Final answer:
Large, angular, and poorly sorted sediment accumulations are characteristic of glacial deposits, where the movement of ice transports and deposits a wide range of sediment sizes, resulting in an unsorted mix known as glacial till.
Step-by-step explanation:
Large accumulations of unlithified, very poorly sorted, very angular and loose sediment are likely to have been deposited by a glacier. During glacial movement, a wide variety of material is picked up, ranging from fine sediments to large boulders, resulting in a very poorly sorted depositional characteristic. This is unlike the typically well-sorted layers that we would see in environments such as rivers, lakes, or deserts, where the energy of the transporting medium (water or wind) is often more consistent and can separate particles by size more effectively.
Additionally, angular and loose sediments suggest a recent deposit from a process lacking the energy to round off the edges of particles, which is indicative of glacial deposits. Glaciers transport sediment of variable grain sizes including conglomerate, breccia, sandstone, and shale, and drop them as unsorted debris when they melt, creating features like moraines. These sediments are known as glacial till and are noted for their lack of sorting due to the indiscriminate transport and deposition by ice.