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CraigHyatt

Cretaceous-Paleogene Boundary ID

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CraigHyatt

I live in Eagle Pass, TX and I've been working a construction site near my house. This is a beautiful site, because there's an excavated wall with several ramps that's perhaps 10 m high (guessing from memory). I can see very clear strata that run perhaps 50 m along the wall.

I've been surveying this wall, and one objective is getting a clear idea of the dates associated with the various layers. This part of Texas is generally Late Cretaceous and was a marine environment.

My question is whether there's any decisive way to identify the Cretaceous-Paleogene boundary. Supposedly, there's a change in color at the boundary. I suppose there would also be a change in the animal and plant life above and below the boundary.

The most evident thing I see is that the lower parts of this site are grey soft clay and some hard shale. This section is riddled with bore holes and not much else. Above this grey layer is soft sand stone and even beach sand with some layers of harder sandstone, shale, and solid rock. The upper section has mostly sea shells. I've only found one ammonite, a sphenodiscus, at this site.

Locating the K-Pg boundary would be a big help to get me oriented. Any suggestions appreciated.

Edited by CraigHyatt

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JohnJ

The PDF link in this post should help you figure out the strata you are seeing. Bear in mind that all of the features you are seeing can be evident in a single formation, and some formations are, locally, many feet thick.

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CraigHyatt

The PDF link in this post should help you figure out the strata you are seeing. Bear in mind that all of the features you are seeing can be evident in a single formation, and some formations are, locally, many feet thick.

John,

Thanks! For some reason I couldn't get it to download the other night, but it worked just now. Looks great!

-Craig

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