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and diagenetic cycles having a cap typified by subaerial
or submarine diagenetic features.
Controls discussed for the generation of repeated
meter-scale subtidal Latemar cycles include autocyclic
processes (vertical accretion, variations in sediment pro-
duction and redistribution), allocyclic processes (epi-
sodic subsidence, short-term eustasy), or a combina-
tion of both. Both auto- and allocyclicity are also dis-
cussed as major controls on the origin of the peritidal
cycles.
Fig. 16.3 shows an ideal Latemar cycle as visual-
ized by Hardie et al. (1986) and Goldhammer et al.
(1990). The Middle Triassic Latemar Limestone in the
Dolomites consists of hundreds of vertically stacked,
meter-scale, platform carbonate cycles. Each cycle
(couplets) is composed of a shallow-marine subtidal
carbonate unit with a thin, centimeter-scale vadose di-
agenetic dolomitic cap. The couplets are interpreted as
the products of repeated episodes of submergence/emer-
gence with durations estimated at about 20,000 years.
The dominant organization of successive couplet thick-
nesses into upward-thinning bundles of five suggested
to Goldhammer et al. (1987) a control by 100,000 years
sea-level oscillations. Spectral analysis gave evidence
of Milankovitch-forced, small amplitude sea-level os-
cillations (Hinnov and Goldhammer 1991). This inter-
pretation has been strongly criticized by Eggenhof et
al. (1999) who found no evidence of a Milankovitch
control on the Latemar cycle.
In terms of Standard Microfacies Types the subma-
rine unit of the Latemar model consists of SMF 16-
N ON - LAMINATED at the base (common in platform inte-
rior environments), overlain by SMF 17 (aggregate-
grain grainstone, common in restricted platform inte-
rior environments), followed by SMF 12 (oncoid rud-
stone, known from different high-energy environments
including back-margin lagoonal areas). The vadose cap
corresponds to SMF 26 (pisoid rudstone, characteriz-
ing subaerial exposure). This sequence of SMF types
reflects notably the trends in the changes of relative
water depths postulated by Goldhammer et al. (1987).
Fig. 16.3. An ideal Middle Triassic 'Latemar cycle' of the
Dolomites consists of an internally differentiated subtidal unit
(1-3) and a thin subaerial exposure cap (4). The base of the
submarine unit is defined by a sharp bedding plane, usually
with a concentration of dolomite clasts derived from the cap
of the underlying couplet. The submarine unit exhibits an
upward coarsening trend in depositional texture, with in-
creased grain-support toward the top. The sequence termi-
nates with gravel-sized oncoids. 1 - Very fine to fine, sand-
sized peloidal, restricted skeletal wackestone to packstone.
2 - Medium to very coarse, sand-sized skeletal grain pack-
stone to grainstone. 3 - Coarse, sand-sized to gravel-sized
oncolitic, lithoclastic grainstone to rudstone. The limestone
member is interpreted as a product of subtidal deposition
within a shallow-marine, back-margin platform lagoon with
normal salinity. The boundary between the subtidal limestone
and the upper vadose dolostone cap (4) is irregular and gra-
dational. The microfacies of the vadose cap is characterized
by pisoid packstones and grainstone with caliche pisoids and
other caliche fabrics. The vadose cap is interpreted as the
product of an extended episode of subaerial exposure lasting
several thousands of years. After Hinnov and Goldhammer
(1991).
Basics: Cyclic carbonates
Overviews
De Boer, P.L., Smith, D.G. (eds., 1994): Orbital forcing and
cyclic sequences. - International Association of Sedimen-
tologists, Special Publications, 19 , 576 pp., Oxford
Drummond, C.N., Wilkinson, B.H. (1993): Carbonate cycle
stacking patterns and hierarchies of orbitally forced
eustatic sealevel change. - Journal of Sedimentary Pe-
trology, 63 , 369-377
Drummond, C.N., Wilkinson, B.H. (1993): Aperiodic accu-
mulation of cyclic peritidal carbonate. - Geology, 21 ,
1023-1026
Einsele, G., Ricken, W., Seilacher, A. (eds., 1991): Cycles
and events in stratigraphy. - 995 pp., Berlin (Springer)
Fischer, A.G., Bottjer, D.J. (eds., 1991): Orbital forcing and
sedimentary sequences. - Journal of Sedimentary Petrol-
ogy, Special Issue, 61 , 1063-1252
Ginsburg, R.N. (1971): Landward movement of carbonate
mud; a new model for regressive cycles in carbonates. -
American Association of Petroleum Geologists, Bulletin,
55 , p. 340
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