Page 107 - Carbonate Platforms Facies, Sequences, and Evolution

19
&
rimmed
sea-level.
(Anisian).
20),
shelf
here
and
also control the sediment
sea-level curve, particular
in the Lower Muschelkalk
Fig.
Fig. 19. Depositional systems
termed
(determined by eustasy and/or
18
by relative changes of sea-level
tracts for a carbonate ramps.
accommodation potential. During
tracts and lithostratigraphical units
Fig. 18. Depositional systems tracts
for a carbonate ramp. The rationale
specific time-intervals of the relative
tectonics; see also Fig. 25) and these
is that stratal patterns are controlled
illustrates
-
Depositional
the
<
,;
0
i
- - .,-
[]
AGE I
muds±
The Mid-Triassic strata of the Catalan Basin can
(compare Hubbard et at., 1985 and Vail et al., 1984,
be divided into two depositional sequences (Figs 4,
systems
(1988) has described the systems tracts of a carbonate
for example and the review of Hubbard, 1988). Sarg
sequence
back ramp
1
�-
evaporites _-_ -_
Maximum flooding su rface
(which
DEPOSITIONAL SYSTEMS
TRANSGRESSIVE SYSTEMS
Depositional
Buntsandstein
Buntsandstein
HIGHSTAND SY STEMS TRACT
mid-ramp
CARBONATE RAMP
-
--� sands +muds
1
the lowstand type.
DEPOSITIONAL SY STEMS TR ACTS -
TRACT -
TRACTS IN
includes
(ANISIAN, MIDDLE
and
1
1
Middle Triassic carbonate ramp systems, Spain
below
sequence
the
! �-------------------------------<
SYSTEMS
the
2
TRIASSIC )
Lower
(which
TRACTS
uppermost
porite unit is a separate depositional
part
THE LOWER MUSCHELKALK
Muschelkalk)
includes
of
NE
I LITHOSTRATIGRAPHIC UNITS
sequence,
carbonate ramp types). The lowstand systems tract may be represented by a paleokarstic surface and calcareous soils,
lutite-carbonate-eva­
and the climate. SB is the sequence boundary, ts is the transgressive surface, mfs is the maximum flooding surface and sl is
the lower sequence are shown as the facies of a ramp with a barrier shoreline and a back-ramp lagoon, whereas in the upper
sequence. TST strata typically consist of an onlapping, retrogradational package, which may consist of parasequences (each
of which will generally be a shallowing-upward cycle). The overlying HST strata will form an aggradational-progradational
(SMW, not appropriate here). On a carbonate ramp, deposits of the TST and HST generally form the major part of the
sabkha evaporites, or fluvial-lacustrine facies, depending on the magnitude of the relative sea-level fall, hinterland relief
depositional systems tracts are established: lowstand (LST), transgressive (TST), highstand (HST) and shelf-margin wedge
the
sequence the TST and HST are shown as the facies of a ramp with a strandplain (see Tucker & Wright, 1990, for a review of
and
package, which again may consist of a parasequence set of shallowing-upward cycles. In this figure, the TST and HST of
of
97
Middle Muschelkalk and Upper Muschelkalk). The
the