292
Chapter 7 Sequences, Minor Cycles, and Event Stratigraphy
7.8.3 Transgression-Regression Cycles (2nd Order)
7.8.4 Sequence Cycles (3rd Order)
7.8.5 Parasequence Cycles and Milankovitch Cycles
7.8.6 Summary (Hierarchy and Causes ofCycles)
7.9 Cyclo- andEvent Stratigraphy
359
7.9.1 Introduction
7.9.2 The Astronomical Time Scale
(Milankovitch Cycles)
7.9.3 Rhythmic (Cyclic) Bedding
Cyclic vs. Discyclic Bedding
Limestone-Marl Altemations
Black Shale-Carbonate Rhythms (Redox
Cycles)
Rhythmic Bedding in Siliceous Sediments
Periodicities and Causes ofCyclic Bedding
7.9.4 Peritidal-Lagoonal and Subtidal Carbonate
Cycles
7.9.5 Platform-Basin Correlation ofHighFrequency Carbonate Cycles
Basin-To-Basin Correlation of Cyclic Bedding
Shoreface-To-Basin Correlation in
Epicontinental Sea
Cycle Correlation on Carbonate Platforms
Platform-To-Basin Correlation
Long-Distance Oceanic Seamount-ToShelf Correlation
7.9.6 Discyclic Bedding and Other Depositional
Events
Examples of Discyclic Bedding
Other Depositional Events
Recurrence Intervals ofEvent Beds
7.9.7 Non-Depositional and Erosional Events
(Skeletal Horizons, Lags etc.)
General Aspects
.
Continental Non-Depositional Events
Marine Lag Sediments and Shell
Concentrations
Biological and Ecological Events
7.9.8 Minor Cycles, Event Beds and Lags in 3rd
Order Sequence Cycles
7.9.9 Summary (Cyclo- and Event Stratigraphy)
7.10 General Discussion (Sequence and Event
Stratigraphy)
381
7.l0.l Principal Achievements in Sequence,
Cyclo- and Event Stratigraphy
7.l0.2 Uncertainties, Problems, and Open
Questions
7.1 General Characteristics of
Cyclic Sediments
7.1.1 Individual Beds, Rhythmic Bedding, and
Sedimentary Cycles
Many sedimentary sections exhibit a kind of
rhythmicity due to regularly altemating beds traceable over long distances, or arepetition of larger
units which are referred to as sedimentary sequences
or cycles. Rhythmic and cyclic sequences occur
worldwide on various scales in presumably every
environmental and stratigraphie system.
They have attracted the interest of earth scientists for a long
time (e.g., Duff et al. 1967; Einseie et al. 1991;
Schwarzacher 1993), but the origin of some of them is still
poorly known. Cyclic phenomena in particular are becoming increasingly important in dating and correlation ofsedimentary successions. Further references are listed in Sect.
7.9.
In a first overview we proceed from small units, observed in field exposures, to large sequences which
are studied in basin cross sections and compiled from
the seetions of several basin fills. Later, the modem
concepts and different orders of sequence stratigraphy are discussed.
The basic sedimentological unit described in sequence analysis is the laterally ·traceable, relatively
uniform bed Bed thicknesses vary from a few centimeters to several meters, but are commonly in the
order of some 5 to 40 cm. The lateral extent of individual beds ranges from a few meters to > 1000 km.
Beds are separated from each other by thinner or
thicker, usually weaker intercalations, the so-called
interbeds, of differing composition or structure (see
e.g. Collinson and Thompson 1982). The bed and
overlying interbed form·a bedding couplet. When the
interbed becomes very thin, as found in bed-dominated alternations, it may essentially represent a bedding plane. Bedsets or bundles represent several bedding couplets, separated by thicker interbeds (Fig.
7.1g). Bedsets without interbeds are formed by amalgamation of event layers (see below). Depositional
rhythms and cycles are defined as follows (Fig. 7.1):
- Rhythmic bedding or rhythmic sequences consist oftwo altemating bed types (succession AB, AB,
etc), i.e., beds and interbeds, or a succession of bedding couplets. This group is subdivided into two different categories (cf. Sect. 7.9.3):
(1) Bedding variations result from abrupt changes
in sedimentation due to depositional events or episodes at random to quasi-periodic time intervals
(forming stochastic, episodic, or discyc/ic bedding;
Fig. 7.1a and b). The most prominent examples of
this group are tempestites and turbidites, flood deposits on alluvial plains, and layers of repeated volcanic ashfalls intercalated into a differing background sedimentation.
(2) Bedding variations are caused by repeated
slow, gradual changes in deposition. This type may
also be called cyc/ic bedding, or when strictly periodic, periodic bedding (Fig. 7.1c and d). Typical examples are little lithified chalk-marl sequences and
stronger lithified pelagic limestone-marl alternations.
Chapter 7 Sequences, Minor Cycles, and Event Stratigraphy
7.8.3 Transgression-Regression Cycles (2nd Order)
7.8.4 Sequence Cycles (3rd Order)
7.8.5 Parasequence Cycles and Milankovitch Cycles
7.8.6 Summary (Hierarchy and Causes ofCycles)
7.9 Cyclo- andEvent Stratigraphy
359
7.9.1 Introduction
7.9.2 The Astronomical Time Scale
(Milankovitch Cycles)
7.9.3 Rhythmic (Cyclic) Bedding
Cyclic vs. Discyclic Bedding
Limestone-Marl Altemations
Black Shale-Carbonate Rhythms (Redox
Cycles)
Rhythmic Bedding in Siliceous Sediments
Periodicities and Causes ofCyclic Bedding
7.9.4 Peritidal-Lagoonal and Subtidal Carbonate
Cycles
7.9.5 Platform-Basin Correlation ofHighFrequency Carbonate Cycles
Basin-To-Basin Correlation of Cyclic Bedding
Shoreface-To-Basin Correlation in
Epicontinental Sea
Cycle Correlation on Carbonate Platforms
Platform-To-Basin Correlation
Long-Distance Oceanic Seamount-ToShelf Correlation
7.9.6 Discyclic Bedding and Other Depositional
Events
Examples of Discyclic Bedding
Other Depositional Events
Recurrence Intervals ofEvent Beds
7.9.7 Non-Depositional and Erosional Events
(Skeletal Horizons, Lags etc.)
General Aspects
.
Continental Non-Depositional Events
Marine Lag Sediments and Shell
Concentrations
Biological and Ecological Events
7.9.8 Minor Cycles, Event Beds and Lags in 3rd
Order Sequence Cycles
7.9.9 Summary (Cyclo- and Event Stratigraphy)
7.10 General Discussion (Sequence and Event
Stratigraphy)
381
7.l0.l Principal Achievements in Sequence,
Cyclo- and Event Stratigraphy
7.l0.2 Uncertainties, Problems, and Open
Questions
7.1 General Characteristics of
Cyclic Sediments
7.1.1 Individual Beds, Rhythmic Bedding, and
Sedimentary Cycles
Many sedimentary sections exhibit a kind of
rhythmicity due to regularly altemating beds traceable over long distances, or arepetition of larger
units which are referred to as sedimentary sequences
or cycles. Rhythmic and cyclic sequences occur
worldwide on various scales in presumably every
environmental and stratigraphie system.
They have attracted the interest of earth scientists for a long
time (e.g., Duff et al. 1967; Einseie et al. 1991;
Schwarzacher 1993), but the origin of some of them is still
poorly known. Cyclic phenomena in particular are becoming increasingly important in dating and correlation ofsedimentary successions. Further references are listed in Sect.
7.9.
In a first overview we proceed from small units, observed in field exposures, to large sequences which
are studied in basin cross sections and compiled from
the seetions of several basin fills. Later, the modem
concepts and different orders of sequence stratigraphy are discussed.
The basic sedimentological unit described in sequence analysis is the laterally ·traceable, relatively
uniform bed Bed thicknesses vary from a few centimeters to several meters, but are commonly in the
order of some 5 to 40 cm. The lateral extent of individual beds ranges from a few meters to > 1000 km.
Beds are separated from each other by thinner or
thicker, usually weaker intercalations, the so-called
interbeds, of differing composition or structure (see
e.g. Collinson and Thompson 1982). The bed and
overlying interbed form·a bedding couplet. When the
interbed becomes very thin, as found in bed-dominated alternations, it may essentially represent a bedding plane. Bedsets or bundles represent several bedding couplets, separated by thicker interbeds (Fig.
7.1g). Bedsets without interbeds are formed by amalgamation of event layers (see below). Depositional
rhythms and cycles are defined as follows (Fig. 7.1):
- Rhythmic bedding or rhythmic sequences consist oftwo altemating bed types (succession AB, AB,
etc), i.e., beds and interbeds, or a succession of bedding couplets. This group is subdivided into two different categories (cf. Sect. 7.9.3):
(1) Bedding variations result from abrupt changes
in sedimentation due to depositional events or episodes at random to quasi-periodic time intervals
(forming stochastic, episodic, or discyc/ic bedding;
Fig. 7.1a and b). The most prominent examples of
this group are tempestites and turbidites, flood deposits on alluvial plains, and layers of repeated volcanic ashfalls intercalated into a differing background sedimentation.
(2) Bedding variations are caused by repeated
slow, gradual changes in deposition. This type may
also be called cyc/ic bedding, or when strictly periodic, periodic bedding (Fig. 7.1c and d). Typical examples are little lithified chalk-marl sequences and
stronger lithified pelagic limestone-marl alternations.