What's up at Wapiti River?

The world can always use some more Pachyrhinosaurus bonebeds. So hooray to my friends and colleagues Federico Fanti and Mike Burns, and my PhD supervisor Phil Currie, for publishing a description of the Wapiti River Pachyrhinosaurus bonebed (currently in 'early view' accepted manuscript form at the Canadian Journal of Earth Sciences).

A friendly Pachyrhinosaurus lakustai greets students at Grande Prairie Regional College!

Most of the time, dinosaur palaeontologists look for bones in dry, barren landscapes – the badlands of Alberta, the Gobi Desert, etc – places that have lots of rocks and not much covering them up, like inconvenient forests or cities. But sometimes, you don't have vast expanses of outcrop. In Nova Scotia, we dig up dinosaurs on the beach. In the area around Grande Prairie, Alberta, you look for bones in the outcrops along rivers and streams.

The very first summer I went out with the University of Alberta crew (way back in the halcyon days of 2007; the first Transformers movie was 'good', everybody read the last Harry Potter book overnight to avoid spoilers, and...apparently not much was happening in my musical spheres, but my, how time has flown), there wasn't a Wapiti River bonebed. We knew that there were bones coming out of the riverbank somewhere, but it took the better part of a day to trace them up the hill to the bone layer. 

See if you can spot Phil for scale way up on the hill there, and remember that Phil is about 3x as tall as most humans. That's where the bone layer is!

It's a pretty steep hill, and so those first few days excavating the bone layer meant hacking out little footholds and gradually making enough of a ledge for us to sit on and walk around each other without plummeting to our death.

The last time I was there, in 2011, the ledge had expanded significantly, although you can see it's still a pretty narrow slice! It's a scenic place to work, with the river and boreal forest stretching away below; bear sightings were not uncommon (and occassionally closer than we'd all prefer), and I remember a hummingbird came down to check on us one day, buzzing around my head for a few moments!

In this bonebed, there's a layer of bones in a crazy, mixed-up layer of folded mudstones, and those are pretty easy to excavate. 

Here's a dorsal vertebra. Nice and easy.

But down beneath that, the skulls and larger bones are encased within super hard ironstones. We can't really do much with these in the field, so we need to take them out in huge pieces. 

And here's what the skulls look like. The circular depression down towards my left foot is the narial opening. The UALVP has like 15 of these suckers and they each take about 2 years to prepare with a crack hammer and chisel.

But the bonebed is also about halfway down into the river valley on a steep slope that's hard enough to just haul yourself up, let alone a huge boulder. So we've been very lucky to have helicopter support to carry out some of the heaviest pieces at the end of each field season.

Up, up and away!

Sometimes we were even visited by Aluk the Pachyrhinosaurus, mascot of the Arctic Winter Games in 2009!

This was probably the strangest day in the field.

There's still much more work to be done on this bonebed – we still aren't exactly sure what species of Pachyrhinosaurus is present. The age is right for P. canadensis, but only time will tell. And with two Pachyrhinosaurus bonebeds in Grande Prairie – the Pipestone Creek bonebed with P. lakustai, and the slightly younger Wapiti River bonebed – there's bound to be much more to learn about the evolution and biology of this unusual ceratopsian. 

Previously in Pachyrhinosaurus:
Wapiti River Fieldwork, Part 1
Wapiti River Fieldwork, Part 2

And don't forget to check out:
Fanti F, Currie PJ, Burns ME. 2015. Taphonomy, age, and paleoecological implication of a new Pachyrhinosaurus (Dinosauria: Ceratopsidae) bonebed from the Upper Cretaceous (Campanian) Wapiti Formation of Alberta, Canada. Canadian Journal of Earth Sciences, early view.

The Great Canadian Dinosaur Hunt

Dino Hunt Canada is almost here! Starting this Friday, History Channel Canada will be airing a series of hour-long documentaries devoted to dinosaur expeditions all across Canada - and not just in the famous badlands of Alberta! The production crew visited field localities in Nova Scotia, Saskatchewan, multiple places around Alberta, and British Columbia. It's going to be a real who's who and where's where of Canadian palaeontology.

I'll be in the second episode featuring work in Dinosaur Provincial Park, which we filmed in 2013. It was a fun if somewhat unusual experience to have such a large film crew with us, and I'm looking forward to seeing the whole shebang!

What was the crew filming in DPP? Tune in to find out!

There's also a really excellent website to accompany the show. You can learn more about some of the dinosaurs featured in the series (including wonderful new artwork by Danielle Dufault!), see interviews with some of the palaeontologists, and submit ideas for a nickname for a new dinosaur excavated during the show by the Southern Alberta Dinosaur Project. You can even submit questions and maybe have my weirdo face answer them via Skype! All in all, it's looking really good so far and I'm so happy to see the huge variety of dinosaur research being conducted across Canada by so many talented and hardworking people.

Cock-a-doodle-doo

I've finally got the time and gumption to sit down and write again, so let's do some research blogging! And let's show some skin while we're at it!

The first paper I'll talk about is not one that I'm lead author on, but which was a really fun project to be involved in. This was the description of a super cool specimen of a hadrosaur from the area around Grande Prairie with some impressive skin impressions. UALVP 53722 was collected as a large block that had fallen along the creekside. Unfortunately, the rest of the skeleton could not be located, which might mean it's still in situ somewhere with nothing visible, or it had already broken apart into unrecognizable pieces. The block preserves the back of the skull with the neck arched over the shoulders, the classic 'death pose' seen in many dinosaur skeletons. Most of the skull is missing, but what is present shows that it is an Edmontosaurus regalis, the slightly older species of Edmontosaurus. 

Flat-headed Edmontosaurus at the Denver Museum of Nature and Science.

And sitting on top of the skull is a round, relatively smooth lump of soft tissue, like the comb on a rooster's head. 

My primary contribution to the paper was to examine the CT scans of the specimen to confirm that there wasn't a bony structure within the crest, so that we could be confidant that it truly was a soft tissue structure only. The UofA put together a short video about CT scanning the fossil that is worth a watch:

The fleshy comb in UALVP 53722 the first time we've seen anything like this in a dinosaur, and was totally unexpected – Edmontosaurus is one of the 'flat-headed' hadrosaurs that lacks the bony crest characteristic of lambeosaurines like Corythosaurus or Lambeosaurus. I love this discovery because it is such a great example of how much soft tissues contribute to the appearance of an animal. It also goes to show how a new fossil, even for a relatively well known dinosaur like Edmontosaurus (which is known from many skeletons and bonebeds) can still give us new information. 

Crested Edmontosaurus based on UALVP 53722.

I was also a big fan of the book "All Yesterdays", and I feel like this specimen kind of fits in with some of the more adventurous reconstructions of dinosaurs with elaborate soft tissues that have become more fashionable of late. And like all good discoveries, we end up with more questions that need to be answered: did all Edmontosaurus regalis have this fleshy comb, or was it restricted to adults, or even just adult males? If males and females both had the comb, was it larger in one sex than the other? Was it brightly coloured? Did Edmontosaurus annectens have a fleshy crest? We'll only be able to answer these questions with more specimens.

Anyway, go check the paper out! UALVP 53722 was on display in Edmonton for a short time earlier this year – stay tuned for more information on where it will be on display next! Many thanks to Phil Bell (a former Currie Lab student and now at the University of New England in Australia) for inviting me to help out with this paper.

Bell PR, Fanti F, Currie PJ, Arbour VM. 2014. A mummified duck-billed dinosaur with a soft-tissue cock's comb. Current Biology 24:70-75.

Horner JR. 2014. Paleontology: a cock's comb on a duck-billed dinosaur. Current Biology 24.

And for those who are extra keen, here's my Quirks & Quarks radio interview from January 2014.

Let's Build the Currie Museum!

A message from my colleague Dr. Phil Bell:

Hi all,

 

Some of you are already aware of the Philip J. Currie Dinosaur Museum, which is scheduled to be built in Grande Prairie, but certainly all of you are aware of Philip Currie himself. As part of the final push to raise the remaining construction funds, we have launched a crowd-fundraising campaign on www.indiegogo.com/curriemuseum. The aim is to raise $1,000,000 in 120 days. In the first hour alone, we raised $1,600!

 

Every donation, no matter how small, is important and donors are rewarded with a range of increasingly cool gifts including a museum logo pin, t-shirts, and original artwork by palaeo-art master Julius Csotonyi. It's all outlined on the website, so please check it out, spread the word, and help us build a world-class museum and research institute.

Many thanks!

 

Phil Bell

Head Palaeontologist

Pipestone Creek Dinosaur Initiative

 

 

 

The Philip J. Currie Dinosaur Museum has been working hard to raise funds for the construction of the museum, which will showcase fossils from northwestern Alberta and support research and education on Albertan dinosaurs. They've raised $17.4 million of the $30 million needed. Even without a museum building, the crew from the Currie Museum is doing an incredible amount of education, outreach, and research. Just last week, Phil visited the University of Alberta to CT scan a hadrosaur with skin impressions from Red Willow Creek. But it can only continue if the museum is funded and built. Please support the museum - they are good folks up there, and every little bit helps!

 

Aluk the Pachyrhinosaurus visits the Wapiti River Bonebed in 2009.

 

Hadrosaur mummies have been collected along Red Willow Creek.

 

New fossil lizards have been described from Kleskun Hills, the northernmost outcrops of badlands in Alberta.

The Wapiti River Pachyrhinosaurus bonebed has been excavated each year since 2007. We're still preparing material from that bonebed in order to figure out which species of Pachyrhinosaurus we have!

 

Thoughts on Tarbosaurus, Part 3

Previously in this series on the poached Tarbosaurus skeleton, I've discussed the role of museums in fossil collecting, how the specimen was identified as Tarbosaurus, and how we know the skeleton came from Mongolia. Today, I'll discuss one final question: Why is fossil poaching such a big deal, anyway?

(Various museum trips, manuscript deadlines, and fieldwork in Dinosaur Provincial Park have kept me from returning to the blog as quickly as I had hoped, and much has transpired in the Tarbosaurus case in the last few weeks; in particular, see Phil Currie's article in New Scientist. Hopefully, posting will become a bit more frequent, and optimistic, in the next little while.)

To me, it seems obvious why fossil poaching is a big deal (in a bad way) - it reduces or removes access to fossil specimens, and reduces or removes important information about that fossil. First, let's talk about access to fossils. As I discussed in part 1 of this series, the role of museums is to conserve artifacts for present and future generations; additional responsibilities include facilitating research and education, and usually involve displaying objects to the public. Private owners of fossils have no such responsibilities. Some private collectors may choose to display some of their fossils to friends and family, or may even open their private residence to visitors. But they don't have to, and most fossils held by private collectors are probably only ever seen by a handful of people. For really common, super-abundant fossils, perhaps this is not a terrible thing. Vertebrate fossils are rarely common and abundant, and each specimen often has important information to contribute to the study of any particular organism.

A second point about access that is probably not widely known is that palaeontologists cannot really study or publish on privately-held fossils. This is because other palaeontologists may not be able to access those specimens to verify the original palaeontologist's findings, and so therefore the science would not be reproduceable. There are probably lots of instances where private collectors have made substantial contributions to museum collections by donating their discoveries or purchases, but while the specimen is privately held, it is, for all intents and purposes, 'invisible' to the scientific community. A specimen that cannot be published in the scientific literature does not contribute to our understanding of the fossil record, and represents lost knowledge. This is why it is important for fossils to be in recognized institutions like museums or university collections, so that palaeontologists (and the public!) can study the material and use it to better understand our world.

Next, let's talk about how poaching reduces the information content of fossils. Fossils do not exist in a vacuum. The sediments encasing a fossil are nearly as important as the fossil itself, as these provide at least two crucial pieces of information about the fossil: 1) how old it is, and 2) what the depositional environment was. Interpreting the age and depositional environment of a rock is not always easy, and requires specialized training in geology in order to be done properly. When a fossil is yanked out of the rock with no attention paid to where or how it was found, important information is lost.

Pop quiz! Is that the Nemegt or Baruungoyot Formation?

Finally, and most obviously, poaching can damage the fossils themselves, if the poachers do not have the appropriate tools or training to properly excavate the fossils. The more a fossil is broken, the more information is lost. Collecting fossils is tricky, difficult work that requires a lot of patience and strength. Without the right tools and people, fossils get broken. Amateur or commercial collectors may be excellent record-keepers and skilled excavators, and so this may not be a problem - but from my experience at least in Mongolia, poachers don't seem to be really good at collecting the dinosaurs they aim to sell.

 See those white bone fragments there? Those used to be a Tarbosaurus skull.

I hope the attention given to the Tarbosaurus auction marks the beginning of the end of fossil poaching in Mongolia, although I suspect I may be being overly optimistic with that sentiment. But fossil poaching and destruction is not limited to Mongolia, as evidenced by a tragic story that happened basically in my backyard this week. A few weeks ago, the University of Alberta and Pipestone Creek Dinosaur Initiative field crews found a beautiful hadrosaur skeleton, with skin impressions, along the Red Willow River near Grande Prairie. The PCDI team was excited because this would make for a great display specimen (not to mention it being a scientifically important specimen) for the museum they are working very hard to get funded and built. Earlier last week while in Dinosaur Park, we received the terrible news that the partially-excavated, plaster-jacketed specimen had been vandalized and severely broken. We're not sure who did it or why. Even earlier in the summer, an in situ display of the Pipestone Creek Pachyrhinosaurus bonebed had been smashed and vandalized as well.

In Alberta, excavating fossils without a permit, or damaging fossils, can get you a $40 000 fine and/or a year in prison. Nowhere else in Canada has fossil protection laws as good as Alberta's, and in no other province is the general public as widely educated about fossils. Fossils are everywhere in Alberta, we have an abundance of museums and public outreach, several universities conduct palaeontological research, and there's an active amateur society. And STILL people feel the need to wreck our fossils - no, scratch that, THEIR fossils. I find this intensely discouraging, and I don't have a good solution.

Given the recent international attention on the Tarbosaurus case, I hope Alberta sets a good example by prosecuting the fossil vandals to the fullest extent possible, if they are able to catch them. At the very least, I hope that this provokes a renewed interest in protecting our amazing fossil resources. Wherever you're from, support your local museums and universities, and be interested in the natural world around you. It will take all of us working together to protect it.

Cool Stuff

"Cool Stuff: The University of Alberta Museums Do Winter" is a winter-themed exhibit that opened last week at the U of A's Enterprise Square location. I checked it out last weekend and was pleased to see so many different types of objects on display. We have 28 different collections on campus, and most (maybe all?) were represented in the exhibit - butterflies, moss, picked parasites, textiles, and more. 

The University of Alberta Laboratory for Vertebrate Paleontology contributed fossils from our Grande Prairie and Edmonton dinosaur bonebed excavations. Although we usually collect stuff in the summer, we've had snow during our Edmonton fieldwork, even in May.

We showed off some field jackets, too. The Monoclonius and ornithomimid are pretty self-explanatory, and if I recall correctly, "Skull B" is from the Wapiti bonebed in Grande Prairie. There were also photos from our December tyrannosaur helicopter lift in Dinosaur Provincial Park, including a photo taken by me!

Last spring we purchased a cast of the Cryolophosaurus original non-reconstructed skull for both teaching and research, but it fit in perfectly with the exhibition theme! The grey slab behind the skull is the Wonder Block from the MOTH locality, which has a variety of 'jawless fish'. Phil will be giving a talk about his 2011 Antarctic expedition on March 1, as part of the exhibition's speaker series.

The exhibition also features specimens from our zoology collections, including these Arctic and sub-Arctic mammals (caribou, deer, and walrus).

"Cool Stuff" mixes natural history objects with cultural heritage objects, and in particular I was pleased to see so many Inuit and Inuvaliut art pieces. I am always astounded by whalebone sculptures like this one.

Another display had Inuit dolls, musical instruments, hunting tools, and boots. The beautiful paintings in the background are the original art from Ted Harrison's "A Northern Alphabet". Click the photo to make it bigger, and see if you can figure out what letter each painting represents.

"Cool Stuff" is open until March 4, and admission is free. It was cool, go check it out. 

Velociraptor-free, mostly...

For the last several years, our lab has run a volunteer fossil prep program on weekday evenings. As the school year starts again, I thought I'd share our recruitment poster for this year!

We are very fortunate to have two prep labs in the BioSci building at the University of Alberta. Our basement lab handles the larger, more complex specimens like skulls or partial skeletons. The fourth floor lab, shown here, is where volunteers help us get through the enormous quantity of smaller fossils we've collected. There's lots of table space and light, and with volunteers it becomes quite sociable in the evenings!

There's always at least one grad student or upper-year undergrad present who supervises the volunteers and teaches them prep techniques. Volunteers have come from many different departments at the U of A, not just the sciences! We also get the occasional volunteers from outside the university, who hear about us online or via posters we put up around town.

Volunteers help us prepare a wide variety of material from all over Alberta, including theropods, hadrosaurs, ceratopsians, crocs, turtles, and champsosaurs. A lot of the small material comes from Dinosaur Provincial Park and is fairly easy to prep (sometimes just require a good toothbrushing and some glue!), but we also have more challenging projects like specimens from our Wapiti River Pachyrhinosaurus bonebed in Grande Prairie. We also have material collected way back in 1921 that has never been prepared!

The beginning of the school year is always exciting and I hope we'll see a bunch of new and returning volunteers in the next few weeks. If you're interested in keeping up with the goings on in our lab, you can follow us on our Facebook page, Dino Lab at the University of Alberta.

Hugo's Boss

I almost forgot to mention a fun bit of news coverage that happened during our Grande Prairie fieldwork. The first Pachyrhinosaurus skull to be prepared from the Wapiti River bonebed was nicknamed Hugo (for I hope obvious reasons...). It is on loan to the Grande Prairie Regional College for the next few months and is on display in a case beside their bookstore. The Grande Prairie Daily Herald-Tribune did a nice little piece on the new display and features a completely awesome photo of Phil Currie and prep technician Susan Kagan.

Susan has been pummeling her way through the hard ironstone nodules that enclose the Wapiti River skulls - here is a photo from last fall of progress on the next skull to be prepared. It's come a long way since then, but it takes a long time to get these guys ready.

Grande Prairie Regional College also has a full skeletal mount of Pachyrhinosaurus lakustai, the species known from the Pipestone Creek bonebed.

Ok, that should actually be the end of Pachyrhinosaurus updates for the next little while...

Pipestone Creek Bonebed

The area around Grande Prairie is rich with dinosaur fossils, although the setting is somewhat different than you might expect if you're used to working in badlands like Dinosaur Provincial Park. In Grande Prairie, the only badlands outcrops are the Kleskun Hills, and most other sites are found along creeks and river valleys. I spent the bulk of my time at the Wapiti River bonebed, but helped out a little bit at the concurrent excavation at Pipestone Creek.

The Wapiti River bonebed has yet to be described, but Pipestone Creek is a fairly famous locality because of the huge numbers of Pachyrhinosaurus that were collected there during the late 80s by the Royal Tyrrell Museum and featured in the touring exhibition Dinosaur World Tour: The Greatest Show Unearthed. This bonebed was reopened last year as plans for the new museum to be built in the area began to solidify. In 2008 the animals in this quarry were separated from Pachyrhinosaurus canadensis (found in southern Alberta), and named Pachyrhinosaurus lakustai after Al Lakusta who discovered the bonebed.

Although material from the Wapiti River and Pipestone Creek bonebeds are currently accessioned at the University of Alberta, we've had a lot of help from the Grande Prairie Regional College, who have helped with many of the logistics of working in the area and allow us to stay at their dorms (it sure is nice to have kitchens, showers, and proper beds).  Here's a few photos from the last days of this year's fieldwork at Pipestone Creek.

 

The Pipestone Creek bonebed is incredibly dense, and I've been told that upwards of 100 bones have been found in a single square meter here. We were particularly excited this year because a very fine P. lakustai skull was uncovered, which you can see here as the large jacket. We had to jacket a bunch of smaller bones along with it because they sit partially underneath the skull and could not be removed. They'll be extracted back at the lab.

Here the skull has been flipped and the crew jackets the underside in preparation for transport. Pipestone Creek is a much easier site to access than Wapiti River. As you can see, the bonebed is not far above the creek, and a road has been constructed to allow visitors an easy walk to the site.

Helicopters are essential for getting large-ish jackets out of the Wapiti River bonebed, since the hill is too steep and high to easily get large jackets up to the edge and into the truck, or down to the river and into jetboats. This year, the helicopter was also a much needed tool for getting the large skull jacket out of Pipestone Creek. Here it sits in a field at the campground after three successful lifts.

We were a little apprehensive about getting the large skull into the truck, but luckily a crane was in the area and happy to help us out. The driver weighed the jacket - it came out at a whopping 1200 lbs! Too bad we didn't have a crane for getting it out of the truck once we were back at the university...

 

I'll probably have more updates as some of this material is prepared at the U of A, but that concludes my Grande Prairie fieldwork for this year. You can keep up to date with the goings on up there by keeping an eye on the museum project, formerly called the River of Death and Discovery Dinosaur Museum and recently been renamed the Philip J. Currie Dinosaur Museum. They have a pretty nifty new website (and blog, which you can find on the blogroll here).

Wapiti River Fieldwork, part 2

Here's a few more shots from the University of Alberta's fieldwork at the Wapiti River bonebed near Grande Prairie. Fieldwork wrapped up on Friday and the fossils are now at the U of A awaiting preparation.

It continues to amaze me just how much we have cleared out of this ledge over the last five years - when we started, the ledge did not exist.

I've learned that different field crews use different methods for mapping quarries. At the U of A, we use a baseline, grid square, plumb-bob and gridded paper to mark the location and orientation of bones in the quarry. (Sometimes it gets a little crowded, but people's heads make good supports for the grid square.) The grid square is a square meter, divided into 10x10 cm quadrants. The baseline is marked at 1 m increments along its length, and the grid square is lined up at the relevant marks. If the grid square is very high above the elements you want to map, a plumb-bob is useful for reducing parallax error. Each bone is marked with quarry coordinates, and eventually all of the map sheets are combined in photoshop or illustrator. The maps will help us to understand the taphonomy of the site.

We almost never find teeth at this site, but this year we recovered 2 or 3 ceratopsian teeth and 2 or 3 tyrannosaurid teeth. Here's one of the ceratopsian teeth, which you can see as a small triangle in the middle of the orange splotch.

Here's a Pachyrhinosaurus skull we helicoptered out on the second last day. It may not look like much, but I think this is one of the nicer ones we've gotten out of this quarry. You can see a large circle to the left that is probably the orbit. Because the block is already broken into smaller nodules, we jacketed the skull as multiple blocks to make arranging for the helicopter nets a little bit easier. The edges of all of the separate nodules were marked before jacketing so we can piece everything back together in the lab.

Wapiti River fieldwork, part 1

Hi everyone! It's been a while since my last post as I catch up on research and get ready for a brief stint of fieldwork in Grande Prairie. I've been working at the Wapiti River bonebed for the last few days, where we are excavating a Pachyrhinosaurus bonebed. Here is a quick update of what we've been up to.

The bonebed is on a steep river side, and we have cut a long but narrow ledge into the cliff. The view is quite spectacular and we occasionally see deer and bears on the other side of the river. 

Ropes are helpful for getting up and down the steep cliff!

The bonebed includes two distinct preservational types - hard bones that separate well from twisty shaley mudstones, and hard, hard nodules containing mostly skull bones. You can see the skull nodules below Angelica, as she works in the mudstone layer.

It can be rather goopy in the quarry and the bones are often cracked with mud in between the pieces, so we often map the bone and then remove it completely to clean and glue before we jacket for transport. The bones look quite good once they are clean and put back together! I am pointing at a skull element I found on my first day here.

More to come soon!

River of Death gets a name change.

I haven't talked a whole lot here about the Pipestone Creek Dinosaur Initiative or the proposed River of Death and Discovery Museum. The area around Grande Prairie, Alberta, about a five hour drive northwest of Edmonton, is rich in Late Cretaceous fossils. The most famous locality is Pipestone Creek, where hundreds of the horned dinosaur Pachyrhinosaurus perished millions of years ago.

For nearly ten years, a dedicated group of folks in Grande Prairie have been trying to get their own palaeontology museum off the ground. The working name for the museum was the River of Death and Discovery Dinosaur Museum. However, the word 'death' in the museum name has made it difficult for the museum to get as many sponsors as they would have liked.

And so it was announced yesterday that the museum would be renamed to the Philip J. Currie Dinosaur Museum! You can read more about the name change at the Grande Prairie Daily Herald-Tribune's article.

There are some exciting things coming up this summer for the museum foundation, including the Akroyd Family and Friends Dinosaur Ball (yes, those Akroyds!), and the University of Alberta will return to our annual excavations at the Wapiti River Pachyrhinosaurus bonebed and the newly-reopened Pipestone Creek bonebed.

A helicopter approaches at the Wapiti River bonebed during the 2009 excavation. Helicopter lifts are the only way the large blocks can be brought up to the edge of the river valley.