12: Stratigraphy
- Page ID
- 20966
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Stratigraphy is the study of the geometric relationships, composition, origin, age, and relationships between stratified rocks deposited at the surface of the Earth. We will begin with an overview of different types of unconformities and geologic contacts and then move on to a discussion of the most common approaches to subdivide and classify sedimentary rocks. These schemes are based on lithology (lithostratigraphy), fossils (biostratigraphy), depositional trends (sequence stratigraphy), or seismic reflection data (seismic stratigraphy).
Many of the concepts described in this chapter are described in more detail in the North American Stratigraphic Code.
- Identify different types of contacts and unconformities and explain their implications for reconstructing the geologic history of an area.
- Identify and describe the different types of lithostratigraphic contacts and units.
- Identify and describe the different types of biozones
- Describe a complete sea level cycle using sequence stratigraphic terminology and the concepts of accommodation and sediment supply.
- Identify the main geometries of seismic reflectors and use them to subdivide packages of rock into seismic sequences
- 12.1: Review of unconformities and other types of contacts
- The three major types of unconformities are angular unconformities (angular discordance between layers), nonconformities (sedimentary deposited atop deep-formed crystalline rocks), and disconformities (sedimentary atop sedimentary with no obvious angular discordance). Recognition of contact metamorphism can help distinguish an intrusive contact from an unconformity.
- 12.2: Lithostratigraphy
- Lithostratigraphy uses the physical characteristics of the rock as a way to subdivide and classifying them.
- 12.3: Biostratigraphy
- Biostratigraphy uses fossil content to understand spatial and temporal relationships in sedimentary rocks. It is possible because of evolution and the Principle of Faunal Succession for correlation.
- 12.4: Sequence Stratigraphy
- Sequence stratigraphy is a technique used to subdivide strata based on changes in depositional trends.
- 12.5: Seismic Stratigraphy
- Seismic stratigraphy is a technique to classify and describe sedimentary rocks in the subsurface based on seismic reflection data.
Chapter thumbnail shows a relative sea level curve (Page Quinton via Wikimedia Commons; CC BY-SA 4.0).