With the cold weather and the short days, it’s safe to say that most people are missing summer. For our palaeontologists though, the winter months are an important part of the research process. In summer, they go out in the field to dig up new specimens. Winter is the time for analyzing what they’ve collected, writing it up, and perhaps even publishing a paper on a new discovery. We’ve asked our palaeontologists how they spent last summer and, in this two part series, they summarize the work they accomplished.
David Eberth, Research Scientist, Sedimentary Geology and Palaeoecology
During the 2016 field season, I was able to make exciting new adjustments to the geologic time scale for Alberta. For the past 31 years, I have been involved in assessing the ages of bentonites that are associated with Alberta’s dinosaurs. Bentonites are ancient volcanic ash and glass deposits that have been geologically altered by burial pressure and temperature after they were exploded from volcanoes. Given the mineral crystals they contain formed at the time of eruption and deposition, the tiny amounts of radioactive isotopes they contain can be analyzed to assess the age of sediments and fossils they were deposited with.
Hunting for bentonites takes patience and requires lots of digging and hauling. A sample that looks good at the surface may turn out to be a bust once I dig more deeply into the rock. In the field, I examine samples with a hand lens, but samples must also be examined in much greater detail in the laboratory using a microscope. As it takes lots of effort to get to a location, I often collect a potential sample in bulk before returning to the lab. A bulk sample usually means six large zip-lock bags of rock that weigh about as much as two bowling balls.
Over the years there have been incredible advances in the science of radioisotopic dating. When I started out studying the ages of bentonites in the late 1980s, I was limited to using potassium-argon, and argon40/argon39 dating, which provided accuracy at the level of plus-or-minus 1 million years. Such results allowed me to compare the approximate ages of dinosaur occurrences from different places around the world, but prevented me from making detailed comparisons. More recently I have turned to a revolutionary new technique called uranium lead chemical abrasion thermal induction mass spectrometry (U-Pb CA-TIMS dating, for short). This technique uses zircon crystals that occur in the bentonites and provides very high resolution ages for Alberta’s dinosaurs — plus-or-minus 30,000 years. For dinosaurs that are about 70 million years old, such accuracy and resolution is phenomenal. Today’s results are more than 20 times more accurate and precise than when I began studying bentonites in the 1980s. Calibrating the age of Alberta’s dinosaurs with such high precision has had profound scientific significance on our research at the Royal Tyrrell Museum of Palaeontology; we can assess patterns of dinosaur evolution, migration, and response to changes in climate and sea-level around the world. With so much new technology available, it’s an exciting time to be studying dinosaurs!
Prior to this summer, my work with CA-TIMS has focused on recalibrating the ages of the rocks and fossils at Dinosaur Provincial Park. Today we know that the dinosaurs at the Park range in age from 76.69 million years to 74.26 million years. This past summer, I spent many hours hunting for datable bentonites in the Horseshoe Canyon Formation in the Drumheller area. Six bentonites were ultimately targeted and will be dated this year.
Dennis Braman, Research Scientist, Palynology
While not much field work happened this summer, the main focus was trying to unravel the biostratigraphy of the vertebrate localities along the Oldman River. Biostratigraphy is the use of fossils to date rock formations – if you know approximately when a plant or animal lived from other sites, you know approximately the age of any rock that contains them. I collected samples from a tributary of the Oldman River near Callum Creek with poor results, a section along the Crowsnest River that indicated the Willow Creek Formation is younger than that exposed along the Oldman River, and a section north of Pierce, Alberta, again to try to work out the biostratigraphy as it relates to the section along the Oldman River west of the Porcupine Hills. I have also been doing in-house work trying to determine the ages of a number of other vertebrate localities with the samples provided by other researchers.
Don Brinkman, Head of Preservation and Research, and James Gardener, Curator of Palaeoherpetology
Vertebrate microfossil localities are accumulations of smaller-sized (about 5 cm and less) fossilized bones, teeth, scales, and other hard body parts from vertebrates (animals with backbones). These fossil localities typically occur in fine-grained sedimentary rocks that were deposited in ancient rivers and ponds and on adjacent, low lying areas such as floodplains. The preserved fossils generally represent a mixture of aquatic, semi-aquatic, and terrestrial animals that lived within a localized area and during a restricted interval of time (tens to hundreds of years). Although the fossils themselves are small, animals of different body sizes are routinely represented. For example, tiny jaws and vertebrae from small animals, such as frogs and minnow-sized fish, may be preserved along with thumb-sized teeth and toe bones from large dinosaurs.
Fossils from vertebrate microfossil localities are important for providing information about the different kinds of animals represented at the localities and insights into ancient ecosystems. In fact, much of what we know about smaller- and medium-sized animals (less than 75 kilograms) during the last 15 million years of the Late Cretaceous in Alberta is founded on fossils from vertebrate microfossil localities.
The Royal Tyrrell Museum of Palaeontology has long been interested in locating, collecting, and studying vertebrate microfossil localities (for further details on that and other research programs at the Museum, see the 2015 paper entitled “Introduction to the Special Issue commemorating the 30th anniversary of the Royal Tyrrell Museum of Palaeontology, with a summary of the Museum’s early history and its research contributions,” available for free download). A region of particular focus for the Museum has been the richly fossiliferous Dinosaur Provincial Park in southern Alberta. There, several dozens of vertebrate microfossil localities have been identified through an 85 metre sequence of rocks that spans about two million years of time during the latter part of the Late Cretaceous.
During the 2016 field season, Drs. Don Brinkman and Jim Gardner re-located and photo documented 20 vertebrate microfossil localities in Dinosaur Provincial Park. This survey was a first step in preparing to re-sample and study selected vertebrate microfossil localities of interest to their respective research agendas.
At the end of the 2016 field season, Museum staff sampled the new eggshell locality. This locality is interesting because it preserves abundant and well-preserved bones of teleost fish and amphibians, groups of particular interest to Brinkman and Gardner, respectively. It also was the first vertebrate microfossil locality that Brinkman found when he began his work in 1985. Nearly 600 kilograms of fossiliferous matrix were collected from the new eggshell locality and transported to the Royal Tyrrell Museum of Palaeontology. Over the winter, the matrix will be washed through fine screens to recover the fossils. We look forward to seeing what treasures might be revealed.
Join us for part two of this series, where we share what our mammologist and dinosaur palaeontologists were up to last summer!