Governor’s Beach in the southern coast of Cyprus exhibits a nice exposure of interbedded chalk and chert.
Chalk is soft, porous, and fine-grained marine limestone composed of calcareous tests of various microorganisms.
Chert is dense and hard sedimentary rock, consisting mostly microcrystalline quartz. These rocks may frequently occur together. Chert is either nodular or forms layers (bedded chert).
Siliceous material forming chert layers is thought to represent siliceous material deposited on the seafloor and consisting of siliceous tests of radiolarians and diatoms which upon burial formed chert.
White chalk and gray chert.
Chert layers stand out because they are much harder than soft chalk layers.
Closeup of chert.
An example of boudinage — chert layer seems to be stretched, it is not anymore continuous.
Chert between slightly brecciated chalk. Sometimes chert that occurs in chalk is named flint. This term does not have a precise definition but it is often reserved for pure and very hard chert examples. Hence, I would hesitate to name that way the examples shown above (and in the middle of this boudin) but this dark gray chert probably qualifies. So, let’s say it is flint.
A closeup of the same flint boudin.
Here again the color of chert varies. I guess it shows the degree of purity. Pale gray chert is probably impure — contains chalk.
Boudinaged bedded chert and chalk.