Page 42 - Carbonate Facies in Geologic History

Basinal Buildups in Areas of Great Regional Subsidence 29

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Fig.II-6. Location map of the Dolomites and their major banks after Bosellini and Rossi
(1974). Hachured lines indicate foreslope strata marking original edge of bank. See also
Fig. VIII-IO. Illustration with permission of Society of Economic Paleontologists and Miner-
alogists

rise occurs, shelf margin barriers cannot easily form. Land is too close and the belt
for maximum carbonate production is too narrow. The tectonic setting for such
narrow facies patterns is defined later in this Chapter, termed a "fringe or halo"
bordering a cratonic edge.

Paleotectonic Settings for Carbonate Facies

Tectonism will, by controlling subsidence, partly influence thickness, facies, and
vertical sequence of the nine facies belts. But climatic, hydrographic, and organic
controls are so strong that the basic pattern will occur in varied megatectonic
provinces. These are outlined below, organized into several major types and fitted
to the outline of Krebs and Mountjoy (1972). The examples are all drawn from the
geologic record. It is difficult to find analogs from Holocene carbonate sedimen-
tary realms because the sedimentary record covering Tertiary and Recent plat-
forms is so young and thin. This problem is reviewed in the summary Chapter.

1. Basinal Buildups in Areas of Great Regional Subsidence
The largest of these features includes major offshore banks. These occur well within geosyn-
clines or pericratonic basins. They contain some of the thickest carbonate sections known, and