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Unformatted text preview: her) and unlayered. The glacier will often carry large boulders, sometimes as large as cars or small homes, as they advance. When the glacier retreats, these large boulders are left behind, often dropped among much smaller glacial till. These large boulders are called erratics. Since erratics are rarely derived from the local bedrock, identifying the source rock for the erratic can tell you about the direction the glacier travel from. Cold Glaciers: are dry‐based & have much rock debris Temp. Glaciers: are wet‐based & have less sediments, but more powerfully erosive 14 Geology & Geophysics in Oil Exploration Mahmoud Sroor Desert from Glacier Geology & Geophysics in Oil Exploration B‐Fluvial deposits: • Alluvial Fan An alluvial fan is a fan‐shaped deposit formed where a fast flowing stream flattens, slows, and spreads typically at the exit of a canyon onto a flatter plain Fan surface is usually desiccated by network of channels & has 3 main zones: 1‐Proximal: coarse grains 2‐Intermediate grains: Medium grains 3‐ Dital: fine grains • River & Stream It comprises the motion of sediment and erosion of or deposition on the river bed. Types of river deposition: 1‐Meandering: with high sinuosity streams make a distinct channel 2‐Braided: with low sinuosity are frequent & braided • Piedmonts Sediment Braided Meandering Accumulate in the basis of mountains as a result of soil creep, Rain Wash, Rock streams & Mud flow • Valley flat Sediments Differ from Piedmonts is that they show better sorting, stratification & more organic matters C‐Lake deposits (Lacoustrine): Lakes are well‐suited to the development of deltas. Deltas are built up by sediment‐laden streams, & they drop their load of sediment as they loose velocity. • Bottom Set Beds: Fine sediment is carried by feeble current to basin bottom • Top set Beds: as the delta builds, gradually filling the basin over its deposits D‐Cave deposits (Spelal): Water seeping through cracks in a cave's surrounding bedrock may dissolve certain compounds, usually calcite and aragonite, or gypsum. When the solution reach...
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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