Sunday, September 14, 2014

Depositional Environments

There are many environments and every one has it's own characteristics. Every single depositional system have many environments where sediments deposits. On a broader sense there are three main types of depositional environments.
  1. Continental
  2. Terrestial
  3. Marine


Continental of-course the name simplifies it in understanding, it is the all environments on the continent. Continental environments include 
  • Glacial 
  • Lacustrine
  • Fluvial
  • Dessert


Glacial environments are those related to snow and ice. When it snows on the continent or mountain ranges after certain time snow becomes more rigid and become ice. The ice melting water carry sediments with itself and these deposits are then glacial deposits. Snow and ice creeps along the slopes where it carries sediments and boulders along itself and deposits where it velocity decreases. As ice can carry sediments to boulders therefore it's deposits are not sorted (fining upward), it's deposit can be distinguished by unsorting called tillites. 


Lacustrine are the deposition in lakes. The sediments coarser to finer according to the streams power to carry sediments are deposited in the lakes. As to the gravity action the coarser sediments deposits first and then the finer particles therefore it gives a fining upward succession. Coarser are at the base and fine upward.


Fluvial deposits are the water channels deposition. These can be in the streams and rivers. Water manages to carry load from boulder to fine sediments according to the velocity of the water. Boulders are usually carried to a certain distance in a mountain ranges sometimes during flooding the capacity increases where water possess huge velocity. Water dumps it's load where the velocity breaks  As velocity decrease will first deposit coarser sediment and then finer, it also have fining upward succession.


Desert are the places where average rainfall is less than 25mm/year. So any deposition in such areas are considered as dessert deposits. In dessert mostly deposition is aeolian (wind). Wind takes finer sediments with itself and deposits elsewhere when wind speed breaks. The sediments are rounded as the corners are round by friction.


These are environments that are present in the junction of marine and continent. These includes
  • Delta
  • Lagoon
  • Beach


Delta deposits are those of the rivers mouth. Rivers carry continental sediments and are deposited where rivers open into sea/ocean. The coarser sediments are deposited at the early opening of river mouth where water velocity breaks and finer sediments are carried along water to the sea/ocean. Water channels are present like birds feet as water moves along different direction. 


Lagoon environments are those when sea/ocean water moves landward and it separates from main water body. These separated water makes environment where sediments deposits on continent.


Beach deposits are the terrestial environments on the onshore. Here deposits are mainly sand particles and some finer sediments are also present.


Marine environment as name indicates it is the deposition in the sea/ocean, open water body. These includes
  • Continental shelf
  • Continental slope
  • Open marine

Continental shelf

Continental shelf is the shallow marine environment where landmass from continent is submerged by ocean water. These environments comes in marine as landmass in submerged by water. Continental shelf has major deposits of sand, clay  and corals. Coral reefs live in colonial form and are mostly on the continental shelf, shallow marine environment.

Continental slope

Continental slope is environment where continental landmass slopes into sea/ocean. Deposition on this slope are referred as continental slope deposits which are finer sediments. These sediments can be reworked by turbiditic currents to open marine environments. 

Open marine

Open marine environment is the overall ocean deposits where it starts after continental slope. This environment deposits are from finer to coarser, organism remains, basalts etc in deposit. All animal living in free water are deposited in open marine along with sediments (Continental and terrestial). These sediments supply are deposited in ocean.