2010年3月16日

Carbonate ramp depositional environments


Carbonate ramp depositional environments

The first concept of a carbonate ramp was given by Ahr (1973) as an contrast to steep-sloped and reefrimmed shelves. Ramps can be understood as a type of carbonate platforms. Carbonate platforms are succesions formed in shallow water, including rimmed shelves, ramps and isolated buildups. The slope-gradient of ramps are smaller than 1° and have no slope break. Read (1982, 1985) devided ramps into homoclinal and distally steepened. The distinction of there two types remains problematic unless slope or slope apron deposits are present in the record. Most classifications (Markello and Read, 1981; Aigner, 1984; Calvet and Tucker, 1988; Buxton and Pedley, 1989 and Somerville and Strogen,1992) use the fair weather wave base (FWWB) and the storm wave base (SWB), to subdivide ramp depositional systems. On this basis Wright (1986) and Burchette et al. (1990) define four sedimentary subdivisions.

Burchette TP and Wright VP. 1992. Carbonate ramp depositional systems. Sedimentary geology, 79(1-4): 3-57