 |
| Cory Brimblecombe, Tyaughton Fossil Beds |
Some of us had viewed the spectacular collection of Jurassic ammonites stored in the basement of the Geological Survey of Canada (GSC) Vancouver office.
Around 1993, I purchased a copy of the Geological Survey of Canada Bulletin 158, Hettangian Ammonoid Faunas of the Taseko Lakes Area of British Columbia by Hans Frebold. I recall wondering if I would even get a chance to visit such a remote locality.
As Karen Lund told me, “Tyaughton is kind of like El Dorado for the Vancouver Paleontological Society (VanPS).” Instead of immeasurable riches in gold, this region of the Chilcotin Mountains holds the treasures of time — bountiful fossils.
We had heard so many stories that this site was becoming somewhat legendary in our minds. In 2000, I made it a personal goal of mine to visit these remote fossil beds. Utilizing my resources as an undergraduate student at Simon Fraser University, I began researching all possible sources related to Tyaughton Creek. I dug up old GSC reports by Hans Frebold, Howard Tipper and George Jeletzky along with more recent material by Paul Smith and his grad students.
All this literature was very helpful in understanding not only the fossil localities but also the complex geology of the region. I also paid a couple of visits to Dr. Howard Tipper of the Geological Survey of Canada. Dr. Tipper was very supportive and helpful in providing valuable information regarding the fossil sites. He also shared with me his extensive knowledge of Jurassic palaeontology.
Armed all this information, I met up with Heidi Henderson, then Chair of the Vancouver Paleontological Society, to plan the expedition. We needed to figure out how to access this rugged and remote locality. The fossil beds are 16 kilometres from the nearest logging road and about 7500 feet above sea level.
The Tyaughton area was first mapped by C.E. Cairnes (1943) and followed by Howard Tipper (1961-1964). Cairnes mentioned briefly about the fossils beds from the area. This triggered several decades of fossil collecting by the GSC. During the 1960s and 1970s, important fossil collections were made by Frebold, Tipper, Jeletzky, and Tozer. UBC students Jennifer O’Brien and later Teri Sigmund published undergraduate honours thesis on the Jurassic Last Creek formation. During this first 2001 trip, Louise Longridge began her study of the Hettangian sections in Castle Pass. Now a PhD, she has published extensively on the fauna.
The collections made at Last Creek and at Castle Pass helped Frebold establish the Canadensis zone, the first ammonite Jurassic zone established in North America. Frebold thought he had found the earliest Hettangian (Earliest Jurassic unit) based on what he considered to be the occurrence of Psiloceras ex aff. P. planorbis. He then went on to make broad correlations with northwestern European ammonite zones. But more recent studies of the Canadensis Zone have likely indicated that the Canadensis Zone actually spans the Hettangian - Sinemurian boundary.
Part of the problem is due to the existence of endemic ammonites. Thus, many Lower Jurassic ammonite faunas in western North America cannot be correlated with well known European faunas, although the latest work by Tipper and Smith on Schlotheimid ammonites have allowed better correlation with faunas of northwest Europe. Frebold’s Psiloceras later turned out to be a new genus — Badouxia, which is now an important Index Fossil in the Canadensis zone, More recent work by David Taylor and Jean Guex in Nevada has improved correlation of the Canadensis zone across western of North America.
Most of us left Vancouver on Friday morning and reached the small town of Gold Bridge in the late afternoon / early evening. Members from the VanPs included Perry Poon, Heidi Henderson, Karen Lund, Ken Naumann, Hilmar Krocke, Cory Brimblecombe, Tonya Khan, Patricia Coutts, Leo Eutsler, Rene Savenye, Oliver Matters, Louise Longridge and myself. We were joined by Vancouver Palaeontological Society (VIPS) members, Dan Bowen, Jean Sibbald, and Betty Franklin.
Most of us checked in the Gold Bridge Motel and had dinner with everyone in the town’s only restaurant. Back at the motel, I briefed everyone of the local geology. The next morning we all met up at the local hotel for breakfast before leaving Gold Bridge for the helicopter site. We passed Carpenter Lake as Perry attempted valiantly to capture a decent photo out of my moving car. Then we turned off onto a logging road passing the Tyax lodge on our way to the Helicopter site.
After many kilometres, just along a clearing of the logging road was the pickup point. It started to rain as we got our gear ready and waited for the Helicopter to arrive. Within minutes of landing, the pilot introduced himself and gave us a crash course on helicopter safety. Soon we off like birds in the sky eagerly anticipating our destination.
What really caught my attention was the bluff just south of Castle Pass. Here lies the overturned section where the Triassic Tyaughton formation lies over the younger Last Creek formation. It perfectly matched the picture of the same section shown on page 46, Vol. 20 No.3 of the 1991 Geos, I had seen as a child.
Within an hour of picking up and dropping all 16 of us, we began to set up camp in clear view of Castle Pass. By 3:00 pm we were all making our way albeit awkwardly, along the sloped terrain towards our destination. When we arrived at the base of the pass, the group split up and we began exploring the south side of the pass. It didn’t take long before we found some fossils. Climbing up into the pass, Hilmar found a fairly complete large ammonite Coroniceras sp.
Exploring on the south side of the pass, Ken Nauman found the first Badouxia canadensis, indicating the presence of the Canadensis zone. The specimens were found along an immense scree slope on the south side of the pass. Ken, Perry Poon and I then made our way towards the contact between the Tyaughton and Last Creek formations. It sure was nice to sit along with the contact and know that we’ve straddled two time periods.
On the saddle, near the north side of the pass, Louise and Oliver were already hard at work measuring a Hettangian section for her study. Close by Cory and Tonya were working away with much success. By the time I came over, Cory had found several nicely preserved Badouxia canadensis.
Within an hour, we found several more small ammonites along with the bivalve Weyla and a high-spired gastropod. The strongly ribbed bivalve Weyla is dated here to be Late Hettangian making it the oldest known occurrence of the genus. Below the saddle we were collecting on, Dan Bowen, Sue, and Jean Sibbald were picking up ‘loose’ Badouxia that had weathered out of the hillside. Caught in the excitement, we all seemed to have forgotten about the time. Dan and I were the last two off the site as we made it back to camp in near darkness!
Excited from the first day’s finds, the group left camp first thing in the morning. About halfway to Castle Pass, I found a concretion containing small ammonite in a large outcrop of Upper Jurassic – Lower Cretaceous Relay Mountain Group shale. Dan, Perry and I combed the small exposure for concretion and to our delight found seven more ammonites. The ammonites seem to belong to the same species, as they were all involute and discoidal in shape. They reminded me of ‘little’ Placenticeras-like ammonites. We also found many well-preserved Buchia (bivalves) and Heidi found an unusual lobster claw.
By the time we found our way up onto the saddle of Castle Pass, Betty and Jean were busy collecting along the scree slope below us. They called Dan to come to check ‘something’ out. Dan soon called me down to look at what Betty had found. She had discovered a rare ammonite, Angulaticeras marmoreum and almost perfect Metophioceras rursicostatum. We cleared the loose rock and dug further into the pit to find one ammonite after another! Many ammonites were in a fragile matrix that had made collecting impossible. Digging deeper into more solid bedrock proved to the best method for extracting well-preserved fossils. News quickly got around as Hilmar, Cory, Renee, Patricia and Ken joined us. Dan worked hard to pull out a solid slab packed with about 20 ammonites, mostly Badouxia canadensis. He also managed to find a large half of Metophioceras rursicostaum, which we put aside. Hilmar then pulled out large complete ammonite that was partially encased in a soft matrix.
Ken Naumann showed me what looked to be the first of several unusually shaped nautiloids that we would later discover. I wasn’t doing too badly myself, collecting several quality ammonites including a slab containing two Badouxia alongside an extremely large Belemnite. What was amazing was the abundance and diversity of well-preserved fossils concentrated within the underlying bedrock. We found many types of bivalves, which have not been described in any great detail.
Finally, the setting sun signalled to us that we better start heading back to camp. We began trimming our finds to manageable sizes only to find out that the soft sandstones were so nice to work with that we could ‘field prep’ most of the ammonites. This was not something I would recommend doing at most other fossil sites! As for the large Metophioceras fragment, Dan Bowen would later re-discover the matching piece. After some chisel work, he had a near-complete 10-inch ammonite.
Most of us would spend the next day spread out participating in different activities in and around Castle Pass. Leo hiked up Cardtable Mountain, Jean, Betty and Heidi were exploring the scree slopes and dried up creek beds just southeast of the pass, and the rest of the crew continued to work at the quarry with considerable success. Louise and Oliver had finished measuring their section and we now working hard in collecting specimens for her study. Perry and I decided to take explore the Northwest side of Castle Pass. Armed with Geological sketch map, we made our way onto more exposures of the Late Jurassic-Early Cretaceous Relay Mountain group.
We found many belemnite fragments and Buchia sp. confirming in my mind that age of the outcrops. I was trying to locate a small limestone lens within the Last Creek formation, which has yielded numerous Lower Sinemurian ammonites. I saw the specimens at the GSC and was hoping to find the outcrop despite reading that it had been cleaned out. After a couple of hours of searching, Perry and I did find a limestone outcrop with traces of shelly material.
Unfortunately, there were no traces of the ammonites. It was getting late in the afternoon and we started to make our way back to the saddle. Suddenly, we heard a bear banger go off in the near distance.
Several hundred feet below us, in the valley, were a sow and two cubs. They were too far away to put us in any real danger but we still noticed Oliver ran down to warn us of the nearby Grizzlies.
At several hundred meters from the top of the saddle, I stopped to take a rest when I noticed several ammonites sticking out of a poorly exposed outcrop. Some last-minute digging proved to reveal more specimens of Badouxia canadensis. I excitedly packed the specimens up as I planned to return the very next day.
Perry Poon and I were the last ones back at camp. We were tired and I was starting to get very cold. Dan volunteered to warm up my food on his stove while I warmed up in the tent. Ken was also outside having a conversation with Dan. Suddenly, Dan yelled out “bear! bear!.”
We all thought it was a joke, but quickly realized that the same sow and cubs we saw in the pass, were about 50 feet away from our camp! Everyone sprung into action as we faced the bears as a large mass making loud noises and armed with bear spray. This tactic seemed to work as the cubs took off with their mother in pursuit. Oliver let off another bear banger that scared the bears further into the nearby valley. Everyone breathed a sigh of relief before chatting about the bear incident.
On day four the wind had died down, and we woke up to the warmest morning of our trip. On the previous day, Dan, Jean, Betty, Heidi and Karen had made several impressive discoveries around the gullies below the saddle. Heidi had found several species of ammonites, some that I had never seen before. A few large specimens belonged to the genus Coroniceras indicating the presence of the Lower Sinemurian Coroniceras Zone. Most of the ammonites were found in sandy siltstone, full of carbonaceous debris.
Several specimens indicated a complete size of nearly a foot in diameter and bigger! Cory, Renee and I searched for but could not locate the actual outcrop where these ammonites had eroded from. It appears that such large blocks of fossiliferous rock were rapidly transported during thawing of snow during the spring. Karen also found some wonderfully preserved corals and a gastropod from the Triassic Tyaughton formation. These fossils probably eroded from the Massive Limestone member and years of water, snow and rain naturally etched the delicate structures from the hard limestone.
After the close encounter with the grizzlies, we all decided that it would be best to leave together as a big group. This turned out to be a smart choice as we soon spotted the sow and two cubs in fairly close proximity. The sow was searching for a quick meal and found it in a nearby marmot hole. After a half hour’s worth of digging, she reached into the hole and pulled out the marmot. One of her cubs quickly seized the marmot from the surprised sow and took off down the valley. The sow and another cub soon gave chase. We continued to wait until the coast was clear as we made our way towards the marmot hole. There we all took time to marvel at how so much earth could be moved in such a short time.
It was close to eleven when we got up to the saddle. I managed to locate the previous days' ammonite site and we began to dig. It didn’t take long to find several quality specimens of Badouxia. The rock was quite a bit harder than at our first quarry. It also contained numerous calcite intrusions that often cut into the fossil itself. Cory and a few others dug about a hundred feet above me and found many nice ammonites as well.
By five o’clock everyone was pretty “fossiled” out despite the fact that we were still finding so much material. Dan and I saw what looked to be a complete Metophioceras partially exposed in the bedrock. But we all had to leave as a group due to the grizzlies. I took one good look around trying to capture the incredible beauty that surrounded me before heading down the saddle and onto the trail towards camp. As the sun began to set, we were joined by a couple of backpackers from Williams Lake who were glad to see us. They had also encountered the same bears a few days ago. After dinner, we shared our knowledge with our ‘guests’ before going to bed.
The next morning, we all woke up to extremely warm weather and numerous horseflies. Luckily, they weren’t in a biting mood. Rather annoyingly they chose to land and sit on our hats and heads. Louise, Oliver and Perry headed up to Castle Pass to do more last-minute measuring of her sections. A few others made their way to the Relay Mountain group site. The rest of us stayed in camp and had a great show and tell session. I was amazed to see that we had amassed such a fantastic fossil collection. Just about everyone went home with some beautiful specimens. I tried my best to document these fossils and am planning to keep an online photo archive of our finds in the near future.
Looking back, I found it amazing that we mostly collected fossils from the Relay Mountain group, Lower Canadensis Zone and Coroniceras beds. Yet, we have barely explored the area for fossils in the Tyaughton formation (Cassianella beds and Upper Green Clastics Member), Pre-Canadensis beds and Upper Canadensis zone. Thus, as the helicopter came and picked us up, I kept thinking about when we would return. There is still so much to explore. By the mid-afternoon, we were all back in our cars and on our way back home. The VIPS people raced off to catch the ferry while the rest of us tiredly drove back to Vancouver.
I would like to thank Dr. Howard Tipper for sharing with me his knowledge regarding the geology, palaeontology and geography of the area. For without his help, I probably would be writing this article today. We lost "Tip" in 2005. His legacy lives on in the work that we do. I would also like to thank Heidi Henderson for taking interest in organizing this VanPS expedition. Finally special thanks for everyone who came on this expedition and contributed in their own ways to a memorable experience.