Mudstone, shale, and limestone are examples of sedimentary rock likely to contain fossils. As the layers of sediment build up on top of one another, they create a physical timeline. The oldest layers, ...
The Upper Jurassic-aged Haynesville Shale formation is a dark organic-rich, brittle (conducive to hydraulic fracing) mudstone-shale that lies between the Bossier and Cotton Valley Lime intervals.