沉积构造与沉积环境
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Lab4_G435.pps
3
Sedimentary Depositional Environments
4
Lab4_G435.pps
Distinctive and Common Stratigraphic Successions
• Vertical successions principally identified by lithology, associations and vertical arrangement of sedimentary structures
Sharp------> gradational-------> amalgamated
– Bedding planes:
– Non-deposition, erosion, or change in depositional regime
• Note the time significance of ―non-deposited strata‖ • Sedimentary record is sparse; More time, with NO deposition, than record.
– Traction: lateral accretion from bed load
• Cross stratification – Scale » Cross laminations; < 3cm amplitude, < 40 cm λ » Cross beds; > 10cm amplitude, > 10cm λ – Planar tabular cross Strat vs trough cross Strat
– Through-going bioturbation:
• Obliteration of primary current induced structures: indicates relatively slow rates of sediment accumulation • Plant roots—> subaerial deposition
– Indicative of particular sedimentary depositional environments
5
Lab4_G435.pps
Primary Current-Induced Sedimentary Structures
• AccretFra Baidu bibliotekonary and Erosional
16
Lab4_G435.pps
Biogenic Structures; Mode of Living
– Vertical accretion: parallel, horizontal layers
• Typically suspension settling/chemical aggradation
– Lateral accretion; Traction transport
• Beds > 1cm • Laminations < 1cm
Primary Current-Induced Sedimentary Structures
Climbing ripples
Lab4_G435.pps
Planar-tabular x-beds
trough x-beds
11
Deformational Sedimentary Structures
• Desiccation
• Mud cracks (subaerial exposure), synaeresis cracks (concentration gradients)
• Water escape
• Mechanical instability (rapid deposition, high water content)
– Vertical accretion: parallel horizontal layers – Lateral accretion
6
Lab4_G435.pps
– Accretionary/Aggradational:
• Physical, chemical, biological accumulation
8
Lab4_G435.pps
Primary Current-Induced Sedimentary Structures
• Types of bedding (mechanical aggradation)
• Horizontal stratification
– Suspension settling: vertical accretion – Graded bedding:
Mud cracks, clear indication of subaerial exposure
12
Lab4_G435.pps
Biogenic Sedimentary Structures
• Syndepositional modification of sediment by biological agents.
• Ethological approach (environmental conditions determine organisms behavior –> sedimentary record). • Abundance of life. • Types of organisms (plants, animals; Single/ multicellular etc). • Mode of living.
Primary Current-Induced Sedimentary Structures
10
Lab4_G435.pps
• Types of bedding (mechanical aggradation)
– Traction: lateral accretion from bed load
• Cross stratification – Scale » Cross laminations; < 3cm amplitude, < 40 cm λ » Cross beds; > 10cm amplitude, > 10cm λ – Planar tabular cross Strat vs trough cross Strat
7
Lab4_G435.pps
Primary Current-Induced Sedimentary Structures
• Erosional (scour):
– Bedding contacts:
• Sediment removal by currents • Change in depositional regime
13
Lab4_G435.pps
– Biogenic structures influenced by:
Biogenic Structures; Mode of Living
• Discrete burrows:
• Form and shape
– – – – Vertical escape artists: Skolithos Horizontal grazers: Zoophycus/Nereites 3D miners: Cruziana Glossifungites » ―Hard-rock‖ miners: burrows into firm substrate
– May (in conjunction with other facies characteristics) be indicative of Sedimentary Depositional Environment.
• • • • Primary Current Induced structures. Biogenic Structures. Deformational Structures. Secondary Mineralization.
– Bedding:
• lithologic, textural, structural homogeneity indicating discrete time intervals of essentially constant (or constantly changing) deposition
14
Lab4_G435.pps
Biogenic Structures; Mode of Living
• Discrete burrows:
• Form and shape
– Vertical escape artists: Skolithos – Horizontal grazers: Zoophycus/Nereites – 3D miners: Cruziana
Mud cracks, clear indication of subaerial exposure
Lab4_G435.pps
2
Sedimentary Depositional Environments
• Siliciclastic
– Short – Long
• Carbonate
– Rimmed margins – Ramps – Patforms
Lab4_G435.pps
1
Sedimentary Structures
• Features preserved in sedimentary strata that indicate.
• Physical, • Biological, and. • Chemical processes and conditions during and after deposition.
15
Lab4_G435.pps
Biogenic Structures; Mode of Living
• Discrete burrows:
• Form and shape
– – – – Vertical escape artists: Skolithos Horizontal grazers: Zoophycus/Nereites 3D miners: Cruziana Glossifungites » ―Hard-rock‖ miners: burrows into firm substrate
Primary Current-Induced Sedimentary Structures
• Bedding:
• lithologic, textural, structural homogeneity indicating discrete time intervals of essentially constant (or constantly changing) deposition
Sedimentary Structures and Preliminary to Sedimentary Environments
Understanding what sedimentary structures mean in terms of physical, biological, and chemical processes that occurred during, shortly after, and subsequent to deposition is the starting point for the analysis of sedimentary rocks and the environments in which they were deposited. Knowing something about fluid dynamics, ecology, and chemical processes is useful!
• Regular variation in particle size in an individual bed (constantly changing hydrodynamic conditions)
9
Lab4_G435.pps
• Types of bedding (mechanical aggradation)
3
Sedimentary Depositional Environments
4
Lab4_G435.pps
Distinctive and Common Stratigraphic Successions
• Vertical successions principally identified by lithology, associations and vertical arrangement of sedimentary structures
Sharp------> gradational-------> amalgamated
– Bedding planes:
– Non-deposition, erosion, or change in depositional regime
• Note the time significance of ―non-deposited strata‖ • Sedimentary record is sparse; More time, with NO deposition, than record.
– Traction: lateral accretion from bed load
• Cross stratification – Scale » Cross laminations; < 3cm amplitude, < 40 cm λ » Cross beds; > 10cm amplitude, > 10cm λ – Planar tabular cross Strat vs trough cross Strat
– Through-going bioturbation:
• Obliteration of primary current induced structures: indicates relatively slow rates of sediment accumulation • Plant roots—> subaerial deposition
– Indicative of particular sedimentary depositional environments
5
Lab4_G435.pps
Primary Current-Induced Sedimentary Structures
• AccretFra Baidu bibliotekonary and Erosional
16
Lab4_G435.pps
Biogenic Structures; Mode of Living
– Vertical accretion: parallel, horizontal layers
• Typically suspension settling/chemical aggradation
– Lateral accretion; Traction transport
• Beds > 1cm • Laminations < 1cm
Primary Current-Induced Sedimentary Structures
Climbing ripples
Lab4_G435.pps
Planar-tabular x-beds
trough x-beds
11
Deformational Sedimentary Structures
• Desiccation
• Mud cracks (subaerial exposure), synaeresis cracks (concentration gradients)
• Water escape
• Mechanical instability (rapid deposition, high water content)
– Vertical accretion: parallel horizontal layers – Lateral accretion
6
Lab4_G435.pps
– Accretionary/Aggradational:
• Physical, chemical, biological accumulation
8
Lab4_G435.pps
Primary Current-Induced Sedimentary Structures
• Types of bedding (mechanical aggradation)
• Horizontal stratification
– Suspension settling: vertical accretion – Graded bedding:
Mud cracks, clear indication of subaerial exposure
12
Lab4_G435.pps
Biogenic Sedimentary Structures
• Syndepositional modification of sediment by biological agents.
• Ethological approach (environmental conditions determine organisms behavior –> sedimentary record). • Abundance of life. • Types of organisms (plants, animals; Single/ multicellular etc). • Mode of living.
Primary Current-Induced Sedimentary Structures
10
Lab4_G435.pps
• Types of bedding (mechanical aggradation)
– Traction: lateral accretion from bed load
• Cross stratification – Scale » Cross laminations; < 3cm amplitude, < 40 cm λ » Cross beds; > 10cm amplitude, > 10cm λ – Planar tabular cross Strat vs trough cross Strat
7
Lab4_G435.pps
Primary Current-Induced Sedimentary Structures
• Erosional (scour):
– Bedding contacts:
• Sediment removal by currents • Change in depositional regime
13
Lab4_G435.pps
– Biogenic structures influenced by:
Biogenic Structures; Mode of Living
• Discrete burrows:
• Form and shape
– – – – Vertical escape artists: Skolithos Horizontal grazers: Zoophycus/Nereites 3D miners: Cruziana Glossifungites » ―Hard-rock‖ miners: burrows into firm substrate
– May (in conjunction with other facies characteristics) be indicative of Sedimentary Depositional Environment.
• • • • Primary Current Induced structures. Biogenic Structures. Deformational Structures. Secondary Mineralization.
– Bedding:
• lithologic, textural, structural homogeneity indicating discrete time intervals of essentially constant (or constantly changing) deposition
14
Lab4_G435.pps
Biogenic Structures; Mode of Living
• Discrete burrows:
• Form and shape
– Vertical escape artists: Skolithos – Horizontal grazers: Zoophycus/Nereites – 3D miners: Cruziana
Mud cracks, clear indication of subaerial exposure
Lab4_G435.pps
2
Sedimentary Depositional Environments
• Siliciclastic
– Short – Long
• Carbonate
– Rimmed margins – Ramps – Patforms
Lab4_G435.pps
1
Sedimentary Structures
• Features preserved in sedimentary strata that indicate.
• Physical, • Biological, and. • Chemical processes and conditions during and after deposition.
15
Lab4_G435.pps
Biogenic Structures; Mode of Living
• Discrete burrows:
• Form and shape
– – – – Vertical escape artists: Skolithos Horizontal grazers: Zoophycus/Nereites 3D miners: Cruziana Glossifungites » ―Hard-rock‖ miners: burrows into firm substrate
Primary Current-Induced Sedimentary Structures
• Bedding:
• lithologic, textural, structural homogeneity indicating discrete time intervals of essentially constant (or constantly changing) deposition
Sedimentary Structures and Preliminary to Sedimentary Environments
Understanding what sedimentary structures mean in terms of physical, biological, and chemical processes that occurred during, shortly after, and subsequent to deposition is the starting point for the analysis of sedimentary rocks and the environments in which they were deposited. Knowing something about fluid dynamics, ecology, and chemical processes is useful!
• Regular variation in particle size in an individual bed (constantly changing hydrodynamic conditions)
9
Lab4_G435.pps
• Types of bedding (mechanical aggradation)