Page 78 - Carbonate Facies in Geologic History

Slope, Buildup, Shelf and Shoal Environments 65

SMF-5 Bioclastic grainstone-packstone; floatstone (Embry and Klovan, 1971) if clasts are
of gravel size with finer matrix supporting fabric (Plates I, IV)
This is a common reef flank facies composed mainly of organic debris from organ-
isms inhabiting reef top and flanks. Geopetal fillings and umbrella effects from
infIltered finer sediment are common.
SMF-6 Reef rudstone (Embry and Klovan, 1971)
Coarse gravel of biogenic pieces derived from reef top or reef flank organisms with
no matrix material. The facies occurs commonly within organic buildups formed in
zones of high wave energy.

Organic Buildup Environments (Facies Belt 5)

(Plates IV, V, XVII, XVIII, XX, XXIV-XXVI)
SMF-7 Boundstone (Dunham, 1962), in situ organic growth. Three subtypes proposed by
Embry and Klovan are useful: (a) Massive upright and robust forms constitute
Framestone, (b) encrusting lamellar mats enclosing and constructing cavities and
encrusting micrite layers are termed Bindstone, and (c) when delicate, complex,
frond-like forms are abundant in a fine matrix, the sediment may be interpreted as
trapped by growth of the organisms and the term Bamestone is applied. (Commonly
the micrite is clotted or vaguely pelleted.)

Shelf Facies-Open Circulation (Facies Belts 2 and 7)

SMF-8 Whole fossils wackestone (Flugel, 1972) (Plates V, XVII B)
This is defined by sessile organisms rooted in micrite which contains only a few
scattered bioclasts. The sediment is formed in quiet water below normal wave base
and contains preserved infauna and epifauna.
SMF-9 Bioclastic wackestone (Dunham, 1962) or bioclastic micrite (Flugel, 1972) (Plate VI)
Almost invariably the sediment contains fragments of diverse organisms jumbled
and homogenized through burrowing. It is formed in shallow neritic water of open
circulation at or just below wave base. Bioclasts may be micritized.
SMF-I0 Coated and worn bioclasts in micrite; packstone-wackestone (Fltigel, 1972)
(Plates XV A, XXIIIA) ~
This sediment shows textural inversion and formed in swales in proximity to shoals.
Dominant particles are of high energy environment and have moved down local
slopes to be deposited in quiet water.

Shoal Environment in Agitated Water (Facies Belt 6)

SMF-ll Coated bioclasts in sparite, grainstones (Flugel, 1972). Bioclasts may be micrizited
(Plate VII)
This sediment formed in areas of constant wave action, at or above wave base so
that lime mud is removed.
SMF-12 Coquina, bioclastic grainstone or rudstone, shell hash (Fltigel, 1972) (Plate VIII)
Sediment formed in an environment of constant wave or current action with mud
removed by winnowing. Concentrations of special types of organic debris may be
significant; e.g., dasycladacean grainstones accumulate in very shallow water. En-
crinites are a special microfacies of SMF-12, requiring winnowing but less strong
water movement for their formation. This type of concentration is a common slope
and shelf edge sediment.