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tary successions, is now commonly used for the sedi-
mentary record of cyclic processes.
Not included in the present section are rhythmic
limestone-marl successions that are discussed in Sect.
16.6 dealing with sediments formed in mixed carbon-
ate-siliciclastic settings.
and ocean volume have been advocated to explain cor-
responding cyclic patterns in climate, sea level, geo-
chemical variables and sedimentary cycles. Many
records of cyclic changes have frequencies that fit well
with those of orbital parameters, and hence are likely
causally related to them.
The Earth's orbit varies in a cyclic fashion in sev-
eral ways. The axis about which the Earth rotates pre-
cesses with a fundamental period of about 26,000 years
and modes between ca. 19,000 and 23,000 years (pre-
cession). It undergoes change in axis inclination (obliq-
uity) in an oscillary manner, generating a cycle of about
41,000 years duration. The orbit of the Earth around
the Sun changes from an almost circular to an almost
elliptical (eccentricity) orbit in two cycles, one at a fre-
quency of about 100,000 years, and the other 400,000
years. These variations in Earth's orbital behavior pro-
duce periodic variations in insolation and climate, called
Milankovitch cycles
with periodicities ranging between
about 20,000 and more than 400,000 years.
The correlation of the Pleistocene deep-sea and
coral-reef record with Milankovitch climatic rhythms
(Hays et al. 1976; Berger 1984; Imbrie 1985) has re-
sulted in a widespread acceptance of the Milankovitch
theory for Pleistocene cycles and also for pre-Pleis-
tocene cyclic sediments. Milankovitch climatic rhythms
are recorded in lake sediments and evaporitic deposits,
in shallow-marine carbonates as well as in hemipelagic
and pelagic sediments.
Orbital forcing
and resulting sea-level fluctuations
are regarded by many authors as the major controls on
carbonate platform cycles. Individual shallowing-up
(sometimes deepening-up) cycles are interpreted as the
result of fifth-order and higher-order sea-level oscilla-
tions. Groups of fifth-order cycles form fourth-order
sedimentary cycles. Third-order cycles in shallow-ma-
rine carbonates have been defined by systematic thick-
ening and thinning of individual cycles over several
hundred meters of profiles.
Important studies on cyclic carbonates using the
Milankovitch model include Fischer (1964), Gold-
hammer et al. (1990, 1991) and Satterley (1996a and
1996b). Problems with the application of the orbital
forcing theory to carbonate cycles were discussed by
Algeo and Wilkinson (1988), Drummond and Wilkin-
son (1993), Satterley (1996b) and Schlager (2002).
16.1.1.1 Cyclic Carbonates: Some Basics
Cyclic sedimentation produces vertical successions of
sedimentary strata characterized by specific patterns.
Based on the mechanisms that generate cyclic depos-
its, two types of cyclic successions can be distinguished:
•
Autocycles
controlled by processes that take place
within the basin itself, e.g. tides or storms. Autocyclic
successions show limited stratigraphic continuity.
•
Allocycles
caused mainly by variations external to
the depositional basin, e.g. sea-level fluctuations, cli-
matic changes or tectonics. Allocyclic successions may
extend over long distances.
Autocycles:
Oscillations generated within the car-
bonate system are used in the
Ginsburg model
, that ex-
plains the common shoaling-upward cycles of carbon-
ate platforms capped by fine-grained tidal flat deposits
(Ginsburg 1971; Hardie and Shinn 1986). The model
assumes continuous, steady basinal subsidence coupled
with carbonate sediment supply rates that are self-regu-
lated by the extent of the progradation. High sediment
production in shallow lagoons leads to seaward pro-
gradation of tidal flat belts. This in turn reduces car-
bonate production and eventually ceases progradation.
Extensive supratidal flats with nearly zero production
lie adjacent to a narrow lagoon. The next cycle starts
with an abrupt transgression and flooding of the tidal
flats when subsidence has sufficiently lowered the
beach ridges on the seaward side of the flats.
Autocyclicity, related to changing sedimentation
during tidal flat progradation, is favored by Hardie
(1986), Pratt and James (1986), Bosellini and Hardie
(1988), Cloyd et al. (1990), Anderson and Goodwin
(1990), Strasser (1991) and Satterley (1996).
Allocycles
. Interpretations of cyclic carbonates re-
lying on allocyclicity assume the existence of high-fre-
quency, and low-amplitude, fourth- and fifth-order sea-
level fluctuations that are often explained by changes
in the Earth's orbital parameters (Goldhammer et al.
1987; Strasser 1988; Koerschner and Read 1989;
Goldhammer et al. 1990; Read et al. 1991).
Orders of stratigraphic cycles.
Cycles
are hierar-
chically classified by the duration of sea-level changes
whereby rates of eustatic changes and amplitudes re-
flect the generating processes (glacio-eustasy or tec-
tono-eustasy). Typical high-frequency, meter-scale
cycles including fifth- and fourth-order cycles with
durations of a few ten thousand years (for fifth-order)
Orbital forcing and Milankovitch cycles
. Insolation
variations affecting the Earth's climate, glacial volume
