こんにちは！D2のYangerです！
I just got back from a field trip to Kikaijima with Professor Hirabayashi. Kikaijima is a small island in Kagoshima Prefecture, east of Amami. Besides being known for its sugar cane and sesame, the island is also famous for its uplifted coral reefs and was recently designated as a Japanese geopark. As we approached the island by air, we could clearly see the classic spur-and-groove formations of its coral reefs.
Our main mission this time was to survey limestone outcrops exposed during excavation for an underground dam. We were joined by Professor Marc Humblet from Nagoya University, an expert on coral and limestone assemblages. With his help, we identified fossils of corals, foraminifera, brachiopods, and other organisms preserved in the limestone. These fossils offered clues about the water depths and environments in which they originally lived. We even found a well-preserved barnacle fossil protruding from the rock face!
We spent two days at the site documenting and sampling the
specimens we found in the rock. After long days working under the sun, we were
rewarded with beautiful sunsets.
In addition to examining the outcrops, we also had the
chance to inspect rock cores collected before construction began. The cores
were stored in the gym of an old school, where rows upon rows of boxes filled
the space. As we examined the cores and identified sections containing corals,
foraminifera, and crustose coralline algae (CCA), we could trace how the
island's environment had changed over time.
On our final day, we drove around the island to sample
groundwater from springs. Professor Hirabayashi explained that our lab has been
regularly monitoring the geochemical composition of Kikaijima's groundwater for
several years. By using radiocarbon as a tracer, these measurements help us
understand how groundwater moves and changes beneath the island.
In just four days, I got a glimpse of the exciting research
being conducted on this coral island. A huge thank you to Professor Humblet for
helping us identify the various organisms preserved in the limestone and
explaining what they can tell us about the island's past environments. I'm also
very grateful to Professor Hirabayashi for organizing the trip and teaching me
so much about Kikaijima!
