1. 퇴적환경

2. Sedimentary Environments
퇴적물이 축적되는 장소.
Includes all of the physical, chemical, biological and geographic conditions under which sediments are deposited.
By comparing modern sedimentary deposits with ancient sedimentary rocks, the depositional conditions can be interpreted.

3. Sedimentary Environments
Use characteristics such as grain size, grain shape, composition, etc. to determine:
Origin
History
Method and Length of Transport
Nature and Environment of Deposition
Reconstruct Ancient Environments and Geographical Relationships

4. The Characteristics of a Sedimentary Environment Depend on:
Tectonic Setting
Rocks in the Source Area from which the Sediment is Derived
Climate (and its effect on weathering)
Method of Sediment Transport
Location of Deposition/Formation
Physical, Chemical, and Biological Processes in the Depositional Environment
Post-Depositional Processes of Lithification (Cementation, Compaction, Recrystallization)
Time

5. Depositional Environments
세 가지로 크게 구분:
해양환경(Marine Environment)s – Ocean
해안환경(Transitional Environments) – Along contact between ocean and land
육성환경(Continental Environments) – On land

6. 해양퇴적환경 Shallow (up to about 200 meters depth)
Land-derived sediments deposited on the continental shelf (coarser-grained – sands, silts, and clays).
Coral reefs
Deep (seaward of continental shelves)
Deep-sea sediments – fine-grained sediments (silts and clays) that have remained entrained in water column for long periods of time and transported great distances. Originate at continental shelf as the result of turbidity currents (deep-sea fans).

7. Marine Depositional Environments
Continental Shelf
Continental Slope
Continental Rise
Abyssal Plain

8. 대양저 퇴적물 Terrigenous Sediment
Mineral grains from weathered continental rocks.
Fine-grained sediment (clay, mud).
Accumulates slowly (5,000 to 50,000 years to deposit 1 cm).
Color may be black, red, or brown.

9. Marine Depositional Environments
Location
Water Depth
Slope
Width
Features
Sediments
Sedimentary Rocks
Continental Shelf
● Flooded edge of Continent.
● Flooding occurred when the glaciers melted about 10,000 years ago.
Shallow water (less than 200 m deep)
Relatively flat
(slope < 0.1º)
Up to 300 km wide
(averages 80 km wide)
● Exposed to waves, tides, and currents.
● Locally cut by submarine canyons (eroded by rivers during Ice Age low sea level stand).
● Covered by land derived detrital sediments pebbles, sand, silt, and clay.
● Larger sedimentary grains are deposited closer to shore.
● Coral reefs and carbonate sediments in tropical areas.
● Pebble Conglomerates, Sandstones, Siltstones, Mudstones, and Shales
● Organic Limestones – Fossiliferous Limestones, Oolitic Limestones, Coral Reef Limestones, and Coquina
● Evaporites in enclosed seas
Continental Slope
Seaward of continental shelf.
Steeper slope at edge of continent.
Deeper water
More steeply inclined.
(slope 3 – 6º)
~20 km wide
● Boundary between continental and oceanic crust.
● Rapid sediment transport from continental shelf down slope by dense, muddy turbidity currents.
● Sediments pass seaward to the continental rise and abyssal plain.
● Turbidites – Fining-upward sequence with a base of pebble conglomerates in a sandy matrix that grade up through coarse to medium sandstones, followed by silty sandstones, and finally siltstones and shales. This vertical succession of changing lithology is representative of strong to waning flow regime currents and their corresponding sedimentation.
Continental Rise
Base of the continental slope.
1,400 to 3,200 m
More gradual slope
Up to 100s of km wide
● Submarine fans form off submarine canyons.
● Turbidity currents form submarine fans off submarine canyons.
● Sediments pass seaward into the abyssal plain.
Abyssal Plain
Deep ocean floor
3 to 5 km+
(2 - 3 miles+)
Nearly flat NA
● Covered by very fine-grained detrital sediments and shells of microscopic organisms that have remained entrained in water column for long periods of time and transported great distances.
● Originate at continental shelf as the result of turbidity currents (deep-sea fans).
● Siltstones, Mudstones, and Shales
● Fine-grained Inorganic Limestones (Micritic and Crystalline)
● Fine-grained Organic Limestones – Foraminifera forming Chalk or Micritic Limestones
● Fine-grained Inorganic Siliceous Rocks – Diatoms forming Diatomite
● Chert (Radiolarians and Volcanic Ash)
Marine Depositional Environments
Shallow (up to about 200 meters depth)
Land-derived detrital sediments deposited on the continental shelf (coarser-grained – sands, silts, and clays forming pebble conglomerates, sandstones, siltstones, mudstones, and shales).
Organic Limestones – Fossiliferous Limestones, Oolitic Limestones, Coral Reef Limestones, and Coquina
Evaporites in enclosed seas
Deep (seaward of continental shelves)
Deep-sea sediments – fine-grained detrital sediments (silts and clays forming siltstones, musdtones, and shales) that have remained entrained in water column for long periods of time and transported great distances. Originate at continental shelf as the result of turbidity currents (deep-sea fans).
Fine-grained Inorganic Limestones (Micritic and Crystalline)
Fine-grained Organic Limestones – Foraminifera forming Chalk or Micritic Limestones
Fine-grained Inorganic Siliceous Rocks – Diatoms forming Diatomite
Chert (Radiolarians and Volcanic Ash)

10. 해안퇴적환경
Environments at or near the transition between the land and the sea.
Consist of land-derived sediments deposited on the continental shelf (coarser-grained – sands, silts, and clays).
Forming pebble conglomerates, sandstones, siltstones, mudstones, and shales.
Carbonates

11. Transitional Depositional Environments
Deltas
Beaches
Barrier Islands
Lagoons
Tidal Flats
Estuaries

12. Transitional Depositional Environments
Description
Location
Features
Sediments
Sedimentary Rocks
Deltas
● Fan-shaped accumulations of sediment.
● Forms where a river flows into a standing body of water, such as a lake or the sea.
● The delta builds seaward (or progrades) as sediment is deposited at the river mouth.
● Coarser sediment is deposited near the mouth of the river.
● Finer sediment is carried seaward and deposited in deeper water.
● Pebble Conglomerates, Sandstones, Siltstones, Mudstones, and Shales
Beaches and Barrier Islands
● A long, relatively narrow island running parallel to the mainland.
● Served to protect the coast from erosion by surf and tidal surges.
● Barrier Islands are separated from the mainland by a lagoon (or salt marsh)
● Exposed to wave energy
● Marine fauna
● Dominated by sand
● Associated with lagoon (or salt marsh) deposits
● Associated with tidal flat deposits
● Beaches – Quartz Sandstones, other sandstones, Conglomerates
● Barrier Islands – Quartz Sandstones
● Lagoons and Tidal Flats – Siltstones, Mudstones, and Shales
Lagoons
● Shallow bodies of water.
● Landward side of barrier islands.
● Also present behind reefs, or in the center of atolls.
● Protected from the pounding of the ocean waves by barrier islands.
● Contain finer sediment than the beaches and barrier islands (usually silt and clay)
● Siltstones, Mudstones, and Shales
Tidal Flats
● Nearly flat, low relief areas.
● Border lagoons, shorelines, and estuaries
● Periodically flooded and exposed by tides (usually twice each day)
● May be marshy, muddy, sandy or mixed sediment types (terrigenous or carbonate)
● Sandy Siltstones, Mudstones, and Shales
● Carbonates
● Laminations and ripples are common.
● Sediments are intensely burrowed.
● Stromatolites may be present (if conditions are appropriate)
Estuaries
● Mouth of a river drowned by the sea.
● Many estuaries formed due to sea level rise as glaciers melted at end of last Ice Age.
● Some formed due to tectonic subsidence.
● Brackish water (mixture of fresh and salt)
● May trap large volumes of sediment.
● Sand, silt, and clay may be deposited depending on energy level
● Sandstones, Siltstones, Mudstones, and Shales

13. Fan Delta
Bird-Foot Delta

14. 연안사주(Barrier Island Complex)
Subenvironments of a Barrier Island Complex

15. 조간대(Tidal Flats)

16. 강하구(Estuaries)
North Carolina's Neuse River Estuary

17. 육성환경
Continental environments are those environments which are present on the continents (as opposed to in the oceans).
Consist of land-derived sediments deposited in various sedimentary environments (boulders, pebbles, sands, silts, and clays).
Detrital sedimentary rocks – conglomerates, brecias, sandstones, siltstones, mudstones, and shales.
Inorganic Carbonates – hotspring and cave formations
Evaporites in desert climates

18. Continental Depositional Environments
Rivers or Fluvial Environments
Lacustrine (or Lake) Environments
Glacial Environments
Aeolian Environments

19. Continental Depositional Environments
Fluvial – dominated by erosion and deposition associated with streams.
Stream channel deposits, floodplains, terrace deposits, bars, alluvial fans, landslides/mass movement, swamps, meander scars, lakes
Land-derived sediments variable grain sizes – gravel, sands, silts, and clays

20. Lacustrine Environments (Lakes)
Filled with terrigenous, carbonate, or evaporitic sediments.
Sediments are typically fine-grained but may be coarse near the edges.
Fine sediment and organic matter settling in some lakes produced laminated oil shales.

21. Continental Depositional Environments
Glacial – dominated by erosion and deposition associated with glaciers.
Terminal, lateral, medial, ground, recessional, and end moraines; outwash plains; drumlins; eskers
Land-derived sediments variable grain sizes – gravel, sands, silts, and clays

22. Continental Depositional Environments
Eolian (풍성) – dominated by erosion and deposition associated with wind.
Sand dunes(사구)
Land-derived sediments finer-grained – sands and silts

23. 퇴적구조

24. 퇴적구조 Sedimentary Structures:
Features visible at the scale of an outcrop.
Formed at the time of deposition or shortly thereafter, but before lithification.
Manifestations of the physical and biological processes that operated in depositional environments.
May be created during deposition by the water or wind which moves the sediment.
May form after deposition – such as footprints, worm trails, or mudcracks.
Provide information about the environmental conditions under which the sediment was deposited.
Some structures form in quiet water under low energy conditions, whereas others form in moving water or high energy conditions.

25. Sedimentary Structures
층리구조(Stratification):
Layering or Bedding
The most obvious feature of sedimentary rocks.
The layers (or beds or strata) are visible because of differences in the color, texture, or composition of adjacent beds.

26. 층리(Bedding) Sedimentary rocks generally have bedding or stratification
Individual layers less than 1 cm thick are laminations
common in mudrocks
Beds are thicker than 1 cm
common in rocks with coarser grains

27. 점이층리(Graded Bedding)
Some beds show an upward gradual decrease in grain size, known as graded bedding
Graded bedding is common in turbidity current (저탁류) deposits
which form when sediment-water mixtures flow along the seafloor
As they slow,
the largest particles settle out
then smaller ones
저탁암(turbidite)

28. Graded Bedding

29. 사층리(Cross-Bedding) or 사교층리(Cross-Stratification)
Cross-bedding forms when layers come to rest
at an angle to the surface
upon which they accumulate
as on the downwind side of a sand dune
Cross-beds result from transport
by either water or wind
The beds are inclined or dip downward
in the direction of the prevailing current
They indicate ancient current directions,
or paleocurrents
They are useful for relative dating
of deformed sedimentary rocks

30. Cross-Bedding or Cross-Stratification
Get Animation of Cross-Bedding Formation

31. 판상사층리(Tabular Cross-Bedding)
Tabular cross-bedding forms by deposition on sand waves
Tabular cross-bedding in the Upper Cretaceous Two Medicine Formation in Montana

32. Tabular Cross-Bedding

33. 곡형사층리(Trough Cross-Bedding)
Trough cross-bedding formed by migrating dunes
Trough cross-beds in the Pliocene Six Mile Creek Formation, Montana

34. 연흔(Ripple Marks) Small-scale alternating ridges and troughs
known as ripple marks are common
on bedding planes, especially in sandstone
Current Ripple Marks
form in response to water or wind currents
flowing in one direction
and have asymmetric profiles allowing geologists
to determine paleocurrent directions
Wave-Formed Ripple Marks
result from the to-and-fro motion of waves
tend to be symmetrical
Useful for relative dating of deformed sedimentary rocks.

35. 유수연흔(Current Ripple Marks)
Ripples with an asymmetrical shape
In the close-up of one ripple,
the internal structure
shows small-scale cross-bedding
The photo shows current ripples
that formed in a small stream channel
with flow from right to left

36. Current Ripple Marks

37. 파동연흔(Wave-Formed Ripples)
As the waves wash back and forth,
symmetrical ripples form
The photo shows wave-formed ripple marks
in shallow seawater

38. 건열(Mud Cracks) When clay-rich sediments dry, they shrink
and crack into polygonal patterns
bounded by fractures called mud cracks
Mud cracks require wetting and drying to form,
as along a lakeshore
or a river flood plain
or where mud is exposed at low tide along a seashore

39. Ancient Mud Cracks Mud cracks in ancient rocks
Mud cracks typically fill in
with sediment
when they are preserved as seen here

40. Mud Cracks
A polygonal pattern of cracks produced on the surface of mud as it dries

41. Biogenic Sedimentary Structures
Biogenic Sedimentary Structures include:
Tracks
Burrows
Trails
Called Trace Fossils(생흔화석)
Extensive burrowing by organisms
is called bioturbation
It may alter sediments so thoroughly
that other structures are disrupted or destroyed.

42. 생교란작용(Bioturbation) U-shaped Burrows Vertical Burrows
Get animation of animals bioturbating.
Vertical Burrows

43. Bioturbation
Vertical, dark-colored areas in this rock are sediment-filled burrows

44. 퇴적상(Sedimentary Facies)

45. Sedimentary Facies A sedimentary facies is a body of sediment
with distinctive
physical, chemical, and biological attributes
deposited side-by-side
with other sediments in different environments
can be used to interpret the depositional environment
Every depositional environment puts a distinctive imprint on the sediment, making a particular facies.

46. Each depositional environment grades laterally into other depositional environments.
Figure (p. 101) Sedimentary facies (lithofacies) developed in the sea adjacent to a land area. The upper surface of the diagram shows present-day facies, whereas the front face shows the shifting of facies through time. Notice that bottom-dwelling organisms also differ in environments having different bottom sediment and water depth.

47. Facies and Sea Level Changes
A marine transgression (해침) occurs when sea level rises with respect to the land.
During a marine transgression,
the shoreline migrates landward
and the environments paralleling the shoreline migrate landward as the sea progressively covers more and more of a continent.
Each laterally adjacent depositional environment produces a sedimentary facies.
During a transgression, the facies forming offshore become superposed upon facies deposited in nearshore environments.

48. Facies and Sea Level Changes
A transgression produces a fining-upward (deepening-upward) sequence of facies.
Finer-grained (deeper water) facies overlie coarser-grained (shallower water) facies.
Sometimes called an onlap sequence.

49. Marine Transgression The rocks of each facies become younger
in a landward direction during a marine transgression
One body of rock with the same attributes
(a facies) was deposited gradually at different times
in different places so it is time transgressive
meaning the ages vary from place to place
Younger Shale
PLAY ANIMATION
Older Shale

50. Sedimentation During a Transgression Produces an Onlap Sequence

51. Causes of Transgressions
Melting of polar ice caps.
Displacement of ocean water by undersea volcanism.
Localized sinking or subsidence of the land in coastal areas.

52. Regressions
A marine regression(해퇴) occurs when sea level goes down with respect to the land.
During a marine regression,
the shoreline migrates seaward
and the environments paralleling the shoreline migrate seaward as the sea progressively migrates off the continent
A regression produces a coarsening upward (shallowing-upward) sequence of facies.
Coarser-grained (shallower water) facies overlie finer-grained (deeper water) facies.
This is sometimes called an offlap sequence.

53. Marine Regression Older Shale A marine regression
is the opposite of a marine transgression
It yields a vertical sequence
with nearshore facies overlying offshore facies
and rock units become younger in the seaward direction
PLAY ANIMATION
Younger Shale

54. Sedimentation During a Regression Produces an Offlap Sequence

55. Causes of Regressions Buildup of ice in the polar ice caps.
Formation of glaciers.
Localized uplift of the land in coastal areas.

56. Figure (p. 103) A rise in sea level will affect a far greater area along low-lying coastlines than along coastlines composed of highlands that rise steeply adjacent to the sea.

57. What if the ice on Earth melted?

58. Recent Sea Level Curve