Page 113 - Carbonate Sedimentology and Sequence Stratigraphy

104 WOLFGANG SCHLAGER

record shows its optimal differentiation in the shoal-water tigraphy; they require high stratigraphic resolution in time
deposits. as well as reliable correlation around the globe and across
The notion that eustasy is the principal control of the sedi- facies boundaries. These conditions are less frequently met
ment record was quickly challenged by tectonicists (Pitman, than is generally assumed. Consequently, eustatic control of
1978; Watts et al., 1982; Cloetingh, 1988) and the debate con- sequences is more often postulated than demonstrated.
tinues to this date (Miall, 1997; Watts, 2001). The issue is The question of eustasy notwithstanding, sequence stra-
of critical importance for global correlation but it is some- tigraphy is a powerful and practically useful concept for
what beyond the sedimentologic scope of this book. The analysing the sediment record. With regard to carbonates,
balance between eustasy and regional tectonics in sequence the sedimentologic principles outlined in this chapter in-
stratigraphy is not a central issue in this context because the dicate that apriori sequences shouldbe viewedas the re-
sediment record at any given location does not distinguish sult of the interplay of relative sea level movements (i.e.
between eustatic and regional tectonic sea-level change. eustasy plus regional tectonics) and sediment supply. The
Two serious tests for eustasy are (1) to globally stack next chapters will show that sediment supply in carbonates
sea-level records and demonstrate the (near)-synchrony of is strongly controlled by the ocean environment. Thus, the
events and (2) to tie records of relative sea-level changes to factor “climate” in Vail’s (1987) list of controls gains added
a globally operating cause such as the perturbations of the importance in carbonate systems.
Earth’s orbit. Both techniques make high demands on stra-