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Thin Sections

Major evidence for a dinosaur-extincting meteor impact 65.5 million years ago. More here

Rob writes:

The sample is showing white Cretaceous followed by the KTB clay section and on top the white and slightly grey Tertiary rock.

The section is completely natural and un-treated. It was taken from the KTB at Stevens Klint cliff (photo 2) near to the Harbor of Rodvig, Denmark.

The method of extraction and preparation, as described by the geologist I purchased this from:

First, prepared the cliff wall such that the sample section I wanted was standing out from the wall. Then the wooden frame was put onto the outstanding rock and then gypsum was filled in between the frame and the rock and on the rock's outer side (which is now the back side covered with gypsum) while the rock was still not not loosened from the wall.

After the gypsum was solidified I broke away the complete frame with the sample from the cliff wall.

Wrapped the front side of the profile with Aluminum foil for protection and you might still find some small foil remanents on the surface. The plaster I used is gypsum and you can see it on the back side of the sample. The gypsum can be clearly distinguished from the natural rock.

For orientation of the sample please refer to the image with my comments:

Cretaceous is bright white almost without color variation and you will find high concentration of Foraminifera (micro animals) embeded.

The KTB section is brown, rusty and grey with tendency to dark in the upper part. The KTB section sometimes can also show areas where it is 'brecciated' and there the coloring can be reversed.

The cretaceous rock directly on the KTB section is typically consisting of several clearly visible thiner layers, variable and sometimes alternating in color (dark-brighter-dark ...) but with tendency to brown and bright, finally white again on the upper Tertiary side. (No such layering can be observed within the Cretaceous section).

Speres (microcrystites/microtectites) can be found in the KTB clay section more in the lower area (look in the rusty colored or dark area near to the bottom of KTB) but depending on brecciation sometimes can be also observed in the central area of the layer.

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