Figure 6. Dating an unconformity at its narrowest lacuna: Middle Miocene Unconformity (green sequence boundary) in Sarawak (about 15.5 ma). This is accomplished through a Wheeler diagram (time vs. distance). Note that the lacuna associated with the unconformity includes both hiatus (non-deposition) and the erosional vacuity (due to erosion). Modified from Mansor et al. (1999).