Carbonates 2 Flashcards
Discuss the back ramp in as much detail as you can.
Supratidal area above high water mark so is subaerial. If it is an arid environment you can have mudcracks, if wet you have karst or soils present.
Within the back ramp you can have 2 other areas what are they called?
Sabhka and low energy environment (intertidal)
May be a sabkha which will be an arid equatorial environment, when the sea water starts to evaporate you will be left with Gypsum, if it is buried and the water is driven off you’ll get halite.
Low energy environment in the intertidal zone below high water mark; can have mangrove swamps and algal mats
What are the two parts of the shallow ramp? Discuss them to the best of your ability and what you find within them.
Beach barriers and shallow subtidal
Beach barriers can have lagoons behind them, they are wave dominated and can have cross bedding present. You get oolitic, skeletal and peloidal sands here.
Shallow subtidal are infront of the beach barriers, wave dominated. Has cross bedding and bioturbation occurring. The flow of water goes opposite direction to a fluvial systems. Tends to have interbedded bioclastic and oolitic grainstones with algal laminated muds.
In the deeper subtidal areas which dunham classifications dominate?
Packstones and mudstones.
Discuss the carbonate ramp in relation to oil generation and preservation.
The basin has carbonaceous sediments with deep water shales which are good potential source rocks. The ramp sediments act as good reservoir rocks. Ontop of the sabkha where there are anhydrites they can act as a seal.
Give an example of a modern day rimmed shelf
Great Barrier Reef, Australia
Give an example of a modern day carbonate ramp
Gulf of Mexico where the Arabian plate is underneath the Eurasian plate.
Describe a rimmed shelf
A shallow water platform with a pronounced break of slope into deeper water
Discuss the 2 different types of reefs and how they are formed. Where are these reefs located?
Skeletal Reef: Created by corals, calcareous algae and stromatoparoids; they are in situ frame builders.
Reef Mound: Forms biogenically and lacks prominent skeletal framework, builds by trapping of material at algal mats.
Reefs located in elevated solid substrate as most reef builders are filter feeders, will be above settling sediment and around the shelf margin or at a lagoon/patch reef as many have different niches.
what are the 3 types of reef morphology?
Barrier Reef: Like Great Barrier Reef or Belize reef
Pinnacle Reef: Isolated, formed in deep water.
Patch Reef: Back barrier, lagoonal.
Discuss the major differences between ramps and rimmed shelves
Rimmed shelves have a well defined slope where slope sedimentation processes act along with accumulation.
The rimmed shelf has a thinner margin which is only a few hundred metres wide.
Discuss slope deposits. Name some processes involved.
The rimmed shelf has line margins where accumulation takes place, it falls into the basin due to a lack of accomodation space. This is shown by the Base of Slope Apron Model, where there is a mixture of benthic and pelagic fauna on the basin floor.
Processes involved include slides and slumps, sediment gravity flows and rock falls.
When is the Base of Slope Apron Model most useful?
When studying ancient deep water carbonates.
Discuss in as much detail as you can isolated platforms
They are detached and form as shallow water platforms surrounded by deeper water. Their facies distributions are affected by prevailing winds and storm directions.
Atolls are a certain type of isolated platform which has a reefal system and central deeper lagoon.
what can all carbonate facies be strongly modified by?
Diagenesis
