Sedimentary Rocks

Sediment- From Latin - to settle

Fragments and precipitates that settle out of a fluid (water, ice, air)

75% of the continents are exposed sedimentary rock

Clastic Sediments

Low temperature minerals formed during weathering and transportation (mostly clay minerals) and those minerals which are most stable at the earth's surface (primarily Quartz) are eventually deposited and form clastic sedimentary deposits

Non-Clastic Sediments

Form by inorganic precipitation of dissolved chemical species

Clastic Grain Sizes

Boulder-bigger than 256mm (about football size/bigger)

Cobble- 64-256mm (roughly brick/baseball/softball size)

Pebble- 4-64mm (golfball sized)

Granule - 2-4mm (pea sized)

Sand- 1/16 - 2mm (uauslly quartz, sand is a size not material)

Silt- 1/16 - 1/256mm (too small to see but have gritty feel)

Clay - smaller than 1/256mm (clay used by itself is a size term, too small to see and won't feel grity)

Sand occurs usually...

Talus Slope + Scree

Silt and Clay are usually found...

Silt and clay are usually found mixed togethor, termed mud. Mud occurs in low energy environments where the water is mostly at a standstill.

- Deltaic swamp deposits

Conglomerate

composed of rounded rock or mineral fragments, usually poorly sorted

Breccia

Composed of generally angular rock or mineral fragments; usually poorly sorted

Clastic Coglomerate Sedimentary Rocks

Boulder Conglomerate - Bigger than 256mm

Cobble Conglomerate - 64-256mm

Pebble Conglomerate - 4-64mm

Granular Conglomerate - 2-4mm

Sandstone

(Clastic Sandstone Sedimentary Rocks)

Between 1/16 - 2mm, come from the weathering of feldspar

Sandstone Rocks

Quartz Sandstone

Arkose

Graywacke

Siltstone

(Clastic Siltstone Sedimentary Rocks)

Between 1/16 - 1/256 mm

Siltstone - generally massive rock composed of quartz and clays (Feels gritty)

Claystone

(Clastic Clay sedimentary rocks)

Smaller than 1/256 mm

Shale -Fissile

Claystone - Massive

Roundness

(Clast Property)

Measure of sharpness or corners (of a rock)

- Beaches have round grains

Round - smooth edged

Angular- Sharp corners

Measures energy put into rock during transportation and deposition

Sphericity

(clast Property)

measure of 3D shape

-Discoid - sheet like

-Rod like- shaped like a rod

-Spherical - sphere like

Helps to determine where they form

Sorting

(Clast Property)

measure of uniformity of grain size (how close all the grains are to the same size)

- Well-Sorted = Grains all the same size

- Poorly-Sorted = Grains are all different sizes

Measures energygoing into the rock during transportation and deposition

Distance Traveled vs Sorting and Rounding

More distance travelled the better the rounding and sorting

A sedimentary rock composed of angular pebbles...

A.  Conglomerate

B.  Breccia

C.  Arkose

D.  Anglestone

Well rounded and well sorted sand-sized grains in sandstone is suggestive of...

A.  Long distance of transport

B.  Deep water sedimentation

C.  Rapid Burial

D.  Transportation by glaciers

Chemical Sediments

(mineral composition and Rock)

   Mineral Composition                               Rock      

Calcite                                             Limestone

Gypsum                                            Rock Gypsum

Anhydrite                                          Anhydrite

Halite                                               Rock Salt

Silica (Chalcedony)                             Chert/Flint

Hematite                                           Ironstone

Limestone

(Texural Varieties)

Massive or Crystalline

Fossiliferous

Coquina

Travertine

tufa

Chalk

Lithographic

Marl

Coquina Limestone

shell hash, porous and lightweight (Spanish Forts used)

non-clastic

Travertine

Cave formations, (stagmites, staligtites, etc...)

Finelly banded rocks composed of crystalline or microcrystalline calcite

Non-clastic

Tufa

Spongy calcite deposits around springs

non=clastic

Gypsum

Forms when sea water evaporates

 - when above 75% of sea water evaporates it is gypsum precipitate

 - Temperature related

Massive rocks composed of crystalline gypsum

Caves made of gypsum - castile FM

non-clastic

Halite

Rock Salt

- mineral formed when 90% of sea water evaporates

non-clastic

Dolostone

Formed when ground water that is rich in magnesium percolates through Carbonate rocks (limestone) and chemically altered to a dense, massive lithology composed primarily of dolomite

The most abundant sedimentary rocks are...

A.  Limestones and Dolostones

B.  Sandstones and Conglomerates

C.  Evaporites

D.  Mudstones and Shales

Dolostone is formed by the addition of  ____ to calcite in limestone.

A.  Calcium

B.  Magnesium

C.  Iron

D.  Sodium

Coquina is formed of...

A.  Feldspar

B.  oolites

C.  Pebbles

D.  broken Shell fragments

The rock underlying campus, present in numerous outcrops, and the facing of many buildings on campus is...

A.  Granite

B.  Shale

C.  Limestone

D.  Sandstone

Playa lakes of the southwest United States are sites of deposition of...

A.  Evaporites

B.  Thick Limestone

C.  Ore grade iron deposits

D.  Varve Deposits

Coal

(Biochemical Rock)

Decayed plant matter

Carbon derived from plants

-the exception to the rule of rocks being made of minerals and being inorganic

-formed from swamp deposits, buried and dehydrated

Grades of Coal

Peat

Lignite

Bituminous

Anthracite

Lignite

low grade, soft and crumbly, brown coal

- High carbon content but still alot of water, Does not burn cleanly, still some plant remains

- used in east texas

Bituminous

dull black coal

- coal used in most industry

- still puts off smoke

Anthracite

high grade, black, shiny coal

- metamorphic rock (appalation Mnts)

- used for home heating not industry

 - lower E-content

HIGHEST GRADE OF COAL

Recrystallization

individual grains undergo solution and redeposition within the rock; some grains grow larger and interlock

EXAMPLE

Calcite in Limestone

Compaction

Small grains stick togethor without "glue"

-Effective in finegrained materials especially with large clay content

Common in shales and mudstones

Cementation

Secondary mineral fills pores to hold grains togethor

_--Iron oxide, silica, or calcite in sandstone

A sedimentary rock formed by accumulation of altered plant remains is...

A.  Shale

B.  Chert

C.  Coal

D.  Oil Shale

Clay particles stick togethor to form shales and mudstones by...

A.  Compaction

B.  Cementation

C.  Recrustallization

D.  Glycolation

The process by which dissolved mineral matter precipitates in the pore spaces of a sediment and binds it together by...

A.  Compaction

B.  Weathering

C.  Cementation

D.  Floccuation

The colors red, yellow, and brown in sedimentary rocks are produced by...

A.  Calcite

B.  Clays

C.  Organic material

D.  Iron oxides/hydroxides

Finely divided pyrites in shales colors the rock...

A.  Red

B.  Black

C.  Yellow

D.  Brown

Black in limestones is usually due to the presence of...

A.  Pyrite

B.  Carbon

C.  Hematite

D.  Magnetite

Which of the following is an inidcation of an alternating wet and dry environment such as a tidal flat?

A.  Mud Cracks

B.  Graded Bedding

C.  Cross-Bedding

D.  Grain Size

Diagenesis

changes that occur after sediment deposition

(what turns sediment into rock)

Minor mineral coloring component

Fe Oxide: yellow, brown, red

Fe Hydroxides: Greens and black

Quartz/Calcite: White

Carbon:  Black

Pyrite (fine-grained): Black

A sedimentary rock formed by accumulation of altered plant remains is...

A.  Shale

B.  Chert

C.  Coal

D.  oil Shale

Which of the following can be used to determine paleocurrent direction?

A.  Mud cracks

B.  graded bedding

C.  Cross-bedding

D.  Grain size

What sedimentary structures indicate current flow directions?

Cross bedding

Graded Bedding

Rythmic bedding

What sedimentary structures indicate which way is up in the sedimentary stack?

Fossils

Fossils: Any evidence of ancient life

Types

Unaltered remains

Altered remains

Trace fossils

Unaltered Remains

(fossils)

Soft Parts: frozen mammoths

Hard parts: teeth, bones, etc...

Altered Remains

(fossils)

Permmineralization: Petrification (bones, wood, etc)

  - filling pores with silica

Replacement

Carbonization:  organic content reduced to carbon content

Trace Fossils

Tracks/Trails

Burrows

Teeth Marks

True or false: The most common sedimentary rocks are mudstones and shales.

True or False: To be a fossil, an object must be part of the original organism.

The most abundant mineral at the earth's surface is....

A.  Clay

B.  Quartz

C.  Feldspar

D.  Calcite

Changes in sediment that occur after deposition are called...

A.  Maturation

B.  Induration

C.  Diagenesis

D.  Calibration

What fundamental concept states that a horizontal sequence of conformable sedimentary strata, each higher bed is younger than than the bed below.

A.  Law of Superposition

B.  Theory of correlative deposition

C.  Theory of superstition

D.  law of original correlation

Which of the following is a trace fossil?

A.  Shark tooth

B.  Frozen mammoth

C.  Foot prints

D.  Clam shell

Cross-Bedding

Sedimentary layers which accumulate along the front slope of migrating deposits during wind or current flow may develop at angles to the horizontal

- usually occur within large scale depositional units which are nearly horizontal

Graded Bedding

Sediment deposited during a sudden loss of current velocity may be sorted according to grain size during settling.

-coarser grained detrital grains are concentrated along the base of a depositional unit and systematically grade upward into finer grained material

Ripple Marks

Sediment transported by wind or water can be shaped by currents into small, wave-like structures.