Page 155 - Carbonate Sedimentology and Sequence Stratigraphy

146 WOLFGANG SCHLAGER

time

elevation cycle complete base cut-out
cycle w.

time

elevation top cut-out top + base cut-out

cycle w.
cycle w.

time

elevation drowning succession (no cycle)

Fig. 7.49.— Cartoons of the sea-level records on very shallow carbonate platforms. The interplay of eustasy, subsidence and sediment
supply produces various kinds of truncated cycles where part of sea-level history is lost in hiatuses. Blue – sea level, red – hiatuses.
Based on Soreghan and Dickinson (1994), Strasser et al. (1999), Tipper (2000).

sessile benthos such as corals (Figs 2.7,7.42). Grain size as Sea-level signals are particularly important in sequence
principal parameter for estimating depth or distance from stratigraphy. Fig. 7.49 summarizes the record one can ex-
shore is less straightforward in carbonates than in siliciclas- pect on flat-topped platforms. The interaction of eustasy,
tics because carbonate grains vary enormously in density subsidence and sediment supply creates a record that is re-
and shape; moreover, their abundance varies because of lo- plete with hiatuses. Usually, only a fraction of the total sea-
calized production. level fluctuation is recorded in the sediment accumulations
The art in facies ranking lies in the choice of parame- (see Soreghan and Dickinson, 1994; Hillgärtner and Strasser,
ters and in the right balance between lumping and splitting. 2003, for detailed analysis). If longer sea-level waves are su-
Descriptions based on oversplit categories drown in mean- perimposed on the short oscillations, the platforms are likely
ingless flicker; descriptions based on broadly lumped cate- to miss large parts of the record (Fig. 5.5).
gories lose useful information.