Lecture 7

Sediments and Sedimentary Rocks

Lecture Outline

I DefinitionsA) SedimentB) Transportation

i. Fluid Dynamicsii. Modes of Transportiii. Transport-Related Properties

C) DepositionD) Lithification

II Sedimentary RocksA) Clastic Rocks

i. Breccia and Conglomerateii. Sandstoneiii. Fine-Grained Clastic Rocks

B) Chemical Sedimentary Rocksi. Carbonatesii. Evaporites

C) Organic Sedimentary RocksIII Sedimentary StructuresIV Interpretation of Sedimentary Rocks

A) Source AreaB) Depositional EnvironmentC) Plate Tectonics and Sedimentary Rocks

Physical Geology

Definitions

sediment - solid fragmental material transported and deposited by wind, water, or ice, chemically precipitated from solution, or secreted by organisms, that forms in layers in loose, unconsolidated form.

unconsolidated material - A sediment that is loosely arranged or unstratified, or whose particles are not cemented together, occurring either at the surface or at depth.

sedimentary rock - A layered rock resulting from the consolidation of sediment.

Physical Geology

Grain SizeUdden-Wentworth Scale

Physical Geology

Sediment Transport

Water

Wind

Gravity

Ice

Physical Geology

Sediment TransportFluid Dynamics

Physical Geology

Sediment TransportModes of Transport

Dissolved Load

Suspended Load

Bed Load

•Saltation

•Rolling (Surface Creep)

Physical Geology

Sediment TransportTransport-Related Properties

Physical Geology

Deposition of Sediment

deposition - the laying-down of rock-forming material by any natural agent

deposit - Earth material of any type that has accumulated through the activities of water, wind, ice, or other agents, such as precipitation.

depositional environment - the location in which deposition occurs

Physical Geology

Deposition of SedimentProgressive Sorting

Physical Geology

Lithification of Sediment

lithification - the conversion of newly deposited sediment into a solid rock. It maybe concurrent with, soon after, or long after deposition.

Cementation

Compaction

Crystallization

Physical Geology

Lithification of SedimentCompaction

compaction - reduction in bulk volume or thickness offine-grained sediments, owing to increasing weight of overlying material that is continuously beingdeposited, or to pressures resulting from earth movements. Tighter packing of sedimentary particles results in a decrease in porosity.

Physical Geology

Lithification of SedimentCementation

cementation - the process by which clastic sediments are converted into rock by precipitation of a mineral cement among the grains of the sediment.

cement - chemically precipitated mineral material that occurs in the spaces among the grains of a sedimentaryrock, thus binding the grains into a rigid mass. The most common cements are silica, carbonates, and iron oxides.

Physical Geology

Lithification of SedimentCrystallization

crystallization - the development and growth of crystals by precipitation from solution at or near the Earth's surface.

Physical Geology

Sedimentary Rocks

Clastic

Chemical

Organic

Physical Geology

Sedimentary RocksClastic Rocks

Physical Geology

Sedimentary RocksClastic Sedimentary Rocks - Examples

conglomerate

breccia

sandstone

graywacke

siltstone

shale

Physical Geology

Sedimentary RocksChemical Sedimentary Rocks

Carbonates Evaporites

Physical Geology

Sedimentary RocksChemical Sedimentary Rocks - Carbonates

(Bioclastic Limestones)

chalk coralline limestone

coquina

Physical Geology

Sedimentary RocksChemical Sedimentary Rocks - Carbonates

(Inorganic Limestones)

tufaoolitic

limestone

travertine

Physical Geology

Sedimentary RocksChemical Sedimentary Rocks - Evaporites

rock saltNaCl

anhydriteCaSO4

rock gypsumCaSO4

. H2O

Physical Geology

Sedimentary RocksOrganic Sedimentary Rocks

coalcoal

lignite

peat

Physical Geology

Sedimentary StructuresDefinitions

sedimentary structure - a feature in sedimentary rock, formed eithercontemporaneously with deposition (primary structure) or by later sedimentary processes (secondary structure)

bedding - the arrangement of sedimentary rock in layers

bedding plane - division plane that separates each successive sedimentary layer or bed from the one above or below. It commonly marks a visible change in lithology or color.

formation - a body of rock strata that consists dominantly of a certain lithologic type or combinations of types. It is the fundamental lithostratigraphic unit. Formations may be combined into groups and subdivided into members.

Physical Geology

Sedimentary Structures

Stratification

Internal Structures

Bedding Plane Structures

Geopetal Structures

Physical Geology

Sedimentary StructuresStratification

stratification - the arrangement

of sedimentary rocks in strata;

bedding. It may be indicated

by differences in texture,

cementation, color, or

composition.

Physical Geology

Sedimentary StructuresStratification - Principle of Superposition

Physical Geology

Sedimentary StructuresStratification - Principle of Original Horizontality

Physical Geology

Sedimentary StructuresInternal Structure

graded bedding

cross-stratification

Physical Geology

Sedimentary StructuresCross-Bedding

Physical Geology

Sedimentary StructuresGraded Beds

Physical Geology

Sedimentary StructuresBedding Plane Features

Mudcracks

Ripples

Fossils

Physical Geology

Lecture 7III.F

Bedding Plane Sedimentary StructuresRipples

Physical Geology

Bedding Plane Sedimentary StructuresMudcracks

mudcrack - an irregular fracture in a crudely polygonal pattern, formed by the shrinkage of clay, silt, or mud, generally in the course of drying under surface conditions.

Physical Geology

Bedding Plane Sedimentary StructuresFossils

Physical Geology

Sedimentary StructuresGeopetal Structures

geopetal - pertaining to any rock feature that indicates the relation of top to bottom at the time of formation of the rock

symmetric ripple marks

included fragments

cross-bedding

graded bedding

mud cracks

bed surface marks

scour marks

fossils

Physical Geology

Interpretation of Sedimentary RocksGrain Size

Lecture 7IV

Physical Geology

Interpretation of Sedimentary RocksColor

Physical Geology

Depositional Environment

Continental

Transitional

Marine

Physical Geology

Plate Tectonics and Sedimentary RocksPassive Margin

Physical Geology

Plate Tectonics and Sedimentary RocksVolcanic Island Arcs

Physical Geology

Plate Tectonics and Sedimentary RocksContinental Collision

Physical GeologyPhysical Geology