Sequence Stratigraphy

Question
• Group Question: discuss the following
• What is allostratigraphy and what does the name imply?

Sequence Stratigraphy
• What is Sequence Stratigraphy
– Allostratigraphy
• Depositional Sequence
– 3rd order T-R unit
– Bounded by unconformities (basinwide in extent)
• Depositional System
– Systems tracts, parasequence sets, parasequences

Sequence Stratigraphy
• Controls on sequence development
• Accommodation space - relative sea level change
– Eustatic sea level
– Tectonics - uplift and subsidence
– Climate - sediment supply and type

Sequence Stratigraphy
• Historical development
• Physical Stratigraphy - Sequence Stratigraphy
• Grabau 1920’s, Wanless & Weller, Newell, Elias, Moore 1930’s & 40’s
• Sloss 1950’s
• Exxon 1970’s - Peter Vail
• Exxon 1980’s & 90’s - Van Wagoner, Posamentier, Academia

Sequence Stratigraphy
• Seismic Stratigraphy - basin scale
• How do you recognize a sequence?
• Surface recognition - stratal discontinuities
– Onlap, toplap, baselap

Sequence Stratigraphy
• Outcrop scale
• Identify facies
• Vertical stacking
• Lateral change
• parasequences

Parasequences
• What is a parasequence
• Marine flooding surfaces
• Surface recognition
• Vertical facies stacking
• Surface morphology
– Skeletal lag (taphonomy)
– Phosphates
• Correlation

Parasequence Correlation
• Surfaces - Closely spaced localities
• Marker beds
• Stratal patterns = stratigraphic significance
• 3-d geometries

Parasequence Stacking Patterns
• Progradational
• Retrogradational
• Aggredational
• Deposisitonal system - overall pattern

Systems Tracts
• Lowstand
• Progradational
• Not present on the shelf
• Onlap and downlap

Systems Tracts
• Transgressive
• Transgressive surface
• Onlap and toplap
• Retrogradational and aggredational

Systems Tracts
• Highstand
• MFS - MFH
• Downlap and toplap
• progradational

Applications
• High resolution chronostratigraphy
• Vertical and lateral predictions
• Better resolve time and space