TOPIC :INCLINED BEDDING(FOLD) (LAB 2a) 1.0 OBJECTIVE To plot ground profile and rock formations from geological map – inclined beddings
2.0 LEARNING OUTCOMES a) Students should able to plot subsurface profile. b) Students should able to understand the geological structure in subsurface profile. c) Students should able to understand a history of the geological area.
3.0 THEORY A geological map is one, which shows in the first place, the occurrence and distribution of the rocks at the surface of the ground. Conventional sign may show certain facts of observation about them. The geological map allows the geological structure of the country to be inferred. Beds of rocks are bounded by bedding surfaces, which may be horizontal, tilted or bent in any form or direction. A series of beds which have been laid down regularly one on the other, and which may be treated as a whole, form a conformable series. It follows that the lower beds are the older. In such a series of bedding surfaces are parallel. Each bedding surface is usually common to two beds of rock, being the top of one and the bottom of the one next above. In the simplest case, these surfaces are planes: bedding planes.
4.0 EQUIPMENT AND MATERIALS 1. Geological Map ( Map 7 – Appendix B ) 2. Graph paper/drawing paper - A4 size 3. Ruler
5.0 PROCEDURE 1.Plot the cross-section with the horizontal and vertical scales accordingly to the scale of the geological map on a piece of graph paper or blank sheet. Refer Figure 1.1. The vertical scale is normally exaggerated to improve visibility of the profile. 2.Draw a line to join the line of cross-section on the map, says A - B. 3.Using a blank piece of paper, mark the points of intersection accordingly between the lines with the contours respective to its heights. 4.Transfer the points to the cross-section profile respective to the heights of the contours. 5.Join the points to form the profile of the ground elevation.
6.0 RESULT AND ANALYSIS By referring to Map 7, 1. Highlights the rock boundary to focus for determination of strike line. 2. Select two pints within the marked boundary of similar heights. 3.Draw the line between the two points to indicate the first strike line. Its value corresponding to two value of contour. 4. Select another point (of ascending @ descending contour value). 5. Draw a line that touches the parallel the select point to the first strike line. 6 Measure the distance (say, d1) cut at right angles to the parallel lines. 7.Determine the angle of dip of the fold.
BOUNDARY
DIRECTION
DIP ANGLE
CB
90°
32°
BA
90°
29°
AB
270°
29°
BC
270°
32°
CB
90°
32°
7.0 QUESTION AND DISCUSSION Question and answers 1. Explain types of fold (with the aid of diagram) and discuss how this structure occurred. A geological fold occurs when one or a stack of originally flat and planar surfaces, such as sedimentary strata, are bent or curved as a result of permanent deformation. Synsedimentary folds are those due to slumping of sedimentary material before it is lithified. Folds in rocks vary in size from microscopic crinkles to mountain-sized folds. They occur singly as isolated folds and in extensive fold trains of different sizes, on a variety of scales.Folds form under varied conditions of stress, hydrostatic pressure, pore pressure, and temperature gradient, as evidenced by their presence in soft sediments, the full spectrum of metamorphic rocks, and even as primary flow structures in some igneous rocks. A set of folds distributed on a regional scale constitutes a fold belt, a common feature of orogenic zones. Folds are commonly formed by shortening of existing layers, but may also be formed as a result of displacement on a non-planar fault (fault bend fold), at the tip of a propagating fault (fault propagation fold), by differential compaction or due to the effects of a high-level igneous intrusion e.g. above a laccolith.
8.0 CONCLUSION When weathering and erosion expose part of a rock layer or formation, an outcrop appears. An outcrop is the exposed rock, so named because the exposed rock "crops out." Outcrops provide opportunities for field geologists to sample the local geology—photograph it, hold, touch, climb, hammer, map, sniff, lick, chew, and carry it home. Classes often visit outcrops to see illustrations of the principles of geology that were introduced in lecture. You often can see geologists or students identifying rocks in roadcuts, outcrops along the road where highway construction exposed the rocks.Mountainous regions, where any loosened Earth material swiftly washes away, contain some of the best outcrops because a greater percentage of the rock formation lies exposed. Rocks crop out especially well across steep slopes, above the tree line (elevation above which trees cannot grow), and on land scraped free of soil by bulldozer-like glaciers. Sediment collects and plants grow in flatter areas, obscuring the rocks. In some areas soil and sediment may completely cover all the underlying rock, such as in the southeastern United States. However, in the desert southwest, the opposite is often the case. Outcrops cut the cost of mapping for geologists. The greater expense of geologic mapping in an outcrop-free area results from high-priced drilling to sample the rocks hidden below the surface. Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficial deposits are covered by a mantle of soil and vegetation and cannot be seen or examined closely. However, in places where the overlying cover is removed through erosion or tectonic uplift, the rock may be exposed, or crop out. Such exposure will happen most frequently in areas where erosion is rapid and exceeds the weathering rate such as on steep hillsides, mountain ridges and tops, river banks, and tectonically active areas. In Finland, glacial erosion during the last glacial maximum (ca. 11000 BC), followed by scouring by sea waves, followed by isostatic uplift has produced a large number of smooth coastal and littoral outcrops. Outcrops allow direct observation and sampling of the bedrock in situ for geologic analysis and creating geologic maps. In situ measurements are critical for proper analysis of geological history and outcrops are therefore extremely important for understanding the geologic time scale of earth history. Some of the types of information that cannot be obtained except from bedrock outcrops or by precise drilling and coring operations, are structural geology features orientations (e.g. bedding planes, fold axes, foliation), depositional features orientations (e.g. paleocurrent directions, grading, facies changes), paleomagnetic orientations. Outcrops are also very important for understanding fossil assemblages, paleo-environment, and evolution as they provide a record of relative changes within geologic strata.
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TOPIC : FAULT BEDDING (LAB 2b) 1.0 OBJECTIVE To plot ground profile and rock formations from geological map – faulted bedding 2.0 LEARNING OUTCOMES a) Students should able to plot subsurface profile. b) Students should able to understand the geological structure in subsurface profile. c) Students should able to understand a history of the geological area. 3.0 THEORY A geological map is one, which shows in the first place, the occurrence and distribution of the rocks at the surface of the ground. Conventional sign may show certain facts of observation about them. The geological map allows the geological structure of the country to be inferred.Beds of rocks are bounded by bedding surfaces, which may be horizontal, tilted or bent in any form or direction.A series of beds which have been laid down regularly one on the other, and which may be treated as a whole,form a conformable series. It follows that the lower beds are the older. In such a series of bedding surfaces areparallel. Each bedding surface is usually common to two beds of rock, being the top of one and the bottom of the one next above. In the simplest case, these surfaces are planes: bedding planes
4.0 EQUIMENT AND MATERIALS 1. Geological Map ( Map 14 – Appendix C ) 2. Graph paper/drawing paper - A4 size 3. Ruler 4. Pencils 5. Colour pencils (optional)
5.0 PROCEDURE 1 Plot the cross-section with the horizontal and vertical scales accordingly to the scale of the geological map on a piece of graph paper or blank sheet. 2.Draw a line to join the line of cross-section on the map, says A - B. 3.Using a blank piece of paper, mark the points of intersection accordingly between the lines with the contours respective to its heights. 4.Transfer the points to the cross-section profile respective to the heights of the contours. 5.Join the points to form the profile of the ground elevation.
6.0 RESULT AND ANALYSIS By referring to Map 14, 1.Determine the dip and strike of the coal seams. 2. Determine the thickness of sandstone outcrop. 3.Determine the dip and strike of the fault. 4.Plot the rock outcrop and fault on the cross-section profile.
BOUNDARY
DIRECTION
DIP ANGLE
BDC
190°
22°
BDFC
190°
63°
190°
21°
190°
22°
BDC
BA
5.0 QUESTION AND DISCUSSION Explain types of fault (with the aid of diagram) and discuss how this structure occur? Strike-slip faults The fault surface is usually near vertical and the footwall moves either left or right or laterally with very little vertical motion. Strike-slip faults with left-lateral motion are also known as sinistral faults. Those with right-lateral motion are also known as dextral faults.Each is defined by the direction of movement of the ground on the opposite side of the fault from an observer.A special class of strike-slip faults is the transform fault, where such faults form a plate boundary. These are found related to offsets in spreading centers, such as mid-ocean ridges, and less commonly within continental lithosphere, such as the Dead Sea Transform in the Middle East, or the Alpine Fault, New Zealand. Transform faults are also referred to as conservative plate boundaries, as lithosphere is neither created nor destroyed. Dip-slip faults A fault which has a component of dip-slip and a component of strike-slip is termed an oblique-slip fault. Nearly all faults will have some component of both dip-slip and strike-slip, so defining a fault as oblique requires both dip and strike components to be measurable and significant. Some oblique faults occur within transtensional and transpressional regimes, others occur where the direction of extension or shortening changes during the deformation but the earlier formed faults remain active.The hade angle is defined as the complement of the dip angle; it is the angle between the fault plane and a vertical plane that strikes parallel to the fault.
6.0 CONCLUSION
Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficial deposits are covered by a mantle of soil and vegetation and cannot be seen or examined closely. However, in places where the overlying cover is removed through erosion or tectonic uplift, the rock may be exposed, or crop out. Such exposure will happen most frequently in areas where erosion is rapid and exceeds the weathering rate such as on steep hillsides, mountain ridges and tops, river banks, and tectonically active areas. In Finland, glacial erosion during the last glacial maximum (ca. 11000 BC), followed by scouring by sea waves, followed by isostatic uplift has produced a large number of smooth coastal and littoral outcrops.Bedrock and superficial deposits may also be exposed at the Earth's surface due to human excavations such as quarrying and building of transport routes. Outcrops allow direct observation and sampling of the bedrock in situ for geologic analysis and creating geologic maps. In situ measurements are critical for proper analysis of geological history and outcrops are therefore extremely important for understanding the geologic time scale of earth history. Some of the types of information that cannot be obtained except from bedrock outcrops or by precise drilling and coring operations, are structural geology features orientations (e.g. bedding planes, fold axes, foliation), depositional features orientations (e.g. paleo-current directions, grading, facies changes), paleomagnetic orientations. Outcrops are also very important for understanding fossil assemblages, paleoenvironment, and evolution as they provide a record of relative changes within geologic strata.Accurate description, mapping, and sampling for laboratory analysis of outcrops made possible all of the geologic sciences and the development of fundamental geologic laws such as the law of superposition, the principle of original horizontality, principle of lateral continuity, and the principle of faunal succession.
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