part marine environment.pptx only marginal marine environmrnts

Marginal marine Environments

1. Marine Environments Marginal-Marine Environments Siliciclastic marine environments

2. Marginal marine depositional environment Deltas Beaches Barrier island system Estuaries

3. Deltas Deltas: D eltas from when velocity drops as the river enters a standing body of water,typically This is the coast as the river flows into the sea .

4. Flocculation Flocculation occurs as fresh water mixes with salt water - e.g where a river flows into the sea -(then called brackish water), and is the process by which tiny particles in suspension like clay and silt (which under normal fresh water conditions would likely never fall out of suspension) coagulate with the salt in the water by chemical reaction and become heavy enough to 'sink' and be deposited

5. Types of Deltas Deltas can be categorise into three main shapes • Arcuate • Birds Foot • Cuspate Arcuate delta : The most common shape of delta. Characteristics: curving shoreline, distinct pattern of drainage and typically more gravely deposits. Ex: the nile delta. Birds foot delta: Fingers of deposition build out into the sea along the distributaries channels giving an appearance like a birds claw. Ex:- mississipi delta . Cuspate delta: It is shaped like a tooth by gentle but regular opposing currents in the water body .

6. Beaches:- Landforms and terminology in coastal regions: • The foreshore. • The backshore. • The berm Beaches Foreshore: The area most influenced by the hi gh and low water marks and breaking waves Bac kshore: Submerged only during the highest tides and severest storms Berm: The high point on the beach;the backshore-foreshore boundary.it change Seasonally.

7. Terminology

8. Movement of sand on the beach: MOVEMRNT PARALEL TO SHORELINE Huge volumes of sand are moved within the surf zone Caused by wave refraction The beach resembles a river of sand

9. Barrier island system Common along passive margins Sand is most common materials Gravel common in glacial terranes Width is<100 to Kms

10. Estuaries Relatively small, partly enclosed coastal embayments are loosely called coastal bays. Two broad types of coastal bays are recognized: ESTUARIES  LAGOONS.

11. Defination : Estuary as”the seaward portion of a drowned valley system receives sediments f rom both fluvial and marine sources. Contains facies influenced by tide , wave and Fluvial process.

12. Physiographic, Hydrologic, and Sediment Characteristics of Estuaries: Seven basic types of modem estuaries are recognized. Fjords: are high-relief estuaries with a U-shaped valley profile formed by drowning of glacially eroded valleys during Holocene sea-level rise. Coastal-plain estuaries: are low-relief estuaries, funnel- shaped in plan view, that are open to the sea. Low-relief estuaries: that are L-shaped in plan view and that have lower courses parallel to the coast are bar-built estuaries. Deltaic estuaries: occur on delta fronts as ephemeral distributaries. Flask-shaped, high-relief rias backed by a low- relief plain created by tectonic activ , ity are called compound

13. Principal types of estuaries based on physiographic characteristics.

14. wave-Dominated Estuary: In wave-dominated estuary, tidal influence is small, and the mouth of the estuary experiences high wave energy. Sediments tend to move alongshore and onshore into the mouth of the estuary. This barrier prevents most of the wave energy from entering the estuary; thus, only internally generated waves are present behind the barrier. Depending upon tidal range and current velocity,a small number of inlets may be kept open in this barrier

15. In wave-dominated estuary, tidal influence is small, and the mouth of the estuary experiences high wave energy. Sediments tend to move alongshore and onshore into the mouth of the estuary. This barrier prevents most of the wave energy from entering the estuary; thus, only internally generated waves are present behind the barrier. Depending upon tidal range and current velocity,a small number of inlets may be kept open in this barrier Wave-dominated estuary

16. Tide-dominated estuaries occur mainly on macrotidal coasts where tidal-current energy exceeds wave energy at the mouth of the estuary. Elongate sand bars develop parallel to the length of the estuary from sand carried into the estuary from marine sources. These bars tend to dissipate tidal energy. Tide-dominated estuary Examples of tide-dominated estuaries include Cook Inlet, Alaska; Ord River, Australia; Gironde Estuary, France; and the Severn River, United Kingdom.

17. Def: A coastal lagoon is defined as a shallow stretch of seawater--such as a sound, channel, bay, or saltwater lake. Most modern lagoons are formed behind spits. Lagoons commonly extend parallel to the coast, in contrast to estuaries, which are oriented approximately perpendicular to the coast. Lagoons have no significant freshwater runoff. LAGOONAL SYSTEMS