EAS 209 - Lecture 30

Barnum Brown

• Lived from 1873–1963.

• Worked for the American Natural History Museum.

• Grew up on a farm.

• Family reportedly struggled to choose a name for him after birth.

• Eventually named after P.T. Barnum of Barnum Circus when the circus passed through town.

• Attended Kentucky University.

• Became involved in fossil collecting while assisting a professor with fieldwork.

• Quickly demonstrated exceptional skill at locating fossils.

• Developed a reputation as a naturally gifted fossil hunter.

• Enjoyed fieldwork far more than classroom-based academic work.

• Obtained employment with the American Natural History Museum while still at university.

• Left university temporarily to pursue fossil collecting professionally.

• Later accepted into graduate studies at Columbia University despite not having completed his undergraduate degree.

• Did not complete graduate studies and eventually left Columbia.

• Ultimately returned to Kentucky University and completed his undergraduate degree.

• Became one of the most successful fossil collectors in history.

• Discovered Tyrannosaurus rex.

• Discovered numerous other dinosaur fossils.

• Many major dinosaur museum collections around the world originated from fossils collected by Barnum Brown.

• Contributed substantially to the development of dinosaur paleontology.

• Known for conducting fieldwork while wearing a large fur coat.

• Demonstrates that scientific success can come through exceptional field skills, not only academic study.

• Recognized as an important scientist despite not following a conventional academic path.

The Cretaceous Within the Zuni Sequence

• The Cretaceous belongs to the Zuni Sequence.

• Sea level continued rising through much of the Cretaceous.

• Peak sea level occurred during the middle-to-late Cretaceous.

• At maximum flooding:

  • Marine waters extended from the Cordillera in western North America to the Appalachians in the east.

  • Much of the continent was submerged.

• Minor unconformities occurred during the sequence.

• These unconformities did not necessarily extend across the entire continent.

• After maximum flooding:

  • Sea level began to fall.

  • Regression followed the transgressive phase.

Global Geography During the Cretaceous

• Example shown at approximately 100 million years ago.

• Pangea was actively breaking apart.

• South America and Africa were separating.

• North America was split by a major inland seaway.

• Antarctica still existed as a recognizable landmass.

• India was isolated and moving northward.

• India eventually collided with Asia.

• Collision between India and Asia formed the Himalayas.

• By approximately 80 million years ago:

  • Continental positions more closely resembled modern geography.

  • Inland seaway still divided North America.

  • Global sea level remained very high.

• Comparison between 100 Ma and 80 Ma demonstrates continued sea-level rise during the Cretaceous.

Completion of Cordilleran Assembly

• By the Cretaceous, most terrane accretion had already occurred.

• Major components of British Columbia had largely assembled.

• Components included:

  • Island arcs.

  • Ancient ocean floor fragments.

  • Continental fragments.

  • Submarine deposits.

• Most of modern British Columbia was already present by this time.

Foreland Basin Formation

• Himalaya–India collision used as an analogy.

• Collision concentrates large amounts of crustal mass.

• Concentrated mass causes loading of the lithosphere.

• Lithosphere bends downward adjacent to mountain belts.

• Resulting depression forms a foreland basin.

• Similar process occurred beside the Cordillera.

• Accreted terranes and mountain building loaded western North America.

• Weight of mountains caused crustal sagging.

• Sagging created the Alberta Foreland Basin.

Alberta Foreland Basin

• Primary location of Cretaceous sediment accumulation.

• Formed because of loading associated with Cordilleran mountain building.

• Basin was:

  • Wide.

  • Stable.

  • Long-lived.

• Stability allowed development of:

  • Rivers.

  • Deltas.

  • Coastal plains.

  • Swamps.

• Basin experienced relatively little tectonic activity after formation.

• Became an ideal sediment trap.

• Note: the Rocky Mountains is also known as the Foreland (Fold and Thrust) Belt.

Cordilleran Belts

• Rocky Mountain Belt.

• Omineca Belt.

• Intermontane Belt.

• Coast Belt.

• Insular Belt.

• These belts reflect different tectonic terranes and geological histories within the Cordillera.

Change in Sediment Transport Direction

• Earlier Paleozoic successions commonly received sediment from the east.

• Development of the Cordillera created a new western highland source.

• During the Cretaceous:

  • Sediment was shed from west to east.

  • Newly uplifted mountains became major sediment suppliers.

• Sediment transport direction therefore reversed compared to many earlier intervals.

Important Structural Features

Sweetgrass Arch

• Remained an important structural high.

• Eventually submerged during marine transgressions.

• Continued influencing sediment distribution.

Peace River Arch

• Previously became a basin during Carboniferous time.

• Retained structural influence.

• Continued affecting sedimentation patterns.

Foreland Fold and Thrust Belt

• Rocky Mountain Belt also referred to as the Foreland Fold and Thrust Belt.

• Area where rocks became:

  • Folded.

  • Faulted.

  • Thrust upward.

• Represents the deformational front of mountain building.

Stratigraphy Column:

• Although the Nikanassin and Kootenay Formations are not completely Cretaceous in age.

  • Transverse that.

Cretaceous Stratigraphy Overview

• Divided into:

  • Lower Cretaceous.

  • Upper Cretaceous.

• Numerous regional formation names exist.

• Names vary between:

  • Outcrop regions.

  • Subsurface regions.

  • Different geographic areas.

• Important stratigraphic intervals include:

  • Aptian.

  • Albian.

  • Campanian.

  • Maastrichtian.

Relationship to Dinosaur Provincial Park Units

• Belly River Group discussed previously.

• Included:

  • Oldman Formation.

  • Dinosaur Park Formation.

  • Bearpaw Formation.

• These units occur higher in the Cretaceous succession.

• Current lecture focuses on older Lower Cretaceous units.

Jurassic–Cretaceous Boundary Units

• Nikanassin Formation.

• Kootenay Formation.

• Both span the Jurassic–Cretaceous boundary.

• Unique because they cross the period boundary rather than lying entirely within one system.

Major Sub-Cretaceous Unconformity

• After Nikanassin deposition, a major period of erosion occurred.

• Created a province-wide unconformity.

• Represents a substantial gap in the geologic record.

• Mountain building produced uplift and exposure.

• Erosion removed large amounts of rock.

• Unconformity extends across Alberta.

• One of the most important surfaces in the western Canadian sedimentary basin.

Cadomin Formation

• First major deposit above the sub-Cretaceous unconformity.

• Represents earliest Cretaceous sedimentation after mountain building.

• Consists largely of conglomerate.

• Dominated by:

  • Quartzite clasts.

  • Chert clasts.

• Very coarse-grained.

• Contains abundant rounded pebbles.

• Clast rounding indicates transport and abrasion.

• Material likely eroded from uplifted Rocky Mountain source rocks.

Source of Cadomin Clasts

• Chert likely derived from:

  • Permian deposits.

  • Pennsylvanian deposits.

• Quartzite may have been derived from:

  • Gog Group quartzites.

  • Other resistant quartz-rich units.

• Represents erosion of uplifted mountain belts.

Angular Unconformity

• Mountain building tilted older strata.

• Erosion truncated tilted beds.

• Cadomin Formation deposited directly on eroded surface.

• Relationship forms an angular unconformity.

• Older rocks exposed at the surface ranged from:

  • Cambrian.

  • Ordovician.

  • Devonian.

  • Carboniferous.

  • Permian.

  • Triassic.

  • Jurassic.

• At the beginning of the Cretaceous these rocks could have been exposed simultaneously at the land surface.

Cross-Section Through the Foreland Basin

• Mountain loading created major subsidence adjacent to the Cordillera.

• Thickest Cretaceous deposits accumulated closest to the mountains.

• Basin deepened toward the mountain front.

• Some Paleozoic units formed structural highs.

• Examples include:

  • Rundle Group.

  • Banff Formation.

  • Wabamun Group.

  • Winterburn Group.

• These highs influenced later sedimentation.

Origin of the Oil Sands

• McMurray Formation.

• Clearwater Formation.

• Grand Rapids Formation.

• Lower Manville Group.

• Important hosts of Alberta oil sands.

• Contain bitumen-rich sandstones.

• Bitumen is highly viscous.

• Requires:

  • Surface mining.

  • Steam-assisted recovery methods.

• Different from conventional oil fields such as Leduc.

• This angular unconformity is underlain by NW-SE trending subcrop belts that are progressively older from SW to NE.

• The mountains pushed down all the deposits.

• The squiggly line is the start of the Cretaceous.

• The deposits in the Foreland Basin are thick. All the heaviness from the mountains formed a depression.

• Moving east to northea

• Asst → the Rundle, Banff, Wabamun, and Winterburn form a high.

  • Ends up bisecting the province.

Paleo-Highs and Sediment Distribution

• Structural highs remained exposed during early Cretaceous sedimentation.

• McMurray deposits filled low areas and valleys.

• Deposits did not immediately cover all highs.

• Different formations accumulated on opposite sides of structural highs.

McMurray–Gething Relationship

• McMurray Formation deposited on one side of the structural high.

• Gething Formation deposited on the other side.

• Units are time-equivalent.

• Deposited simultaneously.

• Differ only because they formed in different geographic areas.

• As time progresses, there is a sea level rise.

Fish Scale Zone:

• A zone of fish debris practically covers the whole province as time continues to go on.

Lower Mannville Group

• Thickness maps reveal locations of paleo-highs.

• Following a period of erosion, invasion of the Boreal Sea occurred.

• Deposits become thinner approaching highs.

• Thick deposits accumulated in low areas.

• Thickness therefore provides clues to ancient topography.

Cadomin Depositional Environment

• The first unit to be deposited was the Cadomin Formation, a quartzite plus chert pebble conglomerate.

• Cadomin Formation repesents alluvial fan and braided stream deposits flowing to NE.

• Interpreted as an alluvial fan system.

• Deposited along the base of newly formed mountains.

• Alluvial fans formed from:

  • Seasonal runoff.

  • High-gradient streams.

  • Rapid erosion of uplifted terrain.

• Deposits spread outward from point sources.

• Comparable to cones of rubble seen along mountain fronts today.

Characteristics of Alluvial Fans

• Mostly subaerial.

• Formed on land.

• Different from submarine fans.

• Contain coarse sediment.

• Deposited rapidly.

• Commonly associated with:

  • High relief.

  • Steep gradients.

  • Active erosion.

Evidence Supporting Alluvial Fan Interpretation

• Extremely coarse grain size.

• Conglomeratic composition.

• Limited geographic extent.

• Thickest near mountain front.

• Rapid thinning away from source.

• Strong relationship to uplifted Cordillera.

Cadomin Thickness Distribution

• Thickest adjacent to mountains.

• Braided stream and braidplain deposits at foot of new mountains.

• Does not extend across all of Alberta.

• Restricted to western portions of the basin.

• Fox Creek Escarpment marks approximate eastern limit.

• Grain size becomes finer farther from source.

• Demonstrates decreasing transport energy away from mountains.

• Apron being formed through the erosion of the Rocky Mountains.

• Flowing to the NE; thickness trends show Peace River Embayment was still active.

Cadomin Outcrop Examples

Hell's Gate Gorge

• Near Grand Cache.

• Displays thick Cadomin conglomerates.

• Excellent exposure of alluvial fan deposits.

Kakwa Falls

• Southwest of Grande Prairie.

• Cadomin forms resistant cap rock.

• Softer sandstone and shale occur beneath.

• Water preferentially erodes softer units.

• Creates overhangs and cave-like features.

Punchbowl Falls (Jasper Area)

• Displays thick Cadomin conglomerate section.

• Demonstrates large volume of sediment shed from early Rocky Mountains.

Transition to Gething and McMurray Deposition

• After Cadomin deposition:

  • Large fluvial systems developed.

  • Major rivers crossed the foreland basin.

• Depositional environments included:

  • Meandering rivers.

  • Floodplains.

  • Swamps.

  • Deltas.

• River sands later became important oil-sand reservoirs.

Oil Sands Reservoirs

• Hosted primarily within river-related sandstones.

• Point-bar deposits especially important.

• Meandering river systems produced extensive porous sand bodies.

• These sand bodies later became reservoirs for bitumen accumulation.

Drainage Systems

• Gething Formation sediments redistributed by NW-SE channels.

• Spirit River Channel.

• Edmonton Channel.

• Peace River Channel.

• Large river valleys transported sediment across the basin.

• Rivers occupied low areas between structural highs.

• A lot of these deposits have water in them.

Preservation of Continental Deposits

• River migration buried floodplains and swamps.

• Burial preserved:

  • Coal.

  • Plant material.

  • Dinosaur remains.

  • Floodplain sediments.

• Preservation of continental environments is less common than marine environments.

Reading Manville Cross Sections

• Root symbols indicate vegetated land surfaces.

• Bell-shaped bodies represent river channels.

• Coal layers represent swamps.

• Gray shales represent marine incursions.

• Stacked deposits record changing environments through time.

Marine Transgression

• Sea level rose during deposition.

• Boreal Sea advanced southward.

• Marine shales became widespread.

• Shoreline deposits developed.

• Eventually marine influence spread across much of the basin.

Coal Formation Review

• Swamps accumulated plant debris.

• Organic matter became peat.

• Burial compressed peat.

• Water and volatile compounds removed.

• Coal formed through compaction and heating.

Paleogeography During Gething–McMurray Time

• Mountains located to the west.

• Spirit River valley ran roughly parallel to mountain front.

• Extensive fluvial systems occupied the basin.

• Structural highs remained exposed.

• Inland sea periodically advanced from the north.

• Deltas formed where rivers entered marine waters.

• Towards the east, it thins as it onlaps a high or spine of resistant carbonates.

Glauconite

• With continuing transgression of the Boreal Sea, the Gething grades into Glauconite.

• A green mineral diagnostic of marine conditions.

• Marine mineral.

• Associated with the Boreal Sea.

• Indicates marine conditions.

• Presence confirms marine incursions into the basin.

ANS: False