Tidal Flats
Tidal Flats - deposits within the tidal zone
muddy
organic matter-rich
intertidal zone - between mean high and low tides
supratidal zone - above mean high tide
Environments (Fig10.47, p. 369)
a. subtidal
b. intertidal
sand flats
mixed flats
mud flats
channels
levees
ponds
c. supratidal
marsh
Successions (Fig. 10.51, p. 373)
a. fluctuating hydraulic conditions
flaser - laterally continuous mud between crossbedded sand/silt
preservation favorable for mud
lenticular - laterally discontinuous mud between crossbedded
sand/silt
preservation favorable for mud
b. bidirectional symmetrical ripples
constructional processes
destructional processes (Fig. 10.50, p. 374)
c. upward shallowing
mud cracks
evaporites
Marine Clastic Shelf Facies
Overview of the major marine environments (Fig. 11.1, p. 379)
briefly go through each environment and geologic setting
a. shelf
b. slope
c. abyssal plain
Shelf (Neritic) Environments
a. pericontinental (Fig. 11.3, p. 380)
b. epicontinental (epeiric)
c. beach - shoreface - inner shelf - outer shelf - shelf break
(Fig. 12.3, p. 421)
d. "reef"
- from the Norse "rif" meaning rib, used to describe
arcuate breakers
- topographic relief on the seafloor
- wave resistant
- modifiers in classifications (i.e. coral reef)
e. relict shelf sediments and topography - from the pre-exisiting
shelf
f. marine fossils
g. crossbedding generally 20 to 25o dip
Types of Shelves
a. tidal-dominated (17%)
diurnal - 2 high, 2 low - Bay of Fundy, Nova Scotia
semidiurnal - 1 high, 1 low, Gulf of Mexico
mixed tides - California coast Pacific Ocean
tidal bulge - sun/moon gravitational attraction, rotates around
amphidromic
sediments and structures = Fig. 12.8, p. 430
b. storm-dominated shelves (80%)
fair weather wave base = 10 to 15 m
storm wave base = as much as 200 m
wind-forced currents with Coriolis deflections
onshore = coastal setup
offshore = geostrophic or longshore current
sediments and structures = tempestites with hummocky Xstratification
c. ocean current shelves (3%)
density currents - due to changes in salinity, temperature or
suspension
nepheloid layer
sediments and structures = mostly relict sediments