The Detours series celebrates lesser-known locales worth visiting across the state. The oldest consecrated church on Mustang Island faces the Gulf of Mexico from high on a dune amid yellow camphor daisies, purple phlox, and swaying sea oats. Completed in 1938 in what is now Port Aransas’s historic Old Town neighborhood, Chapel on the Dunes was designed by San Antonio artist and writer Aline B. Carter as a place of worship near her beach cottage. It provided years of inspiration for Carter, who served as Texas’s poet laureate in the late forties. A few years after her death, in 1972, the Carter family authorized artist John Patrick Cobb to paint the structure’s roughly 250-square-foot interior; he covered the white walls with colorful, almost dreamlike biblical frescoes in…