Development of flute-mark assemblages, 1. Evolution of pairs of defects

Abstract

Experiments using a bed of hardened Plaster of Paris dissolved by a turbulent water stream (practical analogue of natural mud-bed erosion) show that paired defects evolve into compound flute marks which at a critical age become marks indistinguishable from structures developed from single defects. The critical age increases as the relative spacing of the paired defects grows larger but decreases as their alignment approaches the mean flow direction. Growth of the compound marks follows similar laws to single flutes. A natural assemblage of flute marks may be expected during an early stage of development to show a progressive reduction in the number-density of the structures, as a consequence of the merging of marks generated from defects sufficiently closely spaced to have interacted during the time available.