356
Chapter 7 Sequences, Minor Cycles, and Event Stratigraphy
major factors in the establishment of a greenhouse
state of the Earth. The en1arged ocean surface with its
10w albedo was ab1e to absorb more solar energy than
the reduced water surface during times of sea-1eve1
10wstand. The c1irnate became warmer and wetter with
reduced temperature gradients between the poles and
the equator. Further consequences of this deve10pment
are discussed in Sect. 5.6.
Simultaneous1y, the overall terrigenous sediment supp1y into the oceans was reduced (Mackenzie 1990).
After the last 1st order sea-1eve1 highstand, decreasing ocean spreading 1ed to a 10ng-term, slow sea-1eve1
fall which has lasted into the present time. As a consequence, uppermost Cretaceous and Cenozoic marine
sedimentation became restricted to the continenta1 rnargins and deep ocean basins.
Whether or not and in which way long-tenn continental
enchroachment (Ist order) and transgression-regression cyeies (2nd order) have influenced the evolution and distribution of Iife in the sea and on the continents is an open question. Many authors postulate special "bio-events", ineluding
the punctuated evolution of species, dispersal events, and
mass extinctions to have controlled the distribution, survival,
and recovery of life (e.g. Fischer 1982; Sepkoski 1989;
Kauffinan and Walliser 1990: Walliser 1995). Ifthere was
some environmental control, changes in temperature and
chemistry ofthe atmosphere and ocean basins probably had
more influence than merely the physical processes of transgression and regression. Some of the bio-events have been
ascribed to rapid changes in the depositional environment,
such as black shale events.
The famous "Kellwasser crisis" in the upper Devonian
(Frasnian-Famennian, for example, is characterized by a
widespread black shale horizon and mass extinction of pelagic marine organisms in tropical regions (e.g. Buggisch
1991). The sudden deterioration in Iiving conditions occurred during a 10ng-tenn trend towards a cooler climate.
Furthennore, the bio-event was associated with the narrowing of the Paleotethys Ocean.
G1acial intervals during the Pleistocene period caused not
only the migration of plants and animals from high into
lower latitude regions, but also led to the extinction ofvarious families and species. It appears, however, that most of
the bio-events in the Phanerozoic cannot be explained by one
single mechanism.
7.8.3 Transgression-Regression Cycles
(2nd Order)
The time period of continenta1 encroachment cyc1es
approximate1y corresponds to the 1ife times of major
sedimentary basins, such as passive continenta1 margin
basins or passive margins evo1ving into foreland basins
(cf. Sects. 8.5 and 12.6.3). The basin-forming proFig. 7.35. Hierarchy of stratigraphie cyc1es re1ated to
sea-1eve1change. (overview). The figure shows the
principa1 features, superposition and periods of cycesses are re1ated to mantle processes which operate
irregu1ar1y with changing ve10cities. The evolution of
such basins may be comprised of severa1 tectonically
controlled phases, for examp1e two or three phases of
extension (passive margin settings) or the transition
from an extensiona1 to a compressiona1 regime (foreland basin). As a result, the subsidence rates gradually
change with time, and the subsidence-time curves
show transitions from concave to convex-upward
forms (Fig. 7.35; Vai1 et al. 1991) generating eustatic
rises and falls in sea level. Although these tectonic
processes operate on a regional sca1e, they can produce
major global transgressive-regressive facies cyc1es.
Second-order cyc1es ("Sloss" sequences) typically last
ten to severa1 tens ofMa and are superposed on the 1st
order continenta1 encroachment cyc1es. They rnay be
superimposed in turn by cyc1es of higher orders.
Second order cyc1es affect wide are'lS ~f continenta1
she1ves, epicontinenta1 seas and other basins as well as
continenta110w1ands by flooding (coasta1 on1ap) and
emergence (regression). The shore1ines rnigrate 1andward and seaward over 10ng distances (on the order of
50 to 200 km; see also, e.g., Sheridan 1987).
7.8.4 Sequence Cycles (3rd Order)
The common, often described sequence cyc1es of intermediate frequency (0.5 or 1 to 5 Ma; Fig. 7.35) are
regarded by rnany authors as the basic stratigraphie
cyc1e in earth history. This type of sequence has been
observed worldwide from the Proterozoic to the Present. Its time period can be approximate1y reso1ved by
biostratigraphy. Still unso1ved problems with these
cyc1es inc1ude their origin and corre1ation from continent to continent. To create the 1arge amp1itudes of
sea-1eve1 change responsib1e for part of these cyc1es,
either fast operating. geodynarnic processes, such as
magrnatism and diapirism, rnass transfer from the continents to the oceans, significant isostatic response of
the ernst to 10ading, or very slow bui1dup and melting
of continenta1 ice are required. Bui1dup and release of
stress between rapid1y moving continental and oceanic
p1ates has been brought forward as a possib1e tectonic
mechanism (C10ething 1986; Dickinson et al. 1994) to
exp1ain 3rd-order tectono-eustasy.
The signature of third-order cyc1es and their systems tracts have been discussed in some detail in the
previous sections.
c1es, and indicates the main causes of cyc1icity. (After P. Vai1, in Emery and Myers 1996, modified and
supp1emented)
Chapter 7 Sequences, Minor Cycles, and Event Stratigraphy
major factors in the establishment of a greenhouse
state of the Earth. The en1arged ocean surface with its
10w albedo was ab1e to absorb more solar energy than
the reduced water surface during times of sea-1eve1
10wstand. The c1irnate became warmer and wetter with
reduced temperature gradients between the poles and
the equator. Further consequences of this deve10pment
are discussed in Sect. 5.6.
Simultaneous1y, the overall terrigenous sediment supp1y into the oceans was reduced (Mackenzie 1990).
After the last 1st order sea-1eve1 highstand, decreasing ocean spreading 1ed to a 10ng-term, slow sea-1eve1
fall which has lasted into the present time. As a consequence, uppermost Cretaceous and Cenozoic marine
sedimentation became restricted to the continenta1 rnargins and deep ocean basins.
Whether or not and in which way long-tenn continental
enchroachment (Ist order) and transgression-regression cyeies (2nd order) have influenced the evolution and distribution of Iife in the sea and on the continents is an open question. Many authors postulate special "bio-events", ineluding
the punctuated evolution of species, dispersal events, and
mass extinctions to have controlled the distribution, survival,
and recovery of life (e.g. Fischer 1982; Sepkoski 1989;
Kauffinan and Walliser 1990: Walliser 1995). Ifthere was
some environmental control, changes in temperature and
chemistry ofthe atmosphere and ocean basins probably had
more influence than merely the physical processes of transgression and regression. Some of the bio-events have been
ascribed to rapid changes in the depositional environment,
such as black shale events.
The famous "Kellwasser crisis" in the upper Devonian
(Frasnian-Famennian, for example, is characterized by a
widespread black shale horizon and mass extinction of pelagic marine organisms in tropical regions (e.g. Buggisch
1991). The sudden deterioration in Iiving conditions occurred during a 10ng-tenn trend towards a cooler climate.
Furthennore, the bio-event was associated with the narrowing of the Paleotethys Ocean.
G1acial intervals during the Pleistocene period caused not
only the migration of plants and animals from high into
lower latitude regions, but also led to the extinction ofvarious families and species. It appears, however, that most of
the bio-events in the Phanerozoic cannot be explained by one
single mechanism.
7.8.3 Transgression-Regression Cycles
(2nd Order)
The time period of continenta1 encroachment cyc1es
approximate1y corresponds to the 1ife times of major
sedimentary basins, such as passive continenta1 margin
basins or passive margins evo1ving into foreland basins
(cf. Sects. 8.5 and 12.6.3). The basin-forming proFig. 7.35. Hierarchy of stratigraphie cyc1es re1ated to
sea-1eve1change. (overview). The figure shows the
principa1 features, superposition and periods of cycesses are re1ated to mantle processes which operate
irregu1ar1y with changing ve10cities. The evolution of
such basins may be comprised of severa1 tectonically
controlled phases, for examp1e two or three phases of
extension (passive margin settings) or the transition
from an extensiona1 to a compressiona1 regime (foreland basin). As a result, the subsidence rates gradually
change with time, and the subsidence-time curves
show transitions from concave to convex-upward
forms (Fig. 7.35; Vai1 et al. 1991) generating eustatic
rises and falls in sea level. Although these tectonic
processes operate on a regional sca1e, they can produce
major global transgressive-regressive facies cyc1es.
Second-order cyc1es ("Sloss" sequences) typically last
ten to severa1 tens ofMa and are superposed on the 1st
order continenta1 encroachment cyc1es. They rnay be
superimposed in turn by cyc1es of higher orders.
Second order cyc1es affect wide are'lS ~f continenta1
she1ves, epicontinenta1 seas and other basins as well as
continenta110w1ands by flooding (coasta1 on1ap) and
emergence (regression). The shore1ines rnigrate 1andward and seaward over 10ng distances (on the order of
50 to 200 km; see also, e.g., Sheridan 1987).
7.8.4 Sequence Cycles (3rd Order)
The common, often described sequence cyc1es of intermediate frequency (0.5 or 1 to 5 Ma; Fig. 7.35) are
regarded by rnany authors as the basic stratigraphie
cyc1e in earth history. This type of sequence has been
observed worldwide from the Proterozoic to the Present. Its time period can be approximate1y reso1ved by
biostratigraphy. Still unso1ved problems with these
cyc1es inc1ude their origin and corre1ation from continent to continent. To create the 1arge amp1itudes of
sea-1eve1 change responsib1e for part of these cyc1es,
either fast operating. geodynarnic processes, such as
magrnatism and diapirism, rnass transfer from the continents to the oceans, significant isostatic response of
the ernst to 10ading, or very slow bui1dup and melting
of continenta1 ice are required. Bui1dup and release of
stress between rapid1y moving continental and oceanic
p1ates has been brought forward as a possib1e tectonic
mechanism (C10ething 1986; Dickinson et al. 1994) to
exp1ain 3rd-order tectono-eustasy.
The signature of third-order cyc1es and their systems tracts have been discussed in some detail in the
previous sections.
c1es, and indicates the main causes of cyc1icity. (After P. Vai1, in Emery and Myers 1996, modified and
supp1emented)