 The ancestral Rio Grande progressively integrated basins to the south, reaching the Palomas basin by 4.5 million years  , the Mesilla basin by 3.1 million years, to Texas by 2.06 million years, and finally joining the Pecos River at 800,000 years to drain into the Gulf of Mexico.
<coherence>  The ancestral Rio Grande progressively integrated basins to the south, reaching the Palomas basin by 4.5 million years  , the Mesilla basin by 3.1 million years, to Texas by 2.06 million years, and finally joining the Pecos River at 800,000 years to drain into the Gulf of Mexico.
 The ancestral Rio Grande progressively integrated basins to the south, reaching the Palomas basin by 4.5 million years ago , the Mesilla basin by 3.1 million years, to Texas by 2.06 million years, and finally joining the Pecos River at 800,000 years to drain into the Gulf of Mexico.