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The older the sediments, the more macho the equipment. Do you want to core a thousand years of salt marsh sediments? Just bring your hand auger and a gouge. And some muscle power, and a willingness to get really close to the muddy side of science. Do you want to core through interglacial sediments? That might not be so easy. As the name “interglacial” already suggests; these sediments are quite likely to be wedged between glacial sediments. And these may very well consist of gravelly stuff that’s awful to core through. If you need to drill through these to get to the sediments of your choice, bring at least a road drill. The percussive force of the drill will break through all the pesky flints you might encounter below. And a core barrel that’s rammed down with such force won’t be easily pulled out, so a big sturdy jack system is needed to pull the barrel up through the sucking mud and obstructing gravel.
A set-up like that can take you through many metres of unforgiving sediment, but there are limits to it. We know that because we tried it. If the core barrel is stuck, you have to pull the levers of the jack with all the power you can muster, but you might find what that results in is that you push the jack into the ground, rather than pull the barrel up. You might add some solid wooden beams to place under the jack to stop it from sinking into the ground; that will just break them. We tried that too! So there is a moment when you have to upgrade from the road drill. And the next step up is quite a step. The next step up is a drill rig. We had pushed the limits of the road drill set-up in the hunt for our iGlass interglacial sediments. So we had to take the next step. Fortunately, we had expected that, and there was budget for it.
The difference between a road drill and a drill rig is mainly the size. Another difference is that if you rent it, you get people to work it with that. So from struggling through brambles and barbed wire to get to a muddy field where we had to do everything physically possible to not lose the core barrel underground, we were suddenly upgraded to overseers who watch other people get muddy and achy and tired. And these muddy, achy and tired people would give us what we couldn’t possibly get ourselves: wide, intact sediment cores, all the way through the interglacial sediments to whatever lies below. And they delivered!
It was in rural Norfolk we got to meet our drillers. They arrived in a Land Rover with the rig as a trailer behind it. We asked them to set it up at Horse Fen, one of our critical field sites, where we had not been able to core the lower contact of the interglacial sediments. We had to set up at some distance from the old drill holes, in order no not disturb our badger neighbours. So the men erected the quadripod, hammered metres of casing into the ground, and started drilling through the glacial sands on top of our interglacial clays. These we don’t need for our research, so we just chucked these away. That saves time. They drilled down to where we expected the clay to start. And they drilled deeper. And deeper. We started to get worried. By the time we were wondering if they were drilling into an entirely glacial succession we hit the clay. The stratigraphy is very laterally variable in this area! We cored and retrieved the clay, which was a lot thicker than we expected, and finally hit the freshwater peats. And then the rig did what we had hired it for: it drilled through these. We knew we had a beautiful, undisturbed contact in our core liner. What would we find below? That was something we would not know until we got to the lab!
Over the coming weeks we will introduce members of each team working on the iGlass consortium project. Today we will introduce the members based at the University of York.
Prof. W. Roland Gehrels
Roland Gehrels is a Quaternary geologist and a physical geographer who specialises in sea-level studies. He was appointed as a Chair in Physical Geography in York in June 2013. Prior to coming to York he was at Plymouth University for almost 18 years, starting as a lecturer and going through several promotions until he was awarded a Chair in 2007. At Plymouth he was a member of the Quaternary Environments Research Group and headed a small research cluster in sea-level studies. Before that, he worked as a postdoctoral researcher at the University of Durham with Ian Shennan. His PhD at the University of Maine (USA) investigated Holocene sea-level changes in the Gulf of Maine and was supervised by Dan Belknap and Joe Kelley. His first endeavours in sea-level studies were in collaboration with the late Orson van de Plassche at the Vrije Universiteit in Amsterdam where he completed an MSc in Applied Quaternary Geology.
Dr. Margot H. Saher
Margot Saher is a palaeoclimatologist specialized in foraminifera, who has been applying the study of these micro-organisms to sea-level research for the past four years. She has been working on the iGlass project since 2009; first at the University of Plymouth (which later renamed itself Plymouth University) and since June 2013 at the University of York. This was her second sea level related project; before iGlass she studied sea-level variability over the last 500 years in the North Atlantic. She has also studied benthic foraminifera ecology in the Barents Sea in relation to anthropogenic warming; this took place at the Norwegian Polar Institute in Tromsø. She received her education (MSc and PhD) at the Vrije Universiteit in Amsterdam, working with Dick Kroon and Simon Jung.