The grains of the parabolic dunes?

Question

My text book says that parabolic dunes consist of consolidated limestone grains, but I wondered if they have sand grains too, so I googled this issue and found that they consist of sands, but I am still perplexed, do parabolic dunes have both sand and consolidated limestone grains or they only contain one type of grains? And do they form exactly as other types of dunes (barchan dunes for example)?

Answer 1

Every active dune is just an unlithified deposit of sand-sized grains whose shape is influenced primarily by wind. The grains could technically be made from any mineral, but in most environments quartz is the most common due to its resistance to chemical weathering. Carbonate minerals (particularly calcite) can also form dunes, mostly in coastal settings. Because parabolic dunes usually require some kind of confining vegetation to form, these are quite common in coastal settings where such vegetation can grow, and where the sand is also more likely to be composed of carbonate minerals (especially in tropical regions like the bahamas). Barchan dunes are a similar shape to parabolic dunes, but don't require any vegetation. The similarity between the dune types comes from the fact they both require wind in a single direction.