AMBIENTE SEDIMENTARIO: conjunto de procesos físicos, químicos y biológicos
que afectan la sedimentación (Fraser, 1989).
Se reconocen tres sitios primarios para el depósito de sedimentos:
(1) Continental, (2) Marino-marginal o transicional, y (3) Marino.
Cada uno de éstos se encuentra dividido en diferentes sistemas de depósito, así
como en una serie de ambientes y sub-ambientes asociados.
Clasificación general de los ambientes de depósito.
SITIO PRIMARIO
DE DEPÓSITO
CONTINENTAL
http://www.geocities.com/SiliconValley/Bridge/3339/index50.html
SISTEMAS
PRINCIPALES
FLUVIAL
DESÉRTICO
LACUSTRE
GLACIAL
VOLCANICLÁSTICO
MARINO-MARGINAL
DELTAICO
LAGUNAR
ESTUARIO
PLAYA
BARRAS DE ARENA
PLANICIE DE MAREAS
MARINO
PLATAFORMA
CARBONATADA
PLATAFORMA
SILICICLÁSTICA
ABANICO SUBMARINO
PLANICIES ABISALES
http://www.geologia.uson.mx/academicos/grijalva/ambientesfluviales/introduccion.htm
Factores físicos, químicos y biológicos que afectan la sedimentación
Factores físicos: incluyen aspectos dinámicos como la velocidad. dirección y
variaciones en el movimiento del fluido que condicionan el medio; corrientes
de agua. oleaje, mareas. vientos. etc.. asi como los parámetros geográficos y
climáticos del mismo, como tipo de meteorización, clima, temperatura,
humedad, frecuencia de las heladas, precipitación. etc.
Factores químicos: condiciones de pH y eH del medio, la geoquímica de la
roca madre y la interacción química entre el sedimento y el ambiente;
principalmente en los subacuáticos.
Factores biológicos: tipo de flora y fauna y su influencia en los procesos
sedimentarios, formación de suelos, erosión, etc., así como las
correspondientes interacciones con el ambiente que puede motivar la
individualización de algún medio sedimentario.
Boggs, 1995
facies are a body of rock with specified characteristics. [Reading (1996)]
Ideally, a facies is a distinctive rock unit that forms under certain conditions of
sedimentation, reflecting a particular process or environment.
The concept of facies goes back to Armand Gressly (1830), who used the term to
designate rocks of different aspect within a particular stratigraphic unit. The idea of
facies sequences was emphasized by Johannes Walther (1896), and since about
1965, facies sequences of various types have been a standard part of
sedimentological interpretation.
•
facies: the total textural, compositional and structural
characteristics of a sedimentary deposit resulting from
accumulation and modification in a particular
environment.
•
grain size, sorting, rounding
•
lithology
•
sedimentary structures
•
bedding type
Ley Facies de Walter
Johannes Walther, states that
the vertical succession of facies
reflects lateral changes in
environment.
Conversely, it states that when a
depositional environment
"migrates" laterally, sediments of
one depositional environment
come to lie on top of another.
http://higheredbcs.wiley.com/legacy/college/levin/0471697435/chap_tut/chaps/chapter05-11.html
http://dept.kent.edu/geology/ehlab/sed_environ/sed_environment.htm
CHARACTERISTICS OF NON-MARINE ENVIRONMENTS USEFUL IN
IDENTIFICATION OF DEPOSITIONAL ENVIRONMENT
Alluvial fan
lots of coarse particles, usually sandstone and conglomerate, poor sorting, deposited by
high energy floods or mudflows
Fluvial (stream channel)
sandstone and conglomerate, ripple marks and cross-beds, graded bedding
Fluvial (floodplain)
usually plane bedding, fine-grained sand, silt, and clay,
Paludal (swamps)
dominantly fine-grained, coal common
Lacustrine (lakes)
beaches along edge; coarse-grained, well-sorted sandstone, sediments in lake are finer
grained, can find evaporites such as gypsum and halite
Glacial
extremely poorly sorted, usually coarse material in moraines, better sorting in outwash
deposits, large cobbles may be striated
Aeolian (desert)
sand usually fine-grained, very large scale cross-bedding, well sorted, usually well
rounded and frosted, rocks may be polished and faceted (windblown)
Transitional Environments
Beach
sizes range from cobbles to fine sand,
well sorted and well-rounded,
may be plane bedded or cross-bedded dunes
Estuary and Tidal Flats
water level rises and falls depending on tides,
ripples will stack on top of each other in opposite directions
mud drapes common, often find a mix of marine and non-marine animals,
tidal flats may have mud cracks
Lagoon
mud and silt common
occasional sandy layers deposited by storms
highly bioturbated
oyster hash common
http://dept.kent.edu/geology/ehlab/sed_environ/sed_environment.htm
Marine Environment
Shallow marine (less than 200 meters)
reef structures
limestone, dolomite, and gray shale common
sediments rich in glauconite and phosphate
Deep marine (greater than 200 meters)
graded gray sandstone
interbedded with gray shale
bedded chert
http://dept.kent.edu/geology/ehlab/sed_environ/sed_environment.htm
CONTINENTAL SEDIMENTARY ENVIRONMENTS
ALLUVIAL FAN
PALUDAL
FLUVIAL
Rock Type
Breccia,
conglomerate,
arkose
Conglomerate,
sandstone, siltstone,
shale
Peat, coal, black
shale, siltstone
Composition
Terrigenous
Terrigenous
Terrigenous
Color
Brown or red
Brown or red
Black, gray, or
brown
Grain Size
Clay to gravel
Clay to gravel (Fining
upward)
Clay to silt
Grain Shape
Angular
Rounded to angular
---
Sorting
Poor
Variable
Variable
Inorganic Sedimentary Structures
Cross-bedding and
graded bedding
Asymmetrical ripples,
cross-bedding, graded
bedding, tool marks
Laminated to
massive
Organic or Biogenic Sedimentary
Structures
---
Tracks, trails,burrows
Root marks,
burrows
Fossils
---
Rare freshwater shells,
bones, plant fragments
Plant fossils, rare
freshwater shells,
bones, fish
http://facstaff.gpc.edu/~pgore/geology/historical_lab/environmentchart.htm
TRANSITIONAL SEDIMENTARY ENVIRONMENTS
DELTA
BARRIER BEACH
LAGOON
TIDAL FLAT
Rock Type
Sandstone,
siltstone, shale, coal
Quartz arenite,
coquina
Siltstone, shale,
limestone, oolitic
limestone or gypsum
Siltstone, shale,
calcilutite, dolostone
or gypsum
Composition
Terrigenous
Terrigenous or
carbonate
Terrigenous,
carbonate, or
evaporite
Terrigenous,
carbonate, or
evaporite
Color
Brown, black, gray,
green, red
White to tan
Dark gray to black
Gray, brown, tan
Grain Size
Clay to sand
(Coarsening upward
Sand
Clay to silt
Clay to silt
Grain Shape
---
Rounded to angular
---
---
Sorting
Poor
Good
Poor
Variable
Inorganic
Sedimentary
Structures
Cross-bedding,
graded bedding
Cross-bedding,
symmetrical ripples
Lamination, ripples,
cross-bedding
Lamination,
mudcracks, ripples,
cross-bedding
Organic or
Biogenic
Sedimentary
Structures
Trails, burrows
Tracks, trails,
burrows
Trails, burrows
Stromatolites, trails,
tracks, burrows
Fossils
Plant fragments,
shells
Marine shells
Marine shells
Marine shells
http://facstaff.gpc.edu/~pgore/geology/historical_lab/environmentchart.htm
MARINE SEDIMENTARY ENVIRONMENTS
REEF
CONTINENTAL
SHELF
CONTINENTAL
SLOPE AND RISE
ABYSSAL PLAIN
Rock Type
Fossiliferous
limestone
Sandstone, shale,
siltstone, fossiliferous
limestone, oolitic
limestone
Litharenite,
siltstone, and shale
(or limestone)
Shale, chert, micrite,
chalk, diatomite
Composition
Carbonate
Terrigenous or
carbonate
Terrigenous or
carbonate
Terrigenous or
carbonate
Color
Gray to white
Gray to brown
Gray, green, brown
Black, white red
Grain Size
Variable,
frameworks, few
to no grains
Clay to sand
Clay to sand
Clay
Grain Shape
---
---
---
---
Sorting
---
Poor to good
Poor
Good
Inorganic
Sedimentary
Structures
---
Lamination, crossbedding
Graded bedding,
cross-bedding,
lamination, flute
marks, tool marks
(turbidites)
Lamination
Organic or Biogenic
Sedimentary
Structures
---
Trails, burrows
Trails, burrows
Trails, burrows
Fossils
Corals, marine
shells
Marine shells
Marine shells, rare
plant fragments
Marine shells
(mostly microscopic)
http://facstaff.gpc.edu/~pgore/geology/historical_lab/environmentchart.htm
Boggs, 1995
SISTEMA FLUVIAL
Los depósitos fluviales están constituidos por sedimentos que se acumulan a
partir de la actividad de los ríos y los procesos de deslizamiento por gravedad
asociados. Aunque estos depósitos se están generando actualmente bajo una
diversidad de condiciones climáticas, desde desérticas hasta glaciales, se
reconocen cuatro sistemas fluviales bien definidos: (1) sistema de abanicos
aluviales (alluvial fans), (2) sistema de ríos trenzados (braidded), (3) sistema de
ríos meándricos (meandering), y (4) sistema de ríos anastomosados
(anastomosing).
Diferentes tipos de canales dentro de los sistemas fluviales
http://www.geologia.uson.mx/academicos/grijalva/ambientesfluviales/introduccion.htm
ALLUVIAL FAN DEPOSITS
Boggs, 1995
Boggs, 1995
Walker, 1984
Boggs, 1995
Meandering stream
Walker, 1984
Walker, 1984
Desert Environment (eolian)
Boggs, 1995
Lakes
Boggs, 1995
Boggs, 1995
Glacial
Boggs, 1995
Delta
Walker, 1984
Walker, 1984
Lewis and McConchie, 1994
Boggs, 1995
Beach/ barrier bar
Walker, 1984
Playa
Boggs, 1995
Estuario
Boggs, 1995
Reineck and Singh, 1980
Boggs, 1995
Lagoon
Boggs, 1995
Tidal Flat
Boggs, 1995
Marine Environment
Lewis and McConchie, 1994
Shallow marine environments
• Shallow seas can be subdivided into clastic and carbonatedominated systems, depending mainly on sediment supply and
climatic setting
• Idealized models predict a general decrease of grain size with
water depth (i.e., away from the shoreline); however, this
simple picture is complicated by a large number of factors (e.g.,
shelf bathymetry)
http://www.uic.edu/classes/geol/eaes350/
Walker, 1984
Shallow Carbonate marine environments
• Shallow seas within the photic zone are the premier ‘carbonate
factories’
• Carbonate platforms can cover continental shelves or
epicontinental seas, when the conditions for carbonate
production (temperature, salinity, light conditions) are favorable
• Isolated platforms (atolls) are found in shallow seas surrounded
by deep water, like extinct volcanoes
http://www.uic.edu/classes/geol/eaes350/
Lewis and McConchie, 1994
Boggs, 1995
http://www.uic.edu/classes/geol/eaes350/
http://www.uic.edu/classes/geol/eaes350/
http://www.uic.edu/classes/geol/eaes350/
Boggs, 1995
Arrecifal
Walker, 1984
Boggs, 1995
Boggs, 1995
Talud
Walker, 1984
Deep marine environments
• The continental slope is a major source of sediment for the deep sea, and
is a setting where slumps can occur
• Debris flows and turbidity currents are the main mechanisms of transport
from the continental slope into the deep sea; these processes can be
triggered by external forcing (e.g., an earthquake) or by the slope
reaching a critical state as a result of ongoing deposition
• Debris-flow deposits and turbidites are often genetically related
• Turbidites can be both clastic (commonly leading to the formation of
wackes) or calcareous
• Pelagic sediments primarily have a biogenic origin
• Calcareous ooze (e.g., foraminifera) forms above the calcite compensation depth
(CCD) at ~4000 m depth
• Siliceous ooze (e.g., radiolarians, diatoms) forms between the CCD and ~6000 m
depth where silica dissolves; it lithifies into cherts
• Hemipelagic sediments consist of fine-grained (muddy) terrigenous
material that is deposited from suspension
• Eolian dust is an important component (~50%) of hemipelagic (and pelagic)
facies
• Black shales have a 1-15% organic-matter content and form in anoxic bottom
waters
http://www.uic.edu/classes/geol/eaes350/
Abanico Submarino
Reineck and Singh, 1980
Turbiditas
Reineck and Singh, 1980
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Marine Environment