Sedimentology (ESCI 332)

Clastics:

•Dr. John Anderson and TA Jason Francis

•~ First 7 weeks of semester (minus 3)

•Me: Julia Smith Wellner; Room 203F, jksmith@rice.edu, 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)

adapted from Van Wagoner et al., 1990; http://www.uga.edu/~strata/sequence/parasequences.html

Lateral and vertical facies relationships:

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