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14.3: Putting it all together - facies models

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    Although many models exist, here we will discuss a range of commonly preserved sedimentary depositional environments, starting with terrestrial environments at the highest elevations on the continents, moving toward the coast, into marine environments of the continental shelf and onto the abyssal plains. The focus will be on the four facies model characteristics that are most observable in hand samples.

    Terrestrial depositional environments

    Alpine glaciers

    Meltwater and lateral moraine till
    Figure \(\PageIndex{1}\): Meltwater and lateral moraine till, Athasbasca Glacier, Banff National Park, Canada. (Photo by K. Layou.)
    • Color: variable depending on landscape
    • Composition: lithics
    • Texture: gravel to clay, poorly sorted, angular to subrounded
    • Sedimentary structures: may see some asymmetric cross-bedding in association with outwash deposits
    • Fossils: rare
    • Other notes: till, moraine deposits

    Alluvial fan

    Am Magh, the alluvial fan that divides Lochan na h-Earba into two lakes, Scotland.
    Figure \(\PageIndex{2}\): Am Magh, the alluvial fan that divides Lochan na h-Earba into two lakes, Scotland. (CC BY-SA 2.0; Richard Webb)
    • Color: tan to pink-red
    • Composition: primarily feldspars and lithics
    • Texture: gravel to clay, poorly sorted, angular to subrounded
    • Sedimentary structures: generally absent
    • Fossils: rare
    • Other notes: massive beds common from one flow

    Braided rivers

    Braided river
    Figure \(\PageIndex{3}\): Braided river deposits, Banff National Park, Canada. (Photo by K. Layou.)
    • Color: tan to gray
    • Composition: primarily lithics, also quartz and feldspars
    • Texture: gravel and sand, subangular to subrounded, poor to moderate sorting
    • Sedimentary structures: asymmetric cross-beds
    • Fossils: larger, robust fossils, commonly plants and vertebrates
    • Other notes: gravel and sand bars (lenticular beds)

    Lakes

    Loch an Eilean, lake near Aviemore, Scotland
    Figure \(\PageIndex{4}\): Loch an Eilean, lake near Aviemore, Scotland. (Photo by K. Layou.)
    • Color: gray to black
    • Composition: siliciclastic minerals (quartz, clay minerals from weathering)
    • Texture: clay to silt, well-sorted
    • Sedimentary structures: laminations
    • Fossils: fish, insects, plants leaves/flowers, pollen
    • Other notes: some carbonate sediment may be possible (tufas)

    Deserts

    Photography of a sand dune. A person walks along its crest, toward a single lone tree.
    Figure \(\PageIndex{5}\): Elim Dune, Namibia. (Photo by Ron Bentley)
    • Color: white to light pink or orange
    • Composition: primarily quartz, hematite cements, evaporites
    • Texture: sand, subrounded to rounded, well-sorted
    • Sedimentary structures: large-scale asymmetrical ripples and cross-beds
    • Fossils: vertebrates, some plants
    • Other notes: sand grains may show some frosting from air abrasion

    Meandering rivers

    Meanders of Taskinas Creek, York River State Park, Virginia
    Figure \(\PageIndex{6}\): Meanders of Taskinas Creek, York River State Park, Virginia. (Photo by K. Layou.)
    • Color: brown to reddish purple
    • Composition: lithics and quartz
    • Texture: sand to clay, subrounded, moderate sorting
    • Sedimentary structures: unidirectional cross-beds, asymmetric ripples in channel; mudcracks, raindrop impressions on floodplain
    • Fossils: terrestrial fish and other vertebrates, plants and roots
    • Other notes: coarser sediment in the channel, finer grained material in the floodplain (coarse lenses in finer sediments in outcrop scale)

    Transitional/coastal depositional environments

    Deltas

    • Color: brown to reddish purple
    • Composition: lithics and quartz
    • Texture:sand to clay, subrounded, moderate sorting
    • Sedimentary structures: unidirectional cross-beds, asymmetric ripples in channel; mudcracks, raindrop impressions on floodplain
    • Fossils: coastal plants (i.e. marsh grasses) and roots, marine fish, shells
    • Other notes: coarser sediment in the channel, finer grained material in the floodplain, large foreset (incline beds) at outcrop scale

    Beaches

    Shoreline of beach at Cape Charles, Virginia
    Figure \(\PageIndex{7}\): Shoreline of beach at Cape Charles, Virginia. (Photo by K. Layou.)
    • Color: white to tan
    • Composition: primarily quartz, heavy minerals OR calcite
    • Texture: moderate to well sorted sand, subrounded to rounded, moderate to well-sorted
    • Sedimentary structures: symmetrical ripples, bidirectional cross-beds
    • Fossils: shells
    • Other notes: may see abundant shells and ooids in carbonate settings

    Marine depositional environments

    Tidal flats

    Symmetrical ripples, tidal flat, Sapelo Island, Georgia
    Figure \(\PageIndex{8}\): Symmetrical ripples, tidal flat, Sapelo Island, Georgia. (Photo by K. Layou.)
    • Color: light gray to tan
    • Composition: quartz and clay minerals OR calcite
    • Texture: silt to clay, subrounded, well-sorted
    • Sedimentary structures: mudcracks, bidirectional ripples
    • Fossils: stromatolites, snails, crustaceans and burrows
    • Other notes: may see laminations if burrows not present

    Shallow subtidal (upper shoreface)

    Shallow carbonate marine environment, Bahamas
    Figure \(\PageIndex{9}\): Shallow carbonate marine environment, Bahamas. (Photo by K. Layou.)
    • Color: gray to tan
    • Composition: quartz and clay minerals OR calcite
    • Texture: sand to clay, subrounded, well-sorted
    • Sedimentary structures: hummocky beds, burrows
    • Fossils: wide variety of invertebrates, fish, reefs in carbonate marine settings
    • Other notes: may produce massive beds due to bioturbation; area of shelf affected by fairweather waves

    Deep subtidal (lower shoreface)

    • Color: dark gray to dark brown
    • Composition: quartz and clay minerals OR calcite
    • Texture: silt to clay
    • Sedimentary structures:
    • Fossils: wide variety of invertebrates, fish
    • Other notes: area of shelf affected by storm waves may show evidence of storm deposits (more broken shells)

    Offshore

    • Color: dark gray
    • Composition: quartz and clay minerals OR calcite
    • Texture: silt to clay
    • Sedimentary structures: laminations
    • Fossils: planktonic microfossils, ammonites, vertebrates
    • Other notes: area of shelf below storm wavebase

    Submarine fan

    • Color: dark gray
    • Composition: quartz and clay minerals OR calcite
    • Texture: silt to clay
    • Sedimentary structures: Bouma sequences from turbidity currents
    • Fossils: planktonic microfossils, ammonites, vertebrates
    • Other notes: deposits will be thin as they are farther away (more distal) from sediment source

    Abyssal plains

    • Color: dark gray to black
    • Composition: quartz (chert), calcite (chalk/micrite), clay minerals
    • Texture: clay
    • Sedimentary structures: laminations
    • Fossils: planktonic microfossils, ammonites, vertebrates
    • Other notes: deep sea sediments capping basalt of oceanic crust

    This page titled 14.3: Putting it all together - facies models is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by Callan Bentley, Karen Layou, Russ Kohrs, Shelley Jaye, Matt Affolter, and Brian Ricketts (VIVA, the Virginia Library Consortium) via source content that was edited to the style and standards of the LibreTexts platform.