According to Flora of North America, different Prunus can have inflorescences of "racemes, corymbs, umbellate fascicles, 2-flowered fascicles, or solitary". However P. caroliniana is a raceme.
At least from the parts I can see clearly, there are only racemes in the pics. The First pic show many individual racemes together. Each one originating from a different bud on last year's wood. In other words, the clump is many inflorescences, not a single one.
