GEOL 340 Sedimentology and Stratigraphy
Lecture 3
1. Stratification and Bedforms
2. Historical Benchmarks
Stratification and Bedforms
Bed = strata = tabular or lenticular layers of sedimentary rock with fabrics and textures distinct from the directly overlying and underlying rock
Bedding planes or bounding planes = the upper and lower planer surfaces surrounding beds
Stratal Geometry = overall shape of a bed or series of beds
Thickness Units
lamina = < 1 cm
very thin bed = 1 - 3 cm
thin bed = 3 - 10 cm
medium bed = 10 - 30 cm
thick bed = 30 cm - 1 m
very thick beds = > 1 m
Historical Benchmarks
Initial Work
Leonardo Da Vinci (~1500 A.D.) fossils in limestones of the Italian Appenines
Nicolas Steno (1669) fossils around Rome, Italy
a. Principle of Superposition = oldest at the bottom
b. Original Horizontality = initial horizontal deposition (note
seafloor exceptions)
Robert Hooke (also 17th century) in England
a. first microscope study of fossils
b. suggested biostratigraphic dating (use of fossil successions)
Giovanni Arduino (Italian) and Johann Gottlab Lehman (German)
in 1700's
a. first general concept of lithostratigraphic ordering by age
b. primary, secondary, tertiary (Tertiary), alluvium (Quaternary)
Uniformitarianism versus Catastrophism: Biostratigraphy and Correlation
Uniformitarians
James Hutton (1727-1797) Scottsman
a. Geologic Cycle = continuous process of uplift, erosion, transport
and deposition
b. Uniformitarianism (actualism) = modern processses are the key
to the past
William "Strata" Smith (1769-1839) English surveyor
a. father of modern stratigraphic concepts
b. Faunal Succession = orderly fossil successions
Albert Oppel (1856) German geologist
a. Biozone = small-scale subdivisions of stages based on overlapping
ranges
Catastrophists
Georges Cuvier (1811) Paris Basin
a. Catastrophism = punctuated series of abrupt events not continuously
operating in the modern
Alcide d'Orbigny (1842) French
a. Biologic Stages = systematic subdivisions of strata
Combined work lead to a global Standard Stratigraphic Column
Petrography and Petrology
Henry Clifton Sorby (1850) siliciclastic petrography and structures
a. Petrography = description and classification of thin sections
under a microscope
b. Thin Sectons = ~30 mm wafer of rock on a glass slide
c. predated extensive applications to igneous and metamorphic
rocks
Early 1900's sedimentology, stratigraphy and petrography milestones
a. Lyell (1833)
b. T.C. Chamberlin (1886)
c. Grabau (1913)
d. Twenhofel, (1926; 1932)
e. Lucien Cayeux (1929; 1931; 1935)
f. Wentworth (1933) grain size analyses
g. Bagnold (1941) hydrologic analyses
Early Cruises
Louis Agassiz (1840) and the H.M.S. Challenger
Charles Darwin (1831-1836) and the H.M.S. Beagle
Geologic Revolution of the 1950's and 1960's
Seafloor Spreading and Global Plate Tectonics =
rigid crust in distinct plates moving over a plastic mantle
a. Mid-Ocean Ridges = spreading centers
b. Subduction Zones = one plate plunges beneath another
Drilling Programs
a. Deep Sea Drilling Program (DSDP; 1963) with Glomar Challenger
b. Ocean Drilling Program (ODP; 1985) with JOIDES Resolution
Hydrocarbon (Oil and Gas) Exploration
a. Shell, Amoco, Exxon