I. Terrestrial Sedimentary Environments (Continental Realm)
  A. Soil
    Loose material at the surface.
    Contains organic matter. Top soil is humus
    The product of weathering
    Where do we find it ?
 Typically beneath unconformities. They are hard to recognize.
 Plant roots an burrows help identification
 Gives clues about conditions at the surface: burrows= above water table
                                                                              caliche = arid climate
 B. Freshwater Lakes and Glacial Environments
Lakes
Characteristics: indicate excessive run off = abundant rain
        Deposition  on the shore: sands and gravel (coarser materials)
                           in the center: laminated silts and clays
                Associated with river deposits
                Fossils: indicate freshwater, not very abundant
                Layering shows little obliteration

Glacial Environments
    Conditions: snow fall exceeds summer melting.
                       prolonged periods of cold climates

  Valley Glaciers: restricted, few features preserved
  Continental Glaciers:estensive erosion, features preserved.
                Striations (scratches): indicate direction of the flow

    Till : glacial sediment  Sorting: very poor

     Tillite
  Outwash: deposit of reworked till produced by rivers of melt-water. Typically sorted and stratified.
  Dropstones:  boulders carried by the glacier end up rafted on icebergs when the glacier enters a lake. After the ice melts the boulders are dropped in the middle of the lake.

  Glacial lakes: Location at the front of the glacier
          Winter:  lake is frozen => deposition of fines & organic mat.
                  Summer: meltwaters bring coarser material

       Each pair of these layers represents a year's deposition =Varves
 

  C. Desert and Arid Environments
        Where? at subtropical latitudes or the rain-shadow of mountains
        Rivers are ephemeral, with internal drainage.

         Playa lakes: depressions that collect water in the arid environments.
                            Deposits: evaporites, typical structure: mud-cracks
        Alluvial fans fringe the playa lakes and have steep slopes.
                    Braided streams
         What causes the braided pattern?
  Abundance of sediment interferes with transport, channel is forced to switch to another path.

        Dunes: deposited by the wind.
            Migration of dunes produces a trough cross-bedded structure as the wind changes direction.
 
 

  D. River Systems as Depositional Environments

  Alluvial fans in humid environments have gentler slopes.
  Distributary channels of braided streams are separated by high bars.
  Meandering Stream (cut bank, point bar, back swamp)

Sketch
 
 
 
 

             natural levees: coarser deposits flanking the channel originated during floods.

Meander migration may cause sediment of the back swamp to cover the previous point bar.

Walther's Law states that when environments migrate laterally, sediment of one environment come to lie on top of the sediment of the adjacent environment.

Vertical sequence of sediment: coarser at the bottom being covered by finer.

  Deltas: If not eroded they build outward or prograde
   delta plain: sand / silt, horizontal, cross-bedded
  delta front: muds, wood & marine fossils,  inclined seaward
          prodelta: clays, farther into the ocean

The active lobe changes, as the stream chokes on its own sediment.

Deltas sink because of compaction under their own weight

Deltaic Cycles

Vertical sequence of sediment: finer  at the bottom being covered by coarser sediment
(opposite to the meandering river sequence)

II. Marine Realm: Marine Depositional Environments

Characteristics of the Ocean Floor
          (Just kidding)
Continental shelf, continental slope, continental rise, continental breakfast
(sketch)
                                                                                                Abyssal Plain
 

    A. Barrier Island - Lagoon Complex (transition between land and sea)
       Narrow, elongated islands, parallel to the shore, separated by a lagoon

  Origin: longshore currents
  Structure: horizontal layers of sand, may be blown to form dunes.
  Tidal flats, where? along the margins of the lagoon
                 Salinity?: brackish, may become hyper-saline.
                 Fossil faunas' diversity: poor, too different from normal salinity.
            Marshes can develop above the tidal zone.

B. Open Shelf Deposits: Clastics
                                         Carbonates

  Clastic Open Shelf deposits: dominated by currents => sand ridges
                                                dominated by waves => thin sand beds
                                                quieter shelves: sands mix with muds
                                                                        rich in burrowing fauna =>
                                                                                bedding obliterated

    Fossils as environmental indicators
            Low diversity => restrictive salinity
            High diversity & abundant individuals => normal salinity
            High diversity & few individuals => normal salinity but
                         other restrictive conditions may exist such as food scarcity.
Carbonates Open Shelf Deposits:
      Reefs: fringing reef

                     barrier reef

                     patch reef

                     atoll

  Deposits with a central: core unstratified, made by the skeletons.
  broken fragments  Talus: faces the ocean, poorly stratified, tilted to      the sea.
                             Back reef: facing the lagoon, horizontal, poorly      stratified

Carbonate Platforms
  Stand above the sea floor at least on one side
 Were abundant in the past: vast precipitation of carbonates => warm waters

Extensive development of carbonate platforms indicate times when Earth's climates were warmer than today's

Stromatolites: knobby structures of carbonate muds and cyanobacteria mats.
Today they indicate supratidal and hypersaline environments.
        Since three billion years ago (enduring organisms!!!)

  C.   Deep-Sea Marine Deposits
    Turbidity currents: How do they form?
 The product of submarine landslides that deliver sediment from the  edge of the continental shelf to the foot of the continental slope.
 Their deposits make submarine fans, which coalesce to form the continental rise.

Submarine canyons: eroded by the turbidity currents on the continental  slope.
     Name of the deposit: turbidite
     Typical structure: graded bedding.
                   coarser sediment at the bottom, getting finer toward the top.
 

    Difference between these deposits and that of a meandering river?
 meandering river                                    turbidite
 well sorted                                             poorly sorted
 rounded fragments                                  angular fragments
 "cleaner" sandstones                               sandy portion will form graywackes
                                                                (a dirty sandstone)
  Turbidity currents are recurrent, so they erode the deposits of previous ones cutting and filling elongated depressions called sole marks. They are useful to indicate the direction of the flow.

Pelagic sediments: Settle from the waters above the abyssal plain

  clays             from turbidity currents, weathering of submarine volcanoes or carried by the wind.

  biogenic      calcareous ooze: foraminifera and phytoplankton                     (microscopic organisms)
 
 

                       siliceous ooze: diatoms and radiolarians