Final answer:
During sediment transportation, grains become more rounded, smaller in size, and better sorted the further they are transported from their source. Grain rounding results from abrasion during transport, while prolonged transport results in smaller, well-sorted sediments, indicating a far distance from the source.
Step-by-step explanation:
During transportation of sedimentary grain, three significant changes tend to occur: grain rounding, grain size, and grain sorting.
Initially, as sediment is transported from its source, the grains typically have rough edges and vary in size. However, the longer the sediment is moved by wind, water, or ice, the more its characteristics change. Grain rounding occurs due to the abrasion of the grains against each other and the transport medium. Grains with smooth edges are often an indicator of having traveled a long distance from source. Over time, the grains wear down to become more spherical or rounded; thus, well-rounded grains suggest a prolonged period of transport.
Regarding grain size, smaller grains are usually the result of extended transport since larger particles get broken down into smaller ones over distance. This sorting of grains based on size results in sediment that is well-sorted if transported over long distances. As sediments settle from their transportation medium, larger grains tend to be deposited first with finer grains settling later or further away from the source.
The grain sorting is another aspect affected by transportation—it refers to the uniformity of grain sizes within a sediment deposit. Well-sorted sediment contains grains of about the same size, indicating a far distance from the source rock, while poorly sorted sediment retains a variety of grain sizes, suggesting a short transport distance from the source.