explain the difference between a sea-level transgression and regression.

Brief Explanations:

Sea-level transgression and regression are geological events that describe the movement of the shoreline relative to the land.

1. Transgression: This occurs when the sea level rises relative to the land, causing the shoreline to move inland (submergence). In the stratigraphic record, this is characterized by a "fining-upward" sequence, where deeper-water sediments (like shale or limestone) are deposited on top of shallower-water sediments (like sandstone).
2. Regression: This occurs when the sea level falls relative to the land, causing the shoreline to move seaward (emergence). This can be caused by a drop in global sea levels or tectonic uplift of the land. In the stratigraphic record, this results in a "coarsening-upward" sequence, where shallower-water sediments are deposited on top of deeper-water sediments.

Answer:

A sea-level transgression is a geological event where the sea level rises relative to the land, flooding previously exposed areas and shifting the shoreline landward. Conversely, a sea-level regression is an event where the sea level falls relative to the land, exposing the sea floor and shifting the shoreline seaward.