USC Dana and David Dornsife College of Letters, Arts & Sciences > Blog

August 10, 2014

Phase 3: jigsaw puzzles and small victories

Filed under: Andean Fossil Hunt,Guess the Fossil! — Kathleen Ritterbush @ 5:13 pm

6:45 pm

Huge success today. If we had the energy Joyce and I would have done one of those jumping high-fives with the sunset behind us on the mountain top, like in the closing credits in a movie. BUT, as it happened we were hustling down a pretty steep slope, trying not to fall into any giant holes or off any cliffs, and it was just beginning to rain. So imagine that we high fived while jumping in the air, and add a llama, and that about sums it up.

Today we worked in a rural area beside a rushing river and grazing lands. This is one of my favorite field sites but it’s a MONSTER. The whole interval I’ve been interested is a pack of rocks about 140 meters thick, and the Earth Life Transitions team is increasingly interested in another 50 meters of rock below that. Now these are layers of mud and sand and animal shells that once accumulated on the seafloor, but now they’re shoved up onto mountains in the darned Andes. They’ve been heated, folded, bent and broken, faulted and eroded by rivers and rain. We want to observe the rock beds in the right order, as they once accumulated near a beach. BUT, the closer we look, the more we see that each chunk of rock is broken into it’s own little tower. A 10 foot tower of mud rocks here, a 15 foot tower of glassy rocks there, a few feet of sandy rocks exposed between the grasses over there. So we climbed a few big hills, and we tried to put the jigsaw puzzle pieces together.

Rock availability differs, and it effects how we are able to look for clues to past habitat conditions. At this field area there is way more vegetation, but at least the rocks in this photo, from a relatively large block of rock between faults, was easier to piece together than the morning's work.

Rock availability differs, and it effects how we are able to look for clues to past habitat conditions. This field area is only at about 15000 feet, so it has more vegetation that covers hillsides. Instead of cliffs, in some places we get small glimpses of the rocks and we need to piece those together. But at least in the hillside photographed here, the rocks are not separated by major faults, so the task this afternoon was more simple than the morning chore of clamoring between major fault-displaced cliff-sides.

Last year I came here and spent about a week with another geology team identifying these rock puzzle pieces, deciding how they ought to fit together, then measuring their total thickness and noting their general contents. Mud, glassy cherts, sands, silts, etc. I took a sample every 10 feet or so to make a microscope slide, and spent the year pouring over those results. Armed with more information from the microscopic view of the rocks and fossils, and from the synthesis of this site compared to others, Joyce and I came back today to pour very carefully over each pack of rocks and to make detailed observations of clues to the depositional energy. If sands in a rock show tiny beds that cross back and forth and cut each other off, they were interacting with fast-moving sea water. If fine carbonate muds accumulated tiny milimeter thick layers gradually, making a laminated rock, this happened in quiet, slow moving water. Now, quiet water can exist in shallow settings, like lagoons, or in deep settings, farther from the coastline. It is our job to figure out the approximate habitat that formed the rocks, and that fostered the associated fossils.

I tried yesterday to post a photo of a fossil, but hilariously none of my photos of fossils would be recognizable. There is so much lichen and shadow and gunk on the rocks, and in most cases the fossils we’re considering are just broken shell pieces or microscopic. I’m most interested here in fossil sponges, but the sponges usually explode into tiny glass needles that litter the seafloor, so to tell for sure I need to look in a microscope months after leaving the field.

Well today I got two good bits on news on that front. I got a photo of a fossil some folks at home might actually recognize! AND after finding a likely candidate rock, I split open a chunk of chert with my sledge hammer and looked with my 10x hand lens – behold, sponge spicultes from their tiny exploded bodies, right there in the rock. Joyce could see them with the naked eye. She found this really impressive and I felt proud that my fossils aren’t, you know, totally illusions.

Photos and more accounts of the day will follow after dinner! Time for water and soup and photo uploads.

Hasta luego!

10:20 pm

Oh man, this is why it’s so hard to run a blog on these trips. Dinner, a shower, skyping with family, and now I’ve got to type the field notes for tomorrow’s destination. But I’ll add some photos once I upload them from my camera. Onward and upward! One more field day!

Guess the fossil

Ok, readers, I finally find time to upload a fossil image for you. Do you recognize what marine animal left this structure behind for use to find hundreds of million years later? Answer in the comments, facebook, or twitter @NerdFever.

August 20, 2012

Guess the fossil!

Filed under: Guess the Fossil! — admin @ 10:16 pm

Howdy!  Saturday night we returned from our Andean fossil adventure – what did we find? Post your guess in the comments, and tomorrow I’ll explain the photo.  Hint: the black and white stripes are each 1 cm.  To read about our expedition, click on the Andean Fossil Hunt link to the right.

August 16, 2012

Fossil answer: burrows!

Filed under: Guess the Fossil! — admin @ 9:18 pm

Time to explain our mystery fossil!

Scott is correct – it DOES look kind of like something was coming out of a hole on the left of one of the orange tubes.

 

These are fossils of burrows – tubes dug by animals on the seafloor.  The block we’re looking at in the photo is turned on it’s side, and we’re looking at the underside.  The orange color is a coincidence of the sediment type and weathering processes.  It nicely highlights the shapes for us.

In healthy ecosystems, marine critters live above, on, and in the sediment at the seafloor.  But how to preserve these burrows?  It can be difficult, because storm and wave activity can erase the trace that these burrows ever existed. Typically we only record fossils of burrows that were deeper – at least 20-30 cm into the muck.

These burrows in the photo are called, “Thalassinoides”.  We name trace fossils independently, because we’re rarely sure of the tracemaker.  These kinds of burrows – deep, diverging, with many chambers – are associated with shrimps in the modern ocean. There’s very cool modern work done on these burrowing shrimps – especially by Dr. Wiebke Ziebis at USC.

Burrows are amazing.  Once you learn how to see them in rocks, you can’t UN-see them!  It was a blast showing off lots of photos of burrows during my talk at the Geological Society of Peru today.  Some people there at the meeting – and the geologists I worked with in the field – will now see burrows long overlooked in the past.

Here’s one of my favorite pics of fossil burrows.  It’s from a site in Nevada, famous for it’s well-studied sedimentary layers.  I talked with a grad student researching there and she, like many other people, hadn’t even realized her site was FULL of burrows!

This is my labmate, Carlie.  Behind her, the dark colors highlight the burrows that permeate so much of these sedimentary layers.  Burrows – they are all over the place!  They tell us a lot about the environment – The diversity and abundance of animals, oxygen levels, all that good stuff.  So, after a mass extinction, obviously I’m keeping my eyes out for burrows of sea floor animals.

August 15, 2012

Guess the fossil!

Filed under: Guess the Fossil! — admin @ 5:36 am

A friend requested more posts and photos about fossils!  I will deliver.  Why have I posted so few? Below, I explain my two pragmatic reasons.

But first, a fossil!  Let’s make this interesting.  Take a look and give me a guess what you think this image shows.  Post your guess in the comments so everybody can see.  Don’t worry, there are no silly guesses – this is how paleontology became what it is today.  We learn to reexamine rocks and every year realize there are amazing records of past live we’ve overlooked for centuries!

Specifically, check out the orange-ish parts of this rock.  Is this a fossil? If so, of what!?  Hints: red and white stripes on the Jake staff are 10cm each. This image is looking at the bottom of a layer of rock.  Need more hints? Post questions in the comments, and I should be able to answer in Lima.

 

 

Why haven’t I posted pictures or videos of my rocks or fossils here?

1)   When lucky enough to have a hotel during field work, my nighttime duties include cataloguing the days observations and samples, looking up information on the internet, and communicating with people back home.  This blog is a part of that but it’s all I can do to get one dispatch out most nights.

2)   Sadly paleontologists can be very competitive, dishonest people.  I vividly remember my first science meeting, 24 years old, two weeks after finishing my first official summer field expeditions. Researchers from three different countries came up to my poster to tell me they planned to fly to the American west to do my dissertation project before I could finish it. This was after I offered to collaborate with people who turned me down! The silver lining here is that I’m studying something people care about. As a totally non-competitive person, though, I just can’t wrap my head around people who lie and manipulate – basic human behaviors to which, sadly, science is not immune.  Consequently, I don’t so much as post on Facebook about where and when I do field work, and what fossils I find. I post pictures of sunsets and lizards, weeks later.  Because my main dissertation research isn’t published yet, I can’t even describe exactly what I’ve found and why I’m here openly on the internet.

To be fair, though, there are plenty of rocks and fossils I’ve seen on this trip that are plentiful throughout time.  They won’t, you know, spill the beans.  So, insofar as I have time, I’ll post pics and explanations of cool fossils or features over the next week or so.

 

Right now time is short – I still have a sack of specimens to re-catalogue and most of my gear is packed, then we head down the mountain for Lima, a drive of 4-5 hours.  Wish us luck!