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Sedimentary basins — Transcript

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0:05[Music]
0:16hello students I am partage of Liberty
0:20from Department of Geology University of
0:22Delhi today our topic of discussion
0:25it is the sedimentary basins the
0:27different mechanism that basically
0:29allows the sedimentary basins to form
0:31once you go through this topic you will
0:35be able to know that what are the
0:37different kinds of sedimentary we seen
0:38that exist in nature you will able to
0:42understand what are the mechanisms
0:44behind their formation what are the
0:47controls beside the recent phil history
0:50and how the different machines they
0:53evolved through time you will also able
0:56to know that what are the different kind
0:58of maps that we prepare to know the
1:01history of the basin field now coming on
1:04to the detail of sedimentary basin what
1:07is the sedimentary basin it is a more
1:09protective depression on the crust of
1:12the earth that basically is it a
1:14depression that we call the sedimentary
1:16basin the question is that how the
1:18depression is formed but it is very
1:22essential to know that how the
1:24depression is formed how it is getting
1:26filled because many of the sedimentary
1:28basins that contains the different kind
1:30of valuable minerals including your coal
1:34oil and different kind of metals and to
1:37understand the history of the basin
1:40which will help us to know where the
1:43concentration of valuable minerals or
1:45oil or coal they are there and how to
1:47explore it how to exploit it we want to
1:51know the history of a beseen the
1:53tectonic history of a BC in the tectonic
1:55setting of a machine and then we can
1:58conclude that how we can best exploit
2:01the economic result present within the
2:04basin so with this aim that we go to
2:08these quotes of the sedimentary machine
2:10and discuss that what are the different
2:12kinds of sedimentary basins will get in
2:14nature now there are simple procedures
2:19of the sedimentary basin formation we
2:21classify those simple procedures into
2:24three different kinds of setting one is
2:26a
2:27Virgen one is a compressional and
2:29another is a strike-slip that is neither
2:33divergent nor compressional that is the
2:36different kind of setting now
2:38our present discussion about this Basin
2:41setting it will be principally in the
2:43light of the plate tectonics I am NOT
2:46going to the basin classification
2:48setting a scheme that was operative when
2:51before the plate tectonics came when we
2:53talked talked about the geosync lynal
2:56scheme earlier people used to believe in
2:59the geosynchronous scheme and the
3:01geosynchronous scheme used to tell that
3:03there is a myalgia syncline and there is
3:06a yugioh syncline and they are separated
3:09from each other by a structure called
3:11genetic line now this earlier thought of
3:15the Geo synclinal system that is being
3:18replaced by the plate tectonic theory
3:21and then the basin's we started talking
3:23about in terms of plate tectonics and
3:25when we talk about the plate tectonics
3:27then how the blessings we classified the
3:30classification was given the person
3:33ingersoll he classified the basis in
3:36terms of plate tectonics and the
3:37criteria he followed that whether the
3:40basin is on a continental crust or a
3:42oceanic crust this is number one number
3:44two that what kind of process is
3:48operating at the plate margin on who is
3:51the basin is there is it a divergent
3:53margin compressional margin or
3:55strike-slip margin and number three how
3:58proximal what is the proximity of the
4:01basin to the plate margin so based on
4:03these there are the separate that there
4:06are classification of the machines which
4:08are considered the inter plate machines
4:10the divergent machine the compressional
4:13basin and the strike-slip essence now if
4:16we'll go to the mechanism of the base
4:17information we normally divide the
4:21mechanism into three different classes
4:23one is a mechanical stretching number
4:26two is the thermal subsidence and number
4:29three it is a full land that is the
4:31loading and the and the subsidence of
4:34the missing now you will see the what
4:38first I will talk about the
4:40mechanical stretching the mechanical
4:43stretching it may sincerely we get in a
4:46system when you have the mantle plume or
4:50any kind of the triple Junction that is
4:53forming and there is a mechanical
4:56stretching that is the extension that is
4:58operated mostly in the extensional
5:01domain this is being formed and the best
5:04example is the East African Rift where
5:07we see this kind of extensional event
5:09now any extension in a extensional
5:13mechanical stretching that basically we
5:16give the mechanical stretching kind of
5:21situation second we come to the thermal
5:25subsidence this normally we get in the
5:28mid-ocean egregious where the ocean
5:30basins are formed and as you go away
5:33from the media listening mid-oceanic
5:35ridges then the edge of the crust which
5:37is formed that increases and as in the
5:40edge of the crust increases it gets
5:42cools and subsides so that is the
5:46thermal compensation and this thermal
5:48compensation calls the Pacer crust to be
5:51subsided and which is very operative in
5:54the oceanic crust now coming on to the
5:57pole and kind of setting now what is the
5:59pole and it is because of a load that is
6:02commonly the thrust load when you put a
6:04thrust load on any crust then there is a
6:07subsidence in the crust which is at the
6:10front of it depending on the flexural
6:14rigidity of the crust
6:16now this subsidence within the crust
6:19because of the load that will call the
6:22full land kind of setting
6:24now what will be the depth what will be
6:26the dimension of the subsidence all
6:28these depends on that flexural rigidity
6:31of the crust which is getting subsided
6:34now we will go into a little bit detail
6:38about the different kind of basin now
6:41first coming onto the extensional basin
6:44now if we come into the extensional kind
6:48of the same that base normally what we
6:51talk about
6:51there the two kinds of extensional kind
6:54of
6:54that is the intraplate Bhasin I am
6:56basically talking about the interplay be
6:58seen now in a interpolate machine which
7:02may transform into a inter plate setting
7:05this is basically a system where you
7:09have the mechanical stretching now
7:10mechanical stretching it can be again of
7:12two different types one is the active
7:14type stretching another is a passive
7:16type stretching now when we call the
7:20active type and passive type passive
7:23type is that when you have a stretching
7:25that is opening a machine in the craft
7:27without any involvement of the hot spot
7:30any bloom or any kind of the movement of
7:35the mental flow but there is a
7:37stretching then you call it a passive
7:40kind of stretching but the active
7:42stretching is that where you have the
7:44plume movement you have a hot spot and
7:46then by the movement of the mental away
7:49from that spot that causes the
7:51mechanical stretching in the upper layer
7:53and that is what is called the active
7:55stretching this active stretching this
7:59normally we presently there is no
8:02actively stretching machine that we get
8:04in our Indian continent but you get it
8:07in the East African continent you get
8:09the actively stretching basins that is
8:11there so this terrestrial rift valleys
8:14which is essentially a extensional
8:17setting there you can get as I have
8:19discussed that both active and the
8:21passive type but one very important
8:23character of that that you get the
8:25bimodal volcanics in that kind of basins
8:29now this character of this extensional
8:32machines it can be in the form of a full
8:36graben it can be a hub graben or it can
8:39be a horst and graben kind of situation
8:41I will explain inboard what we mean by a
8:45hub grabbin
9:07so this is a simplified picture of a hub
9:10grabbin you can see that this is the
9:13fault and which has subsided this part
9:16which is the hanging word part and this
9:18is the footwall part now this is a
9:21typical kind of this is the deep slope
9:23that is the hanging wall slope so the
9:25main sediment delivery in this case will
9:27be from this site and some small-scale
9:30conglomerate ik fans that will be
9:32generated from this side that is the
9:34footwall site so we can discuss that
9:37this is the typical kind of pattern for
9:39a hub graben where you have a steep or
9:42scarf that is the pond by the foot wall
9:45and the deep slope that is created by
9:47the hanging wall normally we gave the
9:50floovio delta ik system that is
9:52operative on the hanging wall whereas a
9:55fem delta which can be formed from the
9:57foot wall site that is the general
9:59character of it I can also have from a
10:03from this extension we can have a Horst
10:06and graben kind of situation Horst and
10:14graben kind of situation so this parts
10:16parts are called hosts and this is
10:19called gravel you get the thick sediment
10:24succession within the revenant but you
10:27do not get a very thick succession in
10:28the host one very important example of
10:31this horrible situation is our Bombay hi
10:33you all know that huge oil reserve of
10:36our Bombay high and that Bombay high is
10:39basically is a host kind of situation so
10:42these are some of the examples that when
10:46we get what are the character of
10:48extensional kind of basin which is
10:50operated when there is active or the
10:53passive kind of extension that is going
10:55on we can also have a proto ocean basin
10:59ripped trough kind of setting where the
11:04basin has a oceanic crust that means the
11:07basin has started opening that any kind
11:10of stretching that the mechanical
11:12stretching it led to the opening of the
11:14basin that is spreading but it has not
11:17spreaded to the pool so that kind of
11:20machine which started spreading and
11:21generated the oceanic crust but didn't
11:24evolve into a full-scale ocean basin
11:26that we call the proto cynic Ric trap
11:29the Red Sea is a classical example for
11:32that now we can also have some bussines
11:36which which are totally intact Ratanak
11:39in nature that is the SAG basins we are
11:42talking about the intricate onyx head
11:45bussines that suppose the in our in
11:48India the bindi on Kadapa Chhattisgarh
11:50which are a classical example of the
11:52interconnection be seen which has it was
11:56normally a Quaqua parcel deep and also
12:00you get a sagging in the central part
12:02then that sagging is either related to
12:05any kind of the earlier reef setting or
12:07the triple point Junction or any kind of
12:10plume activity that may be hidden below
12:12the surface in it we'll always saw the
12:16Depot Center in the middle and the on
12:18all sides that the sediment that will be
12:21edging out so that is the
12:23Intercontinental Samba scene then we
12:26also have then we go to the passive
12:30passive margin basin now what is the
12:32passive margin basin
12:33it is a transition from the continental
12:36to the mean that is what we call the
12:38passive margin Basin that means a
12:40mechanical stretching which has started
12:43it the the stretching that led to the
12:46spreading and then the drifting apart so
12:50reaped and that the spreading given way
12:53to the drift so the dripping of the
12:57continent that basically is that gave
13:01give rise to the formation of passing
13:04margin and the margin of the continent
13:07the classic example is of the our
13:09country's East Coast and West Coast if
13:12you say the both the East question is to
13:14see the East Coast what we can see that
13:17if you drill at the base you get the
13:20deeps which is the Wando and elites and
13:22that basically is a reason that the
13:26coast how the coast is formed and then
13:28there you get the large scale Delta's
13:30that pro-grade onto this passive margin
13:33setting
13:33so that is very important that what
13:36really is the passive margin setting now
13:39there are some bases which are very
13:40active basins and there are bases which
13:43are dormant basins classic example is
13:46Atlantic and Pacific if you see there
13:49Atlantis is a ever glowing the same
13:52because the in in both the sides of
13:56Atlantic you get the passive margin but
13:59Pacific is a if I shrinking machine
14:03because on both the side you get the
14:05subduction zone
14:06there are also doorman machines which
14:09neither grows and nor it is shrinks it
14:12is maintaining the Gulf of Mexico is the
14:14classic example that it is a dormant
14:17basing now I will come to the discussion
14:21or the convergent margin basins now
14:23there are a number of convergent margin
14:25basins if I go to board and draw then I
14:28can explain you that what are the
14:29different convergent margin vessels
14:59here I have drawn a cross-section of the
15:03trench arc system you can see this plate
15:07is going down this is the subducting
15:09plate and this plate is called
15:11overriding plate now the rate of
15:16subduction and the rate of convergence
15:20of the overriding plate that basically
15:23controls the entire story here if the
15:26rate of subduction is higher than the
15:30rate of convergence of the overlying
15:32plate then the trench that we call this
15:36portion that will call the trench that
15:40will start rolling back and there will
15:44be extension at the back of the magmatic
15:46arc and will open the back if the rate
15:49of subduction that the rate of
15:51subduction rate that is lower than the
15:54convergence rate in that case there will
15:57be compression here and we will not open
15:59the backer but there will be the retro
16:02are basins and if the two rates match
16:06that means in that case you have a
16:08neutral kind of situation where the
16:10trains will remain at the same place and
16:12the configuration will be maintained we
16:15call them the neutral arc system so
16:17extensional arc compressional arc and
16:20the neutral arc these are the three
16:22different situation that can arise by
16:24means of the different rate of
16:26subduction and the rate of convergence
16:28now we will come on to the different
16:30bussines that would form in this area
16:32first common to the Train it is the
16:36morphologic depression and that
16:38basically controls that that the plate
16:40is subducting through that cell so that
16:42the the trench that is a geophysical
16:46identified depression that what through
16:48who is the plate is subducted we also
16:51hear the train slope bussines which are
16:53structurally formed bussines
16:55on the accretionary prism that is the
16:58thrust which are scrapped from the
17:01downgoing plate and implicit on the
17:03downwind plane so as it is subducting
17:06the the material scrap from it it gets
17:09it gets implicit on it by
17:13means of low-angle trust and that
17:15bussines which will form between this
17:18different trust that is being that is
17:21impressed on it those what we get that
17:24the Train slope bussines now we get the
17:28porridge be seen this product be seen
17:30that is between the accretionary prism
17:33and the magmatic arc that depression
17:36that he called the product it is the
17:37same because there is a we I have
17:40already discussed that what is called
17:41Poland the Poland as I discussed that
17:45there is a load and because of the
17:47flexural rigidity does the subsidence in
17:50the crust because of the load that we
17:53call the Poland in our tents setting it
17:56is the same mechanism that forms the for
17:58Ark so there is a sub subsidence because
18:02of the implement and then that we call
18:04it a faux Rock the main supply of
18:07sediment in the product is from the
18:09magmatic arc and this magmatic arc the
18:12the beautiful example of the magmatic
18:15arc in our country that - you know the
18:18baron and the DAR condom islands which
18:20at the magnetic arc and this magmatic
18:22arc that that gets operative our and
18:25among islands that represents the
18:27accretionary prism and the Indian plate
18:29it is basically subducting below the
18:33eurasian plate all along the trains and
18:35that subduction has created the
18:38accretionary prism which is represented
18:41that the trains flow base in that tray
18:43is represented by the for the underman
18:46islands the underman see that represent
18:49the products sitting and depending on
18:52the extension of the compression i we
18:55can have the back arc in the back we
18:58have the extensional series there is the
18:59ocean oceanic crust that is formed or
19:02when there is a compression you get the
19:04retro occitane where there is a thrust
19:06belt that operates that we call it the
19:08retro rock sitting and the basin spawned
19:10on the first bill that we also known as
19:13the retro artisans so we have discussed
19:15the rhetoric machines now we also
19:18discussed the peripheral poland base in
19:20the peripheral poland machine it is
19:23basically that when there is a truss
19:25belt
19:26that is as I discussed earlier also that
19:29there is it there is a there is any
19:32subduction and you have the thrust and
19:36then the subsidence as I discussed that
19:40a peripheral Poland it is the similar
19:42that we get in the octant setting that
19:45is the for AK but when you have a large
19:48scalar suppose the Himalayan origin then
19:50the poor fool and machines which are the
19:52Poland machines even the today the
19:54entire Gangetic machine is a Poland
19:56machine because of the rising Amala and
19:58the huge load of Himalaya on the Indian
20:01cross then the subsidence of the inter
20:03kindy incretin that basically allowed
20:06that the full land base into form where
20:08the river Ganges that is operating that
20:11is the full language scene we also get
20:13the Poland in the problem of Shivalik
20:15that that is also a full land machine at
20:17that time that when the Himalaya is the
20:19early stage and then the subsidence in
20:22the nearby area that is also a full land
20:24machine
20:25so all these basins they are the
20:27peripheral to the main thrust load and
20:30then you call the subsidence that is the
20:32peripheral Poland listen now
20:36we also get the piggyback base in the
20:38piggyback bussines
20:40had those which are within the trust
20:43built so bases which are which it is
20:47holding within the frost belt then you
20:49call it a piggyback machine and there
20:51are some machines which we call the
20:53remnant machines these are the bases
20:55which remained as a remnant when there
20:57is a continuum contingent collision
20:59continent our collision so the bases
21:01that remain as a remnant within that
21:04system suppose of the Bay of Bengal
21:07basin so all these bussines
21:10that that is a part of the compressional
21:13setting that we have discussed in this
21:15now will come onto the strike-slip
21:17setting in the strike-slip setting there
21:20are three different kinds of setting
21:21that one is a translational machine one
21:24is the translational machine and trans
21:26rotational listen now the trans
21:29tensional we seen then you get a cup of
21:32the basin there is a pole bounded be
21:35seen this is a very
21:38since our subsidies it's sub-sites very
21:42easily and there is a large-scale
21:44subsidence that geothermal gradient is
21:46high and they are fault fault and the
21:48extensional margin on the two sides now
21:51there are bases which are translational
21:53where the Congressional force are
21:55operative on that Basin but when there
21:57is a block rotation about a axis and
21:59that forms a basin then we call it the
22:02trans rotational be seen
22:03so all these bases there even part of
22:05the strike-slip machine so if I if I if
22:08I go to board and draw a strike-slip
22:11basin then it will be more easier a
22:16simplified geometry of a strike-slip
22:18Basin where you can see that these are
22:20the two faults and they are in a
22:23strike-slip form and on that other side
22:26you get the compression on the two other
22:28margins of the basin so you can develop
22:30some machines that are basically by
22:33transfer extension and there are some
22:37basins which may form by compression so
22:40both the actions that is operative it is
22:42a very quickly subsiding base a
22:43geothermal gradient
22:44often becomes very high and this is a
22:47very good kind of situation for any kind
22:49of stratigraphic trap or the or any kind
22:51of hydrocarbon deserve that may be
22:53formed now there are some bases which
22:55are hybrid in nature now high ability
22:58since they are of different type suppose
23:01we can have a whole occasion that is a
23:03hybrid basin we can also have the
23:06intercontinental range machine we can
23:09have the impact again basin and then
23:12there may be successor the scene in case
23:15of colic odeon it is a fail raped that
23:18the one rift which couldn't open the two
23:20other limbs of the triple Junction that
23:22has opened in form of you can be seen
23:24but the other limb cannot open our
23:26Kambei Gulf of Cambay is a classic
23:28example that shows a kind of ala cogent
23:31it will be more spreaded more wide
23:34towards the sea and become narrow
23:36towards the continent that is the kind
23:39of situation in a collocation
23:41now if you go to the Intercontinental
23:44arrange machine this is a machine that
23:46formed on continental crust and it is
23:48affected by any distance the
23:51collisional origin or the collisional
23:53process and that affects and it forms in
23:55the continental ways the impacted in it
23:58forms at a high angle to the origin ik
24:00built that is the basic nature of the
24:03impact agent
24:04so in successor machine is that when it
24:07is formed in a Intermountain setting
24:10after the end of the tap hygienic
24:13activity then we call it a successor
24:15basin
24:16now what are the different kinds of map
24:19that we prepare to know the history of a
24:21basin we prepare different kinds of map
24:24suppose with people are the ISO pack map
24:26there is a equal thickness map that
24:28means this same lethality strata how
24:31what are the equal thickness of that
24:33strata in different part of the basin
24:35that is on the map when you represent
24:37then we call it a high so back map we
24:40also prepare the warmth I view map which
24:44is proposed by me all that on an
24:46unconformity what is the one lap history
24:48of a basin that on lap history that is
24:51mapped and that we call the worms eye
24:53view map we also prepared the Palio G of
24:55the pic map that is the PCs map in the
24:58space domain how the different phases
25:00that are there in the space domain in a
25:02basin that is also that mapped we also
25:06people who do different kind of ratio
25:08map such as this hand is to shell ratio
25:11map then the plastic it to carbonate
25:13ratio map so all these maps why we do
25:16this kind of map these maps allow us to
25:19interpret what is the feces distribution
25:22where is the Depot Center and how the
25:24different strata and the sediment they
25:26are distributed throughout the basin of
25:28the different tectonic history to know
25:31that so we generate the different kinds
25:33of map we also discuss the little basis
25:38map the little pieces map that that also
25:40allows us to know that what are the
25:43faces types that formed in the different
25:46kinds of setting now there are two
25:50different kinds of cross sections that
25:52also we do one is a master cross section
25:54and there is a static graphical
25:56structure in a master cross section what
25:59we do that we make a cross section on
26:02the surface depending on the
26:05so we will get the different fill
26:08history that different different Phyllis
26:10tree and different geological features
26:14that is there in the basin whereas when
26:18you talk about the stratigraphic a
26:20cross-section then there is the time
26:22connotation associated with that the
26:25time is associated with the different
26:27kind of lithology what we get and how
26:29the time and the lethality distribution
26:32in a time domain that can be explained
26:34that you call it the static epic map of
26:37the area in a text you will see that in
26:41a tabular form all the machines that is
26:44categorized in different kind of
26:46tectonic setting and what are the
26:48features that is the characteristic or
26:50the telltale feature to identify that
26:52kind of machine that has been given in
26:54the tabular form in the e-text where the
26:57what I have discussed in this that has
26:59been categorized and the tectonic
27:01history the basin and their character
27:04that is been clearly explained in a
27:06tabular from in the table now what I
27:09have discussed if I summarize this note
27:12how we get the basin is a mod protecting
27:15depression on the earth crust now that
27:17can be done by different kind of process
27:19some are mechanical process some a
27:22thermal process and some are the process
27:24related to loading on the class and the
27:26subsidence of the class because of the
27:28flexural rigidity when we talk about the
27:31stretching the stretching can be passive
27:33or active it can be related to a plume
27:35activity it can be related to a triple
27:37for injunction it may not be related to
27:39that and we get the different kind of
27:41grabbing situation Hubble urban
27:42situation horst and graben situation and
27:45depending on that some basins they may
27:47be ever-growing somebody machine may be
27:49sinking and all this depends that what
27:52kind of plate tectonics setting that is
27:54de marketing that the same as we have
27:56already discussed that Atlantic is a
27:58ever-growing base in Pacific say worse
28:00linking Basin we also get the arctan
28:06situation and the different kinds of
28:08basin that is formed that is we discuss
28:10the trains trains slope force of
28:12for our Baca retroarch piggyback all
28:15these different kinds of machines that
28:16can for
28:17in art and setting we also give the
28:19strike-slip situation and we have
28:21discussed that that there is a
28:23contention that the translation and the
28:26trans rotation so all these basins that
28:28is the different kind of behavior of the
28:30basin we also discuss the different
28:32kinds of maps that we prepare and those
28:35maps how they help that the type of map
28:37the ISO pack Mac isolate map the Palio
28:40faces map the ratio map the one my view
28:43map
28:44so all these maps that help us to know
28:46that how that the basin filling history
28:49that has gone in the space-time domain
28:51so I understand that this will help you
28:54in understanding that blessings can be
28:57of different type and they are dependent
28:59on the different kind of tectonic
29:00history at the different type of
29:02tectonic margin at the plate margin and
29:04that will encourage you to go for the
29:07further literature ever know that the
29:09basins of different tectonic margin how
29:11they form how they behave how they
29:13evolve and how they ultimately close so
29:16it is a history like a human being the
29:19basin has it it forms it evolves and
29:22then it closes so this will encourage
29:25you to know better and more by going to
29:28the further literature which is also
29:29mentioned in the e-text to know better
29:31about these machines and their histories
29:34now I believe you have enjoyed this
29:36course and thank you

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