Marine Sediments Review

EOS 110 - 201309

MARINE SEDIMENTS

Outline

• Types of sediments

• Classified by particle size

• Classified by origin

• Classified by location

• Controls on sediment accumulation

Readings: Chapter 5: Sediments pp. 130-151

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Introduction

Sediments are particles of organic or inorganic matter that accumulate in loose, unconsolidated forms.

Sediments reveal Earth’s history:
- Past climates
- Plate motions
- Age of seafloor
- Fossil evolution and extinction

- Timing of major extinctions

- Location of natural resources (e.g. crude oil, natural gas)

1) Types of sediments

I) Classified by particle size

(see table 5.1)

ii) Classified by origin

(see table 5.2)

• Terrigenous

• Biogenous

• Hydrogenous

• Cosmogenous

a) Terrigenous sediments

-Derived from preexisting rock material, rock fragments from land

-Also called Lithogeneous or lithogenic

-originated by weathering and erosion

- Sediments are transported to the oceans by: Wind, Water (rivers, streams), Glaciers, Gravity flow (landslides), Volcanic eruptions

- ex. Clay, quartz and estuarine mud

-Big rivers: The amazon, The mississippi

- Composition of terrigenous sediments:

Host deposits are primarily composed of the most abundant mineral on earth= Quartz ( SiO2) and clays

b) Biogenous sediments

• Derived from remains of hard-parts of marine organisms

• Macroscopic:

Shells

Bones and Teeth of larger organisms

Rare sediment, except in certain tropical beaches (coral sand)

• Microscopic:

Small ( microscope-size) particles

Tests ( or shells) of micro organisms.

Deposits are called ooze ( fine-grain mushy material)

Ooze contains . 30% biogeneous material by weight

--->crest is fine-grain terrigeneous clays for example

Most abundant biogeneous sediment type

Composition of biogenous sediments:

• Most common compounds:

• Silica (SiO2.nH2O: opal)

• Calcium carbonate (CaCO3: calcite)

Siliceous sediments:

• Mostly composed of:

Microscopic protozoans :

----> radiolarians

Microsocpic algaes

--> diatoms

When siliceous ooze lithifies

= diatomaceous earth

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-Other minor components=sponges

Calcareous sediments:

• Mostly composed of:

Microscopic protozoans= foraminiferans