14 December 2012

Friday fold: the folded xenoliths of Duck Creek

Posted by Callan Bentley

On Duck Creek (Ellendale, NC quadrangle), you can see folded xenoliths within the Toluca Granite (383 Ma, 378 Ma, or 368 Ma, depending on which mineral you ask).

The granite there contains xenoliths that contain pre-exisiting fabrics and structures, and we stopped at Duck Creek on the pre-GSA-Charlotte field trip I took to the Neoacadian Inner Piedmont to check out these xenoliths.

Here are some less impressive xenoliths, strung out parallel to foliation within the Toluca Granite:

This was the showpiece of the stop:

Our trip leaders Arthur Merschat and Bob Hatcher claimed an S1 and S2 foliation visible here, and an F1 fold hinge that was overprinted by the F2 fold hinges, but I’m not convinced I can make out two unambiguous generations… And the ones I picked as F1 (like the isoclinal fold in the large central xenolith) are different from the ones they picked: that’s labeled as “F2” on page 203 of the field trip guide… Hmph. Regardless, here’s some annotation for you:

We didn’t discuss the cuspate-lobate features at upper center at all. In fact, I’m ashamed to say I didn’t even notice them while I was at the site – only spotted them when I was working up the photo for this post. Shame on me.

Here’s trip leader Arthur Merschat checking out this outcrop:

Happy Friday!