theImage.com     Notes on Basic Geology
Notes created & information organization based on the book:
"The Dynamic Earth - an introduction to physical geology"
Brian Skinner & Stephen C. Porter   (further book information here)
also look at www.wiley.com for additional resource information
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Sediments & Sedimentation - Page 5

Sedimentary Facies

Facies : the changes in depositional environment between separable phases of deposit. These can be used to determine something about the conditions that existed as the sediment was deposited. It may reflect changes in texture, rate of deposit, chemistry, or a combination of these.

These are tools used to deconstruct a layered sediment. They aid n defining the time line and history of the earth at the time the deposits were created. Sometimes the phase changes can be very smooth and not well defined. At other times there may be an abrupt change in the relationship of two sediments. This too helps in the determination of the sediments history.
Land based environments

Type of
Sediment

Stream

The stream transport is variable based on the age or location of the stream. Water with a higher gradient (more speed and straighter) tends to move larger material until the gradient diminishes. Slower moving streams that are older or farther from mountains wind lazily along further reducing their gradient, and hence cannot carry coarse material. Larger size material is found near younger streams or higher mountains. Better differentiated and smaller material is found where there is less water flow.

Lake

Lake deposits shoe more change around their edges where they are worked by tributary streams and where the wind can stir up the lake bed in the shallows. The deposits at the center of the lake tend to be fine grained from slow deposition or chemically different from lack of sunlight penetration.

Glacial

Glaciers may deposit materials along their edges or at their ends as they melt back. Since the ice can handle virtually any size material and the volume (center cross section) of a glacier has little abrasive force, the resultant deposits are widely varied in size and chemistry. Only at the bottom of the glacier and on the side walls where is fills the valley completely will there be much differentiation (grinding).

Eolian

Aeolus, the Greek god of the wind. Wind blown sediment has to light and fine by its nature. Since it occurs mainly in desert or low plant life environments, any water that passes through it will tend to dissolve all but the sturdiest material. The grain gradation may be more in the vertical direction over a distance than the horizontal direction if wind directions were prevalent.
Water based environments

Type of
Sediment

Estuarine

A semi enclosed body of water where it is partially protected from the sea, but the water mixes with sea water forming a brackish environment. Brackish water promotes some grain growth and hence precipitation of clay particles.

Deltaic

Deposit formed at the point where a river runs directly into the ocean. The center of a delta is usually more granular as it is created fro from the deepest and fastest moving water. As it continues outward it automatically grades the material from coarser to finer.

Beach

Beach sediments are continually worked over by wave action, and thus among the best sorted material there is. It tends to me made up of silica unless there the beach is adjacent to a stream inlet or a reef. On average beach sand is silica as it is the toughest material.

Offshore

The continental shelves receive much of the remaining suspended sediment as it slowly sinks, only about 10% ever reaches the deep oceans. There may be patches of even more coarse material along the shelves as the ocean has advanced and retreated over millions of years. When it has retreated, then streams carry coarse material farther out on to the shelves. It is soon covered by finer material as the ocean advances again.

Carbonate shelve

Carbonate shelves are formed where the water temperature can remain elevated and the sun con penetrate too the sea floor. They are mainly along the continental shelves, around islands, or near the top of the ocean mounts. They rely on solar energy to provide the climate for abundant sea life growth.

Marine Evaporite basins

these are area in the ocean that once evaporated faster than they could be refilled by fresh water streams around their parameters. They may often have been trapped sea water as the sea withdrew from an area.

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