Sedimentary Rocks

47
SEDIMENTARY ROCKS A. Sediment Source and History B. Formation of Sedimentary Rocks C. Types of Sedimentary Rocks D. Sedimentary Structures and Environments

description

A. Sediment Source and History B. Formation of Sedimentary Rocks C . Types of Sedimentary Rocks D. Sedimentary Structures and Environments. Sedimentary Rocks. - PowerPoint PPT Presentation

Transcript of Sedimentary Rocks

Page 1: Sedimentary  Rocks

SEDIMENTARY ROCKS

A. Sediment Source and History

B. Formation of Sedimentary Rocks C. Types of Sedimentary Rocks D. Sedimentary Structures and Environments

Page 2: Sedimentary  Rocks

SEDIMENTARY ROCKS These are composed of particles derived from

pre-existing rocks or by the crystallization of minerals that were held in solutions.

A general characteristic of this group is the layering or stratification.

Page 3: Sedimentary  Rocks

Type of Sedimentary Rocks Clastic Sedimentary are composed of

particles of pre-existing rocks. These fragments show evidence of transport – rounding of the grains and size sorting.

Chemical sedimentary rocks are the result of either precipitation of solids from solutions (like salt from water) or by organic process, like shells from marine organisms.

Page 4: Sedimentary  Rocks

Recipe for Sedimentary Rocks Sediment

Clasts: mineral particles from weathering of parent rock

Bioclasts: Shell and coral fragments (calcite or silica)

Chemical Precipitate: (calcite, silica, salts) Accumulation and Preservation

Sedimentation > Erosion Lithification

Compaction Cementation

B. Compaction

C. Cementation

A. After DepositionOverburden

compacts and reduces pore space

Cement from dissolved ions fills some porespace

Page 5: Sedimentary  Rocks

Creation of Clastic Sedimentary Rocks

Page 6: Sedimentary  Rocks

Sediment History

Talus slopes Mtn. Streams Beaches Oceans Alluvial Fans Rivers Delta (Plains)

Effects: Rounding, Size, Sorting and Mineralalogy

Page 7: Sedimentary  Rocks
Page 8: Sedimentary  Rocks

Clastic Sedimentary Rock Classification (Indicates History and Environment)

Rock Fragments

Unstable Minerals

More Stable Minerals Quartz

Angular Rounded Sub-Angular Rounded

Gravel (and Sand), Poorly Sorted

Sand and Silt, Poorly Sorted

Sand,Well Sorted

Mountains Cliffs, Glaciers

Mountain Streams

Rivers, (Flood Plains)

Beachesand Dunes

Breccia Conglomerate Arkose Quartz Sandstone

Clast Composition

Clast Shape

Clast Size and Sorting

Depositional Environment

Rock Type

Increasing duration of weathering and winnowing out of silt and Clay sized particles (predominantly clay minerals)

Immature Mature

Page 9: Sedimentary  Rocks

Mud

Clastic Particle Sizes (Wentworth Scale)

Example (mm) (Ø)

Bowling Ball 256 -8

Pool Ball 64 -6

Buck Shot 2 -1

Powder /16 4

1/256 8

BoulderCobblePebbleSandSiltClay*

*very small particles are usually clay minerals

GravelKehew, Table 4-3

Sand

Page 10: Sedimentary  Rocks

Talus Slopes

1. Gravel (boulders, cobbles etc.)

2. Poorly sorted3. Angular4. Fragments of rocks

and minerals

Page 11: Sedimentary  Rocks

Mountain Stream (Upstream)

1. Gravel (Cobbles, Pebbles etc.)

2. Poorly sorted3. Sub-angular

(Somewhat rounded)

4. Fragments of Rocks and minerals

Page 12: Sedimentary  Rocks

Mountain Stream (Downstream)

1. Gravel (Cobbles, Pebbles etc.)

2. Poorly sorted3. Rounded4. Fragments of

Rocks and minerals

Page 13: Sedimentary  Rocks

Alluvial Fans

1. Sand2. Poorly Sorted3. Sub-angular4. Many minerals

Page 14: Sedimentary  Rocks

River in the Plains

1. Sand2. Somewhat

Sorted3. Sub-angular4. Many minerals

Page 15: Sedimentary  Rocks

Quartz Sandstone: From Beaches and/or Dunes

Page 16: Sedimentary  Rocks

Delta Silt and Clay i.e., MudDeep Sea (Lakes, Oceans) Clay

Fig. 10.30 Clay minerals and quartz

Page 17: Sedimentary  Rocks

Breccia (#24) is made of varying

sizes of angular fragments cemented together.

Many form as the result of fault movement; others form as the result of rapid and short transportation, such as landslides.

Page 18: Sedimentary  Rocks

Conglomerate (#17) are very similar to

breccias, but the fragments are rounded.

These rocks form in alluvial fans, stream beds and pebble beaches.

Page 19: Sedimentary  Rocks

Sandstone (#16) is made up of fine-grained

particles (1/16 –2 mm). The sand grains (often

quartz) are commonly cemented by silica, carbonates, clay or iron oxides.

is identified by its sandy texture – which often translates into a gritty feel

Environments in which sandstones form include beaches, sand bars, deltas and dunes.

Page 20: Sedimentary  Rocks

Shale (#14) It is the most common

type of sedimentary rock. It is made of silt and clay

sized particles. It is generally very thin-

bedded and splits along the bedding planes.

Normally gray to black, shale may be brown to dark red, depending on the amount of included iron oxide.

form in quiet environments, such as lakes, swamps, deltas and offshore marine.

Black shale, deposited in a offshore basin in a Middle Cambrian sea. Wheeler Shale with trilobite fossil (Elrathia kingii)

Fish scales

Page 21: Sedimentary  Rocks

C L U E S T O S E D IM E N TA R Y R O C K S

F R A G M E N T A L : C o m p os e d o f p ie c e s o f ro c ks a n d m in e ra ls

L A R G E P IE C E S (B o u ld e rs ,c o b b le s ,

p eb b les )

B R E C C IA : C o m p o s e d o f la rg e a n g u la r p ie c e s a n d c la y C O N G L O M E R AT E : C o m p o s e d o f la rg e rou n d e d p ie c es an d c la y

S M A L L P IE C E S (s a nd )

S A N D S T O N E : L o o ks s a n d y (m a y “s h e d ” s a n d g ra in s ), fe e ls ro u g h ( l ike s a n d p a p e r) ; m a y b e ta n , w h ite , re d , g ra y.

V E R Y S M A L L P IE C E S (c la y, s i l t, m u d )

S H A L E : H a s ve r y th in la ye rs ; o fte n b la c k. M a y h a ve fo s s ils — u s u a ll y im p res s io n s (n o s h e ll, b u t ind e n ta tio n w ith p a tte rn o f s h e ll) o r c a rb o n ize d fi lm (as fo r p lan ts ) . H a s a d u ll lu s te r . Is s o ft. W h e n ta p pe d w ith a ro d o r o n a ta b le , i t g e ne ra ll y m a ke s a d u ll th u n k.

Page 22: Sedimentary  Rocks

Chemical Sediments

Page 23: Sedimentary  Rocks

Weathering & Sediments

Quartz

Na Feldspar

Biotite

Sediments

Weathering

Page 24: Sedimentary  Rocks

Weathering of Granite

1. Mechanical Weathering forms rock and mineral

fragments of parent rockQuartz

Na Feldspar

Sediments of:Quartz1

Feldspar1

Biotite

Ions4

4. Dissolves some ions (e.g, Ca, Na, K, Mg)

Chemical Weathering2. Converts silicates* to clay3. Oxidizes iron in minerals

(i.e., ferromagnesian minerals)

Clay2

Hematite3

*except quartz

Page 25: Sedimentary  Rocks

Weathering and Erosion of Hawaii What are the

products of the weathering of Hawaii?

Haleakala Past and Present1.3mya

Hint: Think of the black sands of Hawaii

Page 26: Sedimentary  Rocks

Sediments from Weathering

• Black sands of basalt and dark minerals • Pyroxene and • Ca-feldspar

• Chemically weathered to• Dissolved ions• Iron oxides, and • Clay (Washed away and

deposited in deep sea)

Maui, Hawaii, 1.3 my old

Page 27: Sedimentary  Rocks

Chemical Weathering and Erosion

Chemical WeatheringDissolving ionsOxidation iron oxidesClay minerals

Erosion carries sediments to ocean

Kauai: An ancient volcanic island, 4.7 my old

Ocean Water

Deep Ocean Sediments

Page 28: Sedimentary  Rocks

Chemical and Biochemical Sedimentary Rocks

Sandstone (sand) Shale (clay) Limestone (Shell frag. & lime mud)

Back Reef ReefFore Reef

Page 29: Sedimentary  Rocks

Limestone (CaCO3) (#18) • Generally it is dense, fine-

grained, and usually white to dark gray.

• Its most distinguishing feature is its solubility in weak hydrochloric or acetic acid accompanied by brisk effervescence.

• The environment of deposition if generally warm, shallow seas.

Limestone can be made two ways: Bioclastic: Fragments of

Coral, Algea and Shells Inorganic: precipitated

directly from water It comes in many

different formats

Page 30: Sedimentary  Rocks

Limestone – Travertine (#22)

Looks sugary with bands of different colours

Created when hot, carbon dioxide rich water dissolve limestone and then cools off to deposit the dissolved calcium carbonate.

Page 31: Sedimentary  Rocks

Limestone - Fossiliferous Made primarily of

seashells and other aquatic organisms.

Page 32: Sedimentary  Rocks

Limestone - Chalk White, soft, and

powdery You could break it

part with you hands.

Page 33: Sedimentary  Rocks

Limestone – Coquina (#19)

Contains nothing but seashells.

Made from old coral refs and shallow seas.

Page 34: Sedimentary  Rocks

CHERT (#13) It is made from quartz or

silica crystals It is made by replacing the

calcium carbonate in limestone with silica.

It is often the result of the dissolution of volcanic ash and is sometimes found in extensive beds.

It has waxy luster, is translucent, looks glassy and can be any color, but extensive beds are generally white to gray.

It is also used to make blades.

Page 35: Sedimentary  Rocks

GYPSUM (#21) It is made of calcium

sulfate It is found in geographically

wide-spread deposits resulting from the evaporation of a body of water, such as ocean basin or playa lake.

It is soft. Gypsum is mined for use in

wallboard and plasters, as an agricultural amendment and to control the set/cure time of Portland cement.

AlabasterSatin Spar

Selenite

Gypsum & Anhydrite (water-less calcium sulfate), Carlsbad, NM

Page 36: Sedimentary  Rocks

ROCK SALT Is known sodium

chloride It is a deposit resulting

from evaporation of a marine basin or lake.

It is used as a source of chlorine and sodium, as a food supplement, in water softeners and as a road de-icer.

Halite Trona, CA

Page 37: Sedimentary  Rocks

COAL (#20) Coal is considered a rock,

although it is not composed of minerals, but rather the decomposed remains of large volumes of vegetation that accumulated in a wet, low oxygen environment, such as a swamp or marsh.

Peat, Lignite and Sub-Bituminous & Bituminous are sedimentary varieties of coal and are used as fuels.

Coal (sub-bituminous) out of the Cretaceous Dakota Formation of north-eastern Arizona.

Page 38: Sedimentary  Rocks

DIATOMITE is composed of the

siliceous shells of microscopic alga called diatoms.

It is light weight and is generally white.

It is used as an abrasive, insecticide, filtering medium, and paint “flattener”.San Manuel, AZ

Page 39: Sedimentary  Rocks

Dolomite (#23) Composed of

calcium magnesium carbonate

The rock has over 90% carbonate and fossils are rare in these rocks

Does not react with acid.

Page 40: Sedimentary  Rocks

M O R E C L U E S T O S E D IM E N TA R Y R O C K S

C H E M IC A L : R o c k s a re c rys ta l l in e

L IM E S T O N E S : C o m p o s e d o f c a lc ite a n d a l l W IL L F IZ Z vig o ro u s ly in a c id C rys ta l l in e — L o o k s s u g a r y, u s u a l ly g ra y o r ta n F o s s il i fe ro u s — C o n ta in s s e a s h e lls (u s u a lly) o r o th e r a q u a tic o rg a n is m s T ra ve r t in e — L o o ks s u g a r y w ith b a n d s o f v a r io u s c o lo rs C h a lk — W h ite a n d s o ft (c o m e s o ff o n h a n d s ) C o q u in a — C o n ta in s a lm o s t n o th in g b u t s e a s h e l ls o r s e a s h e l l f ra gm e n ts

C H E R T: C ry p to c ry s ta llin e Q U A R T Z V e r y f in e — c a n N O T s e e c rys ta ls W a xy lu s te r C o n c h o id a l f ra c tu re (b re a k s l ike g la s s ) V e r y h a rd — w i l l e a s ily s c ra tc h g la s s M a y b e A N Y C O L O R (R e d = J a s p e r , B la c k = F l in t, in c lu d e s S i l ic i f ie d W o o d )

G Y P S U M : W h i te , g ra y, c le a r V e r y s o ft — yo u c a n s c ra tc h w i th fin g e rn a il C le a r s h e e ts , f ib ro u s o r s u g a ry

R O C K S A LT: W h i te to c le a r — c u b ic s h a p e S o ft — yo u c a n s c ra tc h i t w i th f in g e rn a i l T a s te s l ike ta b le s a l t ( IT IS T A B L E S A L T !)

C O A L : B la c k ; B r i tt le ; L ig h tw e ig h t M a y c o n ta in p la n t fo s s i ls V a r ie tie s : p e a t, l ig n i te ( in c l . je t) , s u b -b i tu m in o u s , b itu m in o u s

D IAT O M IT E : W hite V e r y s o ft ( c o m e s o ff o n y o u r h a n d s ) L ig h tw e ig h t W i ll N O T fiz z in H C l a c id (u n l ike c h a lk )

Page 41: Sedimentary  Rocks

Sedimentary Structures

Bedding: Sediments are deposited in Horizontal layers (original horizontality)Deeper rocks are older (superposition)

Page 42: Sedimentary  Rocks

Tilted Sedimentary Rock Layers

La Castilla, Peru

Page 43: Sedimentary  Rocks

Sedimentary Structures

Other information preserved in sedimentary rocks

Cross Bedding (Dunes)Graded Bedding

(Turbidity Currents)Ripple marks (water or

wind)Mud Cracks (dried lake)Fossils (many

sediments)

Page 44: Sedimentary  Rocks

Cross Bedding

Indicates currentand directionWindWater

Page 45: Sedimentary  Rocks
Page 46: Sedimentary  Rocks
Page 47: Sedimentary  Rocks

Homework P. 132 #1,2,3 P. 127 #1- 4