Sedimentary Rocks Flashcards
Define sediments
Particles of minerals that often settle on the top of mineral beds.
Define Siliciclastic sediment
Grains of feldspar and quartz
Or basically minerals that have Si in formula
Define lithify
Hardening
Define compaction and cementation
Compaction- reduction in volume of sediments resulting from weight of newly deposited sediments above
Cementation- Sediment being “glued” together via mineralization, typically calcite and quartz from groundwater fluid
Formation of sedimentary rocks
Formed from sediment, deposited in water or air
Usually settles as layers or bedded
Define Carbonate sediments
Grains of calcite and dolomite
Or minerals that have C03 in the formula
Pyroclastic
Process of the formation of sedimentary rocks starts from what
Weathering and Erosion
Process of formation
Weathering —> transportation—>deposition and lithification *****in a hole or basin (lake or ocean basin
Sedimentary rocks constitute
Only 7% of the earths crust by volume however
Covers 75% of the earths surface
What are modes of Transportation of loose sediment
Wind, water, glacial ice
Coarsest particles are close to the surface
The greater the distance of transport, the smoother or more rounded grains become
What are the three main Types of sedimentary rocks
Clastic sediments
Biochemical (carbonate) sediments
Chemical sediments
Clastic sediments
Rocks made up of small fragmented pre-existing rocks. Are then naturally weathered and transported, ends with lithification. Clastic = Detrital
Biochemical sediments
Formed from organic processes that involve living organisms producing the sediments. E.g. Limestone & Dolostone
Chemical sediments
precipitated directly from water (evaporation)
Define lithification
Is the conversion of sediments into rock. The following diagenetic processes may be involved
Compaction
Cementation
Define diagenetic
Physical, chemical or biological alteration of sediments into sedimentary rock at relatively low temperatures and pressures
Sedimentary rock classification
Generally determined by size of grain and roundness
Location and ecological can also determine types
Clastic sedimentary rocks
Classical = detrial
Classified by size or particle
What is the Wentworth scale
Grain diameter
Angular and rounded sediments rocks
Breccia and conglomerate
What rock name is greater than .0625mm
Shale
What is the study of the provenance
reconstruct and to interpret the history of sediment from parent rocks at a source area
Biochemical sedimentary rocks traits
Primarily found in oceans
Limestone and Dolostone are the main rocks
They are precipitation of dissolved ions
Limestone
Composition of Calcium Carbonate
The primary source of calcite is marine organisms shells
Most important feature of carbonate rocks
Texture
Is it carbonate mud or carbonate mud with skeletal materials
Carbonate reefs
A reef complex on a carbonate shelf or platform,
Important setting of deposition of limestone
Define fore reef, test question***
A fore reef is a platform on the edge of a coral reef made up of mostly dead organisms and calcite
Where do coral reefs occur
Needs clear, warm, shallow water
Need water temperatures of 30 degrees
Atoll formation
1) Underwater volcano pierces ocean surface
2) Coral reef forms around thre volcanic island
3) Fringing reef surround the sinking island
4) Barrier reef protects newly formed lagoon
Chemical sedimentary rocks
Chemical sedimentary rock forms when mineral constituents in solution become supersaturated and inorganically precipitate.
Biochemical rock
Chert or Flint
Small particles of silica, often from shells of microscopic organisms like radiolarian
So chert is not a carbonate but a silica
Deep water oozes
Organic sedimentary rocks
Think coal. *****
Sedimentary structures
Layers = beds/strata
Graded bedding
changing (decreasing) energy = Fining up?
Formation of cross bedding and ripples ***test question
Asymmetrical ripples form in a unidirectional flow. Symmetrical ripples are the result of an oscillating back-and-forth flow typical of intertidal swash zones.
How much of the earths core is made up of sedimentary rocks*****test question
75%
What are the three main categories of sedimentary rocks ** test question
Silicilastic, biochemical and chemical
