Unformatted text preview: used to determine locations with respect to a reference point For Example: in Egypt we have 3 zones each one has its reference point At the figure, the point location 150km North, 170 km east 3 Geology & Geophysics in Oil Exploration Mahmoud Sroor Geology & Geophysics in Oil Exploration Ch1: Sedimentary rocks Sedimentary rock is a type of rock that is formed by sedimentation of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles (detritus) to settle and accumulate or minerals to precipitate from a solution. Particles that form a sedimentary rock by accumulating are called sediment. Before being deposited, sediment was formed by weathering and erosion in a source area, andthen transported to the place of deposition by water, wind, mass movement or glaciers. The study of the sequence of sedimentary rock strata is the main source for scientific knowledge about the Earth's history, The scientific discipline that studies the properties and origin of sedimentary rocks is called sedimentology. Sedimentology is both part of geology and physical geography and overlaps partly with other disciplines in the Earth sciences, such as geomorphology, geochemistry or structural geology. Classification of sedimentary Minerals: • Detrital: A‐Residual detrital: are those of source rocks which survive from the process of weathering & mechanically transported & redeposit (Some of them stable like Quartz or unstable like Clay minerals) B‐Secondary detrital: are those generated by weathering process • Chemical Precipitates: Deposited from solutions by chemical & biochemical process Example: Aragonite, Calcite, Gypsum, Anhydrite & Opal Classification of Sedimentary Rocks: • Clastic or Mechanical Sediments: such as Conglomerate, Sandstone, Mudstone • Non Clastic Sediments: Chemical: Limestone, Chert, Gypsum, Rock salt Biological: Fossilferous Limestone Classification of clastic sediments based on Size of fragments: Boulder: >256mm Cobble: 64:256mm Pebble: 4:64mm Granule: 2:4mm Sand: 1/16:2mm Silt: 1/256:1/16mm Clay: <1/256mm 4 Geology & Geophysics in Oil Exploration Mahmoud Sroor Geology & Geophysics in Oil Exploration Textural elements of clastic Rocks: • Grain Size: ‐Coarse ‐Medium ‐Fine ‐Very fine • Grain Shape: • Sphericity: Ratio of surface area of grain to a sphere of...
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- Spring '10
- Geology, Volcano, Tephra, Volcanic Ash, Geology & Geophysics, Mahmoud Ahmed Sroor