Your journey will bring you to Goose Creek State Park in eastern North Carolina located along the Pamlico River. The Pamlico River, the estuary to the Tar River, empties into the Pamlico Sound. The Pamlico Sound is part of a large, interconnected network of lagoon estuaries. Seven sounds making up the whole: the Albemarle, Currituck, Croatan, Pamlico, Bogue, Core, and Roanoke Sounds. As a whole it is the second largest estuary in the United States; Chesapeake Bay is the largest.
Goose Creek State Park is located on the north side of the Pamlico River between Washignton and Bath NC.
Rapid Marine Transgression
This Earth Cache illustrates a fundamental and important geologic process. At Ground Zero you will find an excellent example of inland coastal marsh undergoing rapid marine transgression. This area has been recognized as a National Natural Landmark
A marine transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, resulting in flooding and erosion. Sediments shift from terrestrial to marine, which reflects an ocean advance.
The opposite of transgression is regression, in which the sea level falls relative to the land and exposes former sea bottom.
What Causes Transgressions?
Transgressions can be caused either by the land sinking or the ocean basins filling with water (or decreasing in capacity). Transgressions and regressions may be caused by tectonic events such as:
--Orogenies - large structural deformations of the Earth's lithosphere (uppermost mantle and crust ) due to the engagement of tectonic plates.
--Isostatic adjustments - following removal of ice or sediment load.
--Severe Climate Change
One example of transgression occurred during the Cretaceous period when spreading sea floor created a relatively shallow Atlantic basin at
the expense of deeper Pacific basin. This reduced the world's ocean basin capacity and caused a rise in sea level worldwide. As a result of this sea level rise, the oceans transgressed completely across the central portion of North America and created the Western Interior Seaway from the Gulf of Mexico to the Arctic Ocean.
Sedimentary changes are indicative of transgressions and regressions and are often easily identified, because of the unique conditions required to deposit each type of sediment. For instance, coarse-grained sediments like sand are usually deposited near shore in high-energy environments; fine-grained sediments however, such as silt and carbonate muds, are deposited farther offshore, in deep, low-energy waters.
Thus, a transgression reveals itself in the sedimentary column when there is a change from near shore sediment to offshore sediment. A regression will feature the opposite pattern, with offshore sediments changing to near shore sediment.
Let’s see what you’ve discovered--
To claim credit for this cache send an email to our profile address with your answers to the following:
1- By your observation and using the above information as a guideline, what is the most likely cause of rapid marine transgression at this site?
2. Describe the sedimentation in this area?
3. Can you see any remnants of the much earlier sediments? If earlier sediments exist, send a description of what you saw.
4. What year was this area dedicated as a National Natural Landmark?
5. What is the elevation at Ground Zero?
6. Optional—post a photo of yourself or group at GZ.
Do not post a pic of the marker.
Do not post answers in your log or we’ll nix it.
This Earth Cache was approved by Ranger John Fullwood. Park manager and head ranger at Goose Creek State Park.
Bikes are NOT permitted on trails.