The Formation of Clastic Sedimentary Rocks
What order would you most likely find the three basic types of clastic sedimentary rock when a stream runs into a lake and out to the middle of that lake?
A. Conglomerate, Sandstone, Shale
B. Shale, Sandstone, Conglomerate
C. Sandstone, Shale, Conglomerate
D. Shale, Conglomerate, Sandstone
Answer:
The three basic types of clastic sedimentary rock would likely be found in the order of Conglomerate, Sandstone, and Shale from where a stream enters a lake to the middle of the lake, reflecting the decreasing energy environment and particle size.
Explanation: When a stream carries sediment into a lake, the particles are deposited based on their size due to the reduction in energy of the water. The grain size of the sedimentary rocks and their deposition is influenced by the distance from the shore and the energy of the environment.
Shale forms from silt and clay-sized particles that settle in calm water far from shore. Sandstone is comprised of sand-sized particles which typically settle out in environments with slightly higher energy, closer to the shore than where shale forms. Conglomerate is made of coarser, gravel-sized particles which settle quickly and are often deposited closest to the shoreline or stream entry point where the energy of the water is greatest.
Therefore, the order in which you would find these sedimentary rocks from the point where the stream enters the lake and moving out towards the center would be Conglomerate, followed by Sandstone, and then Shale, which corresponds to option A: Conglomerate, Sandstone, Shale.