GeolCarp_Vol66_No5_393

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On the peritidal cycles and their diagenetic evolution in the

Lower Jurassic carbonates of the Calcare Massiccio

Formation (Central Apennines)

MARCO BRANDANO

1,2

, LAURA CORDA

, LAURA TOMASSETTI

and DAVIDE TESTA

Department of Earth Sciences, Sapienza University of Rome, P. Aldo Moro 5, I-00185, Italy;

laura.corda@uniroma1.it; laura.tomassetti@uniroma1.it; davidetesta.86@gmail.com

Institute of Environmental Geology and Geoengineering (IGAG) CNR, Via Salaria km 29, I-00016, Italy; marco.brandano@uniroma1.it

(Manuscript received March 4, 2015; accepted in revised form June 23, 2015)

Abstract: This paper shows the environmental changes and high-frequency cyclicity recorded by Lower Jurassic shal-
low-water carbonates known as the Calcare Massiccio Formation which crop out in the central Apennines of Italy.
Three types of sedimentary cycle bounded by subaerial erosion have been recognized: Type I consists of a shallowing
upward cycle with oncoidal floatstones to rudstones passing gradationally up into peloidal packstone alternating with
cryptoalgal laminites and often bounded by desiccation cracks and pisolitic-peloidal wackestones indicating a period of
subaerial exposure. Type II shows a symmetrical trend in terms of facies arrangement with peloidal packstones and
cryptoalgal laminites present both at the base and in the upper portion of the cycle, separated by oncoidal floatstones to
rudstones. Type III displays a shallowing upward trend with an initial erosion surface overlain by oncoidal floatstones
to rudstones that, in turn, are capped by pisolitic-peloidal wackestones and desiccation sheet cracks. Sheet cracks at the
top of cycles formed during the initial phase of subaerial exposure were successively enlarged by dissolution during
prolonged subaerial exposure. The following sea-level fall produced dissolution cavities in subtidal facies, while the
successive sea-level rise resulted in the precipitation of marine cements in dissolution cavities. Spectral analysis re-
vealed six peaks, five of which are consistent with orbital cycles. While a tectonic control cannot be disregarded, the
main signal recorded by the sedimentary succession points toward a main control related to orbital forcing. High
frequency sea-level fluctuations also controlled diagenetic processes.

Key words: cyclostratigraphy, diagenesis, Calcare Massiccio, Apennines, Jurassic.

Introduction

One goal of the sedimentologist is to decipher signals re-
corded in the sedimentary record. The carbonate sedimentol-
ogist has to understand how and where carbonate sediments
have been created in response to intrinsic and extrinsic
mechanisms forced by tectonic, eustatic, oceanographic and
climatic processes, and ecological changes (Lukasik & Simo
2008; Strasser & Vedrine 2009; D’Argenio et al. 2011).

Modern carbonate platforms provide a means to examine

how  many  depositional  processes  occur  and  demonstrate  the
complexity  of  facies  associations  (Wright  &  Burgess  2005;
Strasser & Vedrine 2009). When dealing with carbonate plat-
forms in the geological past, detecting facies associations and
the origin of stacked cycles becomes more difficult. In particu-
lar, a long debated problem in stratigraphy is whether to relate
the formation of peritidal carbonate cycles to autocyclic pro-
cesses (Hardie 1986; Pratt et al. 1992) or to allocyclic processes
(both  Milankovitch  and  tectonic  models).  Autocyclic  pro-
cesses include progradation of shorelines and lateral migration
of tidal channels, tidal inlets and bars (Ginsburg 1991). These
processes  are  inherent  to  the  shallowest  environments  of  the
platform (Strasser 1994). Cyclical perturbation of the Earth’s
orbit  induces  changes  in  the  insolation  and  consequently  sea
level,  climatic,  oceanographic,  sedimentary,  and  biological

changes  that  are  potentially  recorded  in  the  sedimentary  ar-
chives through geological time (Strasser 1994; Strasser et al.
2006). In the case of proved Milankovitch cyclicity, the dura-
tion of the smaller-scale depositional sequences lies within the
Milankovitch frequency band, then a very narrow time frame-
work of 20, 41 and 100 to 400 ka can be established (Strasser
et  al.  1999,  2006;  D’Argenio  et  al.  2011).  Twenty-one ka
cyclicity  is  produced  by  the  precession  of  the  equinoxes,
41 ka cyclicity is related to the obliquity of the Earth’s axis,
and the 100—400 ka cyclicity is produced by variation in the
eccentricity of the ellipse of the Earth’s orbit of  ~ 100 (short
eccentricity) and  ~ 400 ka (long eccentricity) periods.

On the basis of stacking patterns and time-series analysis

of western Mediterranean Lower Jurassic shallow-water car-
bonates,  Crevello  (1991)  recognized  a  Milankovitch-type
cyclicity.  However,  tectonic  subsidence  changes  can  also
produce  sedimentary  cycles.  Burgess  (2001)  showed  that
shoreline  and  island  progradation,  controlled  by  subsidence
and  sediment  transport  rate,  are  also  plausible  mechanisms
to  create  variable  thickness,  shallowing-upward  peritidal
parasequences and should be considered in interpretations of
such strata. Based on datasets from different Lower Jurassic
peritidal cycles from western Tethyan platforms, Bosence et
al. (2009) argued strongly for an overriding tectonic control
on cycle formation.

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This paper illustrates the high frequency cyclicity of the

Lower  Jurassic  shallow-water  carbonates  known  as  the
Calcare  Massiccio  Formation.  The  Calcare  Massiccio  For-
mation  belongs  to  the  Tethyan  Liassic  carbonate  platform
domain  that  developed  in  the  large  epicontinental  sea  that
covered shelf areas of present-day North Africa and Western
Europe  as  well  as  the  Apennines  and  the  Pelagonian  plat-
form  of  present-day  Greece  (Bosence  et  al.  2009).  In  the
Apennines,  the  Calcare  Massiccio  Formation  is  character-
ized  by  lateral  variation  in  depositional  environments  and
in thickness, probably related to an articulated physiography
of  the  Triassic  to  Lower  Jurassic  carbonate  platform
(Centamore  et  al.  1971).  For  this  reason,  it  has  been  subdi-
vided  into  a  number  of  lithostratigraphic  sub-units.  The  ar-
ticulated  physiography  was  attributed  to  the  beginning  of
tectonic  extension,  which  created  two  different  domains:  a
persistent carbonate platform (Latium-Abruzzi domain) and a
deep-water  domain  (Umbria-Sabina  Basin)  with  intrabasinal
structural  highs.  On  the  structural  highs,  the  Calcare
Massiccio  Formation  is  characterized  by  peritidal  cyclical
sedimentation  and  is  usually  overlain  by  pelagic  sea-mount
deposits  represented  by  condensed  pelagic  cephalopod-rich
carbonates  of  the  upper  Pliensbachian—Tithonian  Bugarone
unit (reduced sequences) that are no more than a few tens of
metres thick (Centamore et al. 1971; Pialli 1971; Colacicchi
et  al.  1975).  Deposition  in  the  structural  depressions  was
characterized  by  the  relatively  deep,  subtidal  Calcare
Massiccio Formation that does not show evidence for cycli-
cal sedimentation (Santantonio 1993).

Notwithstanding the great extent of the Tethyan Liassic car-

bonate platform, few works have analysed the origin of the
sedimentary cyclicity following a cyclostratigraphic approach
(Bigozzi 1990; Bosence et al. 2000, 2009). This approach
uses astronomical cycles of known periodicities to date and
interpret the sedimentary record (Strasser et al. 2006).

This paper presents an analysis of environmental and dia-

genetic  changes  recorded  in  the  Calcare  Massiccio  Forma-
tion deposited on structural highs. Based on detailed logging
and  facies  analysis  of  a  well  exposed  section,  sedimentary
cycles  are  defined  according  to  cyclostratigraphic  concepts.
This  paper  aims  to  distinguish  the  controlling  factors  pro-
ducing the cyclicity of the Calcare Massiccio Formation, and
to evaluate the role of autocyclic vs. allocyclic processes.

Geological setting

The studied area is located near S. Angelo Romano vil-

lage, in the Cornicolani Mountains (Fig. 1b). These moun-
tains belong to the Apennine chain and represent a structural
high within the Sabina Basin that developed from the
Pliensbachian to Tithonian.

The Apennines are an asymmetric fold and thrust belt de-

veloped  on  top  of  an  eastward-retreating  westward  dipping
continental  slab  attached  to  the  Adriatic  plate  (Doglioni
1991;  Carminati  &  Doglioni  2005;  Carminati  et  al.  2010,
2013).  The  Neogene  to  Quaternary  evolution  of  the  North-
ern-Central Apennines is characterized by east-north-eastward
migration  of  deformation  fronts  of  the  related  foredeeps

coupled with extensional tectonics in the hinterland leading
to the opening of progressively younger backarc basins
(Gueguen et al. 1998).

The central Apennines fold-and-thrust belt consists of a

Meso-Cenozoic  succession  deposited  on  the  Adria  passive
margin  (Fig. 1a).  Deposition  began  with  continental  to  ma-
rine clastic sediments followed first by Upper Triassic dolo-
mitic  and/or  evaporitic  deposits  (Burano  Formation)  and
then  by  Lower  Jurassic  peritidal  carbonates  represented  by
the Calcare Massiccio Formation, which ranges in thickness
from  three  to  seven  hundred  meters  (Pialli  1971).  The
Calcare  Massiccio  Formation  is  generally  dated  Late
Hettangian—Early  Pliensbachian  (Ibex  Biozone).  Deposition
of  peritidal  carbonate  sediments  persisted  from  Late
Hettangian  to  Sinemurian  when  a  rifting  phase  led  to  plat-
form fragmentation and drowning. The resulting complex ar-
chitecture  was  characterized  by  spatial  and  temporal
variations  in  subsidence  rates  (Carminati  et  al.  2013),  pro-
duced  by  extensional  tectonic  processes,  which  created  a
persistent  carbonate  platform  (Latium-Abruzzi  carbonate
platform), a deep-water domain (Umbria-Marche and Sabina
pelagic  basin)  and  intrabasinal  morpho-structural  highs
(Centamore  et  al.  1971;  Damiani  et  al.  1992;  Santantonio
1993; Galluzzo & Santantonio 2002; Cosentino et al. 2004).

From the Sinemurian onward, the Latium-Abruzzi carbon-

ate platform persisted as a monotonous repetition of subtidal
and  peritidal  cycles,  interrupted  by  short  periods  of
emersion, which were associated with bauxite development.
After  the  fragmentation  and  drowning  of  the  Hettangian-
Sinemurian  platform,  the  Umbria-Marche  and  Sabina  do-
main  developed  into  a  wide  pelagic  basin  with  scattered
fault-bounded  structural  highs  (pelagic  carbonate  platforms
sensu  Santantonio  1993)  characterized  by  normal  and  con-
densed  pelagic  deposits,  respectively.  The  structural-high
blocks, within the Umbria-Marche and Sabina domain were
characterized by high subsidence rates occurring during the
deposition of the Calcare Massiccio Formation (Carminati et
al. 2013). With the activation of late Hettangian—Sinemurian
extensional  tectonics,  subsidence  rates  drastically  increased
in the sectors which would later host thick pelagic successions
(the  definitive  drowning  of  the  Calcare  Massiccio  platform
occurred  in  the  Early  Sinemurian).  At  the  structural  highs,
the shallow-water deposition of the Calcare Massiccio Forma-
tion persisted until the Sinemurian—Early Pliensbachian and
was  followed  by  condensed  pelagic  deposits  (Santantonio
1993; Passeri & Venturi 2005).

Analysis of sedimentary cycles in the Calcare Massiccio

Formation  was  first  undertaken  by  Colacicchi  et  al.  (1975).
These authors recognized sequences of facies evolving gradu-
ally  from  subtidal  to  supratidal  environments  arranged  into
predominantly shallowing upward cycles. The authors also re-
ported  the  occurrence  of  cycles,  which  do  not  follow  this
Waltherian  model,  but  document  the  superposition  of
supratidal  facies  directly  on  subtidal  facies.  The  same  cycles
were also recognized by Bigozzi (1990) who showed an orga-
nized stacking pattern consisting of megacycles each compris-
ing  five  individual  cycles  and  interpreted  as  the  product  of
high-frequency sea-level changes probably produced by varia-
tion of orbital parameters. Successively, Bosence et al. (2009)

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presented the analysis of different Lower Jurassic succes-
sions along the Tethys margin including the Apennines suc-
cession in Umbria. These authors recognized five sedimentary
cycles, two of them present in the Umbrian Apennines suc-
cession (

α and γ). According to Bosence et al. (2009), α cycles

are  asymmetrical,  shallowing-upward  cycles  that  evolve  up-
ward from open-marine to subaerial or restricted marine to in-
tertidal  facies  associations.  Cycle  boundaries  are  marked  by
erosional  surfaces  overlain  by  evidence  of  marine  flooding.
The

γ cycles show a symmetrical arrangement of facies with a

transgressive phase, an interval of maximum marine flooding,
followed by a regressive phase capped by an erosional sur-
face. In these cycles, the intertidal and subaerial facies asso-

ciations are well developed and the top of the cycle is charac-
terized by calcretes with tepees. According to Bosence et al.
(2009), both

α and γ cycles may be generated by allocyclic

and autocyclic mechanisms. The other three cycle types char-
acterizing the Liassic platform outside the Apenninic domain
are: the deepening upward

β cycles bounded by an erosional

surface; the asymmetrical

δ cycles composed of subtidal sedi-

mentary facies with a subaerial diagenetic overprint affecting
its upper surface; the

ε cycles, which are characterized by

subtidal  facies  with  a  deepening  upward  trend.  According  to
Bosence et al. (2009), these cycles can be generated only by
allocyclic  controls.  The  common  character  of  these  cycles  is
the  scarcity  of  intertidal  facies,  dominance  of  subtidal  facies

Fig. 1. Geological situation, from general to detail. a – schematic geological map of Central Apennines, b – geological map of Cornicolani
Mountains and location of studied section (modified from Billi et al. 2007).

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and a deepening upward trend indicative of relatively more
open marine environments.

The investigated stratigraphic section comes from the

end of the upper portion of the Calcare Massiccio Forma-
tion cropping out in the Cornicolani Mountains. Many sedi-
mentological works on the Calcare Massiccio demonstrate
a cyclically monotonous alternation of few lithofacies
forming

α and γ cycles (sensu Bosence et al. 2009), al-

though  the  formation  displays  a  remarkable  thickness  of
up  to  700 m  (Pialli  1971;  Colacicchi  et  al.  1975;  Bigozzi
1990; Barattolo & Bigozzi 1996; Passeri & Venturi 2005;
Bosence et al. 2009). In this work, we present a high-reso-
lution  analysis  of  a  very  well  exposed  road  cutting  (26 m
exposed  thickness)  located  in  the  structural  high  of  the
Cornicolani  Mountains  at  the  end  of  the  upper  portion  of
the  Calcare  Massiccio  Formation,  around  40 m  before  the
drowning  succession.  Notwithstanding  the  limited  thick-
ness, this section displays facies associations typical of the
peritidal  cycles  characterizing  the  Calcare  Massiccio  and
can be considered representative of the recorded cyclicity.

Material and methods

An outcrop in an abandoned quarry and a well-exposed

stratigraphic section along the road to S. Angelo Romano
village provide a good opportunity to study the facies as-
sociations  of  Calcare  Massiccio  Formation  (Fig. 1).  Tex-
tural and compositional data were observed in the field at
centimeter  scale,  providing  a  virtually  continuous  sedi-
mentological data set recording the stratigraphic evolution
of  the  investigated  interval.  For  the  sedimentary  cycle
identification we followed the methodology of Bosence et
al. (2009). We used the term sedimentary cycle to identify
commonly  repeated  meter-scale  lithofacies  successions.
These cycles comprise bundles of beds of different thick-
ness  separated  by  erosional  surfaces.  Each  erosional  sur-
face  is  overlain  by  relatively  open  marine  facies  (e.g.
subtidal  facies)  evolving  upward  to  shallower  more  re-
stricted  facies  (from  intertidal  to  supratidal  facies).  The
cycle  boundary  is  placed  at  the  most  prominent  erosional
surface or at a non-Waltherian facies shift at the accommo-
dation  minima,  for  example,  at  the  subtidal  facies  directly
overlying a subaerial exposure surface, or intertidal facies.

In order to better characterize the sedimentary facies and

the composition of the investigated carbonates, 82 samples
were collected along the measured section (Fig. 2). A se-
lected  set  of  70  thin  sections  was  studied  and  classified
according  to  the  nomenclature  of  Dunham  (1962)  and
Embry  &  Klovan  (1971)  for  carbonate  rocks  and  their
compositional  and  diagenetic  characteristics  recorded.
Ten  selected  thin  sections  were  polished  and  examined
under cathodoluminescence (CL) microscopy at the Earth
Science  Department  “Ardito  Desio”  of  the  University  of
Milan.  Twenty  selected  thin  sections,  were  polished  and

Fig. 2. Measured section from the Calcare Massiccio Formation and
thickness recurrences of the main facies associations.

Twenty oxygen and carbon stable isotope analyses were

carried out on 15 samples obtained with a hand-operated
microdrill, using 0.5 mm Ø tungsten drill bits. All of the dif-
ferent recognized cements were sampled. Analyses were per-

carbon-coated and subjected to electron microprobe analysis
to determine the concentration of Mg, Sr, Mn, Fe and Ba
(CAMECA instrument – Istituto di Geologia Ambientale e
Geoingegneria-CNR, University of Roma “La Sapienza”).

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formed using a Finnigan MAT 252 mass spectrometer at the
isotope  geochemistry  laboratory  of  the  Istituto  di  Geologia
Ambientale  e  Geoingegneria-CNR.  The  results  were  cali-
brated using NBS carbonate standard and are reported on the
PeeDee belemnite (PDB) scale. The analytical precision for
the isotope data is  ± 0.1 ‰

based on replicate standards.

Sr/

Sr dating was carried on the micrite of pure lime-

mudstones.  It  was  microdrilled  after  examination  under
cathodoluminescence  with  the  luminescent  portion  being
discarded. Isotopic analyses were performed at IGAG-CNR
(Dipartimento  di  Scienze  della  Terra,  University  of  Rome
“La  Sapienza”)  using  a  Finnigan MAT 262RPQ  multi-
collector  mass  spectrometer.  All  samples  were  loaded  on  a
double  Re  filament  as  nitrate  and  analysed  in  static  mode.
Measured Sr isotope ratios were normalized for mass fractio-
nation to

Sr/

Sr = 0.1194. NBS987 yielded a

Sr/

Sr value

of 0.710235 + /—10. The averaged analytical error (2

σ) of

Sr/

Sr was ± 0.000011 (n = 16). The

Sr/

Sr values of the

samples were converted to numerical ages using Version 4B:
08/04 of the Look-Up Table of Howarth & McArthur (1997).

An observational time series was generated from the mea-

sured stratigraphic section. A numerical value (1—3) was as-
signed to each facies association recognized (Fig. 2). A spot
sampling  method  was  used  to  generate  continuous-signal
records  (Weedon  2003).  The  classical  method  of  searching
for  cyclicity  in  time  series  uses  spectral  analysis.  This
method looks at time series in terms of their frequency com-
position  (Schwarzacher  1993).  Time-series  analysis  of  the
investigated section was performed by using thickness recur-
rences of the main facies associations (Fig. 2). The sampling
interval to perform the time series analysis was 1 cm, which
was chosen based on the facies-thickness data for the investi-
gated section. To mathematically study the signal frequency,
Fourier  analysis  was  performed  with  the  Macintosh-based
software  Analyseries 1.1  (Paillard  et  al.  1996).  The  maxi-
mum  entropy  approach  and  the  Blackman-Tuckey  power
spectrum estimator were used (Blackman & Tuckey 1958).

Results

In the studied section, three lithofacies associations (LF-A,

-B, and -C) were identified based on texture, main constitu-

ents,  fabrics  and  early  diagenetic  features.  These  are  inter-
preted  as  representing  the  three  main  sedimentary  environ-
ments of the inner platform environment represented by the
Calcare  Massiccio  Formation  (Table 1).  According  to  the
studies  on  modern  and  ancient  peritidal  carbonate  systems
(Pratt et al. 1992; Strasser & Vedrine 2009), the sedimento-
logical interpretation leads to a facies model representing the
spatial  distribution  of  the  products  of  different  sedimentary
processes  occurring  in  the  different  environments  of  the
Calcare Massiccio platform.

The investigated section comprises the last interval of the

Calcare Massiccio Formation in the Cornicolani Mountains,
where outcrops occur of about a hundred meters of peritidal
carbonates covered by beds of the drowing succession
(Cosentino et al. 2004).

The isotopic age obtained from strontium isotope analysis

of micrites from the base of the section (Fig. 2) approximates
194.30 Ma confirming a Sinemurian age for the upper part of
the formation. Lastly 19 sedimentary cycles have been rec-
ognized, with thickness ranging between 0.5 and 3 m, with
average of 1.36 m.

Lithofacies associations

LF-A packstones to grainstones with ooids, oncoidal float-

stones to rudstones

This facies association is characterized by two sublitho-

facies:  packstones  to  grainstones  (LF-A1)  and  oncoidal
floatstone  to  rudstone  (LF-A2).  LF-A1  comprises  abundant
ooids, peloids (fecal pellets, algal peloids, microbial peloids)
and  aggregate  grains  such  as  lumps.  The  ooids  show  a  large
micritized nucleus and a very thin cortex characteristic of  su-
perficial  ooids  (sensu  Carozzi  1957).  Typical  skeletal  grains
are  small  benthic  foraminifera  (valvulinids,  textulariids  and
lituolids),  ostracods,  mollusc  fragments  and  cortoids,  small
ammonites,  Cayeuxia,  thaumatoporellids,  and  porostromata
cyanobacteria  (Fig. 3a).  LF-A2  is  dominated  by  oncoids  of
various shape and size (up to 2 cm). Two types of oncoids are
identified:  Type 1  and  Type 2  (sensu  Védrine  et  al.  2007).
Type 1 oncoids are up to 0.5 mm in diameter and show spheri-
cal  to  elliptical  shape  with  smooth  contours.  The  cortex  is
micritic,  homogeneous  and  lacks  associated  microencrusting

Lithofacies associations Sub-lithofacies

Components

Environment

LF-A packstones to
grainstones with ooids,
oncoidal floatstones to
rudstones

Packstones to
grainstones (LF-A1)

Peloids, superficial ooids, lumps and subordinate small benthic
foraminifera, ostracods, mollusc fragments, cortoids, Cayeuxia,
thaumatoporellids, porostromata cyanobacteria

Shallow subtidal environment
under moderately to high
energy conditions
characterizing lagoonal
channels or shoals

Floatstones to
rudstones (LF-A2)

Type 1 and type 2 oncoids, matrix comprising peloids and
skeletal fragments

LF-B peloidal
wackestones to
packstones alternating
with cryptalgal
bindstone

Peloidal wackestones
to packstones (LF-B1)

Peloids, small benthic foraminifera lituolids and textulariids,
small ostracods, serpulids, gastropod fragments and Cayeuxia

Intertidal and supratidal
environment

Bindstones (LF-B2)

Planar algal laminae and trapped mud, type 3 oncoids with
Bacinella irregularis, Lithocodium aggregatum, Cayeuxia,
subordinate type 2 oncoids

LF-C pisolitic-peloidal
wackestones with
extensive sheet-cracks

Pisoids and peloids

Supratidal environment

Table 1: Lithofacies associations of the Calcare Massiccio Formation and their interpreted environmental setting.

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fauna. Laminations are micritic but rarely visible. Nuclei are
lithoclastic and comprise small ooids and/or aggregate grains.
Type 2 oncoids have diameters of between a few millimeters
and 2 cm and elliptical to elongated shapes with smooth con-
tours. The cortex is micritic with laminae easily recognizable.
Laminae are micritic but irregular and locally truncated, show-
ing  different  growth  phases.  Couplets  of  micritic  and  sparry
laminae are present and accentuate the laminar structure of the
Type 2  oncoids.  Both  lithoclastic  (peloids,  ooids)  and  bio-
clastic (echinoid fragments, Cayeuxia) nuclei occur (Fig. 4a).
Occasionally,  small  ooids  are  incorporated  into  the  cortex.
Some  serpulids  and  small  articulated  ostracods  also  occur
within the matrix.

The matrix of the oncoidal floatstones to rudstones con-

sists of fine-grained peloids or skeletal fragments. When the
matrix is lacking, oncoids are usually surrounded by a thin
rim of isopachous fibrous cement and later drusy mosaic ce-
ment. Dissolution cavities are diffuse and infilled by drusy
mosaic cement (Fig. 5a).

Interpretation:

This facies association was deposited in a shallow subtidal

environment under moderate to high energy conditions char-
acterizing  lagoonal  channels  or  shoals  (Colacicchi  et  al.
1975;  Barattolo  &  Bigozzi  1996;  Pomoni-Papaioannou  &
Kostopoulou  2008)  as  demonstrated  by  the  textural  charac-

Fig. 3. Field photographs of the recognized lithofacies associations. a – LF-A packstone to grainstone with ooids, oncoidal floatstone to
rudstone that forms decimetric thick beds; b – LF-B peloidal wackestone to packstone with birdeyes and laminated bindstone; c – LF-C
pisolitic-peloidal wackestone alternating with extensive sheet-cracks; d – detail of sheet cracks overlaid by oncoidal rudstone; e – photo-
micrograph of sheet cracks with isopachous radiaxal fibrous cement (rf) followed by blocky cement (b).

Fig. 4. Photomicrographs of the lithofacies associations. a – LF-A, oncoidal rudstone, dominated by Type 2 oncoids; b – LF-B, cryptal-
gal bindstone consisting of micritic laminae (black arrows) produced by microbial mat, fine grained laminated peloidal packstone to grain-
stone passing into peloidal wackestone and fenestral cavities (white arrow); c – LF-C, laminated crust, composed of radiaxial fibrous
cement and thin micritic laminae. Note the articulated ostracod concentration (black arrow); d – type 2 oncoids with Cayeuxia nuclei, and
isopachous fibrous cement around the oncoids; e – dissolution cavity with a fibrous cement rim and drusy mosaic cement in the central
portion; f – detail of the crust of fibrous cement consisting of two or more growth zones of cloudy fibrous crystals a few millimeters in
size (black arrow), growing perpendicularly to the substrate; g – detail of drusy mosaic cement; h – this drusy cement under cathodolu-
minescence is alternating bright and non-luminescent.

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teristics. Shallow water, high energy conditions are also sup-
ported by the presence of oncoids that were able to overturn
and roll (cf. Védrine et al. 2007) as demonstrated by their
sub-spherical to elliptical shape.

LF-B peloidal wackestones to packstones alternating with

cryptalgal bindstone

This facies association comprises two sublithofacies: (i) pel-

oidal  wackestones  to  packstones  (LF-B1)  alternating  with
(ii) cryptalgal bindstone with birdseyes and fenestral fabrics
(LF-B2)  (Figs. 3b  and  4b).  Geopetal  structures  and  irregu-
larly  shaped  peloidal-micritic  intraclasts,  derived  from  un-
derlying lithologies, were also recognized.

Fenestrae are usually filled with drusy calcite; in some cases

large  irregular  stromatactoid  voids  filled  with  fine-grained
sediment  are  also  recognizable.  Peloids  are  up  to  500 µm  in
diameter  and  equal-sized  and  they  are  associated  with  small
benthic  foraminifera  lituolids  and  textulariids,  small  ostra-
cods,  serpulids,  gastropod  fragments  and  Cayeuxia.  Gastro-
pods  and  ostracods  are  often  recrystallized  and  articulated
ostracods may be preserved in the center of cavities filled with
radial fibrous calcite.

Bindstones (LF-B2) are composed of stromatolitic layers,

planar algal laminae and trapped mud (Fig. 4b). Couplets of
micritic and clotted peloidal layers occur. This facies associa-
tion is characterized by Type 3 oncoids (sensu Védrine et al.
2007). These oncoids are between 0.5 mm and 3 cm in dia-
meter and show a sub-elliptical to lobate shape with wavy and

Fig. 5. a – dissolution cavity with fibrous cements, black arrows show leached grains, solution enlarged pores; b – isolated euhedral pla-
nar crystals of dolomite within the fine grained matrix interval of LF-B and LF-C facies associations.

Fig. 6. Sketch illustrating the diagenetic imprint after the deposition
of the sedimentary cycle of Calcare Massiccio. a – sheet cracks
formed during initial subaerial exposure are successively enlarged by
dissolution during prolonged subaerial exposure; b – the sea-level
fall results in the enlargement of the meteoric zone and the lowering
of the mixing zone producing dissolution cavities; c – sea-level rise
produced the space for the accumulation of the overlying sedimentary
cycle and precipitation of marine cement in the dissolution cavities.

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irregular contours. The cortex comprises an alternation of or-
ganism-bearing  and  subordinate  micritic  laminae.  Micritic
laminae are rarely continuous. The organism-bearing laminae
are predominant and comprise the microencrusting organisms
Bacinella  irregularis  (Radoičić,  1959)  and  Lithocodium
aggregatum  (Elliott,  1956).  Bacinella  and  Lithocodium  are
commonly assumed to be cyanobacterial organisms character-
ized  by  an  irregular  microbial  meshwork,  alveoli  and
interspaces  filled  with  microsparry  calcite  (Schmid  &
Leinfelder 1996; Duprax & Strasser 1999). Oncoid nuclei are
mainly  bioclastic,  made  of  echinoid  or  Cayeuxia  fragments
and  gastropods,  but  also  include  small  peloids  or  aggregate
grains. Occasionally, small Type 2 oncoids with a Bacinella—
Lithocodium envelope occur.

Micritic layers in this facies may show partial dolomitiza-

tion with dolomite forming clear euhedral rhombs (Fig. 5b).

Interpretation:

This facies association is interpreted as the deposits of in-

tertidal and supratidal environments. A characteristic feature
of peritidal carbonates are millimeter-scale microbial lami-
nated sediments commonly associated with fenestral and
birdseye fabrics (Tucker & Wright 1990). Their preservation
is most common in the upper intertidal zone as they are fre-

quently disrupted by bioturbation in subtidal and lower inter-
tidal environments.

Type 3 oncoids indicate relatively low-energy conditions

characterized by Bacinella—Lithocodium. In fact, these micro-
encrusters dominate in low to very low energy settings
where the microbial meshwork had time to grow (cf. Védrine
et al. 2007).

LF-C pisolitic-peloidal wackestones with extensive sheet-

cracks

This facies association consists of barren mudstones to

wackestones,  which  are  locally  dolomitized.  The  only  fauna
preserved  are  articulated  ostracods  (Fig. 4c).  These  deposits
are characterized by the presence of sheet-cracks and laminoid-
irregular  fenestrae.  The  sheet-cracks  can  be  laterally  con-
tinuous  on  a  decimeter  to  meter  scale  and  are  lined  by  an
isopachous rim followed by coarse blocky calcite (Fig. 3c,d,e).
Sheet-cracks consist of radiaxial fibrous calcitic cement with a
horizontal  or  undulating  trend  (Figs. 3d  and  4c).  The  cracks
are up to 3 cm thick and occur individually or in stacked sets.

The sheet-cracks may be superimposed on the facies of

LF-A and LF-B. They are often associated with pisolitic
wackestones. Pisoids are centimeter-sized grains (up to 3 cm)

Cement

Mn (ppm)

Fe (ppm)

Sr (ppm)

Ba (ppm)

Mg (ppm)

O ‰

C ‰

Isopachous

fibrous

224 70

693 331 3023

–0.9

2.08

418 241 481 188 2927

–0.80

2.03

255 404 549

0 3074

–1.3

1.7

224

211

376

2244

464 0 33 232 2960

0 310 515

0 2432

85 0

515 277

2089

464 0 67 420 2698

Drusy

mosaic

224 326 0

0 2206

–1.32

1.17

0 0 0 0

2273

–1.87

1.11

139 0

169 0

1197

–1

1.01

0 139 279

0 2764

673 295.4 0

0 2106

Blocky

177

2404

–3.97

0.34

263 0

33.8 0

2529

–3.45

1.01

0 0 0 0

1400

–3.8

0.8

0 0 0 0

1616

Radiaxial

fibrous

464 0 67 420 2692

–2.21

2.25

0 178 0 1200 1357

–1.15

2.5

309 101 0 653 1993

–0.35

3.42

0 264 0 850 2495

–0.53

3.02

54 0

254 770

2931

–1.74

2.75

170 124 346 609 1000

–1.2

1.6

139

169

806

1411

–1.15

0.3

0 178 0 797 1009

–1.02

278 363 0 698 2479

–0.80

1.6

0 101 0 609 2395

–1.02

2.8

Dolomite

0 0 0 0

43600

0 0 0 0

110340

0 0 0 0

80000

0 0 0 0

103430

0 0 0 0

94000

0 0 0 0

125780

0 0 0 0

116000

0 0 0 0

108750

0 0 0 0

60050

Table 2: Summary of the geochemical and isotopic data of the recognized cements.

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with  a  concentric  laminated  structure.  Nuclei  are  mainly
small peloids and aggregate grains. Laminae are made of an
alternation  of  thin  micritic  laminae  and  calcitic  microspar.
Some  pisoids  are  fractured  and  fragmented.  Peloidal  bands
with oxidized iron staining and some root-related structures
also occur.

Some laminae are heavily disrupted by bioerosion traces.

Interpretation:

This facies association is interpreted as deposits from a

supratidal  environment.  The  interpretation  is  based  on  the
abundance  of  laminar  sheet  cracks  and  features  related  to
subaerial  diagenesis,  such  as  vadose  pisolites,  diffuse  red-
dish iron oxides testifying extended periods of exposure, and
partial dolomitization.

Diagenetic features

Four main types of calcitic cement were recognized in the

analysed  rocks:  1) isopachous  fibrous  cement  on  oncoids
and bioclasts; 2) drusy mosaic cement infilling intergranular
pores  and  dissolution  cavities;  3) crusts  of  radiaxial  fibrous
cement  constituting  the  sheet  cracks;  4) blocky  cement  oc-
cluding  large  pores  between  the  crusts  of  sheet  cracks.  The
diagenetic feature includes also the presence of dolomite that
occurs as matrix-dolomite.

The isopachous fibrous cement consists of closely packed

crystals (10

×70 µm) and occurs in interparticle and vuggy

pores (sensu Choquette & Pray 1970), and in dissolution
cavities (Figs. 4d, 5a). This cement is non-luminescent under
cathodoluminescence (CL), is non ferroan-to slighty ferroan,
with moderate Sr, Mn and Mg concentrations. Stable isotope
values of this cement are around —0.90 ‰ for

O, and be-

tween + 2.80 ‰ and + 1.70 ‰ for

The drusy mosaic cement developed mainly in interpar-

ticle  and  vuggy  pores,  and  subordinately  in  intraparticle
pores. It is characterized by a mosaic of polygonal, anhedral
crystals  ranging  in  size  between  50 µm  and  250 µm
(Fig. 4e). Under CL, it comprises alternating bright and non-
luminescent bands (Fig. 4g,h), with moderate Fe, Mn and Sr
concentrations  (Table 1).  Stable  isotope  values  are  around
—1.00 ‰ for

O and + 1.00 ‰ for

The crusts of radiaxial fibrous cement consist of two or

more  growth  zones  of  cloudy  fibrous  crystals  3—4 mm  in
length,  growing  orthogonal  to  the  substrate  and  showing
undulose  extinction  (Fig. 4f).  This  cement  does  not  exhibit
luminescence under CL. It is non-ferroan and Mg concentra-
tions vary between 1300 and 2900 ppm. This cement is char-
acterized by a Ba content of up to 1200 ppm. Stable isotope
values  range  between  —0.35 ‰  and  —2.20 ‰  for

O and

+ 0.30 ‰ and + 3.40 ‰ for

The blocky cement is found in large pores between crusts

of radiaxial fibrous cement in the sheet cracks. This cement
is  characterized  by  subhedral  to  anhedral  crystals  ranging
from 0.2 to 1 mm in size. This cement is not luminescent un-
der CL and is non-ferroan with moderate Mg concentrations
(between  2100  and  2400 ppm).  Stable  isotope  values  range
from  —3.45 ‰  to  —4.00 ‰  for

O and from + 0.34 ‰ to

+ 1.10 ‰ for

C (Table 2).

Dolomite is represented by isolated euhedral planar crystals

or scattered patches within the fine grained matrix interval of
LF-B and LF-C facies associations (Fig. 5b). Crystals are me-
dium in size ranging between 50 and 120 µm. Dolomite oc-
curs within micritic layers 1—2 cm thick bounded by stylolites.
The analysis of major and trace elements indicate that dolo-
mite is characterized by an excess of Ca, while trace elements
are absent or present in very low concentrations (Table 2).

Interpretation:

The diagenetic features suggest that sheet cracks were

formed  during  the  initial  phase  of  subaerial  exposure
(Fig. 6a—c), with cavities becoming infilled by sediments, and
were  successively  enlarged  by  dissolution  during  prolonged
subaerial  exposure.  The  pisolitic  wackestone  facies,  associ-
ated with the sheet cracks, are interpreted as a caliche product
(cf. Assereto & Kendal 1977; Mutti 1994). A further sea-level
fall resulted in the enlargement of the meteoric zone and the
lowering of the transition zone between the meteoric and ma-
rine water (the mixing zone). Aggressive meteoric and mixing
zone water then produced dissolution cavities in subtidal LF-A
facies (Fig. 6b). The following sea-level rise resulted in the pre-
cipitation of marine cements in dissolution cavities (Fig. 6c), in-
cluding crusts of radiaxial fibrous cement in the sheet cracks.
This  cement  is  not  luminescent,  suggesting  it  precipitated  in
oxygenating conditions and it is characterized by isotopic val-
ues  consistent  with  Jurassic  marine  waters  (Prokoph  et  al.
2008). The high concentration of Ba suggests the presence of
decaying  organic  matter  probably  related  to  the  presence  of
microbial  mats  (Table 2).  Barite  precipitates  inorganically
directly  from  seawater  in  microenvironments  containing  de-
caying  organic  matter  and  other  biogenic  remains  (Bishop
1988; Dehairs et al. 1990; Ganeshram & Francois 2002).

After the deposition of subtidal LF-A, isopachous fibrous

cement precipitated on oncoids and bioclasts. This cement is
not luminescent and has a geochemical character and isotopic
composition  indicating  precipitation  from  marine  waters
(Table 2,  Fig. 7a—d).  The  drusy  mosaic  cement  infilling  the
dissolution cavities and interparticle pores is alternating bright
and non-luminescent under cathodoluminescence (Fig. 4h). It
is  non-ferroan,  and  has  moderate  Mn  and  Sr  concentrations.
These characteristics indicate precipitation in fluctuating oxy-
genated to suboxygenated conditions typical of the deeper part
of the marine phreatic zone (Lohmann 1988; James & Coquette
1990).  The  blocky  cement  filling  larger  cavities,  especially
within sheet cracks, has an isotopic composition and lumines-
cence consistent with precipitation under meteoric conditions.

Dolomite was only locally developed and occurs in asso-

ciation with muddy textures, stylolites and pressure solution
seams. There is no evidence of former evaporites, therefore it
is interpreted as a product of burial diagenesis. Burial dolo-
mites are widely documented in the Lower Jurassic carbon-
ates of the southern and northern Apennines (Ronchi et al.
2003; Iannace et al. 2011).

Sedimentary cycles

In this work, the term sedimentary cycle is used to identify

commonly repeated meter-scale succession of facies associa-

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Fig. 7. Scatter diagrams of element compositions for the recognized cements. a – Mg vs. Ba, b – Sr vs. Ba, c – Mg vs. Sr, d – carbon
and oxygen isotopic composition.

tion (cf. Strasser et al. 1999; Bosence et al. 2009). The cycles
occur  as  bundles  of  the  recognized  facies  associations  and
are bounded by a discontinuity surface. This surface is over-
laid by subtidal facies of the following cycle. As observed by
Bosence et al. (2000), the cycle tops are not immediately rec-
ognizable as they do not weather out on natural rock surfaces
and  their  occurrence  only  becomes  apparent  from  detailed
bed-by-bed  logging.  Once  confidently  identified,  the  cycle
tops  may  be  followed  for  many  hundreds  of  meters  in  the
open quarry and road cut.

On the basis of the facies association stacking pattern,

three  types  of  sedimentary  cycle  were  recognized:  classic
shallowing-upward  cycles  (Type I),  symmetrical  cycles
(Type II),  and  shallowing  upward  cycles  with  non-
Waltherian facies shifts (Type III) (Fig. 2).

Type I consists of a sedimentary cycle produced by a re-

peated meter-scale shallowing upward succession (Fig. 8A).
The cycles are 0.5 to 2.5 m thick and either become finer or
coarsen upward. They start with an erosion surface overlain
by oncoidal floatstones to rudstones (LF-A). The basal ero-
sional surface shows an irregular morphology, evidence of

subaerial  exposure,  and  a  sharp  contact  with  the  overlying
LF-A  facies  that  may  contain  reworked  lithoclasts  and
intraclasts  from  the  underlying  LF-C  facies.  The  oncoidal
floatstone  to  rudstone  passes  gradationally  up  into  peloidal
packstone  alternating  with  cryptoalgal  laminites  (LF-B).
Some cycles may show lenticular oncoidal beds, up to 30 cm
thick laterally passing into peloidal packstone of LF-B. This
cycle  is  bounded  by  LF-C  facies  that  are  connected  with  a
period  of  subaerial  exposure  (Fig. 2).  Rarely,  the  cycle  is
capped by LF-B.

Type II is 3 m thick and shows a symmetrical trend in

terms of facies arrangement with peloidal packstone and
cryptoalgal laminites present both at the base and in the up-
per portion of the cycle, separated by oncoidal floatstones to
rudstones. Sheet-cracks associated with pisolitic-peloidal
wackestones (LF-C) characterize the top of the cycle.

Type III cycles are between 0.5 and 1 m thick (Fig. 8b).

These  cycles  show  non-Waltherian  facies  shifts.  An  initial
erosion  surface  is  overlain  by  oncoidal  floatstones  to
rudstones  with  skeletal  fragments  (LF-A),  capped  by  desic-
cation  cracks  and  pisolitic-peloidal  wackestones  (LF-C).  In

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Fig. 8. a – meter-scale shallowing upward sedimentary cycle type I showing the vertical evolution from the subtidal oncoidal floatstones
to rudstones facies (LF-A) to the supratidal peloidal packstone alternating with cryptoalgal laminites facies (LF-B) passing upward to the
pisolitic-peloidal wackestone facies associated with sheet-cracks (LF-C). The base and the top of the cycle are characterized by an erosional
surface. Dashed lines indicate the base and top of the cycle; b – Type III sedimentary cycle displaying basal erosion surface overlain by
oncoidal floatstones to rudstones (LF-A), capped by desiccation cracks and pisolitic-peloidal wackestones (LF-C) delimited by another ero-
sional surface corresponding to the top cycle.

this cycle the meteoric overprint is enhanced and penetrates
deeply into the underlying oncoidal facies, which show dis-
solution features suggesting prolonged exposure.

Spectral analysis

Six main peaks have been identified in the power spectra

of the investigated sections (Fig. 9): peak 1 at a frequency of
0.330995  (3.12 m),  peak 2  at  0.380177  (1.8 m),  peak 3  at
0.307043  (1.35 m),  peak 4  at  0.158386  (0.97 m),  peak 5  at
0.090113  (0.83 m)  and  peak 6  at  0.088033  (0.61 m).  To  in-
terpret  the  origin  of  the  observed  high-order  cyclicity,  cal-
culated ratios between peak frequencies were compared with
estimated ratios for Jurassic cycles reported by Berger et al.

Table 3: Comparison between a) the values estimated by Berger et al. (1989)
and b) the peak-frequency ratios calculated in this work.

(1989) (Table 3a). We followed the methodology of
D’argenio et al. (1997, 1999) to estimate the cycle
duration.  This  was  calculated  by  comparing  the
relative ratio sets for the cycle expressed in meters
(Table 3b), with the relative ratio sets of orbital pa-
rameters (Table 3a). The two ratio sets show a very
good  linear  correlation  (r > 0.98),  suggesting  that
the  Calcare  Massiccio  cycles  of  the  investigated
section  had  a  hierarchical  organization  controlled
by Earth’s orbital perturbation.

The most prominent peaks (1.8 m and 1.35 m)

are consistent with obliquity cycles, the 3.12 m
peak approximates to a short eccentricity cycle
(period of 95 ka), and the small peaks (0.83 m and
0.61 m) approximate to the two precession cycles
(21.5 ka and 18 ka, respectively). Peak 4 (0.97 m)
is not consistent with orbital cycles.

Discussion

Type I cycles correspond to the classic peritidal cycle char-

acterized  by  a  shallowing  upward  evolution  and  match  the
α cycle of Bosence et al. (2009). This cycle is the most com-
mon in the investigated section and it represents the product of
regression  and  infilling  of  accommodation  space.  Lithofacies
changes in peritidal carbonates may be caused by relative sea-
level  changes,  but  also  by  sediment  supply,  increased  wave
erosion or development of bedforms reducing tidal exchange
(Tucker & Wright 1990). Consequently, Type I cycles may re-
sult both from autocyclic and allocyclic processes.

Type II cycles show a symmetrical facies arrangement with

an intertidal facies association at the base and top separated by

404220

95000

47000

37000

21500

18000

a
404220 1

4.254947 8.600426 10.92486 18.80093 22.45667

95000

0.235021 1 2.021277 2.567568 4.418605 5.277778

47000

0.116273 0.494737 1

1.27027

2.186047 2.611111

37000

0.091534 0.389474 0.787234 1

1.72093

2.055555

21500

0.053188 0.226315 0.457446 0.581081 1

1.194444

18000

0.04453

0.189473 0.382978 0.486486 0.837209 1

3.12

1.80

1.35

0.97

0.83

0.61

3.12 1 1.733333 2.311111 3.216495 3.759036 5.114754
1.80 0.576923 1 1.333333 1.85567

2.168675 2.95082

1.35 0.432692 0.75

1.391753 1.626506 2.213115

0.97 0.310897 0.538889 0.718519 1

1.168675 1.590164

0.83 0.266026 0.461111 0.614815 0.85567

1.360656

0.61 0.195513 0.338888 0.451852 0.628866 0.73494

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a subtidal facies association. This cycle corre-
sponds to the

γ cycle of Bosence et al. (2009) and

records a gradual transgressive phase followed by
regression. This cycle could also result from either
autocyclic or allocyclic processes.

The facies arrangement of Type III cycles

shows subtidal facies directly overlain by supra-
tidal  facies.  Consequently,  this  cycle  records  a
marked sea-level fall resulting in subaerial expo-
sure  of  subtidal  facies.  In  this  case,  the  cycle
forms  as  a  result  of  relative  sea-level  fall  that
may  be  caused  by  allocyclic  processes  such  as
eustasy or tectonic uplift.

Spectral analysis is considered an objective

method  for  the  detection  of  regular  cyclicity  in
data  recording  oscillating  parameters  (Weedon
1989). In this case the sedimentary record is rep-
resented by a repetitive meter-scale succession of
facies associations. In this study, spectral analy-
sis  suggests  that  the  observed  cyclic  pattern  of
the  Calcare  Massiccio  was  controlled  predomi-

paleoseismites were documented, which would have provided
evidence for an active tectonic control during deposition.

Based on spectral analysis results, we conclude that the

signal recorded in the studied succession points toward an
orbital forcing control on deposition of the Calcare Massicio
Formation.

High frequency sea-level fluctuations also controlled dia-

genetic processes in the Calcare Massiccio. Sea-level varia-
tions, by inducing changes in the water table, play a key role
in exposing the peritidal cycles to the marine, mixed marine/
meteoric and vadose meteoric zones (Fig. 6a,b,c). As a con-
sequence, they are responsible for the cyclical dissolution in
the vadose and mixing zone and the following precipitation
of cements (cf. Mutti 1994).

Conclusion

The present paper illustrates an integrated workflow for

the characterization of the Calcare Massiccio shallow-water
carbonates coupling facies analysis, cyclostratigraphy and
petrography.

The study highlights that the Calcare Massiccio, which de-

veloped  on  the  structural  high  within  the  Sabina  basin  do-
main,  is  organized  into  meter-scale  shallowing  upward
cycles  bounded  by  subaerial  exposure  surfaces.  The  most
frequent  cycles  show  vertical  evolution  from  a  subtidal  fa-
cies association (oncoid dominated) to a supratidal facies as-
sociation with well-developed sheet cracks.

Spectral analysis reveals prominent peaks consistent with

obliquity cycles and short eccentricity cycles, while small
peaks approximate to the two procession cycles. Nevertheless,
one of the recorded peaks is not consistent with any orbital
cyclicity.

We conclude that, in the Calcare Massiccio, a tectonic

control on sedimentary cycle development cannot be disre-
garded, but the signal recorded by the sedimentary succes-
sion points toward a significant control by orbital forcing.

Fig. 9. Blackman-Tukey power spectrum estimation from the investigated sec-
tion of Calcare Massiccio. The power spectrum indicates how much of the sig-
nal is at the recognized frequencies. The peaks show the periodicities (p = 1/f,
f = frequency) recognized in the studied section.

nantly by orbital forcing. The vertical staking pattern of sedi-
mentary  cycles  indicates  a  cyclical  variation  in  cycle  thick-
ness along the section (Fig. 2). Elementary cycles are related
to either the Earth’s precession or obliquity signal (or a com-
bination  of  both).  The  elementary  cycles  are  hierarchically
organized  into  bundles  (seven  groups  of  1—4  elementary
cycles)  and  the  bundles  into  superbundles  (two  groups  of  4
bundles),  which  correspond  to  short  ( ~ 100 ka)  and  long
( ~ 400 ka)  eccentricity  signals,  respectively.  Consequently,
the  investigated  portion  of  the  Calcare  Massiccio  shows  an
accumulation rate of 1 m/30 ka, which is in agreement with
the  values  recorded  for  the  Tethyan  Liassic  carbonate  plat-
forms (see fig. 2 from Bosence et al. 2009).

The vertical variation of elementary cycle thickness sug-

gests  that  the  orbital  cycles  are  superimposed  on  long-term
transgressive—regressive facies trends. A transgressive facies
trend  is  singled  out  on  the  basis  of  an  upward  increase  in
thickness  of  elementary  cycles,  while  a  regressive  trend  is
marked by a decrease of elementary cycle thickness and an
increase in restricted lagoonal deposits (LF-C and LF-B).

The carbonate cycle of the Lower Jurassic shallow-water

platform in the High Atlas of Morocco has similarly been in-
terpreted as been related to sea-level changes driven by or-
bital forcing (Crevello 1990, 1991).

However, the influence of autocyclic controls cannot be

totally excluded because the investigated facies were depos-
ited  in  a  sedimentary  environment,  the  tidal  flat,  where
autocyclic  processes  are  documented.  Furthermore,  auto-
cyclic  strata  may  be  stacked  as  apparently  allocyclic  strata
(Burgess 2006). The spectral analysis records one periodicity
not consistent with orbital parameters, which may have been
produced by autocyclic processes (Fig. 9).

Bosence et al. (2009) suggested a pulsed tectonic control for

the creation and filling of accommodation space of some of
the Calcare Massiccio peritidal cycles. However, fault activity
is unlikely to be the major control on cycle repetition on ex-
tensive carbonate platforms (Tucker & Wright 1990). In this
study, and in general in the Calcare Massiccio Formation, no

406

BRANDANO, CORDA, TOMASSETTI and TESTA

GEOL

EOL

EOLOGICA CARPA

OGICA CARPA

OGICA CARPATHICA

THICA

THICA, 2015, 66, 5, 393—407

The diagenetic characteristics of Calcare Massiccio are

linked to high frequency sea-level fluctuations, which pro-
duced dissolution during sea-level fall and cement precipita-
tion during following sea-level rise as illustrated by marine
cements precipitated inside sheet cracks developed on top of
the cycles.

Acknowledgments: Financial support from MIUR (PRIN

2010-11  Research  Grant  20107ESMX9_001  and  Sapienza
Ateneo Project 2014) are gratefully acknowledged. Criticism
and  comments  by  František  Vaček  and  an  anonymous  re-
viewer greatly improved the manuscript. Comments by Editor
Jindřich Hladil are much appreciated. The authors would like
to thank Flavio Jadoul for the cathodoluminescence analysis.
Discussions in the field with Alessandro Lanfranchi were very
useful.  Mariano  Parente  is  thanked  for  assistance  with  the
Strontium Stratigraphy. Useful discussions with Dan Bosence,
Fotini  Pomoni-Papaioannou,  Sabrina  Amodio  and  Julien
Michel  are  much  appreciated.  Marcello  Serracino  is  thanked
for the assistance with EDS-WDS analyses. We thank James
Hodson (RPS Energy) for comments and English review.

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