Clift’s Cruise By Dr. Peter Clift
At the end of March 2015, I left my office in Baton Rouge and headed off to Colombo, Sri Lanka, to begin my involvement in International Ocean Discovery Program (IODP) Expedition 355. IODP is an international organization, funded by the National Science Foundation and its international partners, and based out of College Station,Texas. IODP performs scientific drilling in deep ocean basins around the world based on proposals written by the international scientific community, including myself. I had been planning for these particular drilling activities since the late 1990s, so I was very excited that finally we were having the opportunity to take samples deep below the ocean floor in the Arabian Sea. In particular I wanted to take samples from the Indus submarine fan. This is the second largest sediment body in the world (around 5,000,000 kmÂł) and is believed to record the long-term erosion and development of the Western Himalayas whose, development is still strongly debated by geologists. This particular expedition was unusual in being partially funded by the Indian government; they contributed around $6 million to the total cost of $15 million. My job was to be the co-chief scientist.
I worked together with an Indian colleague making the decisions about when to start and stop drilling, as well as coordinating the writing of reports. We were joined in this endeavor by about 25 other scientists taken from all the member countries and spanning a wide range of expertise. On Easter Sunday we left the harbor of Colombo and headed first west and then north after rounding the southern tip of India until we were approximately 250 miles offshore Mumbai, India. All of our drilling took place within a subbasin of the area called Laxmi Basin. This structure was believed to have formed a little earlier than the rest of the Arabian Sea and possibly related to the emplacement of the Deccan Traps volcanic province. The Deccan is particularly famous as being one of the potential influences that caused the mass extinction at the end of the Cretaceous. As well as reconstructing the erosion of the mountains and attempting to link their development with the history of the Asian monsoon, we were also interested in investigating the origin of Laxmi Basin by drilling into the basalt which underlies the sediments.
Our ship, the JOIDES Resolution, was a converted oil industry drill ship adapted to undertake only scientific missions, something it has been doing since the late 1980s. Without a blowout preventer we were unable to cope with the presence of any hydrocarbons but instead focused entirely on coring. This process also provides us with the material that we will work on after our return to the shore. Because of the significant sediment thickness in this part of the Indian Ocean, locally in excess of 11 km, we only had time to drill at two locations, each of which penetrated around 1100 m below the seafloor. At the second of these locations, we managed to recover some basalt on the very last day of drilling. This allowed us to see that the basin had begun to open before the onset of the Deccan volcanics. Drilling was often rather complicated. We had significant problems keeping the hole open and stable so that we could reach our deep targets. Although studying sand is one of my great passions, this material makes problems for drilling in the subsurface. Until it is properly consolidated, it can flow and fall into the hole causing blockage and loss of the drill pipe, costing a lot of time and money in the process. At one point this happened to us; we were forced to blow off the end of the pipe using explosives in order to free ourselves. This is always a tough decision to make, especially after investing
Co-chief scientist Peter Clift (center) discusses the cores recovered during the previous shift with the sediment description team in the core laboratory on the JOIDES Resolution.
Co-chief scientist Dhananjai Pandey from the National Centre for Ocean & Antarctic Research, GOA, India (left), expedition project manager Denise Kulhanek from Texas A&M University (center), and Peter Clift (right) in the science office.
a lot of time and effort into making a deep hole. Generally speaking the weather was really good for drilling during our eight weeks at sea. We only had minor disruptions as a result of inquisitive fishermen, followed by a request from the Indian Navy for us to move so they could conduct a bombing practice. In the end both these groups left us alone to continue operations in peace. At the end of our journey, we recovered around 1600m of sediment, which will be stored in the repository in Japan, where I and other researchers will be able to access it for many years to come. One of the best things about undertaking scientific drilling is you often get surprised by the results. You begin to develop some humility about how much you really know
about how planet Earth works. One of the most dramatic results we had was to drill through a 300 m thick mass transport deposit that we dated to be late Miocene age, around 10 million years old. This deposit represented an enormous landslide, which seismic data shows us to be around 18,000 kmÂł in volume or around three times larger than the next largest such landslide on Earth, found off the shore of Norway. Although this was not our original objective, such a dramatic deposit demands attention and study. Already we know that this was released from the continental slope of India to the northwest of the drilling site and we believe that it flowed as much as 400 km from its source onto the deep floor of the nearby ocean. Study of the chemistry and minerals in the sediments
holds out the possibility of better understanding how the Asian monsoon has changed its intensity in the past; however, revealing this history will require detailed work in the laboratory, partly to be done here in Baton Rouge, as well as in collaborating laboratories around the world. One of our primary objectives is to test the idea that the Asian monsoon started to strengthen around 8 million years ago, a suggestion that I have battled against for many years now. Now at last we have the opportunity to test who is right, or indeed, whether any of us are correct in what we have believed up to this point. The expedition ended in Mumbai. There we were taken off the vessel in the middle of the harbor by a small water taxi. It was certainly good to get back to the shore and return to the world of fast Internet, cold beer, and something new to eat. While the facilities on the ship were very good and the food generally delicious, I’m sure I was not alone in being happy to be headed home. A little peace and quiet after an expedition that lasted nine weeks from door to door is exactly what I needed. LSU students will no doubt be working on the samples I collected for many years to come, hopefully in collaboration with many new friends that I’ve made across the country and around the world in the process.