1. Marginal-Marine Environments
Deltas, Beach and Barrier Island systems,

2. Marginal Marine Transitional Where land meets the sea
Dominated by rivers (fluvial), wave, and tidal processes.
High-energy – waves and currents
Quiet water – lagoonal, and estuarine

3. Deltas – Deltaic system
Alluvial Delta
Subaerial, subaqueous
Sediment in a standing body of water

4. Ancient Delta Deposits
Found in all ages of stratigraphic sequences
Important petroleum and natural gas deposits, coal, and other mineral resources, uranium is one.
Excellent reservoir rocks, cap rocks and traps in this sequence of rocks, stratigraphic traps

5. Modern deltas Table 9.1 Largest delta plain area = Ganges –Bramaputra
Large water discharge = G-P, Irrawaddy, Mississippi

6. Classification of Deltas

7. Delta Classification 2
Figure 9.3

8. Cross-Section of a Delta
progradation

9. Delta formation

10. Cross-section
Gilbert-type deltas, in your book, Figure 9.4

11. Figure 9.12
Components of a Delta

12. Sediment Characteristics of Deltas
Deltaic plain – subaerial component
Subaqueous Deltaic plaine
Delta front
prodelta

13. Closer view of the cross-section

14. Flow and Discharge Jet – discharge of sediment
Homopycnal flow – equal density water of river entering basin of equal density water, rapid mixing and abrupt deposition of sediment.
Hyperpycnal flow – river water higher density than basin water, flows beneath the basin water, vertically oriented plane-jet flow, forms turbidites on gentle slope of delta.
Hypopycnal flow – river water is less dense than the basin water, river flow into marine or saline lake flow on top of basin as a horizontal plane-jet,

15. Bird-foot Delta

16. History of the Mississippi Delta

17. River-Dominated Delta

18. Wave-dominated Delta

19. Tidal-dominated Delta

20. Fan Delta
Figure 9.11

21. Delta Cycles Transgression of sea
Progradation of delta seaward – construction phase
Coarsening-upward sequence
Fine prodelta muds overlain by delta front silt and sand
Distributary-mouth sands on top of these
Marsh and fluvial deposits
Transgression of sea
Destruction phase

22. River – Dominated Strata

23. Wave-dominated delta Strata

24. Tide-dominated delta strata

25. Ancient Delta system - Mississippian
What tectonic event would these deltas be associated with of the Appalachian Mountains?

26. What do you know of the sea?
Ocean currents?
Rotation?
Hurricanes rotate in what direction?
What about tides?
How many low tides per day?
Spring tide?
Neap tide?

27. Surface Currents

28. Spring Tide and Neap Tide

29. Beach and Barrier Island Systems
Beach is the dominant marginal marine deposit
What is the dominant Wentworth’s clast size found on the beach?

30. Depositional Settings
Tidal ranges
Microtidal = 0 – 2 m tidal range, barrier islands
Mesotidal = 2 – 4 m tidal range
Macrotidal = > 4 m tidal range

31. Beach to Barrier Island
Single Beach – attached to the mainland
Strand Plain – broad beach-ridge system, multiple parallel beach ridges and parallel swales, lack well-developed lagoons or marshes
Chenier Plain – sandy ridges elongated along the coast and separated by coastal mudflat
Barrier Island – separated wholly or partly form mainland by a lagoon or marsh

32. Beach
Littoral zone

33. Breakers

34. Longshore Current

35. Rip Current

36. Prograding Beach
Figure 9.25

37. Barrier Islands and Lagoon

38. Barrier Island
Figure 9.23

39. Characteristics Beach deposits Backshore Shoreface deposits
Fine to medium Sand
Heavy-mineral laminae
Backshore
Eolian sand deposits
Storm-wave deposits
Shoreface deposits
Upper shoreface – bidirectional cross-bedding sets, Skolithos burrows,
Middle shoreface – fine to medium sand, shell material, landward and seaward dipping cross-beds, Skolithos and ophiomorpha
Lower shoreface – fine to very fine sand, intercalated layers of silt and mud, small scale cross-stratification, horizontal laminations, hummocky cross-stratification

40. Deposits Back-barrier
Washover deposits – sandy deposits in the mud-rich lagoon
Tidal-channel deposits – sand and lag deposits, fluvial marine deposit, cross-bedding
Tidal delta deposits – sandy deposits, parabolic shape in cross-section
Tidal Flat deposits – sand lenses and mud deposit
Lagoonal – fine grained muds, organic rich muds
Marsh – sandy to silts to muds, peat deposits, bioturbated a lot.

41. Barrier Islands
Figure 9.26

42. Galveston Island

43. Delaware Island

44. Barrier Island Sequence

45. Back-Barrier
Figure 9.27

46. Pennsylvanian Lagoon

47. Barrier Island and Lagoon - Estuary

48. Estuary