Transgressive Coastlines Flashcards
A > S means sea will ….. so the sediment will ….
Transgress, the sediment will be eroded inland.
A < S means sea will ….. so the sediment will …
Receed, so the sediment will prodgrade outwards into the sea.
Name the succession of environments going out to sea during the building of a delta
Backshore, foreshore, shoreface, inner shelf, outer shelf
When does sediment get preserved during flooding of the land?
Sediment can only be preserved when A
What does TSE stand for? Discuss TSE.
Transgressive Surface Of Erosion, occurs during transgression inland where a surface is eroded. It starts when transgression starts and ended when regression begins.
Evidence of alot of bioturbation is due to what?
Low sedimentation rates, it is not always because there are more organisms present.
In the sedimentary record we see mostly evidence of regression or transgression?
Regression, transgression is rarely preserved.
what happens to a barrier island during transgression?
It will get flooded and eroded away. It will build out if it is regression.
Breaches in barrier islands are caused by what?
Tidal currents, as the tide rises you can get a flow that breaches the barrier island and so can get flood-tidal deltas.
What is the difference between a flood-tidal delta and a delta?
Flood tidal deltas are formed at barrier islands when they breach due to a release in confinement. They do not form in the same way as a normal delta.
Where are estuaries defined in a sedimentary point of view?
Defined by the Inner Limit of Tidal Influences (ILTI)
What does ILTI stand for
Inner Limit of Tidal Influences
Discuss the balance of energy in the estuary process
At the sea end marine processes as dominant, as you go inland they become progressively weaker until they reach 0. At the river end the river is the most dominant process, and as you move further towards the sea it becomes less dominant.
The arbitrary point is where they cross, 50 energy from sea and 50 energy from river.
Low tidal range and exposed coastline gives you a …. dominated estuary
Wave
Tide dominated estuaries have …. tidal range and coast is …. with ….. waves.
High tidal range, coast is sheltered with weaker waves
discuss a river dominated estuary
This is not possible as the river would fill up the valley and create a delta. The river may dominate over a short period of time.
Discuss a tide dominated estuary as much as you can.
Tidal inflow and outflow much stronger, waves are minor and drop off very quickly. Tidal flow speeds up as it funnels into the estuary, once they are into the estuary they drop off. River flows are the opposite to this and pick up once you are in the estuary. The red line on the diagram shows the relative energy which drops when the river is meandering.
Sand bars are present at the mouth, they are elongated parallel to the dominant flow current. Aligned in direction to valley and parallel to valley axis.
In a tide dominated estuary, are the sand bars parallel or perpendicular to the valley axis?
Parallel to valley axis
In a tide dominated estuary, are the sand bars parallel or perpendicular to the valley?
They are aligned in the direction to the valley so are perpendicular.
Why would the flow come in one side of the estuary and go out another? what does this mean for sedimentary structures at either side of the estuary
Because of the way the moon pulls the tide. At one side there will be a unidirectional current creating dunes whilst the other side will have dunes migrating in the other direction.
what happens when saline and river water mix with clay particles present?
The clay particles clump together (flocculate) due to the changing salinity and drop to the seabed as they can’t be carried in suspension
