An estimate of Albian sea-level amplitudes and its implication for the duration of stratigraphic hiatuses

Abstract

Carbonate platform tops are reliable but incomplete recorders of past sea-level fluctuations as they are riddled with hiatuses of various durations. Basinal sections represent a more complete record but fail to register regressive–transgressive events with small to moderate amplitudes. We seek to avoid these problems by combining information on past sea-level fluctuations from coeval platform top, slope and basinal sections. The outcome of this study is a semiquantitative Albian sea-level curve from the southern Tethyan margin in Oman. In subaerial exposure surfaces, the northern Oman margin recorded 4 high-amplitude (∼50 m); 6 intermediate-amplitude (∼30 m); and 26 low-amplitude (∼10 m) regressive–transgressive cycles. Hiatuses that cap the platform top depositional sequences might account for between 30% to 70% of the cycle duration. The resulting platform top depositional sequences have frequencies in the order of 230±20 kyr; i.e. they are in the time range of orbital eccentricity cycles. It appears that at least some of these Albian regressive–transgressive cycles were rapid and punctuated, as opposed to sinus-shaped Milankovitchian sea-level oscillations.