The location is the Burren - A rocky area in North County Clare.
In relation to John Sweeney, there is a John Sweeney in the townland of Doonagore, Civil Parish of Killilagh in Griffith's Valuation taken c1850. He is a tennant and is joined with James Moloney in farming the land. His house and other land is in the same townland.
There is a Michael McCarthy in the townland of Ballysallagh which is also in the parish of Killilagh.
There is a family of "Sweeney's" recorded in the 1901 census in Doonagore.
I have checked for a birth record for "Mary Sweeney", but did not find any. Nothing for John Sweeney and Mary McCarthy.
I recommend that you check out the Genealogy Section of Clare County Library - www.clarelibrary.ie for further records in relation to the Burren area.