Geology Chapter 6

Particle size (from biggest, coarsest to finest)

Boulder, cobble, pebble, sand, silt, clay

Composition of sediment is governed by?

Rates of Chemical, mechanical weathering, and erosion.

Sediment

loose unconsolidated particles of mineral that orginate from weathering/erosion and precipitation

Most silt are?

Quartz

What are the 3 types of Sedimentary rocks?

Detrital, Chemical, Organic

What happens during transportation of sediment?

Rounding and Sorting

Rounding

grinding away sharp edges and corners during transporation

Sorting

sediment grains selected and separated according to grain size.

Lithification

process that convert loose sediments into sediment rocks

Detrital sedimentary rocks form mostly by?

Compaction and cementation of grains

What are the 3 different types of Lithification?

compaction, cementation, cyrstallization

compaction

packs loose sediment together (open pore space filled)

Cementation

precipitation of cement around grains binds them into rock

crystallization

Crystal hold them together

Detrital sedimentary rocks

formed form cemented sediment grain. weathered and eroded remains

What is the most common sedimentary rock type?

Detrital

Types of detrital rocks

Breccia, Conglomerate, sandstone

Sedimentary Breccia

coarse-grained sedimentary rock formed by cementation of coarse angular fragments of rubble

Conglomerate

coarse-grained formed by cementation of rounded gravel that transported only a short distance

Sandstone

cementation of sand grains.

Matrix

finer materials that larger particles are embedded in.

What mineral tend to concentrate in sandstone? Why?

Quartz because it is more resistant to chemical weathering than feldspar

How did Sandstone form?

Formed from sand deposited by rivers, wind, waves, or turbidity currents

How did Shale form?

Formed from river, lake, or ocean mud

Chemical sedimentary rocks are formed by?

precipitated from low-temp by organisms or inorganic.

What are the types of chemical sedimentary rocks?

carbonate Rocks, Chert, and Evaporites

What are the two main types of carbonate rocks?

Limestone and Dolomite

Limestone

composed of calcite formed either as a chemical precipitate in a reef, or by cementation of shell and coral fragments or of ooids

Dolomite

usually forms from the alteration of limestone by magnesium-rich solutions

Chert

consists of mainly silica and usually forms from accumulation of microscopic organisms

Evaporites

forms as water evaporates (rock salt, gypsum)

Original beds are deposited in —layers

horizontal

Sedimentary structures

features found within sedimentary rocks

Cross beds

in sandstone, thinner inclined beds formed by flowing air and water

Ripple marks

formed by waves

Mud cracks

form in drying mud

Formation

body of rock of considerable thickness large enough to be mapped and with characteristics that distinguish it from adjacent rocks

transgression

sea level rises. Limestone, Shale, Sandstone

Regression

sea. level drops. Sandstone, Shale, Limestone