How Do You Reverse Projections to Interpret Geological Maps?

[rahuldg11]

I have real problems in interpreting geological maps. Can somebody help me ??

 

[Evo]

I have real problems in interpreting geological maps. Can somebody help me ??

You need to first explain what you are having a problem with. Can you give examples?

 

[rahuldg11]

Can you tell me the steps to interpret a map? i can more or less understand the topography, then identify the litho units. The main problem i have is with the discontinuity surfaces. Even if i am able to identify them, i cannot get the details of the surfaces.

 

[matthyaouw]

I always found it helpful to draw a cross section of an area that looks unclear. Use the topographic and dip information given, see if that helps.

 

[rahuldg11]

yes, that is not a bad thing to do. But how do u understand the discontinuities from the map itself, just by looking at the dip directions and relative dip amounts ?

 

[matthyaouw]

honestly I'm not quite sure what it is you don't understand so I can't really help.

 

[Ophiolite]

Remember that a map is a section. It is an intersection of the ground with the subsurface geology. A syncline with an axis dipping at 20 deg projects an outline of itself onto the 3-D - ground surface and hence onto the 2D map surface. You just have to reverse those projections in your mind in order to envisage the 3-D structure.

Unconformities are easily recognisable, since one lithology will cut across several others. Unless we are dealing with thrust faults, or igneous intrusions then the truncated lithologies are the older ones.

It's really just a mater of putting together common sense ideas like that and practising the art of interpretation.

Apart from that, I'm with Matt - I don't understand what it is you don't understand.