Page 154 - Carbonate Sedimentology and Sequence Stratigraphy

CHAPTER 7: SEQUENCE STRATIGRAPHY OF THE T FACTORY 145

ranked in six categories from open marine to highly re- sensitive in space to small, accidental features and in the
stricted, with two categories added for emergent conditions time domain to short, strong, but accidental events such as
at the landward end. storms, sudden gravitational collapse etc. On very flat plat-
The choice of parameters for recording change in the forms, the degree of restriction and emergence is an attrac-
stratigraphic section is arguably the most critical step in tive choice. Ramps on continental margins may be open ma-
high-resolution sequence stratigraphy. Ideally, the param- rine right to the shoreline. In such settings, wave energy
eters should relate to properties that change gradually or in as a proxy for water depth may be an appropriate choice.
small steps over a wide range. They should be rather in- A third possibility are relative light levels as indicated by

80 -
Fig. 7.48.— Bedding record of an Early-
hst Cretaceous (Aptian) carbonate platform in
RFT
the Apennines, Italy. Profiles were measured
mfs S6
with 2-centimeter resolution, only large pat-
terns are shown. Left: Age and thickness
70 - tst scale in meters. Shaded: Lithologic col-
umn showing facies varying from fully open-
SB marine on the left (facies belt A) to restricted
supratidal on the right (facies F). Sedimen-
hst
tation is interrupted by two types of expo-
mfs S5 TFT sure surfaces: type 1 – supratidal, possibly
60 - tst terrestrial; type 2 – demonstrably terrestrial.
SB Central column shows sequence classifica-
mfs tion. Arrows on the right: shoaling and deep-
S4
ening trends of two different orders. After
tst D’Argenio et al. (1999), modified.
50 - SB RFT
hst
mfs
S3

Aptian 40 - tst TFT

SB

hst

30 - S2
mfs
tst
SB

hst
20 -
mfs S1

tst
10 -
SB

hst RFT

0m -
Super
A B C D E F 12 systems bundles T/RFTs
faciesbelts em tracts
(sequences)