News from the Sessions Research Group

Congratulations Dr. Raven!

On May 6, Morgan successfully and impressively defended her Ph.D. thesis, titled Organic Matter Sulfurization in the Modern Ocean. We went for the record, grilling her for nearly 3 full hours, which she survived with flying colors. As of June 10, 2016 (graduation day at Caltech), she is officially Dr. Raven. She will move on to a postdoc position with David Fike at Washington University of St. Louis at the end of the summer, as an Agouron Postdoctoral Fellow.

Welcome Jess Hinojosa

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Jessica Hinojosa joins the research group this month as a GPS Chairs Postdoctoral Investigator and AGEP Fellow. Jess will be working on leafwax D/H paleoclimate records of the Southern Hemisphere, based on sediments from fjords and lakes in New Zealand. Jess recently completed her PhD at the University of Otago (Dunedin, New Zealand). Welcome to LA, Jess — you can take your coat off now!

Reto Wijker joins the group

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This month we welcomed Reto Wijker, the latest postdoc to join the group. Reto comes to us from EAWAG in Zurich, Switzerland where he did his PhD working on stable isotope records of microbial contaminant chemistry. At Caltech, he will be working on our project to understand microbial D/H fractionations.

Glaciers! Kiwis! Sand flies!!

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Field trip participants pose in front of the Franz Josef glacier on a typically sunny(?) day. At least there are no sand flies up here. Trevor Chinn, bottom right, was our local guide.

This spring, I had the good fortune to lead (along with John Eiler and Mike Lamb) an international field trip to the south island of New Zealand. We took 11 graduate students and 2 undergrads. We started in Christchurch, drove over Arthur’s Pass, down the west coast, back through Haast Pass, down to Queenstown and Te Anau, and back. Over the course of 10 days we saw recent earthquake damage in Christchurch, metamorphic rocks and active landslides in the Alps, podocarp forests and temperate mountain glaciers (and sand flies) on the West Coast, glacial geomorphology around Queenstown, and … of course … Milford Sound. It was the trip of a lifetime, so thanks to all those who made it possible!

Sulfur-mania hits Science

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Jess Adkins, Guillaume Paris, and I have not one but TWO articles published in this week’s edition of Science. The first is a collaboration with Sean Crowe and others, to measure the δ34S of trace sulfate in Lake Matano, an analog for the Archean oceans. We argue that low sulfate concentrations yield small apparent fractionations between sulfate and pyrite, but not for the reason previously thought. Its not that the biologic fractionation disappears, it’s that sulfate is completely consumed thus the fractionation is not expressed. The second paper is work done entirely here at Caltech, along with colleague Woody Fischer. We’ve made the first reliable measurements of CAS in Archean rocks, using our new ICP-MS technique to study rocks from the Campbellrand platform of South Africa. We show that the sulfate preserved in these rocks (which we assume represents Archean seawater sulfate) has a positive Δ33S anomaly, opposite what everyone has been assuming. This means many of the models out there for how mass-independent anomalies get generated must be incorrect. There is a third article on sulfur in this same issue from James Farquhar’s group. Somebody at Science must be feeling the sulfur love...

Professor Stefanie!


Stefanie Wirth, a postdoc in our group for the last two years, heads back to Switzerland this month to take up her new position as a Senior Lecturer at the University of Neuchatel in Switzerland. We hear she has a pretty sweet lake view from her living-room window, and is happy to host visitors. While here at Caltech, Stefanie worked on leaf-wax D/H proxy records of Holocene climate change in the Swiss Alps. In particular, she has been combining lake-sediment D/H records with sedimentologic records of flood frequency.

Welcome Peter Douglas

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Peter Douglas has joined the research group, having recently finished his PhD with Mark Pagani at Yale. He will be working with myself and John Eiler on using clumped-isotope thermometry of methane to investigate sources of permafrost methane release in the arctic.

Min Sub Sim joins the group

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Min Sub Sim has joined the group as a postdoc working with myself, Jess Adkins, and Victoria Orphan on our big Sulfur project. Min Sub’s main project is working on isolating intermediate species in the sulfate-reduction pathway to measure their isotope composition by ICP-MS. He comes to us from a postdoc at Northwestern with Matt Hurtgen, and got his PhD with Tanja Bosak and Shuhei Ono at MIT.

Under new management

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Dr. Fenfang Wu has joined the group as our new Laboratory Manager. Fenfang comes to us from Teledyne, where she worked on gas analyzers in their testing and calibration group. Before that she was a postdoc at Caltech in the Kellogg Radiation Lab, and has a PhD in neutrino physics from UC Irvine. We've agreed to teach her organic geochemistry if she can explain the whole Higgs Boson thing to us... 

A new cave

Last summer, the ESE option finished moving into its newly renovated home in Linde + Robinson Hall. Although we're sad to see some of our colleagues move (albeit just next door), this has a silver lining for us: some of the vacated lab space has now been renovated as a new instrument lab for geochemistry. We have recently moved all of our instrumentation into the new lab, and at over 1000 square feet this more than triples our previous analytical space. What's more, it has big windows! Features of the new lab (for those gear-heads among you) include a dedicated instrumentation electrical busway protected by a massive power conditioner; hard-plumbed gas lines (11 in total) that lead to a tank farm in the hallway, and with 5 separate 'stations' for connecting instruments; a dedicated and fire-walled local area network for all the lab computers, so that they can share data without outside intrusion (we hope); and a dedicated workstation/server running 3 virtual WindowsXP machines that can be accessed remotely for data processing. Stop by and see it sometime.


West end of the lab. Look at all those windows...

East end of the lab.

Copyright 2015 by Alex Sessions. All rights reserved.