I do not consider the 70's to be the age of R&B/Soul, it was the birth of Funk and the slap bass. The 60's were more about that sweet soul music with Atlantic, Chess, Epic, Motown and Stax.
James Brown, Otis Redding, Little Milton, Sam & Dave and Aretha formed that music that was only defined as Soul. The Four Tops, Temptations, Smokey Robinson, Marvin Gaye and Supremes founded what would be known as Blue Eyed Soul. It continued through the 70's but that wasn't it's shining glory because it became influenced by rock and out of necessity Funk was born.