Sediments Rocks Lecture.pdf
This document was uploaded by user and they confirmed that they have the permission to share it. If you are author or own the copyright of this book, please report to us by using this DMCA report form. Report DMCA
Overview
Download & View Sediments Rocks Lecture.pdf as PDF for free.
More details
- Words: 967
- Pages: 73
Chapter 6
Sediments and Sedimentary Rocks Hurricane Ivan: 09-16-04, 15:15 UTC
Image source: NOAA-GEOS-12 (1 km)
rock cycle!
sediment: (sedimentum: settling )! • fragments of solid material that settle and accumulate! • fragments settle in layers after being transported!
fragments are products of weathering and erosion! easy to see sedimentation in action!
sedimentary rock: “lithified” sediment; “lithos” -- rock! • 75% of all rock exposed on Earth’s land surface! • composition is weathering products of rocks or biological matter! • principal source of coal, oil, natural gas, cement, Al, Fe, groundwater!
3 types of sediments and sedimentary rocks:! detrital sediment: fragments of pre-existing rocks!
chemical sediment: precipitated from dissolved ions in water!
organic matter: formed from accumulation of biological debris (swamps)!
relationship to Earth’s systems! • atmosphere ! -- most sediments produced by weathering in air! -- sand and dust transported by wind!
• hydrosphere ! -- water is primary agent in sediment production, ! transportation, deposition, cementation, and ! formation of sedimentary rocks!
• biosphere ! -- biological activity key to formation! -- petroleum and coal resources have biological origin!
sediment: loose, solid particles! originate from:! -- weathering and erosion of pre-existing rocks! -- chemical precipitation from solution, including ! "secretion by organisms in water!
sediment is classified by particle size! • boulder > 256 mm! • cobble: 64 to 256 mm! • pebble: 2 to 64 mm! • sand: 1/16 to 2 mm! • silt: 1/256 to 1/16 mm! • clay: < 1/256 mm!
turning sediment into sedimentary rock! transportation!
movement of sediment away from its source,! typically by water, wind or ice! rounding occurs by abrasion during transport! “particles knocking against each other”!
sorting occurs as sediment is separated by size! by transporting agents, such as water! --sediment size decreases with increased transport distance--!
sediments may be angular or rounded!
rounded beach boulders! angular fragments!
particle size sorting by rivers ! as flow slows down, river can no longer carry larger particles!
current velocity decreases!
headwaters!
mouth! grade = change in elevation/length!
Mountains
River Gravel
Plain
Mountains
River Gravel
Plain
Sand
Mountains
River Gravel
Plain
Sand
Silt and clay
gravel/boulders at headwaters!
normally! deposited! in or near! steep! mountains! at river! headwaters
sand/silt downstream, closer to mouth of river!
Distance from Source
sediments may be poorly sorted or well sorted! wind: most selective transporting agent! "-- only picks up sand thus deposits are well sorted!
windblown sand forms dunes!
note well sorted and rounded grains!
glaciers and flooding rivers are unselective transporting agents! flooding rivers -- fast currents! …transport all sizes…!
poorly sorted river sediment!
poorly sorted glacial sediment!
turning sediment into sedimentary rock! deposition! • settling of transported material! • accumulation of chemical or organic sediments,! "particularly in water! sediment transported! from canyon and! deposited at ! canyon mouth! at the! base of the slope!
environment of deposition is setting of deposition!
sediments and sedimentary rocks form in many settings!
turning sediment into sedimentary rock! preservation! • sediments must be preserved to turn into rock! • burial by additional sediments deposited on top!
turning sediment into sedimentary rock! lithification! • sediments must be hardened into rock! • compaction and cementation occur!
water is expelled from pore space!
other fluids cement grains!
Basic Clastic Rock Types • Breccias: angular particles! • Conglomerates: rounded particles! • Sandstones! – Quartz sandstone: dominated by quartz grains! – Arkose sandstone: composed of qtz & fsp grains! – Graywacke: dominated by lithic (rock) fragments! • Shales: mud and silt particles!
Coarse Breccia NB Angular fragments
Conglomerate
NB Rounded particles & dissimilar lithologies
Quartz Sandstone - > 90% qtz
Arkose Sandstone - Feldspar + Qtz
Graywacke - lithic fragments in dark fine grained matrix
Poorly sorted, “dirty” sandstone Sorting can be based on particle size and/or composition; It yields important constraints on provenance of the clastic particles.
Shale outcrop, Pittsburgh, PA
Shale hand specimens
NB very fine grained and thin laminations
Lithification and compaction of shale
NB volume loss during compaction
Chemical Sedimentary Rocks • Carbonate Rocks (e.g. CaCO3) • Chert (e.g. SiO2) • Evaporites (e.g. NaCl; CaSO4•2H2O)
Carbonate atoll, Bora Bora!
Patch Reefs
Global Reef Distribution
Carbonate Beach - Lagoon Environments
Bioclastic Limestones
Clearly visible fossils
Fine grained carbonate mud
Coralline algae - Lagoon Environment
Fossil Rich Limestone - Coquina
Marl - Chalk (pelagic ooze)
SEM images of forams and coccoliths (CaCO3)
Photo credits: V. Pariente, J. Lundquist, D. Greig
Carbonate Bank - Shallow Currents
Oolitic Limestone
Nodular Chert (poorly crystalline SiO2)
Redwall limestone, Grand Canyon, AZ
Bedded Chert
SEM images of diatom fustules (SiO2) - unicellular plants
100 m
100 m From: http://www.uni-mainz.de/FB/Geøpalaeontologie/griessdiato.html
Evaporites
Bonneville salt flats, UT
Organic Sedimentary Rocks • Coal!
Sedimentary Structures! Environments of Deposition
Coal Bed - Trinidad, CO Composed of decayed plant remains - compressed peat bogs
Sedimentary Structures • Bedding - series of visible layers in sedimentary rocks! – Principle of Original Horizontality! – Superposition! – Cross-cutting relationships!
• • • •
Grading! Mud Cracks! Ripple Marks! Fossils
Horizontal Bedding
Cross Bedding
Cross Bedding Models
Normal Grading
Grading Model
Turbidity Currents
Mud Cracks
Preserved mud cracks
Ripple Marks Model
Symmetric
Asymmetric
Tidal Flat Ripples
Current Direction
Preserved Ripple Marks
Preserved Bivalve Fossils
Vertebrate (Fish) Fossil
Dinosaur Footprint
Interpretation of Sedimentary Rocks! • Source Area! • Environment of Deposition! • Plate Tectonics and Sedimentary Rocks
Sedimentary Formation Definitions • Body of rock of considerable thickness! • Characteristics must be distinguishable from adjacent units! • Usually composed of one or more beds! • Often based on rock type (lithology or lithofacies)! • Contacts are the boundary surfaces between two rock units of different lithology or age
Upper Grand Canyon Sequence
Lithofacies - Paleocurrent Maps
Fluvial Environments
Alluvial Fan Deposits - Baja, CA Coarse channel deposit (conglomerate)
Convergent Margin Environment
Rift Sedimentary Environment
NB that this model only is applicable for sub-aerial environments
Sediments and Sedimentary Rocks Hurricane Ivan: 09-16-04, 15:15 UTC
Image source: NOAA-GEOS-12 (1 km)
rock cycle!
sediment: (sedimentum: settling )! • fragments of solid material that settle and accumulate! • fragments settle in layers after being transported!
fragments are products of weathering and erosion! easy to see sedimentation in action!
sedimentary rock: “lithified” sediment; “lithos” -- rock! • 75% of all rock exposed on Earth’s land surface! • composition is weathering products of rocks or biological matter! • principal source of coal, oil, natural gas, cement, Al, Fe, groundwater!
3 types of sediments and sedimentary rocks:! detrital sediment: fragments of pre-existing rocks!
chemical sediment: precipitated from dissolved ions in water!
organic matter: formed from accumulation of biological debris (swamps)!
relationship to Earth’s systems! • atmosphere ! -- most sediments produced by weathering in air! -- sand and dust transported by wind!
• hydrosphere ! -- water is primary agent in sediment production, ! transportation, deposition, cementation, and ! formation of sedimentary rocks!
• biosphere ! -- biological activity key to formation! -- petroleum and coal resources have biological origin!
sediment: loose, solid particles! originate from:! -- weathering and erosion of pre-existing rocks! -- chemical precipitation from solution, including ! "secretion by organisms in water!
sediment is classified by particle size! • boulder > 256 mm! • cobble: 64 to 256 mm! • pebble: 2 to 64 mm! • sand: 1/16 to 2 mm! • silt: 1/256 to 1/16 mm! • clay: < 1/256 mm!
turning sediment into sedimentary rock! transportation!
movement of sediment away from its source,! typically by water, wind or ice! rounding occurs by abrasion during transport! “particles knocking against each other”!
sorting occurs as sediment is separated by size! by transporting agents, such as water! --sediment size decreases with increased transport distance--!
sediments may be angular or rounded!
rounded beach boulders! angular fragments!
particle size sorting by rivers ! as flow slows down, river can no longer carry larger particles!
current velocity decreases!
headwaters!
mouth! grade = change in elevation/length!
Mountains
River Gravel
Plain
Mountains
River Gravel
Plain
Sand
Mountains
River Gravel
Plain
Sand
Silt and clay
gravel/boulders at headwaters!
normally! deposited! in or near! steep! mountains! at river! headwaters
sand/silt downstream, closer to mouth of river!
Distance from Source
sediments may be poorly sorted or well sorted! wind: most selective transporting agent! "-- only picks up sand thus deposits are well sorted!
windblown sand forms dunes!
note well sorted and rounded grains!
glaciers and flooding rivers are unselective transporting agents! flooding rivers -- fast currents! …transport all sizes…!
poorly sorted river sediment!
poorly sorted glacial sediment!
turning sediment into sedimentary rock! deposition! • settling of transported material! • accumulation of chemical or organic sediments,! "particularly in water! sediment transported! from canyon and! deposited at ! canyon mouth! at the! base of the slope!
environment of deposition is setting of deposition!
sediments and sedimentary rocks form in many settings!
turning sediment into sedimentary rock! preservation! • sediments must be preserved to turn into rock! • burial by additional sediments deposited on top!
turning sediment into sedimentary rock! lithification! • sediments must be hardened into rock! • compaction and cementation occur!
water is expelled from pore space!
other fluids cement grains!
Basic Clastic Rock Types • Breccias: angular particles! • Conglomerates: rounded particles! • Sandstones! – Quartz sandstone: dominated by quartz grains! – Arkose sandstone: composed of qtz & fsp grains! – Graywacke: dominated by lithic (rock) fragments! • Shales: mud and silt particles!
Coarse Breccia NB Angular fragments
Conglomerate
NB Rounded particles & dissimilar lithologies
Quartz Sandstone - > 90% qtz
Arkose Sandstone - Feldspar + Qtz
Graywacke - lithic fragments in dark fine grained matrix
Poorly sorted, “dirty” sandstone Sorting can be based on particle size and/or composition; It yields important constraints on provenance of the clastic particles.
Shale outcrop, Pittsburgh, PA
Shale hand specimens
NB very fine grained and thin laminations
Lithification and compaction of shale
NB volume loss during compaction
Chemical Sedimentary Rocks • Carbonate Rocks (e.g. CaCO3) • Chert (e.g. SiO2) • Evaporites (e.g. NaCl; CaSO4•2H2O)
Carbonate atoll, Bora Bora!
Patch Reefs
Global Reef Distribution
Carbonate Beach - Lagoon Environments
Bioclastic Limestones
Clearly visible fossils
Fine grained carbonate mud
Coralline algae - Lagoon Environment
Fossil Rich Limestone - Coquina
Marl - Chalk (pelagic ooze)
SEM images of forams and coccoliths (CaCO3)
Photo credits: V. Pariente, J. Lundquist, D. Greig
Carbonate Bank - Shallow Currents
Oolitic Limestone
Nodular Chert (poorly crystalline SiO2)
Redwall limestone, Grand Canyon, AZ
Bedded Chert
SEM images of diatom fustules (SiO2) - unicellular plants
100 m
100 m From: http://www.uni-mainz.de/FB/Geøpalaeontologie/griessdiato.html
Evaporites
Bonneville salt flats, UT
Organic Sedimentary Rocks • Coal!
Sedimentary Structures! Environments of Deposition
Coal Bed - Trinidad, CO Composed of decayed plant remains - compressed peat bogs
Sedimentary Structures • Bedding - series of visible layers in sedimentary rocks! – Principle of Original Horizontality! – Superposition! – Cross-cutting relationships!
• • • •
Grading! Mud Cracks! Ripple Marks! Fossils
Horizontal Bedding
Cross Bedding
Cross Bedding Models
Normal Grading
Grading Model
Turbidity Currents
Mud Cracks
Preserved mud cracks
Ripple Marks Model
Symmetric
Asymmetric
Tidal Flat Ripples
Current Direction
Preserved Ripple Marks
Preserved Bivalve Fossils
Vertebrate (Fish) Fossil
Dinosaur Footprint
Interpretation of Sedimentary Rocks! • Source Area! • Environment of Deposition! • Plate Tectonics and Sedimentary Rocks
Sedimentary Formation Definitions • Body of rock of considerable thickness! • Characteristics must be distinguishable from adjacent units! • Usually composed of one or more beds! • Often based on rock type (lithology or lithofacies)! • Contacts are the boundary surfaces between two rock units of different lithology or age
Upper Grand Canyon Sequence
Lithofacies - Paleocurrent Maps
Fluvial Environments
Alluvial Fan Deposits - Baja, CA Coarse channel deposit (conglomerate)
Convergent Margin Environment
Rift Sedimentary Environment
NB that this model only is applicable for sub-aerial environments
Related Documents
Sediments Rocks Lecture.pdf
November 2019 15
Sediments And Sedimentary Rocks
November 2019 10
Rocks
December 2019 52
Contaminated Sediments
November 2019 16
Rocks
November 2019 45
Rocks
October 2019 103More Documents from ""
Wellsite Geologist Requirements.pdf
November 2019 5
Sediments Rocks Lecture.pdf
November 2019 15
Ndx_iqbal.pdf
November 2019 10
Wellsite+geologist+requirements.pdf
November 2019 7