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Author Topic:   Mechanisms of sea transgression and regression
Adminnemooseus
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(3)
Message 1 of 15 (806346)
04-24-2017 9:04 PM


This is a spin-off of the "The TRVE history of the Flood..." topic, which is currently at message 515.

I'm not posting any real material to start this topic, rather I encourage the forums geologists (and other geologically inclined) to chip in there thoughts.

The question is, "How did the sea transgressions and regressions of the Earth's geologic history happen"? This is, as in the frame of mainstream old age thought. I don't want any "young Earth" flood geology in this topic.

Davidjay, you best stay out of this topic.

Adminnemooseus


Or something like that.

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edge
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From: Colorado, USA
Joined: 01-09-2002
Member Rating: 4.7


Message 2 of 15 (806603)
04-26-2017 8:06 PM
Reply to: Message 1 by Adminnemooseus
04-24-2017 9:04 PM


I'm not posting any real material to start this topic, rather I encourage the forums geologists (and other geologically inclined) to chip in there thoughts.

The question is, "How did the sea transgressions and regressions of the Earth's geologic history happen"? This is, as in the frame of mainstream old age thought. I don't want any "young Earth" flood geology in this topic.


I believe that most geologists would attribute inter-regional transgressions to plate tectonics in that a surge of mid-ocean ridge volcanism would swell the ridges to such an extent that they would displace seawater onto the continental masses.

ETA: This would be supported by the fact that the Cretaceous Period seems to be a time of increased ocean ridge volcanism (i.e., wide bands of Cretaceous sea floor on either side of the mid-ocean ridges) that would correspond to the Zuni transgression.

This would, of course result in global dimensions for the transgressions and yet we don't see evidence of such on all continents.

I recently read of the possibility that depending on climate, the degree of erosion going on at any one place might mask the effect of a transgression and/or regression. That would make some sense.

I'm also of the opinion that some continents might be undergoing a significant degree of orogeny due to the local effects of subduction or continental collision that would also affect the amount of both erosion and deposition.

Edited by edge, : No reason given.


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Faith
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From: Nevada, USA
Joined: 10-06-2001
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Message 3 of 15 (806607)
04-26-2017 9:04 PM
Reply to: Message 2 by edge
04-26-2017 8:06 PM


... the Cretaceous Period seems to be a time of increased ocean ridge volcanism (i.e., wide bands of Cretaceous sea floor on either side of the mid-ocean ridges

What is the evidence that this increased ocean ridge volcanism occurred in the Cretaceous period? What is "Cretaceous sea floor?"


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edge
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Posts: 3904
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 4.7


Message 4 of 15 (806637)
04-27-2017 12:38 AM
Reply to: Message 3 by Faith
04-26-2017 9:04 PM


What is the evidence that this increased ocean ridge volcanism occurred in the Cretaceous period? What is "Cretaceous sea floor?"

The width of the Cretaceous seafloor bands extending away from the mid-ocean ridges are wider for the number of years than other periods. This is known due to radiometric dating and correlation of magnetic signature of the oceanic crust. This suggests a temporary increase in the amount of seafloor spreading and the volcanism that would accompany it.
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Minnemooseus
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Message 5 of 15 (806638)
04-27-2017 1:16 AM
Reply to: Message 4 by edge
04-27-2017 12:38 AM


Increased Cretaceous seafloor spreading rates
This is something I've tried to research in the past, and didn't come up with much information.

It may be difficult for you to have the information, but my question is, was this increased spreading rate confined to one ocean or was it multiple locations?

Also, was there increased subduction zone volcanism associated with this increased spreading rate?

Was there orogeny/mountain building associated with this increased spreading rate?

(can't remember ****, of my historical geology class) Moose


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Percy
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Posts: 15706
From: New Hampshire
Joined: 12-23-2000
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Message 6 of 15 (806662)
04-27-2017 8:27 AM
Reply to: Message 2 by edge
04-26-2017 8:06 PM


edge writes:

I believe that most geologists would attribute inter-regional transgressions...
...
This would, of course result in global dimensions for the transgressions...

I don't understand why the focus on global and inter-regional transgressions. Aren't most transgressions/regressions more limited in extent and a result of local interactions between sea height and subsidence/elevation?

--Percy


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edge
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Posts: 3904
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 4.7


Message 7 of 15 (806732)
04-27-2017 11:21 AM
Reply to: Message 6 by Percy
04-27-2017 8:27 AM


I don't understand why the focus on global and inter-regional transgressions. Aren't most transgressions/regressions more limited in extent and a result of local interactions between sea height and subsidence/elevation?

Most probably are more local or regional.

Cratonic Sequences are a unifying theory that blend a lot of data but don't provide a lot of details. In a way, it's kind of like evolution, but on a more modest level.


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edge
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Posts: 3904
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 4.7


(1)
Message 8 of 15 (806739)
04-27-2017 11:34 AM
Reply to: Message 5 by Minnemooseus
04-27-2017 1:16 AM


Re: Increased Cretaceous seafloor spreading rates
This is something I've tried to research in the past, and didn't come up with much information.

It may be difficult for you to have the information, but my question is, was this increased spreading rate confined to one ocean or was it multiple locations?


That's a good question. I don't know, but the Pacific Basin shows it more readily because the plates are moving so much faster. When there are continents associated with the plates they tend to move more slowly.

Also, was there increased subduction zone volcanism associated with this increased spreading rate?

Was there orogeny/mountain building associated with this increased spreading rate?


For western NA, most definitely. You see an increase in volcanism into the Tertiary and you see several orogenic episodes starting in the Jurassic. These are mostly related to increased subduction rates along the western edge of the NA Plate.

While these are regional effects, one might expect some global consequence since sea level is more or less a global feature. However, there are a lot more variables than just seafloor spreading activity.


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Faith
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From: Nevada, USA
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Message 9 of 15 (806839)
04-28-2017 11:03 AM
Reply to: Message 8 by edge
04-27-2017 11:34 AM


Re: Increased Cretaceous seafloor spreading rates
You see an increase in volcanism into the Tertiary and you see several orogenic episodes starting in the Jurassic.

So, to be clear, is all such dating to time periods done by radiometric methods? When it is said that mountains formed in such a such a time period, that's due to radiometric measurement? Of what, exactly? Is that how the Cratonic transgressions are dated? (And is anyone paying attention to all this in relation to the movement of the Supercontinents and the breakup of Pangaea and all that? Because the seafloor would not have spread as far in the Cretaceous as today for instance. Is all that being taken into account?

ABE: So for instance if Pangaea broke up in the Jurassic there was really not a lot of seafloor formed by the Cretaceous? )

Edited by Faith, : No reason given.


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edge
Member
Posts: 3904
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 4.7


Message 10 of 15 (806878)
04-28-2017 4:58 PM
Reply to: Message 9 by Faith
04-28-2017 11:03 AM


Re: Increased Cretaceous seafloor spreading rates
So, to be clear, is all such dating to time periods done by radiometric methods? When it is said that mountains formed in such a such a time period, that's due to radiometric measurement? Of what, exactly? Is that how the Cratonic transgressions are dated?

Most absolute dates are radiometric. I think some are bioichronological. Relative ages are still how we describe them, such as Ordovician or Cretaceous.

quote:
(And is anyone paying attention to all this in relation to the movement of the Supercontinents and the breakup of Pangaea and all that?

Yes, that's the whole idea. We are not like YECs in applying ad hoc solutions to questions.

Because the seafloor would not have spread as far in the Cretaceous as today for instance. Is all that being taken into account?

I'm not sure what you are asking.

ABE: So for instance if Pangaea broke up in the Jurassic there was really not a lot of seafloor formed by the Cretaceous? )

Well, yes that's pretty much what happened. For instance, there basically isn't much seafloor older than Jurassic unless it's been accreted to the continents. Part of that is due to more recent rifting as you suggest, but much is due to subduction which is kind of the ultimate fate of old, thick oceanic crust.

So, likewise, if rifting started in the Cretaceous, there would be less Cretacesous and no Jurassic seafloor.


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Pressie
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From: Pretoria, SA
Joined: 06-18-2010
Member Rating: 3.2


Message 11 of 15 (813952)
07-03-2017 5:22 AM
Reply to: Message 1 by Adminnemooseus
04-24-2017 9:04 PM


Adminnemooes writes:

"How did the sea transgressions and regressions of the Earth's geologic history happen"?

Lots of different ways as can be witnessed in my country today.

1. Plate tectonics (splitting of continents, island arcs forming, continents moving, etc. etc).
2. Isostatatic changes.
3. Sea level changes.
4. Climate changes.
5. Inland lakes forming and disappearing.
6. Rivers becoming bigger or smaller.
7. Deserts forming.
8. Erosion.
9. Sedimentation such as big tombolos forming, etc.
10.Etc. Etc

Literally lots of different scenarious. Processes similar to what is happening all over the world today. The present is the key to the past.


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Pressie
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From: Pretoria, SA
Joined: 06-18-2010
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Message 12 of 15 (813953)
07-03-2017 5:27 AM
Reply to: Message 3 by Faith
04-26-2017 9:04 PM


Faith writes:

What is "Cretaceous sea floor?"

Sea floor formed during the Cretaceous. I'm not sure why you are asking the question.
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Pressie
Member
Posts: 1714
From: Pretoria, SA
Joined: 06-18-2010
Member Rating: 3.2


Message 13 of 15 (813964)
07-03-2017 7:48 AM
Reply to: Message 9 by Faith
04-28-2017 11:03 AM


Re: Increased Cretaceous seafloor spreading rates
Faith writes:

So, to be clear, is all such dating to time periods done by radiometric methods?

Some. Others not. That's the beauty of it. Lots of different methods provide similar ages.

Edited by Pressie, : No reason given.


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Pressie
Member
Posts: 1714
From: Pretoria, SA
Joined: 06-18-2010
Member Rating: 3.2


Message 14 of 15 (813967)
07-03-2017 8:01 AM
Reply to: Message 9 by Faith
04-28-2017 11:03 AM


Re: Increased Cretaceous seafloor spreading rates
I'm not too sure why you pretend to be interested in the Cretaceous. I mean, you believe that the earth is less than 10 000 years old.

Oh, and Faith. Before you forget. Let's remind you that the Cretaceous in not a "rock layer".

Edited by Pressie, : No reason given.

Edited by Pressie, : No reason given.


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JonF
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Joined: 06-23-2003
Member Rating: 3.2


Message 15 of 15 (813983)
07-03-2017 9:56 AM
Reply to: Message 9 by Faith
04-28-2017 11:03 AM


Re: Increased Cretaceous seafloor spreading rates
So, to be clear, is all such dating to time periods done by radiometric methods?

No, although radiometric methods are by far the most accurate and convenient.

One thing you are forgetting is that "radiometric methods" covers a plethora of different and independent techniques that are used to cross-check each other. Nobody's ever come up with any physically possible ideas on how the results of all these techniques could be changed and still agree.

Of course for times less that 50,000 years there is a score of methods, all of which agree. That agreement the most difficult thing for creationists to address, so they never try. But for significantly older ages there are some techniques.

Milankovitch cycles leave evidence behind that we can use for absolute dating.
Sunquakes have changed over time as helium accumulates in the core, and that can used to calculate the ages of meteorites, and that calculation agrees with radiometric methods.
Amino Acid Racemization can date items as old as two million years if they happen to have been preserved in ideal conditions (e.g. Antarctica).

Edited by JonF, : No reason given.


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