Inside the curation container, Jody Webster peers into a transparent, cylindrical tube – a core liner holding the first official core of our expedition. After pulling up this meter and a half of rocks and sediment (from a depth of about 740 meters on top of the reef terrace) our geo technicians extracted it from the core barrel and handed it over to our scientists.
It’s just after 10 pm and even though we’ve been working all day, everyone is wide awake, buzzing with energy and excitement. Members of the science team take turns inspecting the core closely.
“We’re looking at what it’s composed of,” Webster explains. “We can see a mixture of different rock types. Basalt. Limestone fragments. And there are definitely some large fragments of fossilized corals.”
To Webster’s experienced eye, it’s easy to spot the genus Porites, a genus of stony coral that is very common on the modern reefs of Hawaii. In well-preserved samples, Porites can tell us about ancient sea surface temperatures.
“When we do more detailed analysis – when we cut into the cores – we might find some crevices or cavities where the original corallite surface has been preserved,” Webster says. A corallite is a skeletal cup, formed by an individual stony coral polyp.
“Of course, it doesn’t have any tissue. All the organics are gone but the fossil is still there.”
The coral specialists will look at the corallites under a microscope to examine its structural elements, including the size, shape, and arrangement and try to identify the species. Depending on the type of coral, the structure (skeleton) itself will look different. Some might look like mesh, while others might appear thicker.
Previous data suggest this reef is about 225,000 to 276,000 years old.
“It’s very exciting to actually recover a core from this terraced reef structure. It’s very useful but exactly how useful will depend on the final interpretation – whether the material is well-preserved enough for dating,” Webster says. “We’ll try do some of that during the mid-point of the cruise. We won’t know that until later.”
After he’s done with his visual examination, Webster takes some high-resolution photographs. In between the larger fragments and coral pieces, the pictures show some lithified hard carbonate sediment, as well as some carbonate grains scattered throughout the core.
“Some of those grains were bits of coral and algae, but we also spotted some larger benthic foraminifera,” Webster says. “I had a guess of what they were – a particular type of genus – but I wanted to get input from our onshore colleagues.”
Our science party includes 30 people with a wide range of disciplines and expertise. Due to limited berthing on the ship, we only have a small subset (nine people) here. Even though some members of the science team are thousands of miles and a dozen time zones away, we can still utilize their expertise.
Webster uploads the high-resolution photos to our Slack channel and posts a message:
We recovered some really interesting facies in the first core. Lots of LBF’s – see images? A species of Amphistegina?? It would be great to get your thoughts.
Willem Renema, Professor of Marine Palaeodiversity at the Institute for Biodiversity and Ecosystem Dynamics, is an expert in large benthic foraminifera. Over Slack, he confirms the genus and begins researching the exact species.
“Being able to communicate with an expert who isn’t here allows us to get extra information quickly – and that’s very valuable,” Webster says. “We’ll do that as much as possible as we continue with the expedition and try to maximize the science we can achieve.”
Blog of IODP Expedition 389: Hawaiian Drowned Reefs 
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