SEDIMENTARY ENVIRONMENTS

I. Terrestrial Sedimentary Environments (Continental Realm)

    Gives clues about conditions at the surface: burrows
                                                                              caliche
  B. Freshwater Lakes and Glacial Environments
    Lakes
Characteristics: indicate ____________ run off = abundant _________
        Deposition: on the shore ____________
                          in the center________________________
                Asociated with ____________________
                    Fossils:
                 Layering shows __________ obliteration

    Glacial Environments
    Conditions: snow fall exceeds _________ ________.
                        ___________ periods of cold climates

    Valley Glaciers
    Continental Glaciers
                Striations (scratches)

    Till :__________ __________. Sorting: very ____________

     Tillite

•  Outwash: deposit of reworked till produced by rivers of ____________. Typically _______

•  Dropstones:  boulders carried by the glacier end up __________________ when the glacier enters a lake. After the ice melts _________________

 
• Glacial lakes: Location _______________

                      Winter:  lake is frozen => deposition of ____________
                       Summer: meltwaters bring ___________ material

  C. Desert and Arid Environments
        Where?
        Rivers are ________________, with ____________ drainage.

        Playa lakes: depressions that collect water in the arid environments.
                            Deposits: evaporites, typical structure mud-________
        Alluvial fans fringe the playa lakes and have _________ slopes.
                    Braided streams
          What causes the braided pattern?
 

        Dunes: deposited by the __________.
            Migration of dunes produces a _________-bedded structure

  D. River Systems as Depositional Environments

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

 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

         natural levees

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: ______at the bottom being covered by finer

• Deltas: If not eroded they build ___________ or prograde
• delta plain
• delta front
• prodelta

Deltas sink because ______________________________

Deltaic Cycles

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

II. Marine Realm: Marine Depositional Environments
A great site from the Smithsonian Institution: Ocean Planet
 

Characteristics of the Ocean Floor

    Continental shelf, continental slope, continental rise, continental breakfast

    A. Barrier Island - Lagoon Complex
       Narrow, elongated islands, _________ to the shore, separated by a _______

•         Origin: longshore currents
•         Structure: horizontal layers of sand, may be blown to form _______.
•         Tidal  ___________, where? _______________
•         Salinity?: _____________, may become hyper _______
•         Fossil faunas' diversity: _______________
•         Marshes can develop ________ 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 => _____________ salinity
        High diversity & abundant individuals => _____________
        High diversity & few individuals => ________ salinity but
                     other restrictive conditions may exist such as ________.
 
 

                   barrier reef

                   patch reef

                   atoll

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

    Carbonate Platform
    Stand above the sea floor at least on one side
        _______________: vast precipitation of carbonates => ____________ waters

    Stromatolites: knobby structures of carbonate muds and _______________.
        Indicate supratidal and hypersaline environments.
        Since __________ billion years ago (enduring organisms!!!)
 
 
 

  C.   Deep-Sea Marine
    Turbidy currents: How do they form?
 
 
 
 

     Submarine canyons: eroded by the turbidity currents on the _________ slope.
     Name of the deposit: turbidite
     Typical structure: ___________ ______________.
                    ___________ at the bottom, getting ________ toward the top.
 

    Difference between these deposits and that of a meandering river?
 
 
 

• Turbidity currents are recurrent, so they erode the deposits of previous ones cutting elongated depressions called ________ _________. They are useful to indicate the direction of the flow.

clays from ______________________________

 

 

biogenic          Calcareous ooze

 

 
 
 
 
 
 
 
 

                      Siliceous  ooze