Lecture 5 Flashcards
Tectonics
The forces controlling deformation or structural behavior of a large area of the Earth’s crust over a long period of
time.
Extrabasinal
Pre-existing rocks that are deposited. (Out of the basin)
Intrabasinal
Rocks that are deposited by chemical precipitates. Carbonate rocks and coal. (Inside the basin)
Continental
Environment on land
Transitional
Environment between ocean and land
Marine
Environment in ocean
Continental Shelf
The flooded edge of the continent.
Continental Slope
The steeper slope at edge of the continent.
turbidity current
A submarine avalanche of sediment and water that speeds down a submarine slope. (UNDERWATER AVALANCHE)
Continental rise
the gently sloping surface at the base of the continental slope
Deep Marine Realm
The deep ocean floor
Transitional Depositional Environments
Environments at or near the transition between the land and the sea.
Deltas
the flat, low-lying plain that sometimes forms at the mouth of a river from deposits of sediments.
Beaches and Barrier Islands
a coastal landforms
Lagoons/Estuaries
Bodies of water on the landward side of barrier islands
Fluvial Environments
Braided and meandering river and stream systemsy
Alluvial Fans
Fan-shaped
deposits at base
of mountains.
Playa lakes
shallow, temporary lakes that form in arid regions They periodically dry up as a result of evaporation
Till
Glacial deposit that contain large volumes of unsorted mixtures of
boulders, gravel, sand and
clay
Eolian Environments
Sediment deposition primarily governed by wind.
Color of Sedimentary Rocks (BLACK)
generally indicates the presence of organic carbon and/or iron in water(Anoxic) environment.
Color of Sedimentary Rocks (RED)
Indicates the presence of iron oxides. Unusually in well-oxygenated
continental sedimentary
environments.
Color of Sedimentary Rocks (GREEN AND GRAY)
Indicates the presence of iron, but in a reduced (rather than an oxidized) state.
Texture of rock (Fine-grained)
Indicate deposition in quiet water.
Does it take higher energy to transport large grain?
YES
Clasts
the larger grains in the rock (gravel, sand, silt)
Matrix
the fine-grained material surrounding clasts (often clay)
Cement
the “glue” that holds the rocks together
Sorting
distribution of grain sizes in a rock.
Ripple marks
Undulations of the sediment surface produced as wind or water moves across sand.
Symmetrical ripple marks
Ripple marks that are produced by waves
Asymmetric ripples
form in unidirectional currents
Mud cracks
A polygonal pattern of cracks produced on the surface of mud as it dries.
Planar bedding
Beds that are nearly horizontal
Major types of sandstone
Quartz sandstone, Arkose, Graywacke
Quartz sandstone
- Long time in the depositional basin
- Tectonically stable setting
- Shallow-water environments
Arkose
a granular sedimentary rock composed of quartz and feldspar or mica; a feldspathic sandstone.
Graywacke
a variety of argillaceous sandstone that is highly indurated and poorly sorted.
Limestone
Calcite / Aragonite
Dolostone
Dolomite
lime mud
sediment composed of calcium carbonate (CaCO3) derived from the skeletal remains of shelled organisms, coral, and calcareous algae and plankton
Claystone
A very fine-grained rock composed of clay minerals, mica, and quartz grains (<1/256 mm).
Shale
A very fine-grained rock composed of clay, mud, and silt.
Facies
The characteristics of a particular rock unit, which we can use to interpret the depositional environment. Each depositional environment grades laterally into other depositional environments.
transgression
A sea Level Rise
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.
Regression
sea level fall
Walther’s Law
Sedimentary environments that started out side-by-side will end up overlapping one another over time due to sea level change.
2 types of contacts between rocks
Conformable and Unconformable
Conformable Contacts
Conformable contacts between beds of sedimentary rocks may be either:
Abrupt or Gradational`
Unconformities
are surfaces which represent a gap in the geologic record
