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Thread: strutural geology

  1. #1 strutural geology 
    ilg
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    hi ! I have some questions on structural geology, which may appear not difficult for you, but I seem always mix up or confused with them. Thanks

    1.is there any term called PLUME AXIS (it should be related to joints). I tried to google it but I cannot find something which is quite related. Is this related to propagation direction of hackles??

    2.For joint plane and foliation plane, can I say both of them are interchangeable or even the same ?
    3. what is slikolite ? again, I google it but I can only found some thai-related website.
    4. Is a kink band similar to a kink fold ?
    5. why do joints not likely to be found in tuffaceous rock and very fine grained sedimentary rocks ?


    Last edited by ilg; May 2nd, 2012 at 10:41 AM.
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  3. #2  
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    Warning: both sides of the Atlantic were much closer to each other when I obtained my degree.

    1. The only context in which I have heard of a plume axis is in relation to mantle plumes.

    2. Joint planes are the planes along which there are fractures, but where there is little or no relative movement between the rock on either side of the plane. A joint plane is a physically real thing.
    A foliation plane is an imaginary plane passing through a zone of foliation i.e. a portion of the rock where minerals are all, or mostly aligned in the same direction.

    3. If you have access to The Journal of Structural Geology locate this paper "Brittle microtectonics: principles and practice" in Volume 7, Issues 3–4, 1985, Pages 437–457. There is reference to slikolites there. via Google Scholar I was able to extract this portion of the paper: "... Jaroszewski (1972) and Mattauer (1973) have emphasized that there is a continuum of structures from stylolites that bear columns normal to a seam, through those on which the columns are oblique to the seam (slikolites) to those within which the lineation is subparallel to ... "

    4. I'm very unsure on this one, but I think the kink band may be that portion of the kink fold where there is an abrupt angle change of the beddings planes, whereas the fold relates to the whole structure.

    5. I believe the answer is in the question.


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  4. #3  
    ilg
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    thanks...i have other questions..

    1. do splays faults means the secondary faults made along the main fault ? Is there any relationship with transpression and restraining bends ? Can I say restraining bends are formed in transpression area ???

    2. I understand folds can be generated by thrust fault, but i doubt how can a strike skip fault also contribute to folding !?

    3. I am wondering is a palm tree structure formed in transpression while a tulip is not (it should be in extensional area right?) . Still, I don't understand why the shape of tulip/palm tree is obtained. Is it related other secondary faults formed along the main fault ?

    4. Assuming there are dikes around the shear zone, some are near while some are not. Does the discontinousity/continousity of deformation (of dike) NOT depending on the distance from the shear zone but depending on the oritentation of the dike ?

    5. Is riedal shears restricted to dextral movement ? How about synthetic and antithetic shears? And are all these secondary faults produced?

    6. can i say plumes = hackles?

    7. concerning the patterns of joints..will a particular type of rocks be more likely to have a certain type of joints pattern? esp, the Y shaped/T shaped

    Thanks
    Last edited by ilg; May 5th, 2012 at 03:40 AM.
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  5. #4  
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    Quote Originally Posted by ilg View Post
    2.For joint plane and foliation plane, can I say both of them are interchangeable or even the same ?
    Joints are typically too spaced to be considered folia of any kind.
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  6. #5  
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    Quote Originally Posted by ilg View Post
    1. do splays faults means the secondary faults made along the main fault ? Is there any relationship with transpression and restraining bends ? Can I say restraining bends are formed in transpression area ???


    A splay can either be a secondary structure, or it can simply be a leg of the main structure. Faults and shear zones are rarely just one plane, so it depends on the context.

    Transpression simply refers to the relative movement: compressional (reverse) movement with a component of transform movement. Its possible for extension to occur in these regions at a local level.



    2. I understand folds can be generated by thrust fault, but i doubt how can a strike skip fault also contribute to folding !?
    Drag folds where rock or strata are deformed along the plane of movement.


    5. Is riedal shears restricted to dextral movement ? How about synthetic and antithetic shears? And are all these secondary faults produced?
    Riedels are not restricted to dextral movement.
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  7. #6  
    ilg
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    I would also like to ask about the decollement and imbricated splays. I don't understand how a trailing imbricate fans are made. I think the imbricate fans are made in the foreland not in the accretionary prism?? Then I think the fault which made by the compression on the foreland should be propagating into the foreland (i.e. forming the leading imbricate fans). I cannot think of what kind of process can lead to the formation of trailing imbricate( with splays within the foreland younging in the direaction of hinterland). Also I also cannot think of how to make the splays within the foreland propagate backwards towards the hinterland (the propagation direction of the younger splays are opposite to that of the oldest one)

    Also...is En echelon tension gash the same as en echelon vein ?

    and..concerning folds..
    it seems the reclined fold and inclined plunging fold are quite indistinguishable? I read some diagrams, but I still do not understand how a reclined fold is formed. Most definition of reclined fold found is 'axial surface is inclined with hinge plunges down the dip of axial surface. Some of the diagram look like a vertical fold with inclined axial plane(p.5 of
    http://instruct.uwo.ca/earth-sci/201a/LectureOnFold.pdf
    ). (if this is true, can a reclined fold look like a horizontal fold with inclined axial plane?)

    Last edited by ilg; May 6th, 2012 at 07:51 AM.
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