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Sedimentology (ESCI 332)
Clastics:
•Dr. John Anderson and TA Jason Francis
•~ First 7 weeks of semester (minus 3)
•Me: Julia Smith Wellner; Room 203F,
[email protected], x2686
•First week of class, two weeks in February
Carbonates:
•Dr. André Droxler and TA Michelle Shearer
•~ Last 7 weeks of semester
Schedule is subject to change!
Lab:
•Fridays 1-4 pm
•Taught by the TAs
•No lab this week
Fieldtrips:
•Several short trips throughout the semester!
Grades:
•Lab grade goes into overall grade
•Clastics portion will have two take-home, essay exams
•More about Carbonates grading later
Books:
•None, notes handed out in class for Clastics
•More on Carbonates later
Any questions on logistics?
Introduction to Facies Concepts
What is sedimentology?
•Scientific study of the classification, origin, and
interpretation of sediments and sedimentary rocks.
•Physical, chemical, and biologic properties of sediments and
sedimentary rocks.
What is stratigraphy?
•Science of rock strata.
•Age relationships of strata, successions of beds, local and
worldwide correlation of strata, and stratigraphic order and
chronological arrangement of beds in the geologic column.
Who uses sedimentology and stratigraphy?
•All types of geologists!
•paleoceanographers, geochemists,
paleontologists
•structural geologists
•glacial geologists, sea-level change studies
•hydrologists, petroleum geologists--define
units in subsurface
•Need to know facies associations...
Walther’s Law (1894):
•Johannes Walther pioneered the study of modern
environments as a tool for interpreting sedimentary strata.
The various deposits of the same facies area and similarly
the sum of the rocks of different facies areas were formed beside
each other in space, but in crustal profile we see them lying on top
of each other.
i.e., Conformable vertical successions of strata also
occurred in laterally adjacent environments.
•This does not mean that any vertical succession will
always reproduce the horizontal succession of environments, but
that only those facies now forming side by side could be
superimposed vertically. (adapted from Middleton, 1973)
Lateral and vertical facies relationships:
adapted from Van Wagoner et al., 1990; http://www.uga.edu/~strata/sequence/parasequences.html
Why is knowing the facies relationship so important?
•Often, geologists work in the subsurface, need to define
the shape and lateral extent of sedimentary units.
Meandering river, dip-aligned
Coastal barrier, strike-aligned
How do we define facies and interpret depositional
environments?
Direct Indicators:
•fossils, including trace fossils
•grain size distributions
•sedimentary structures
•mineralogy of grains
Indirect Indicators:
•electric log shapes
•high-resolution seismic data
Biofacies: facies defined mainly with paleontologic information
Lithofacies: facies defined mainly with sedimentologic criteria
Seismic Facies: facies defined mainly on seismic data
Each of these factors is non-unique and a meandering
river can have the same grain size as a coastal barrier.
Certain fossils are unique to a given environment, but
can’t count on finding these.
Therefore: •use multiple criteria
•use the vertical succession of characteristics to
define the facies
•Grain size and sedimentary structures provide evidence of
how the grains were transported and deposited. It is another step
to interpret the environment of deposition.
References used throughout for Class 1:
•332 notes from Anderson
•Principles of Sedimentology and Stratigraphy (3rd Edition),
Boggs
•Principles of Sedimentology, Friedman and Sanders