I wrote this a couple of months ago, but as usual, the spring semester got ahead of us! Here's the second installment covering our whale excavation this past winter. There will be two more installments and I'll try not to let them be spaced out quite so much!
Day two, continued: Panic and decision making in the field
When it comes to finding bone while digging – I’d rather have a clean break from removing a large block than something being chiseled through. One of the challenges we faced is that the bone at this excavation was so porous that it tended to just crumble when you got close to it – which is why Sarah exposed so much of the mandible using only a toothbrush. We didn’t have time to be so painstakingly slow, so we opted to find the edges of the bone scatter and just start trenching – digging blind, so to speak.
What are the advantages of “field prep”? You leave the field knowing precisely what you’ve found, and on a more important level, have much less to carry out in terms of mass: there is less rock in each field jacket. The disadvantages, I believe, outweigh these advantages – at least in my own experience. The first is time. I’ve always been in charge of or a party to relatively poorly funded field programs (dinosaurs tend to get all the big bucks, sadly) – none of which have the time to painstakingly excavate a skeleton in situ for weeks. We, on average, have perhaps 10% of the available time since we’re usually doing this on everyone’s day off (field trip leader included) or on an actual work day and avoiding teaching/grading/exam writing etc.
The "Fordyce method" of quickly excavating large fossils in soft limestone with students and power tools: 1) (upper left) have the young folks (students and preparator; undergrad Marcus Richards, left; preparator Sophie White, in green hat; Ph.D. student Felix Marx, right) carefully expose bone and uncover the edges of the bone scatter. 2) (upper right) - carve an outline about 2-3 feet away from the edges of the bone scatter - a 10-12" deep vertical cut with a chainsaw. 3) (lower left) Cut an inner cut, and a series of radial cuts that can be removed by students armed with picks. 4) (lower right) repeat this, going down one more layer, and then do an angled cut undercutting the block from all sides. We found this bone scatter at 9am, had the edges defined by noon, chainsawed by 3pm, and loaded up fully jacketed for the ride back to University of Otago by 5pm.
More power tools: the formidable, heavy, violent, but very effective Pionjar rock drill, here used on the South Otago coastline splitting apart large sandstone concretions. On left: Dr. Ewan Fordyce using the drill while then-Ph.D. student Yoshi Tanaka watches; right: then-PhD student Cheng-Hsiu Tsai (seated) and Ewan (in signature orange jumpsuit) use feathering wedges to split apart a thousand-pound concretion.
The advantages of finding the edges of a bone scatter and trenching ASAP is that you can quickly make a jacket by cutting out the time intensive ‘field prep’ stage – however, it does result in more and heavier jackets leaving the field, and requires more preparation (not an issue if the fossils are in relatively soft rock, anyway). In New Zealand, my experience in the Fordyce lab taught me the benefits of using power tools – we could dig up a 5 foot long jacket in about six hours or less, provided the whale (or penguin) was in the horizontal quarry floor – we would spend a couple hours finding the edge of the bone scatter, use a knife or chisel to mark the edges of the scatter – and the venerable Dr. Fordyce would take out a Stihl brand gas (er, petrol) powered chainsaw with a 3 foot blade and make three cuts: one vertical set of cuts at the edge of the bone scatter, another vertical cut about 12-16” out from that, and another cut 12” further out set off at an angle to make a wedge. The grad students would then spend about 15-20 minutes with picks to dislodge all of the sawn blocks. At the end of it, a relatively deep trench would be dug, and then the block would actually be undercut using the chainsaw rather than hours of painstaking – and back/neckache inducing – chiseling. Once undercut, we’d do one round of plastering, wait 20 minutes to cure, then proceed with chiseling – and in some cases, use the chainsaw again and literally just cut through the pedestal like a tree trunk. In one case we used the Pionjar rock drill – an incredible, but heavy, Swedish petrol-powered contraption that is a combination of a drill and jackhammer (and can be used as either) – it’s got a jackhammer bit that rotates about 30 degrees between each strike. After flipping the block, we often used a masonry saw to cut a grid into the excess rock from the base of the pedestal – which allows for quick removal of little 4x4” rock cubes, speeding up time otherwise spent on tiring chisel work by four or five times. On other occasions, we wheeled out a generator/air compressor into the quarry and used zip guns – basically like a giant airscribe (or, handheld jackhammer, for those of you unfamiliar with airscribes).
A typical assortment of tools - powered and otherwise - brought by Dr. Ewan Fordyce on a regular single day outing to quarries like Hakataramea Quarry, provided we knew we were going to be jacketing a whale. The chainsaw and associated gear is in the white tub on the left. Petrol powered masonry saw up in front, and petrol-powered compressor in back to power "zip guns".
The point of all this is that we didn’t have any of these tools available: we had hammers, chisels, picks, shovels, and whatever we could squeeze out of our muscles in a day’s work. By three in the afternoon, we were down to two people and had barely established a trench, and were no closer to having found the edges of the bone scatter. Worse, the sun was going down, and it was rapidly starting to cool off. I was rapidly becoming more and more anxious. Fortunately, the cavalry arrived: Ashby Gale swung by on his way back from Columbia and helped us pick up the pieces. I desperately needed a win – and I managed to isolate the periotic, and determined that there wasn’t much around it. I began to trench around it, and after about twenty minutes of careful – but nerve-wracking chiseling – I was able to remove a shoe-sized block of limestone, wrapped carefully in tin foil, that we were able to remove. By around 5pm, we had started mixing plaster- and we quickly applied three small plaster caps onto parts of the scatter, with the largest cap over the mandible to keep it protected. We also wrapped up the block of articulated (but fractured) thoracic vertebrae I “discovered” while picking with plaster. The temperature was, at this point, perhaps 55 degrees and rapidly dropping – and we plunged our hands into puddles of frigid muddy water in the quarry to clean off our hands. By 6pm it was 45 degrees and a light rain had started; we left the quarry chilled, soggy, overwhelmed and defeated – or at least I was. Retrieving the periotic was a small consolation prize.
The fruits of our labor from day 2: a few pitifully small plaster caps, and a small tin foil jacket with the earbone.
I thought a lot about this tactical defeat. Part of it, for sure, was going into it with a far too optimistic set of expectations – but also, my very first serious excavation where I was actually in charge: all of my excavations here in South Carolina have been small, one-day affairs – 2-4 hours to trench, undercut, and haul off blocks of limestone under 100 lbs. I’ve been in charge of smallish excavations that took several days in very difficult to access spots on the California coast – including the four-day long excavation of the Balaenoptera bertae holotype, a one day excavation with one assistant of a smallish plaster jacket containing a nice (and now published) skull of Parapontoporia, and a challenging two day excavation of a skull of Herpetocetus bramblei.
The last time I felt this overwhelmed was very likely June 2007 after trying to haul out a 150 lb jacket containing that Herpetocetus skull with my friend Chris Pirrone: we collected it ten feet above the beach and about 300 feet from the nearest route up the cliffs – a set of surfer’s “stairs”. Between the excavation site and the “stairs” were two small coves, the first filled with slippery boulders – which we began to navigate, but got blasted by a wave and dropped the jacket into the surf. I sat on a ledge at sundown, watching the incoming tide threaten the safety of the fossil (now entirely submerged), questioning my life choices, and wondering if the jacket would be recoverable at low tide tomorrow – and if the plaster would survive a night of tumbling in the surf. Chris encouraged me to continue, and we managed to wait for a gap between waves, grab the damp jacket, and approach a slippery rock ledge – and performed the second incredible feat of the evening: muscle this 150 lb jacket up an eight foot slope, covered in algae, without dropping the jacket, as waves were crashing down on our feet and legs. We had done it! The jacket was now out of the surf zone. Could we leave it over night? We were both cold and tired – but Chris, much like Samwise in Return of the King, encouraged me to press on.
The 2007 Herpetocetus dwarf baleen whale excavation: my second whale excavation. On left: me, at about 4pm, smiling like an utter dumbass, because I have no idea that the tide is coming in as quickly as it would and how unnecessarily difficult removing this tiny jacket would be. On right: removal of the jacket. 1) Location of the excavation, jacket flipped, finished, and cured by 6pm. 2) 6:30pm - jacket spends about 15 minutes underneath the Pacific Ocean while I evaluate my life choices. 3) 7:00pm, roughly: Chris and I, somehow, manage to carry jacket, now 50 lbs heavier thanks to waterlogging, up an 8 foot tall outcrop, the only one still accessible - as waves are crashing down on us, and we're waist deep in water, ankle deep between waves. 4) Roughly 8pm, after taking a bit of a breather and letting the jacket surface dry - we use a car mat to carry the jacket across this narrow ledge. The drop is about 8-12 feet, and there's now four-five feet of water down there. 5) 9-10pm: Chris and I manage to muscle the jacket with our last bits of rapidly fading strength, to lift the jacket up several shoulder to eye level surfer's stairs. Jacket in car by 10pm.
Our third impossible task was to navigate an 18” wide, 20 foot long ledge about 12 feet above the beach – now nearly high tide, so the water was about four feet deep here. This ledge was easily traversed with a surfboard or a regular field pack – but this jacket was nearly 30” across, and heavy enough that we would not have a free hand to steady ourselves. We would have to somehow get this jacket across in one shot without dropping it into the ocean or ourselves falling into the ocean. Chris went and grabbed the floor mat from his car – which we used as an impromptu stretcher, folding it up – we managed to shuffle across the ledge, ocean boiling below, without incident. Our fourth and final impossible task was to lift the jacket up the surfer’s stairs – in actuality a series of steps anywhere from two to five feet high. We managed several of the smaller steps, and failed several times on the final one – nearly at eye level, and getting the jacket 90% of the way there and then our muscles kept giving out. I finally proposed to put the flat side of the jacket vertical, and we would push it up and then into the wall when we needed to rest – inching it up a few inches at a time. We eventually got it to tip over the top – and let out victory cries! From there we used our last few shreds of remaining muscle fibers to lift the jacket into the back of my hatchback.
"I'd really like to go back to being a college professor". Funny at the time, entirely too relatable now. This marine crocodile was a similar situation: each time we went out, progress slowed more and more. Thermopolis Shale, south central Montana.
Now, that was a rough excavation: our defeat at Giant quarry was nothing in comparison. I had to remember that we had discovered – and not seriously damaged – a more complete specimen of Chrysocetus healeyorum – including the first earbones, good mandible, and periotic of the species (and only the second specimen). And, recovered the periotic. There was a lot of winning – but the rapid explosion in size of the fossil had really freaked me out. I was reminded of a seemingly never-ending excavation of a marine crocodile in September 2010 I had participated in – fellow master’s student Cathy Lash had discovered it in her field area in south Central Montana, and our adviser Dave Varricchio had offered to help excavate it. However, the shale became increasingly harder and more difficult to dig through – and one weekend became two weekends in the field, and it was approaching the end of September – and only half the skeleton had been uncovered. I recall Dave becoming increasingly frustrated, wanting help and commitment from Museum of the Rockies – and at one point said “I’d really like to get back to being a college professor”. I thought it was hilarious at the time – and I had lost research time for my own thesis and felt similarly – but now as a young professor and with a seemingly unending scatter of bone - I could really relate. [Eventually MOR sent a few people out to help the Earth Sciences Dept. field crew, and a few years later, the specimen was completely prepared and was out on display when we returned to Montana after our time in New Zealand].
Other concerns weighing on my mind were weather and quarry operations. We had found out that the mine would not be continuing mining activities on that ramp for about two months – which was admittedly plenty of time, enough time to ask if volunteers could dedicate about one day a week. With volunteers – people who have jobs they’re taking time away from to help us out – you’re simply not going to have several days commitment back to back. Nor could I actually afford that much time away from my own job. The benefits to spreading out collecting over many weeks are several: it keeps everyone fresh – myself included, as I went into this with an already mildly thrown out back – and keeps everyone from being burnt out. It also allows for some rain in between trips and gives the volunteers some nice fossils to go out and look for when they’re taking breaks – a good incentive since most collectors don’t have access to Eocene rocks in the area since they’re all in quarries, like Giant. However, it is winter now, and while December is not much colder than November, January and February are quite cold here – not as cold as our time in Montana, but certainly much colder than California.
Tabytha Wall's makeshift office in the back of Ashby's truck: she came out to help when we needed all hands on deck, but was saddled with a grant proposal deadline. I thought this was way too funny not to share.
Day Three - inching closer and closer
We returned the following Sunday with a slightly larger crew – Sarah, myself, Ashby Gale and his fiancée Tabytha Walls, CCNHM preparator Shelley Copeland, CCNHM curator Scott Persons, and Mark Bunce and Rich Familia. I returned guardedly optimistic – our major goal for the day was to finish trenching, apply a plaster jacket, and perhaps even flip the large block, and at minimum, remove some smaller blocks. We arrived slightly later – 10am – since the 9am day the week before was a bit on the early side, and it was still quite chilly. We lugged all the stuff up the hill and had a great morning – not much more bone was being found, and we were actually starting to excavate a bit of a trench. However, by 2 in the afternoon, I was beginning to realize that flipping the big block was not in the cards. Scott had to leave around 1pm or so, and Tabytha got screwed over at the office and needed to work in a makeshift office in the bed of Ashby’s truck to complete something a coworker failed to – so by 3pm we were back down to our skeleton crew again. I decided that at best we could define the margins of the jacket and apply a single top jacket on, and place the needed plaster caps onto the smaller pedestals. Rich had continued to work on his small pedestals – his “lumps” as we dubbed them – which contained some vertebrae. Late in the day, I started expanding the trench on the high side of the specimen and found another bone cluster – complete with a complete lower molar of our whale – but since all three lower right molars were in place in the jaw, this meant that it was a left lower molar. A few more mandible-looking fragments appeared, and we covered it up with some tin foil. By this time the sun was getting low, and we knew we needed to start getting ready to apply a plaster jacket. We used most of the remaining water up, and mixed nearly two whole 30lb bags of plaster – applying a large jacket over the main bone scatter, a patch on the newly uncovered tooth and bone scatter, and jacketed Rich’s two small pedestals. We were all done by about 4:30, and by 5:15 we had rinsed our hands off, put a tarp over the specimen, and packed everything back down the hill to the cars.
