Continental shelf environments - Environmental Sedimentology - page 353

dominant fair-weather processes and the rela-
tive interaction with storm-associated processes
(Fig. 10.2), where of primary interest are those
processes that are reflected in the nature, dis-
tribution and stratigraphy of shelf deposits.
Shelf sedimentary processes (Fig. 10.3) operate
at a range of physical and temporal scales, so
that the relative sedimentary impacts of these
processes depend on their frequency, magnitude
and recurrence intervals. Sediment transport is
a cubic (or quartic) function of flow speed
(Soulsby 1983, 1997), which, together with the

presence of flow thresholds of transport, means
that short periods of fast flows (e.g. related to
storms, cyclones or tsunami) may sometimes be
more significant in terms of sediment transport
than longer periods of slower flow.

10.1.2 Environmental sedimentology of shelf
environments

Human influences on the sedimentary regime of
continental shelves include, but are not limited
to, impacts by fisheries (especially trawling),

Forcing functions

Sediment characteristics

10 5 yr

Centuries: macro-scale sediment
balances, wind climate, sea-level
fluctuations

Depositional
systems
tract

Millenia: macro-scale
sediment balances,
sea-level fluctuations,
climate, neotectonics

10,000 yr

1000 yr

Depositional
systems

100 yr

Facies

Beds

Decades: storm bed
deposition

10 yr

Laminae

1 yr

Seasons:
shoreface variability,
calm/stormy weather,
river run-off

1 mo

Nearshore
morphology

1 wk

1 day

Dunes

10,000 s

1000 s

Events: storm surges, flooding,
water level fluctuations due to
seiches, river run-off

Ripples

100 s

10 s

Suspension
bands

1 s

0.1 s

0.01 s

0.1 mm 1 mm 1 cm 10 cm 1 m 10 m 1 km 10 km 100 km 1000 km
Spatial scale

Fig. 10.3 Forces operating in coastal and shelf environments and their sedimentary products. (Modified from Sternberg & Newell
1999; Schwarzer et al. 2003.)