Page 160 - Carbonate Facies in Geologic History

Diagenesis in Middle Paleozoic Buildups 147

discussion of it and conjectures concerning its origin will be found in Chapter V. The original
cavity is probably basically of slump origin and indicates an early porosity and permeability
of micritic core rock.
3. Evidence of subaerial exposure occurs on the edges and in places within some bank
interiors. Klovan describes an island rim of tidal flat fenestral laminites on the eastward side
of Redwater complex. Petrographic study of the bank margin and bank interior rocks shows
some cementation as well as solution under conditions of meteoric water circulation.
4. The dominance of stromatoporoids in the Middle Paleozoic offers improved chances
for porosity and permeability in such carbonate strata. That the original loose network of
pillars and laminae in stromatoporoids may have been aragonite is inferred by comparing
their preservation with that of rugose and tabulate corals. Stromatoporoids are more suscep-
tible to leaching and alteration to coarse calcite and to dolomitization than are corals.