What depositional environment does black shale form in?
anoxic marine environment
The black shales in the Qusseir area (Duwi Formation, Campanian–Maastrichtian) were deposited in an anoxic marine environment, and are remarkably high in their enrichment of redox-sensitive and sulfide-forming trace metals.
Why are Paleozoic black shales important?
Because of their often large extent, ancient black shale strata represent one of the most significant crustal reservoirs of organic carbon and sulfur, and potential resources of many metals, including so-called critical metals.
What is shales depositional environment?
Depositional Environment. Flood Plain, Lake (away from shore), Mid-continental Shelf, Delta, Tidal Flat, Lagoon, or Deep Marine. Type. Sedimentary Rock.
What type of deposition does shale indicate?
Limestone forms in a deep marine environment from precipitation of calcium carbonate. Shale is made of fine clay particles, and therefore indicates deposition in relatively still water.
How are black shales formed?
Depositional processes involve a range of relationships among such factors as organic productivity, clastic sedimentation rate, and the intensity of oxidation by which organic matter is destroyed. If enough organic material is present to exhaust the oxygen in the environment, black shale results.
What is the most likely interpretation of a black colored shale?
Dark gray to black colors mean anoxic conditions, which may mean deep water, but could also be a swamp environment. The conclusion is, environmental interpretations can only be made in relation to the other rocks deposited with the shale. The dark gray of this specimen indicates a low oxygen environment.
What do black shales indicate?
Fine laminae in black shale indicate a lack of bottom-dwelling organisms, suggesting that the seafloor was covered by O2-deficient water.
What is black shale?
Black shale is a dark-colored mudrock containing organic matter that may have generated hydrocarbons in the subsurface or that may yield hydrocarbons by pyrolysis. Many black shale units are enriched in metals severalfold above expected amounts in ordinary shale.
How is black shale formed?
They typically form in environments where muds, silts, and other sediments were deposited by gentle transporting currents and became compacted, as, for example, the deep-ocean floor, basins of shallow seas, river floodplains, and playas.
What is black shale used for?
Black and gray shale are common, but the rock can occur in any color. Shale is commercially important. It is used to make brick, pottery, tile, and Portland cement. Natural gas and petroleum may be extracted from oil shale.
Where are black shales found?
Most black shales are found in marine sediments (Potter et al., 1980), but they can also form prominent deposits in lacustrine successions (Bohacs et al., 2000). Their black color is due to two constituents: (1) the contained organic matter, and (2) finely disseminated pyrite.
What causes black shale?
Black shales sediments in common are dark gray to black in color and are characterized by microlaminations, which may vary from distinct to blurred. The lamination is caused by quiet depositional conditions and the scarcity or lack of bioturbation.