Geology Reference
In-Depth Information
Ideal Mendola Cycle
Ideal Latemar Cycle
(Goldhammer et al ., 1987)
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Unit 2 : Dolomitized M/W;
mm-scale planar to wavy
laminae, cm-scale v-shaped
polygons. (Mudcracked
cryptomicrobial laminite -
Peritidal )
Unit 2 : Dolomitized P/G;
mm-to-cm-scale coated
grains, fenestrae, sheet
cracks, cement-filled voids.
(Dolomitized vadose
diagenetic cap)
Unit 1 :
(a) Coarse, sand-to-
gravel sized oncolitic,
lithoclastic grainstone
Unit 1 : Dolomitized M/W;
peloidal, fine-bioclastic
debris; mm-scale wispy
incipient lamination, rare
burrows, rare cm-scale vugs.
Basal contact is erosive,
consisting of entrained
mm-cm scale flat laminite
clasts from the underlying
laminite. Upper 10 cm
consists of coarse skeletal
(dasycladacean) grainstone
which grades upward into
fenestral P/G with discontin-
uous mm-scale laminations.
(Shallow restricted subtidal
lagoon; shallowing-upward
into intertidal storm-reworked
grainstone beneath peritidal
cap )
(b) Medium to very
coarse sand-sized
skeletal grain packstone
to grainstone
(c) Very fine to fine sand-
sized peloidal, restricted
skeletal wackestone to
packstone
( Shallow restricted subtidal
lagoon; shallowing-upward
into shallow, higher-energy
lagoon beneath vadose cap)
0
Components
Tepee structure
Pendant cements
Dolomitic caliche
Dessication crack
Cryptomicrobial laminite
Oncoid
Bioclast
Dasycladacean algae
Ideal Latemar Cycle
(Egenhoff et al ., 1999)
Microfacies
5 : Dolomitic caliche crust or
tepee. Diagenetically overprinted
coated grain P/G. (Subaerially
exposed) .
4 : Oncoid/bioclastic P/G. (High
energy intertidal to supratidal) .
3 : Fenestral W/P with peloids
and lumps. (Transition between
shallow subtidal and intertidal) .
Micritized grains/lumps
Mixed skeletalal lochems
Firmground/scour
Peloids/pellets
Flat intraclasts
2 : Dasycladacean algae-bearing
packstone. (Reworked shallow
subtidal)
1 : Dasycladacean algae-bearing
peloidal W/P. Common erosive
bases with flat pebbles.
(Transgressive reworking
followed by low energy
shallow subtidal)
Dunham textural classification
M = mudstone, W = wackestone,
P = packstone, and G = grainstone
Fig. 3. Comparison of 'ideal' shallowing-upward cycles as observed at Mendola Pass (this study) and in the Latemar
buildup (Goldhammer et al ., 1987; Egenhoff et al ., 1999).
The recognition of an intertidal facies in the
Latemar cycles is important because it affects the
fundamental conclusion held earlier (Goldhammer
et al ., 1987), that the cycles were a record of eus-
tatic oscillations because of the Waltherian skip in
facies succession. The interpretation by Egenhoff
et al . (1999) for a full shallowing-upward suite of
environments allows for Ginsburgian autocyclicity
as a possible driver that does not require eustatic
oscillations (Ginsburg, 1971). This makes confi r-
mation of an allocyclic driver for the Latemar all
the more pertinent.
Mendola cycles
The facies succession internal to the Mendola Pass
cycles is fundamentally different to that of the
platform interior cycles at Latemar. Rather than
 
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