No answers, but some suggestions:
They were there pretty early. They might have been buried on private land. Do you know where their farm was?
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One of their children, John E, is said to have died at Redstone, Fayette County. Can you find where he is buried? Was it a family plot? Where were the other children buried, if they died nearby?
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The Gibsons were Quaker. Were there Quaker cemeteries in the area that early? Is there a Quaker meeting house there now? Would they know where the Gibsons would have been buried?
http://www.quaker-chronicle.info/meetings.php?meetingID=142----
Fayette County genweb site:
parent site:
http://www.pagenweb.org/~fayette/cemeteries:
It looks like not all have been transcribed
http://www.pagenweb.org/~fayette/cemetery/index.htmlI site-searched
site:http://www.pagenweb.org/~fayette/cemetery/ Thomas Hannah Gibson
and didn't see anything that looked good, but it might be worth your while to look through the lists.
research_aids:
http://www.pagenweb.org/~fayette/research_aids/index.htmllibraries:
http://www.pagenweb.org/~fayette/research_aids/libraries.html---
I don't know if the site is currently active, there is a copyright 2019 on it, so maybe. Maybe someone there might be able to help.
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Along the way I found this. Bad OCR but you can tell what it is saying
XI HANNAH RING' I Nathaniel,- Nathaniel') dau. of Nathaniel and
Evdia (\'cnii)ni Ring, m. at Concord Meeting, Pa. 9 mo. 27, 1751,
THOMAS GIBSON (see Gibson family) against the cjuaint protest of his
mother which was overruled by the Meeting.*
* Minutes of Concord Monthly Meeting, 9 mo. 4, 17.i7, "Thomas Gibson and
Hannah Ring i)ropose marriage. His mother Christiana Harlan not being .satisfied,
a connuittee was appointed to wait on her, fmt she W(juid not give reasons, 'but that
she can't consent.'"
http://www.ebooksread.com/authors-eng/james-henry-lea/the-ancestry-and-posterity-of-john-lea-of-christian-malford-jae/page-36-the-ancestry-and-posterity-of-john-lea-of-christian-malford-jae.shtml