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

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.

The hunt continues!

Filed under: The Hunt Continues — admin @ 10:12 pm

Home sweet sweltering Los Angeles! The national heat wave is jarring, but the long hot nights are a relief after the Andean cold.  Last week I was sleeping in a wool scarf!

We’re back in Los Angeles but the hunt isn’t over.  We managed to bring back 2 duffle bags full of rocks – rocks that I have a hunch contain fossilized sponges.

Soft-bodied seafloor sponges rarely leave fossils.  Typically, their bodies decompose, and if we’re lucky, tiny glass needles that once supported the porous sponge framework are later found among sand and mud particles in sedimentary rocks.  From looking at microscope slides of Dr. Rosas, I know plenty of sponges inhabited the shallow seas along Pangea right after the mass extinction.  But why does that matter?

Around 201,300,000 years ago, Pangea split open, releasing 10 million square kilometers of Hawaii-style lavarock (basalt).  (Part of that spill is now the Pallisades near New York City!)  Consequent changes in chemistry and climate correspond with the effects from human fossil fuel use we see today – and, at the end of the Triassic period – to animal extinctions around the globe.  The aftermath of these events is most interesting too me, and the Triassic/Jurassic crisis caused fascinating changes. Dinosaurs radiated into suddenly available ecological niches, spreading to famously dominate the land.  But in the sea?


Mass extinctions change everything.  Even the least-significant animals build together frameworks and habitats and communities that shape our world.  When those animals die the habitats – down to the very floor of the ocean – change dramatically.

In fossil hunts for my dissertation research, I’ve uncovered a mountain of unexpected sponges in Nevada.  After the mass extinction, siliceous sponges dominated seafloor habitats here in seaways along the northern part of the Pangea supercontinent.  I’m not talking about hundreds of sponges.  I found millions of sponges, sponges that cover whole fossilized sea-beds, greedy sponges that apparently did not share well with others. We don’t see corals, clams, crinoids – all the other characters we’d expect to find.  For about two million years the regular habitats – reefs, clam beds, crinoid banks – were missing

I traveled to Peru to compare and contrast the record from Pangea’s southern coast to what I’ve seen in Nevada.  We didn’t know what to expect – maybe enough observations for a paper now, or maybe we’d scout rocks to revisit later.

We won the fossil lottery.  We found both enough material to write a paper now, and so many excitingly challenging rock sequences and fossil occurrences that I’ve got to return to Peru next year!

The rocks we visited in Peru are incredibly well studied.  In the western Andes they bear valuable metal ore and in the east they bear oil. Researchers in Peru want to know why the valuable materials occur.  In the photo above, the head geologist for Pan American indicates the mountains, lakes, mine sites, and rock layers of animal history that link them all.  I think this mass extinction, and the record animals that benefitted in its disastrous wake – holds the answers.  The fossils and rocks we observed in the field support my interpretation that extinction-related changes in sea floor habitats caused the deposition of now-valuable human resources.

Now that I’m back at USC, we start a new search.  I need to further test my interpretations by scrutinizing the microscopic record hidden in the rocks themselves.

I’ll start by making microscope slides from the rocks samples we brought home.  To do this, I:

cut a domino-sized rock sample,

glue it to a piece of glass,

cut off the extra rock,

then polish the remaining sliver of rock attached to the glass ‘til it’s thin enough to see through.

Did I mention the glue has to be 140 degrees to seal properly?  Yikes!  Making these slides is no joke.  But I’m so eager to see what’s inside these rocks! From microscope slides I made from Nevada specimens, I can now tell the difference between seafloor muck with bits of dead sponges, and rocks that contain actual fossilized pieces of sponges that died abruptly.  I’ll use the microscopic observations to piece together how abundant sponges were, what habitat they preferred, and how much they hogged their territory.


I’ll post about what I find, but it may have to wait ‘til after we take the new USC Earth Science grad students camping this weekend!  If this is your first visit to the blog, check out posts from our Andean Fossil Hunt – it was a wild adventure, and I can’t wait to go back!


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.


Filed under: Life in Lima — admin @ 9:00 pm

Howdy, y’all.

Here are some pics from our journey down the mountain yesterday:

Last morning in the Andes

Raul stopped by his grandmother’s farm to get some potatoes for breakfast, and to deliver to his family in Lima on our way back to the hotel.

And as a treat on our last day in the highlands we saw a herd of dozens of alpaca.  yay!


A successful field session all around! Last night we arrived back in Lima.  Tonight I gave my talk at the Geological Society of Peru.  About 25 people came – not bad for a last minute meeting.  And it was simultaneously broadcast to 5 other universities across Peru!

A few people were avidly interested, and we had a good discussion during the question session about other sequences in Peru, and other records of the mass extinction.  Afterwards, a couple of people wanted copies of the slides.  I chatted and had a bit of wine – finally!

Dave and I have both been a little sick – it seems inevitable with so much international adventuring.  I’ve just got to keep my act together so I can finish up at the university tomorrow.  I’ll discuss our results with Dra. Rosas, show her some fossils, and hopefully get started to plan my next visit here!

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!


August 14, 2012

!No quiero a salir!

Filed under: Andean Fossil Hunt — admin @ 8:29 pm

[I don't want to leave!]

A tremendous day to end a tremendous field session!  Again, I am blown away.  By the rocks themselves and our luck to find their fossils, by my incredible new geology friends, by the whole adventure of it all.  I could not have imagined a better trip.

We have enough exciting fossils and rocks to publish a new interpretation of this sequence, and to reveal important events following the mass extinction.  We went far beyond the fundamental questions I posed in my proposals.  And, we have a mind-boggling collection of fun challenges for the future.

We went to the site by the farm today, and the farmer indeed left the gate unlocked for us.  Almost no fossils to see there, but plenty of sedimentary structures.  When the waves interact with bits of sand and shell on the seafloor, they can leave lasting marks in the rocks.  200,000,000 years later, I’m interpreting these layers of sand and shell and muck to determine the history of the environment where our animals lived.

A key challenge of this expedition is tackling several different field sites.  This way, we can see the conditions in different parts of the environment that simultaneously recorded responses to the mass extinction.

The last site of the trip was spectacular, and the highest elevation, in the Sierra Nevada range.  I’d been marginally interested after a preliminary scout session on Saturday.  Then, yesterday morning Julio brought me cores from Sierra Nevada, and I knew I wanted to see it with my last remaining half day.

WOW.  So many fossils, so many peculiar associations.  In fact, these rocks looked most like my material from Nevada.  I spent three hard years banging my head (well, my rock hammer) against those rocks before finding their secret of sponges.  Now, it seems like Mission: Impossible Fossil is my specialty.  This afternoon, I was looking at rocks equally frustrating.  I’m riveted!

A crucial skill in geology is reconstructing the history of a pile of rocks.  Fossils are great, but they can only inform us about mass extinction ecology – specific animals at a specific time – if we can organize the rocks into relation with others.  If we can discover the correct stratigraphic order, the correct sequence of the rocks, then we have a guide.  Sure, rocks are often stacked on top of each other.  But what about when they point straight at the sky? Or when they twirl around and flop over on themselves.  Picture a gigantic taco shell made of 40-foot thick rock. That’s what I saw today.

Over lunch – fried trout from tiny family farms – Julio and I talked about jobs and vacations and vocation. He’s an exploration geologist.  His life, like mine, is full of daily mysteries, and mysteries that take years to tackle.  He’s been looking at this taco shell of rock for six years.

Today we searched for and found fossils.  Together we collected notes, photos, observations, and samples for microscopic analysis.  Raul is stellar at finding fossils, it turns out, and chiseled out a half dozen for me while I photographed those too tough to remove.

We were at close to 14000 feet of elevation today.  Conveniently, the site led to a steep slope with a road at the bottom, so the drivers pulled the trucks around and then met us half way.  Easy!  Still I got winded – glad I ran all those stairs back in LA.

Dark clouds moved in and the cold sharpened in a persistent wind.  Julio and Armando and I agreed it was time to go, and we were only half way down the slope.  Wouldn’t you know, we kept sighting more fossils all the way down.  We kept agreeing to leave, then finding something too good to pass up – just a photo! Just a photo.  Finally, it started snowing.  Snowing.  OK, OK, now I will get off the rocks.

There was just a bit of snow but it was already five, and Raul would have to drive in the dark on the windy roads down to his valley hometown  In the lessening light and sprinkling snow, I gathered all my samples, exchanged contact info, goodbyes and hugs all around.  Man I hate to leave these rocks. I hate to leave this countryside and I hate to leave these damn fine geologists.  But everybody’s got other fish to fry, and I have a hunch I’ll be back.



August 13, 2012

surprise and sheep

Filed under: Andean Fossil Hunt — admin @ 7:59 pm

Today began with the most fantastic surprise. Julio brought me CORES!


Wild rocks are big, and messy, and plants grow on them and sheep make messes on them (especially here!) and they tend to fall apart.  So if a company or academic group has money and wants to know more about rocks, they take a core. Picture putting a straw into the rocks, holding your thumb over the top, and pulling it out. It’s exactly like that!  Only it costs at least ten thousand dollars and half the time everything in the tube breaks.


I thought Julio said he’d bring me photographs of some kind of holes from one of our field sites. No.  He brought me these rock cores from inside the earth, totally perfect clean rocks, of exactly what I’m looking at here in the mountains. We poured water on them to make the fossils clear. Julio had looked through photos to decide which cores from the company collections might interest me most.  He chose wisely. They were amazing!  They contained diffinitive evidence of some of the phenoms we’re chasing – the mass extinction, the impact on local rock development, the rise of sponges.


The rest of the day was a bit of a struggle.  I was again managing a team, with so many language limitations, and so many ambitions. I feel exactly like this on every trip.  If I only had one more week, one more day, one more hour.


I was working, balancing time limits, detailed notes, vertical relief.  Meanwhile the geologists above me were scaling the cliffs like eagles.  That’s when I shot this video.  This is how I feel all day every day out here.  Outwardly, it’s business business business, but inside, I am shouting this:


As a grad student, I have to select a set of problems I can handle now, and accumulate interesting investigations for the future.  Dave says, “Those are projects for you future master’s students.” He’s right.


Today I needed to work with finality. Measure, sample, select, choose.  Though I’ve got this great team, I can only be in one spot at a time. When should I take the photos I need? Should I take them now with the sun casting shadows or wait for the perfect diffused cloudy light? Should I call one objective a bust and move on to the next?

But as I joked repeatedly to my team today, I’d take the whole mountain if I could, and I never want to leave.


We worked our tails off, ate lunch, worked again.  I managed to explain the American adage, “I’ll work when I’m dead”, which we all thought was ridiculous.  I told the geologists that since they work so efficiently, they could take the precision attack jobs, and I’d take the careful plodding thoughtful musing jobs.


In the end, we got it all done.  Well, whatever we didn’t get is fruit for another trip, another team, geology students from the university in Lima.  I finally agreed to leave and go back to the trucks, but then I heard hammering.  Sure enough, the guys were trying to sample some more.  Again I agreed to leave twenty minutes later, and again, I heard more hammering behind me.  Good geologists never want to leave the outcrop.

So it was almost sunset when we left. Everyday we pass through this flock once or twice, with the shepherd and her sheep dog and puppy.  But today, on the road, we saw two little lost lambs all alone.

little lost lambs sm


August 12, 2012

Cultural notes about the high Andes

Filed under: Andean Fossil Hunt — admin @ 5:10 pm

Today we saw VICUNAs!!!!! My ungulate triumvirate is complete!  Llamas and alpacas are pack livestock native to Peru and derived from the wild – and still present – vicuna. Our driver Raul said we would see them and we did!


Our field site sandwiches a colonial complex of ore processing and livestock and living areas, all built hundreds of years ago.  I’ll be looking for sponges then think, Oh, Damn, this is man-made! And find myself walking on a wall hundreds of years old.  I mean, to me, that’s not much time.  But my dad will be impressed.  See the group photo in the last post.

Our driver is from this little mountain town that has the only hotels and his grandparents still live here.  Seriously – he saw them on the road tonight when we arrived in town and he stopped to chat a moment.  They live in the Andeanas – the terraced slopes of the high plateau where the Incas developed agriculture.  When the Spanish asked about the mountains, and pointed, the locals answered, “Andeanas”.  They grow a ton of flowers to send to Lima, but they’re also used for an annual Easter festival here in town.  Raul told us all about it.  Now that he knows we enjoy cultural information, and that my Spanish is improving so I understand more – he’s been very informative.

Other fun things right near our rocks  – cows at pasture across the river, sheep together with their human shepherds and sheep dogs – real sheep dogs!  Most dogs are mutts here.  And people gathering grains.  Raul explained but I understood nothing until he said, “cervesa”.  Ahah! Hops!

La Equipa de Sueños! [the dream team]

Filed under: Andean Fossil Hunt — admin @ 5:09 pm


I am just speechless.  This is the craziest, most fortuitous, most amazing field trip.  WOW.


Fossils.  Tons of fossils.  Ammonites, sponges, bivalves – everything a girl could want, if she lived in the earliest Jurassic ocean.  WOW.


And my team.  My team!  Spectatular geologists.  Really amazing.  Even the drivers, curious, hard working, eager to join in, made important finds.  Really amazing.


First I asked the geologists what they wanted to do for the day.  They said, of course, to help me.  This is amazing because Dave and I thought, look, this mining company is sending “an assistant” with us to keep an eye on us.  That’s handy, so we don’t get in trouble with the police or locals or anybody.  But instead we got two professional exploration geologists, and their driver who is super helpful but I don’t know his official vocation.  I don’t know if the head geologist assigned the second geologist with us or if he asked.  Either way, it’s spectacular.


In the morning, I spent the better part of an hour explaining my plan and answering questions.  First, I gave them printed explanations of my sequence of rocks in Nevada, then took them on a photo tour of my site’s best sponge fossils on my laptop.  After that, I showed them photos of microscope slides – both of my Nevada sponges and from Dra. Rosas’ slides from the rocks on which we sat.   then I laid out my plan for how we could all explore the rocks, and what specific priorities to look for.  I did this entirely in Spanish, asking for words by description in Spanish and with a couple written down in my notes.  It was exhilarating,


More exhilarating was the fact that they TOTALLY understood what the hell I was saying.  I don’t mean just the words – and Julio, who speaks some English, helped to explain concepts for me.  Even when I speak in Spanish, and I think in Spanish, I have English ways of constructing sentences and thoughts.  Anyway, they didn’t understand just the gist or just what to look for.  They totally get why I’m here.  They get that this mass extinction completely changed the world, and the changes explain these totally frustrating wierdnesses about their valuable rocks.  And they totally want to help, to discover for themselves the answers, and to learn how to see and interpret fossils and sediments.

At lunch, we sat by the river.  Everyone brought too much food but it was delicious.  After lunch we compared notes on our findings.  Wow!  Three teams, working totally independently, ended up observing almost the exact same package of rocks, and reported very similar findings.  A few pseudofossils, but I was able to explain these well enough without letting anybody down too hard.


After lunch I walked through each of their findings.  Incredible.  I showed them which parts are valuable, and which are not related to life 200,000,000 years ago.  There’s a lot in a rock that didn’t happen then.  And I think they saw more of how I prioritize and sort fossils and sediments of importance.


When we were done, we decided to explore more, with the last hour of the day.  We went to the roadside to look for ammonoids.  Again, we split up, and again we found the same stuff.  But bringing together these different observations, comparing them, seeing how the rocks connect – I mean PHYSICALLY connect – this is amazing.  This is worth a dozen days in the field.  More.


It take SO MUCH TIME to go through rocks, to learn what’s important, to decide where to search.  Even though I know what we’re looking for, here’s an example.  I had a lousy morning.  I was on one side of the creek and ruins, and my rocks were ok but a bit busted and too much caked on dirty caliche to see much.  If I were alone here, I’d be discouraged after that.  I would take another look across the creek, see some of the observations these guys made – but we had six people pouring all over these rocks today.  The synthesis makes those six observations WAY more than the sum of their parts.  We became a team of people, each with the experience of six people.  It sounds silly but knowledge is like this. It’s fractal.


So at the end of the day we found the most unexpected jackpot.  I came here looking for sponges.  We found those yesterday.  Then I wanted a model for how the sponges lived in their environment and the changes in it – we got that during the morning and afternoon.  Then, in the very last hour of the day, we got this surprise bonus.  Ammonites.  Ammonites tell you what was swimming or drifting in the water above the seafloor.  They also tell you time.  Ammonites come and go.  They evolve fast, spread around the world, and go extinct quickly too.  With ammonites, we can zero in on where in time our sponges are, our environments are – all of it.  Dra. Rosas will be so thrilled.  During her dissertation she found maybe two in this particular rock unit.  Other visiting scientists she speaks of found one, another a handful.  Today, in the last hour, we got a dozen.  And of course more fossils between the ammonites to help us learn more.  Totally incredible.


Tomorrow: measurements, collections, observations.  What an incedible find such work.  Julio asked me if I was going to see Cuzco, and when I said no, he asked don’t I ever go on vacation.  Now, when he and I are walking sheep trails between fossils on these steep mountainsides, I point to the river and views and say, “Vacaciones!” and he laughs.


Mini paleo lesson for the nerdly reader!

Filed under: Andean Fossil Hunt — admin @ 5:07 pm

Note – spotty interwebs and the site was down for maintenence yesterday evening.  This is from Saturday night.

Photos coming but maybe after dinner tonight.


As I said earlier, in the sea, little animals make rocks.  Limestone is a rock usually made chiefly from the shells of little boneless animals on the seafloor.  Clams, snails, corals, and less famous critters like crinoids, bryozoans, and brachiopods.  We have many tasks when we approach these in the field.


Paleontologists first typically want to know what kinds (species, if they can be identified that specifically) of animals were living at a certain time.  Old-school paleontologists approach this by making a “range chart”; determining how long each given animal group lived.  Based on this body of work, over 100 years old, I can say, “Oh, I found Psiloceras tilmani, a coiled ammonite [like a squid] shell. These rocks are from the beginning of the Jurassic.”


My approach is very different, and serves very different purposes. I am an ecologist. I want to know, after this mass extinction, what were conditions like for animals? I want to know about abundance – how many? And when I ask “what type of animal?” what I mean is “did animals burrow? Did animals live on the seabed? Did animals live together or keep their own territories separately?”  Usually I go to places where other geologists have already made a list of the species of animals present, but these other important observations are left for me.


Ecology isn’t complete without a sense of the environment in which the animals lived. Was it a fast-moving shallow sea coast, by the beach? Was it a quiet deep setting with little flurries of mud and the occasional storm-generated dump of shells?

In this picture, in the center, is a small white clam – the kind that burrows into the seafloor.  It was found by our driver, Raul! Surrounding it is “matrix”; the sand or gunk on the seafloor, and other “clasts”; the big chunks. Oh, and a TON of living lichen, a fungal/algal association that makes it really tricky to see fossils some times. This layer of rock is about 8 inches thick, full of small pieces of busted-up clam and scallop shells, and is a distinctive laterally consistent layer surrounded above and below by finer, muddier material.  This information fits a “storm bed”; when there’s a storm, waves in the shallows bust up shells and smear them out into deeper water.  It’s a great snapshot of animals that lived nearby, but it has important caveats.

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