paleosol

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My day in four photos. I left pinedale this morning super excited to do high-resolution sampling for paleosols at Honeycomb Buttes, but the road (“road” = faint two track literally just through fields of cows having sex) got potholey and muddy and I was nervous about driving another hour out, so I sadly bailed and headed down to Utah early. It was an absolutely gorgeous drive - great weather and breathtaking views the whole way. Then I had to decide: camp or cheap motel? The campground I have booked for my planned nights here is full, so my options were KOA or BLM. which normally, BLM any day. But driving through the Swell area I wasn’t sure about where to go, and it’s 100 degrees and a shower after fieldwork is veeerrry nice. So I’m being a lame wimp and moteling it. Hoping tomorrow goes better…

Last two photos are from around the Swell at sunset. Pretty gorgeous.

Hope Jahren (b. 1969) is a geochemist and geobiologist working at the University of Oslo in Norway. Her research focused mostly in the area of fossils, and included the first extraction and analysis of DNA from paleosol. She was the recipient of multiple prizes, including three Fullbright Awards.

She is also known for her book Lab Girl, which combines personal history with science writing, and talks about the challenges of being female in the science world.

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Life took hold on land 300 million years earlier than thought

Life took hold on land at least as early as 3.2 billion years ago, suggests a study by scientists from Berlin, Potsdam and Jena (Germany).

The team led by Sami Nabhan of the Freie Universität Berlin studied ancient rock formations from South Africa’s Barberton greenstone belt.

These rocks are some of the oldest known on Earth, with their formation dating back to 3.5 billion years.

In a layer that has been dated at 3.22 billion years old, tiny grains of the iron sulfide mineral pyrite were discovered that show telltale signs of microbial activity.

These signs are recorded both in trace element distributions as well as in the ratio between the sulfur isotopes 34S and 32S in the pyrite.

Using instrumentation installed in Potsdam in 2013, the scientists showed that the fraction of 34S in the core of some crystals differ characteristically from that of the same crystal’s rim, indicating that the exterior of the grain involved a processing of sulfur by microbes, so-called biogenic fractionation.

The determination of the 34S/32S ratio, using sample masses less than one billionth of a gram, was carried out at the GFZ German Research Centre for Geosciences by Michael Wiedenbeck of the GFZ’s secondary ion mass spectrometry (SIMS) lab.

The composition of the rock, the shape of the crystals, and the layering visible in the field all indicate that the studied rock sequence was derived from an ancient soil profile; this so-called paleosol developed on a river flood plain 3.22 billion years ago.

Field data collected during this study imply that a braided river system transported the sediment containing the iron sulfide crystals.

It is interpreted that microbes living in the soil, at a level that was continually shifting between wet and dry conditions, subsequently produced the rim overgrowths on the pyrite crystals.

Based on this evidence, the scientists conclude in their publication in the journal Geology that they found evidence for biological activity on land at this very early date.

Their research pushes back the date for the oldest evidence of life on land to some 300 million years earlier than previously documented.

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I found a sequence of pennsylvanian aged sandstone, paleosols, and shale today. The sandstone overlies the paleosol layer in the first photo. The sphere thing pictured below is one of many such rocks I found embedded in the paleosol. You can see where I found the one I took in the bottom left part of the first photo. I’m not sure what it is, but it is very fissile, and not very well lithified (though not loose like compacted dirt). The grains are very fine, and the the sandstone that overlies the paleosol layer it was found in was deposited by a river. I was thinking a concretion, but do concretions sometimes split like this? Part of me thinks that it is a hunk of shale that was weathered by a river. I’m not sure at all though, have any of yall ever seen anything like it? 

你好地质人, 

Ni Hao Di Zhi Ren,

We’re enjoying early spring conditions in Inner Mongolia sampling great paleosols from the Cretaceous and Cenozoic. Tonight we’ll wrap up fieldwork and enjoy some baijiu with our Chinese colleagues to truly embrace our inner Mongolian!

Daniel Ibarra, Jeremy Caves, Matt Jones, and Yuan Gao, Ph.D. students at Stanford, Northwestern, and China University of Geosciences, Beijing

地质