Page 85 - Carbonate Facies in Geologic History

72 Outline of Carbonate Petrography

5. Bulbous-cabbage heads. Rounded shape insures strong architecture but also in turbid
water prevents sediment from accumulating on the surface; generally found in quiet water
either deeper (below wave base) or in shallow protected back reef areas: Bulbous stroma-
toporoids, Diploria, M ontastrea.
6. Basket-shaped; presents double surface area in moderate to slight current: Sponges,
Favosites.
7. Elongate, erect, tall, and slender. Rapid upward growth as a preventative to swamping by
strong sedimentation: Rudists, some deep water modern corals, Dendrophyllia.
8. Flexible dendroid, segmented forms. Found in areas of moderate currents and wavy
motion. The fenestrate form prevents sediment accumulation and presents large surface
area. Associated with bulbous "cabbage head" forms: Crinoids, alcyonarian sea fans,
gorgonians, fenestrate bryozoans, sphinctozoan sponges.
9. Rigid dendroid and fasciculate. Found in protected areas in all parts of reef areas. Com-
mon in quieter water and on muddy bottoms except for some forms which, although
brittle, may be fast-growing: Acropora cervicornis, Stachyoides (Devonian), Thecosmilia,
Oculina (Tertiary-Recent), Montlivaltia (Mesozoic), some sponges, disphyllids, Syringo-
pora (Late Paleozoic).

Table III-I. Environments for major groups of calcareous marine algae (from Ginsburg et aI.,
1971)
Algal type and growth habit Salinity, temperature Less than Maximum
average depth depth

Coralline Red Algae:
Massive, and dendroid, Normal marine. <25 m. Very 200-250m
Rigid and articulated. Open marine shelf and bays shallow, range
Nodules on seafloor. Reef variable
builder and reeffringe
dweller

Codiacean:
Encrusting or with leaves Warm, shallow marine <10m 100m
erect and articulated. Only water of slightly variable
calcified cortex preserved. salinity. Do not require
strong circulation
Das ycladacean
Erect, articulated segments. Warm, shallow, variable 3-5m 12-15 m
Radiating pores which salinity, up to 50-60%. just below low
produce calcispheres tide level
(fruiting cases).
Chara oogonia
Calcareous fruiting cases. Fresh water, but may wash Very shallow < 10m
Large calcispheres into coastal marine and
brackish water
Blue green-cyanophytes
Irregular tiny tubular Highly variable. Intertidal 45m?
bundles forming mats, Fresh to hypersaline
massive erect domes,
dendroid forms, tufts
depending on the water
energy