Marine Geology 336 (2013) 84–98
Contents lists available at SciVerse ScienceDirect
Marine Geology
journal homepage: www.elsevier.com/locate/margeo
Mud volcanoes along the inner deformation front of the Calabrian Arc accretionary
wedge (Ionian Sea)
G. Panieri a,⁎, A. Polonia a, R.G. Lucchi b, S. Zironi c, L. Capotondi a, A. Negri d, L. Torelli e
a
ISMAR-CNR, Bologna, Italy
Istituto Nazionale di Oceanografia e Geofisica Sperimentale (OGS), Trieste, Italy
Dipartimento di Scienze della Terra e Geologico-Ambientale, Università di Bologna, Italy
d
Dipartimento di Scienze della Vita e dell'Ambiente, Universita' Politecnica delle Marche, Ancona, Italy
e
Dipartimento di Scienze della Terra, Università di Parma, Italy
b
c
a r t i c l e
i n f o
Article history:
Received 30 July 2011
Received in revised form 24 October 2012
Accepted 12 November 2012
Available online 5 December 2012
Communicated by G.J. de Lange
Keywords:
Mud volcano
Massive mud breccia
Patchy/cloudy mud breccia
Fluid emission
Accretionary wedge
Calabrian Arc
Mediterranean Sea
a b s t r a c t
We present geophysical data integrated with the analysis of well-targeted sediment samples in order to contribute to a better understanding of fluid circulation in the Calabrian Arc accretionary wedge. Two cores
(BS81/II 5 and BS81/II 10) collected on a swell in the hangingwall of the inner deformation front show
upper Pleistocene mud breccias that include Cretaceous to Late Miocene rock fragments mechanically
incorporated into the eruption deposit by the upward transport of overpressured fluids. An additional core
(CALA 21) came from the summit of a topographic high in the footwall of the inner deformation front of
the accretionary wedge and contains a mud breccia patchy/cloudy facies where sediment disturbance is
caused by fluid expulsion. Integration of the entire data set provides evidences of the interplay among tectonics, fluid emissions and sedimentation, and enables the identification of two new volcanoes in the accretionary prism where overpressuring due to Pliocene and Pleistocene sediment accumulation and the evolution of
active fault systems triggered fluid circulation and the formation of those structures.
© 2012 Elsevier B.V. All rights reserved.
1. Introduction
Mud volcanoes form as a result of the eruption of argillaceous material on the Earth's surface or the sea floor, and have been described on
both active and passive margins (Kopf, 2002). The main driving process
producing eruptions is overpressured methane rising from reservoirs
and source rocks at greater depths. Clastic material, saturated with gas
and other fluids is transported through the feeder channel of mud volcanoes in a clay/silt fluidized matrix and deposited on the seafloor (Ivanov
et al., 1998). The erupted sedimentary material is called “argille scaliose”
(literally ‘scaly clays’ or ‘scaly argillites’) (Bianconi, 1840; Wiedenmayer,
1950; Ogniben, 1953) “diapiric melange” (Williams et al., 1984; Barber et
al., 1986; Brown, 1990) or more frequently, “mud breccia” (Cita et al.,
1981; Akhmanov, 1996). It consists of a complex mixture of a matrix
and rock fragments, mechanically incorporated into the eruption deposit
by the powerful upward fluid transport (Akhmanov, 1996; Akhmanov
and Woodside, 1998).
Mud volcanoes (Mvs) are the most remarkable indications of
methane/gas seepage and are often positive, dome-like topographic
structures of up to tens of kilometers in diameter and several hundred
⁎ Corresponding author. Tel.: +39 051 6398915; fax: +39 051 6398940.
E-mail address: [email protected] (G. Panieri).
0025-3227/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.margeo.2012.11.003
meters in height (Ivanov et al., 1998). MVs are frequently reported as
mud diapirs, mud pies, mud cones, or mud lumps (e.g. Henry et al.,
1990; Le Pichon et al., 1990; Ginsburg and Soloviev, 1994; Ivanov et
al., 1996; Vogt et al., 1999; Kopf, 2002; Hovland et al., 2005). Mud
volcanoes have also been documented in caldera structures up to
8 km in diameter (Ivanov et al., 1996; Woodside et al., 1997; Dupré
et al., 2008).
In the Eastern Mediterranean Sea, mud volcanoes are manifestations of incipient plate convergence and are more prevalent than on
other accretionary margins. They were first reported in the Eastern
Mediterranean by Cita et al. (1981), who identified the “Prometheus
dome” close to the crest of the western Mediterranean Ridge. After
that pioneering work, the so called “Mediterranean Ridge Mud
Diapiric Belt” (Limonov et al., 1996), was extensively investigated
(Ryan et al., 1982; Cita et al., 1989; Camerlenghi, 1991; Camerlenghi
et al., 1992; Cita and Camerlenghi, 1992; Cusin et al., 1992; Staffini
et al., 1993; Cita et al., 1996a, b), and high resolution geophysical
data demonstrated a strong interplay between fluid outflow and
tectonics within the deformed wedge.
The Calabrian Arc in the Ionian Sea has been less intensively investigated than the Mediterranean Ridge. The original evidence of allochthonous material emplacement was reported by Rossi and Sartori
(1981) and Barbieri et al. (1982) whose identified debris flow and
G. Panieri et al. / Marine Geology 336 (2013) 84–98
slump deposits, and proposed the terms “polygenic chaotic deposits”
and “chaotic units” for these lithological facies. Based on their assumptions, such lithologies could only result from frontal mass
waste flows accompanied and/or followed by under-thrusting of
none-consolidated sediments. The possibility of mud volcanoes
within the inner accretionary prism of the Calabrian Arc was
suggested by Fusi and Kenyon (1996) and Sartori (2003). Recently,
using seismic reflection and sedimentary data, the existence of two
mud volcanoes, Madonna dello Ionio and Pythagoras, was confirmed
(Praeg et al., 2009). These Authors' data showed a strong link between mud volcano eruptions and the critical reorganization of the
accretionary complex during the Middle Pliocene. Such tectonic
rearrangements caused changes in the stress field resulting in the
formation of a regional unconformity due to a widespread compressions along the Calabrian Arc (Capraro et al., 2006 and references
therein).
The aim of this paper is to contribute to our knowledge of the relationships among mud volcanism, fluid flow and tectonics through
the interpretation of old and newly acquired geophysical data, integrated with the analysis of well targeted sediment cores along the
inner deformation front of the Calabrian Arc.
2. Regional setting
The Calabrian Arc (Fig. 1) develops along the Africa/Eurasia plate
boundary in the Ionian Sea (Eastern Mediterranean Sea) and is part
85
of the eastward migrating Apennine subduction system connecting
the NW trending Apennine with the EW oriented Maghrebian thrust
belt (Patacca and Scandone, 2004). The Calabrian Arc is located above
a NW dipping subduction system, characterized by an active volcanic
arc (the Aeolian Islands) and a well-defined Wadati–Benioff zone
(Wortel and Spakman, 2000), with earthquakes descending to nearly
500 km depth. Africa/Eurasia convergence occurs in this region at a
very slow rate (5 mm/yr or even b 5 mm/y), as reported by recent
GPS studies (Calais et al., 2003; Reilinger et al., 2006; Serpelloni et
al., 2007; D'Agostino et al., 2008; Devoti et al., 2008).
The external part of the Arc (Fig. 1) is represented by a 300 km wide
subduction complex bounded to the south by the outer deformation
front and bordered laterally by two major structural features, the
Malta escarpment to the southwest and the Apulia escarpment to the
northeast. The Calabrian Arc subduction complex displays a well developed accretionary wedge, multiple slope sedimentary basins and a seaward dipping metamorphic basement, with tectonic units belonging to
the Apenninic–Maghrebian prism and a Mesozoic to Miocene relatively
undeformed thinned continental block (Artoni et al., 2008). The northwestward thickening accretionary wedge (Finetti, 1982; Cernobori et
al., 1996; Finetti, 2005) is segmented along strike in different structural
domains characterized by different rheologies and deformation styles
(Polonia et al., 2011). Four main morpho-structural domains were identified in the subduction complex: 1) the post-Messinian accretionary
wedge; 2) a slope terrace; 3) the pre-Messinian accretionary wedge,
and 4) the inner plateau. Variation of structural style and seafloor
Fig. 1. Structural map of the Calabrian Arc region superposed over a gray level bathymetric slope map, modified from Polonia et al. (2011). Slip vector in the African reference frame
is indicated by a red arrow. Eu: Europe, Afr: Africa. Multibeam bathimetry provided by the CIESM/Ifremer Medimap group (Loubrieu et al., 2008). Major structural boundaries,
active faults and the extent of the structural domains (i.e. pre and post-Messinian wedges and inner plateau) are indicated. The location of the seismic profiles shown in Fig. 2 is
indicated. The black box represents the study region shown in Fig. 3c. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of
this article.)
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G. Panieri et al. / Marine Geology 336 (2013) 84–98
Fig. 2. a: line drawing of pre-stack depth migrated 36 fold MCS line CROP M-4. Deformation is related to an imbricate fan within the post-Messinian salt-bearing accretionary wedge (yellow domain), out-of-sequence thrust faults in the
pre-Messinian wedge (green domain) and normal faults in the Inner plateau (gray domain). b: Sparker seismic profile J-08 across the continental margin. The rather flat inner plateau is bounded towards the south by the rough morphology
of the inner accretionary wedge. Correlation between seismic and borehole data allow to identify and date main seismostratigraphic units. Location of seismic profile is shown in Fig. 1. (For interpretation of the references to color in this
figure legend, the reader is referred to the web version of this article.)
G. Panieri et al. / Marine Geology 336 (2013) 84–98
morphology in these domains is related to different tectonic processes,
such as frontal accretion, out-of-sequence thrusting, underplating and
complex faulting and also to the very different rehologies of the involved sediments.
The very low tapered (taper angle about 1.5°) outermost accretionary wedge is a salt bearing complex emplaced during and after
the Messinian salinity crisis (Figs. 1 and 2). Frontal accretion is active
in this region on a shallow basal detachment located at the base of the
evaporites. At the rear of the post-Messinian accretionary complex
the Inner wedge is formed by pre-Messinian clastic sediments. The
basal detachment in this domain is located on top of the Cretaceous
sediments and/or on the basement. Moving inwards (towards NW)
the inner wedge is bounded by an inner deformation front (Splay-3
fault system, Calabria Escarpment, in Fig. 1), that represents the
transition from the highly deformed accretionary wedge to a more
stable inner plateau characterized by complex normal and strike slip
faulting. The inner plateau hosts chaotic units (Rossi and Sartori,
1981) and mud volcanoes (Praeg et al., 2009); normal faults control
strike margin segmentation and forearc basin formation (i.e. Squillace
basin), dewatering and fluid/mud/salt upward migration (Polonia et
al., 2011; Capozzi et al., 2012).
3. Material and methods
3.1. Geophysical data
We reconstructed the regional architecture of the accretionary
complex from MCS data (the CNR-ENI Deep Crust Seismic Profiles —
CROP and Mediterranean Sea — MS datasets) acquired during the
1970s and 1990s and re-processed at the Marine Geodynamics Department of the IFM-GEOMAR (Kiel, DE) to obtain full pre-stack
depth-migrated (PSDM) seismic sections (Fig. 2a).
The fine structure of key morphotectonic domains was analyzed
through single-channel SPARKER seismic data (Fig. 2b) acquired by
IGM (now ISMAR-Bologna, IT) in the Ionian Sea during the 1970s
(Rossi and Sartori, 1981). These data, available only in hardcopies,
were digitized, processed and geo-referenced using the open-source
software Seisprho (Gasperini and Stanghellini, 2009).
Morphobathymetric data provided by the CIESM/Ifremer Medimap
group (Loubrieu et al., 2008), have been used to map active
faults and to address relationships between first order tectonic
features visible on seismic profiles and small scale morphotectonic features. For more details on data acquisition and processing see Polonia et
al. (2011).
87
Core CALA 21 was investigated taking advantage of new, nondestructive, analytical techniques, while the other two cores were
re-described and re-sampled to carry out additional analyses.
3.2.1. Sedimentological and compositional analyses
Core CALA 21 was visually described and scanned for magnetic
susceptibility using a point sensor with measurements at 1 cm spacing. Whole-core magnetic susceptibility was measured using a point
sensor with measurements at 1 cm spacing using a Bartington MS2
meter (resolution 2 × 10 −6 SI units) coupled with an MS2C loop
sensor.
The core was sampled every 10 cm for grain size using a CoulterCounter Laser Beckman LS-230, on the 0.04–2000 μm fraction at
0.004 μm resolution. The results were classified according to Friedman
and Sanders (1978) grain-size scale.
High resolution digital photographs, sediment color scan, and
chemical composition were determined on core CALA 21 by means
of an Avaatech XRF-core scan using the 50 kV instrumental setting
to measure the Al, Si, K, Ca, Ti, and Fe contents. The results were normalized to the titanium (Ti) detrital phase. Additional analyses were
carried out on the clean sand fraction of selected gold sputtered samples of CALA 21 using Philips (NL) 5015b EDX DX4 Scanning Electron
Miscroscope (SEM) coupled with an Energy Dispersive Spectroscopy
(EDX).
3.2.2. Micropaleontological investigation
Nannofossil assemblages were analyzed in smear slides with a polarizing light microscope at 1250 × magnification on 21 samples from
the core CALA 21 collected from different lithologic types. Smear
slides were prepared directly from the sediment samples. The abundance of nannofossils was estimated relative to the other biogenic
particles and inorganic components (see details in the Appendix A
data).
The three investigated cores were sampled every 10 cm for foraminiferal analyses; at some levels sampling was more closely spaced.
Planktonic and benthic foraminifera were analyzed on 26 samples
from core BS81/II 5, 20 samples from core BS81/II 10, and 83 samples
on core CALA 21. For foraminiferal analyses samples were dried for
24–48 h at 50 °C; then weighed, soaked in distilled water and wet
sieved with mesh widths of 63 μm. Residues were dried again at
50 °C. The foraminiferal species were identified and semi-quantified
in the sediment fraction >63 μm. Micropaleontological investigations
were aimed at obtaining a chronostratigraphy by identifying displaced
species indicative of extruding deep-seated formations. All samples
were stored at ISMAR-CNR in Bologna (IT). Planktonic foraminifera
were identified largely following the taxonomy of Hembleben et al.
(1989); benthic foraminifera following Loeblich and Tappan (1987).
3.2. Geological data
This investigation was carried out on three sediment cores
(Table 1): core CALA 21, acquired during cruise CALAMARE with
R7V Urania from the summit of a topographic high of the inner accretionary wedge during (Fig. 2), and gravity cores 5 BS81/II and 10
BS81/II, collected in 1981 from a topographic high imaged on Sparker
line J-22 (Fig. 3) initially studied by Barbieri et al. (1982) and Morlotti
et al. (1982).
Table 1
Reference data for the sediment cores used for this study.
Core
Latitude N
Longitude E
Water depth
(m)
Length
(m)
5 BS 81/II
10 BS 81/II
CALA 21
38°12.2′
38°12.2′
38°24′ 59″
17°36.1′
17°35.4′
17°55′ 40″
1836
1888
2396
315
293
533
3.2.3. Organic carbon
Variations in organic carbon content on whole mud samples in intervals with different sediment colors of core CALA21 were measured
using a Fison CHN Elemental Analyzer at ISMAR-CNR in Bologna (IT).
Prior to measurement samples were treated with 2 N HCl to eliminate
the carbonate fraction. The error in these determinations is ± 1% of
the value.
3.2.4. Stable isotopes
Oxygen and carbon stable isotope analyses (δ18O and δ13C) were
carried out on selected clasts recovered in cores BS81/II 5 and BS81/II
10 as well as on bulk sediments from intervals of core CALA 21 characterized by anomalous sediment disturbance presumably caused by fluid
migration. These analyses were carried out on 10 μg samples with a
ThermoFinnigan MAT252 mass spectrometer coupled with CarboKielII carbonate preparation device at the Serveis Cientifico-Tècnics of the
University of Barcelona (ES). Analytical precision was estimated to be
better than 0.08‰ for δ18O and 0.03‰ for δ13C by measuring the
88
G. Panieri et al. / Marine Geology 336 (2013) 84–98
Fig. 3. a: segment of Sparker seismic profile J-22 parallel to the Calabrian continental margin (see Fig. 1 for location) across the transition between the inner plateau and the inner
accretionary wedge. The boundary between these two structural domains corresponds to the splay-3 fault system. The three studied gravity cores are located at the footwall and
hangingwall of this major tectonic feature. b: zoom of the seismic line across the mud volcano. c: contour bathymetric map of the study area superimposed on the slope map of the
multibeam data (isolines every 200 m). The cores shown in this work (5 BS81/II, 10 BS81/II and CALA21) are represented by the red dots, while the yellow line is the sparker profile
J-22. In red the inner deformation (splay-3 fault system) of the subduction system that marks the transition between the rather flat inner plateau and the inner accretionary wedge
which is characterized by a very rough topography related to a NE–SW trending ridges and troughs. (For interpretation of the references to color in this figure legend, the reader is
referred to the web version of this article.)
standard NBS-19. Isotope results are reported in standard delta notation
relative to Vienna Peedee Belemnite (V-PDB).
4. Results
4.1. Seismic data
CROP MCS seismic line M-4 (Fig. 2a) was acquired orthogonal to
the main structural trends of the subduction complex (Fig. 1). In the
outer domains (from s.p. 100 to s.p. 240), the basal detachment is located at the base of the evaporites while moving inwards (from s.p.
240 to s.p. 800) the detachment cuts through progressively deeper
levels down to the basement and progressively thicker sediment
packages are involved in deformation. At the rear of the postMessinian salt bearing accretionary wedge a series of landward dipping out-of-sequence thrust faults named splay-faults (Splay-1,
Splay-2, Splay-3) are active (Polonia et al., 2011). Splay-3 is marked
by a major topographic scarp (“Calabria Escarpment”) with about
600–700 m offset. To the South of the Calabria Escarpment, the seafloor
has a very rough topography related to high amplitude, large wavelength folds that produce km-scale sedimentary basins (“intermediate
depressions” of Rossi and Sartori, 1981). Landward of the Calabria
Escarpment, a less deformed and rather flat terrace is present (Inner
plateau). Here, seaward and landward dipping normal faults contribute
to the development of multiple slope basins separated by structural
highs. The Inner plateau is bounded towards NNW by the Squillace
forearc basin that is a NNW–SSE trending forearc basin (Figs. 1 and 2a)
filled by a 5 km thick sedimentary section.
The upper structure of the Inner Plateau, imaged in Sparker seismic
line J-08 (Fig. 2b), is characterized by a rather flat area dipping slightly
towards SE, with large wavelength (50 km) seafloor undulations. A
thick section (about 1 s TWT) of Plio-Quaternary sediments is present
below the terrace overlying Messinian deposits. Sediments appear to
be folded and locally disrupted along sub-vertical deformation zones
that bound acoustically transparent sedimentary units (fix 83 and 84)
corresponding on the seafloor to small (about 1 km wide) subcircular, probably diapiric swells. The nature and composition of the
diapiric material (mud or evaporites) cannot be determined through
seismic data. Another mound is present immediately SE of fix 70 and
close to the sub-vertical fault at fix 71 (Fig. 2b). Its geometry and location suggests that it was formed by the rising of fluid, since it develops
in a region where the Messinian salt or gypsum are absent. Diapiric processes observed in this region appear to be related to transtensive faults
segmenting the continental margin (Del Ben et al., 2008), similar to
those controlling the development of the Squillace Basin (Capozzi et
al., 2012).
Seismic profile J-22 (Fig. 3), collected in the inner Calabrian Arc, is
orthogonal to the previous profiles and crosses obliquely the transition between the inner plateau and the inner wedge represented by
the seaward dipping, about 4° steep topographic scarp (Calabrian
Escarpment) between pings 105 and 109 (Fig. 3). At the toe of the
Calabrian escarpment, a 4 km wide swell (0.5 s TWT, about 370 m
above the surroundings) is present between pings 113 and 116
G. Panieri et al. / Marine Geology 336 (2013) 84–98
89
90
G. Panieri et al. / Marine Geology 336 (2013) 84–98
(Fig. 3). On the crest of this feature we collected gravity core CALA 21.
To the NW, North of the Calabrian escarpment, the rather flat inner
plateau shows short wavelength undulations and depressions possibly related to normal faults (see for example s.p. 100). A small swell
10–15 km North of the escarpment characterized by a transparent
acoustic facies is less prominent and characterized by two peripheral
troughs. Cores BS81/II 5 and BS81/II 10, collected on top of this feature (Barbieri et al., 1982), were re-analyzed in the frame of the
newly acquired dataset.
Table 2
Control points used in the definition of the age-depth model of core CALA 21 (°foraminifera;
# nannofossils). * For the base and top of sapropel S1 interval we adopt radiometric ages
published by Vigliotti et al. (2011) from the same investigated area.
Depth in core Control point
CALA 21 (cm)
Calibrated
Source
age B.P. (ky)
33
° 3/2 ecozone boundary
4
57.5
° 4/3 ecozone boundary
and top sapropel S1*
° 5/4 ecozone boundary
and base sapropel S1*
° 6/5 ecozone boundary
° 7/6 ecozone boundary
° 8/7 ecozone boundary
° 9/8 ecozone boundary
° bMIS 4/MIS 3 transition
# Emiliana huxley acme zone
5.7
101
4.2. Sediment core description, physical properties and composition
Detailed descriptions of sediment cores BS81/II 5 and BS81/II 10 are
reported in Barbieri et al. (1982) and Morlotti et al. (1982). Here we report the identification of the mud breccia facies according to the classification of Staffini et al. (1993) and Cita et al. (1996a). The upper parts of
gravity cores BS81/II 5 and BS81/II 10 contain an undisturbed sequence
of hemipelagic upper Pleistocene–Holocene sediments containing
Sapropel S1 and a fine-grained tephra layer (Fig. 4) identified as tephra
Z-1 and dated 3300 yr B.P. by Keller et al. (1978). The lowermost part of
both cores contains a pebbly mudstone composed of hetero dimensional
and polygenic litho-fragments (Table 3) chaotically distributed in a stiff
clayey matrix formed by greenish-gray clay that include microclasts
(from mm to microns) of different lithologies. The pebbles, mainly
sub-rounded with size ranging from 0.5 to 8 cm, have different lithologies including: fossiliferous micrites, micrites apparently barren of fossils, calcareous mudstones, siltstones and fine laminated
sandstones. The pebble concentration decreases upwards into the
chaotic deposit (Fig. 4). Following Cita et al. (1996a), we correlate
the pebbly mudstone described in cores BS81/II 5 and BS81/II 10
with mud breccia facies A1 (Massive, coarse grained) and A2 (Massive,
medium grained).
The upper 150 cm of core CALA 21 consists of yellowish bioturbated
hemipelagic sediments interbedded with cm-thick, fine-grained turbidites and tephra with high magnetic susceptibility values (Figs. 4 and
5). A 40 cm thick black interval in the uppermost sequence was identified as Holocene Sapropel S1, whereas the 5 cm-thick tephra layer recovered above Sapropel S1 was correlated to tephra Z-1 as in the
cores BS81/II 5 and BS81/II 10 (Fig. 4). The sedimentary interval between 150 and 284 cm is made of brownish bioturbated sediments
with several, few mm-thick, terrigenous turbidites, containing abundant quartz, rock fragments, and rare shallow water benthic foraminifera. The upper sequence contains also two minor tephra of unknown
origin. The sequence below 284 cm is characterized by silty-clay bulk
sediments containing irregularly clustered intervals of differently colored sediments (from dark gray to olive gray sediment clouds and
light gray to gray matrix) with several fragmented and vertically
dislocated thin sandy/silty turbidites and volcanoclastic layers (Fig. 6).
Visual logging and radiographs (Fig. 5) reveal no bioturbation. The sediments contain several vertical or sub-vertical sandy/silty micro-pipes
suggesting sediment reworking by fluid migration (Fig. 6). Following
Staffini et al. (1993) and Cita et al. (1996a), we assigned this sediment
facies to the mud breccia facies B3 (patchy/cloudy).
The presence of the mud breccia patchy/cloudy facies in the core is
outlined by an abrupt color change (color indexes a, b, and lightness)
and magnetic susceptibility whereas the grain size trend and the
chemical composition of the sediments do not show diagnostic
changes (Fig. 5). The sand fraction of the mud breccia patchy/cloudy
facies is characterized by abundant pyrite occurring as aggregates
cubic, octahedral and pentagon-dodecahedral microcrystals forming
framboids and sometimes framboidal aggregates, as well as replacing
134
158
188
234
533
533
10.4
11.5
12.65
14.8
21.8
b60
b63–84
Capotondi et al. (1999),
Sprovieri et al. (2003)
Sprovieri et al. (2003),
Vigliotti et al. (2011)
Sprovieri et al. (2003),
Vigliotti et al. (2011)
Sprovieri et al. (2003)
Sprovieri et al. (2003)
Sprovieri et al. (2003)
Sprovieri et al. (2003)
Budillon et al. (2009)
Raffi et al. (2006)
of foraminifera carbonates tests. Authigenic minerals including Iron
oxides and glauconites are also present. At 432 cm high reflectivity
aggregates were identified in the radiographs and analyzed with a
coupled EDX/electron microscope (Figs. 5 and 6). We sampled within
the aggregates a centimetric clast whose shape and morphology resemble a cylindrical pipe-like chimney (Fig. 6). EDX analysis indicates that
this structure contains barite and pyrite on the outer and inner surfaces,
respectively. Accessory minerals accompanying these major phases include calcite, quartz, feldspars, and phyllosillicates.
4.3. Micropaleontological investigation
4.3.1. Nannofossils
In CALA 21 calcareous nannofossils are generally abundant and
show moderate to good preservation (Table in Appendix A). Samples
were collected in key layers with different sediment color, texture
and grain size to check if these variations are related to different sedimentary input. Emiliania huxleyi is abundant from the top to the
base of the core (see Table in the Appendix A). Reworking of
nannofossils and abundant calcareous clasts were observed from
234 to 533 cm (Fig. 4). In general almost all the samples show
reworked Plio-Pleistocene species such as large Reticulofenestrae together with Helicosphaera sellii, Sphenolithus spp., Pseudoemiliania
lacunosa, and five rays Discoaster. Late Cretaceous to Tertiary (mainly
Eocene–Oligocene) taxa are present especially from 434 to 320 cm
and very old reworked nannofossils show abundances exceeding
30% of the total of counted coccoliths. A single sample (411 cm)
does not show reworked elements, therefore evidencing that the deposition of this layer was due to biogenic sedimentation. A high content of pyrite has been observed from 443 to 433 cm.
4.3.2. Foraminiferal assemblages
Cores 5 BS81/II and 10 BS81/II were examined for foraminiferal
content both in the muddy sediments and in the clasts. All samples
contained scarce and poorly preserved microfauna; only very few
samples were rich in foraminifera and allowed a stratigraphic assignment. The chaotic deposits (from 315 to 145 cm in 5 BS81/II
and from 293 to 153 cm in 10 BS81/II) contain foraminiferal species
dating back to Cretaceous confirming previous observations made
by Barbieri et al. (1982) and Morlotti et al. (1982) even if in some
cases the clasts were completely barren of indicative microfauna.
Fig. 4. Lithological log, investigated samples, stratigraphy and description of the microfaunal assemblages (planktonic and benthic foraminifera and calcareous nannoplankton) of
cores 5 BS81/II and 10 BS81/II (see for more details Morlotti et al., 1982), and core CALA 21 (this paper). Magnetic susceptibility has been reported to highlight the abrupt change at
the passage between hemipelagic mud and mud breccia patchy/cloudy facies.
G. Panieri et al. / Marine Geology 336 (2013) 84–98
91
Table 3
Clasts of mud breccia (facies A1 massive, coarse grained and A2 massive, medium grained, according to Cita et al., 1996a) found in cores 5 BS81/II and 10 BS81/II. Lithology and
stable carbon and oxygen isotope values for clasts are indicated.
Mud breccia
(scale bar 1 cm)
Sample
Core
cm in the core
(bsf)
Lithologies
6
5 BS81/II
195
Fossiliferous micrite, light gray, firm, massive, angular
10
5 BS81/II
221
14
5 BS81/II
23
δ13C
(%0PDB)
δ18O
(%0PDB)
1.01
−0.14
Calcareous mudstone, gray, firm, rounded
−1.26
−1.64
225
Calcareous mudstone, light gray, firm, massive, abundant mica, rounded
−0.32
−2.65
5 BS81/II
243
Fossiliferous micrite, light gray, firm, massive, rounded
0.27
−1.40
25
5 BS81/II
275
calcareous mudstone, light gray, firm, massive, with calcite veins
0.03
−3.85
3
10 BS81/II
279
Calcareous mudstone, light gray, firm, massive, angular
−0.23
−1.45
31
5 BS81/II
288
Calcareous mudstone, light gray, firm, massive, rounded
−0.74
−0.28
20
10 BS81/II
220
Calcareous mudstone, dark gray, firm, planar laminated, altered surface
−0.81
−0.42
9
10 BS81/II
254
Calcareous mudstone, dark gray, firm, planar laminated, with calcite
veins, altered surface
−0.41
−3.18
36
10 BS81/II
216
Calcareous mudstone, gray, firm, rounded
−0.03
0.37
52
10 BS81/II
278
Calcareous mudstone, gray, firm, massive, angular
0.67
−0.28
53
10 BS81/II
284
Calcareous mudstone, gray, firm, massive, angular
−0.36
−0.58
92
G. Panieri et al. / Marine Geology 336 (2013) 84–98
Fig. 5. X-ray, photograph, graphic lithology, magnetic susceptibility, grain size, chemical composition, and colors indexes of the core CALA 21. Green boxes: pictures in Fig. 6.
The cores yielded foraminiferal species from middle Eocene
(Morozovella spinulosa), Oligocene (Globorotalia opima opima),
Early and Middle Miocene, Early Pliocene (Globorotalia margaritae,
Globorotalia punticulata), Late Pliocene (Globorotalia crassaformis,
Globorotalia inflata), and Pleistocene formations (Globigerinoides
ruber, Globorotalia truncatulinoides, Neogloboquadrina dutertrei).
Benthic foraminifera are represented by Cassidulina, Gyroidinoides,
Cibicidoides, Quinqueloculina, Miliolinella, Nonionella, Bulimina, Brizalina,
Melonis, Fissurina and Uvigerina. Both cores exhibited abundant
Gyroidinoides laevigatus and Glomospira charoides at the top whereas
down core the matrix of the chaotic sequence is dominated by
Cassidulina laevigata, Cibicidoies pachyderma, Articulina tubulosa, and
miliolids. Some species belonging to Stilostomella abundant in the late
Miocene and rare specimens of Bolivina fastigia were observed between
290 and 203 cm in core 10 BS81/II; both are rare in chaotic deposits of
core 5 BS81/II.
Samples from CALA21 yielded rich microfaunas, the majority belonging to fossil planktonic taxa, with minor benthic components.
Planktonic foraminifera are abundant throughout the core. They consist of: Globigerinoides ruber (alba and rosea variety), Globigerinoides
sacculifer, Orbulina universa, Globigerinella aequilateralis, Globigerina
calida, Globigerina bulloides, Globigerinita glutinata, Neogloboquadrina
pachyderma, Neogloboquadrina dutertrei, Turborotalia quinqueloba,
Globorotalia inflata, Globorotalia scitula and Globorotalia truncatulinoides
(Fig. 4). The majority of benthic foraminifera can be considered
autochthonous, are quite abundant and belong to the taxa: Cassidulina
(C. laevigata and C. crassa) Quinqueloculina (Q. lamarkiana, Q. longirostra,
Q. oblonga, Q. seminulum), Miliolinella (M. irregularis, M. subrotunda),
Sigmoilinita tenuis, Nonionella (N. opima, N. turgida), Bulimina
(B. marginata, B. inflata), Brizalina (B. alata, B. dilatata, B. spathulata),
Gyroidinoides laevigatus, Melonis barleeanum, and Uvigerina peregrina;
all are consistent with the depth range of the core, with the chronostratigraphic framework and the paleoenvironment.
In general, the preservation of the microfossils is rather variable,
from poor to excellent, due to diagenetic alteration and/or transport.
While from the top of the core to 284 cm the preservation of foraminifera is excellent, from 284 down core the assemblages specimens
show different degrees of tests preservation: in many cases we
observed broken specimens and/or taxa filled by CaCO3 and pyrite.
In some samples (at 278 cm, at 290 cm, from 333 to 353 cm, and
from 483 to 520 cm) both planktonic and benthic foraminifera had
pyritized tests and/or pyrite overgrowth on tests.
4.4. Stable isotopes
The carbon and oxygen isotopic composition of analyzed mud
breccia samples in cores 5 BS81/II and 10 BS81/II are shown in
Table 3. The δ 18O values display a higher scattering than the δ 13C
G. Panieri et al. / Marine Geology 336 (2013) 84–98
93
Fig. 6. Details of mud breccia patchy/cloudy facies (facies B3 according to Staffini et al., 1993; Cita et al., 1996a) in CALA 21 at different stratigraphic intervals (blue boxes showed in
Fig. 4). Dotted line indicates vertical migration structures. Disrupted tephra/terrigenous sandy layers and micro-pipes filled with silt/fine sand transported by fluid escape are evident. b) Nodule with cylindrical pipe-like chimney shape selected from a concentration of nodules (black circle in a) identified visually and in the X-ray radiography. SEM micrograph (c) shows the composition of the nodule by EDX analyses, barite and pyrite on the outer and inner surfaces respectively. Pyrite occurs as aggregated spheroids constructed of
numerous cubic pyrite crystals and barite in euhedral crystals. e′) cartoon showing the reconstruction of mud breccia patchy/cloudy facies where mud bulk samples collected for
isotopic analyses (e″) are indicated.
values. Measurements from clasts from core 5 BS81/II yielded δ 13C
from 1.01 to − 1.3‰ and δ 18O values from − 0.1 to − 3.8‰, whereas
clasts from core 10 BS81/II exhibited δ 13C values from 0.67 to − 0.8‰
and δ 18O from − 0.4 to − 3.2‰. Bulk muddy sediment samples recovered from the patchy/cloudy mud-breccia facies of CALA 21 were selected in layers from 375 and 385 where color and texture changes
marked the different clouds of the mud breccia patchy/cloudy facies
as shown in Fig. 6. The sampling strategy aimed at verifying if different isotopic signatures characterize the different clouds of this facies.
Isotopic analyses indicate a variation of the δ 13C values (from − 0.3 to
− 0.4‰) and δ 18O (from −1 to 0.6‰).
5. Discussion
5.1. Biostratigraphy
The biostratigraphic scheme of core 5 BS81/II and10 BS81/II previously published by Morlotti et al. (1982) has been confirmed here
placing the sediment cores in the MNN 21b (Emiliania huxleyi acme)
zone in the Upper Pleistocene–Holocene.
The biostratigraphic scheme for core CALA 21 is based on calcareous nannofossils and foraminifera assemblages (Table 2). Calcareous
nannofossils show Emiliania huxleyi dominating the assemblage
from the base to the top of the core placing the sedimentary succession within the MNN 21b zone (E. huxleyi acme) of Rio et al. (1990).
Emiliania huxleyi acme zone (MNN 21 b) starts at ~ 85 ka in tropical
and subtropical waters (Thierstein et al., 1977) and according to
Raffi et al. (2006) the age of its base varies from 82 to 63 ky.
Concerning planktonic foraminifera, we used the main microfaunal
bioevents in agreement with the eco-biostratigraphic schemes used
for the Mediterranean Late Quaternary time subdivision (Asioli et al.,
1999; Capotondi et al., 1999; Sbaffi et al., 2001; Sprovieri et al., 2003;
Ducassou et al., 2007; Geraga et al., 2008; Budillon et al., 2009). In this
work we adopted the ecobiostratigraphic guidelines proposed by
Capotondi et al. (1999) and Sprovieri et al. (2003) for the last 23 ky
and Budillon et al. (2009) for the lower intervals. Table 2 shows all
the control points defined in the core and their assigned ages. In detail,
cold water species Globigerina bulloides, Neogloboquadrina pachyderma,
Neogloboquadrina dutertrei, Globorotalia scitula and Turborotalia
quinqueloba dominate the planktonic foraminifera assemblage at
the base of the core (533–234 cm), and together with the low
abundance of Globigerinoides ruber gr. confirm that the faunal content
of MIS 3 is consistent with Budillon et al. (2009). Between 234 and
188 cm the dominance of T. quinqueloba and N. pachyderma, together
with the occurrence of G. scitula and the absence of Globorotalia inflata
identifies the ecozone 8 F of Sprovieri et al. (2003) and Budillon et al.
(2009). Upward, a series of bioevents are related to the ecozones of
Sprovieri et al. (2003); at 188 cm the frequency increase of G. ruber
gr. and G. inflata marks the ecozone boundary 8 F/7 F; the interval between 158 and 134 cm characterized by the absence of G. ruber gr.
and the abundance of N. pachyderma and T. quinqueloba coincides
with the ecozone 6 F; at 134 cm the concomitant increase of G. ruber
gr. and Globorotalia truncatulinoides with the presence of G. inflata and
94
G. Panieri et al. / Marine Geology 336 (2013) 84–98
the low abundance of N. pachyderma and T. quinqueloba allow the recognition of ecozone 5 F and the beginning of the Holocene.
The high frequency of Globigerinoides ruber, Globigerinella
aequilateralis, Globigerina calida, and Orbulina universa between
101 and 57.5 cm identifies ecozone 4 F that corresponds to the sapropel
S1 deposition interval, in agreement with the lithology and the geochemical parameters. Finally, the occurrence of Neogloboquadrina
pachyderma, Globorotalia inflata and Globorotalia truncatulinoides correlates the interval between 57.5 and 33 cm with the ecozone 3 F, and the
Globigerinoides sacculifer increase at 33 cm marks the zonal boundary
3 F/2 F.
Table 4
Organic carbon analyses on selected samples from CALA 21.
Depth in core CALA21
(cm)
%OC
%Ctot
%Cinorg
251.5
269
273
275
280
283.5
286
304
0.21
0.52
0.23
0.23
0.24
0.23
0.25
0.25
4.26
4.02
3.57
4.01
3.82
3.36
3.68
3.60
4.05
3.50
3.35
3.78
3.58
3.13
3.44
3.35
5.2. Micropalentology and mud volcanism
Micropaleontological analysis in mud extrusion provinces is useful
in assessing the migration of fluids providing the age of the source sediments thanks to fossils that may indicate mixing of different stratigraphic formations involved in mud volcanisms, and, ultimately, the
timing of extrusive events. The state of preservation of tests of foraminiferal assemblages in the massive and patchy/cloudy mud breccia in
the cores shows planktonic and benthic specimens with pristine tests
together with tests with different color and abraded/polished appearance, and with pyritized tests sometimes exhibiting abundant calcite
in sutures. It has been previously observed that fluid emission sites
are dynamic environments where the remobilization due to fluid activity could resuspend, mix and redeposit sediments and foramineral tests
(Panieri et al., 2009).
The age of source sediments of the mud breccia in cores BS81/II 5
and BS81/II 10 obtained from microfossils is consistent with derivation from different deeper stratigraphic units. While the planktonic and benthic foraminifera together with calcareous nannofossils
(Morlotti et al., 1982), indicate that the matrix of the mud breccia includes Early Pliocene–Pleistocene sediments; on the contrary pebbles
and clasts indicate extrusion from older units from Cretaceous to Late
Miocene.
In the patchy/cloudy mud breccia of core CALA 21 no reworked foraminifera from older formations were observed, whereas calcareous
nannofossils reveal abundant reworking of Cretaceous to Tertiary
(mainly Eocene–Oligocene) formations in some levels (Fig. 4 and
Table in the Appendix A).
5.3. Sedimentary facies, composition and stable isotope geochemistry
The sedimentary facies of the studied cores suggest different dynamics of sediment extrusion in Calabrian Arc mud volcanoes.
The newly collected data suggest that the matrix-supported
diamicton recovered in cores BS81/II 5and BS81/II 10 are manifestations of extruding deep-seated clay-rich formation probably linked
to tectonic stresses within the accretionary prism. The previous hypothesis of Morlotti et al. (1982) considered an external provenance
of the materials related to tectonic chaoticization of the sediments
flooring the Ionian bathyal plain (Rossi and Sartori, 1981). Here we
suggest that the mud breccia with centimetric to pluricentrimetric
unsorted clasts observed in cores 5 BS81/II and 10 BS81/II represent
the “massive” type A1 and A2 according to the mud-breccia facies
classification of Staffini et al. (1993) and Cita et al. (1996a), indicative
of sediment mobilization from deeper stratigraphic intervals. Stable
isotope analyses on the clasts of cores 5 BS81/II and 10 BS81/II
(Table 4) suggest a common source, since all samples show narrow
isotopic ranges.
The organized type B3 patchy/cloudy mud-breccia facies in core
CALA21 characterized by differently colored patches and clouds represent a sediment disturbance caused by fluid expulsion. The absence
of bioturbation in both visual logging and radiographs and the presence of vertical sandy/silty micro-pipes and fragmented/vertically
dislocated sandy layers (either turbidites and tephras) (Fig. 6)
support the hypothesis of sediment disturbance caused by fluid activity. This seems to be confirmed by the geochemical analyses
performed on the bulk sediment collected in the patchy/cloudy facies,
and also by the occurrence of abundant reworked calcareous
nannofossils. The stable isotope values obtained from the mud recovered below and above the patchy/cloudy mud-breccia facies (Fig. 6)
and representing the local normal sedimentation, are positive in
δ 18O and negative in δ 13C whereas the three differently colored sediment patches show anomalously more negative δ 18O and more positive δ 13C values. Carbonate precipitated in the presence of seepage
generally exhibit negative δ 13C and more positive δ 18O. Similarly,
Peckmann et al. (2003) found lower δ 18O and higher in δ 13C in Late
Eocene methane-seep deposits and concluded that ongoing micrite
formation after the cessation of the seepage during increased burial
might have altered the isotopic composition of the microcrystalline
carbonates toward lower δ 18O and higher δ 13C. Higher δ 13C values
have been also reported for Oxfordian (Gaillard et al., 1992;
Peckmann et al., 1999), and Oligocene (Peckmann et al., 2002)
seep carbonates. In addition, positive δ13C values indicate hydrocarbon
formation rather than oxidation. This results from methanogenic archaea producing a 13C enrichment in the CO2 pool (Irwin et al., 1977;
Boehme et al., 1996). Consequently, carbonates formed in the archaeal
methanogenesis zone exhibit high δ13C values. We conclude that the
differently colored mud patches formed by a process involving methane
formation.
The patchy/cloudy mud breccia facies in core CALA 21 is mainly
outlined by a sharp color change from brownish to grayish and by a
sharp drop of the magnetic susceptibility, whereas the grain size
and the chemical composition of the sediments do not present diagnostic changes. The two former parameters are related neither to
climatic variation (as the Pleistocene/Holocene boundary is located
at 137 cm), nor to a higher organic matter contents (as in the case
of the Sapropel S1 in the upper part of the core), because the brownish and grayish sediments present similar organic carbon content
(Table 4). We can also exclude a higher terrigenous input in the
gray facies, as the sediment chemical composition does not change
significantly (Fig. 5). Fluid migration across the gray facies may
have caused the formation of minerals with low magnetic susceptibility including the pyrite and barite of the patchy/cloudy facies of core
CALA 21.
The coexistence in the sediment of isotopic anomalies, aggregates
of pyrite and barite, and vertical migration structures including
micro-pipes in the patchy/cloudy mud breccia facies, are strong indications of local fluid remobilization.
5.4. Mineralogy of sediments affected by mud volcanism
Mineralogical analyses of the pipe-like nodule in CALA 21, part of an
accumulation of nodules identified by X-ray radiography, revealed the
presence of barite and pyrite (Fig. 6). Barite and pyrite have been
reported in cold methane and/or in hot hydrothermal vents, as well as
in up flow and discharge zones of present-day thermal springs. Barite
G. Panieri et al. / Marine Geology 336 (2013) 84–98
and pyrite are also diagenetic minerals, frequently associated with
authigenic carbonates from cold seeps. Barite precipitates within the
sediments in the sulfate/methane transition zone, i.e., at the boundary
between sulfate-rich and sulfate-depleted solutions (Fu et al., 1994;
Torres et al., 2003; Aloisi et al., 2004; Castellini et al., 2006). Comparing
our data with previous studies confirmed the presence of discharging
fluids in our areas. This is confirmed also by the high concentration of
framboidal and/or tubular pyrite, and pyritized foraminiferal shells observed in samples of CALA21. Pyrite and pyritized foraminiferal shells
have been found in diverse oxygen-deficient environments and in modern seepage sites (Stakes et al., 1999; Lobegeier and Sen Gupta, 2008).
95
features, and compares with Mediterranean Ridge mud volcanoes active for over 1 m.y. (Robertson and the Ocean Drilling Program, Leg
160, Shipboard Scientific Party, 1996; Robertson and Kopf, 1998;
Kopf, 2002).
We cannot exclude that the extrusive fluid emissions are still
active; however, the uppermost part of the sedimentary sequence
appears to be completely undisturbed, suggesting that the emission, if still active, is not focused along single (or a few) large conduits that could eventually give rise to a paroxisitic activity but
rather it is more diffused, and do not cause sediment reworking
and mixing in the Upper Pleistocene sediments of the investigated
cores.
5.5. Relationship between tectonics and mud volcanism
Mud diapiric processes, widespread in the inner plateau of the CA
subduction complex, appear to be related to major structural features,
such as the inner deformation front of the CA subduction complex
(s.p. 4000 in Fig. 3), at the transition from the inner plateau to the
inner accretionary wedge. This feature shows all the characteristics
of a transpressive fault accommodating strain partitioning at the contact between the highly deformed wedge and the continental basement. A similar setting is observed in the Mediterranean Ridge
accretionary complex, where strike-slip faults mark the contact between the accretionary wedge and the backstop (Chaumillon and
Mascle, 1997; Mascle and Chaumillon, 1998; Chamot-Rooke et al.,
2005b). These faults are often associated with fluid venting because
they represent conduits along which material deriving from the wedge
interior can be extruded to the seafloor forming argilo-kinetic structures. The lack of evaporitic impermeable cap in the inner wedge, active
faulting along the inner deformation front and transverse structures
segmenting the subduction complex all favor rising of fluids from the
wedge interior and formation of volcanic features (Chamot-Rooke et
al., 2005a). The recently discovered Pythagoras mud volcano (Praeg et
al., 2009) is located along the wedge/inner plateau tectonic contact,
confirming that this boundary represents a favorable pathway for rising
fluids.
Our observations are in accord with previous results obtained in
the inner to central Calabrian accretionary prism (Praeg et al., 2009)
and in the Mediterranean Ridge (Cita et al., 1981; Huguen et al.,
2001; Akhmanov et al., 2003) where mud breccia is composed by
fossils and clasts derived from strata as old as Cretaceous incorporated in the accretionary prism. Correlation with Expanding Spread
Profile (ESP) refraction data (de Voogd et al., 1992) and stratigraphic reconstructions in the Mediterranean Ridge (Polonia et al., 2002)
and Calabrian Arc (Polonia et al., 2011), point out that the incoming
African plate has a sediment cover as thick as 6 km in the abyssal
plain. The Cretaceous clasts found in Plio-Pleistocene sediments
within the accretionary wedge originate probably several kilometers deep (ca 10 km; Polonia et al., 2011, Figs. 2 and 3), in a region
where the basal detachment of the subduction system is located
above of the Mesozoic strata. This might suggest mud volcanoes
with deeply rooted conduits through which material of multiple
stratigraphic levels could migrate. Similar observations by Praeg et
al. (2009) call for deeply rooted sub-vertical conduits below mud
volcanoes, where the rise of overpressured fluids drives sediment
mobilization via formation of material of mud chambers beneath,
with migration of multiple stratigraphic levels dating back to the
Late Cretaceous.
The timing of fluid activity assumed here can be reconstructed
through the cronostratigraphic constraints proposed in this work.
The massive mud-breccia facies in cores BS81/II 5 and BS81/II 10
and the patchy/cloudy mud-breccia facies in CALA 21 are present
within the upper Pleistocene sediments. In accordance with Praeg et
al. (2009), extrusion of the Calabrian Arc mud volcanoes have taken
place since the late Pliocene, a period of at least 3 m.y. This may be
the longest documented record of mud extrusion from individual
6. Conclusions
- The investigated sites in the Ionian Sea reveal the existence of two
new mud volcanoes at the contact between the inner wedge and
the inner plateau of the Calabrian Arc. The formation of these
structures implies new considerations on the importance of fluid
venting in this area and, generally on the active role of the accretionary wedge tectonics in driving fluid flow.
- The massive mud breccia in cores BS81/II 5 and BS81/II 10 and the
mud breccia patchy/cloudy facies in CALA 21 are expressions of
different intensities of fluid flow. Northwest of the CA inner
deformation front (hangingwall of the Calabria Escarpment)
where cores 5 BS81/II and 10 BS81/II were collected, mud breccias mark the extrusion of deep-seated clay-rich formations
linked to tectonic stresses within the accretionary prism. In
contrast, southeast of the inner deformation front of the subduction system (footwall of the Calabria Escarpment), the mud breccia patchy/cloudy of core CALA 21 is produced by local fluid
remobilization.
- The massive mud breccia in cores 5 BS81/II and 10 BS81/II is
derived from different stratigraphic levels beneath the mud volcano. In the Plio-Pleistocene mud matrix the mud breccia includes a mixture of euhedral to rounded clasts with different
sizes and lithologies involved in intrusive cycles with rising of
old sediments (Upper Cretaceous to Late Miocene).
- The integrated investigation of CALA21 can help distinguish the
mud breccia patchy/cloudy facies from host sediments based on
the following: abrupt decrease in magnetic susceptibility with
no variations in grain size and chemical composition of sediments; authigenic minerals such as pyrite and barite; different
preservation of foraminifera; reworked nannofossils; micropipes, and anomalous isotopic data. Moreover, lower δ 18O and
higher δ 13C values might indicate alteration after cessation of
the seepage during increased burial.
Acknowledgments
We acknowledge Giovanni Bortoluzzi and Francesco Riminucci for
core sampling operations during the Urania Cruise, Giorgio Gasparotto
for SEM assistance, Leonardo Langone for CHN analyses, and Rossella
Capozzi for discussions. This manuscript was greatly improved by constructive comments from Jörn Peckmann, Alina Stadnitskaia, and the
Editor Gert de Lange. A special thanks to Ruth Martin and Enrico Bonatti
who helped to improve the manuscript. Structural mapping and seismic
data interpretation has been performed with the SEISRPO software
(Gasperini and Stanghellini, 2009). We acknowledge the CIESM/Ifremer
Medimap group (Loubrieu et al., 2008) for having provided us with the
multibeam grid of the study area. This work has been supported by
MIUR-PRIN (2006) and TOPOMED projects.
This is an ISMAR contribution n. 1762.
96
Appendix A
Table showing the total abundance, estimate of preservation and semiquantitative total abundance of nannofossils in core CALA 21.
Table 1
Reference data for the sediment cores used for this study.
Abundance of
nannofossils
Preservation of
nannofossils
Emiliana
huxleyi
Gephyrocapsa
oceanica
2
15
22
27
33
35
45
48
53
61
63.5
65
235
351
431
335
411
432
435
444
530
A
A
B
A
A
A
A
A
A
A
C
A
A
A
C
C
C
C
A
A
A
G
G
G
G
G
G
G
G
G
G
M/P
G
M
M
M
M
G
M
M/P
M
M
A
A
A
A
A
A
A
A
A
A
A
C
C
C
C
A
C
C
A
C
Florisphaera
profunda
Gladiolithus
flabellatus
Rhabdosphaera
stylifer
Helicosphaera
carteri
Syracosphaera
sp.
Syracosphaera
pulchra
Calcidiscus
leptoporus
Discosphaera
tubifera
Umbellosphaera
irregularis
Oolithotus
fragilis
Umbilicosphaera
sibogae
reworked
Tertiary
reworked
Cretaceous
C
C
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
C
C
C
C
C
C
C
C
C
R
R
R
R
C
R
R
A
R
F
F
F
F
F
R
R
F
F
F
F
F
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
F
R
C
C
C
C
F
C
F
C
R
R
R
R
R
R
R
R
F
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
F
F
F
R
F
R
C
R
A
C
A
A
R
C
C
F
F
R
R
R
R
R
F
R
F
R
A
C
C
R
R
R
R
R
R
R
R
R
R
R
R
R
F
F
F
R
R
R
R
R
R
R
R
R
For total abundance A = abundant (>50 specimens per field of view, FOV); C = common (10–50 specimens/FOV); F = few (1–10 specimens/FOV); R = rare (1 specimen/1–10 FOV); B = barren. For species abundance are as well expressed
semiquantitatively after evaluation of the abundance in 100 field of view and are coded as follows: A = abundant (more than 10 specimens/FOV); C = common (1–10 specimens/FOV); F = few (1 specimen/1–10 FOV); R = rare (1 specimen/
10–50 FOV); B = barren. Estimates of preservation is based on the degree of etching, overgrowth, and dissolution, and was coded according to the code of the Ocean Drilling program code as follows: M = moderate (specimens with some
etching or overgrowth or dissolution, primary morphological characteristics are sometime altered, but identifiable at the species level); PM = poor to moderate; P = poor (specimens with etching, overgrowth or dissolution, destroying
primary morphological characteristics that could hamper the identification at the species level).
G. Panieri et al. / Marine Geology 336 (2013) 84–98
Depth
in core
CALA21
(cm)
G. Panieri et al. / Marine Geology 336 (2013) 84–98
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