LATE HETTANGIAN FOSSIL FAUNA FROM THE TASEKO LAKES: BRITISH COLUMBIA

The late Hettangian ammonite fauna from Taseko Lakes is diverse and relatively well‐preserved. Over three field seasons, thirty-five taxa from the Mineralense and Rursicostatum zones were studied and three new species discovered and named: Fergusonites hendersonae, Eolytoceras constrictum and Pseudaetomoceras victoriense. 

This material is very important as it greatly expands our understanding of the fauna and ranges of ammonites currently included in the North American regional ammonite zonation. 

I had the very great honour of having the fellow below, Fergusonites hendersonae, a new species of nektonic carnivorous ammonite, named after me by palaeontologist Louse Longridge from the University of British Columbia. 

I'd met Louise as an undergrad and was pleased as punch to hear that she would be continuing the research by Dr. Howard Tipper, the authority on this area of the Chilcotins and Haida Gwaii — which he dearly loved. 

"Tip" was a renowned Jurassic ammonite palaeontologist and an excellent regional mapper who mapped large areas of the Cordillera. He made significant contributions to Jurassic paleobiogeography and taxonomy in collaboration with Dr. Paul Smith, Head of Earth and Ocean Science at the University of British Columbia. 

Tip’s regional mapping within BC has withstood the test of time and for many areas became the regions' base maps for future studies. The scope of Tip’s understanding of Cordilleran geology and Jurassic palaeontology will likely never be matched. He passed away on April 21, 2005. His humour, knowledge and leadership will be sorely missed. 

Fergusonites hendersonae

Before he left us, he shared that knowledge with many of whom who would help to secure his legacy for future generations. We did several trips over the years up to the Taseko Lake area of the Rockies joined by many wonderful researchers from Vancouver Island Palaeontological Society and Vancouver Paleontological Society, as well as the University of British Columbia. 

Both Dan Bowen and John Fam were instrumental in planning those expeditions and each of them benefited greatly from the knowledge of Dr. Howard Tipper. 

If not for Tipper's early work in the region, our shared understanding and much of what was accomplished in his last years and after his passing would not have been possible. 

Over the course of three field seasons, we endured elevation sickness, rain, snow, grizzly bears and very chilly nights  — we were sleeping right next to a glacier at one point — but were rewarded by the enthusiastic crew, helicopter rides — which really cut down the hiking time — excellent specimens including three new species of ammonites, along with a high-spired gastropod and lobster claw that have yet to be written up. This area of the world is wonderful to hike and explore — stunningly beautiful country. We were also blessed with access as the area is closed to all fossil collecting except with a permit.

This fauna understanding helps us to understand the correlations between different areas: (1) the Mineralense and Rursicostatum zones are present in Taseko Lakes and can be readily correlated with contemporaneous strata elsewhere in North America; (2) the Mineralense and Rursicostatum zones of North America are broadly equivalent to the Canadensis Zone and probably the Arcuatum horizon of the South American succession; (3) broad correlations are possible with middle–late Hettangian and earliest Sinemurian taxa in New Zealand; (4) the Mineralense and Rursicostatum zones are broadly equivalent to the circum‐Mediterranean Marmoreum Zone; (5) the Mineralense Zone and the lower to middle portion of the Rursicostatum Zone are probably equivalent to the Complanata Subzone whereas the upper portion of the Rursicostatum Zone may equate to the Depressa Subzone of the north‐west European succession.

Taseko Lake Area, BC

The Taseko Lakes area has yielded the best preserved and most diverse collection of late Hettangian ammonites yet discovered in British Columbia (BC). Early studies of the fauna were undertaken by Frebold (1951, 1967). At that time, eastern Pacific ammonite faunas were poorly understood and species were frequently shoehorned into established north‐west European taxa. 

Since then, knowledge of eastern Pacific Hettangian ammonite faunas has improved considerably. 

Detailed systematic studies have been completed on faunas from localities in other areas of BC, Alberta, Alaska, Oregon, Nevada, Mexico and South America (e.g. Guex 1980, 1995; Imlay 1981; Hillebrandt 1981, 1988, 1990, 1994, 2000a–d; Smith and Tipper 1986; Riccardi et al. 1991; Jakobs and Pálfy 1994; Pálfy et al. 1994, 1999; Taylor 1998; Hall et al. 2000; Taylor and Guex 2002; Hall and Pitaru 2004). 

These studies have demonstrated that Early Jurassic eastern Pacific ammonites had strong Tethyan affinities as well as a high degree of endemism (Guex 1980, 1995; Taylor et al. 1984; Smith et al. 1988; Jakobs et al. 1994; Pálfy et al. 1994). Frebold’s early studies were also hampered because they were based on small collections, which limited understanding of the diversity of the fauna and variation within populations. However, recent mapping has greatly improved our understanding of the geology of Taseko Lakes (Schiarizza et al. 1997; Smith et al. 1998; Umhoefer and Tipper 1998) and encouraged further collecting that has dramatically increased the size of the sample.

A study of the ammonite fauna from Taseko Lakes is of interest for several reasons. The data are important for increasing the precision of the late Hettangian portion of the North American Zonation. 

Owing to the principally Tethyan or endemic nature of Early Jurassic ammonites in the eastern Pacific, a separate zonation for the Hettangian and Sinemurian of the Western Cordillera of North America has been established by Taylor et al. (2001). Except for information available from the early studies by Frebold (1951, 1967), the only Taseko Lakes taxa included in the North American Zonation of Taylor et al. (2001) were species of Angulaticeras studied by Smith and Tipper (2000). 

Since then, Longridge et al. (2006) made significant changes to the zonation of the late Hettangian and early Sinemurian based on a detailed study of the Badouxia fauna from Taseko Lakes (Text‐fig. 2). An additional taxonomic study was recently completed on the late Hettangian ammonite Sunrisites (Longridge et al. 2008) and this information has not yet been included within the zonation. 

Hettangian Zonation

The systematics of the remaining ammonite fauna from Taseko Lakes are presented here. A comprehensive study of this material is important because the exceptional quality and diversity of the fauna provide important data for updating the North American Zonation, making it more comprehensive and more widely applicable, especially in Canada.

The Taseko Lakes fauna can improve Hettangian correlations within North America as well as between North America and the rest of the world. 

North‐west European ammonite successions (e.g. Dean et al. 1961; Mouterde and Corna 1997; Page 2003) are considered the primary standard for Early Jurassic biochronology (Callomon 1984). 

In north‐west Europe, the turnover from schlotheimiid dominated faunas in the late Hettangian to arietitid dominated faunas in the early Sinemurian was sharp (e.g. Dean et al. 1961; Bloos 1994; Bloos and Page 2002). In other areas, by contrast, these faunas were not so mutually exclusive and the transition was much more gradual. 

This makes correlations between north‐west Europe and other areas difficult (e.g. Bloos 1994; Bloos and Page 2000, 2002). Correlations are further impeded by endemism and provincialism. 

The Taseko Lakes fauna addresses these problems because it contains many taxa that are common throughout the eastern Pacific as well as several cosmopolitan taxa that make intercontinental correlation possible. Correlation between North America and other areas is of particular significance in that the interbedded volcanic and fossiliferous marine rocks in North America permit the calibration of geochronological and biochronological time scales (Pálfy et al. 1999, 2000). 

This correlation between the late Hettangian fauna in the Taseko Lakes area and contemporaneous faunas in other areas of North America, South America, New Zealand, western and eastern Tethys, and north‐west Europe is of particular interest to me — especially the correlation of the faunal sequences of Nevada, USA. 

Reference: PaleoDB 157367 M. Clapham GSC C-208992, Section A 09, Castle Pass Angulata - Jurassic 1 - Canada, Longridge et al. (2008)

L. M. Longridge, P. L. Smith, and H. W. Tipper. 2008. Late Hettangian (Early Jurassic) ammonites from Taseko Lakes, British Columbia, Canada. Palaeontology 51:367-404

PaleoDB taxon number: 297415; Cephalopoda - Ammonoidea - Juraphyllitidae; Fergusonites hendersonae Longridge et al. 2008 (ammonite); Average measurements (in mm): shell width 9.88, shell diameter 28.2; Age range: 201.6 to 196.5 Ma. Locality info: British Columbia, Canada (51.1° N, 123.0° W: paleo coordinates 22.1° N, 66.1° W)

Photo One: Hettangian Ammonites and Gastropods, Taseko Lakes. Photo Two: Fergusonites hendersonae, a Late Hettangian (Early Jurassic) ammonite from the Taseko Lakes area of British Columbia, Canadian Rockies, named by Dr. Louise Longridge after Heidi Henderson, Chair, Vancouver Paleontological Society who collected and subsequently donated many Hettangian specimens from Taseko Lakes to the GSC collections. Holotype. GSC 127423 from the Rursicostatum Zone, Castle Pass section A, level 06, Taseko Lakes.

Map: Localities of sections and isolated outcrops bearing late Hettangian ammonites in the Taseko Lakes map area. Figure Two: Zonation for the Hettangian showing correlation of North American zones with South America, north‐west Europe, western Tethys (circum‐Mediterranean), eastern Tethys and New Zealand. Only approximate correlations are implied. 

HISTORICAL FOLIAGE & THE FOSSIL RECORD

The colder seasons of autumn and winter are a wonderful time to explore Vancouver. The riot of yellow, orange and green from the cities autumn palette slowly fades to deep gold and soft browns. 

Fallen debris you crunch through send up wafts of earthy smells that whisper of decomposition, the journey from leaf to soil.

It is a wonderful time to be out and about. I do love the mountain trails but must confess to loving our cultivated gardens for their colour and variety. 

We have some lovely native plants and trees and more than a few exotics at Vancouver's arboreal trifecta — Van Dusen, Queen E Park and UBC Botanical Gardens. One of those exotics, at least exotic to me, is the lovely conifer you see here is Metasequoia glyptostroboides — the dawn redwood. 

Of this long lineage, this is the sole surviving species in the genus Metasequoia and one of three species of conifers known as redwoods. Metasequoia are the smaller cousins of the mighty Giant Sequoia, the most massive trees on Earth. 

As a group, the redwoods are impressive trees and very long-lived. The President, an ancient Giant Sequoia, Sequoiadendron giganteum, and granddaddy to them all has lived for more than 3,200 years. While this tree is named The President, a worthy name, it doesn't really cover the magnitude of this giant by half.   

This tree was a wee seedling making its way in the soils of the Sierra Nevada mountains of California before we invented writing. It had reached full height before any of the Seven Wonders of the Ancient World, those remarkable constructions of classical antiquity, were even an inkling of our budding human achievements. And it has outlasted them all save the Great Pyramid of Giza, the oldest and last of those seven still standing, though the tree has faired better. Giza still stands but the majority of the limestone façade is long gone.

Aside from their good looks (which can really only get you so far), they are resistant to fire and insects through a combined effort of bark over a foot thick, a high tannin content and minimal resin, a genius of evolutionary design. 

While individual Metasequoia live a long time, as a genus they have lived far longer. 

Like Phoenix from the Ashes, the Cretaceous (K-Pg) extinction event that wiped out the dinosaurs, ammonites and more than seventy-five percent of all species on the planet was their curtain call. The void left by that devastation saw the birth of this genus — and they have not changed all that much in the 65 million years since. Modern Metasequoia glyptostroboides looks pretty much identical to their late Cretaceous brethren.

Dawn Redwood Cones with scales paired in opposite rows

They are remarkably similar to and sometimes mistaken for Sequoia at first glance but are easily distinguishable if you look at their size (an obvious visual in a mature tree) or to their needles and cones in younger specimens. 

Metasequoia has paired needles that attach opposite to each other on the compound stem. Sequoia needles are offset and attached alternately. Think of the pattern as jumping versus walking with your two feet moving forward parallel to one another. 

Metasequoia needles are paired as if you were jumping forward, one print beside the other, while Sequoia needles have the one-in-front-of-the-other pattern of walking.

The seed-bearing cones of Metasequoia have a stalk at their base and the scales are arranged in paired opposite rows which you can see quite well in the visual above. Coast redwood cone scales are arranged in a spiral and lack a stalk at their base.

Although the least tall of the redwoods, it grows to an impressive sixty meters (200 feet) in height. It is sometimes called Shui-sa, or water fir by those who live in the secluded mountainous region of China where it was rediscovered.

Fossil Metasequoia, McAbee Fossil Beds

Metasequoia fossils are known from many areas in the Northern Hemisphere and were one of my first fossil finds as a teenager. 

And folk love naming them. More than twenty fossil species have been named over time —  some even identified as the genus Sequoia in error — but for all their collective efforts to beef up this genus there are just three species: Metasequoia foxii, Metasequoia milleri, and Metasequoia occidentalis.

During the Paleocene and Eocene, extensive forests of Metasequoia thrived as far north as Strathcona Fiord on Ellesmere Island and sites on Axel Heiberg Island in Canada's far north around 80° N latitude.

We find lovely examples of Metasequoia occidentalis in the Eocene outcrops at McAbee near Cache Creek, British Columbia, Canada. I shared a photo here of one of those specimens. Once this piece dries out a bit, I will take a dental pick to it to reveal some of the teaser fossils peeking out.

The McAbee Fossil Beds are known for their incredible abundance, diversity and quality of fossils including lovely plant, insect and fish species that lived in an old lake bed setting. While the Metasequoia and other fossils found here are 52-53 million years old, the genus is much older. It is quite remarkable that both their fossil and extant lineage were discovered in just a few years of one another. 

Metasequoia was first described as a new genus from a fossil specimen found in 1939 and published by Japanese paleobotanist Shigeru Miki in 1941. Remarkably, the living version of this new genus was discovered later that same year. 

Professor Zhan Wang, an official from the Bureau of Forest Research was recovering from malaria at an old school chum's home in central China. His friend told him of a stand of trees discovered in the winter of 1941 by Chinese botanist Toh Gan (干铎). The trees were not far away from where they were staying and Gan's winter visit meant he did not collect any specimen as the trees had lost their leaves. 

The locals called the trees Shui-sa, or water fir. As trees go, they were reportedly quite impressive with some growing as much as sixty feet tall. Wang was excited by the possibility of finding a new species and asked his friend to describe the trees and their needles in detail. Emboldened by the tale, Wang set off through the remote mountains to search for his mysterious trees and found them deep in the heart of  Modaoxi (磨刀溪; now renamed Moudao (谋道), in Lichuan County, in the central China province of Hubei. He found the trees and was able to collect living specimens but initially thought they were from Glyptostrobus pensilis (水松). 

A few years later, Wang showed the trees to botanist Wan-Chun Cheng and learned that these were not the leaves of s Glyptostrobus pensilis (水松 ) but belonged to a new species. 

While the find was exciting, it was overshadowed by China's ongoing conflict with the Japanese that was continuing to escalate. With war at hand, Wang's research funding and science focus needed to be set aside for another two years as he fled the bombing of Beijing. 

When you live in a world without war on home soil it is easy to forget the realities for those who grew up in it. 

Zhan Wang and his family lived to witness the 1931 invasion of Manchuria, then the 1937 clash between Chinese and Japanese troops at the Marco Polo Bridge, just outside Beijing. 

That clash sparked an all-out war that would grow in ferocity to become World War II. 

Within a year, the Chinese military situation was dire. Most of eastern China lay in Japanese hands: Shanghai, Nanjing, Beijing, Wuhan. As the Japanese advanced, they left a devastated population in their path where atrocity after atrocity was the norm. Many outside observers assumed that China could not hold out, and the most likely scenario was a Japanese victory over China.

Yet the Chinese hung on, and after the horrors of Pearl Harbor, the war became genuinely global. The western Allies and China were now united in their war against Japan, a conflict that would finally end on September 2, 1945, after Allied naval forces blockaded Japan and subjected the island nation to intensive bombing, including the utter devastation that was the Enola Gay's atomic payload over Hiroshima. 

With World War II behind them, the Chinese researchers were able to re-focus their energies on the sciences. Sadly, Wang was not able to join them. Instead, two of his colleagues, Wan Chun Cheng and Hu Hsen Hsu, the director of Fan Memorial Institute of Biology would continue the work. Wan-Chun Cheng sent specimens to Hu Hsen Hsu and upon examination realised they were the living version of the trees Miki had published upon in 1941. 

Hu and Cheng published a paper describing a new living species of Metasequoia in May 1948 in the Bulletin of Fan Memorial Institute of Biology.

That same year, Arnold Arboretum of Harvard University sent an expedition to collect seeds and, soon after, seedling trees were distributed to various universities and arboreta worldwide. 

Today, Metasequoia grow around the globe. When I see them, I think of Wang and all he went through. He survived the conflict and went on to teach other bright, young minds about the bountiful flora in China. I think of Wan Chun Cheng collaborating with Hu Hsen Hsu in a time of war and of Hu keeping up to date on scientific research, even published works from colleagues from countries with whom his country was at war. Deep in my belly, I ache for the huge cost to science, research and all the species impacted on the planet from our human conflicts. Each year in April, I plant more Metasequoia to celebrate Earth Day and all that means for every living thing on this big blue orb.  

References: 

• https://web.stanford.edu/group/humbioresearch/cgi-bin/wordpress/?p=297
• https://humboldtredwoods.org/redwoods