Orca Basin

The Orca Basin is a special underwater area in the northern Gulf of Mexico, about 300 km southwest of the Mississippi River mouth near Louisiana. It is different from other areas because it holds a large pool of very salty water without oxygen, called a brine pool. This pool covers about 123 km² and is up to 220 meters deep, sitting under 2,400 meters of ocean water. It formed when a lot of ancient salt, called Louann Salt, dissolved into seawater.

Scientists found something interesting in the Orca Basin during a research trip called Leg 96 of the Deep Sea Drilling Program. They discovered gas hydrates, which are ice-like structures that contain gas, in the mud samples they brought up from the deep sea. These hydrates looked like tiny white crystals and were found at depths of about 2,412 meters underwater.

The gas in these hydrates comes from tiny living things, as shown by special tests. Unlike other places where gas hydrates are found in the Gulf of Mexico, in the Orca Basin they were found inside the basin itself, not on the edges. The hydrates were found in layers of mud that contained organic material and a special type of rock called pyrite.

Importance of Orca Basin as a study site

The Orca Basin helps scientists learn about big changes in Earth's past, like when huge glaciers melted and sent water into the oceans. This basin has layers of mud and sand that tell stories about the environment and ocean conditions near the Mississippi River Delta for the last 25,000 years. By studying these layers, scientists can see how meltwater from old glaciers affected the Gulf of Mexico.

The Orca Basin is special because it is one of the few places in the Gulf of Mexico where scientists have found gas hydrates — ice-like structures that trap gas — deep under the sea. These hydrates are important because they show how salty the water was when they formed. The Orca Basin is a great place to study how tiny living things and minerals mix with seawater, helping us understand how nutrients and other materials move through the ocean.