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Author Topic:   Growing the Geologic Column
Faith 
Suspended Member (Idle past 1444 days)
Posts: 35298
From: Nevada, USA
Joined: 10-06-2001


Message 526 of 740 (734780)
08-02-2014 4:37 AM
Reply to: Message 519 by RAZD
08-01-2014 3:32 PM


other evidence the strata were all in place before the faulting
More important for this discussion is that the "Alban" sedimentary layers were all deposited well after the tectonic activity that caused these particular faults had ceased. Put this together with the top layer being deposited after all the other faults except the one at the extreme right had ceased activity, and you have two different periods when there was sedimentary deposition after tectonic activity and occurring with a large gap in time between them.
Maybe I'll get back to your post later, but I just have to point out that the evidence I see on that diagram is that the Albian could NOT have been deposited after the tectonic activity because it too is affected by it. If it had been deposited afterward its surface would have been level with respect to the layer it deposited on, but as you can see its shape conforms for the most part to the surfaces of those below. And really, the Base tertiary should show some signs of having originally had a horizontal surface as well if it was deposited after all the others were subjected to the faulting. I don't see any sign of that myself. Obviously the salt dome has pushed it up though, so that occurred after the layer was there.
And along this same line of thinking, to Percy in particular, anywhere in the stack you claim that deposition occurred after the faulting you should be able to show that it deposited horizontally there too. But although the strata get shifted a lot by the faults a basic parallel pattern between them is maintained for at least the upper half of the whole area.
I wonder what that lower layer is composed of, the one with the wavy lines top and bottom that maintains its straightness? The one that the salt has collected above.
Guess I should include the diagram here too:
Edited by Faith, : No reason given.
Edited by Faith, : No reason given.
Edited by Faith, : No reason given.
Edited by Faith, : No reason given.
Edited by Faith, : No reason given.
Edited by Faith, : No reason given.

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Faith 
Suspended Member (Idle past 1444 days)
Posts: 35298
From: Nevada, USA
Joined: 10-06-2001


Message 527 of 740 (734781)
08-02-2014 4:52 AM
Reply to: Message 515 by edge
08-01-2014 10:29 AM


Re: whatever
Show us a picture of an angular unconformity forming today.

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 Message 515 by edge, posted 08-01-2014 10:29 AM edge has replied

Replies to this message:
 Message 529 by edge, posted 08-02-2014 9:28 AM Faith has replied

  
RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


(1)
Message 528 of 740 (734783)
08-02-2014 8:25 AM
Reply to: Message 526 by Faith
08-02-2014 4:37 AM


cyclic faulting, some faults reactivate, some don't
Maybe I'll get back to your post later, but I just have to point out that the evidence I see on that diagram is that the Albian could NOT have been deposited after the tectonic activity because it too is affected by it. ...
Sedimentary deposition occurs, then tectonic activity occurs, then sedimentary deposition occurs, then tectonic activity occurs ... a cyclic pattern.
To use your own argument you don't know that the tectonic activity that produced the faults through the Albian could NOT have occurred before that layer was deposited, and then SOME of them were reactivated during later tectonic activity, while some were not.
From direct observation we KNOW that tectonic activity tends to reoccur along fault lines, ANS we KNOW there is a good reason for this - the rock structure is weaker due to previous faulting - so ANY fault line can have periodic activity continuing, even while sedimentary deposition occurs. Thus it is not possible to say that the fault lines crossing the Albian deposit only occurred after the deposition of all the layers.
But in any event the four faults at the left show activity before the Albian layer was deposited. That is clear from the diagram.
Enjoy.

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edge
Member (Idle past 1706 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(2)
Message 529 of 740 (734785)
08-02-2014 9:28 AM
Reply to: Message 527 by Faith
08-02-2014 4:52 AM


Re: whatever
Show us a picture of an angular unconformity forming today.
I know this will be difficult for you because it depicts a process that is only in progress and not complete.
However, my favorite example would be the Valley and Ridge Province in Pennsylvania.
Would you agree that these rocks are folded?
Woudl you agree that they are also presently being eroded?
Would you not agree that if this landscape were inundated by the sea that it would begin to received sediments that would eventually bury the shown topography?
Would that not create an angular unconformity?
We live on an unconformity. It may be one of the largest in geological history. In some places the rocks at the surface are folded and when they are reburied, it will present an angular unconformity.
Here is a close-up of an angular unconformity in the process of forming. In this case a soil has developed on top of the folded rocks.

This message is a reply to:
 Message 527 by Faith, posted 08-02-2014 4:52 AM Faith has replied

Replies to this message:
 Message 543 by Faith, posted 08-02-2014 1:25 PM edge has replied

  
edge
Member (Idle past 1706 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(1)
Message 530 of 740 (734786)
08-02-2014 9:40 AM
Reply to: Message 526 by Faith
08-02-2014 4:37 AM


Re: other evidence the strata were all in place before the faulting
Maybe I'll get back to your post later, but I just have to point out that the evidence I see on that diagram is that the Albian could NOT have been deposited after the tectonic activity because it too is affected by it.
But not by all of the tectonism. The deeper rocks are more affected and the uppermost rocks are least affected. In fact, the data show that some of the faults do not even project upward into the Albian rocks on the right side of the diagram.
There is no other viable interpretation than that some deformation has been occurring at the location throughout geological time.
And really, the Base tertiary should show some signs of having originally had a horizontal surface as well if it was deposited after all the others were subjected to the faulting.
You do realize that you just contradicted your whole premise here? So the Tertiary was not affected by many of the faults? How do you explain this?
And along this same line of thinking, to Percy in particular, anywhere in the stack you claim that deposition occurred after the faulting you should be able to show that it deposited horizontally there too.
Why this qualification? It is pretty clear that the younger rocks are nowhere nearly as deformed as the Paleozoic, and it's pretty clear that the deformation decreases upward. Horizontality was probably the case, but that's irrelevant right now.
But although the strata get shifted a lot by the faults a basic parallel pattern between them is maintained for at least the upper half of the whole area.
Exactly. The shallower rocks are less deformed. As we have been saying all along.

This message is a reply to:
 Message 526 by Faith, posted 08-02-2014 4:37 AM Faith has replied

Replies to this message:
 Message 538 by Faith, posted 08-02-2014 12:52 PM edge has replied

  
Percy
Member
Posts: 22392
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.3


(2)
Message 531 of 740 (734787)
08-02-2014 9:47 AM
Reply to: Message 362 by Faith
07-29-2014 8:10 AM


Re: igneous layers
Hi Faith,
I devote a little time each day to this thread, and yet I'm still over 150 messages behind. But if it keeps raining today then I'll have to stay indoors and should have a little extra time.
Faith writes:
Let's get something in perspective here. The interspersed layers do not meet the original conditions.
Well, your habit is to reveal what it is you're truly looking for only a little bit at a time, but evidence of volcanic layers in the form of basalt and tuff interspersed with sedimentary layers have been provided for you, and it's far more than just the Cardenas. I could browse through the thread and pick out the images showing this, but I hesitate to devote the time because I'm already so far behind. If you need me to find them for you please let me know.
One thing mentioned at least once already in this thread (by Dwise1) bears repeating. Non-metamorphic sedimentary layers are not often directly amenable to radiometric dating. They're made up of material that tends to come from a huge variety of sources spread across an entire drainage region. The particles comprising sedimentary layers have their origin in many places and from many times. This origin means that radiometric dating of sedimentary material would be meaningless for purposes of determining the date of formation of a sedimentray layer, and so they are dated using the volcanic deposits contained within them. The originally molten state of volcanic deposits set their radiometric clocks to zero, making accurate radiometric dating possible.
Volcanic layers appear infrequently in diagrams of geologic layers because most volcanic eruptions are local in extent. Most volcanoes don't leave lava and ash deposits extending across thousands of square miles. This isn't always the case, but it is certainly most often the case. A volcanic eruption affects a roughly (very roughly) circular region. Lava flows down the mountainside, but often not very far before it cools too much to flow. Volcanic ash will distribute across a broader region, but often not very far in any significant amounts. Here's a diagram of the lava and ash distribution from Mount St. Helens. Note that there wasn't any significant lava flow that would have left a basalt layer. There was a pyroclastic flow (which was 1/3 lava), there was a mud flow, and there was a lateral blast of ash that left significant deposits locally, but nothing of significance beyond 10 or 20 miles. The Mount St. Helens eruption devastated a vast region and yet left no evidence behind except in the region immediately nearby:
So if an eruption as big as Mount St. Helens in 1980 produced virtually no basalt layer whatsoever, and a tuff layer in a rough 10-mile radius, you can see why basalt and tuff layers will not be anywhere near as common as sedimentary layers. Some eruptions produce almost no lava flow, some a little, some a lot. Some produce ash deposits locally, some across a broad region. It varies, and in most circumstances the lava doesn't flow far from the volcano, and the ash, though it travels further, doesn't usually travel that far. Events like the Siberian Traps where volcanoes erupted for millions of years and left basalt layers across a region the size of Greenland do not occur often.
A coastline thousands of miles long can transgress and regress across the continent leaving sedimentary layers huge in extent, like those at the Grand Canyon, but in this relatively tectonically quiet region volcanoes occur only occasionally and on a relatively modest scale. That there were local volcanic eruptions during the formation of all the layers of the Grand Canyon will not be reflected in any generalized diagram of the geologic column. In a geologic diagram intended to be representative of thousands of square miles it wouldn't be accurate to show a basalt layer for a volcanic eruption that deposited only a square mile of lava. Even the huge series of eruptions that occurred geologically recently from 725,000 to 100,000 years ago in the western canyon isn't usually represented in diagrams of the Grand Canyon region.
All this means that the volcanic deposits of basalt and tuff used to date sedimentary layers are usually local in extent and not represented in geologic diagrams, except when the diagram is for a small region, or when the eruptions were huge in extent, like the Siberian Traps. But of course these volcanic layers exist, and they're mentioned in the technical literature. Even the RATE group in their report Radioisotopes and the Age of the Earth mentions volcanic deposits in sedimentary layers when they describe a "high priority experiment" they'd like to perform on page 16:
RATE group writes:
Select an initial sample from a tuff bed in the Muav Formation of Grand Canyon.
Even the RATE group knows the sedimentary record is dotted with volcanic deposits.
--Percy

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edge
Member (Idle past 1706 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 532 of 740 (734788)
08-02-2014 9:48 AM
Reply to: Message 524 by Faith
08-02-2014 3:43 AM


Re: Order of events as shown on cross sections
This is all interpretive stuff. You have no more support than I do for your interpretation.
Yes, well-supported interpretations. Do you have a problem with that? And just where is your supporting evidence?
For instance, I have just given you evidence that angular unconformities exist in the present and that we have a pretty good idea how they form, by direct observation.
Now, please provide us with evidence for your explanation of angular unconformities.

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 Message 524 by Faith, posted 08-02-2014 3:43 AM Faith has not replied

  
edge
Member (Idle past 1706 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(1)
Message 533 of 740 (734789)
08-02-2014 10:09 AM
Reply to: Message 523 by Faith
08-02-2014 3:41 AM


Re: cross section shows all layers were in place except top one
Not at all, not when you can see the same layers those faults cut through continuing on across the formation where other faults cut through not only those layers but all those above, which would of course have to have happened after the faulting on the right as you are thinking of it, but there is really nothing to prove that was the order of things.
Faith, if you have other information than that shown on the diagram, this would be a good time to let us know.
The fault just to the left of that section of strata that lies beneath the Late Jurassic Shelf Edge, occurred with the pushing up of that whole section, leaving the very same strata on the left lower in the stack. That's all that happened there. All the strata were already in place at that time. Probably also the Base tertiary but of course that can't be proved based on the fault lines.
But, Faith, why don't all of the faults cut entirely through the section if, as you say, they were all present at the time of faulting?
Well you're good at the OE fairy tale, I'll give you that. Of course there were no millions of years, no eroded layers of an imaginary unconformity, just all the strata laid down in sequence and faulted and deformed according to whatever forces acted upon various parts of it.
Let's see... Who said this?
I just wouldn't be dogmatic about it if I were you.
Heh, heh...
This discussion has gone comic.
A NOTE ON INTERPRETIVE VERSUS PRACTICAL GEOLOGY
Now, all this is a perfect example of what I'd been calling "historical Geology" that is all nothing but unprovable untestable interpretations.
Actually, it is tested every day by people working with it in the field.
I'm calling it Old Earthism now because that other term apparently includes more than I want to include. But the principle is quite clear. You've got the whole OE interpretive system going there without any way to verify it.
Yes, you just said that. Actually, we test the OE ideas by using them every day. If they didn't work, we'd know it.
Using the very same data I just answer with my own interpretive system which I think is a lot more plausible.
No, you do not use the same data. For instance, you ignore radiometric dates and relative dating methods by cross-cutting features (this is shown by your erroneous interpretation of the Gulf Coast cross sedtion). And, in fact, you make up a bunch of stuff also, like the abrasion effects at angular unconformities. They just don't exist.
For the purposes of Practical Geology none of this should matter, just the positions of the rocks relative to each other. If the Base tertiary was laid down before the faulting or after doesn't matter, ...
Evidently, your position has changed here. You said that all rocks were deposited prior to all deformation and volcanism. We have shown that to not be the case. Now, it's not important to you?
... all that matters for practical purposes is where the rocks are now.
Negative. Genetic models are important in all geological studies. I know that they are not important to you, but how the rocks got to be the way they are is part and parcel to the science. It is laughable that you can sit there and deny centuries of successful geological interpretation based on a religious myth.

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 Message 523 by Faith, posted 08-02-2014 3:41 AM Faith has not replied

Replies to this message:
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JonF
Member (Idle past 168 days)
Posts: 6174
Joined: 06-23-2003


Message 534 of 740 (734792)
08-02-2014 11:05 AM
Reply to: Message 531 by Percy
08-02-2014 9:47 AM


Re: igneous layers
And the RATE group knows there are non-intrusive igneous rocks in the Muav. Smack dab in Faith's geologic column and yet another thing we observe that she says is impossible.

This message is a reply to:
 Message 531 by Percy, posted 08-02-2014 9:47 AM Percy has seen this message but not replied

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herebedragons
Member (Idle past 857 days)
Posts: 1517
From: Michigan
Joined: 11-22-2009


(1)
Message 535 of 740 (734794)
08-02-2014 11:14 AM
Reply to: Message 533 by edge
08-02-2014 10:09 AM


Re: cross section shows all layers were in place except top one
Could you explain what you mean by "genetic model"? It sounds more biological than geological.
When I did a search on that term, this chapter in a book came up. I only briefly looked at it, but it seems to be the very kind of thing being discussed - how the history of a region is used to determine where to look for minerals. Perhaps you could take a look at it and make some comments on it that may help a layman like me to understand what they are talking about (it is quite technical). It may actually be more on topic over at the SCIENCE: -- "observational science" vs "historical science" vs ... science. thread, if you would want to comment on it over there.
Please?
HBD
Edited by herebedragons, : Added undignified pleading

Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca
"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.
Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.

This message is a reply to:
 Message 533 by edge, posted 08-02-2014 10:09 AM edge has replied

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herebedragons
Member (Idle past 857 days)
Posts: 1517
From: Michigan
Joined: 11-22-2009


Message 536 of 740 (734795)
08-02-2014 11:17 AM
Reply to: Message 534 by JonF
08-02-2014 11:05 AM


Re: igneous layers
non-intrusive igneous rocks in the Muav
Do you have a source? I was actually looking for something along these lines but didn't find anything.
HBD

Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca
"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.
Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.

This message is a reply to:
 Message 534 by JonF, posted 08-02-2014 11:05 AM JonF has replied

Replies to this message:
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edge
Member (Idle past 1706 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(1)
Message 537 of 740 (734809)
08-02-2014 12:46 PM
Reply to: Message 535 by herebedragons
08-02-2014 11:14 AM


Re: cross section shows all layers were in place except top one
Could you explain what you mean by "genetic model"? It sounds more biological than geological.
Perhaps I can clarify. You can think of it as 'ore genesis' in the mining business. What are the facts surrounding the formation of a deposit that tell you how it formed? We use such models to explore and develop resources, whether it's kitty litter, diamonds, baking soda, oil or copper.
It usually means all of the features, processes and timing by which a geological deposit forms. It could include the source rocks, fluid sources, the transport chemistry and depositional environment, geological age, the timing of faulting, etc., etc.
For a specific, RW example, I might envision the development of a a half-graben and thermal lake in a volcanic field with explosive breccias, and so on. It can be as involved as you wish.
When I did a search on that term, this chapter in a book came up. I only briefly looked at it, but it seems to be the very kind of thing being discussed - how the history of a region is used to determine where to look for minerals. Perhaps you could take a look at it and make some comments on it that may help a layman like me to understand what they are talking about (it is quite technical). It may actually be more on topic over at the SCIENCE: -- "observational science" vs "historical science" vs ... science. thread, if you would want to comment on it over there.
This is exactly correct.
Okay, I'll try to clarify with some ensuing posts. The gist of it is that if you can reconstruct the history and controls on where/when a mineral deposit occurs, it makes exploration and development a lot easier.
To keep it on topic here, age dates can be an important part of the process. Faith keeps harping on the sedimentary sequence, but sometimes we do not have a visible sequence of events. For instance, there may be two intrusive rocks present in an area, but we may not be able to tell the relative ages, much less the absolute ages. If a 12my, intrusive is known to be more productive in the region, it would help to know both of ages in order to spend money efficiently. If we know the absolute ages, we also know the relative ages.
I hope this helps. Please feel free to ask questions. I really don't expect Faith to get much our of it, but really, if there's on thing I like to emphasize it's that these things are usually more complex than we'd like.

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Faith 
Suspended Member (Idle past 1444 days)
Posts: 35298
From: Nevada, USA
Joined: 10-06-2001


Message 538 of 740 (734810)
08-02-2014 12:52 PM
Reply to: Message 530 by edge
08-02-2014 9:40 AM


Re: other evidence the strata were all in place before the faulting
I don't think you got what I was trying to say. Which was that layers deposited above and after the tectonic distortion should be horizontal on their surface, since sediments deposit horizontally, but they aren't, they conform to the surface shape of the lower rocks. If they were deposited later and then deformed later as well they also wouldn't conform to the shape of the lower rocks, they would have their own pattern of deformation independent of them. But the Albian for one, except at the far left, keeps parallel to the shape of the lower rocks all the way to the far right. Why doesn't it have a flat horizontal surface, or at least a surface deformed differently from the rocks below it? It isn't just a matter of degree of deformation as you are saying, it's also a matter that the deformation maintains a mostly parallel form when a layer laid down later should have its own different pattern of deformation.
And I was also suggesting that it is probably true of the Base tertiary as well: I've already noted that the faults do not penetrate into that layer, which is of course an argument that it was laid down afterward, but an argument that contradicts that is the lack of a horizontal surface which shows that it was deformed right along with all the rest of them even if the faults don't go all the way through. I also noted that the salt dome does penetrate through it, even raising its surface, showing at least that that part of the deforming forces came later.
Edited by Faith, : No reason given.

This message is a reply to:
 Message 530 by edge, posted 08-02-2014 9:40 AM edge has replied

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 Message 540 by edge, posted 08-02-2014 1:11 PM Faith has replied

  
Faith 
Suspended Member (Idle past 1444 days)
Posts: 35298
From: Nevada, USA
Joined: 10-06-2001


Message 539 of 740 (734811)
08-02-2014 12:58 PM
Reply to: Message 537 by edge
08-02-2014 12:46 PM


Re: cross section shows all layers were in place except top one
...it would help to know both of ages in order to spend money efficiently. If we know the absolute ages, we also know the relative ages.
So you send samples for radiometric testing?

This message is a reply to:
 Message 537 by edge, posted 08-02-2014 12:46 PM edge has replied

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 Message 541 by edge, posted 08-02-2014 1:13 PM Faith has replied

  
edge
Member (Idle past 1706 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(1)
Message 540 of 740 (734814)
08-02-2014 1:11 PM
Reply to: Message 538 by Faith
08-02-2014 12:52 PM


Re: other evidence the strata were all in place before the faulting
I don't think you got what I was trying to say. Which was that layers deposited above and after the tectonic distortion should be horizontal on their surface, since sediments deposit horizontally, but they aren't, they conform to the surface shape of the lower rocks.
Yes, it shows that the deformation is ongoing and that it started a long time ago. I would expect this in a place such as the Mississippi Delta and the Gulf of Mexico as sediments compact and dewater at depth.
I think you are missing the point that deformation is decreasing upward.
If they were deposited later and then deformed later as well they also wouldn't conform to the shape of the lower rocks, they would have their own pattern of deformation independent of them.
I'm not sure why you would say this. They do have their own pattern which is 'less deformed' than the lower rocks. The fact that the deformation is occurring in the same tectonic setting means that they will have some similarities, but the intensity is less.
But the Albian for one, except at the far left, keeps parallel to the shape of the lower rocks all the way to the far right. Why doesn't it have a flat horizontal surface, or at least a surface deformed differently from the rocks below it?
The entire pile of sediment is settling, and there is no reason why a surface should remain perfectly flat. In fact, if what you said were true, the salt would never flow. And that flow is just another factor in the irregularities of the formation contacts.
It isn't just a matter of degree of deformation as you are saying, it's also a matter that the deformation maintains a mostly parallel form when a layer laid down later should have its own different pattern of deformation.
Some styles of deformation are inherited either from previous events or from boundary conditions such as the direction of forces.
And I was also suggesting that it is probably true of the Base tertiary as well: I've already noted that the faults do not penetrate into that layer, which is of course an argument that it was laid down afterward, but an argument that contradicts that is the lack of a horizontal surface which shows that it was deformed right along with all the rest of them even if the faults don't go all the way through.
The beginning of the Tertiary was over 50million years ago. I would expect the base to be irregular in the settling of a pile of sediments.
I also noted that the salt dome does penetrate through it, even raising its surface, showing at least that that part of the deforming forces came later.
There could be several reasons for this.
Faith, you continue to grope for interpretations that fit your preconceived notions. It won't work.

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 Message 538 by Faith, posted 08-02-2014 12:52 PM Faith has replied

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