Common Fieldstone Fossils of Saskatchewan
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Common Fieldstone Fossils Of Saskatchewan By: Frank H. McDougall 3rd Edition 2019 Crinoid stem in Ordovician limestone FOREWARD The following guide was originally developed by the author in order to compliment the Saskatchewan Archaeology Societies (SAS) summer archaeological caravan tours that began in 2012 and visited many local Saskatchewan museums. The author has drawn on an extensive career in mining exploration and palaeontology as well as experience with local provincial museum collections in preparing this guide. This document is designed to aid in the identification of the more common fossil specimens found in fieldstones in Saskatchewan. It is not meant to be an exhaustive resource that will allow the user to identify all specimens. Common Fieldstone Fossils Of Saskatchewan, 3rd Edition i TABLE OF CONTENTS FOREWARD ....................................................................................................................... i TABLE OF CONTENTS.................................................................................................... ii LIST OF FIGURES ............................................................................................................ ii 1.0. INTRODUCTION ........................................................................................................2 2.0. SOURCES OF FOSSIL MATERIAL IN SASKATCHEWAN ...................................2 3.0. COMMON FIELDSTONE FOSSILS FOUND IN SASKATCHEWAN ....................3 3.1. Fossils Found in Limestone Rocks ..........................................................................3 3.1.1. Receptaculites ....................................................................................................5 3.1.2. Nautiloids...........................................................................................................6 3.1.3. Crinoids..............................................................................................................8 3.1.4. Gastropods .........................................................................................................9 3.1.5. Brachiopods .....................................................................................................10 3.1.6: Rugose Corals..................................................................................................12 3.2. Fossils Found in Mudstone Rocks .........................................................................14 3.2.1. Baculites (Cretaceous Nautiloids)....................................................................14 3.2.2. Ammonites.......................................................................................................16 3.2.3. Pelecypods .......................................................................................................18 3.3. Other Common Fossils ..........................................................................................18 3.3.1. Fossil or “Petrified” wood ...............................................................................19 3.3.2. Mammoth teeth ................................................................................................20 4.0. PSEUDOFOSSILS .....................................................................................................22 4.1. Concretions ............................................................................................................22 4.2. Rocks with Differential Weathering ......................................................................23 4.3. Other Rocks That Form Pseudofossils...................................................................24 5.0. ADDITIONAL REFERENCES ................................................................................26 6.0. OTHER PUBLICATIONS BY THE AUTHOR ........................................................26 7.0. ABOUT THE AUTHOR ............................................................................................27 FIGURES Figure 1: The Young Erratic................................................................................................2 Figure 2: Distribution of bedrock deposits in Saskatchewan ..............................................4 Figure 3: Example of Ordovician age Tyndall stone limestone with fossils .......................5 Figure 4: Complete specimen of Ordovician age Receptaculites ........................................6 Figure 5: Shell of modern chambered nautilus....................................................................7 Figure 6: Example of Nautiloid shell from Ordovician age limestone................................8 Figure 7: Crinoid fossils and drawing of complete specimen..............................................9 Common Fieldstone Fossils Of Saskatchewan, 3rd Edition ii Figure 8: Ordovician gastropods and section through modern gastropod .........................10 Figure 9: Determining the difference between pelecypod and brachiopods......................11 Figure 10: Examples of Ordovician brachiopods ..............................................................12 Figure 11: Examples of rugose corals................................................................................13 Figure 12: Section through Ordovician rugose coral.........................................................13 Figure 13: Two examples of baculite shells from the Late Cretaceous of Saskatchewan.14 Figure 14: Broken section of baculite showing internal structure .....................................15 Figure 15: Fragment of baculite shell showing pattern of internal cell walls....................15 Figure 16: Diagram showing anatomy of ammonite shell and animal ..............................16 Figure 17: Example of large ammonite showing features of the shell ..............................17 Figure 18: Two examples of pelecypod shells from the Late Cretaceous .........................18 Figure 19: Example of fossilized wood showing preserved growth rings.........................19 Figure 20: Example of fossilized wood showing primary features ...................................20 Figure 21: Example of mammoth molar tooth from Saskatchewan ..................................21 Figure 22: Concretion that creates pseudofossil that looks like a claw .............................22 Figure 23: Basaltic bedrock with granitic intrusive...........................................................23 Figure 24: Differentially weathered rocks that resemble man made artifacts ...................24 Figure 25: Example of sheared Precambrian rock that looks like a fossil log...................25 Common Fieldstone Fossils Of Saskatchewan, 3rd Edition iii 1.0 INTRODUCTION Most of the specimens of fossils found in Saskatchewan fieldstones are sourced from the province itself with a few exotic ones that have been brought in from outside by people who have travelled abroad. This guide is aimed at the ones that have been found within the province itself. Many of the provincially sourced specimens are quite common and examples of them are found in most museum collections. This guide will talk first about the sources of the material and then will give specific information on the most common fossil specimens found. 2.0. SOURCES OF FOSSIL MATERIAL IN SASKATCHEWAN Although some localities of bedrock occur in the southern half of Saskatchewan especially in the southwest and along the US border most of the rock and fossil specimens found in this area come from what are commonly referred to as "fieldstones". These are the rocks that we often see laying out in pastures and farm fields throughout the province. They vary in size from a few centimetres up to some that are many meters in diameter and weigh hundreds of tonnes (Figure 1). Many of these fieldstones can contain fossils. Figure 1: The Young Erratic, one of the largest fieldstones in southern Saskatchewan. It is composed of fossiliferous limestone and weighs roughly 700 tons. Photo credit: Belinda Riehl- Fitzsimmons. Common Fieldstone Fossils Of Saskatchewan, 3rd Edition 2 These fieldstones are more correctly known as Glacial Erratics. Glacial Erratics are pieces of bedrock that have been picked up by the glaciers during the ice age (Pleistocene) and transported to new locations were they were dropped in deposits up to 400 metres thick. In this way fieldstones with bedrock sources as far away as the east side of Hudson Bay have been deposited over virtually the entire province. Naturally the moving ice does not discriminate as to which type of bedrock it picks up. Therefore fieldstones found in any given area are often composed of a wide variety of rock types that can represent all of the bedrock that the ice travelled over from the time of its formation to the time that it melted. The northern half of Saskatchewan is mainly underlain by bedrock of Precambrian age (Figure 2) and although glacial deposits are common here too the bedrock is much better exposed than in the south as the ice was picking up much of the till material here rather than depositing it. These ancient rocks are virtually devoid of any fossils and as a result the fieldstones in this part of the province contain fewer fossils than in the south. Some fossil bearing material has been transported into northern Saskatchewan from the Hudson Bay area that is underlain by post Precambrian rocks however and there is also potential for fossils of animals from the Pleistocene to be present in the glacial deposits. It is from this northern area of Precambrian bedrock that the fieldstones in the southern half of the province