Chapter 6 Flashcards
particular sites where sediment
accumulates and builds a rock.
Sedimentary depositional environments
Most sedimentary rocks came from loose?
loose
grains of sediment
the collective name for loose, solid particles?
Sediment
Sediments are said to be ____________, which means that the grains are separate, or unattached to one another.
unconsolidated
themovement of eroded material from one place to another?
transportation
a key phase in the process of
erosion, where particles that have been eroded from their original location are moved to a new area by natural forces?
transportation of
sediments
Mechanism of sediment transportation are?
suspension, saltation, traction, and solution.
the grinding away of sharp edges and corners of rock fragments during transportation.
Rounding
It occurs in sand and gravel as rivers, glaciers, or waves cause particles to hit and scrape to one another or against a rock surface.
Rounding
process by which sediment grains are selected and separated according to grain size by the agents of transportation (wind, running water)
sorting
are considered as well-sorted when the grains are nearly all the same size.
sediments
occurs when transported
material settles or comes to rest.
Deposition
location in which deposition occurs (ex. Deep seafloor, desert valley, river channel, coral reef, lake bottom, beach, and sand dunes).
Environment of deposition
a geomorphic unit in which deposition takes places.
depositional environment
_________ are recognized by features preserved in ancient sediments.
Geomorphic units
____________ are depressions where sediments are deposited.
Depositional Environments
The layers of sediment that accumulate in each type of depositional environment have ______________, which provide important information regarding the geologic history of an area.
distinctive characteristics
These are environments which are present on the continents, such as ailuvial fans, fluvial environments (rivers), lacustrine environments (lakes), aeolian or eolian environments (deserts), and paludal environments (swamps).
Continental Environments
These are fan-shaped deposits formed at the base of mountains where rainfall is infrequent but torrential, and erosion is rapid.
Alluvial Fan
____________ sediment is
typically coarse, poorly- sorted
gravel and sand.
Alluvial Fan
Channel deposits consist of ?
coarse, rounded gravel, and sand.
Bars are made of?
sand or gravel
Levees are made of?
fine sand or silt
River channels is typically contains?
cross-beds and current ripple marks
They may be large or small, shailow or deep, fresh water or salt water, and filled with terrigenous, carbonate, or evaporite sediments.
Lakes (Lacustrine Environment)
_________ is deposits thin-bedded
shales, silt, and clay characterized
by mud cracks and fossil footprints of animals.
Floodplains
Fine sediment and organic matter settling in some lakes produced _____________-
laminated oil shales.
This type of depositional environment can host oil and gas reservoirs, especially in rift basins.
Lakes (Lacustrine Environment).
These are areas with little or no rainfall during the year.
Deserts (Aeolian or Eolian
Environments)
It usually contains vast areas
where sand is deposited in dunes.
Deserts (Aeolian or Eolian
Environments).
are well sorted, well rounded, and frosted or polished, without associated gravel or clay.
Dune sands
Sandstones from aeolian
environments can be excellent
reservoir rocks due to their high ____________
porosity and permeability.
These are areas of standing water
with trees.
Swamps (Paludal Environment)
Decaying plant matter accumulates to form peat, which
may eventually become _____
coal
Found in regions influenced by glaciers.
Glacial Environments
These sediments can be significant
for understanding past climates and glacial influences on sediment
distribution.
till, outwash sands, and glacial lakes deposits
These are environments which include deltas, beaches and barrier islands, lagoons, salt marshes, and tidal flats.
Transitional Environments
________ are low-lying areas that are alternately covered by water and exposed to the air each day.
Tidal flats
________ are fan-shaped deposits of sediment, formed where a river flows into a standing body of water, such as a lake or sea.
Delta
Contains a great variety of sub-environments but are generally made up of thick sequences of siltstones and shale, marked by low-angle cross bedding.
delta
__________ shoreline deposits exposed to wave energy and dominated by sand with a marine fauna.
beaches
an elongate bar of sand built by wave action.
Barrier Island
They deposit well-sorted quartz sandstones with well-rounded grains.
Barrier Island
Barrier Island is characterized by:
cross beddings and marine fossils
These are bodies of water on the landward side of barrier islands.
Lagoons
They are protected from the pounding of the ocean waves by the barrier islands, and contain finer sediment than the beaches (usually silt and mud).
Lagoons
______________________, cut by tidal channels of coarsed sand and containing marine fossils are deposited in lagoons.
Fine-grained dark shale
These are in the seas or oceans.
Marine Environment
Marine environments include:
reefs,
the continental shelf
slope,
rise, and
abyssal plain.
can host extensive hydrocarbon reservoirs, particulariy in continental shelf and slope settings where organic-rich source rocks are present.
Marine Environment
________ often form significant source and reservoir rocks due to their extensive areal distribution.
Marine Environment
______________ are nearly flat, gentle sloping edge of the continent that extends under the ocean.
Shallow marine clastic
____________ is the flooded edge of the continent.
Continental shelf
The continental shelves are exposed to ___________.
waves, tides, and currents.
It is relatively flat (with a slope of less than ___), shallow (less than ____________).
0.1° , 200 m or 600 ft deep
_____________ are located seaward of the continental shelf.
continental slope and continental rise
The continental slope is the steep (_______) “drop-off’ at the edge of the continent.
5-25°
The ________ passes seaward into the continental rise, which has a more gradual slope.
continental slope
The ________ is at the base of the continental slope, where thick accumulations of sediment are deposited.
continental rise
Shale and graywacke sandstones are deposited in the deep ocean floor.
Deep Marine Environment
_____________ are deposited by turbidity currents and typically contains graded beds.
Graywackes
The _____________________ are reflected by the types of sediment that accumulate and thus their potential to contain resources.
depositional environments
__________ provide direct physical evidence of the subsurface geology.
Core Samples
Examine the rock types and their characteristics (e.g., sandstones, shales, limestones).
Lithology
Look for features such as cross-bedding, ripple marks, and graded bedding.
Sedimentary Structures
Assess the grain size and sorting of the sediment.
Grain Size and Sorting
Identify fossils or biogenic structures.
Biological Indicators
Marine environments might contain __________
marine fossils
freshwater environments may have _____________________.
freshwater fossils or plant material.
Examine how the lithology and sedimentary structures change vertically and laterally within the core.
Facies Changes
Look for signs of diagenesis, such as cementation and mineral alteration.
Post-Depositional Changes
___________________ can affect reservoir quality and provide clues about past environmental conditions.
Diagenetic features
Case Studies on Real-world examples
Deltaic and shallow marine deposits in the North Sea basin have been extensively studied for oil and gas exploration.
The North Sea
Case Studies on Real-world examples
Fluvial, deltaic, and marine deposits in the Permian Basin of West Texas provide diverse reservoir opportunities.
The Permian Basin
Case Studies on Real-world examples
In this evaporative environment, salt and other evaporites form significant reservoirs.
The Great Salt Lake:
