Fieldwork and Cruises

Tarawa 2004/2005. We had two field expeditions to Tarawa Atoll in the central Pacific in 2004/2005 to core Holocene reefs to collect fossil banded corals for ENSO reconstructions. The purpose of the project is to determine how ENSO frequency and intensity changes during the Holocene and if these changes are tied to changes in the Earth.s precessional radiation cycle as some models suggest. The first field trip sited the drill sites, arranged permits and personnel, and cored surface corals for calibration purposes and to extend the recent proxy record of ENSO signal using the oxygen isotope proxy. The first trip was manned by Columbia undergraduate students. The drill cores recently arrived at Lamont and graduate student Jacob Mey is preparing the samples to measure the oxygen and carbon isotopes. In addition, Jocob is in the process of age dating the longer cores by 230Th/234U/238U dating technique.

Barbados 2004/2005. As part of our offshore coring program designed to recover the sea level history of the last glaciation and earlier we cored offshore Barbados in 2004 and will return in 2005 on a ship of opportunity to core the near shore fossil reefs. We expect to recover corals dating back to 70,000 years old in the shallower core site planned for the summer of 2005. In April of 2005, Fairbanks. Isotope Geology II class did a five-day field tip to Barbados where they researched Pleistocene sea level history and studied the diagenesis of carbonate minerals in this classic setting. In addition, the class researched speleothems formation and chemistry in the karstic region of the island.

Araki 2004/2005. In 2004 we carried out a very successful sampling expedition to Araki Island with Columbia University undergraduates for the purpose of collecting additional coral specimens for our radiocarbon calibration project as well as a cooperative sea level study with Art Bloom at Cornell University. Araki is part of the Vanuatu Island chain and is located in the southwest Pacific between Fiji and Australia. We will return to Araki Island and Vanuatu in the spring of 2005 to conduct additional sampling as part of the master.s thesis for Curtis Brainard, a student in our Journalism and Science program. Curtis is seeking to better resolve the timing of the Laschamp geomagnetic excursion that occurred around 40,000 years ago, a time when the Earth.s geomagnetic field collapsed. The brief weakening of the geomagnetic field caused a dramatic increase in the 14C content of the atmosphere. Models indicate that the atmospheric signal was probably quickly attenuated in the surface ocean but Araki coral samples close in age to the Laschamp should record this remarkable event.