Geology
Tyndall Stone is a distinctive mottled stone used in the construction or facing of many major buildings in Canada. The Houses of Parliament in Ottawa, the Legislative Buildings in Winnipeg (Manitoba), Regina (Saskatchewan) and the Empress Hotel in Victoria BC are prime examples. The material when fresh is a light grey with darker grey to brown mottles and it weathers over time to a pleasant creamy yellow or gold colour with rust coloured mottles. Fossils are always present in Tyndall Stone.
Tyndall Stone is quarried from Garson, Manitoba, which is located 37 km northeast of Winnipeg. The Garson deposit was opened in 1895, although the first record of construction with Tyndall Stone extends even further back to 1832, when it was used to build the fort warehouse and walls of Lower Fort Garry in Manitoba. Tyndall Stone acquired its name from Tyndall, the closest railway point to Garson.
During the late Ordovician Period, approximately 450 million years ago, southern Manitoba was a warm, shallow, inland sea just south of the equator. Many different types of animals lived in this ocean including corals, sponges, molluscs and algae. Other animals such as trilobites, and stromatoporoids are now extinct. These creatures lived on or above the soft muddy sea floor and when they died, their skeletal remains became part of the muddy layers. Other animals burrowed in the mud of the sea floor for food or protection and it is their preserved burrows that make up the beautiful mottling which gives Tyndall Stone its unique appearance.
A variety of fossil types can be found in Tyndall Stone. This earthcache will identify some of the types.
Trace Fossils: This is the name of the mottles which give the Tyndall Stone its distinctive appearance. The mottles are actually fossils. They are traces of burrows made in the original sediment by an unknown animal and the disturbed sediment within the burrows has been preferentially dolomitised at a later date making it darker and more resistant to weathering.
Tabulate and Rugose corals were ancient types not related to modern corals. They are now extinct.
Chain Coral (Catenipora) was a colonial tabulate coral. Individual corallites which form the colony grew as a vertical tube with elliptical cross-section and joined along the edges to give the appearance of a chain, hence the common name Chain Coral..
Saffordophyllum was a colonial tabulate coral in which the vertical tubes of the corallites are polygonal in cross-section and joined on all sides to give the appearance of a honeycomb, hence the common name Honeycomb Coral.
Calapoecia was a colonial tabulate coral in which the vertical tubes of the corallites are separated from each other by a calcareous mesh.
Grewingkia was a solitary rugose coral. Individuals were separate and grew in the shape of a slightly curved cone rather like a cow's horn, hence the common name Horn Coral. In cross-section the fossil shows a circular to elliptical shape with septa radiating from the centre. In vertical section it shows an elongated curved triangular shape with septa running along its length.
Stromatoporoid - were colonial animals in which the very small individuals formed layers as the colony grew. They are now extinct.
Receptaculitids were animals with a similar life style to modern sponges. They are now extinct. Fisherites was a large form which grew in the shape of a hollow irregular sphere, the walls of which were double and made up of small hexagonal plates and rods. In some sections the arrangement of the plates resembles a sunflower blossom hence the common, but erroneous name, Sunflower Coral.
Gastropods: These include your typical snails, as well as other forms such as slugs. Fossils of both tall spiral shells and more broadly rounded ones may be found in Tyndall Stone. Examples include the Hormotoma and Maclurites
Cephalopods: These are relatives of today’s octopods, squids, and the “living fossil” nautilus. Like the existing nautilus they have a shell composed of a series of separate chambers. The shell may be curved (like the nautilus) or straight, but straight ones are much more commonly seen in Tyndall Stone.
Logging Requirements
- Go to each of the reference points and identify which fossil or fossils you find at that location. Send me your answers in an email. (Note: You may find two of the photos at the same location).Answers must be sent before logging a find on this earthcache.
- Find the Cephalopod fossil in photo # 9 at the coordinates given on the north wall. Send me the length and width of this fossil.
- (Optional task) Photos are appreciated so if you like take a photo of yourself or your GPS in front of one of the fossils you find. Note: Most of the fossils can be found on the wall between knee height and head height. The fossil from photo 3 can be found above 12 feet up the wall and is large and distinctive.
Due to signal bounce, I have included an aerial view of the Library with the 6 locations marked out in order to make it easier to find the locations.
Photo #1
Photo #2
Photo #3
Photo #4
Photo #5
Photo #6
Photo #7
Photo #8
Photo #9
References
Manitoba’s Tyndall Stone - http://www.whaton.uwaterloo.ca/waton/s9911.html
Doug Patterson - http://dfp.mediacooks.com/fossils/page7.html
Doug Patterson - http://dfp.mediacooks.com/fossils/page4.html
Popular Science - http://www.gac.ca/PopularGeoscience/factsheets/TyndallStone_e.pdf
