Basic Paleogeographic Models for Nonmarine Basins
-z
Fig. 11.85. The Po Basin, Italy, an example of basin�f ill
model 7. (Miall l98lb)
Model 5 occurs mainly in areas facing open
oceans, which are characterized by high wave en�
ergy. Deltaic deposits are reworked into superim�
posed beach ridges flanking the river mouth, which
may be deflected downcurrent into a spit. Modern
ex amples of such alluvial systems include the Pacific
coast of Guatemala (basin type 2.2; Fig. 11.82) and
the Sao Francisco delta of Brazil (b asin type 1.2.2).
Ancient examples have been described from the Gulf
C:: oast (Fisher 1969).
Models 6, 7, 8, and 9 are comb inat ions of longitudinal trunk rivers wit h transv erse trib ut aries. The
latt er are commonly alluvial fans at the basin mar�
gins. Most major rivers· and large inland basins show
one or other of these four patt erns. Trunk river
417
Fig. 11.86. The Central Lowlands of Myanmar (Burma),
an example of basin-flll model S. (Miall 1981b)
lengt h may be thousands of kilometers. The models
aie distinguished mainly on the basis of river termination patterns. In the case of smaller rivers wit h low
sediment discharge, or those emptying into a rapidly
subsiding basin, there may be inadequate sediment
load to form a delta. This is model 6. Rivers may be
ephemeral, terminating in a sheet flood.zone along a
pl aya lake margin (Fig. 11.78), or they form an estuary wit h tidal flats. Modern examples of the latt er
include the Thames (U.K.), the Amazon, the Rhine,
the Susitna (Cook Inlet), and the Colorado at the
Gulf of California. Many intermontane basins in
California and Nevada (b ackarc rifts, basin type 2.3)
show longitudinal rivers terminating in a playa or
permanent lake. Some strike-slip basins (e.g., JOrdan
Valley, basin ty pe 3.3; Fig. 11.8 3) and rift systems
(e.g., East African rifts, basin type 1.!; Fig. 11.84) also
show this pattern. Ancient nonmarine examples include the Devonian fluvial sediments of Spitsbergen,
which flow int o a playa (basin type 4.3; Friend and
-z
Fig. 11.85. The Po Basin, Italy, an example of basin�f ill
model 7. (Miall l98lb)
Model 5 occurs mainly in areas facing open
oceans, which are characterized by high wave en�
ergy. Deltaic deposits are reworked into superim�
posed beach ridges flanking the river mouth, which
may be deflected downcurrent into a spit. Modern
ex amples of such alluvial systems include the Pacific
coast of Guatemala (basin type 2.2; Fig. 11.82) and
the Sao Francisco delta of Brazil (b asin type 1.2.2).
Ancient examples have been described from the Gulf
C:: oast (Fisher 1969).
Models 6, 7, 8, and 9 are comb inat ions of longitudinal trunk rivers wit h transv erse trib ut aries. The
latt er are commonly alluvial fans at the basin mar�
gins. Most major rivers· and large inland basins show
one or other of these four patt erns. Trunk river
417
Fig. 11.86. The Central Lowlands of Myanmar (Burma),
an example of basin-flll model S. (Miall 1981b)
lengt h may be thousands of kilometers. The models
aie distinguished mainly on the basis of river termination patterns. In the case of smaller rivers wit h low
sediment discharge, or those emptying into a rapidly
subsiding basin, there may be inadequate sediment
load to form a delta. This is model 6. Rivers may be
ephemeral, terminating in a sheet flood.zone along a
pl aya lake margin (Fig. 11.78), or they form an estuary wit h tidal flats. Modern examples of the latt er
include the Thames (U.K.), the Amazon, the Rhine,
the Susitna (Cook Inlet), and the Colorado at the
Gulf of California. Many intermontane basins in
California and Nevada (b ackarc rifts, basin type 2.3)
show longitudinal rivers terminating in a playa or
permanent lake. Some strike-slip basins (e.g., JOrdan
Valley, basin ty pe 3.3; Fig. 11.8 3) and rift systems
(e.g., East African rifts, basin type 1.!; Fig. 11.84) also
show this pattern. Ancient nonmarine examples include the Devonian fluvial sediments of Spitsbergen,
which flow int o a playa (basin type 4.3; Friend and