Presented By: Niah Venable, Geosciences, Western Michigan University Kalamazoo, MI

1. Excerpts from:The Application of Key Stratigraphic Concepts plus Geological Insights from the Sequence Stratigraphy “Revolution” to Engineering Geology in Michigan Presented By: Niah Venable, Geosciences, Western Michigan University Kalamazoo, MI

2. Geological “First Principles” Relevant to Sequence Stratigraphy(adapted from Posamentier and Allen, 1999) • Fluid and sediment gravity flows tend to move from high to low elevations, i.e., water flows downhill, tending to follow topographic or bathymetric lows. • Flow velocity is directly proportional to slope magnitude. • Sediment grain size and flux is directly proportional to stream power, i.e., flow velocity and discharge.

3. Geological “First Principles” Relevant to Sequence Stratigraphy(adapted from Posamentier and Allen, 1999) • Fine-grained sediment (e.g., silt and clay) is generally transported in suspension to accumulate in low current strength areas through suspension settling. • Coarser-grained sediment (e.g., sand sized and greater) is generally transported as bed load or, less commonly, in suspension. • As environmental energy decreases, coarse-grained sediments are deposited first.

4. Geological “First Principles” Relevant to Sequence Stratigraphy(adapted from Posamentier and Allen, 1999) • In typical alluvial, marine shelf, or deep-water sedimentary systems ”equilibrium” (the most efficient use of system energy) is expressed as a graded or steady-state profile. • In near-shore marine (or lacustrine) systems sea (lake) level is the base level of accumulation.

5. Geological “First Principles” Relevant to Sequence Stratigraphy(adapted from Posamentier and Allen, 1999) • Walther's Law: the same sedimentary succession that is present vertically was present horizontally unless there was a break (unconformity) in sedimentation. From Shaw, 1964

6. First Principles and ControlsSequence Stratigraphy • Relative Sea Level • Eustacy (global s.l.) • Tectonic Subsidence/Uplift • Climate/Sediment Supply • Sediment compaction Coe, et al., 2003

7. First Principles and ControlsSequence Stratigraphy • Eustatic Sea Level Cycles • 1st Order Cycles • 100’s my • 100’s of meters • 2nd Order Cycles • 10’s my • 100’s of meters • 3rd Order Cycles • 1-10 my • 10’s of meters • Etc. Falling Rising From: Nichols, 1999

8. Accommodation “Space” available for sedimentaccumulation First Principles and ControlsSequence Stratigraphy • Accommodation Space, akey first principle Posamentier, Jervey, and Vail; 1988

9. First Principles and ControlsSequence Stratigraphy • Accommodation is defined by: • The Equilibrium Profile • The theoretical, steady state (no gain or loss of sediment) depositional surface in any environment • Controlled by various factors, including • Hydrodynamic gradient of the system • Substrate and sediment load characteristics and

10. Base Level Points coinciding with theoretical equilibrium profile along an actual depositional profile Erosion occurs above and deposition occurs below base level First Principles and ControlsSequence Stratigraphy Posamentier and Allen, 1999

11. First Principles and ControlsSequence Stratigraphy • Base Level • Marine (lacustrine) base level is simplified as the sea (or lake) surface • Actually much more complicated Coe, et al., 2003

12. First Principles and ControlsSequence Stratigraphy • The thickness and type of sedimentary deposit formed in any sedimentary environment is controlled by: • Sediment supply • Base level and accommodation space for that sediment Coe, et al., 2003

13. RELATIVE SEA LEVEL First Principles and ControlsSequence Stratigraphy • Rate of relative sea level change, Accommodation (A) and stratal geometry (SG) dA/dt  dSG/dt Aaccommodation SGstratal geometry Ttime Posamentier, Jervey, and Vail; 1988

14. Analysis of cyclic patterns in sedimentary successions, developed through time, in response to: Used to explain and predict stratal geometry. variations in sediment supply and space available for sediment accumulation Sequence Stratigraphy Vail, 1987

15. Major Sequence Stratigraphic and Chronostratigraphic Surfaces Kendall, USC Sequence Stratigraphy www site

16. Sequence StratigraphyFirst Principles and Controls • Implication of high resolution sequence concepts to aquifer/hydrocarbon reservoir correlation Van Wagoner, et al., 1990 Retrogradational System Progradational System

17. Key Sequence Stratigraphy References • Sea Level Changes: an Integrated Approach; edited by, C.K. Wilgus, et al., SEPM Spec. Pub. No. 42, 1988. • Siliciclastic Sequence Stratigraphy – Concepts and Applications; Posamentier, H.W. and Allen, G.P., SEPM Concepts in Sedimentology, No. 7, 1999 • The Sedimentary Record of Sea-Level Change; ed. Angela Coe, The Open University/ Cambridge University Press, 2003