Page 128 - Petrology of Sedimentary Rocks

kJ* Basin-wedge, equant depositional region, greatly thickened at
one edge (e.g., so-called Catskill “delta”)

P Prism, small area, often fault-bounded, extremely thick at one
side with rapid thinning (e.g., Newark fault troughs).

9 Geosyncline, long, narrow, thick trough such as a typical miogeo-
syncline

!3* Geosyncline of extreme thickness (thickness like that of typical
eugeosyncline--but no volcanism implied as that comes in an-
other part of the symbol)

I Local patch, small, thin, often superficial or residual or local
valley-fill

In the above, (*) means great thickness. This system is flexible so that
account may be taken of units that may grade from one type of basin in one
area to another type elsewhere--example, sb or sg.

IV. Dominant Depositional Environment

Tercier proposed a sort of super-environmental assemblage, upon which the
following is based. A formation, though made up of rock bodies deposited in
many micro-environments (e.g., tidal flat, estuary, lagoon, beach-dune, etc.)
can be placed in a general mega-environmental assemblage as follows:

C Continental; flood plain, river channel, swamp, etc.

Continental, alluvial fan.
cf
Continental, lacustrine.
cl
Continental dune-sheet (e.g., Saharan erg).
‘d
L Littoral: specifically mainly beach, beach-dune, some shallow marine
“undaf or mrr --basically shoreline deposits in areas not much influenced
by riverine contributions.

P Paral ic: floodplain and delta, coastal swamp and lagoon, estuarine, shallow
marine; heavy influence of alluviation (e.g., Pennsylvanian of Appalachians).
Pd: del taic.

E Evapori tic: inland salt lake or marine evaporitic lagoons.
M Marine, generally shallow and of normal circulation. May be sub-
divided into M undaform of Rich, wave-influenced generally coarser
U’
sediments; M , clinoform or slope deposits, if turbidites M Mf,
ct;
fondoform of kich, below significant stirring by wave action, generally
muds; Mk, dominantly carbonate area with little detrital influx.

B Bathyal to Abyssal, slope and baisn deposits; clinoform and deep-water
deposits; of ten Vurbidi tes” (Bt).

Cg,Mg, etc.--Glacially influenced.

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