7 weeks 4 days
Meet the Paleo team!
Submitted by Exp 350 Paleo on Fri, 05/23/2014 - 10:01
The “paleo” on JR is a small team of 6 scientists working together to date the sediments and rocks recovered day and night to address a specific scientific question. Here, the “Crustal Evolution of the IZU back-arc.”
They have to work swiftly and flexibly at the same time as drilling operations proceed. Sometimes, when operations stop or slow down during casing or when the drill bit needs to be changed, they have more time to catch up with some less pressing samples and to report on their findings.
On Expedition 350 the Paleo group counts:
4 micropaleontologists: Zack Kita (US), Eleanor John (UK & Fidji), Manuela Bordiga(Sweden) and Maryline Vautravers (UK). Zack and Manuela are experts in nannofossils (tiny dust-size unicellular algae) and Eleanor and Maryline are mastering the foraminifers (sand-size micro-organism with a calcareous shell).
2 paleomagnetists: Myriam Kars (Japan) and Bob Musgrave (AUS) measure the magnetic properties recorded in each core to reconstruct the “Earth palaeomagnetic field.”
Like everybody here they work in 12 hours shifts. Zack, Eleanor and Myriam work during the night; Manuela, Maryline and Bob work during the day.
Depending on the needs of any IODP expedition (linked to the location) the group can also include an expert in another microfossil group, e.g. diatoms or dinoflagellates (microscopic siliceous/organic planktonic algae).
Their work follows an almost inflexible pattern:
As soon as a core arrives on deck, even before it is cut in the laboratory, measured or even labelled, the paleontologists will have the privilege to get a first sample from the core catcher (at the bottom of each 9 m long core) delivered out of the hole.
Helmet and glasses on, one of them is ready to collect a precious sample, quickly bringing it back to the paleontology preparation room. Excitement is visible on the faces. They will get a first and special glimpse into what has just been recovered. More precisely they will find out about the core age or in some cases see the problems preventing them from estimating this age. This has happened during Exp 350 and there have been times when they could not say. Because deep in the IZU back-arc (>600 m) the nature of the rocks made identification of microfossils very tricky.
The nannofossils expert strikes first:
Within minutes of the core being received, Manuela/ Zack will have made one simple smear slide using a very small sediment piece, a toothpick and a drop of water between 2 glass slides. They are looking for the tiniest yet the most abundant microfossils of all: the nannofossils (needs a *1000 magnification to be seen).
Meanwhile, Maryline/Eleanor have to wait a bit longer to study their samples, at least a few hours and at most 2 days.
For the fresh mud samples (not compacted and not lithified), a sieve and a water spay used to remove the clay, leaving behind the foraminifers and other large particles will be all it takes before drying and study under the microscope (at only * 20-50 magnification).
More compacted to lightly lithified samples need a few hours in hydrogen peroxide and the lithified mudstone recovered even deeper in the back arc get a harsh kerosene and boiling water treatment over 2 days to force them to release their microfossils.
Put simply, both the nannofossils and foraminifers experts are looking for species appearances and disappearances from the fossil record as evolution (recorded in changing appearance of the shells) goes on for each group of species. They call the times when they see these events happening: Datum.
Datum have known ages because they have been observed in numerous studies including from the sediments and rocks collected by IODP and its predecessors over 45 years. Their ages have been calibrated by other dating methods also.
Datum Ages and Depths at the drilled site can be plotted: The first tentative biostratigraphy of a site is born.
Meanwhile, because scientists like to cross check findings and not to rely just on one set of evidence, our 2 paleomagnetists on board, Myriam and Bob Musgrave are looking for magnetic reversals of the Earth’s magnetic field.
At the present time, the Earth's magnetic field is considered to be ‘normal’ with the North Pole of the magnetic field at the North and the South Pole at the South. Good, but it wasn’t always like this. Due to changes in Earth's outer core affecting the convection of liquid currents, the magnetic field can ‘flip’ and it has done so many times over geological time. Intervals when the field was not as it is now are called reversed. These flips in the field have been well documented and dated, so our cores can be compared to a known sequence.
So, guess what? Paleomagnetists also provide Datum from comparing our cores to this sequence of reference and these datum too can be plotted on and age /depth profile.
A bit later….
Discussions, meetings, cross checking a few times and finally the question.
Will they all agree on dates or not?
On this trip, the magnetic dates and the fossil dates work well together. Well done!
Just short of 10 million years down to c.1500 m below sea floor.