HARRISON LAKE FOSSIL COLLECTING

Cadoceras (Paracadoceras) tonniense

Most folk headed to Harrison Lake are venturing the three hours east of Vancouver to enjoy the hot springs, play out on the lake or take in the rugged scenery. A few also come to look for the elusive Sasquatch reported to live here.

But there are some who come and miss the town completely, instead favouring the upper west side of the lake and their fossiliferous bounty.

It is here that many wonderful marine fossil specimens can be found. When you look through the outcrops, what you will find embedded in the rock are their often warped or partially crushed fossilized, mineralized shells — millions of years old. 

It is truly amazing that we find them at all. These beauties are from the Lower Callovian — meaning, they swam our ancient oceans 164.7 - 161.2 million years ago. 

A wee handful — This lovely partially crushed ammonite is Cadoceras (Paracadoceras) tonniense (Imlay, 1953). 

These small, often incomplete brown and grey ammonites can be found at one of my favourite outcrops in the Jurassic macrocephalites macrocephalus ammonoid zone of the Mysterious Creek Formation near Harrison Lake, British Columbia. 

It is interesting that almost all of the ammonite specimens found here have well preserved outer whorls but flattened inner whorls. It makes one suspect if it is related to what was filled with sediment and what was open space within the shell at the time of burial. 

Elliptical specimens are found here, too — showing evidence for the depth and tectonic strain the rocks were subjected to. Take a good look at the photos to set your search image. You are looking for the dark grey rock with the fossils showing up either dark grey, grey-brown or black.

Ammonites were predatory, squidlike creatures that lived inside coil-shaped shells. Like other cephalopods, ammonites had sharp, beak-like jaws inside a ring of squid-like tentacles that extended from their shells. They used these tentacles to snare prey, — plankton, vegetation, fish and crustaceans — similar to the way a squid or octopus hunt today.

Harrison Lake, Forestry Road #17

Catching a fish with your hands is no easy feat, as I am sure you know. But the Ammonites were skilled and successful hunters. They caught their prey while swimming and floating in the water column. 

Within their shells, they had a number of chambers, called septa, filled with gas or fluid that were interconnected by a wee air tube. By pushing air in or out, they were able to control their buoyancy in the water column. 

They lived in the last chamber of their shells, continuously building new shell material as they grew. As each new chamber was added, the squid-like body of the ammonite would move down to occupy the final outside chamber.

Interestingly, the ammonites from the Harrison Lake locality are quite similar to the ones found within the lower part of the Chinitna Formation, near Cook Inlet (Tanaina: Tikahtnu; Sugpiaq: Cungaaciq) Alaska and Jurassic Point, Kyuquot, on the west coast of Vancouver Island — some of the most beautiful places on Earth. 

Geologic Hammer for Harrison's Hard Matrix

Most folk visiting Harrison are here for the hot springs or to kayak the crisp waters of the lake. I venture the three-hours east of Vancouver for the rock and the fossils they contain. 

The area you are exploring for geology and palaeontology around Harrison Lake has been home to the Xa'xtsa First Nation for thousands of years. 

Theirs is a band government of the In-SHUCK-ch Nation, a subgroup of the larger St'at'imc — also referred to as Lower Stl'atl'imx. Xa'xtsa is made up of two communities: Port Douglas, situated at the northern end of Little Harrison Lake, and Tipella, on the west side of the Lillooet River.

These species are from Callomon's (1984) Cadoceras comma Fauna B8 for the western Cordillera of North America, which is equivalent in part to the Macrocephalus Zone of Europe of the Early Callovian. 

The faunal association at locality #17 near Harrison suggests a more precise correlation to Callomon's zonation; namely, the Cadoceras wosnessenskii Fauna B8(e) found in the Chinitna Formation, southern Alaska (Imlay, 1953b). The type specimen is USNM 108088, from locality USGS Mesozoic 21340, Iniskin Peninsula, found in a Callovian marine siliciclastic in the Chinitna Formation of Alaska.

Exploration of the geology around Harrison Lake has a long history with geologists from the Geological Survey of Canada studying geology and palaeontological exposures as far back as the 1880s. They were probably looking for coal exposures and where to route the planned Canadian Pacific Railway — or perhaps sought a glimpse of the wily but shy local Sasquatch — but happily, they found fossils.

The paleo outcrops were first mentioned in the Geological Survey of Canada's Director's Report in 1888 (Selwyn, 1888), then studied by Whiteaves a year later. Whiteaves identified the prolific bivalve Aucella (now Buchia) from several specimens collected in 1882 by A. Bowman of the Geological Survey of Canada. 

The first detailed geological work in the Harrison Lake area was undertaken in a doctoral study by Crickmay (1925), who compiled a geological map, describing the stratigraphy and establishing the formational names, many of which we still use today. Crickmay went on to interpret the palaeogeography and structure of the region. 

Click to Enlarge

Around Harrison Lake, Callovian beds of the Mysterious Creek Formation are locally overlain disconformably by 3,000 feet of the Early Oxfordian conglomerate. Here we find the cigar-shaped squid-like cephalopod Belemnites, the bivalve Buchia and the ammonite Cadoceras tonniense, as well as others. 

Interestingly, we also find Cadoceras tonniense at nine localities hundreds of kilometres north of here along the Alaska Peninsula and within the Cook Inlet region of the United States.

If you would like to visit the site at Chinitna Bay, you'll want to hike into 59.9° N, 153.0° W: paleo-coordinates 31.6° N, 86.6° W.

If you're a keen bean for the Canadian site, you can drive the 30 km up Forestry Road #17, stopping just past Hale Creek at 49.5° N, 121.9° W: paleo-coordinates 42.5° N, 63.4° W, on the west side of Harrison Lake. You'll see Long Island to your right. 

If you can pre-load the Google Earth map of the area you will thank yourself. This site is a great day trip from Vancouver or the Fraser Valley. 

You will need a vehicle with good tires for travel on gravel roads. Search out the route ahead of time and share your trip plan with someone you trust telling them where you are going and when you plan to be back. 

Access Forestry Road #17 at the northeast end of the parking lot from the Sasquatch Inn at 46001 Lougheed Hwy, Harrison  Mills. Look for signs for the Chehalis River Fish Hatchery to get you started. NTS: 92H/05NW; 92H/05SW; 92H/12NW; 92H/12SW. 

The first of the yummy fossil exposures (that are easily collected) are just north of Hale Creek on the west side of the road. There is active logging here so be very careful with kids and pets on the roadcut. Slides are also fairly common — and you may start a few if you hike the cliffs — so watch out for those below. Wear something brightly coloured so cars and trucks can see you. 

You will want to look both in the bedrock, in the loose material that gathers in the ditches and for large dark grey boulders the size of dishwashers packed with Buchia — sometimes made entirely of these densely packed bivalves. 

Buchia populated our Upper Jurassic and Lower Cretaceous waters like a team sport. When they thrived they really thrived, building up large coquinas of the material that make up much of the rock you will find at Harrison and other sites in the Northern Hemisphere. 

We use them as Index Fossils, fossils helpful for dating the age of rock because of their abundance and relatively short stratigraphic range, ie. they lived well, populated an area en masse then died out quickly — the ideal biostratigraphic index fossil.

What does that mean to you? Well, when you are out and about with friends and discover rocks with Buchia or made entirely of Buchia, you can casually say, "oh, this looks to be Upper Jurassic or Lower Cretaceous. Guys, come take a look. We're likely the first to lay eyes on this little clam for more than 160 million years." You'll impress the pants off them. Very high-five worthy.

And on a geeky language note, know that it gets easier. If you had never seen an apple and overhead folk talking about Granny Smith, Ambrosia, Gala or Honeycrisp, your eyes might glaze over. But consider how much knowledge you have that is specialized. You didn't study for it but just picked it up because you find it interesting. 

Think of your knowledge of sports teams, boats, cars, Star Wars or the Marvel Universe. You know things, so many things. You'll find your inner fossil geek in time — probably with your first find. And that's the tip of the iceberg; first you, then your kids, your friends, your neighbour. Once you start is it easy to get hooked on the goodness. Fossil addiction is real and the only cure is to embrace your geek, get out there and do it. You've got this!

WHAT TO BRING:

As with all trips into British Columbia's wild places, you will want to dress for the weather. This is a good site for hiking boots, raingear, gloves, eye protection and a good geologic hammer and chisel. Fill your gas tank and pack a tasty lunch. You will definitely want to bring your camera for the blocks of Buchia too big to carry. If you take some good photos, I would love to see them. 

Wear bright clothing and keep your head covered. If it is a larger group, those collecting below may want to consider hardhats in case of small rock falls. These are most often chunks of rock the size of your fist up to the size of a grapefruit — and they pack a punch. 

Bring a colourful towel or something to lay your keepers on. Once you set down a rock, it is hard to find that keeper pile again as they often blend into the surroundings. I take the extra precaution of spraying the ends of my hammers and chisels with yellow fluorescent paint as I have set down too many and ended up leaving them in the field. I also always throw one of those lightweight yellow construction vests over whatever I am wearing so my crew and cars can spot me.

When you have finished for the day, you can compare your various treasures to see which ones you would like to keep. In British Columbia, you are a steward of the fossil, meaning these all belong to the province but you can keep them safe though cannot sell them or ship them outside British Columbia without a permit. You should be all set to celebrate a glorious day in the beautiful outdoors.

I have been asked about collecting four seasons. What do we do about the weather? We live in a rainforest so collecting in sun and rain means your field season is longer. Everyone has a preference. I prefer not to collect in the snow, but I have done. While sunny days are lovely, it can be easier to see the fossil specimens at Harrison when the rock is wet. So, do we do this in the rain? Heck, yeah. 

Torrential rain? You, yes, once you're good and hooked. A casual friend or your kids, no. Choose your battles. A solid eight hours in the rain is on the losing end. They may come, but they'll likely never join you again — or speak to you.

Once you get home you can wash and ID your finds. I have put the scientific names here but if they occur as gobblygook, don't worry. Harrison does not have a huge variety of fossil fauna. Essentially, if your find is coiled and round, it is an ammonite. If it is long and straight, it is a belemnite. And if it looks like a wee fat baby oyster, it is Buchia. That is not always true, but it is mostly true. 

If you find something you cannot ID, send me a photo on the Fossil Huntress Facebook page and I will help you to identify it.

Oh, and do be on the lookout for anything that looks like bone. This site is ripe for finding a marine reptile. Think plesiosaur, mosasaur, elasmosaur, you get the idea. Maybe the next Indiana Jones to get a new species named for them is you!

• A. J. Arthur, P. L. Smith, J. W. H. Monger and H. W. Tipper. 1993. Mesozoic stratigraphy and Jurassic palaeontology west of Harrison Lake, southwestern British Columbia. Geological Survey of Canada Bulletin 441:1-62
• R. W. Imlay. 1953. Callovian (Jurassic) ammonites from the United States and Alaska Part 2. The Alaska Peninsula and Cook Inlet regions. United States Geological Survey Professional Paper 249-B:41-108
• An overview of the tectonic history of the southern Coast Mountains, British Columbia; Monger, J W H; in, Field trips to Harrison Lake and Vancouver Island, British Columbia; Haggart, J W (ed.); Smith, P L (ed.). Canadian Paleontology Conference, Field Trip Guidebook 16, 2011 p. 1-11 (ESS Cont.# 20110248).