I am descended from Silas T. Bement of Croton Twp., MI. He was born 28 Dec 1822 and died 13 Dec 1902. He had a brother also named Silas who was born 30 Apr1818 and died very young on 6 Aug 1820. Perhaps the tombstone you found was his and it only showed the date of his death.
I have more information on Silas T. Bement and his descendents if you are interested. You might also check out the webpage that Dennis BeMent maintains at www.bementfamily.com. It has information on Mariam Bement Chesley and many, many other Bement family members.