Aguathuna Quarry, Port Aux Port Peninsula

Newfoundland, 7/28/03 Day 5

A shot of the different layers of limestone visible here.

About the Quarry

* A scenic stop; an old quarry beside the ocean. Finally we are seeing some sun on one of our first stops in Newfoundland!

* The rock in this quarry is composed of limestone. Limestone is a sedimentary marine rock that can form in both deep and shallow water, depending on the method of deposition. Economically, we use limestone to make lime, which in turn makes concrete. The limestone from this particular quarry was used to make steel, then shipped to Sydney, Nova Scotia, to smelt iron.

The group posing in front of an uplifted section.

Up-close view of one of the 3 layers of limestone.

How Was This Deposited?

* If the limestone was deposited in shallow water, by carbonates from coral reefs, algae, and organisms secreting CaCO3, one would more readily observe preserved mud cracks in the limestone. In that case, the mud literally baked in the sun, and fossils may be present as well. Deep water deposition, on the other hand, would yield no visible mud cracks. This type of deposition, via deep direct deposits of CaCO3, yields very fine layers and crossbedding, due to little wave action deep under the surface of the water.

* There are three limestone units here from distincly different time periods in geologic history. The three different layers are separated by unconformities, or areas where there is missing rock that was either eroded away or never deposited.

Todd explains the different methods of sediment deposition to our group.


We wanted to determine the location of the three types of limestone and the type of unconformity we observed.

The layer of limestone we most closely observed was the Mississippian layer. The type of unconformity we observed is an erosional unconformity. In an erosional unconformity, there is actual sediment missing between distinct layers of deposition. In the topmost layer, the Mississipian, there are lumpy, modeled dolomites which is evidence of erosion. Additionally, in the contact between the Mississippian layer and the Middle Ordivician layer we were able to see where there has been dissolution of material.

We found some fossils in the Mississippian layer, as well as visible mud cracks, which leads us to believe that this layer was deposited in shallow water.

Table represents the 3 different layers of limestone found here, separated by distinct unconformities.

click on some pictures for a larger view!