Gulf of Mexico numerous bays and smaller inlets. A number of rivers empty into the gulf, most notably the Mississippi River and Rio Grande in the northern gulf, and the Grijalva and Usumacinta rivers in the southern gulf. The land that forms the gulf's coast, including many long, narrow barrier islands, is almost uniformly low-lying and is characterized by marshes and swamps as well as stretches of sandy beach. The Gulf of Mexico is an excellent example of a passive margin. The continental shelf is quite wide at most points along the coast, most notably at the Florida and Yucatán Peninsulas. The shelf
Gulf of Mexico basin shallow-marine siliciclastics; eventually sediments grade into the Cretaceous carbonates, evaporites, and chalks. More recently, the Laramide Orogeny and consequential uplift of the Rocky Mountains, which led to increased sediments flooding the gulf, is responsible for the rapid loading and burial of the Wilcox Formation (pg 43), which is one of the deepwater Gulf of Mexico formations currently being exploited for hydrocarbons. This rapid loading is also responsible for the first salt flows from beneath the basin-margin region towards the continental slope. Gulf of Mexico basin The formation of the Gulf of Mexico, an oceanic rift basin located between North America