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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.
SITIO PRIMARIO DE DEPÓSITO
SISTEMAS PRINCIPALES
CONTINENTAL
FLUVIAL DESÉRTICOLACUSTREGLACIALVOLCANICLÁSTICO
MARINO-MARGINAL
DELTAICOLAGUNARESTUARIOPLAYABARRAS DE ARENAPLANICIE DE MAREAS
MARINO
PLATAFORMA CARBONATADAPLATAFORMA SILICICLÁSTICAABANICO SUBMARINOPLANICIES ABISALES
Clasificación general de los ambientes de depósito.
http://www.geologia.uson.mx/academicos/grijalva/ambientesfluviales/introduccion.htm
http://www.geocities.com/SiliconValley/Bridge/3339/index50.html
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.
Factores físicos, químicos y biológicos que afectan la sedimentación
Boggs, 1995
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 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.
• facies: the total textural, compositional and structural characteristics of a sedimentary deposit resulting from accumulation and modification in a particular environment.
• grain size, sorting, roundinggrain size, sorting, rounding
• lithologylithology
• sedimentary structuressedimentary structures
• bedding typebedding 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
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
Glacialextremely 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)
http://dept.kent.edu/geology/ehlab/sed_environ/sed_environment.htm
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
Lagoonmud 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
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
Marine Environment
http://dept.kent.edu/geology/ehlab/sed_environ/sed_environment.htm
CONTINENTAL SEDIMENTARY ENVIRONMENTS
ALLUVIAL FAN FLUVIALPALUDAL
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
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
REEFCONTINENTAL
SHELFCONTINENTAL
SLOPE AND RISEABYSSAL 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, cross-bedding
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)
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
Boggs, 1995
Desert Environment (eolian)
Lakes
Boggs, 1995
Boggs, 1995
Glacial
Boggs, 1995
Delta
Walker, 1984
Walker, 1984
Lewis and McConchie, 1994
Boggs, 1995
Beach/ barrier bar
Walker, 1984
Boggs, 1995
Playa
Estuario
Boggs, 1995
Reineck and Singh, 1980 Boggs, 1995
Lagoon
Boggs, 1995
Tidal Flat
Boggs, 1995
Marine Environment
Lewis and McConchie, 1994
• Shallow seas can be subdivided into clastic and carbonate-dominated 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/
Shallow marine environments
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/
Boggs, 1995http://www.uic.edu/classes/geol/eaes350/
Boggs, 1995
Arrecifal
Walker, 1984
Walker, 1984
Boggs, 1995
Walker, 1984
Talud
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/
Reineck and Singh, 1980
Abanico Submarino
Reineck and Singh, 1980
Turbiditas
