Geology Reference
In-Depth Information
Fig. 21.22
Base-level curve
, depositional sequence ('strati-
graphic sequence'), systems tracts, and sequence stratigraphic
surfaces defi ned in relation to base-level curve (Modifi ed from
Catuneanu
2006
; Catuneanu et al.
2009
) . Abbreviations:
(
a
), accommodation;
C.C
*
, correlative conformity
sensu
Posamentier
and Allen
1999
;
C.C.
**
,
sensu
Hunt and Tucker
1992
;
MFS
maxi-
mum fl ooding surface,
MRS
maximum regressive surface, SB
sequence boundary,
LST
lowstand systems tract,
TST
transgres-
sive systems tract,
HST
highstand systems tract,
FSST
falling
stage systems tract
21.7
Ancient Examples of Carbonate
Tidalites
margin succession, however, lowstand peritidal
deposits may form during lowstand slow base-level rise
consisting of siliciclastics, evaporites or mixed carbonate-
siliciclastic peritidal deposits (see the Middle Cambrian
tidalites in Sect.
21.7.2
and the Mississippian St. Louis
Formation in Sect.
21.7.4
).
In mature passive margins, peritidal deposits may
constitute the bulk of the transgressive and highstand
packages (see the Middle Cambrian and Middle
Triassic tidalites in Sects.
21.7.2
and
21.7.5.2
).
Platform sequences in proximal areas of a basin may
consist almost exclusively of tidal fl at deposits as in
the Lower Triassic Sorkh Shale Formation (see
Sect.
21.7.5.1
). Sequences in the distal areas of a basin,
on the other hand, consist dominantly of subtidal facies
with tidal fl at facies occurring in the upper part of the
highstand systems tracts (see the Lower Triassic Elika
Formation in Sect.
21.7.5.1
). Absence of peritidal
deposits in the transgressive tracts may be the result of
rapid base level rise. In foreland basin successions,
tidal fl at deposits commonly comprise the upper part
of the highstand systems tract (see the Miocene tidalites
in Sect.
21.7.6
); rapid subsidence in response to over-
thrust loading may prevent tidal fl at deposition in the
transgressive systems tract.
Numerous examples of ancient carbonate tidal facies,
practically comparable to their modern counterparts,
have been reported from the Precambrian and
Phanerozoic successions (e.g. Ginsburg
1975
; James
1984
; Hardie and Shinn
1986
; Tucker and Wright
1990
; Demicco and Hardie
1994
; Flügel
2010
) .
Ancient carbonate tidalites were deposited on huge
carbonate platforms that developed along the Atlantic
type passive margins and in smaller platforms associ-
ated with failed rifts, intracratonic, foreland, back-arc/
fore-arc and pull-apart basins (Read
1985
; Grotzinger
1989
; Demicco and Hardie
1994
) . The thickest and
most extensive tidal deposits, however, were laid down
during Proterozoic through Late Mesozoic times on
the vast carbonate platforms that developed along the
passive (Atlantic type) continental margins, such as the
Iapetus (proto-Atlantic), Paleo-Tethys and Neo-Tethys
ocean margins and associated intracratonic basins.
Proterozoic carbonate tidalites consist of micro-
bialites (both thrombolites and stromatolites), ooids,
intraclasts and micritic carbonates refl ecting carbon-
ate production by chemical and microbial processes.
