Sad but true: our Lone Male Excavator has left us for more exotic locales (grad school in plant and soil sciences on OAHU) and we miss him already. Ryan has been a careful and conscientious excavator, a funny dude, a good friend, and last but not least, an incredibly snazzy dresser (plaid + camo = AWESOME).
Yes, we will miss his hard work, his dedication to replacing shoring boards in the heat of summer, and his enviable ability to reach things on tall shelves, but we will also miss his encyclopedic knowledge of all things Star Wars, his willingness to talk in funny voices for our amusement, and perhaps most of all...
his unparalleled ability to re-purpose old broken office furniture during his lunch break. The above photo may appear to be an ordinary office chair, but look closer! It is actually an office chair attached to another chair because it broke off its original base. The wooden legs of the base chair have been careful sawed at an angle for maximum comfort.
And what became of the base of the chair, you ask? BEHOLD:
This is quite possibly my favorite piece of furniture ever. It's an end table! On WHEELS! This handcrafted beauty is made of another chair (with the back sawed off) screwed onto the base of the broken office chair, with a piece of laminate for a top. And it's the perfect height for chips and salsa!
Finally, Ryan's coup de grace:
A genuinely well-made desk for volunteer Christina, made out of the side of box 10B (I think it's 10B).
In conclusion: Ryan is awesome! We totally miss him! He is funny and us taught about plants and how to sharpen tools and such! However, on the bright side: we now have a couch to sleep on when we go to Oahu...
the process of replacing old side-wall boards in large dug-out spaces (e.g., Pit 91).
This post will serve as both an introduction to some of the "other work" that excavators (and excavatrices) perform at Rancho La Brea and a documentation of the particular method of shoring board replacement that the Lone Male Excavator has developed.
So as the thick boards holding up the side walls of Pit 91 grow old, they often bow out, rot out, or both. Up above the pit, 14ft x 11 3/4" x 2 3/4" boards are stored ready to be cut to an average of about 75" long for use as a shoring board.
After a board is slated for replacement, of course it must be extracted. This is commonly far more difficult than it sounds. If the board is rotted to extremes on the ends locked in by the I-beams, then it is not too tough for a hatchet to cut through one end and pry the board out with a crowbar. If the board is not rotted away much at the ends, however, (as the boards pictured here) it can be quite difficult.
Initially, a cut with a circular saw is made through the board(s) being replaced. This is very dangerous and every safety precaution must be taken at this point (e.g., clean goggles, steady hands, hard hat). It is also messy and anything, including one self, which should not get covered in sawdust should be protected. If two parallel cuts, about 2" apart are made, extraction will be easier. Our cordless circular saw, however, does not cut deep enough to go through to the back of the boards. So I have added to this method inspired by the wisdom of William A. Akersten's thought on sabertooth cat incisor (front teeth) functional morphology.
The points on large, cone-shaped incisors of Smilodon fatalis are separated to the extent that when they pinch together top to bottom and pierce into the skin of prey, they are thought to create a perforated line which allows for easy tearing off of chunks of flesh. When we are unable to pry/break out a board along the saw cuts, holes can be drilled along the cuts to create such perforated lines which can then be hacked trough easily or broken out through prying.Once a board is out, the wall of earth, often asphalt saturated, must be shaved a little with hand tools or, in dire need, a pneumatic chipper. Occasionally fossils are found in the side walls, so these must be watched for and documented when discovered.
Depending on the thickness of the new board and the bowing out of the old board shaving the walls may take up to a couple hours. Once this is done a measurement for the new board's length is taken, giving about an inch and a half behind the lip of each I-beam. (Often, when you think you've shaved enough and try to get the new board in, you find that a few spots need more shaving. The first of these two pictured here took me 3 attempts. I also found that I had cut it too long and had to take an inch off one end.)
After you've seen that the board will fit the space you've shaved out of the earth-wall, you must get it equally situated behind the lip of each I-beam... not so hard when you've got two-three boards out and you are doing the bottom board, but if you are trying to slide a single board over in a single space (like w/ the second board pictured) it can sometimes involve a long trial messing with crowbars. I have no solution, except putting in the lag screws early and trying to use them to slide the board. This does not often work.
If gaps are left, they are reduced by placing thin pieces of wood at the bottom of boards.
The boards are locked in between (and behind the lip of) I-beams which run about 40 ft under ground. As much of the board as possible is slid behind the inside of the I-beam before 5/16" holes are drilled beside the lip of the I-beam for 9/16" x 3 3/4" lag screws. The lag screws go through, what I'm gonna call, giant square washers which tighten the board flush to the I-beam. A thin, small piece of plywood is often needed between the shoring board and the giant square washer. There you have it; Shoring 101. The final exam is getting a board replaced and not injuring yourself in the process.
So the Lone Male Excavator is off to grad school. This is my last day as an excavator at the Page Museum at Rancho La Brea, but I will still be around in spirit. (In fact don't be too surprised to see posts in the future by The Ghost of the Lone Male Excavator.)
Hello! We found a very neat thing a few weeks ago:
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.
The bones in the numbered in this photo are as follows:
carpometacarpus
scapula
2 limb bones -- not sure which exactly
sternum
tibiotarsus? I think?
tarsometatarsus
femur?
The photo above was taken after removing a number of other bones separately, such as ...
the furculum...
another scapula...
...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...
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:
This is a different style of deposition than in the "main" bone cluster we've previously worked on:
These fossils are spaced further apart, and spread out more evenly -- not all jumbled together like pick-up-sticks.
These bones are broken, weathered, and worn. The bones in the other cluster are largely complete
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.
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?
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.
...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!
After about 8 months of digging, Deposit 1 is finally starting to look markedly different than it did when we first unveiled it -- well, to us, at least. Yes, it's still a dusty hunk of rock, but now it's a dusty hunk of rock that's around half a meter shorter than when we first got it.
As I've hopefully mentioned before, we work in 1m x 1m grids, and dig down 25 cm at a time. You've seen this before:
...the large, convoluted bone mass that was keeping us from "closing" grids B-1 and B-2 and moving on to other portions of the box. In both grids, we're working on level 3, which is the section of dirt 50-75 cm below the original ground level of the deposit. Does that make sense? Those large saber-toothed cat scapulae and innominates were sticking out above floor (the bottom of each 25 cm deep level) and needed to be removed before moving on.
Now the grids look like this:
Yes, there are still bones, but if you look carefully, you'll note a wonderful lack of scapulae...
...because Tara got the last one out! Everything left in place is too far below floor to excavate at this time. The grids surrounding the bone mass are still at level 2, so we have to get those down to level 3 before we can open up grids b-1 and b-2 at level 4. Did that all make sense? Excavational peccadilloes are difficult to describe via the interwebs. To sum up: if we keep excavating just the main bone deposit, we'll wind up with a giant hole in the ground (in the box) which will be too deep to keep digging at. So: sterile grids for us, for a while.
In non deposit 1 news: as Ryan and I have both mentioned, 10A is no more! We time lapsed it's final moments:
I have to say, I like the soundtrack to this one better than last week's, but I don't think anything will match excavation to the tune of "I Am the Walrus." Ah well.
Next week: we just laid grid lines out for 5 new deposits -- 7A-E! We're very excited to start work in new, softer dirt. Pictures soon to follow. OH! And click through to flickr to check out the giant freaky black (and brown) widows Laura and Michelle found under 10A.
We've been having a lot of fun with the built-in intervalometer on our new camera:
expect more videos like this in weeks to come! To our email subscribers -- the blank space you see above (and in my last post) is actually a youtube video embedded in the blogpost, which unfortunately doesn't seem to translate to email. Go to excavatrix.blogspot.com to view.
Y'all need to chime in and tell Andrea what a good job she is doing on this here blog a'ight!
We've got a lot done since my last post. Finished another box, matter-O'-fact (10A)! We've busted out them there scapulae from box 1 and got loads more dirt out to, eh.
Keep yer eyes open for a new "what is it" post coming soon!
Yes indeedy, as Ryan pointed out last week, we have finished excavating our very first deposit from Project 23:
10B is no more! And its big sister 10A is soon to follow:
We're down to Project 21-and-a-half. The small patch of fossils from this deposit seems to have petered out. We can't be sure, but we're thinking the remaining few feet of dirt are largely -- if not entirely sterile. The boundaries between grids are left in place until they're completely exposed, and then mapped and photographed. This way, we can reconstruct the deposit's geology long after the deposit has been excavated.
And 5B looks much the same is it did last time I posted, only sans a level of plywood around the sides.
We're waiting to speak to one of the geologists who originally supervised the salvage before we begin digging.
Meanwhile, in Deposit 1....
We're still plugging away at the main bone jumble in Box 1. We've measured out at least another 100 fossils from this area. Right now, however, we're at a bit of a standstill, stuck between a rock and a hard place so to speak. Or rather, a scapula (shoulder blade) and an innominate (one half of a pelvis):
Pleistocene pick-up sticks once again! From left to right: we can't get the first innominate out without removing the scapula immediately above it, but we can't get that scapula out because of the saber cat vertebra immediately above it. THAT's stuck under the middle scapula, which is in turn pinned in place by next-to-last scapula, which is, of course, covered by both a cat humerus (lion or saber cat, not sure though) and yet another scapula.
This is all very detailed, very slow work. However, on the other side of Box 1, we get the other end of the paleo-work perspective:
This is Grid D-3/Level 2 at 9am. Mouse over to see it at 5. Or, just scroll down:
D-3 is largely sterile, except for the occasional articulated millipede or bit of plant matter. This means we can power through it as quickly as our muscles allow. Spencer and I worked on D-3 all day, and chiseled out about 5 full buckets of matrix! Hard, hard work, as evidenced below:
6 blisters on my right hand! Badges of honor, all.
What is a fossil? One of our readers, "Duys" in Belgium recently reminded me of how one can determine a fossil and I thought it a good time to bring it up. I'll meet that idea in a round about way here:
The other day, I held the back door for a family visiting the museum. One of them was in a wheel-chair and since the back (staff) door is nearest the parking lot, could enter there. Anyway, I was heading into the lab and so held that door open too so that they could get a peek inside at Shelley and the volunteers eating lunch and glimpse behind the scenes fossil workstations. The older gentleman pushing the wheelchair asked me if I was a fossil... "I'm getting there," I replied. (Yes, the LME turns 30 in less than a month.) This question the gentleman asked was not one we get often, but we are very often asked if the bones and other previously living materials we dig out are, in fact, "fossils."
Strictly speaking, it depends on your definition of the word fossil. When I took Invertebrate Paleontology, my professor, in the first week, was discussing some common mistakes & misconceptions in word definitions. One he mentioned was archaeology vs. paleontology, between which this blogs readers surely already distinguish the differences and similarities (yes?). Another he discussed was the difference between "fossil remains" and "recent remains," as well as how to tell if what you have is a fossil. Being a geologist, he discussed the difference in whether or not the remains had undergone mineralization. He noted that a fossil will not smell if you hold fire to it. Furthermore, if you stick your tongue to a "recent" bone it will stick a bit, but it won't with a "fossil" bone.
Geologists and dinosaur paleontologists often use this sort of "mineralisation" definition, but how do La Brea bones hold up to it? Since they do still contain collagen, Rancho La Brea bones would, hypothetically, still produce a burning organic smell if we held them to fire. And, yes, ones tongue would likely stick to them if tried, but that may be more due to the asphalt than the collagen.
So I've decided to test these hypotheses with a personal experiment. (Of course, I am not serious.) We don't need to burn or lick these bones to determine that they have collagen, as studies have already used collagen samples from many of the bones in attempts to extract proteins and DNA.
So, are they not fossils? A 30,000 year old bone is a fossil, no matter how you slice it. Ancient Rancho La Brea bones, plant, shells, and insect parts all fall under the more encompassing definition of fossil provided to us by thefreedictionary.com: "A remnant or trace of an organism of a past geologic age, such as a skeleton or leaf imprint, embedded and preserved in the earth's crust."
The Rancholabrean North American Land Mammal Age (named for our site) spans from 300,000 to 11,000 years BP, so being of a past geologic age, our remains in this time frame are fossils.
Here is a question for you all: Are the bones, plants, shells, insect parts, etc., that we find and can date to less than 11,000 YBP fossils? Pit 10 contained a vent of remains, for example, dated at around 9,000 years. So these are not technically from "a past geologic age." Are these bones not fossils?
Since Andrea alluded to it in a previous post, I have to mention that a month ago I sprained my left wrist when I rode the top of a ladder to the ground...backwards and downwards, and slam. I have missed my left hand terribly and promise to never take it for granted again if it works with me on the physical therapy and retains full functioning. Lawyers need not contact me, as the staff here and NHM human resources department have been caring and accommodating.
Oh, and FYI: We've completed excavation of Box/deposit 10B; our first box finished. It went pretty fast because it was a disturbed (mostly fallen apart) deposit and we did not measure out any bones or use a grid system on it. We will not, be changing the project name to Project 22, but the thought crossed our minds.
1. the feminine form of excavator; a woman employed to dig out earth 2. the semi-official blog of the excavators and excavatrices at the La Brea Tar Pits in Los Angeles, CA.
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