| GE |
|
PIX |  |
 |
 |
 |
 |
 |
| Geological photographs from around the world | ||||||||
In an environment of marine deposition, the sediments and fauna depend on the
- depth of water;
- strength of the current;
- temperature of the water.
A number of factors are inter-related. For example, shallow water is more likely to be turbulent, which will
bring in food (plankton) and oxygen, encouraging more animals. On the other hand, turbulence may make the water
muddy and murky, preventing the growth of certain organisms such as corals.
Taken together, the rock type (lithology) and associated fauna and flora (fossils) can be given the name of a
particular facies, for example the graptolite shale facies of the Lower Palaeozoic.
The main types of marine environments include:
SHALLOW MARINE: clastic
Shallow water implies that the sea floor is influenced by wave action, currents and tides. In some cases, an ancient beach deposit can be identified, and therefore the position of the coast identified for that geological time.
|
Rock types conglomerate, sedimentary quartzite, glauconitic sandstone Sedimentary structures symmetrical ripples Fossils shelly fauna adpated to the turbulent waters of the light zone Other points often associated with unconformities |
 |
SHALLOW MARINE CARBONATE: High Energy
|
Rock types bioclastic limestone, oolitic limestone Sedimentary structures occasional cross-bedding Fossils shelly fauna adpated to the turbulent waters of the light zone |
 |
SHALLOW MARINE CARBONATE: Low Energy
|
Rock types calcite mudstone, chalk Fossils may not be present if the water is too 'salty' due to evaporation; thin shelled; well preserved |
 |
SHALLOW MARINE CARBONATE: Reefs
A reef is an unusual environment in that the structure of the reef is preserved in its entirity. Most other deposits are the broken-up remains of pre-existing structures.
|
Rock types limestone Sedimentary structures unbedded Fossils shelly fauna find sheltered niches within the reef Other points not all reefs are coral reefs; algae often acts as a binder for the sediment |
 |
DEEP MARINE
|
Rock types fine grained clay and shale, greywacke/turbidite Sedimentary structures thin bedded; graded bedding in turbidites Fossils too deep (cold, little food or oxygen) for benthonic (bottom-living) fauna; fossils are from pelagic fauna which sank to the sea floor on death |
 |
Geopix Study Guide "Marine Environments" sumarises the following environments:
- shallow marine; clastic;
- shallow marine carbonate - high energy;
- shallow marine carbonate - low energy;
- shallow marine carbonate - reef;
- deep marine;
- gives examples from modern and ancient environments;
- outlines the use of graphic logs;
- suggests how to answer exam questions on this topic.
The Marine Environments Study Guide contains the following pages:
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
|
|
To order this CD go to the Geopix Online Store