6 Special Depositional Environments
and Sediments
6.1 Green Marine Clays
Introduction
Remarks to the Nature ofGreen Particles
Greenish Sediments in the Modem Oceans
Summary (Green Marine Clays)
6.2 Oolitic Ironstones
Depositional Environment
Provenance of Iron
Effects of Reworking and Sea Level Changes
Summary (Oolitic Ironstones)
6.3 RedBeds
General Aspects
Primary, Allochthonous Red Beds
In Situ (Secondary) Formation ofRed Beds
Depositional Environments ofBrown and Red Beds
Summary (Red Beds)
6.4 Marine Evaporites
6.4.1 Introduction
6.4.2 Models for Primary Evaporite Deposition
Tbe Closed Sea-Water Basin
Shallow Salt Lagoon (Barred Basin or
Seepage Basin)
Drawdown ofWater Level in Deep Basin
Deep-W ater Salt Basin
Minor Evaporite Cycles Controlled
by Sea-Level Changes
Coastal Sabkhas
Tbe Combined Deep and Shallow/Sabkha
Salt Basin
6.4.3 Examples of Giant Salt Deposits
6.4.4 Varves and Sedimentation Rates ofEvaporites
6.4.5 Sequences and Sedimentary Structures
ofEvaporites
6.4.6 Diagenesis ofEvaporites (Secondary and
Tertiary Evaporites)
Tbe Active Phreatic Zone
Mechanical Compaction and Compaction Flow
Early Cementation
Large-Scale Subsurface Dissolution
Tbermobaric Flow Regime and Phase Changes
of Salt Minerals.
Exhumation of Buried Evaporites
(Tertiary Evaporites)
6.4.7 Trace Elements, Stable Isotopes, and
Accessories in Marine Evaporites
6.4.8 Salt Tectonics
Introduction
Mechanics of Salt Flow
Evolution of Salt Structures
Economic Aspects ofEvaporites and
Salt Structures
6.4.9 Summary (Marine Evaporites)
6.5 Nonactualistic (Precambrian) Depositional
Environments
6.5.1 Introduction
6.5.2 Evolution ofthe Atrnosphere
6.5.3 Evolution ofthe Hydrosphere and Clirnate
6.5.4 Early Life
6.5.5 Precambrian Sediments
Carbonates
Stromatolites, Phosphorites
Bedded Quartzites and Chert
Banded Ironstone Formations
Red Beds
Evaporites
Clastic Deposits
6.5.6 Summary (Precambrian Sediments)
6.1 Green Marine Clays
Introduction
Sediments greenish in color are fairly common in the
present-day oceans at various water depths. Theyare
also frequently observed in ancient sediments, but in
these cases the minerals causing the green color may
differ from those found in young sediments due to
diagenesis. The correct identification, crystallographie and geochemical characterization of finegrained green minerals is difficult and can be done
only in the laboratory using special methods in clay
mineralogy. For simple rock descriptions in the field,
barely more than the greenish color can be noted,
which in turn may be modified by other sediment
components such as organic matter and fine-grained
particles of different composition.
For these reasons and the unavailability in the past of special investigative techniques, much uncertainty existed
about the nature of greenish marine sediments. Most geologists and sedimentologists used the mineral names
glauconite, chamosite, and chlorite for green particles,
which were often poorly defined. In the last decade, how-
and Sediments
6.1 Green Marine Clays
Introduction
Remarks to the Nature ofGreen Particles
Greenish Sediments in the Modem Oceans
Summary (Green Marine Clays)
6.2 Oolitic Ironstones
Depositional Environment
Provenance of Iron
Effects of Reworking and Sea Level Changes
Summary (Oolitic Ironstones)
6.3 RedBeds
General Aspects
Primary, Allochthonous Red Beds
In Situ (Secondary) Formation ofRed Beds
Depositional Environments ofBrown and Red Beds
Summary (Red Beds)
6.4 Marine Evaporites
6.4.1 Introduction
6.4.2 Models for Primary Evaporite Deposition
Tbe Closed Sea-Water Basin
Shallow Salt Lagoon (Barred Basin or
Seepage Basin)
Drawdown ofWater Level in Deep Basin
Deep-W ater Salt Basin
Minor Evaporite Cycles Controlled
by Sea-Level Changes
Coastal Sabkhas
Tbe Combined Deep and Shallow/Sabkha
Salt Basin
6.4.3 Examples of Giant Salt Deposits
6.4.4 Varves and Sedimentation Rates ofEvaporites
6.4.5 Sequences and Sedimentary Structures
ofEvaporites
6.4.6 Diagenesis ofEvaporites (Secondary and
Tertiary Evaporites)
Tbe Active Phreatic Zone
Mechanical Compaction and Compaction Flow
Early Cementation
Large-Scale Subsurface Dissolution
Tbermobaric Flow Regime and Phase Changes
of Salt Minerals.
Exhumation of Buried Evaporites
(Tertiary Evaporites)
6.4.7 Trace Elements, Stable Isotopes, and
Accessories in Marine Evaporites
6.4.8 Salt Tectonics
Introduction
Mechanics of Salt Flow
Evolution of Salt Structures
Economic Aspects ofEvaporites and
Salt Structures
6.4.9 Summary (Marine Evaporites)
6.5 Nonactualistic (Precambrian) Depositional
Environments
6.5.1 Introduction
6.5.2 Evolution ofthe Atrnosphere
6.5.3 Evolution ofthe Hydrosphere and Clirnate
6.5.4 Early Life
6.5.5 Precambrian Sediments
Carbonates
Stromatolites, Phosphorites
Bedded Quartzites and Chert
Banded Ironstone Formations
Red Beds
Evaporites
Clastic Deposits
6.5.6 Summary (Precambrian Sediments)
6.1 Green Marine Clays
Introduction
Sediments greenish in color are fairly common in the
present-day oceans at various water depths. Theyare
also frequently observed in ancient sediments, but in
these cases the minerals causing the green color may
differ from those found in young sediments due to
diagenesis. The correct identification, crystallographie and geochemical characterization of finegrained green minerals is difficult and can be done
only in the laboratory using special methods in clay
mineralogy. For simple rock descriptions in the field,
barely more than the greenish color can be noted,
which in turn may be modified by other sediment
components such as organic matter and fine-grained
particles of different composition.
For these reasons and the unavailability in the past of special investigative techniques, much uncertainty existed
about the nature of greenish marine sediments. Most geologists and sedimentologists used the mineral names
glauconite, chamosite, and chlorite for green particles,
which were often poorly defined. In the last decade, how-