Tafoni development in the Bahamas

Abstract

Tafoni are cuspate pseudokarst weathering features with sloping sediment covered floors, and overhangs and projections, occurring in many rock types. Tafoni appear to be polygenetic. Tafoni have been confusingly defined in many ways: variations in size, rock type, and formation mechanisms. This study addresses tafoni in Quaternary eolian carbonates of the Bahamas to help better define the term. Both large (meters) and small (decimeters) tafoni were studied and comparisons were made between tafoni occurring in Pleistocene and Holocene aged rock units. The differentiation between the main cave types on these islands: tafoni, flank margin caves, and sea caves, is important as all three cave types form in the same area, but flank margin and sea caves can be used as paleo-sea level indicators, while tafoni cannot. Small tafoni were measured and studied from cliff faces and various cultural locations and show a growth rate of 0.022 m3/year; and may amalgamate to form larger tafoni, which grew at faster rate of 0.65 m3/year as a result of that amalgamation. Petrographic analysis was done to help identify tafoni-forming mechanisms; results revealed no evaporites present, removing crystal wedging as a formation mechanism in this environment, while other data indicated wind erosion as the primary mechanism.