I - and several other Gravel family researchers - have been trying to answer your question for ten years. We have never found Joseph Wark's or Marguerite Gravel's parents.
I can tell you that John Wark married Marguerite Gravel on 15 January 1787 at St. Andrew's Presbyterian Church, Williamstown, Glengarry County, Ontario. Sources: Registers of Reverend John Bethume, St. Andrews Presbyterian Church, Williamstown, Glengarry County, Ontario; page XII [but also says page 13]; original records in the Public Archives, Toronto; photostats by the Public Archives Department, Ottawa; available on LDS FHL microfilm #0272356 (gives date and place of marriage but no parents' names; lists groom as "John Wark of Montreal"); see also Fraser & Ross, Register of Baptisms [&] Marriages for St. Andrews Presbyterian Church, Williamstown, Ontario for 1779-1804; Lancaster, Ontario, Alex W. Fraser, 1999; available at the Library of Congress, Local History and Genealogy Room, call number CS88.W52F73 (1999) (record says "John Wark of Montreal was married to Marguerite Grasell on the 15th of January 1787").
I know of two other children of this couple: Francois Wark who married Louise Thouin on 10 Feb 1823 at Ste. Rose Catholic Church in Laval, Quebec; and, Angelique Wark who married Pierre Paquet on 18 Feb 1822, also at Ste. Rose.
Hopefully, someone who sees your inquiry will have the answer you seek.