Class Notes (836,391)
Canada (509,766)
EESA06H3 (564)
Nick Eyles (496)
Lecture 6

Lecture 6

5 Pages
Unlock Document

Environmental Science
Nick Eyles

EESA06 Lecture 6 Page 1 EESA06 Lecture 6 Fossils - Step 1: The earliest Bacteria: 3.8 Ga(?) - Step 2: The Cambrian Explosion: 542 Ma (multicellular animals with shells, backbones etc) - Step 3: Diversification During the Paleozoic: c.400-250 Ma - Step 4: Role of Meteorites - Nova DVD: Becoming Human Evolution of Earth: - Hadean Period – “hell on earth” - Rocks was molten, no water no atmosphere - Diversification – heavier elements sank to the middle - Magnetic field – to hold on to the gases – which build up atmosphere + oceans How are fossils formed? - Shells buried and preserved unaltered (<100 million years) - Mineralization - Cavities are filled with silica, calcium carbonate, iron (ex: tree stumps) - Most fossils are found in sedimentary rock o Exception: Pompeii people covered by pyroclastic flow and fossilized in ash Per-mineralization - Die in or near water - Soft parts consumed by bacteria - Sedimentation (fine grained =more detail, chemical makeup of rock = color) - More sediments pile on = pressure – rock - Mineral rich water = changes to the shell - Uplift – by continental crusts coming together (plate tectonics) - Erosion – wear away rocks Ammolite – an organic gemstone Ammonite fossils – iridescent aragonite with trace elements (Fe, Mn, Al, Ba) Trace Fossils - Preserved tracks, trails, burrows (protection/food), borings - Ichnology – study of trace fossils - Bioturbation – process of disturbing sediment Fossils as clues to ancient environments - Palaeocology – study of ancient organisms and their environments o (St.Cuthbert rings, Sea Lily - Crinoide) o Clues from: fossil types, assemblages (group of fossils tend to be found together), fossil morphology, trace fossils Fossils and stratigraphy - How do we use fossils in stratigraphy? o to establish relative age of rock units, correlate units - What information do we need to do this? o Relative age of rock units o Fossil species present in each unit EESA06 Lecture 6 Page 2 o Geologic range - Establish time of first and last appearance of each species William Smith – Principal of Faunal Succession – fossils appear in layers What kinds of Fossils are most useful for stratigraphic work? - Index Fossils (ex: Ammonites) - Are Short-lived and widespread - Assemblages (groups) of species Trilobite Growth - Trilobites molted regularly – shed skin - Thus very abundant in the fossil record The evolution of Life on Earth… - Intense bombardment from 4.5 to 4 Ga prevented life becoming established - No magnetic field to prevent oceans and atmosphere being stripped off the planet’s surface by the solar wind? Sir James Dawson – was wrong. - Thought to be the oldest fossil Eozoon Canadense (1868) – ‘the dawn of animal of Canada’ now recognized as mineral not organic – dubiofossil Step 1: The Earliest bacteria 3.3 Ga (?) - Prokaryotes – some are photosynthetic (called cyanobacteria: blue/green algae) o Microscopic, single-celled, lacking a nucleus - The earliest prokaryotes (the Archaea) lives around superheated waters near submarine volcanic vents (hyperthermophilic) o Simple bag-like cells o Only life forms between 3.8 and about 2 Ga Where on Earth did early life forms flourish? - Probably in oceans – salts, solvents, mixing of elements to create organic compounds EESA06 Lecture 6 Page 3 - Life forms may have first developed at hydrothermal vents (mid-ocean ridges) At Modern Hydrothermal vents (called smokers) on mid-ocean ridges: - Microbes – hydrothermophiles - Live at temps > 100C - No light - Energy from chemosynthesis – ex: sulfur Gunflint Formation (in Ontario) – prokaryotes - 1.9 billion – once thought to be the world’s oldest fossils Oldest Cyanobacteria are thought to be 3.5 billion years old from the Apex Chert in Western Australia - They may be dubio-fossils… entirely of mineral origin, not organic Stromatolites (Gk for ‘stoney carpet’) - most common Proterozoic fossils made up of colonies of prokaryotic bacteria trapping fine sediment on sticky bacterial mats - Modern relatives still survive in hyper-saline lagoons in western Australia The “Rusting” of the Earth c. 2.8 Ga - Hydrothermal Delivery of Dissolved
More Less

Related notes for EESA06H3

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.