Caves, lakes, and automobiles… and a helicopter!- Fieldwork in New Zealand’s South Island.

Andrew Pearson, March 2016

Welcome to my first blog post for Waikato Environmental Geochemistry, in which I’ll be relaying the activities of our recent fieldwork in New Zealand’s South Island.

In February, 2016 Adam and I visited three caves, Hodges Creek in Mt. Arthur region, Kahuranghi National Park, Nelson, and ‘Calcite cave’ and ‘Dave’s cave’ atop Mt. Luxmore in Fjordland National Park, Southland. I was extremely excited to see the sites where the speleothem samples (that are at the focus of my PhD project) were collected. I was also able to visit lake Ohau (Canterbury), to see the mind-blowingly cool Lake Ohau Climate History project in action.

Hodges Creek, Mt. Arthur

Our trip began with a Kiwi Regional Air flight (thoroughly recommended- complimentary Tim-Tam biscuit!) to Nelson from Hamilton, and the next day our journey to Hodge Creek cave commenced.

After leaving the Mt. Arthur hut track, we ascended the slopes of Mt. Arthur, competing with obstacles including abundant vegetation, the varying topography of the karst landscape, and in Adam’s case; the numerous wasps that attacked his leg. Nevertheless, after 5-6 hours we made it to a rock-shelter, where we made camp. We entered the cave that evening and collected drip-loggers that were deposited 12 months ago, and will provide important hydrological information. We also left bottles to collect water samples beneath active drip-points. The chemical composition of these water samples will be compared with that of the speleothems, and the soil above the cave, to give information on geochemical changes through the system.

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Adam & the Marsden Fund flag inside Hodges Creek.

After deployment of the bottles, we camped for two nights, enabling enough time for the bottles to fill. Once the bottles were collected, we moved on to Fjordland (via Dunedin).

Calcite cave and Dave’s cave, Mt. Luxmore

After another tough hike (this time along the Kepler track), we set up camp atop Mt. Luxmore, and immediately set to work in calcite cave (once we located the caves in amongst the tussock). The bottles were deposited in Calcite cave (my favourite cave thus far), and last years’ drip-loggers were collected. After camping for one night, we descended, and spent the next couple of days recovering from our hiking and waiting for the water samples to collect.

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Speleothems inside Calcite cave, featuring a bottle fixed upon a tripod, collecting a water sample from an active drip-point (bottom-right).

After much thought, it was decided that rather than ascend and descend Mt. Luxmore, and collect our samples from Calcite cave and Dave’s cave in just one day, it would be safer and more feasible to travel via helicopter from Manapouri to the landing point at Luxmore Hut (just several hundred metres from the caves). One of the reasons the caves at Mt. Luxmore were selected, is because the lack of human influence and pristine conditions, and this was evident in our helicopter commute. This was my first trip in a helicopter, and surely there aren’t many better places in the world for it.

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(Left & centre) Stunning scenery on the helicopter journey from Manapouri to the Luxmore hut. (Right) Helicopter departing after drop-off.

Lake Ohau

Upon completion of our cave-based fieldwork, Adam returned to Waikato, whilst I travelled north to lake Ohau. The Lake Ohau Climate History project (LOCH) is a collaboration between numerous research institutes and universities (see link to more information at bottom of post), and involves sampling up to 80m of sediment (mud) from the bottom of lake Ohau. The lake sediments are known to contain annual laminations of deposition, and these laminations vary in numerous aspects, including sediment grain-size, colour and density, and therefore provide a detailed archive of the local/regional climate since the lake was glaciated (approx. 17,000 years ago).

The lake coring took a while to commence, as setting the rig and coring system in the required position is a difficult task (even for a professional drilling team!), which becomes an impossible task in high-winds (Ohau means ‘windy place’). Once the wind settled and the coring began, the speed at which the drill-team worked was hugely impressive, with 3m of sediment being removed hourly, 24 hours per day. Upon retrieval, the samples were logged, and transported to shore, where they underwent preliminary analysis using a veterinary x-ray (to check the quality of the sediment), before being stored in a large cooler.

This project was fascinating to me, in terms of the subject matter, but also because it provided an insight into the complexities and immense amount of planning and preparation required to ensure the success of a large operation.

 

Ohau

(Left) One of the perks of starting a shift at 06.30 am is witnessing the sunrise above Ohau canal. (Right)- Lake Ohau (I would have liked to have taken a picture of the coring system in action, but my camera had run out of battery at my only opportunity- D’oh!)

More information on LOCH: (http://www.gns.cri.nz/DrillNZ/Lake-Coring/Lake-Ohau-Climate-History).

If it wasn’t really clear, I loved my 3 weeks of fieldwork, but I’m glad to be back at Waikato and am ready to tackle some lab-work (even though it won’t be quite as photogenic).

Thanks to Adam for organising the fieldwork, and to Marcus Vandergoes at GNS for inviting me to see the LOCH project.

Cheers for reading,

Andrew Pearson

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