1. Introduction to Basin Analysis

2. In the long run, eustatic changes in base level are cyclical Do not produce permanent increases in accommodation for long- term sediment storage Base level is also a function of climate (=energy), but it is unlikely that climate changes will lead to substantial permanent accommodation creation

3. Yet many sedimentary basins have kilometers (or 10s of km) of sediment fill over 10s-100s of Myr How is that much permanent accommodation space created?

4. Subsidence is required for formation of a sedimentary basin and long-term sediment accumulation

5. Physical mechanisms of subsidence: 1. Isostasy Pratt isostasy Topography is a function of lithospheric density Airy isostasy Topography is a function of lithospheric thickness

6. Physical mechanisms of subsidence: 2. Flexure (also called regional isostasy) Earth’s rigid lithosphere acts as an elastic plate. When loaded (by a mountain range, sediment column, other tectonic plate), it flexes.

7. Most (but not all) sedimentary basins occur in areas of active plate tectonics 1.Basins due to extension 2. Basins due to convergence 3. Strike-slip basins

8. Crustal extension leads to rift basins and ultimately to passive margins Subsidence driven by crustal thinning and heat flow changes Primarily isostatic Basins due to extension

9. Rift-drift transition marked by “breakup unconformity” that coincides with the onset of seafloor spreading (heat flow from magma production) Transition to a passive margin

10. Subsidence primarily driven by flexure of underlying plate from weight of overriding plate E.g., forearc basins at continental margins above subduction zones Basins due to convergence

12. Foreland basins are deepest next to the mountain front Marine or terrestrial sediment fill reflects balance between sedimentation rate and subsidence rate (accommodation space)

13. Strike-slip basins Pull apart or fault overstep basins associated with strike-slip fault systems Small size means that heat is lost through walls, leading to rapid fault-controlled subsidence

14. Strike-slip basins often have extremely rapid lateral facies variations May be sediment-starved (marine or lacustrine) in center