Final answer:
Mature sediments show increasing well sorting and rounding, indicating they have been transported a significant distance from their source of origin.
Step-by-step explanation:
The question pertains to the characteristics of sediment that can indicate how mature it is and the distance from the source where it was deposited. The two blanks in the sentence can be filled with:
(a) well sorted
(b) rounded
Mature sediments that have been transported far from their point of origin tend to be well sorted and rounded. This sorting occurs because as sediments are transported, finer particles are carried farther than coarser ones, leading to stratification of particle sizes. As for rounding, sediments become rounded due to the abrasion and weathering they experience while being transported over long distances. Therefore, increasing sorting and roundness indicate sediments that are mature and have been deposited far from their source.