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ASBOG FG EXAM PREP 2024/2025 with 100% correct answers
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ASBOG FG EXAM PREP 2024/2025 with 100% correct answers
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ASBOG FG EXAM PREP 2024/2025 with 100% correct answersA plunging anticline will show closure in an outcrop pattern. In which direction does the
anticline plunge with respect to the closure? - ✔✔A plunging anticline is plunging in ht direction
of closure.
What can be inferred from a borehole log indicating a repetition of beds? - ✔✔A repetition of
beds in cross section indicates fault movement in which the hanging wall has moved up with
respect to the foot wall (reserve faulting).
Are slickensides indicative of faulting? - ✔✔The presence of slickensides may indicate faulting
but this feature also results from non-fault related movement in clays, such as shrinking and
swelling.
What type of geologic feature might you expect from a mapped outcrop pattern that consists of a
series of series of concentric circular shapes? - ✔✔1. Horizontal beds mapped on a rounded
hilltop. 2. Horizontal beds mapped in an enclosed basin. 3. An intrusion with bands of contact
metamorphism of varying degrees.
Chert is found commonly in the Coast Ranges Province of California. What is its depositional
environment and how is it formed? - ✔✔Chert originates in shallow sea water. Some cherts
result from the enrichment of silica in the sea water from volcanic rocks. They also may form by
the accumulation of silicious skeletons of silica secreting organisms.
According to the Unified Soil Classification System, gravels have a grain size greater than what
diameter? - ✔✔gravel: >No. 4 sieve or 4.76 mm
When observing cross-bedded sandstones, how do you know where the top of the beds are? -
✔✔Unit is right side up when cross-bedding is concave up.
What type of geologic units would constitute a "key bed"? - ✔✔Key beds are layers that have
been deposited simultaneously over large areas. Volcanic ash, beds rich in fish scales, oysters or
corals.
,What type of fault might be represented by juxtaposition in map view of noncontiguous
sedimentary formations. - ✔✔Sedimentary formations that do not occur next to each other may
be moved laterally by strike slip faults.
Name and define the 4 various different types of unconformities? - ✔✔Angular unconformity:
strata below the unconformity are cut off and overlain at an angle by the beds above.
Nonconformity: sedimentary deposits rest upon older igneous or metamorphic rocks.
Disconformity: beds above and below unconformity are parallel, but unconformity not parallel to
bedding.
Paraconformity: unconformity is parallel to the strata above and below it.
How can the "rules of V's" be used on a map with no topography? - ✔✔In using the rule of V's
to interpret direction of dip on a map with no topography you must first look at the V's
downstream, since V downstream is always dip downstream. When interpreting V's upstream
you must observe the quality of the V. Shallow V's mean dip upstream and ac the V's get deeper
it passes from horizontal bedding to a dip downstream less than the valley gradient.
Define foot wall and hanging wall - ✔✔Foot wall - block that underlies a non-vertical fault.
Hanging wall - block that overlies a non-vertical fault
What is a regressive sequence? - ✔✔Regression is the withdrawal of the sea from land. A
regression is represented by limestone overlain by shale overlain by sandstone.
What is the order of deposition of evaporites? - ✔✔Order of Deposition
calcium carbonate - calcite
calcium sulfate - gypsum or anhydrite
sodium chloride - halite
magnesium sulfates and chlorates
sodium bromide and potassium chloride
, What are the processes of diagenesis? - ✔✔Diagenetic processes include: compaction,
cementation, reworking, authigenesis, replacement by secondary minerals, crystallization of
secondary minerals, leaching, hydration, bacterial action, or formation of concretions.
Give three examples of magmatic segregation deposits - ✔✔1. Layered magic intrusions
(chromite)
2. Kimberlite pipes (diamonds)
3. Ophiolites (asbestos)
What is the importance of knowing water saturation in a oil reservoir? - ✔✔Below 60% of oil
saturation, the reservoir will produce mostly water.
Define aquifer - ✔✔A geologic unit that is saturated and sufficiently permeable to transmit
significant economic quantities of water to wells and springs
A poorly-sorted (or well-graded) sediment or sedimentary rock contains how many grain sizes? -
✔✔Poorly-sorted (well graded) sediment has a wide range of grain sizes present.
A plunging syncline may show closure in an outcrop pattern. In which direction does the
syncline plunge with respect to the closure? - ✔✔A plunging syncline is plunging away from the
closure.
According to the Unified Soil Classification System, a clay or silt would contain particles less
than what diameter? - ✔✔clay or silt - <No. 200 sieve or 0.074 mm
Contact metamorphism is associated with the intrusion of an igneous mass. What causes the
metamorphic changes in this type of metamorphism? - ✔✔Metamorphic changes are caused
principally by heat, but also by magma composition and deformation related to the intrusion.
Pressures are relatively low (<3000 bars) while temperatures range from 200 c to 1000 c.
How is pyrite formed? - ✔✔Pyrite is formed by the indirect action of bacteria. The bacteria
chemically change sulfur from an oxidized state (sulfate - SO4) to a reduced state (sulfide - S).
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