slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
British Virgin Islands Daria Jones PowerPoint Presentation
Download Presentation
British Virgin Islands Daria Jones

Loading in 2 Seconds...

play fullscreen
1 / 28

British Virgin Islands Daria Jones - PowerPoint PPT Presentation


  • 133 Views
  • Uploaded on

British Virgin Islands Daria Jones. Virgin Gorda, BVI James O’Brien. SEDIMENTATION AND SEDIMENTARY ROCKS. DEPOSITIONAL or SEDIMENTARY ENVIRONMENTS. Analysis of sedimentary rock can provide clues to their DEPOSITIONAL ENVIRONMENT . Can then be used to interpret geologic history of a

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'British Virgin Islands Daria Jones' - Jims


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide3

Virgin Gorda, BVI

James O’Brien

slide4

SEDIMENTATION AND SEDIMENTARY ROCKS

DEPOSITIONAL or SEDIMENTARY ENVIRONMENTS

Analysis of sedimentary rock can provide clues to their

DEPOSITIONAL ENVIRONMENT.

Can then be used to interpret geologic history of a

region.

Can include

Continental environments

Transitional environments

Marine environments

slide5

SEDIMENTATION AND SEDIMENTARY ROCKS

DEPOSITIONAL or SEDIMENTARY ENVIRONMENTS

Continental Environments

Found on landmasses.

Most sediments are clastic.

Include paleocurrent

direction or indicators.

Plant and freshwater fossils

common.

Includes rivers, lakes, caves,

deserts and glaciers.

slide6

SEDIMENTATION AND SEDIMENTARY ROCKS

DEPOSITIONAL or SEDIMENTARY ENVIRONMENTS

Transitional Environments

Occur at boundary between

ocean and land.

Some sediments are clastic,

some are organic.

Influenced by tides, currents,

and breaking waves.

Includes estuaries, deltas,

beaches and lagoons.

slide7

SEDIMENTATION AND SEDIMENTARY ROCKS

DEPOSITIONAL or SEDIMENTARY ENVIRONMENTS

Marine Environments

Entirely oceanic environments.

Most sediments are clastic, some are organic.

Vary according to depth of water.

Shallow marine < 200 m.

Narrow band along continent.

Sandstone, mudstone, limestone

Deep marine - offshore.

Fine-grained wind blown clays

and organic, calcareous or siliceous oozes.

slide8

SEDIMENTATION AND SEDIMENTARY ROCKS

DEPOSITIONAL or SEDIMENTARY ENVIRONMENTS

Shallow Marine Environments

slide9

SEDIMENTATION AND SEDIMENTARY ROCKS

DEPOSITIONAL or SEDIMENTARY ENVIRONMENTS

Deep Marine Environments

slide10

SEDIMENTATION AND SEDIMENTARY ROCKS

DEPOSITIONAL or SEDIMENTARY ENVIRONMENTS

Deep Marine Environments

slide11

SEDIMENTATION AND SEDIMENTARY ROCKS

SEDIMENTARY FACIES

Adjacent sedimentary or depositional environments

produce different sediment and rock types.

While different, they are deposited at the same time.

Represents a horizontal continuum.

The horizontal changes demonstrate the variability of

the adjacent environments.

Vertical changes reflect how environments have

changed over time.

slide13

SEDIMENTATION AND SEDIMENTARY ROCKS

SEDIMENTARY FACIES

Walther’s Law of Succession of Facies

Sedimentary facies move as environmental conditions

change.

Position of the beach will vary as position of sea level

changes.

Adjacent facies will stack up vertically over time.

slide15

SEDIMENTATION AND SEDIMENTARY ROCKS

DIFFERENCES IN CLIMATE AND WEATHERING

Arid Regions

Sandstones and Limestones produce cliffs.

Mudrocks make up slopes.

Humid Regions

Sandstones produce cliffs

Mudrocks and limestones make up slopes

slide16

SEDIMENTATION AND SEDIMENTARY ROCKS

DIFFERENCES IN CLIMATE AND WEATHERING

Slopes in Arid Regions

slide17

SEDIMENTATION AND SEDIMENTARY ROCKS

DIFFERENCES IN CLIMATE AND WEATHERING

Slopes in Humid Regions

Kope Formation, OH

Showangunks, NY

slide18

Maine Geological Survey

July 2002, Site of the Month

slide20

METAMORPHISM AND METAMORPHIC ROCKS

All rocks are susceptible to metamorphism.

Change occurs in response to conditions affecting them.

slide21

METAMORPHISM AND METAMORPHIC ROCKS

METAMORPHIC ROCKS

Generally form at conditions

between those that form

igneous and sedimentary

rocks.

METAMORPHISM is the

process by which heat, pressure,

and chemical reactions deep in

the Earth alter the mineral

content and/or structure of pre-

existing rock without melting it.

slide22

METAMORPHISM AND METAMORPHIC ROCKS

Most are buried beneath layers of sedimentary rocks.

Processes take place deep in the Earth.

Brought to the surface by tectonics and erosion.

Most of what we know about metamorphism and

metamorphic rocks comes from lab experiments.

slide23

METAMORPHISM AND METAMORPHIC ROCKS

What Drives Metamorphism?

Rocks and minerals are most stable at the conditions

under which they form.

Movement of rocks causes instabilities to exist.

New minerals and rocks are formed in an

attempt to become stable.

Increase the amount of change, metamorphism occurs.

Produce clays by weathering

With metamorphism, clay are altered to become

micas with increasing heat and pressure.

slide24

METAMORPHISM AND METAMORPHIC ROCKS

Rocks remain solid during metamorphism.

Minerals become unstable during metamorphism.

Bonds break in minerals allowing the creation

of new minerals, stable at new conditions.

Not all the bonds break, that would be melting.

Circulation of ion-rich fluids enhances the movement

within a rock undergoing metamorphism.

The power of water strikes again.

Composition of the parent rock also influences the

metamorphic rock that forms.

slide25

METAMORPHISM AND METAMORPHIC ROCKS

METAMORPHISM is the transformation of solid

rock to form new minerals and textures.

Quartz will remain quartz, but size and shape may

change.

Clays break down and elements and ions recombine

to form new minerals.

With enough heat, atoms and ions can move within a

rock to form new minerals.

Composition of the rock may stay the same, but the

minerals and texture may change.

slide26

METAMORPHISM AND METAMORPHIC ROCKS

FACTORS INFLUENCING METAMORPHISM

HEAT

Most important factor in driving metamorphism.

Accelerates the pace of most chemical reactions.

Heat increases with depth in the Earth

Thermal Gradient

20-30C/kilometer depth

74 F/mile depth

Rocks at depth are always at higher temperature.

Rocks and minerals that form there are stable.

slide27

METAMORPHISM AND METAMORPHIC ROCKS

FACTORS INFLUENCING METAMORPHISM

HEAT

Moving rocks from the surface to depth causes increase

in heat and metamorphic potential.

Sources for Increase in Heat

Tectonic activity pushes rock from surface to depth.

Sediments get buried.

Contact with magma.

slide28

METAMORPHISM AND METAMORPHIC ROCKS

FACTORS INFLUENCING METAMORPHISM

HEAT

Heat in the crust is produced by:

Decay of radioactive isotopes

Upward conduction of heat from the mantle

Friction from subduction

Heat necessary for metamorphism is not attained

until a depth of 10 kilometers (6 miles).

To occur at the surface it requires contact with

rising magma.