Geologic Archives of Climate Drivers in the South Pacific

Yesterday witnessed our most recent excursion to Rumbling Gut cave, Waitomo, as part of the Australian Research Council funded Discovery Project “South Pacific and Australian hydroclimatic history recorded by stalagmite calcite fabrics“, being led by Silvia Frisia of the University of Newcastle, NSW. Adam is co-investigator on this project with Silvia Frisia and John Hellstrom (University of Melbourne), and is co-supervising the PhD research of Ebony Anderson.

PhD candidate Ebony Anderson of the University of Newcastle, Australia

Ebony visited us for the purposes of completing the routine monitoring of dripwater and cave carbon dioxide levels as part of this project. The unique angle that Ebony is investigating, is the ability of carbonate fabrics (i.e., texture) in stalagmites to be used as a direct climate proxy. One focus of the research is to establish relationships between calcite crystallization, natural organic matter (NOM) and tiny particles (known as colloids) dissolved in the cave dripwater.  In fact, the pathways by which carbonate crystals form are believed to influence the incorporation of trace elements and the resulting fabrics, whereby “equilibrium” incorporation may not hold true, because “non-classical” nucleation pathways influence trace element content in speleothem crystals. Ebony is pictured above carrying out an “instant precipitation” experiment with cave dripwater, in which crystals nucleate in the presence of colloids and NOM in the water and are captured on the surface of a small carbon-coated copper grid, which is then used to visualise the crystals using a powerful microscope.

We made use of our time in Rumbling Gut constructively, getting very muddy and practiced our caving technique by exiting via the very tight “Hurricane Hole” entrance. Due credit to Ebony, who made the journey four times. Some of us had a little more trouble than Ebony fitting through the squeezes, but all enjoyed the daylight on the other side.

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Cheers for now,

Adam (U Waikato, 21 Feb 2017)

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