Page 119 - Petrology of Sedimentary Rocks

ek: Epikratonic” shelves, basins and geosynclines (parageosynclines of Stille),
developed on the interior of the kraton, away from its margins (auto- and
zeugogeosyncl ines of Kay). Rift Valleys (KAK) may represent aulacogens.
Wider basins result from “Saucer Tectonics.”
u: Uplifts may or may not be present adjoining the epikratonic basins.

All of the above features are completely gradational and overlapping, but represent
recognizable end-points like the colors of a spectrum.

Later in the history of the continent, the mobile belt is thrusted, folded, squashed,
intruded, uplifted, and accreted onto the continent as a relatively rigidified outer
frame, which thererafter does not normally undergo further severe horizontal deforma-
tion. Thus the original kraton (hedreocraton of Kay) is enlarged to become a new
kraton, or neokraton.” Any mobile belts added since Precambian are considered as
neokratons. Further geosynclines, basins, sheets, and troughs may then develop atop of
and flanking the neokraton, as classified below:

eg-m

c-OLD KRATON -
c RIGID IFIED OLD ORTHOGEOSYNCLINE
-NE~KRATON

eg: Epigeosynclinal* sheets 9 basins, troughs, and geosynclines; can be divided as
f 01 lows:

regions
eg-f: flanking linear . . of thick deposition (paraliageosynclines of Kay--
. .
more exactly, “geomonocl i nes” like Atlantic and Gulf Coast Tertiary,
U.S.A.); or more equant basins or sheets (e.g., Sydney Basin, Australia).
These often occur on the passive edges of continents, where continent and
ocean basin are on the same tectonic plate. (KOA).

eg-m: medial regions (including local intermontane basins, fault-block basins or
taphrogeosynclines of Kay, and deeply subsiding troughs or epieugeosyn-
clines of Kay; e.g., Newark series, or Nevada graben-fills, etc.) These may
be the result of tensional movement between plates, or the initial rifting
when a continental plate starts to split. (KAK).

eg-c: centripetal regions, sediment moving generally from the deformed belt back
onto the stable kraton (e.g., Great Plains Tertiary, USA; Cretaceous and
later, western Queensland, Australia). Dilution from the old kratonic area
common,

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