The Story is in the Sediments . . . Show Me the Evidence

Time Seismic Section Images the ocean floor using acoustic impedance contrast.
The running group is all smiles in front of the marina.

Participants of School of Rock 2019 benefit from the easy access to downtown San Diego. This eclectic backdrop provides an opportunity to explore the local culture as we wait for the return of the JOIDES Resolution. Our learning spills out past the official 9 to 5 coursework as we visit different neighborhoods and explore the region. This morning, a small group joined a running tour of the marina and Little Italy. We made our way along the shorefront taking note of the decommissioned aircraft carrier USS Midway, the tall ship Star of India, the Soviet submarine B-39 as well as many historic businesses in Little Italy.

SOR student contemplate drill site locations.


Back in the classroom at the Scripps Laboratory in Vaughan Hall, Dr. Norris challenged our cohort to determine the best drilling sites along the route used by Expedition 342 which circled the sediment drifts offshore of Newfoundland, Canada.  Drilling vessels are expensive operations and need to focus their time and efforts on optimal drilling sites. In order to select these locations, scientists often use technologies such as Time Seismic Sections. These detailed diagrams are two-way time graphs depicting the acoustic impedance contrast of sound through sediments. In other words, these images are created with loud blasts from the airgun towed behind the ship. The reflection of these sound waves off of the different layers create useful imaging of the sediment deposits below the surface. Armed with our images, we searched for sediment facies that best fit the desired criteria: corresponding with other Eocene aged deposits, occurring in shallow waters, and having minimal sediments covering it. We then matched our optimum drilling site to a bathymetric chart pinpointing the exact drilling site. 

Notice the abundant Discoasters in the smear slide.
Timescale highlighting the evolution of the extinct genus Discoaster.


Shifting gears after a lovely lunch overlooking the expansive Pacific Ocean, we turned our fine focus towards equally as interesting microfossils. These fossilized plankton indicate the age of the seafloor sediments in which they are found. We examined both our own hand made smear slides and prepared slides. These  discoasters (think 1970’s dance moves) are ideal for determining the age of a sample because of their distinct evolution. The sample seen in the picture below displays Discoaster brouweri which indicates that this sample is from the Pliocene. Being able to determine the age of a sediment deposit using the microfossil deposit is essential in telling a more complete sequential story.   


Dr. Norris illustrating the drilling process.

After multiple days in the field using large scale geologic structures and macrofossils to interpret the story of Southern California’s geologic history, it was compelling to work first hand with these fossilized microscopic Discoasters. These seemingly invisible organisms provide a reliable timeline of Earth’s history. Trapped in seafloor sediments and preserved for over 50 million years, their presence clearly chronicles the past. It is the objective of the JOIDES Resolution team to locate and expose these mini historians and interpret the story they reveal.   


Modern technology connects land based classrooms with real-time research taking place on the JR.

We ended the day with the reason we were all gathered in San Diego with a video conference ship to shore discussion with instructors, Kaatje and Leah aboard the JOIDES Resolution. Currently, research vessel is hosting the inaugural JR Academy consisting of twelve undergraduate students on Expedition 385T. This particular voyage is focused on testing new equipment and looking at old drill holes. As part of the program, the students are tasked with two projects while on board. The first project had students utilize JR datasets as a catalyst for individual research projects. The second objective emphasized the importance of science communication piece. The college students are video conferencing from ship to shore with other students in a land-based classroom.  These video conferences include opportunities for students to practice their communication skills while providing a window into ship life.

Written by: Dawn Adams and Erica Wallstrom (Educators from Rutland City Public Schools in Rutland, VT)

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