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Author Topic:   "The Flood" deposits as a sea transgressive/regressive sequence ("Walther's Law")
edge
Member (Idle past 935 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


(1)
Message 219 of 224 (821811)
10-13-2017 12:12 AM
Reply to: Message 218 by RAZD
10-09-2017 10:28 PM


Re: What I expect from Walther's Law for Delta Formations
why does that picture make me think of a penguin

I thought it was a ghost ...

Which may be appropriate since the delta will be lost in the geological record as a lobe of channels and sands and overbank deposits at the base of a transgressive beach sand.


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 Message 218 by RAZD, posted 10-09-2017 10:28 PM RAZD has seen this message

Replies to this message:
 Message 220 by Pressie, posted 10-13-2017 6:51 AM edge has replied

  
edge
Member (Idle past 935 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 221 of 224 (821878)
10-13-2017 10:08 PM
Reply to: Message 220 by Pressie
10-13-2017 6:51 AM


Re: What I expect from Walther's Law for Delta Formations
Good points. Unfortunately, it has to be kind of basic. Deltaic deposits could consume a career in geology. The thing that makes it easier is the presence of those transgressive sands. I am familiar with the 20 Mile Sandstone in the Willaims Fork Formation of Colorado. A great marker bed and easy geology. Some nice fossils too.
They tend to preserve nice seams below them. There are some regressive sands above, usually disncontinuous and much thinner.

So, for the layman, think of the delta deposits as a kind of swamp, partly marine partly terrestrial. The coal seams would represent a swampy area of high organic content ... and a river runs through it ... The beach is always there on a delta because waves wash the silt away and that sand moves along the shore with currents to form beaches far away. As the sea level rises, the beach moves inland until the high stand is reached and the sea recedes again. This happened numerous times in North America during the late Paleozoic and again in the late Cretaceous. Not sure what/ when happened in South Africa.


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 Message 220 by Pressie, posted 10-13-2017 6:51 AM Pressie has replied

Replies to this message:
 Message 222 by Pressie, posted 10-17-2017 7:14 AM edge has replied

  
edge
Member (Idle past 935 days)
Posts: 4696
From: Colorado, USA
Joined: 01-09-2002


Message 223 of 224 (822083)
10-18-2017 9:42 PM
Reply to: Message 222 by Pressie
10-17-2017 7:14 AM


Re: What I expect from Walther's Law for Delta Formations
In my country, very similar, except that it happend in a fresh water environment with a big freshwater lake in the middle and that the coal deposits were formed during the Late Carboniferous (few lenses) , the Permian (most of the coal) and Early Triassic (big, "coaly" deposits such as the Waterberg coal).

I think that in most places the waters are fresh to brackish. These are mostly swamps and if no one is intercepting the surface and groundwater flow they should be more or less fresh. The Everglades in Florida would be an example where the flows are of fresh water to the south. In that case, however, we are getting salt water incursion into the water table.

This goes back to the delta question where we have fresh water flowing into the ocean to some degree. The Amazon supposedly forms brackish zones far into the Atlantic Ocean, particularly at the surface. I haven't tried to drink it...

I think someone mentioned the Amazon delta. The curious thing is that it is so small...


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