TYPES OF SEDIMENTARY ENVIRONMENTS

1. SEDIMENTARY ENVIRONMENTS
• A sedimentary environment is an area of the earth's surface
where sediment is deposited. It can be distinguished from
other areas on the basis of its physical, chemical, and
biological characteristics.

2. CONTINENTAL ENVIRONMENTS
• Continental environments are those environments which
are present on the continents and include:
1. Fluvial (Rivers)
2. Lacustrine (Lakes)
3. Paludal (Swamps)
4. Glacial
5. Desert

3. TYPES OF SEDIMENTARY ENVIRONMENTS
• There are three main types of sedimentary environments:
1. Continental
2. Marine
3. Transitional

4. 1. Meandering streams
• Have a single channel with a sinuous pattern and a broad
floodplain.
• The most common pattern on floodplains.
• Meandering channels form where streams are flowing over a
relatively flat landscape.
• Associated facies are point bar, oxbow lakes, levees, crevasse
splay and floodplain.
Meandering river

5. Fluvial (Rivers)
• The river channel includes two main types:
• Meandering stream.
• Braided stream.
Meandering stream Braided stream

6. Point bar
• It develops where stream flow is locally reduced because
of friction and reduced water depth.
• The eroded materials from the cut banks at the outside
bend; will be deposited as point bars that lie at inside
bend.
• Point bar composed of cross-bedded sand.

7. Oxbow lake
• As the channel migrates, parts of it may become abandoned and
left behind as oxbow lakes which made up of fine-grained sand to
silt (lake sediments).
Point bar
deposits
Cut bank
erosion
Meander
loop

8. Levees
• They are ridges found
along the sides of the
stream channel and
composed of silt and fine
sand.

9. Crevasse splay
• The crevasse splay will be formed when an overloaded
stream breaks a natural or artificial levee and deposits
sediments on a flood plain. It made up of sands, fining
upwards to a mud.
Crevasse splay
Crevasse splay

10. Floodplain
• It is a plain that subjected to periodic flooding and
composed of fine-grained materials which are very fertile
soil.
Flood plain

11. Meandering river fining upward sequence

12. Sand dunes
• They are the most common aeolian landforms; their
geometry and resulting sedimentary structures depend
primarily on sediment supply and prevailing wind
direction.
• Eolian sand sheets develop when sediment supply is
limited and are characterized by planar stratification.
• Vegetation can contribute to dune formation under such
circumstances.

13. Sand dunes
• Desert dune sands are characterized by a grain size of fine
to coarse sand (0.1-1.00 mm), good sorting and a negative
skewness.
• Characterized by large-scale, high angle cross bedding.
• The interdune areas are filled with lag deposits and
sabkha.

14. Sand dunes
• Geomorphologically, sand dunes include
• Barchan dunes.
• Transverse dunes.
• Linear (longitudinal) dunes.
• Star dunes.

15. Alluvial fans
– It is a fan shaped deposits generally form at the margin
of an uplift area, such as a mountain range front.
– Streams in narrow valley (Canyon), carrying recently
eroded material, and spread out their sediment load
(alluvium) onto the plain at the base of the upland
where the slope suddenly flattens.
– They most commonly form under semi-arid and glacial
climate conditions.

16. Alluvial fans
– The deposits are generally texturally and
compositionally immature.
– The sediments become finer grained away from the
apex of the fan.
– Fans generally do not form as a single body, but are
built up over time as a complex of coalescing and
overlapping deposits.
– Coalescence of alluvial fans forms Bajada.
– They consist of stream-flow and debris-flow or mud-
flow deposits.

17. MARINE ENVIRONMENTS
–Marine environments are
those environments in seas or
oceans.
– marine environments may be
shallow or deep.
–The shallow marine
environments include reefs
and continental shelf.
– The deep marine
environments are continental
slope, continental rise and
abyssal plain.
Reefs

18. Reefs
–They are mound-like, wave resistant structures made up of
calcareous skeletons of organisms such as corals, bryozoa,
etc.
–Reefs are growing in the photic zone of warm, clear,
shallow seas.

19. Reefs
–Ancient reefs buried within stratigraphic sections are of
considerable interest to geologists because they provide
paleoenvironmental information about the location in
Earth's history.
–In addition, reef structures within a sequence of
sedimentary rocks provide a discontinuity which may
serve as a trap for oil or ore deposits.

20. Reefs
–The three principal reef types are:
• Fringing reef: a reef that is directly attached to a
shore or borders it with an intervening shallow
channel or lagoon.
• Barrier reef: a reef separated from a mainland or
island shore by a deep lagoon.
• Atoll: is an annular reef enclosing a lagoon.

21. The Continental Shelf (Continental Platform)
– The continental shelf is the flooded edge of the continent and lies between
shoreline and continental slope.
– This shelf is relatively flat (slope < 0.1o), shallow (less than 200 m), and may
be up to hundreds of miles wide.
– Continental shelves are exposed to waves, tides, and currents.
– The shelf area is commonly subdivided (toward deep water) into three zones
each with their specific geomorphology and marine biology.
– The inner continental shelf (neiritic zone).
– The mid continental shelf.
– The outer continental shelf.

22. The Continental Shelf (Continental Platform)
– The continental shelves are commonly covered by terrigenous sediments, in
addition to non-clastic sediments such as carbonates, phosphates.
– Terrigenous sediments usually become increasingly fine with distance from the
shoreline whereas, sand is limited to shallow, wave-agitated waters, while silt
and clays are deposited in quieter, deep water far offshore.
– The carbonates of the continental shelf (carbonate factory) are rich in algae,
larger foraminfera etc..
– These shelf sediments accumulate at an average rate of 30 cm/1000 years, this
rate is much faster than that for deep-sea pelagic sediments.

23. The continental slope and continental rise
– They are located seaward of the continental shelf and may reach a depth of
4000 m.
– The continental slope is the steep (5- 25o) part at the edge of the continent.
– The continental slope passes seaward into the continental rise, which has a
more gradual slope.
– The continental rise is the site of deposition of thick accumulations of
sediment, much of which is in submarine fans, deposited by turbidity currents.
– Submarine fans are essentially turbidites dumps most typically at the mouths of
the submarine canyons that feed them.

24. The abyssal plain
– It is flat or very gently sloping areas of the deep ocean basin floor.
– It covered by very fine-grained sediment, consisting primarily of clays and the
shells of microscopic organisms (such as small foraminifera, radiolarians, and
diatoms).

25. The abyssal plain
– The carbonate rocks of the deep marine water (above the CCD) are formed
mainly by the accumulation of tests such as planktonic foraminifera.
– The Carbonate Compensation Depth (CCD) is the depth below which no
carbonate sediments can accumulate.
– Below CCD, the deep marine environments are cold, with high PCo2, due to
the decay of the few organisms that may be buried there.
– Therefore, this environment is not suitable for the direct precipitation of
carbonates from seawater. As a matter of fact, below the depth of about 5000
m, no carbonate sediments can accumulate.

26. TRANSITIONAL ENVIRONMENTS
– Transitional environments are those environments at or near the transition
between the land and sea.
– These environments include delta, tidal flats, beach, barrier islands and lagoons
Delta
Tidal Flat
Lagoon
Barrier Island
Beach

27. Delta
– A delta forms where a river transporting significant quantities of sediment
enters a receiving basin such as ocean or other body of water.
– Name from the Greek letter ‘∆’, from the shape of the Nile Delta.

28. Delta
– Delta is subdivided into the delta plain, delta front and prodelta:
1. The delta plain
comprises a flat area dominated by alluvial deposition. The resulting
vertical deposits include alluvial channel fills, overbank muds and the
fine-grained sediment infill of lakes.
2. The delta front
is located at the distal edge of the delta plain; sediments are deposited in
mouth bars as the rivers emerge into the sea.
3. The prodelta
is most distal part of the delta whereas the finest grained sediments are
deposited.

29. Delta
– Controls on delta environments and facies.