EAS 209 - Lecture 32

Review of Previous Lecture: Colorado Group

• Previous lecture discussed the Colorado Group.

• Represents approximately 800 m of shale deposition.

• Deposited when the Western Interior Seaway connected:

  • Gulf of Mexico.

  • Boreal Sea.

• Nearly one kilometer of shale accumulated during this interval.

Completion of the Sloss Sequence Framework

• Course has progressed through the entire Sloss sequence framework.

• Covered geology from the Precambrian onward.

• Today's lecture focuses only on the very top of the record.

• Major Tejas deposits are largely absent in Alberta.

• Only small remnants are preserved locally.

• Focus shifts to:

  • Tertiary deposits.

  • Quaternary glaciation.

Tertiary Period:

• Tertiary period began with the demise of the non-avian dinosaurs in the Cretaceous-Tertiary extinction event (called the KT boundary).

• In terms of climate, the period was marked by widespread cooling, beginning in the Paleocene with tropical-to-moderate worldwide temperatures and ending before the first extensive glaciation at the start of the Quaternary. Although there was the Eocene Thermal Maximum (Ypression).

• Mammals replaced reptiles as the dominant vertebrates on the planet.

• Modern types of birds, reptiles, amphibians, fish, and invertebrates became numerous at the beginning of this period. Whales too!.

• Modern types families of flowering plants evolved.

• The earliest recognizable hominid relatives of humans appeared.

• Begins after the end-Cretaceous extinction.

• Cretaceous ended with:

  • Chicxulub impact event.

  • Dinosaur extinction.

  • Major ecological disruption.

• Mammals diversified afterward and became dominant.

KT Boundary

• KT boundary = Cretaceous–Tertiary boundary.

• "K" used instead of "C" because several geological periods begin with C.

• Marks:

  • End of dinosaurs.

  • Beginning of mammal-dominated ecosystems.

Tertiary Climate Evolution

• Early Tertiary climate remained relatively warm.

• Paleocene:

  • Tropical to temperate conditions.

• Eocene:

  • Experienced the Eocene Thermal Maximum.

  • One of the warmest intervals of the Cenozoic.

• Following Eocene:

  • Long-term cooling trend.

  • Development of polar ice.

  • Expansion of glaciers.

• Last ~10,000 years represent recovery from glaciation.

• Modern climate remains cooler than:

  • Cretaceous climates.

  • Early Paleogene climates.

Evidence for Ancient Warm Climates

• Fossil forests preserved:

  • Antarctica.

  • High Arctic.

• Presence of trees in these regions indicates:

  • Much warmer global temperatures.

  • Absence of permanent polar ice during those times.

Major Tertiary Epochs

• Paleocene.

• Eocene.

• Oligocene.

• Miocene.

• Pliocene.

• Pleistocene follows later in the Quaternary.

  • Important to know all of these.

Evolutionary and Tectonic Events Through the Tertiary

Paleocene

• Rodents appear.

• Early primates appear.

• Atlantic Ocean continues development.

Eocene

• Eocene Thermal Maximum occurs.

• Bats appear.

• Early whales appear.

• Early horse ancestors (Eohippus) appear.

• Europe and North America separate further.
  
  

Oligocene

• Australia separates from Antarctica.

• India collides with Asia.

• Himalayas begin forming.

• Antarctic glaciation begins.

• Dogs, cats, and pigs appear.

Miocene

• Africa moves toward Europe.

• Alps continue developing.

• Arctic ice expands.

• Horses diversify.

• Beavers appear.

• Apes diversify.

Pliocene

• Mediterranean Sea develops further.

• North and South America connect via Panama.

• Modern continental arrangement becomes established.

• Earliest humans begin appearing.

Whale Evolution

• Fossil whale skeletons discovered during sedimentological fieldwork in Africa.

• Whales are interpreted to have evolved from land-dwelling ancestors.

• Evolutionary sequence:

  • Terrestrial mammal.

  • Semi-aquatic lifestyle.

  • Fully aquatic whale.

• Represents movement from land back into the ocean.

• In the tertiary they went back into the water → whale formation.

Eocene Fossil Forests of the Arctic (Axel Heiberg)

• Located on Axel Heiberg Island.

• Dated to approximately 50 million years ago.

• Preserved tree trunks found far north of modern tree line.

• Forests existed during the Eocene Thermal Maximum.

• Demonstrates:

  • Warm Arctic climate.

  • Major climate differences from today.

• The thermal maximum occurred right at the start of the Eocene (Ypression).

Dating Limitation

• Carbon dating cannot be used on Eocene fossils.

• Fossils are too old for radiocarbon methods.

• Alternative dating techniques are required.

Tertiary Deposits in Alberta

• Deposits formed within the foreland basin.

• Basin created by loading from Rocky Mountain uplift.

• Weight of mountains depressed the crust.

• Depression filled with sediment.

Preserved Tertiary Units

Rocky Mountains/Foothills

• Porcupine Hills Formation.

• Willow Creek Formation.

Plains Region

• Paskapoo Formation.

  • Major aquifer unit.

  • Contains important groundwater reservoirs.

  • Contains coal deposits.

  • Source of significant surface coal mining.

Obed Coal Zone

• Part of the Paskapoo Formation.

• Located near Obed Mountain.

• Obed Mountain lies along Highway 16 between Edmonton and Jasper.

• Area known for coal resources.

Preservation of Tertiary Deposits

• Much of Alberta's Tertiary record was removed by glacial erosion.

• Best-preserved sections occur in elevated regions:

  • Cypress Hills.

  • Swan Hills.

  • Caribou Mountains.

  • Birch Mountains.

• These areas preserve more complete successions than lower regions.

• Everything else has been eroded by glaciers.

• Tertiary Alberta: this part of the succession is a thin to thick veneer of continental, largely alluvial plain sediments; much is stripped by erosion… 10 isolated plateaus.

  • Examples include Swan Hills and Cyprus Hills.

• Sediments were also deposited in valleys and troughs of the Rockies, but most are eroded now.

• Excellent discoveries of Tertiary vertebrates/mammals occur, especially in the Cypress Hills region, with over 100 species known.

Counterintuitive Preservation Pattern

• High elevations preserve older deposits.

• Lower areas were preferentially eroded.

• Opposite of the common expectation that older rocks occur only at depth.

Tertiary Fossils in Alberta

Pembina River

• Excellent location for collecting fossil plants.

• Fossil leaves preserved in gray mudstones.

• Preservation quality often exceptional.

• No permit required for casual collecting.

Other Local Fossils

• Shells.

• Plant remains.

• Mammals.

• Fish.

• Turtles.

• Ants.

• Primates.

Blackmud Creek

• Dinosaur fossils excavated close to the modern surface.

• Fossil beds found with minimal excavation.

Dry Island Buffalo Jump Provincial Park

• Excellent exposure of Paskapoo Formation.

• Shows sandstone units and coal-bearing strata.

• Modern river erosion exposes the formations.

Coal Mining

• Large-scale mining occurred in Paskapoo deposits.

• Obed area especially important.

Fossil Ant Discovery

• Fossil ant discovered in Tertiary deposits.

• Preserved body structures include:

  • Mandibles.

  • Legs.

  • Abdomen.

Fossil Turtles

• Found near Calgary and Red Deer.

• Shells usually fragment during burial and compaction.

• Fossils often occur as scattered shell fragments.

Fossil Fish

• Well-preserved fish fossils known from deposits of similar age.

• Fine-grained sediments allow exceptional preservation.

Fossil Mammals:

• Hollow teeth were found in specific mammals (poisonous shrews):

  • Teeth may have delivered venom.

  • Similar to venomous modern mammals.

  • After biting, the teeth may have excreted poison into its victim.

• Possible uses:

  • Defense.

  • Predation.

  • Research led by Richard Fox.

  • Fossils include:

    • Tiny shrew-like mammals.

    • Early primates.

    • Other Paleocene mammals.

Cypress Hills Gravels and Conglomerates

• Cypress Hills preserve thick conglomerates.

  • They’re capped by these thick conglomerates.

• Contain large cobbles that seems to have covered the entire province. You need high velocity water to transport coarse rocks long distances.

• Represent highly energetic depositional systems.

Evidence for High-Energy Transport

• Large cobble sizes.

• Deep scour surfaces.

• Percussion marks on cobbles.

• Cobbles collided during transport.

• Must have been fast-moving, high velocity water to bang huge rock together and form large scours.

Major Geological Question

• How were large cobbles transported across such large portions of Alberta?

• Especially puzzling because coarse material is usually deposited near mountain sources.

Interpretation 1

• Cobbles sourced from:

  • Sweetgrass Hills.

  • Bearpaw Mountains.

• Transported by braided rivers that produced the conglomerates and glaciers would come and erode, hence letting a few areas of these deposits preserved (like Cyprus Hills).

• Later modified by glacial erosion.

• Limitation:

  • Difficult to explain province-wide distribution.

  • Sweetgrass hills and Bearpaw Mountains don’t occur everywhere in the province… which is why it falls short in terms of interpretation.

Interpretation 2

• Mountains were once significantly higher.

• Massive erosion removed several kilometers of rock (3km-10km according to this interpretation… but this much erosion seems unrealistic).

  • Uplift and heavy erosion occurred during this time and were deposited across the plains in braided rivers.

• Braided rivers spread sediments across Alberta.

• Later glaciation modified the landscape further.

• Helps explain widespread gravel distribution.

Archaeological Significance of Gravels

• Indigenous peoples utilized cobbles for:

  • Knives.

  • Spear points.

  • Axe heads.

  • Other stone tools.

• Archaeological surveys around Swan Hills examine:

  • Resource extraction sites.

  • Processing areas.

  • Trade networks.

  • Tool production.

Transition to Quaternary Glaciation

• Final topic of the course.

• Focus shifts from Tertiary deposits to glacial processes.

Basic Glacier Structure

Accumulation Zone

• High-elevation region.

• Snow and ice continuously added.

• Ice persists year-round.

• Always stays cold enough so the glacier doesn’t disappear.

Ablation Zone

• Lower-elevation region.

• Ice lost through melting and sublimation.

• Net decrease in glacier mass.

• The area where the glacier loses ice.

• There is a elevation change between the Accumulation Zone (higher up) and the Ablation Zone (lower).

Glacier Head

• Thickest portion of glacier.

• Located in accumulation zone.

Crevasses

• Large fractures within glacier ice.

• Form as flowing ice deforms and breaks.

• Cracks in the ice.

Ice Channels:

• Inside glaciers… has channels.

Glacier Safety

• Glaciers are extremely dangerous.

• Hazards include:

  • Deep crevasses.

  • Hidden meltwater channels.

  • Ice collapse.

• Walking on glaciers without training or guides strongly discouraged.

Glacier Movement:

• Along the base, there is often pressure melting → forms a liquid interface where it continuously freezes (to the sediment) and thaws.

• That sediment is accumulated into the ice as it flows along.

Glacial Erosion Mechanisms

Plucking

• Ice freezes onto bedrock or sediment.

• Material becomes incorporated into glacier.

• Material removed as glacier moves.

Abrasion

• Rocks frozen into glacier scrape underlying bedrock.

• Produces scratches and grooves.

Moraines

• Sediment transported within ice.

• Deposited when glacier melts.

• Sediment that was accumulated within the ice… which melted out at the abrasion area.

Pleistocene Ice Sheets

Laurentide Ice Sheet

• Covered most of Canada.

• Main ice sheet affecting Alberta.

Cordilleran Ice Sheet

• Mountain-based glacier system.

• Associated with western mountains.

Modern Alberta Glacier Examples

• Angel Glacier at Mount Edith Cavell.

• Columbia Icefield.

Effects of Glacial Erosion

• River valleys widened and deepened.

• V-shaped valleys converted into U-shaped valleys.

• Mountain landscapes became more rugged.

• Topography becomes more jagged.

Horn

• Sharp peak formed by erosion from multiple directions.

Arête

• Narrow ridge between glacial valleys.

Cirque

• Bowl-shaped depression formed by glacier erosion.

Truncated Spur

• Ridge cut off by a glacier.

• Arete that been chopped off by the main glacier.

Hanging Valley

• Tributary valley left elevated above main valley.

Tarn

• Small lake occupying a former cirque basin.

Striations

• Scratches carved into bedrock by glacier movement.

• Record ice-flow direction.

• Used to reconstruct glacial movement patterns.

Erratics

• Large rocks transported by glaciers.

• Deposited far from original source.

Big Rock

• Famous glacial erratic in Alberta.

• Composed of Gog Group quartzite.

• Recognized as the world's largest erratic.

• The world’s largest erratic.

Drumlins

• Streamlined hills formed beneath glaciers.

  • Pushes the sediment, gets over the sediment, and goes.

• Indicate direction of glacier movement.

• Common near Calgary.

• Visible from Highway 2.

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