The Excavatrix

1. Box 7A is almost done!

Katlynn Thompson on the 7A throne
and volunteer Katlynn Thompson makes excavating the rest of it look easy

2. Box 14 has been exposed down to more levels.

After removing more fill and plastic we have exposed more of the deposit edges and found more boards, metal bands, crumbling sides, buried artifacts from initial excavation (electrical wiring and a tupper-ware lid) and discovered this:

box 14 hole
??? A hole in the west side edge of the deposit.

Recent finds of the ancient kind in 14 include:

dire wolf sacrum
Dire wolf sacrum found at bottom of level 3

proximal humerus of Little Timmy
Little Timmy's humeri. Here is the proximal end of one standing exposed. It has an old break that caliche filled. This end was removed at that break and the rest of the bone lies in level 4. We also have its other humerus lying to the west in L4.

coyote skull under hard asphalt
A coyote skull, seen under the dark hard asphalt in this picture.

Excavation of deposit 14 has been underway for almost 2 months now and has been very fruitful, as expected, due to what we have already seen in the amount of spill-over fossils that were put in buckets when the deposit was removed from the ground, as demonstrated here by Andie in a previous blog. But before we could poke our dental picks in the top asphaltic sugar sand already showing signs of large bone we had to transform the highly awkward box into something we could work with.

This is how it came to us, after protective tarp removed

box 14 uncovered

The actual deposit is the darker colored sediment in the center. It fell apart when they were trying to excavate it and came to us wrapped with a few boards and metal bands, then plastic, and then supported by tons of the sterile "fill" dirt within the space of the tall box.

box 14 surface

Box excavation preparation included cutting the metal bands that crossed over the top of the box, assembling scaffolding, removing front top board so the public can see us work, affixing handrails for easier boarding, setting up a shade canopy, and determining grid lines, and then box 14 was ready for digging!

box 14 scaffolding

The fossiliferous asphaltic sugar sand midsection of the deposit is relatively easy to dig in. It softly peels and crumbles away from the bone. We never have it completely easy though, as within it there are also spots of hard oxidized asphalt as well as bones that have already been fractured. Given that the deposit was disturbed upon excavation we also have not been taking three point orientation measurements of bones as they are believed to be disrupted from their original position. The only data thus far taken has been the grid and level that the fossil is found in.

Included in what we have found so far:

2 large hervibore vertebrae including sloth

1 coyote skull

1 dire wolf skull, tibia, radius

2 juvenile saber-toothed cat mandibles

lots of bird - including golden eagle skull, teratorn sized limb bones, male
turkey, and hawk

"lots of turtle" - according to Trevor there are at least 3 individuals

pieces of juvenile mastodon skull including a maxilla with teeth that
indicate its young age, possibly younger than any mastodon in the RLB
collection, along with a tibia

Meet "Snuffleupagus" or "Dumbo"

field photo
juvenile mastodon field photo

after some cleaning by Henry
IMGP7077

Also, here's an example of what the main fossil deposit in 14 looks like
box 14 grid C3/L2

and the bird beak I found (my first), which is eagle sized
beak

and the perfect furcula from a medium sized hawk that Michelle found


Deposit 14 has been worked down two levels and in order to continue we
have started removing fill dirt so that we can remain excavating from the deposit's side. Last week bucket by bucket we removed over a ton of fill. Literally. Thank you Sunday volunteers Karin Rice, Bruce Fischer, and Katelynn Simpson for being awesome dirt movers!

Now this is 14's current look
deposit 14 at level 2 floor

In other P23 news the reopening of the rather non-fossiliferous deposit 7a has yielded 3 horse cervical vertebrae and progress has been excellent in box 1. More updates are to come!!!

When we last left our heroes:

where-we-are-today

They were digging away at deposit 5B. And the still are! The deposit has shrunk considerably from its original size, but excavators are still looking for more elements of Clyde, our partially articulated, partially complete Camelops hesternus.

As you may remember from two posts ago, we had most recently exposed his almost perfectly articulated 7th cervical and first thoracic vertebrae, and were pleased to find that his 6th cervical vertebra wasn't too far off:

Hey, we're on tv! Again! Video below features Dr. John Harris & Trevor Valle speaking, and Carrie Howard, Meena Madan, and Tara Thara excavating (and Aisling Farrell and myself for approx 2 seconds a piece, which is perfectly a-ok, because being on tv is scary). "Best of LA," check it out (email subscribers -- I think you'll have to click through to actual blog to view, sorry):

[埋込みオブジェクト:http://bestoflatv.com/player.swf?t=1272259422000]

Little kid questions of the week (both addressed to Carrie):

Small child: "Do you guys ever find anything besides bones in there?"
Carrie: "Like what?"
Small child: "Like weapons??"

I'm sure the kid meant spearheads, but my mind went instantly to a giant ground sloth holding a rifle.

Small child: "Why do they save all the dirt?"
Carrie: "We will look through it for microfossils."
Small child: "Microfossils... ohhhh like ancient germs??"

Now that one, I suppose, depends on what you consider a germ... We do get asphalt-eating bacteria, after all...

Another keen-eyed excavator (your truly, to tell the truth) spotted a new instance of the family Suidae at Rancho La Brea....

Right. So we've been working steadily in deposit 7A, and are about 1/2 a meter down in all areas. There were three bones immediately visible on the surface (all sliced by the tractor that found them, and horribly dried out), but other than that we've yet to find any substantial vertebrate fossil deposit. We've found a few scattered pieces of turtle shell (not to mention some extremely odd fragments of mineralized bone -- very rare for Rancho la Brea!) but none of the big jumbly bone masses we've come to know and love. What we have found:

Gastropods! And lots of them.



These freshwater snail shells are further contextualized by the immense amount of plant material we've been getting out of the deposit as well; the northeastern corner of the deposit is filled with what appear to be tree branches (but possibly roots). Additionally, there's some interesting stratigraphy going on in this deposit: layers of river sand and large rounded rocks.


But as of yet no big vertebrate fossils. Boo.


For that reason (and because we're acutely aware we're already one year into a five year project!), we've put deposit 7A on hold, and re-doubled our efforts in deposit 1 (the big box we first started in).




And we've made some really impressive progress! But more on that next post. Until then, I leave you with this month's "What is it?" Check out the photo below, and leave a comment with your guess of species and element! Correct guesses win a congratulatory shout out on the next post, and the knowledge that they have bettered their internet peers!


Happy guessing!

With Ryan gone, life is much daintier here at Rancho La Brea.

dainty dainty dainty
ping ping ping!

However, this does not mean that we are not still capable of great feats of strength:

meena angry, meena smash!
once, this was a chisel. now, it is rubble. such is life.

as is evidenced by the still-growing pile of broken tools left in our wake (volunteer Meena broke this one...)

Thus, over the last week our girlie muscles have brought Deposit 7B down almost a meter below its original grade. 7B is small, and not densely fossiliferous, but nevertheless productive enough to stay interesting:

7b as it was... and never shall be again.

The femur is the latest of several sabertoothed cat bones we've excavated from this area (including a skull!), and we're wondering if they're all from the same individual animal. We won't know for sure until they're cleaned and officially identified by the folks in the lab.

Less immediately exciting, but still important: there's a huge chunk of rock hard oxidized asphalt right in the middle of the deposit. There are bones around this asphalt, but not in it. We think this might be a vent -- the fissure in the ground that the asphalt originally oozed up from! We've seen this in Pit 91 before, but haven't been able to observe it as well as now. We only worked in Pit 91 for 12 weeks out of the year, and would only excavate a fraction of the exposed grids each season. This means that though interesting geological features were documented, it would sometimes take years to see if they continued another foot below the surface -- just because it took us that long to excavate the entire floor. Working year round with smaller deposits is allowing us to focus on unexpected geologic/taphonomic environments like this one.

I mentioned the lab earlier, and soon we'll have a proper Update From Indoors but until then:

[埋込みオブジェクト:http://www.youtube.com/v/B70GIYu2o-4&hl=en&fs=1]

here's a soundtrack-less time lapse of the preparation of Zed's right femur. Still a work in progress, but you get the general idea. Email subscribers: visit excavatrix.blogspot.com to see the video. Or scroll down:

zed's femur

to see Zed's femur in it's shiny, well polished glory.

That's it for now, more later!

Hello! We found a very neat thing a few weeks ago:

Associated bird skeleton in situ at the La Brea Tar Pits

It's a bird! It's a plane! It's-- wait, nope, it's a bird. The many small bones in the upper left-hand corner (with the big arrow pointing at them labeled "bird") are all from a small passerine, (or "perching bird"). These bones likely represent an associated individual; they were found in a slightly separate layer of asphaltic sand than the rest of the deposit, and some bones even appear to be somewhat articulated. In other words: this is the almost complete skeleton of a small bird; this is extremely rare; I have named him Kevin.

Though most birds are passerines, they are nevertheless rare at Rancho La Brea; our collections are dominated by bigger birds of prey like teratorns and condors. It's hard to say what species Kevin is, exactly -- especially without cleaning and preparing the bones first -- but Lab Supervisor Shelley says he's about the size of a scrubjay.

Kevin the associated bird from Project 23 at the La Brea Tar Pits

The bones in the numbered in this photo are as follows:

1. carpometacarpus
2. scapula
3. 2 limb bones -- not sure which exactly
4. sternum
5. tibiotarsus? I think?
6. tarsometatarsus
7. femur?

The photo above was taken after removing a number of other bones separately, such as ...

furculum of small bird (kevin)
the furculum...

scapula of small bird (kevin)
another scapula...

A passerine humerus, with finger for scale

...and a humerus (as well as an articulated synsacrum and femur, several vertebrae, and several phalanges that I don't currently have photos for). After removing these uppermost bones and discovering there were even more underneath we decided to remove the rest of the skeleton in one block...

Associated bird skeleton about to be removed

which was accomplished by gently prying the layer of asphaltic sand it was rested in with well-placed screwdrivers and chisels.

Though this skeleton is exciting in and of itself, its context may actually be more important. As regular blog readers may remember, up until now Deposit 1 has been more dirt than fossils. There's a dense cluster of bones in the southeast corner that has yielded at least 1000 specimens (and at least that many more to come), but about 3/4ths of the box has been largely sterile. Not anymore. As we dig deeper into the so-called "sterile" areas, we've found a new layer of fossils:

where kevin was found.

This is a different style of deposition than in the "main" bone cluster we've previously worked on:

1. These fossils are spaced further apart, and spread out more evenly -- not all jumbled together like pick-up-sticks.
2. These bones are broken, weathered, and worn. The bones in the other cluster are largely complete
3. Many of the longer bones and bone fragments point in the same direction (scroll back up to the top of the page to get a closer look) -- perhaps implying stream movement? We don't know! But it's interesting...

Kevin was found in the northwest corner of this grid (near where the meter sticks cross) in a slightly separate layer of asphaltic sand -- perhaps implying that he flew in and got stuck after the rest of these unlucky beasts? Again -- we don't know! But also interesting! We will keep you posted as things and finds progress.

la brea tar pits panorama - pit 91 compound

OH, we have been bad bloggers. Apologies for the complete and total lack of communication. BUT, in our defense, we've been really busy. Look:



This is Deposit 7B, and it is open for excavation. Now that 10A and 10B are done, lead excavatrix Kristen and curatorial assistant Aisling decided that the 7's would be next to go (while continuing work on the never-ending saga that is Deposit 1). According to APRMI's field notes and photos, the 7's are pretty fossiliferous -- more so than 10A and 10B, anyway -- and so far, the sediment hasn't been terribly hard -- good for excavators' hands, good for the fossils' relative safety.

Serendipitously enough: Shelley et al in the lab just opened another plaster jacket in the lab labeled "mammoth" only to find that it's actually half of a Giant Ground Sloth pelvis from near Deposit 7. Other finds from 7B:


From top to bottom: the ischium of a bison pelvis, an herbivore (possibly bison) rib, a cervical vertebra from a sabertoothed cat, a bit of plant, and a dire wolf humerus. We've also recovered another sabertoothed cat vertebra, another herbivore (possibly bison) rib, and a small piece of maxilla that may belong to a small dog or a mustelid of some sort -- we won't know until it's clean.

So, why has this taken up so much time? Well, I'll tell you:
Opening a new box/deposit isn't as simple as lifting up a tarp and digging in. First, we have to determine the box's original cardinal orientation -- that is, we have to figure out what side of the box originally faced north. More often than not, our imaginary north arrow isn't actually perpendicular to the northernmost side of the box; it's at an angle that can only be determined by carefully referencing original field notes from the salvage. It's only after we figure that out that we can set our grid lines, and begin digging. The diagram above (mid-pass from me to Laura) is a sketch of the overall layout of Deposit 7B, with every grid labeled, and the angle of that imaginary north arrow recorded for future reference. Did all that makes sense? If not -- comment, and I'll explain better next post.

So what else have we been doing?

[埋込みオブジェクト:http://www.youtube.com/v/ebTNpTYsvmo&hl=en&fs=1&color1=0x3a3a3a&color2=0x999999]

The Page Museum hosted an Art + Science event in conjunction with LACMA's art walk. I put this 4 minute time lapse film-lette together for it -- PLEASE watch it; I think it turned out quite nicely! Time lapse experiments are largely responsible for stealing the time I would ordinarily spend updating the blog -- sorry! -- but I hope you will agree that the results have been worthwhile.

LACMA's art walk invaded our side of the park in a pleasantly chaotic sort of way:


These partially constructed hexagons of what would have been a geodesic dome spotted the hill surrounding the museum.


And these white and black tarps surrounded our sloth and bear sculptures! By the end of the day, they were re-purposed somewhat...


...as awesome space age forts for young paleontologists. More pictures, as always, if you click on the picture above and explore our flickr photo feed.

Speaking of social networking...



...especially when I'm MIA, or if more than 140 characters is just too much for you.

Finally, Michelle has recently discovered her true calling: she is a poet, and she didn't know it. Her specialty: the ancient Japanese form of poetry known as the haiku:

Working in Box 1
Ouch! I hit my hand again!
Chiseling is hard.

Dermal ossicles
There are many in this grid.
Natural defense

Glossotherium
Haikus can be so random.
Cheese quesadilla

Like I said, we've been very busy! Next update will be prompter, I promise!

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