1. Carbonate Platforms

2. RECAP: Carbonate Ramps
Consistent shallow gradient from shoreline to basin (some may be distally steepened), somewhat analogous to siliciclastic shelf
Highest Energy
Lowest Energy

3. Carbonate Platforms
Low-gradient to flat, shallow, broad top with very steep slope
May have platform-edge barrier (reef or shoals)

4. Where is the energy maximum?
Quiet-water lagoon
Fore-reef energy max
Beach energy max
Platform-edge energy max
Frictional energy loss

5. Platform margin facies: Great Bahama Bank
Platform interior
Platform Margin Shoals
Slope and Basin

6. Grainstone margin
Packstone/wackestone interior
Localized ooid grainstone shoals
Skeletal grainstone margin

7. Platform-margin shoals of ooid or skeletal grainstone
Spillover sediment transport in windward direction

8. Planar cross-bedded shoal facies over lagoonal facies

9. Platform Interior Facies
Protected peloidal packstone/wackestone
Open platform peloidal grainstone

10. Characteristic meter-scale cyclicity in platform interior
Shallowing-upwards from subtidal to supratidal
Upper Triassic, Italy

11. Cycles may be allocyclic, driven by rising base level and creation of accommodation space for sediment accumulation
Typical carbonate accumulate rates are very high (> base level rise), so rapidly fill accommodation space and shallow upward

12. Exposure (karst) surface (Carboniferous, Nevada)
Primary relief on surface mantled and infilled by subsequent deposition

13. Cycles may also be autocyclic (properties inherent to the carbonate factory)
High shallow subtidal sedimentation rates = carbonate factory tends to aggrade rapidly to sea level
Carbonate production slows as sediments near sea level

14. Cycles are strongly asymmetrical – thin to absent retrogradational facies, thick progradational facies
May require “lag time” where carbonate sedimentation is slow or absent during early part of base level rise