372
Chapter 7 Sequences, Minor Cycles, and Event Stratigraphy
Under these conditions, the number ofmissed beats may become very high.
Platform-To-Basin Correlation
A correlation of minor cyeles from platform to basin
appears to be even more difficult than correlation
within platfonn sediments. N evertheless, some authors
have recently tried to establish such a correlation for
peritidal, subtidal, and alternately bedded carbonate
cyeles over distances ofhundreds up to > I 000 km. The
main results of one of these examples are shown in
Figure 7.44 in a simplified way, omitting local stratigraphic tenns and many other details.
In addition to the elementary and small composite
units, 3rd order sequences could be identified which
modify to some extent the character of the smaller cyeles. As a result of the superposition of various frequencies, the "classical" sequence boundaries, SB, and
maximum flooding surfaces, MFS, of pure 3rd or 4th
order sea-Ievel oscillations had to be replaced by sequence boundary zones, SBZ, and maximum flooding
zones, MFZ, as mentioned above (Fig. 7.44b and c).
Each of these zones contains several surfaces which
could be denominated as SB or MFS. During 3rd order
lowstands, the platfonn emerged or only allowed the
fonnation of condensed sections; slopes could be subjected to erosion.
One ofthe first attempts to establish such a correlation was
made in Lower Cretaceous sediments of the Vocontian
Trough and its neighboring platforrn in southeastem France
(Ferry and Monier 1987). In this work, cycle bundling was
mainly used for correlation. Later, this type of study in the
Early Cretaceous (Berriasian) was conducted in both Switzerland and France (Pasquier and Strasser 1997). Another
example deals with the Jurassie (Oxfordian) in the Swiss
Jura, Spain and Norrnandy (Pittet and Strasser 1998). Such
attempts require very accurate stratigraphie resolution based
on various methods discussed in the special articles. In some
cases, the meter- to dekameter-scale peri- and subtidal (about
100 ka) cycles deposited on the platforrns seeIIi in turn to
consist of a number of thinner units representing about 20 ka
periods. The latterprobably correspond to the limestone-marl
couplets (precession cycles) observed on the slope and in the
deeper basins (Fig. 7.44).
If the platforrn emerged only episodically during lowstands (keep-up stage, F ig. 7 .44c), the continuously produced
carbonate was flushed into deeper water to form limestone
beds. During highstands, most of the carbonate production
remained on the platforrn, while in deeper water relatively
thin marly beds accumulated (Fig 7.44d). Thus, the basinal
sediments became thicker during lowstands and transgression
than during highstands.
Long-Distance Oceanic Seamount-To-Shelf
Correlation
Thanks to the Ocean Drilling Program, first extensive
sedimentary records from isolated submerged oceanic
seamounts (guyots) are now available from the western
Pacific (Winterer et al. 1995). During the Middle Cretaceous (Aptian-Albian), the tops of these volcanic
structures (presently at water depths between 1300 and
1500 m) accumulated shallow-water carbonates. The
carbonate caps maintained a depositional environment
elose to sea level for about 20 Ma by sediment buildup
compensating for thermal subsidence (30-50 mlMa),
before carbonate deposition was shut off. These platfonn carbonates (up to 900 m in thickness) were
hardly affected by local syntectonic movements or
terrigenous sediment supply and therefore provide an
excellent re cord of major and minor sea-Ievel changes.
The most important results gained from four
seamounts are the following (Röhl and Ogg 1996):
- The Aptian and Albian cores displayed 12 third-order sequences each. The average thicknesses of the
sequences range from ab out 30 to 60 m and their time
periods from 0.5-1.5 Ma (average ~0.8 Ma). About
one third of the sequence boundaries showed well-cemented exposure surfaces.
- Each sequence could be subdivided into two to five
parasequence sets (mostly 9-12 m thick, time period
around 0.3 Ma) consisting in turn of two to five thinner stratal elements.
- The overall carbonate production allowed an upbuilding of the carbonate caps at rates of 35-65 mlMa
(equal to the subsidence rates). These rates are similar
to those found at other carbonate platforms (Sect. 3.3,
Fig. 3.27). In times of SLF>SUB, the platforms
emerged; with SLF ~ SUB, condensed sections with
algal flats evolved, and with SLF
boundaries exhibit upward deepening facies.
- The sequences identified at the seamounts could be
correlated with well-dated (thicker) Aptian-Albian sequences of Western Europe (England, France, and
northern Spain). With the aid of this correlation (including parasequences) it seems to be possible to improve the calibration of the European biozones, because the exponentially deelining thennal subsidence
of the seamounts renders a relatively precise time contro!.
This and the previous examples demonstrate the considerable progress which has been achieved in
cyclostratigraphy. This method may help to solve some
of the correlation problems associated with the socalled global eustatic sea-level curve after Haq et a!.
(1987).
Chapter 7 Sequences, Minor Cycles, and Event Stratigraphy
Under these conditions, the number ofmissed beats may become very high.
Platform-To-Basin Correlation
A correlation of minor cyeles from platform to basin
appears to be even more difficult than correlation
within platfonn sediments. N evertheless, some authors
have recently tried to establish such a correlation for
peritidal, subtidal, and alternately bedded carbonate
cyeles over distances ofhundreds up to > I 000 km. The
main results of one of these examples are shown in
Figure 7.44 in a simplified way, omitting local stratigraphic tenns and many other details.
In addition to the elementary and small composite
units, 3rd order sequences could be identified which
modify to some extent the character of the smaller cyeles. As a result of the superposition of various frequencies, the "classical" sequence boundaries, SB, and
maximum flooding surfaces, MFS, of pure 3rd or 4th
order sea-Ievel oscillations had to be replaced by sequence boundary zones, SBZ, and maximum flooding
zones, MFZ, as mentioned above (Fig. 7.44b and c).
Each of these zones contains several surfaces which
could be denominated as SB or MFS. During 3rd order
lowstands, the platfonn emerged or only allowed the
fonnation of condensed sections; slopes could be subjected to erosion.
One ofthe first attempts to establish such a correlation was
made in Lower Cretaceous sediments of the Vocontian
Trough and its neighboring platforrn in southeastem France
(Ferry and Monier 1987). In this work, cycle bundling was
mainly used for correlation. Later, this type of study in the
Early Cretaceous (Berriasian) was conducted in both Switzerland and France (Pasquier and Strasser 1997). Another
example deals with the Jurassie (Oxfordian) in the Swiss
Jura, Spain and Norrnandy (Pittet and Strasser 1998). Such
attempts require very accurate stratigraphie resolution based
on various methods discussed in the special articles. In some
cases, the meter- to dekameter-scale peri- and subtidal (about
100 ka) cycles deposited on the platforrns seeIIi in turn to
consist of a number of thinner units representing about 20 ka
periods. The latterprobably correspond to the limestone-marl
couplets (precession cycles) observed on the slope and in the
deeper basins (Fig. 7.44).
If the platforrn emerged only episodically during lowstands (keep-up stage, F ig. 7 .44c), the continuously produced
carbonate was flushed into deeper water to form limestone
beds. During highstands, most of the carbonate production
remained on the platforrn, while in deeper water relatively
thin marly beds accumulated (Fig 7.44d). Thus, the basinal
sediments became thicker during lowstands and transgression
than during highstands.
Long-Distance Oceanic Seamount-To-Shelf
Correlation
Thanks to the Ocean Drilling Program, first extensive
sedimentary records from isolated submerged oceanic
seamounts (guyots) are now available from the western
Pacific (Winterer et al. 1995). During the Middle Cretaceous (Aptian-Albian), the tops of these volcanic
structures (presently at water depths between 1300 and
1500 m) accumulated shallow-water carbonates. The
carbonate caps maintained a depositional environment
elose to sea level for about 20 Ma by sediment buildup
compensating for thermal subsidence (30-50 mlMa),
before carbonate deposition was shut off. These platfonn carbonates (up to 900 m in thickness) were
hardly affected by local syntectonic movements or
terrigenous sediment supply and therefore provide an
excellent re cord of major and minor sea-Ievel changes.
The most important results gained from four
seamounts are the following (Röhl and Ogg 1996):
- The Aptian and Albian cores displayed 12 third-order sequences each. The average thicknesses of the
sequences range from ab out 30 to 60 m and their time
periods from 0.5-1.5 Ma (average ~0.8 Ma). About
one third of the sequence boundaries showed well-cemented exposure surfaces.
- Each sequence could be subdivided into two to five
parasequence sets (mostly 9-12 m thick, time period
around 0.3 Ma) consisting in turn of two to five thinner stratal elements.
- The overall carbonate production allowed an upbuilding of the carbonate caps at rates of 35-65 mlMa
(equal to the subsidence rates). These rates are similar
to those found at other carbonate platforms (Sect. 3.3,
Fig. 3.27). In times of SLF>SUB, the platforms
emerged; with SLF ~ SUB, condensed sections with
algal flats evolved, and with SLF
boundaries exhibit upward deepening facies.
- The sequences identified at the seamounts could be
correlated with well-dated (thicker) Aptian-Albian sequences of Western Europe (England, France, and
northern Spain). With the aid of this correlation (including parasequences) it seems to be possible to improve the calibration of the European biozones, because the exponentially deelining thennal subsidence
of the seamounts renders a relatively precise time contro!.
This and the previous examples demonstrate the considerable progress which has been achieved in
cyclostratigraphy. This method may help to solve some
of the correlation problems associated with the socalled global eustatic sea-level curve after Haq et a!.
(1987).