River Systems
Four types, braided, meandering,
anastamosing and straight
Grand Canyon, erosion
River incision
in Indus Suture
Zone
River types
Links between sinuosity and slope
Anastomosing river stratigraphy
Braided rivers
• Typically developed in mountainous terrain on
higher gradients. Typified by high degree of
seasonality. Permanent channels with ripple crossed
bedded sands develop during periods of low flow.
These channels meander between sand bars that are
active only during flood stage, these develop larger
scale cross beds. Sediments are typically sandy and
pebbly, usually moderate to well sorted, texturally
moderately mature. Ancient example- Devonian Old
Red Sandstone. Modern example - Saskatchewan
River.
Braided
River
Model
Braided
River Model
and
stratigraphy
Braided
River
Braided geometry, Matanuksa River, Alaska
Braided River, Nubra, India
Braided River,
Shyok River, India
Anastomosing River, Indian foreland
Channel sandstone facies
Meandering Rivers
Typically developed in coastal plain areas, lower
gradient. More continuous flow, finer grained
sediment than braided. Channel sediment is marked
by the deep stream migration of meanders and the
construction of cross laminated sands on point bars in
the inner bends of meanders. Channels are separated
by levees from flood plains that are comprised of
finer grained muds and sands deposited after breach
of levee during flood stage, usually vegetated. Flood
stage can lead to cut-off of meanders and breakthrough of river.
Meandering Rivers, contd.
Abandoned meanders become Ox-bow lakes, filled by
clays. Meandering river deposits typified by finingupward stratigraphy. Sediments are typically sandy,
silty and clayey. Well sorted. Sandstones form
isolated channels in finer background. Ancient
example- Jurassic, Brent Group of North Sea. Modern
example - Brazos and Mississippi Rivers.
Meanders
in the
Amazon
Basin
McKenzie River
meanders and
glacial lakes
Ox Bow Lake/meanders
Point bar
deposits
Braided versus
meandering
river type
sections
Impact of
sinuosity on
stratigraphy
Channel migration-Ganges
Ganges and Himalaya thrust front
Indus River and
tectonic uplift,
Kohat Plateau
Effect of
tectonism on
location of
rivers
Fluvial facies examples
Indus Molasse,
fluvial sandstone
Slumped sediment,
modern Indus River
Climbing wave ripples, Indus River