Sec. 5. All mines and minerals, and the mineral rights including oil and gas are hereby specially reserved to the State under that part of said area described in Section 1, which has been filled, laid out and constructed for use by the City of Corpus Christi as streets, public drives, parks, boulevards, and seawall, and all minerals and mineral rights under the remainder of said land are hereby relinquished and released unto the City of Corpus Christi and its assigns.