[Music] thank you hello everyone we had three consecutive lectures on reviewing the theory and this lecture will go directly to the field and will roam around katrila particularly in harindungri and some other places also in fairy god to understand and see different kinds of superposition of folds in this lecture we will particularly focus on the form surface and these form surfaces could be S 0 S 1 or S two at the same time we will also see because of the folding of these firm surfaces will generate multiple sets of foliations or in other words axial planar cleavages we will try to interpret their Mutual relationships will measure will show them how they are disposed in the stereo Nets and so on let us get started so now we will focus on the folding that has happened in this exposure and the folds are as you can see in this area is expressed by a lot of asymmetric Folds so again these are the traces of s 0 on this surface we are looking at a vertical surface and you can see that if I mark this one focus on this one you see beautiful asymmetric Folds going on like that you can say asymmetric folds also here in this layer like this and if you look carefully the fold axis of this goes in in this way ok here for example here so if you have a fold asymmetric fold which in this case is somehow like that like this and this is your fold axis then axial planar cleavage of this particular fold should be like this so again let us repeat our nomenclatures these are the traces of the S zero that means the primary bedding surface and this if this S 0 gets folded then that fold IS F 1. so we are looking at f one folds in this form here and here the fold axis of f one is like that here here and here in this form so therefore S one should form in this way and if we come here in this surface we actually can see the exposed S one and interestingly both S 0 and S1 they are almost parallel or sub parallel or at a very low angle to each other and that tells us first interpretation from this is that we are at the limb of a major fold and all these asymmetric folds also support this interpretation now if you closely look on the S1 surfaces which are these surface we see that s one surfaces are also granulated and these are the granulations you can see here so if S one surface is granulated that means we are developing f 2 over S one so S one is a continuous foliation or continuous cleavage here and F two is developing over S one or has developed over S one as you can see in all places here here and here they are going like that so they have to be spaced because these are granulated so s two then Falls in a very similar fashion so in this surface we cannot see s two which should develop because of f two we will see on a horizontal section s two and identify whether the S two is parallel or perpendicular to F1 but meanwhile you can think that what it should be what we further see here that we have identified f 1 is this way this is the f one fold axis and granulations are also in this manner and therefore we can conclude that this one was our f one and this one is f two and we clearly see that they are parallel to each other so we again conclude from this exposure that f one and f 2 are coaxial to prove it further we have measured the data from all these places and we also got some direct fold access measurement of f one and we plotted them on the stereo net and then we will see that how we can actually tell what is the deformation features or related geometries ah in this area what we are seeing in this exposure ah this exposure is between the first quartzite band the thickest quartzite band and the next one the medium thick quartzite band we are on this alternate quads and Mica cyst layers and what we have just seen in this exposure that here f 1 and F two are coaxial we have seen in this place that f one Folds are essentially asymmetric so if we see them they are going like that and if I they are not so I am trying to make them full axis vertical they are like this so these are the f one Folds and so on now if F two as we have seen because of this we are forming the axial planar cleavage of the f one fold almost sub parallel to S 0 which is this one and then S one is coming like that now if S one we have seen that s one showed some granulations in the second stage of deformation and therefore this fold of s two giving rise what is called f two and f one and F two as you can see there parallel to each other and therefore coaxial now what is happening with the S 0 as a result of F2 so essentially S 0 is also getting folded so you can think of that if s 0 is getting folded further by F two which has already been folded by f one then the hinge sections particularly will get modified and they probably will take a shape like that you may also expect some minor folds here or you may not but the hinge sections could be greatly modified and if we now try to see this in third dimension we can figure out that these things where f one and we have generated one more curvature here this one these are giving rise F two so therefore this is a fold superposition of type 3 this we know from our Theory lecture I mean type 3 as classified by Professor Ramsay and the typical outcrop pattern of type 3 is hook now in this area what we are seeing ah the fold axis we have just seen and measured they are not vertical they are at an angle and therefore the appearance of hook pattern is little apparent and you may have to stress your imagination to understand that because we do not have a proper section to see this so what you you just see this image remember this image particularly say for example this section and try to stretch your imagination to fit this part that we are looking at so this is s 0 and here you can see that this is folded giving rise fold axis f one which is going in this in this direction and f one has formed which is at very very low angle so you can see the trusses of f One S one ah are going like this and S two F two is here you can see the granulation of s one falling like this so therefore if one and F two so this was f 1 and this is f 2 they are parallel to each other and coaxial and this we have already demonstrated and understood but as a result we can see because of f one and F two s 0 is giving like a hook shape and because if one here is not perpendicular so we can actually visualize the fold in this manner so it was like this and you can see if you just stretch it in this form it appears this way so it is coming and then getting around and then coming back this one and this one and this one this this and this are f one and this one is f two I repeat this is not a very ideal section to look at the superposition outcrop for for example in this case we expect hook but this is the closest I can demonstrate you from this exposure we hope to see some more features and show you later so here also in a very little exposure here and we will examine the over printing relationships as this particular exposure ah displays a number of features I hope your eyes are more or less set right now to understand at least ah through the visual ways we see the trends of s 0 I am marking this particular place here we can also check it here so s 0 as you can see here it is folded and this I am marking it here is defining the f one S 0 got folded defining the f one and all these surfaces that you see this stresses you see and these surfaces here these are produced because of f one and therefore all these are S1 surfaces on this S one surface we see one set of granulation this way we can see that this way and another set of credulation it is prominently developed here this way you can see this so this particular surface S one has two sets of Folds one this one and another this one both are given by granulations and therefore formation of s two and S three because of this fold and this fold should be spaced whereas s 1 is continuous now you see we have identified that f one and this particular fold are of same orientation and their coaxial so this is f two and regionally we will see when we will do the map that this orientation has changed at some places but this orientation remained constant so which one is first this one or that one to understand that we have mapped the entire region and found that both this orientation and its axial planar cleavage S2 that is this orientation have changed significantly in this region but this one fold axis and its axial planar cleavage S3 they remain constant throughout this region so that helped us to conclude and we have already said it when we saw only these two that f one and F two therefore I Define this as F two they are coaxial and then F three which remain constant throughout the area is the third fold and therefore I call it f three so in this small region you see we see S 0 which is folded folding of S zero gave you s one which is this surface or this surface this S one surface got folded Twice first in this manner by a granulation giving rise s two spaced foliation and then the entire packet got further folded in a crossed manner giving rise F three in this direction Again manifested by granulation and therefore S three is also spaced here so we are reiterating the same ah statement that if you form folding on S 0 the foliation should be continuous foliation and all successive Generations at least in low grade metamorphic rocks should always be space foliation and in this region particularly we have measured all these orientations the general trend of s 0 wherever we found deep and strike S one we measure depend strike s two wherever we found we measure depend strike S three wherever we saw we measured deep and strike and at the same time we also measure the fold axis of f one F two and F three and we plotted them regionally and we will show you later that how they are related in this entire region not only in harinder Moody Village but also in the entire ghatsila region particularly we will compare the fairy gut and what we see here in the village so here we are also in a very interesting exposure we have seen in this exposure that all other features that we we just have seen in another exposure exactly on the Eastern side of the youngest and thickest quartzite band in this harindungi region ah there we have established the relationship between S 0 S 1 and S2 and here we also see the trusses of the bedding planes so these are S 0 this particular surface that we are looking at is actually S one surface as you can see here as well s 1 surface is little curved because of the cleavage refraction but that gave us an opportunity to look at several other features so if this is s one surface and these are the trusses of s 0 falling on the S 1 surface this if you measure the trend and plunge of this lineation on the surface that gives you f one now you also see this surface and this surface is granulated and as we have identified these granulation axis as the axis of f two now this F two traces of f two are also on S1 so S2 here is also going like that as we have seen on this exposure so therefore the traces of S2 on S 1 is also like this we have seen if one is like that and we are seeing that traces of S2 on S 1 are also like this so it clearly tells us that here f 1 and if two are parallel to each other and therefore we can conclude that in this area f one and f 2 are coaxial and this we have established from our data and other things even we have seen this in fairy heart another most important feature in this surface is other than the trusses of s 0 and f 2 on this S1 surface we see another interesting granulation which have developed on the surface and you can see they are going like that in the curved surface and their General orientation here access orientation is like that so what we see here these are probably defining another fold and you are right if you guessed so these are the third generation of fold that have developed in this area and these are the trusses of the fold axis of the third generation of fold or F3 and which is here at least in this case the cross fold so if I try to summarize here what we have observed this is one surface on this S1 surface we see the trusses of S 0 and S two defining the f one and F two fold access and we have taken their measurement and we have understood that they are coaxial S three is falling like that and they are appearing as granulations on this surface and therefore if we take this measurement that will give you the orientation of f three so in this very small exposure we have identified a number of features in addition to all these we also understood a very important mechanism that S one which is the first foliation that is axial planar cleavage of the major fold here is a continuous one all other to foliations S two and S three both of them are spaced cleavage and this is how it has to be so if you see a continuous foliation in the field 99.9 percent cases these foliations continuous foliations are generally S one and if S one further deforms and produces later generation of Folds the foliations due to these later generation of folds are essentially best foliation so here we arrive at the hinge zone of this third quartzite band that I was talking about in the previous section what we see here you can follow these are the traces of the bedding planes and then it turns here and then it goes here it takes a further turn and goes in this direction So eventually it generates a fold here and if I look from this side you see this is the fold you are looking at this is a fold axis and when it turns back in this side you get another fold and this is the fold axis so again if I look from this side you see this is the antiform and in the same train of the fold you see this is the same form and this has happened here and this is almost a tight fold as you can see will measure this angle and show it to you what is most important if we consider it and compare it with respect to fairy heart is the fold axis you see the fold axis is almost vertical the plunge of the fold axis here we have measured its close to 75 degrees and this tight fold here makes the regional S1 you see the traces of the S one here like that because this in form this antiform and the sin form is almost symmetrical here the fold axis is going like this and these are the traces of S1 on this surface and making the fold very much symmetric in fairy heart we found the fold axis was plunging around 15 degrees with the same S 0 here we find the fold axis is plunging extremely at high angle it it basically is making a recline fold so that gives us a clear idea the fact that here in this location we see the fold access is almost vertical or is giving kind of a reclined fold and in fairy heart we saw that the fold access where pretty gentle close to 12 to 15 degrees tells us that or helps us in concluding the fact that regionally the fold is not cylindrical because the flange of the fold axis is heading regionally and if the fold is not cylindrical that means the fold is non-cylindrical there must be superposed deformation or superposition of folding and this we have seen in many other places where we are looking at different uh full superpositions in small scale we have seen granulation cleavages we have seen ah granulations forming F2 F3 and so on the third quartzite band from this place also drifted or shifted because of this folding from its original trained and then it follows actually the luxury Anala which is also following the trend of this quartzite band and flowing along its boundary so it's coming from my back and then going this way taking a strong turn and now going towards north side axial planar cleavage and s0 that means bedding plane so S1 and S 0 they interact in many different ways when they appear before us for example what we see here we see the trusses of the bedding planes going like this and you can figure out that it is giving a very gentle open fold and from your side of view it gives an antiform now you see the axial planar cleavage the trusses of axial panel cleavage perfectly making it a symmetric fold what is important to note here this is a quads Rich layer therefore stiffer these has more Mica therefore less stiffer or softer and because it has more Mica the concentration of axial planar cleavages here you see are more and here you hardly see actual planet cleavages or even if you see they are not as concentrated as here so can you say that these are space cleavage here and continuous cleavage here the answer is no because they are not here that does not mean that they are not present because we cannot see here does not mean that they are not present here they are strongly developed but here not but if you make a thin section and try to figure out the orientation of the quads grains you will figure out the presence of axial peanut cleavage in the thin section so this is a beautiful place where we see that axial planar cleavages are perfectly developed as we see in textbook images so here we are looking at a small fold as you can see the fold is going like this and this way so because of this fold the rock here this rock is particularly a quartzite so it is a quartz rock and what you see outside this rock is micassist and you can clearly see the trusses of the axial planar foliation of this particular fold so this is s 0 that is folded and then because of that you have actual printer foliation going like that as your S1 what is interesting to see here if you follow this foliation from here then you see a part of it this is the hinge and that is the hinge point which are coming from this side is taking a curve turning and running this way and which are coming from this side taking a curve and running it this way giving kind of a flower like structure so in this particular scene form that you are looking at they are diverging away towards the hinge so this is an example of cleavage Fanning thank you for your attention with this we finish the lecture number 13. in the next lecture we will take you to a beautiful place called where we will see super post folding in a single outcrop stay tuned I will see you in the next lecture thank you [Music] thank you foreign [Music] [Music]