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Geology Research Unit@TUC

Modelling stratigraphy. Problem with representing the actual structure of the geology.

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I have been trying to model an area that consists of 3 separate geological units. These units, from depth to top, are the metamorphic basement (named as Ypovathro at the stratigraphy legend) the unit of Viannos a sedimentary unit consisting of marls and sandstones with average thickness of 600 meters and finally the unit of Sxoinias a second sedimentary sequence of thick marls and sandstones. The data we had on hand were 7 boreholes of average depth of 1000meters and 6 Vertical Electric Soundings. From field observations we know that the basement unit appears on the surface at the northwest part of the study area. The unit of Sxoinias appears mostly at the East side of the study area and the unit of Viannos appears also on the surface at a large scale of the area. The first model was created with a baseplate at -600 meters which was the deepest depth the boreholes reached.Onlap was turned on. The initial stratigraphy model failed to show the basement as it appears in the northwest part.

The next model was created with onlap off and showed the basement at the expected areas. The next step was to create a stratigraphy model with the topography of the area. I followed the steps as described in the case study of Modelling Pinch outs and steep topography, but the model that occurred failed to interpret correct the succession of the formations at depth,especially between Viannos unit and Sxoinias unit. Also the basement appears at the observed area at the north west but in smaller scale than expected.

An hint on how i could deal with this problem ??

Thanks in advance, George

P.S I tried to upload an image of the model so you could see the problems i refer to,but it failed repeatedly.

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Do you have all units listed in all boreholes, to give the program the information necessary to pull the Basement surface up in the NW corner, to pinch out the Viannos in that area, and to allow the Sxionias to overlay the Viannos in the SE? You can set units to zero thickness in boreholes where they are not found to indicate where they should be pinched out.

For example, in the NW corner of the area, the boreholes might appear:

0 0 Sxoinias

0 0 Viannos

0 600 Ypovathro

(Note that I’m guessing with all of the depths here)

And in the middle, they might appear:

0 0 Sxoinias

0 200 Viannos

200 600 Ypovathro

While in the SE area they might appear:

0 200 Sxoinias

200 200 Viannos (zero thickness should be used if this unit pinches out here)

200 600 Ypovathro

For more details, it's helpful to see your actual data, along with the topographic grid model, so feel free to zip and email me your project folder. Please also send a separate email notifying me that you’ve emailed the ZIP so that I can watch for it and let you know if it does not arrive.


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