
Sandy bedfo rms
SB
Downstream-accretion ma croform DA
Late ral-accretion macrofo rm
LA
Scour hollows
HO
Sediment gravity flows
SG
Laminated sand sheet
LS
Overbank fines
FF
Facies classification from Miall (1978b).
Prin cipal
fades
assem bla ge
Any
co mbination
Gm, Gp, Gt
St, Sp, Sh, Sl,
Sr, Se, Ss
St, Sp, Sh, Sl,
Sr, Se, Ss
St, Sp, Sh, Sl,
Se, Ss, less
commonly Gm,
Gt, Gp
Gh, Gt, St, Sl
Gmm, Gmg,
Gci, Gem
Sh, Sl; minor
Sp, Sr
Fm, Fl
Geomet ry and relationships
Finger, lens or sheet; concave-up erosional
base; scale and shape highly va ria ble;
internal concave-up 3rd-order erosion
surfa ces common
Lens, blanket; usually ta bula r bo dies;
commonly inte rbedded with SB
Lens, sheet, blanket, wedge, occurs as
channel fills , crevasse splays, minor bars
Lens resting on flat or channeled ba se,
with convex-up 3rd -orde r inte rnal erosion
su rfaces and upper 4th-o rde r bounding surfa ce
Wedge, sheet, lobe; characterized by
internal lateral-accretion 3rd-or der su rfa ces
Scoop-shaped hollow with asymmet ric fill
Lobe, sheet, typi cally inte rbedded with GB
Sheet, bla nket
Thin to thick blankets; commonly
interbedded with SB; may fill abandoned
ch annels
Table 4.4. Architectural elements in the Cutle r Formation, New Mexico. (Adapted from Eberth and Miall l991)
Element
Symbol
Lithology
Geometry
Interp retation
Major ss.
CHS
Gm, Se, St,
w/d > 15, with 'wings',
Braided fluvial channel
sheet
Sh, Sl,
sto reys 2-5 m th ick,
ra re Sp
units < 1 krn wide
Major ss.
CHR
Gm, Se, St,
w/d< 15, with 'wings',
Anastomosed fluvial ch annel
ri bbon
Sh, Sl,
sto reys <5 m thick
rare Sp
Minor ss
cs
Se, Sh, Sl,
Tabula r, flat- based,
Sheet splay
sheet
rare St, Sr
< 1 m thick, wing of
CHS sheet
Mino r ss
CRS
Se, St, Sl,
w/d< 10,
Minor crevasse channel
le ns
Sh, Sr
<1m thick
U-shaped
CRM
Se, Sr, Fl,
1-10 m thick
Deep, stable crevasse ch annel
mixed fJll
p
1-30 m wide
Interlam ,
FFP
Sr , Fl, P
Ta bula r,
Proximal floodplain deposits
mixed
<15m thi ck
sheets
SiltstoneFFD
Fl, P
Ta bula r
Distal floodplain deposits
mudstone
< 5 m thi ck
sheets
93
Ta ble 4.3. Arch itectu ral elements in fluvial deposits. (Modified from Miall 1985)
Element
Symbol
Channels
CH
Gravel ba rs and bedfo rms
GB
Sandy bedfo rms
SB
Downstream-accretion ma croform DA
Late ral-accretion macrofo rm
LA
Scour hollows
HO
Sediment gravity flows
SG
Laminated sand sheet
LS
Overbank fines
FF
Facies classification from Miall (1978b).
Prin cipal
fades
assem bla ge
Any
co mbination
Gm, Gp, Gt
St, Sp, Sh, Sl,
Sr, Se, Ss
St, Sp, Sh, Sl,
Sr, Se, Ss
St, Sp, Sh, Sl,
Se, Ss, less
commonly Gm,
Gt, Gp
Gh, Gt, St, Sl
Gmm, Gmg,
Gci, Gem
Sh, Sl; minor
Sp, Sr
Fm, Fl
Geomet ry and relationships
Finger, lens or sheet; concave-up erosional
base; scale and shape highly va ria ble;
internal concave-up 3rd-order erosion
surfa ces common
Lens, blanket; usually ta bula r bo dies;
commonly inte rbedded with SB
Lens, sheet, blanket, wedge, occurs as
channel fills , crevasse splays, minor bars
Lens resting on flat or channeled ba se,
with convex-up 3rd -orde r inte rnal erosion
su rfaces and upper 4th-o rde r bounding surfa ce
Wedge, sheet, lobe; characterized by
internal lateral-accretion 3rd-or der su rfa ces
Scoop-shaped hollow with asymmet ric fill
Lobe, sheet, typi cally inte rbedded with GB
Sheet, bla nket
Thin to thick blankets; commonly
interbedded with SB; may fill abandoned
ch annels
Table 4.4. Architectural elements in the Cutle r Formation, New Mexico. (Adapted from Eberth and Miall l991)
Element
Symbol
Lithology
Geometry
Interp retation
Major ss.
CHS
Gm, Se, St,
w/d > 15, with 'wings',
Braided fluvial channel
sheet
Sh, Sl,
sto reys 2-5 m th ick,
ra re Sp
units < 1 krn wide
Major ss.
CHR
Gm, Se, St,
w/d< 15, with 'wings',
Anastomosed fluvial ch annel
ri bbon
Sh, Sl,
sto reys <5 m thick
rare Sp
Minor ss
cs
Se, Sh, Sl,
Tabula r, flat- based,
Sheet splay
sheet
rare St, Sr
< 1 m thick, wing of
CHS sheet
Mino r ss
CRS
Se, St, Sl,
w/d< 10,
Minor crevasse channel
le ns
Sh, Sr
<1m thick
U-shaped
CRM
Se, Sr, Fl,
1-10 m thick
Deep, stable crevasse ch annel
mixed fJll
p
1-30 m wide
Interlam ,
FFP
Sr , Fl, P
Ta bula r,
Proximal floodplain deposits
mixed
<15m thi ck
sheets
SiltstoneFFD
Fl, P
Ta bula r
Distal floodplain deposits
mudstone
< 5 m thi ck
sheets