Sedimentary and Metamorphic Rock Formation Processes, Slides of Earth Sciences

Download Sedimentary and Metamorphic Rock Formation Processes and more Slides Earth Sciences in PDF only on Docsity!

R O C K S F R O M S E D I M E N T S

SEDIMENTARY ROCKS

SEDIMENTARY ROCKS

How sediments are formed to sedimentary rocks Sedimentary processes have portions that are largely dependent on climatic events (e.g. precipitation and wind) powered by the sun.  As rocks are exposed to these surface conditions, their mineral constituents adapt to the change in conditions (temperature, pressure, etc.) which causes significant physical and chemical changes

A R E P R O C E S S E S L E A D I N G T O T H E B R E A K D O W N O F R O C K S

SEDIMENTARY

PROCESSES

SEDIMENTARY PROCESSES

Processes that take place before the sediments are transformed to sedimentary rocks  (^) Weathering - Transport  (^) Erosion - Deposition Process that will finally lithify or make the sediments into a sedimentary rock

• Diagenesis

SEDIMENTARY PROCESSES

Chemical weathering take mostly on exposed surfaces of rocks If rocks are broken down into smaller pieces, it will be more vulnerable to attacks of chemical weathering Chemical weathering processed result to the ‘decay’ of minerals present in the rock With greater difference in the conditions of mineral formation and surface conditions, minerals are more susceptible to weathering attacks

SEDIMENTARY PROCESSES

 (^) Erosion Means to ‘eat away’ Is the process of eating away rocks from their source. With physical and chemical weathering already weakening the stability of rocks, erosion takes place with the help of gravity and medium such as water, wind or organisms

SEDIMENTARY PROCESSES

Competence is the property of medium (e.g. water, air, etc) to bring bigger sediments Capacity is the property of medium to bring more sediments Sorting is the property that happens smaller sediments are delivered farther away while the larger ones are left behind because of the continuous transport As a summary: with greater distance of transport, sediments tend to become smaller, rounder, spherical in shape, and well-sorted.

SEDIMENTARY PROCESSES

 Deposition The settling of the sediments in an area before they are finally lithified to form sedimentary rocks It occurs when the energy of the medium/agent is no longer capable of transporting the sediments

SEDIMENTARY PROCESSES

Diagenetic processes are important in the formation of sedimentary rocks. Without them, your sediments will remain unconsolidated

T H E E N D P R O D U C T O F P H Y S I C A L W E AT H E R I N G W O U L D B E S M A L L E R U N I T S O F S E D I M E N T S , W H I L E C H E M I C A L W E AT H E R I N G W O U L D B E C H E M I C A L LY- D I S S O LV E D M I N E R A L C O M P O N E N T S A N D R E S I S TA N T M I N E R A L S. B E C A U S E O F T H I S D I S T I N C T I O N O F E N D P R O D U C T S , T H E C L A S S I F I C A T I O N O F S E D I M E N T A R Y R O C K S B E C O M E S E A S I E R

CLASSIFYING

SEDIMENTARY ROCKS

DETRITAL SEDIMENTARY ROCKS

Udden-Wentworth scale (classification is based on size not on composition)

DETRITAL SEDIMENTARY ROCKS

 Conglomerates and Breccias Are detrital sedimentary rocks composed of gravel-sized (>2mm in size) elements Conglomerates are composed of rounded (smooth) rock fragments Breccias are composed of angular ones For rounded grains, the sediments came from a source farther away from the area where the sediments are deposited For angular grains, the source of the sediments must be nearby

DETRITAL SEDIMENTARY ROCKS

 (^) Sandstones Are detrital sedimentary rocks composed of hand-sized (1/16mm – 2mm in size) sediments Because of their smaller sediment size, the roundness of grains may be difficult to determine Sand is deposited at much lower energies compared to conglomerates and breccias

DETRITAL SEDIMENTARY ROCKS

 (^) Siltstones Are detrital sedimentary rocks composed of silt-sized (1/256 – 1/16 mm in size) sediments Because of its smaller size, they may be easily mistaken for fine sandstones or claystones