42:161 Historical Geology - Final Exam

Lithostratigraphy

• The element of stratigraphy that deals with the description and systematic organization of the rocks of the Earth’s crust into distinctive units based on the lithologic character of the rocks and their stratigraphic relations

Lithostratigraphy Fundamental Rock Unit

• Formation

Formation

• Body of rock identified by lithic characteristics and stratigraphic position

• Mappable at the Earth’s surface or traceable in the subsurface

• Basic mappable lithostratigraphic unit

Chronostratigraphy

• Branch of stratigraphy that deals with the age of strata and their time relations

Chronostratigraphy Fundamental Rock Unit

• Eonthem

  • Erathem

    • System

      • Series

        • Stage

Biostratigraphy

• Element of stratigraphy that deals with the distribution of fossils in the stratigraphic record and the organisation of strata into units on the basis of their contained fossils

Biostartigraphic Fundamental Rock Unit

• Biozone

Correlation Methods in Stratigraphic Analysis

• Continuity to exposure

• Seismic

• Marker beds

• Fossils

Correlation Method - Continuity to Exposure

• Established by walking along the outcrop

• Arial surveys: plane, helicopter, satellite

Correlation Method - Seismic

• Seismic reflection

• Imaging the subsurface

• Earth’s x-rays - determines stacking patterns

Correlation Method - Marker Beds

• Litho-/chrono-correlation

• Examines volcanic ash beds or lava flows

• Can be dated, can establish date of beds

Correlation Method - Fossils

• Bio-correlation

• Correlating rock units

• Used to set up geologic time table

Marine Regression

• Causes superposition of nearshore facies over offshore facies

Graded Bedding

• An upward decrease in grain size in a single bed

Good Sedimentary Structures that Indicate Paleocurrent Directions

• Cross bedding

• Ripple marks

• Graded bedding

• Mud cracks

Sedimentary Structure - Cross Bedding

• Series of inclined bedding planes that have relationship to the direction of current flow, angle of rest of sediment and the rate of supply of sediment

• Common in desert, river, and shallow marine environments

Sedimentary Structure - Ripple Marks

• Undulations produced by fluid movement over sediments

  • Current ripple - Uni-directional → asymmetrical, rivers

  • Wave ripple - Bi-directional → symmetrical, ocean or lake waves

Sedimentary Structure - Graded Bedding

• Sedimentary unit or bed which displays a sorting effect

  • Coarsest material at the base and the finest material at the top

Sedimentary Structure - Mud Cracks

• Irregular fracture in a crudely polygonal pattern, formed by the shrinkage of clay, silt or mud, generally in the course of frying under the influence of atmospheric surface conditions

Outgassing

• Process whereby an early atmosphere is formed by volcanism

Canadian Shield

• Largest exposed area of craton in North America

Photosynthesis by Cyanobacteria

• Process responsible for at least some free oxygen in Earth’s early atmosphere

Archean Eon

• Ended 2.5 billion years ago

BIFs (Banded Iron Formations)

• Sedimentary rocks consisting of alternating layers of iron minerals and chert

Trans Hudson Orogen

• Where Superior and Hearne provinces collide

Most Significant Biologic Event During Proterozoic

• Appearance of eukaryotic cells

Red Beds

• One indication that free oxygen was present in the Proterozoic atmosphere

Late Proterozoic

• Most extensive global glaciation

Oceans/Ocean-Atmosphere Interface (Primordial Ocean)

• Hypothesised location where the earliest organisms originated

  • Due to most organisms being composed of C, H, N, and O, all of which were present in Earth’s early atmosphere in the form of CO2, H2O, N2, CH4, and NH3

Undersea Hydrothermal Vents

• Hypothesised location of where life evolved

  • Microbes called hyperthermophiles

    • Supported by variety of inverts → shrimp-like arthropods, crabs, clams, and tube worms

Inorganic Molecules Present in Early Earth

• CO2 - Carbon dioxide

• H2O - Water vapour

• N2 - Nitrogen

• CH4 - Methane

• NH3 - Ammonia

Proterozoic - Earliest Prokaryotes

• Blue-Green Algae or cyanobacteria

  • Asexual reproduction

  • Little diversification, slow-paced evolution

Stromatolites

• Photosynthesising organisms

  • Made from blue-green algae or cyanobacteria

• Early Archean - 3.5 bya

Proterozoic - Earliest Eukaryotes

• Single celled

• Sexual reproduction

• Faster rate of evolution

• Middle Proterozoic → 1.4 - 1.6 bya

Proterozoic - Multicellular Eukaryotes

• Metazoans

• Ediacaran fauna

• Molds, casts, imprints, trace fossils

• Late Proterozoic

• 670 - 570 Mya

Skeletonization

• Small shelly fauna debris

• Latest Proterozoic

Proterozoic - Evolutions “Big Bang”

• Cambrian explosion of life

• All principal animal phyla

• Shelled invertebrates → For protection and became larger

• Abundant fossil fragments

• 530 - 520 Mya

Palaeozoic - Eastern North America

• Shift from passive to active

• 3 major orogenic events

  • Taconic

  • Acadian

  • Alleghanian

Palaeozoic - Taconic Orogeny (Eastern)

• Late Ordovician → 470 - 440 Ma

• Convergent plate boundary

• Collision of an island arc with eastern Laurentia

• Global plate movement → Closure of the lapetus ocean

• Effects → Uplift and deformation of Appalachian margin, thrust faulting

Palaeozoic - Acadian Orogeny (Eastern)

• Middle Devonian → 390 - 360 Ma

• Continental collision

• Collision of Avalonia with Laurentia

• Global plate movement → Continued convergence across closing of lapetus ocean

• Effects → Further uplift of northern and central Appalachians, intense folding, faulting, and metamorphism

Palaeozoic - Alleghanian Orogeny (Eastern)

• Late Carboniferous-Permian → 325 - 260 Ma

• Continent-continent collision

• Collision of Gondwana with Laurentia during formation of Pangaea

• Gloabal Plate Movement → Closure of the Rheic ocean

• Effects → Development of massive thrust belts and fold-and-thrust zones

Palaeozoic - Taconic Orogeny

• Passive to active margin

• Reversal of plate motion

• Laurentia and Baltica move together

• Subduction of Iapetus ocean plate

• Thrusting, folding

• Queenstone delta

• Ordovician

Palaeozoic - Caledonian Orogeny

• Mirror image event to taconic in baltica

• Silurian

Palaeozoic - Acadian Orogeny

• Laurentia and Baltica collide

• Iapetus ocean closed

• Thrusting, folding, metamorphism

• Catskill clastic wedge/delta deposited

• Devonian

Palaeozoic - Ouachita Orogeny

• Gondwana collides with Laurentia

• South America and Central America collide with North America

• Thrusting, Folding

• Carboniferous

Palaeozoic - Allegheny Orogeny

• Final Suturing of Gondwana and Laurasia

• Africa collides with Southeast North America

• Thrusting and Folding → create Southern Appalachians

• Pangaea formed

• Permian

Palaeozoic - Rifting & Drifting

• Triassic rifting and volcanism (Ns to NC)

• Jurassic opening of Atlantic: Reverse. zipper

• Atlantic opens from south to north

• Eastern margin becomes passive

• North America drifts westward

Cratonic Sequence (Sloss Sequence)

• Major transgressive-regressive cycle bounded by cratonwide uniformities

Creation of Taconic Orogeny

• Oceanic-Continental Convergent Plate Boundary interaction

Orogenic Belt

• Elongated area marking the site of mountain building

Sauk Transgression

• Cambrian geological event

Canadian Shield

• During deposition of the Sauk sequence, only area above sea level besides Transcontinental arch was this area

Occurred During Cretaceous

• Greatest post-Paleozoic inundation of the craton

Late Carboniferous & Early Permian

• Extensive continental glaciation of the Gondwana continent

Cyclothems

• Rhythmically repetitive sedimentary sequences

• Pennsylvanian deposits

• Main economic deposit → Coal

Ural Mountains

• Formed by Hercynian orogeny

Antler Orogeny

Passive Margin

Island Arc Collision

Thrusting of Antler Mountains

Devonian

Ancestral Rockies

Passive Margin

Basement Block Faulting (Near Vertical)

Response to Eastern Margin Collisions

Pennsylvanian

Sonoma Orogeny

Passive Margin

Island Arc Collision

Thrusting of Sonoma Mtns

Permian-Triassic

Nevadan Orogeny

Active Margin (Convergent)

Accreted Terranes

Thrusting, Folding, Batholith Intrusions

Foreland Basin Develops

Jurassic-Cretaceous

Sevier/Columbian Orogeny

Active Margin (Convergent)

Accreted Terranes

Thrusting, Folding, Batholith Intrusions

Foreland Basin Fully Developed

Cretaceous

Laramide Orogeny

Active Margin (Convergent)

Accreted Terranes

Thrusting, Folding

No Batholithic Intrusions

Shallow Subduction

Spreading Center or Mantle Plume

Foreland Basin Infilling

Cretaceous-Tertiary

K-T Mass Extinction Animal Groups

• Triceratops

• Sauropods

• Pterosaurs

• Mosasaurs

• Plesiosaurs

• Ammonites

• Belemnites

K-T Extinction Theories

• Asteroid Impact Hypothesis

• Volcanism hypothesis

• Climate change

• Sea-level regression

K-T Extinction Theory Evidence - Asteroid Impact

• Iridium layer worldwide

• Shocked quartz

• Chicxulub crater

• Soot and ash layer worldwide

• Sudden extinctions

K-T Extinction Theory Evidence - Volcanism

• Prolonged volcanic eruptions in India released massive amounts of CO2

• Mercury anomalies

• Stepwise extinctions → gradual extinctions

K-T Extinction Theory Evidence - Climate Change

• Fossil record and isotopic data show cooling trend

K-T Extinction Theory Evidence - Sea-Level Regression

• Geological data shows widespread sea-level fall leading to loss of continental shelf environments

• Changes in ocean circulation and chemistry

Mesozoic Tectonic History of North American Cordilleran Region

• Complex and involves convergence (oceanic-continental crust)

• Exotic terrane accretion

Nevadan

• First Mesozoic orogeny in Cordilleran region

Nevadan Orogeny

• Sierra Nevada, Southern California, Idaho and Coast Range batholiths were formed as a result of this orogeny

Sundance Sea

• Jurassic sea floods North America

Laramide Orogeny

• Responsible for the present-day Rocky Mountains

Iridium Anomaly

• Cited as evidence for meteorite impact at the Cretaceous-Tertiary boundary

Paleogene

• Africa collides with Europe

Himalayas Formation

• When Indian and Eurasian plates collided

Neogene

• Colorado Plateau uplifted

North American Cordillera

• Complex mountainous region region in the western USA and Canada

Miocene

• Mediterranean sea evaporates

Isostatic Rebound

• Phenomenon in which Earth’s crust rises after unloading

Varves

• Fine-grained deposits in glacial lakes accumulate as dark-light couplets

Moraine

• Sediment deposited directly by glaciers

Glacial Lake Agassiz

• Quaternary Period