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Daniele

Stratigrafy - 2 strata with same order value

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Hy,

I'm insterested in create a stratigrafy model with the following formation:

- asfalt

- agriculture soil

- aquifer (sand)

- aquitard (clay)

Asfalt and agriculture soil have same order value because in same boreholes I've only asfalt while in the others I've only agriculture soil.

How can I set up Rockworks to deal with this?

Thanks

DLattuada

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Hi Daniele,

Each unit must have a different order value. If there are boreholes in which ALL units exist, use that order. For example, the Strat Types table might look like this:

asfalt 1

agriculture soil 2

aquifer (sand) 3

aquitard (clay) 4

It's ok for units to be missing from the boreholes themselves:

0.0 0.5 asfalt

0.5 5.0 aquifer (sand)

5.0 8.5 aquitard (clay)

or

0.0 1.5 agricultural soil

1.5 6.2 aquifer (sand)

6.2 9.0 aquitard (clay)

if you want to pinch units out, you can set them to have zero thickness:

0.0 0.0 asfalt

0.0 1.5 agricultural soil

1.5 6.2 aquifer (sand)

6.2 9.0 aquitard (clay)

There's a topic in the Help messages about 'missing formations' which might be helpful.

If you have data-specific questions, feel free to email me directly.

Molly Mayfield

RockWare Inc

[email protected]

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So, according with the order listed below, I could insert these stratigrafy:

0.0 0.5 asfalt

0.5 0.5 agricultural soil

0.5 5.0 aquifer (sand)

5.0 8.5 aquitard (clay)

or

0.0 0.0 asfalt

0.0 1.5 agricultural soil

1.5 6.2 aquifer (sand)

6.2 9.0 aquitard (clay)

Thanks,

DLattuada

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Yes - exactly. The zero-thickness intervals offer the additional control points for the program to use when interpolating the location of the surfaces for the top and base of the units.

Molly

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concerning the order value of soil, I have questions.

In my case, rock type 1 were found above and/or below rock type 2 in different boreholes

e.g.

Borehole 1

0 1 Fill

1 2 Marine Deposit

2 3 Bedrock (Granite)

3 Bedrock (Tuff)

Borehole 2

0 2 Fill

2 3 Marine Deposit

3 5 Bedrock (Tuff)

5 Bedrock (Granite)

what should be their order value?

when froming the Stratigraphy Model, how can I select both rock type 1 and rock type 2 be the possible Strat Unit for Baseplate?

and what would be the problem of having the same order value for 2 rock types?

Thanks

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Hi Gene,

RockWorks assumes a "layer cake" arrangement for Stratigraphy, so formations need to be in the same order across the project. (They can be missing, but they can't cross.) Since RockWorks uses surfaces for modeling stratigraphic tops and bases, it cannot be used for complicated geology where faults and folds result in the same formation occuring twice in a borehole or a unit being split into sub-units, etc.

That said, the Order definition is mostly used if you turn on the "Onlap" option, which tells RockWorks how to build a stratigraphic model from the oldest (lowest) formations upward, or the BasePlate option, which sets the base of a specified stratum to a specified elevation.

If you set the Order in the Stratigraphy Types table to

Fill = 1

Marine Deposit = 2

Bedrock (Granite) = 3

Bedrock (Tuff) = 4

with Onlap and Baseplate off, then you'll probably just get surfaces that cross, with blank spaces in the middle. The attached image shows an example.

If you set the Order to:

Fill = 1

Marine Deposit = 2

Bedrock (Granite) = 3

Bedrock (Tuff) = 4

Bedrock (Granite 2) = 5

you can distinguish the lower granite as a "sub-unit" in those holes where it exists below the Tuff. Be sure to add control to adjacent holes for any units which need to pinch out. See the other attached example.

The Baseplate can only be used for a single formation, so my second option would be the best bet.

It might also be good to ask what it is that you're most interested in... the bedrock structure or the depositional? Computing volumes of all?

For areas where the materials are not consistent in order (formations not well defined), you could enter the data as Lithology. Lithology modeling does not use surface but solid modeling techniques.

Without knowing more about the geology of your area and what, specifically, you wish to do, it's hard to offer more advice. Feel free to email me your data and descriptive details if you need more information.

Molly Mayfield

RockWare Inc.

post-3-1260822090227_thumb.jpg

post-3-12608221159315_thumb.jpg

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