Page 46 - Carbonate Facies in Geologic History

Stratigraphic Sequences, Geometry, and Facies of Carbonate Shelf Margins and Basins 33

o •
,,~ .. 0 0 0 •
'i57'
• xc Bioclastic shools •
~O.
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:'" ": " ~'l~S~ GULF
~o () 0 0 0 0 Q

Fig. II-I O. Bathymetry and surface sediments of Persian Gulf after Houboult (1957), showing
facies change in lime sands in progressively deeper water out from the isolated gentle positive
area of the Qatar peninsula. The slope northeast ofT Qatar is extremely slight e / 2 m per km)
but a facies progression exists which reflects the systematic though very gradual deepening

Montana high; the Albian Cretaceous beds of central Texas (Glen Rose Formation and
Fredericksburg Group, of central Texas, Fig. Il-9); a modern analog may be found in the
facies developed around the northern end of the Qatar Peninsula in the Persian Gulf (Fig. Il-
10).

Stratigraphic Sequences, Geometry, and Facies
of Carbonate Shelf Margins and Basins

The basic carbonate facies model divides logically into two parts based on geome-
try and stratigraphic relations, degree of slope, and tectonic position: (1) Shelf
margin complexes at the edges of major basins or along margins of major offshore
banks within such basins, areas of considerable subsidence; and (2) Shelf strata
laid down across flat cratonic areas in clear epeiric seas, areas of moderate subsi-
dence.