Unformatted text preview: es an air‐filled cave, a discharge of carbon dioxide may alter the water's ability to hold these minerals in solution, causing its solutes to precipitate. Over time, which may span tens of thousands of years, the accumulation of these precipitates may form speleothems. 15 Geology & Geophysics in Oil Exploration Mahmoud Sroor Lake Cave Geology & Geophysics in Oil Exploration 2‐Transitional deposits A‐Lagoons: A lagoon is a body of comparatively shallow salt or brackish water separated from the deeper sea by a shallow or exposed barrier beach or coral reef. The water salinity ranges from fresh water to water with salinity greater than that if sea. In stagnant lagoons, Activity of bacteria loads to form H2S which causes precipitation of Black Iron Sulphides In lagoons with extensive evaporation, Salinity may become too great & form Salt & Gypsum B‐Deltas: A delta is a landform that is created at the mouth of a river where that river flows into an ocean, sea, estuary, lake. . Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river. Over long periods of time, this deposition builds the characteristic geographic pattern of a river delta. Delta is divided to Delta front which include Sand Bars at the mouth of distributy & Delta plain which include channels, bays & flood plains Types of Deltas: • River‐dominated Deltas: In this case, the river is stronger than Sea waves. When a single channel is occupied for a long period of time, its deposits extend the channel far offshore, and cause the delta to resemble a bird's foot (ex. Mississippi River Delta) • Wave‐dominated Deltas: In this case, the sea waves are stronger than river. Wave erosion controls the shape of the delta (ex. Nile Delta) • Tide‐dominated Deltas: In this case, Erosion is also an important control in tide dominated deltas. New distributaries are formed during times when there's a lot of water around ‐ such as floods or storm surges (ex. Ganges...
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This note was uploaded on 01/05/2011 for the course GEOL 1 taught by Professor Jenniferalford during the Spring '10 term at Indian Institute of Technology, Roorkee.
- Spring '10