From the NYRB's review of the current Garcia Marquez bio:
García Márquez popularized the style, but he was not its inventor, and One Hundred Years of Solitude would not have been possible without his hav- ing studied, at Carlos Fuentes's urging, the works of an older generation of Spanish-American writers who were magic realism's pioneers, among them Alejo Carpentier and Miguel Asturias. It is remarkable that so little influence on his writing is credited to his Latin American precursors. This is partly because García Márquez himself has been reluctant to give them their due. At times he seems to enjoy casting himself as the magician who created a new Spanish-American literature out of thin air.
The footnote embedded in the paragraph informs us that
The Cuban novelist Alejo Carpentier coined the term— lo real maravilloso—in 1949 to describe what he thought of as his variation on French Surrealism. Miguel Angel Asturias's phantasmagoric novel about a dictator, El Señor Presidente (1946), was the prototype for García Márquez's The Autumn of the Patriarch. In 1967, Asturias, a Guatemalan, became the first Latin American novelist to be awarded the Nobel Prize. García Márquez was awarded the prize in 1982.
Read Alejo Carpentier.