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Scientific Drilling Concludes in the Gulf of California Adapted from Information by the JOIDES Resolution Science Operator The JOIDES Resolution is a scientific drilling ship used by the International Ocean Discovery Program (IODP) to drill into the ocean floor to collect and study core samples. One of its latest journeys was for Expedition 385 where it drilled at a new site - Octopus Mound. Also known as Central Seep, the mound is a cold methane seep located in Guaymas Basin in the Gulf of California. There, a group of scientists will study the relationship of tecton- ics, magmatism, sedimentation, carbon cycling, and potential microbial life, as well as the fauna and animals thriving around the methane-rich mound. Magma forms in the upper mantle through seafloor spreading. This project examined the very young spreading system of the Pacific and North American tec- tonic plates, where new seafloor is being created. However, in this system, sediments are being deposited on the seafloor very quickly, causing the magma to become trapped under 1600-1900 feet of organic-rich marine sediments. These isolated pockets of hot magma eventually move sideways and solidify into hot layers of intrusive magma rock called sills. These sills become interlayered with the sediments. At a safe distance of three miles from the potentially explosive mound, the team drilled into a shallow gas-rich zone, presumably with methane hydrates not far below the surface. Although this is a cold seep site, the high heat flow of Guaymas Basin was instantly noticeable, something a proper cold seep wouldn’t do. Drilling could reveal a clue to the answer. The drilling team decided to use rotary core barrel drilling (RCB), known for its raw power and speed, to exam- ine the underground conditions. A tungsten carbide bit was used to chew through the extremely hard sediments and rock, saving only the central core. Immediately after core recovery, methane and light alkane levels were checked. As the team drilled deeper, they knew increased gas concentrations were possible, making these safety checks a crucial part of the process. At just over 1174 feet below the seafloor, the drill crew discovered Octopus Mound’s little secret, it’s sitting on top of a very deep sill. The recovered core sample was stunning and the crew was excited to see such a good quality, textbook sample of drilled volcanic rock fresh from the borehole. In the end, more than 750 cores were extracted. With a recovery rate of 88%, scientists have over 13,550 feet of recovered cores to study. The core description team worked feverishly to identify the cores, while the labs revved up for scientists to conduct their exami- nations. Site reports will have to go through two review cycles by the expe- dition cochiefs, Professor Andreas Teske from the Department of Marine Sciences at the University of North Ca r o l i na -Chape l H i l l and Dan i e l Lizarralde associate scientist from the Department of Geology and Geophysics a t Wo o d s Ho l e Oc e a n o g r a p h i c Institution. Then, the IODP publications office will review the reports. 20 FEBRUARY 2020 WorldWide Drilling Resource ® ENV