Siliciclastic Marine Environments

1
Siliciclastic Marine Environments
2
Ocean Realm
Neritic Zone Continental Shelf active vs.
passive margins Oceanic zone Continental Slope,
continental rise, Abyssal plain Oceanic ridge,
trench
Figure 10.1
3
Shelf Environment
Pericontinental or marginal sea Epicontinental or
epeiric sea
Figure 10.2
4
Shelf physiography
Figure 10.3
Inner Shelf dominated by tidal, wind-driven,
and storm-wave processes. Middle Shelf Outer
Shelf deep water, 200 m water depth
5
Shelf Sediments

• Relict sediments sediment deposited on the
  shelf by other than marine deposition, when sea
  level was much lower. Glacial sediments, fluvial
  sediments
• Weather-dominated 80
• Wave-dominated
• Storm-dominated
• Tide-dominated 17
• Intruding ocean currents 3

6
Shelf transport processes
Figure 10.5
7
Wave- and Storm Dominated Shelves

• Fair-weather waves
• Wave base
• Period of the wave number of waves passing a
  give point in a unit of time, i.e. waves/minute
• Swells
• Low-relief, long-period, long-wavelength waves,
  generated by storms
• Wind-forced currents
• Unidirectional currents generated by wind shear
  stress

8
Shelf flows

• Sediment plumes
• Buoyant plumes hypopycnal flow
• Underflows bottom plumes hyperpycnal flow
• Nepheloid flow
• Turbid body of suspended sediment, may reach
  heights of several 100 meters above the seafloor.
  More dense than water, but not dense enough to
  sink rapidly, remain suspended for long periods
  of time, days to weeks

9
Shelf Sediments

• Shelf sand ridges elongate, coastal- to
  shelf-sand bodies, lengths of 10 km, heights or
  20 of the water depth.
• Storm layers hummocky cross-stratification
• Tempestites

10
Tempestites

• pre-depositional high-energy event in the form of
  a scour or erosional surface down into
  pre-existing shelf muds,
• a massive normally graded, fining upward skeletal
  shell-bed representing initial deposition from
  traction bed loads followed by less-dense
  sediments from a quieting turbulent flow regime,
• a coarse-to-fine grained, planar laminated
  horizon deposited during the initial change to
  laminar, non-turbulent lower energy flows,
• hummocky cross-stratified horizons resulting from
  shutdown in laminar, unidirectional flows and
  residual interactions between storm waves and
  bottom currents,
• another layer of planar laminated fine-sands
  deposited as a result of rapid deposition during
  storm waning period, and
• wave-rippled intervals reflecting last storm
  energy dissipation

11
Resource of more information

• http//www.uic.edu/classes/geol/eaes455/EaES455-6.
  ppt

12
Tide-dominated shelves

• Asymmetry due to velocity differences
• Flood-tide
• Ebb-tide
• Tidal rythmites or tidalites
• Sand mud laminae, mud deposited on top during
  standstill, with sand deposited during higher
  energy flow
• Tidal-dominated shelves characterized by sand
  bodies of various types and sizes, Figure 10.8

13
Biological Activity on shelves
14
Shelf Sequences
Figure 10.10
15
Oceanic Environment

• Deep-water
• Continental Slope
• Continental Rise
• Abyssal Plain

16
Deep marine environments
Figure 10.12
17
Continental Slope

• Submarine canyons
• Turbidity currents
• Bouma Sequence

18
Turbidity Current

• Submarine landslide
• Earthquake-triggered
• Autosuspension dynamic equilibrium of
  suspension
• Low-density flows less than 20 to 30 percent
  grains, mainly silt, clay and fine sand
• High-denisty flows contain greater
  concentrations, contain coarse-grained sediments,
  coarse sand, pebbles to cobble sized clasts as
  well as fine sediment

19
Turbidity Current
20
Turbidity Current Deposits

• Turbidites
• High-density flow thick-bedded turbidite,
  graded bedding, coarse grained sediments
• Low-density flow thin-bedded turbidite,
  laminations, cross-bedding, etc.

21
Bouma Sequence
22
Bouma Sequence

• A graded or massive sandstone
• B parallel laminated sandstone
• C ripple cross-laminated fine sandstone
• D faint parallel laminations of silt and mud
• Not always separated from E.
• E pelitic (argillaceous, mudstone) division,
  partly deposited by the turbidity current and
  partly hemipelagic

23
Hypothetical sequence of three turbidites
Hsu claimed that Bouma D rarely occurs in most
turbidites
24
Deep-Sea processes
Figure 10.14
25
Deep-sea sediment inputs

• Wind Transport
• Eolian
• Surface current transport
• Fluvial
• Glacial
• Coastal
• Biological productivity
• Pelagic processes planktonic organisms
• Pelagic rain - oozes
• Chemogenic processes

26
Deep-sea sediments

• Terrigenous
• Hemipelagic mud
• Turbidites flysch facies sandstone, marls,
  shales and clays
• Contourites
• Glacial
• Slump and slide deposits
• Pelagic
• Calcareous
• Silicious
• Pelagic muds
• Allochthonous deep-water carbonates
  re-transported from the shelf
• Table 10.1

27
Distribution of deep-sea sediments
Figure 10.21