260
The Stratigraphic Architecture of Fluvial Depositional Systems
L!] Fluvial deposits
ft{,:�;@l) Shelf phaae delta
J;��� Shelf phaee delta
Ill Shelf margin delte
(thlckne•• In m)
Fig. 9.12. Depositional systems on part of the continental
shelfofLouisiana that developed during the Pleistocene at
a time oflow sea level. Note the fluvial systems occupying
incised valleys. The sea-level cycle during which this
example, during low stands of sea level, fluvial systems become incised into the continental shelf and
extend their courses to the shelf margin. During the
subsequent sea-level rise, these broad incised valleys
are then fi lled with fluvial or estuarine deposits (depending on the balance between sediment supply
paleogeography developed was one of many ft.fth-order
gladoeustatic (Milankovitch) cycles that affected conti�
nental margins during the late Cenozoic. (Suter et al. 1987)
and rate of base-level rise). An example of the depositional systems that result is iUustrated in Fig. 9. 12.
Commonly, the scale of such incised valleys is little
different from that of channel systems generated by
autogenic processes, and correct interpretations require very careful mapping.