Geomorphic features have been one of the major tools for sea-level change studies. The present work shows an example of sea-level change study on karst terrain in the tropics. Sea-level notches as well as flank margin caves were identified in the research area and their elevation measured. The time of formation of the sea-level indicators was constrained by lithology study and dating methods such as facies comparison and U-Th dating. Denudation and uplift were also studied for the same purpose.

From this study it can be concluded that sea-level stands within the glacial cycle can cause the formation of flank margin caves and that the position of these sea-level stands can be determined. The research area was estimated to have cumulatively uplifted ∼22 m in the past 125 ka years (∼0.18 mm/yr) while the surface has been denuded some 8 m in the same span of time (∼0.064 mm/yr).

Keywords: karst, karst hydrology, flank margin caves, sea-level change, denudation rate, uplift rate, sea-level notches, bioerosional notches, last interglacial, MIS 5e, mid-Holocene sea-level highstand, reef limestone, Guam